Eustace L Dereniak

Interests

No activities entered.

Courses

Scholarly Contributions

Journals/Publications

• Dereniak, E. L. (2013). Novel imaging spectrometers and polarimeters. Proceedings of SPIE - The International Society for Optical Engineering, 9066.
  More info

  Abstract: The use of two dimensional arrays has enabled the development of novel imaging spectrometers and polarimeters with snapshot capabilities, meaning the entire data cube can be recorded simultaneously. This presentation will discuss the development of spectrometer and polarimeter imagers that use new optical designs based on old ideas. The presentation contains an overview of the various types of imaging sensors that have been developed at the Optical Detection Lab of the University of Arizona. The goal of our research is to develop instruments capable of discriminating objects in biological tissue and within the human eye. Additionally, instruments of this type will be capable of spectrally monitoring simultaneously chemical or biological processes in real time in four dimensions (x,y,λ,t). © 2013 Copyright SPIE.
• Hagen, N., Oka, K., & Dereniak, E. L. (2013). Erratum: Snapshot Mueller matrix spectropolarimeter (Optics Letters ). Optics Letters, 38(10), 1675-.
• Jungwirth, M. E., Wilcox, C. C., Wick, D. V., Baker, M. S., Hobart, C. G., Milinazzo, J. J., Robichaud, J., Romeo, R. C., Martin, R. N., Ballesta, J., Lavergne, E., & Dereniak, E. L. (2013). Large-aperture active optical carbon fiber reinforced polymer mirror. Proceedings of SPIE - The International Society for Optical Engineering, 8725.
  More info

  Abstract: An active reflective component can change its focal length by physically deforming its reflecting surface. Such elements exist at small apertures, but have yet to be fully realized at larger apertures. This paper presents the design and initial results of a large-aperture active mirror constructed of a composite material called carbon fiber reinforced polymer (CFRP). The active CFRP mirror uses a novel actuation method to change radius of curvature, where actuators press against two annular rings placed on the mirror's back. This method enables the radius of curvature to increase from 2000mm to 2010mm. Closed-loop control maintains good optical performance of 1.05 waves peak-to-valley (with respect to a HeNe laser) when the active CFRP mirror is used in conjunction with a commercial deformable mirror. © 2013 SPIE.
• Kudenov, M. W., Mallik, S., Escuti, M. J., Hagen, N., Oka, K., & Dereniak, E. L. (2013). Snapshot imaging mueller matrix instrument. Proceedings of SPIE - The International Society for Optical Engineering, 8897.
  More info

  Abstract: A novel way to measure the Mueller matrix image enables a sample's diattenuation, retardance, and depolarization to be measured within a single camera integration period. Since the Mueller matrix components are modulated onto coincident carrier frequencies, the described technique provides unique solutions to image registration problems for moving objects. In this paper, a snapshot imaging Mueller matrix polarimeter is theoretically described, and preliminary results shows it to be a viable approach for use in surface characterization of moving objects. © 2013 SPIE.
• Van, J., Scrymgeour, D. A., Kemme, S. A., & Dereniak, E. L. (2013). Range and contrast imaging improvements using circularly polarized light in scattering environments. Proceedings of SPIE - The International Society for Optical Engineering, 8706.
  More info

  Abstract: We find for infrared wavelengths there are clear particle size ranges and indices representative of fog and rain where the use of circular polarization imaging can penetrate to larger optical depths than linear polarization. Using polarization tracking Monte Carlo simulations for varying particle size, wavelength, and index systematically, we show that for specific scene parameters circular polarization vastly outperforms linear polarization in maintaining degree of polarization for large optical depths in transmission and reflection. This enhancement in circular polarization can be exploited to improve imaging in obscurant environments that are important in many critical imaging applications. Specifically, circular polarization performs better than linear for radiation fog in the SWIR and MWIR regime, advection fog in the LWIR regime, and small sized particles of Sahara dust in the MWIR regime. © 2013 SPIE.
• Craven-Jones, J., Kudenov, M. W., & Dereniak, E. L. (2012). Tunable interference contrast using a variable Wollaston prism. Optical Engineering, 51(1).
  More info

  Abstract: A Fourier transform spectrometer (FTS) acquires interferogram data for spectral measurements. Conventional FTS instruments incorporate Michelson interferometers. However, limitations of the Michelson for imaging applications have produced interest in alternative interferometer configurations. Common path interferometers, such as birefringent interferometers, offer advantages for remote sensing applications. To ensure the best possible signal-to-noise ratio, the fringe contrast provided by the interferometer should be maximized. Unfortunately some birefringent interferometers, such as those that utilize Wollaston prisms (WPs), require stringent tolerances in order to ensure high fringe contrast across even a modest field of view (FOV). Fabricating an interferometer to meet these tolerances adds fabrication cost and time to the development of an instrument. We present how the introduction of additional birefringent elements into birefringent interferometer can be used to compensate for a decrease in fringe visibility due to manufacturing errors. These components form a variable angle WP (VWP), which can be used to vary the fringe visibility across the FOV. Experimental results confirming the ability of the VWP to vary the fringe visibility of a birefringent interferometer are included. These results are compared to polarization raytrace simulations for the system. © 2012 Society of Photo-Optical Instrumentation Engineers (SPIE).
• Dereniak, E. L. (2012). Mentored by Mr. Infrared. Proceedings of SPIE - The International Society for Optical Engineering, 8483.
  More info

  Abstract: Professor Wolfe has been my mentor and friend since 1965, even before I became one of his PhD students. In fact, the development of my career in infrared technology was closely linked to Bill's work, and would not have been possible without him and his guidance. © 2012 SPIE.
• Dereniak, E., Kudenov, M. W., & Dereniak, E. L. (2012). Compact real-time birefringent imaging spectrometer. Optics express, 20(16).
  More info

  The design and experimental demonstration of a snapshot hyperspectral imaging Fourier transform (SHIFT) spectrometer is presented. The sensor, which is based on a multiple-image FTS (MFTS), offers significant advantages over previous implementations using Michelson interferometers. Specifically, its use of birefringent interferometry creates a vibration insensitive and ultra-compact (15x15x10 mm(3)) common-path interferometer while offering rapid reconstruction rates through the graphics processing unit. The SHIFT spectrometer's theory and experimental prototype are described in detail. Included are reconstruction and spectral calibration procedures, followed by the spectrometer's validation using measurements of gas-discharge lamps. Lastly, outdoor measurements demonstrate the sensor's ability to resolve spectral signatures in typical outdoor lighting and environmental conditions.
• Dereniak, E., Miller, D. A., & Dereniak, E. L. (2012). Selective polarization imager for contrast enhancements in remote scattering media. Applied optics, 51(18).
  More info

  Conventional intensity imaging through turbid media suffers from rapid loss of image contrast due to light scattering from particles or random variations of refractive index. This paper features the development of an active imaging, snapshot, system design and postprocessing algorithms that differentiate between radiation that scatters or reflects from remote, obscured objects and the radiation from the scattering media itself through a combination of polarization difference imaging, channel blurring, and Fourier spatial filtering. The produced sensor acquires and processes image data in real time, yielding improved image contrasts by factors of 10 or greater for dense water vapor obscurants.
• E., M., Wick, D. V., & Dereniak, E. L. (2012). Theory and tradespace analysis of a reflective axial adaptive optical zoom system. Optical Engineering, 51(8).
  More info

  Abstract: Optical zoom enables wide and narrow fields-of-view within a single optical system. Traditional zoom designs translate elements along the optical axis, a technique that is generally prohibitive for large diameter optics. Adaptive optical zoom (AOZ) alters system magnification via variable focal length elements, a technique that has the potential to facilitate zoom in large diameter systems. This paper details a novel optical theory developed to design AOZ systems. The developed theory modifies existing techniques for telescope objective design and third-order aberration determination to accommodate the additional degrees of freedom found with AOZ. The derived theory also enables a large-scale tradespace analysis, allowing optical design to begin from a broad perspective and optimize a particular design. Using the tradespace analysis, a Cassegrain AOZ objective with a 3.3Xzoom ratio is designed, demonstrating the capability and validity of the theory. © 2012 Society of Photo-Optical Instrumentation Engineers (SPIE).
• E., M., Wick, D. V., Baker, M. S., Wilcox, C. C., Dereniak, E. L., Romeo, R. C., & Martin, R. N. (2012). Actuation for carbon fiber reinforced polymer active optical mirrors. IEEE Aerospace Conference Proceedings.
  More info

  Abstract: Adaptive or active elements can alter their shape to remove aberrations or shift focal points. Carbon fiber reinforced polymer (CFRP) material improves upon current active mirror materials, such as Zerodur, in several ways: low stiffness-to-weight ratio, very low hysteresis, and greater dynamic range of correction. In this paper, we present recent developments in CFRP mirror actuation, i.e., changing the mirror's shape in an accurate and repeatable fashion. Actuation methods are studied both theoretically, using finite element analysis, and experimentally, using interferometric testing. We present results using two annular rings to push against the mirror's back, producing a wavefront with less than 20 waves of total error. Applications for this work include active telescope secondaries, phase diversity, and adaptive zoom systems. © 2012 IEEE.
• Jungwirth, M. E., Wick, D. V., & Dereniak, E. L. (2012). Theory and design of a MEMS-enabled diffraction limited adaptive optical zoom system. Proceedings of SPIE - The International Society for Optical Engineering, 8373.
  More info

  Abstract: Micro-electro-mechanical systems (MEMS) deformable mirrors are known for their ability to correct optical aberrations, particularly when the wavefront is expanded via Zernike polynomials. This capability is combined with adaptive optical zoom to enable diffraction limited performance over broad spectral and zoom ranges. Adaptive optical zoom (AOZ) alters system magnification via variable focal length elements instead of axial translation found in traditional zoom designs. AOZ systems are simulated using an efficient approach to optical design, in which existing theories for telescope objective design and third-order aberration determination are modified to accommodate the additional degrees of freedom found with AOZ. An AOZ system with a 2.7x zoom ratio and 100mm entrance pupil diameter is presented to demonstrate the validity and capability of the theory. © 2012 SPIE.
• Kudenov, M. W., & Dereniak, E. L. (2012). Compact real-time birefringent imaging spectrometer. Optics Express, 20(16), 17973-17986.
  More info

  PMID: 23038346;Abstract: The design and experimental demonstration of a snapshot hyperspectral imaging Fourier transform (SHIFT) spectrometer is presented. The sensor, which is based on a multiple-image FTS (MFTS), offers significant advantages over previous implementations using Michelson interferometers. Specifically, its use of birefringent interferometry creates a vibration insensitive and ultra-compact (15x15x10 mm3) common-path interferometer while offering rapid reconstruction rates through the graphics processing unit. The SHIFT spectrometer's theory and experimental prototype are described in detail. Included are reconstruction and spectral calibration procedures, followed by the spectrometer's validation using measurements of gas-discharge lamps. Lastly, outdoor measurements demonstrate the sensor's ability to resolve spectral signatures in typical outdoor lighting and environmental conditions. © 2012 Optical Society of America.
• Kudenov, M. W., Banerjee, B., Chan, V. C., & Dereniak, E. L. (2012). Compact snapshot birefringent imaging Fourier transform spectrometer for remote sensing and endoscopy. Proceedings of SPIE - The International Society for Optical Engineering, 8542.
  More info

  Abstract: The design and implementation of a compact multiple-image Fourier transform spectrometer (FTS) is presented. Based on the multiple-image FTS originally developed by A. Hirai, the presented device offers significant advantages over his original implementation. Namely, its birefringent nature results in a common-path interferometer which makes the spectrometer insensitive to vibration. Furthermore, it enables the potential of making the instrument ultra-compact, thereby improving the portability of the sensor. The theory of the birefringent FTS is provided, followed by details of its specific embodiment. A laboratory proof of concept of the sensor, designed and developed at the Optical Detection Lab, is also presented. Spectral measurements of laboratory sources are provided, including measurements of light-emitting diodes and gas-discharge lamps. These spectra are verified against a calibrated Ocean Optics USB2000 spectrometer. Other data were collected outdoors and of a rat esophagus, demonstrating the sensor's ability to resolve spectral signatures in both standard outdoor lighting and environmental conditions, as well as in fluorescence spectroscopy. © 2012 SPIE.
• Kudenov, M. W., Craven-Jones, J., Aumiller, R., Vandervlugt, C., & Dereniak, E. L. (2012). Faceted grating prism for a computed tomographic imaging spectrometer. Optical Engineering, 51(4).
  More info

  Abstract: A computed tomographic imaging spectrometer (CTIS) disperses the three-dimensional (3-D) datacube (x, y, λ) into two-dimensional (2-D) projections on a focal plane array (FPA). The 3-D datacube is subsequently reconstructed from these 2-D projections using iterative computed tomography algorithms. Conventional designs achieve the 3-D to 2-D mapping by incorporating an optimized disperser. However, these dispersers suffer from the linearity constraint inherent in the first-order grating equation. This constraint means that many of the FPA's pixels are either unilluminated or they are used to image redundant projections; in both cases, they can not be used to increase the datacube's spectral resolution. Here, we outline various hardware improvements that increase the CTIS's spectral resolution by making use of these previously unilluminated or redundant pixels. Specifically, we incorporated a new disperser based on a 2-D grating prism and a division of aperture approach. Included is an optical design analysis of the system, in addition to an experimental characterization of the instrument's performance. Lastly, the new disperser is compared to a conventional disperser to quantify the increased spectral resolution. © 2012 Society of Photo-Optical Instrumentation Engineers (SPIE).
• Kudenov, M. W., Escuti, M. J., Hagen, N., Dereniak, E. L., & Oka, K. (2012). Snapshot imaging Mueller matrix polarimeter using polarization gratings. Optics Letters, 37(8), 1367-1369.
  More info

  PMID: 22513688;Abstract: A snapshot imaging Mueller matrix polarimeter (SIMMP) is theoretically described and empirically demonstrated through simulation. Spatial polarization fringes are localized onto a sample by incorporating polarization gratings (PGs) into a polarization generator module. These fringes modulate the Mueller matrix (MM) components of the sample, which are subsequently isolated with PGs in an analyzer module. The MM components are amplitude modulated onto spatial carrier frequencies which, due to the PGs, maintain high visibility in spectrally broadband illumination. An interference model of the SIMMP is provided, followed by methods of reconstruction and calibration. Lastly, a numerical simulation is used to demonstrate the system's performance in the presence of noise. © 2012 Optical Society of America.
• Kudenov, M. W., Miskiewicz, M. N., Escuti, M. J., & Dereniak, E. L. (2012). Spatial heterodyne interferometry with polarization gratings. Optics Letters, 37(21), 4413-4415.
  More info

  PMID: 23114313;Abstract: The implementation of a polarization-based spatial heterodyne interferometer (SHI) is described. While a conventional SHI uses a Michelson interferometer and diffraction gratings, our SHI exploits mechanically robust Wollaston prisms and polarization gratings. A theoretical model for the polarization SHI is provided and validated with data from our proof of concept experiments. This device is expected to provide a compact monolithic sensor for subangstrom resolution spectroscopy in remote sensing, biomedical imaging, and machine vision applications. © 2012 Optical Society of America.
• Miller, D. A., & Dereniak, E. L. (2012). Selective polarization imager for contrast enhancements in remote scattering media. Applied Optics, 51(18), 4092-4102.
  More info

  PMID: 22722285;Abstract: Conventional intensity imaging through turbid media suffers from rapid loss of image contrast due to light scattering from particles or random variations of refractive index. This paper features the development of an active imaging, snapshot, system design and postprocessing algorithms that differentiate between radiation that scatters or reflects from remote, obscured objects and the radiation from the scattering media itself through a combination of polarization difference imaging, channel blurring, and Fourier spatial filtering. The produced sensor acquires and processes image data in real time, yielding improved image contrasts by factors of 10 or greater for dense water vapor obscurants. © 2012 Optical Society of America.
• Miller, D. A., Wilson, D. W., & Dereniak, E. L. (2012). Novel design and alignment of wire-grid diffraction gratings on a visible focal plane array. Optical Engineering, 51(1).
  More info

  Abstract: A pixelated, wire-grid diffraction grating is designed, fabricated, aligned, and mounted on an active focal plane array of a camera operating in the visible. The resulting design of the pixelated wire-grid polarizer array eschewed the need for fine translational alignments and drastically reduced cross-talk between pixels detecting differing polarization states. Using common optomechanical elements in conjunction with a novel correlation-based alignment metric, we are able to achieve repeatable angular alignments to better than 0.004deg between the focal plane array and the pixelated wire-grid polarizer array, both featuring 6.45m pixels. An on-chip, four-state, linear snapshot polarimeter is yielded in the detailed processes and raw image data from the instrument are presented. © 2012 Society of Photo-Optical Instrumentation Engineers.
• Craven-Jones, J., Kudenov, M. W., Stapelbroek, M. G., & Dereniak, E. L. (2011). Infrared hyperspectral imaging polarimeter using birefringent prisms. Applied Optics, 50(8), 1170-1185.
  More info

  PMID: 21394189;Abstract: A compact short-wavelength and middle-wavelength infrared hyperspectral imaging polarimeter (IHIP) is introduced. The sensor includes a pair of sapphire Wollaston prisms and several high-order retarders to form an imaging Fourier transform spectropolarimeter. The Wollaston prisms serve as a birefringent interferometer with reduced sensitivity to vibration versus an unequal path interferometer, such as a Michelson. Polarimetric data are acquired through the use of channeled spectropolarimetry to modulate the spectrum with the Stokes parameter information. The collected interferogram is Fourier filtered and reconstructed to recover the spatially and spectrally varying Stokes vector data across the image. The IHIP operates over a ±5° field of view and implements a dual-scan false signature reduction technique to suppress polarimetric aliasing artifacts. In this paper, the optical layout and operation of the IHIP sensor are presented in addition to the radiometric, spectral, and polarimetric calibration techniques used with the system. Spectral and spectropolarimetric results from the laboratory and outdoor tests with the instrument are also presented. © 2011 Optical Society of America.
• Craven-Jones, J., Kudenov, M. W., Stapelbroek, M. G., & Dereniak, E. L. (2011). Preliminary results from an infrared hyperspectral imaging polarimeter. Proceedings of SPIE - The International Society for Optical Engineering, 8160.
  More info

  Abstract: We present results from a SWIR/MWIR infrared hyperspectral imaging polarimeter (IHIP). The sensor includes a pair of sapphire Wollaston prisms and several high order retarders to form an imaging Fourier transform spectropolarimeter. The Wollaston prisms serve as a birefringent interferometer with reduced sensitivity to vibration versus an unequal path interferometer, such as a Michelson. Polarimetric data are acquired through the use of channeled spectropolarimetry to modulate the spectrum with the Stokes parameter information. We discuss the operation of the IHIP sensor, in addition to our calibration techniques. Lastly, spectropolarimetric results from the laboratory and outdoor tests are presented. © 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).
• Dereniak, E., Craven-Jones, J., Kudenov, M. W., Stapelbroek, M. G., & Dereniak, E. L. (2011). Infrared hyperspectral imaging polarimeter using birefringent prisms. Applied optics, 50(8).
  More info

  A compact short-wavelength and middle-wavelength infrared hyperspectral imaging polarimeter (IHIP) is introduced. The sensor includes a pair of sapphire Wollaston prisms and several high-order retarders to form an imaging Fourier transform spectropolarimeter. The Wollaston prisms serve as a birefringent interferometer with reduced sensitivity to vibration versus an unequal path interferometer, such as a Michelson. Polarimetric data are acquired through the use of channeled spectropolarimetry to modulate the spectrum with the Stokes parameter information. The collected interferogram is Fourier filtered and reconstructed to recover the spatially and spectrally varying Stokes vector data across the image. The IHIP operates over a ±5° field of view and implements a dual-scan false signature reduction technique to suppress polarimetric aliasing artifacts. In this paper, the optical layout and operation of the IHIP sensor are presented in addition to the radiometric, spectral, and polarimetric calibration techniques used with the system. Spectral and spectropolarimetric results from the laboratory and outdoor tests with the instrument are also presented.
• Kudenov, M. W., & Dereniak, E. L. (2011). Compact Snapshot real-time imaging spectrometer. Proceedings of SPIE - The International Society for Optical Engineering, 8186.
  More info

  Abstract: The described spectral imaging system, referred to as a Snapshot Hyperspectral Imaging Fourier Transform (SHIFT) spectrometer, is capable of acquiring spectral image data of a scene in a single integration of a camera, is ultra-compact, inexpensive (commercial off-the-shelf), has no moving parts, and can produce datacubes (x, y, λ) in real time. Based on the multiple-image FTS originally developed by A. Hirai [1], the presented device offers significant advantages over his original implementation. Namely, its birefringent nature results in a common-path interferometer which makes the spectrometer insensitive to vibration. Furthermore, it enables the potential of making the instrument ultra-compact, thereby improving the portability of the sensor. By combining a birefringent interferometer with a lenslet array, the entire spectrometer consumes approximately 15×15×20 mm3, excluding the imaging camera. The theory of the birefringent FTS is provided, followed by details of its specific embodiment and a laboratory proof of concept of the sensor. Post-processing is currently accomplished in Matlab, but progress is underway in developing real-time reconstruction capabilities with software programmed on a graphics processing unit (GPU). It is anticipated that processing of >30 datacubes per second can be achieved with modest GPU hardware, with spatial/spectral data of or exceeding 256×256 spatial resolution elements and 60 spectral bands over the visible (400-800 nm) spectrum. Data were collected outdoors, demonstrating the sensor's ability to resolve spectral signatures in standard outdoor lighting and environmental conditions as well as retinal imaging. © 2011 SPIE.
• Kudenov, M. W., & Dereniak, E. L. (2011). Imaging spectrometers and polarimeters. Optics InfoBase Conference Papers.
  More info

  Abstract: Imaging spectrometer and polarimeter research at the Optical Detection Lab, University of Arizona, is overviewed. Topics include snapshot imaging spectroscopy, white-light channeled imaging polarimetry, and infrared hyperspectral imaging polarimetry. © 2011 OSA.
• Kudenov, M. W., Escuti, M. J., Dereniak, E. L., & Oka, K. (2011). Spectrally broadband channeled imaging polarimeter using polarization gratings. Proceedings of SPIE - The International Society for Optical Engineering, 8160.
  More info

  Abstract: A snapshot channeled linear imaging (CLI) polarimeter is demonstrated by incorporating two identical polarization gratings (PGs) into a shearing polarization interferometer. Placing the PGs in series causes the shear to become linearly proportional to the wavelength, thereby generating white-light polarization fringes at the focal point of an imaging lens. These fringes amplitude modulate the incident Stokes parameters corresponding to linearly polarized light (S0, S1, and S2). In this paper, we theoretically and experimentally demonstrate the CLI polarimeter. Additional validation of the technique is conducted through outdoor measurements of moving targets, and extending the measurement capacity of the system to include circularly polarized light is theoretically demonstrated. © 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).
• Kudenov, M. W., Escuti, M. J., Dereniak, E. L., & Oka, K. (2011). White-light channeled imaging polarimeter using broadband polarization gratings. Applied Optics, 50(15), 2283-2293.
  More info

  PMID: 21614123;Abstract: A white-light snapshot channeled linear imaging (CLI) polarimeter is demonstrated by utilizing polarization gratings (PGs). The CLI polarimeter is capable of measuring the two-dimensional distribution of the linear Stokes polarization parameters by incorporating two identical PGs, in series, along the optical axis. In this configuration, the general optical shearing functionality of a uniaxial crystal-based Savart plate is realized. However, unlike a Savart plate, the diffractive nature of the PGs creates a linear dependence of the shear versus wavelength, thus providing broadband functionality. Consequently, by incorporating the PG-based Savart plate into a Savart plate channeled imaging polarimeter, white-light interference fringes can be generated. This enables polarimetric image data to be acquired at shorter exposure times in daylight conditions, making it more appealing over the quasi-monochromatic channeled imaging polarimeters previously described in the literature. Furthermore, the PG-based device offers significantly more compactness, field of view, optical simplicity, and vibration insensitivity than previously described white-light CLI polarimeters based on Sagnac interferometers. Included in this paper are theoretical descriptions of the linear (S0, S1, and S 2) and complete (S0, S1, S2, and S3) channeled Stokes imaging polarimeters. Additionally, descriptions of our calibration procedures and our experimental proof of concept CLI system are provided. These are followed by laboratory and outdoor polarimetric measurements of S0, S1, and S2. © 2011 Optical Society of America.
• Craven, J., Kudenov, M. W., Stapelbroek, M. G., & Dereniak, E. L. (2010). Compact infrared hyperspectral imaging polarimeter. Proceedings of SPIE - The International Society for Optical Engineering, 7695.
  More info

  Abstract: A compact SWIR/MWIR infrared hyperspectral imaging polarimeter (IHIP) is currently under development at the Optical Detection Lab at the University of Arizona. The sensor uses a pair of sapphire Wollaston prisms and high order retarders to form an imaging birefringent Fourier transform spectropolarimeter. Polarimetric data are acquired through the use of channeled spectropolarimetry to modulate the spectrum with the Stokes parameter information. The two dimensional interferogram is Fourier filtered and reconstructed to recover the complete Stokes vector data across the image. The IHIP operates over a +/-5° field of view and will use a dual-scan false signature reduction technique to suppress polarimetric aliasing artifacts. We present current instrument development progress, initial laboratory results, and our plan for future work. © 2010 SPIE.
• Kudenov, M. W., & Dereniak, E. L. (2010). Compact snapshot birefringent imaging Fourier transform spectrometer. Proceedings of SPIE - The International Society for Optical Engineering, 7812.
  More info

  Abstract: The design and implementation of a compact multiple-image Fourier transform spectrometer (FTS) is presented. Based on the multiple-image FTS originally developed by A. Hirai, the presented device offers significant advantages over his original implementation. Namely, its birefringent nature results in a common-path interferometer which makes the spectrometer insensitive to vibration. Furthermore, it enables the potential of making the instrument ultra-compact, thereby improving the portability of the sensor. The theory of the birefringent FTS is provided, followed by details of its specific embodiment. A laboratory proof of concept of the sensor, designed and developed at the Optical Detection Lab, is also presented. Spectral measurements of laboratory sources are provided, including measurements of light-emitting diodes and gas-discharge lamps. These spectra are verified against a calibrated Ocean Optics USB2000 spectrometer. Other data were collected outdoors, demonstrating the sensor's ability to resolve spectral signatures in standard outdoor lighting and environmental conditions. © 2010 SPIE.
• Kudenov, M. W., E., M., Dereniak, E. L., & Gerhart, G. R. (2010). White-light Sagnac interferometer for snapshot multispectral imaging. Applied Optics, 49(21), 4067-4076.
  More info

  PMID: 20648191;Abstract: The theoretical and experimental demonstration of a multispectral Sagnac interferometer (MSI) is presented. The MSI was created by including two multiple-order blazed diffraction gratings in both arms of a standard polarization Sagnac interferometer (PSI). By introducing these high-order diffractive structures, unique spectral passbands can be amplitude modulated onto coincident carrier frequencies. Extraction of the modulated multispectral images, corresponding to each passband, is accomplished within the Fourier domain. This yields a unique multispectral sensor capable of imaging all the passbands in a single snapshot. First, the theoretical operating principles of a PSI are discussed to provide a context for the MSI. This is followed by the theoretical and experimental development of the MSI, which is an extension of a dispersion-compensated PSI. Indoor and outdoor testing and validation of the MSI are performed by observing vegetation, demonstrating the ability of our experimental setup to detect four distinct spectral passbands. © 2010 Optical Society of America.
• Kudenov, M. W., E., M., Dereniak, E. L., & Gerhart, G. R. (2010). White-light Sagnac interferometer for snapshot polarimetric and multispectral imaging. Proceedings of SPIE - The International Society for Optical Engineering, 7672.
  More info

  Abstract: A common technique, referred to as channeled imaging polarimetry (CIP), enables the snapshot acquisition of the 2-dimensional Stokes parameters of an arbitrary scene or sample. It achieves this by amplitude modulating the Stokes parameters onto various interference-based spatial carrier frequencies. While this technique has utility, it often suffers from low signal-to-noise ratios in remote sensing scenarios, since it requires narrow spectral bandwidth illumination (< 3 nm in the visible). This paper discusses one hardware implementation that can be utilized to overcome this limitation. Consequently, an overview of the theoretical and experimental development of this system, a uniquely modified Sagnac interferometer, is discussed. Both laboratory and outdoor data are included to demonstrate the instrument's ability to measure polarization in arbitrary scenes. Inclusion of blazed diffraction gratings inside the interferometer enables whitelight interference fringes to be generated. By incorporating these gratings, the operational bandwidth of the interference fringes can exceed approximately 300 nm within the visible spectrum; two orders of magnitude greater than previous CIP implementations. Lastly, by modifying the diffraction grating, the sensor becomes capable of snapshot multispectral imaging. This is briefly discussed, with both a theoretical description and experimental data. © 2010 SPIE.
• Scholl, J. F., Hege, E. K., & Dereniak, E. L. (2010). The design of wavelets for limited-angle tomographic hyperspectral imaging systems. Proceedings of SPIE - The International Society for Optical Engineering, 7799.
  More info

  Abstract: A number of hyperspectral (x, y, λ) imaging systems work on the principle of limited angle tomography. In such systems there exists a region of spatial and spectral frequencies called the "missing cone" that the imaging system cannot recover from data using any direct reconstruction algorithms. Wavelets are useful for imaging objects that are spatially and in many cases also spectrally compact. However wavelet expansion functions have three-dimensional frequency content intersecting the missing cone region; this means the wavelets themselves are altered thus compromising the corresponding datacube reconstructions. As the missing cone of frequencies is fixed for a given imaging system, it is reasonable to adjust parameters in the wavelets themselves in order to reduce the intersection between the wavelets' frequency content and the missing cone. One wavelet system is better than another when the frequency content of the former has a smaller amount of overlap with the missing cone. We will do this analysis with a couple of classic wavelet families, the Morlet and the Difference of Gaussian (DOG) for an existing hyperspectral tomographic imaging system to show the feasibility of this procedure. © 2010 Copyright SPIE - The International Society for Optical Engineering.
• Craven, J. M., Kudenov, M. W., & Dereniak, E. L. (2009). False signature reduction in infrared channeled spectropolarimetry. Proceedings of SPIE - The International Society for Optical Engineering, 7419.
  More info

  Abstract: Channeled spectropolarimetry, first developed by K. Oka, is capable of measuring all the Stokes parameters from a single modulated spectrum. We present a theoretical means for improving the spectral resolution of channeled spectropolarimetry by at least a factor of four. Especially valuable in the infrared due to atmospheric absorption features, this method simultaneously provides for the correction of aliasing artifacts from the channels used for the determination of the Stokes parameters. The technique is experimentally demonstrated using a Fourier transform infrared spectrometer and two multiple-order Yttrium Vanadate (YVO 4) retarders. This approach is implemented with consideration of crystal dichroism effects, and reconstructions are compared with conventional channeled spectropolarimetric reconstructions from the same system. Additional results, produced by using Cadmium Sulfide (CdS) retarders, provide demonstration of the technique across the infrared. © 2009 SPIE.
• DeHoog, E., Luo, H., Oka, K., Dereniak, E., & Schwiegerling, J. (2009). Snapshot polarimeter fundus camera. Applied Optics, 48(9), 1663-1667.
  More info

  PMID: 19305463;PMCID: PMC2853936;Abstract: A snapshot imaging polarimeter utilizing Savart plates is integrated into a fundus camera for retinal imaging. Acquired retinal images can be processed to reconstruct Stokes vector images, giving insight into the polarization properties of the retina. Results for images from a normal healthy retina and retinas with pathology are examined and compared. © 2009 Optical Society of America.
• Kudenov, M. W., E., M., Dereniak, E. L., & Gerhart, G. R. (2009). White light Sagnac interferometer for snapshot linear polarimetric imaging. Optics Express, 17(25), 22520-22534.
  More info

  PMID: 20052177;Abstract: The theoretical and experimental demonstration of a dispersioncompensated polarization Sagnac interferometer (DCPSI) is presented. An application of the system is demonstrated by substituting the uniaxial crystal-based Savart plate (SP) in K. Oka's original snapshot polarimeter implementation with a DCPSI. The DCPSI enables the generation of an achromatic fringe field in white-light, yielding significantly more radiative throughput than the original quasi-monochromatic SP polarimeter. Additionally, this interferometric approach offers an alternative to the crystal SP, enabling the use of standard reflective or transmissive materials. Advantages are anticipated to be greatest in the thermal infrared, where uniaxial crystals are rare and the at-sensor radiance is often low when compared to the visible spectrum. First, the theoretical operating principles of the Savart plate polarimeter and a standard polarization Sagnac interferometer polarimeter are provided. This is followed by the theoretical and experimental development of the DCPSI, created through the use of two blazed diffraction gratings. Outdoor testing of the DCPSI is also performed, demonstrating the ability to detect either the S2 and S3, or the S1 and S2 Stokes parameters in white-light. © 2009 Optical Society of America.
• Kudenov, M. W., Pezzaniti, J. L., Dereniak, E. L., & Gerhart, G. R. (2009). Infrared Stokes imaging polarimeter using microbolometers. Proceedings of SPIE - The International Society for Optical Engineering, 7419.
  More info

  Abstract: A long wave infrared (LWIR) division of amplitude imaging Stokes polarimeter is presented. For the first time, to our knowledge, application of microbolometer focal plane array (FPA) technology to polarimetry is demonstrated. The sensor utilizes a wire-grid beamsplitter with imaging systems positioned at each output to analyze two orthogonal linear polarization states simultaneously. Combined with a form birefringent wave plate, the system is capable of snapshot imaging polarimetry in any one Stokes parameter (S 1, S2 or S3). Radiometric and polarimetric calibration procedures for the instrument are provided and data from the instrument are presented, demonstrating the ability to measure intensity variations corresponding to polarized emission in natural environments. As such, emission polarimetry can be exploited at significantly reduced cost, sensor size and power consumption over instruments based on more costly Mercury-Cadmium Telluride (MCT) FPA's. © 2009 SPIE.
• Oka, K., Suda, R., Ohnuki, M., Miller, D., & Dereniak, E. L. (2009). Snapshot imaging polarimeter for polychromatic light using Savart plates and diffractive lenses. Optics InfoBase Conference Papers.
  More info

  Abstract: The imaging polarimeter using the Savart plates is modified for use with the polychromatic light by incorporating an imaging system utilizing diffractive lenses. Its feasibility is numerical simulated for the visible light with 50 nm-bandwidth. © 2009 Optical Society of America.
• Aumiller, R. W., Vandervlugt, C., Dereniak, E. L., Sampson, R., & McMillan, R. W. (2008). Snapshot imaging spectropolarimetry in the visible and infrared. Proceedings of SPIE - The International Society for Optical Engineering, 6972.
  More info

  Abstract: Two imaging systems have been designed and built to function as snapshot imaging spectropolarimeters; one system made to operate in the visible part of the spectrum, the other for the long wavelength infrared, 8 to 12 microns. The devices are based on computed tomographic imaging channeled spectropolarimetry (CTICS), a unique technology that allows both the spectra and the polarization state for all of the wavelength bands in the spectra to be simultaneously recorded from every spatial position in an image with a single integration period of the imaging system. The devices contain no moving parts and require no scanning, allowing them to acquire data without the artifacts normally associated with scanning spectropolarimeters. Details of the two imaging systems will be presented.
• Dereniak, E. L., Hartke, J. P., & LeVan, P. D. (2008). Presentation summaries: Conference on infrared detectors and focal plane arrays IX. Proceedings of SPIE - The International Society for Optical Engineering, 7055, ix-xii.
• Dereniak, E., Luo, H., Oka, K., DeHoog, E., Kudenov, M., Schiewgerling, J., & Dereniak, E. L. (2008). Compact and miniature snapshot imaging polarimeter. Applied optics, 47(24).
  More info

  We present and demonstrate a compact and miniature snapshot imaging polarimeter camera; it is anticipated that such a camera can be scaled down to less than 1.5 cm. Two Savart plates are used at the pupil plane to generate multiple fringes to encode the full Stokes vector in a single image. A geometric ray model is developed to explain the system. The numerical simulation based on this model is presented. Finally, the validity of the device is demonstrated by showing experimental results.
• Hagen, N., & Dereniak, E. L. (2008). Analysis of computed tomographic imaging spectrometers. I. Spatial and spectral resolution. Applied Optics, 47(28), F85-F95.
  More info

  PMID: 18830288;Abstract: Computed tomographic imaging spectrometers measure the spectrally resolved image of an object scene in an entirely different manner from traditional whisk-broom or push-broom systems, and thus their noise behavior and data artifacts are unfamiliar. We review computed tomographic imaging spectrometry (CTIS) measurement systems and analyze their performance, with the aim of providing a vocabulary for discussing resolution in CTIS instruments, by illustrating the artifacts present in their reconstructed data and contributing a rule-of-thumb measure of their spectral resolution. We also show how the data reconstruction speed can be improved, at no cost in reconstruction quality, by ignoring redundant projections within the measured raw images. © 2008 Optical Society of America.
• Hagen, N., & Dereniak, E. L. (2008). Gaussian profile estimation in two dimensions. Applied Optics, 47(36), 6842-6851.
  More info

  PMID: 19104535;Abstract: We extend recent results for estimating the parameters of a one-dimensional Gaussian profile to twodimensional profiles, deriving the exact covariance matrix of the estimated parameters. While the exact form is easy to compute, we provide a set of close approximations that allow the covariance to take on a simple analytic form. This not only provides new insight into the behavior of the estimation parameters, but also lays a foundation for clarifying previously published work. We also show how to calculate the parameter variances for the case of truncated sampling, where the profile lies near the edge of the array detector. Finally, we calculate expressions for the bias in the classical formulation of the problem and provide an approach for its removal. This allows us to show how the bias affects the problem of choosing an optimal pixel size for minimizing parameter variances. © 2008 Optical Society of America.
• Hartke, J., Hagan, N., Kinder, B. A., & Dereniak, E. L. (2008). Computed Tomographic Imaging Spectrometer (CTIS) and a snapshot hyperspectral imager and polarimeter. International Journal of High Speed Electronics and Systems, 18(3), 505-517.
  More info

  Abstract: A Computed Tomographic Imagining Spectrometer (CTIS) is an imaging spectrometer system that acquires all the information required to reconstruct the data cube in a single integration time. This is compared to conventional systems such as whiskbroom systems, pushbroom systems, and filter wheel systems that requiring scanning in one or more coordinate direction. CTIS systems have been designed and tested in several different singular spectral bands as well as a dual band system. In addition to hyperspectral imaging spectrometers, CTIS systems have been used as an imaging spectropolarimeter and as a ranging imaging spectrometer. An imaging spectropolarimeter not only reconstructs the spectral content at every point in the scene of interest, but also provides the Stokes parameters at every point. So instead of just one data cube, we get four data cubes, one for each element of the Stokes vector. The ranging CTIS incorporates a LADAR system with the CTIS to provide the range information to targets in scene as well as the reconstructed data cube. The physical principles behind the CTIS system are presented as well as some of representative data from single band systems, the dual band proof of concept, the spectropolarimeter, and the ranging imaging spectrometer. © 2008 World Scientific Publishing Company.
• Kudenov, M. W., Dereniak, E. L., Pezzaniti, L., & Gerhart, G. R. (2008). 2-Cam LWIR imaging Stokes polarimeter. Proceedings of SPIE - The International Society for Optical Engineering, 6972.
  More info

  Abstract: A 2-Cam micro-bolometer imaging polarimeter operating in the LWIR is presented. The system is capable of snapshot imaging Stokes polarimetry in any one channel (S1, S2, or S3) by taking two simultaneous measurements of a scene. For measurements of S1 or S2, the instrument relies on a specially optimized wire-grid beam-splitter. For measurements of S3, a form birefringent quarter-wave retarder is inserted into the optical path. Specifics associated with the design of the wire-grid beam-splitter and the form birefringent quarter-wave retarder will be overviewed, with inclusion of RCWA simulations. Calibration and simulation procedures, as well as calibration targets, will be highlighted, and initial data from the instrument are presented.
• Kudenov, M. W., Pezzaniti, L., Dereniak, E. L., & Gerhart, G. R. (2008). Prismatic imaging polarimeter calibration for the infrared spectral region. Optics Express, 16(18), 13720-13737.
  More info

  PMID: 18772984;Abstract: The calibration of a complete Stokes birefringent prismatic imaging polarimeter (BPIP) in the MWIR is demonstrated. The BPIP technique, originally developed by K. Oka, is implemented with a set of four Yttrium Vanadate (YVO4) crystal prisms. A mathematical model for the polarimeter is presented in which diattenuation due to Fresnel effects and dichroism in the crystal are included. An improved polarimetric calibration technique is introduced to remove the diattenuation effects, along with the relative radiometric calibration required for the BPIP operating with a thermal background and large detector offsets. Data demonstrating emission polarization are presented from various blackbodies, which are compared to data from our Fourier transform infrared spectropolarimeter. © 2008 Optical Society of America.
• Luo, H., Oka, K., Dehoog, E., Kudenov, M., Schiewgerling, J., & Dereniak, E. L. (2008). Compact and miniature snapshot imaging polarimeter. Applied Optics, 47(24), 4413-4417.
  More info

  PMID: 18716648;Abstract: We present and demonstrate a compact and miniature snapshot imaging polarimeter camera; it is anticipated that such a camera can be scaled down to less than 1.5 cm. Two Savart plates are used at the pupil plane to generate multiple fringes to encode the full Stokes vector in a single image. A geometric ray model is developed to explain the system. The numerical simulation based on this model is presented. Finally, the validity of the device is demonstrated by showing experimental results. © 2008 Optical Society of America.
• McMillan, R. W., Dereniak, E., Aumiller, R., & Hagenb, N. (2008). Single-frame polarization measurement techniques. Proceedings of SPIE - The International Society for Optical Engineering, 6972.
  More info

  Abstract: This paper will describe methods of measuring all of the components of the Stokes polarization vector for each pixel in a scene using only one frame of passive optical sensor data, one radar pulse, or one radiometer integration interval. Both active and passive sensors operating in any waveband from microwave to visible will be considered. For systems operating in the millimeter wave and terahertz bands, the techniques developed by Dereniak and his students at the University of Arizona will be discussed. For other wavebands, a technique developed by the author that requires the coherent reception of two orthogonally-polarized signal components will be presented. This latter method works for both for both broad-band and narrow-band active or passive signals, but requires focal planes and hardware in the visible and infrared bands that may be too complicated for many applications. Results of calculations made for the millimeter and terahertz bands will be presented.
• Scholl, J. F., Hege, E. K., Hart, M., O'Connell, D., & Dereniak, E. L. (2008). Flash hyperspectral imaging of non-stellar astronomical objects. Proceedings of SPIE - The International Society for Optical Engineering, 7075.
  More info

  Abstract: There are certain classes of astronomical objects that have rather involved spectra that can also be a composite of a number of different spectral signatures, as well as spatial characteristics that can be used for identification and analysis. Such objects include galaxies and quasars with active nuclei, colliding / interacting galaxies, and globular cluster systems around our own Milky Way and other galaxies. Flash hyperspectral imaging adds coherence-time limited functionality so that Earth orbiting spacecraft and solar system objects such as planets, asteroids and comets can be spectrally imaged as well, as these also have both spatial and spectral structure rotating and moving within much shorter time spans. Flash hyperspectral imaging systems are, therefore, also useful for faster simultaneous spatial and spectral feature analysis. Previous work has explored spectral unmixing and other types of feature extraction of these general types of objects, but without consideration of the hyperspectral imaging system involved, neither in how the data is collected nor in how the datacube is reconstructed. We will present a proof of concept simulation of a resolved object as it is imaged through such a physically modeled imaging system and its datacube reconstructed. Finally, we provide a demonstration of the capability with astronomical data, Venus and a binary star, when constrained by our physical model of the instrumental transfer function.
• Vandervlugt, C., Sampson, R., Craven, J., Dereniak, E., & Gerhart, G. (2008). Computed tomographic imaging spectropolarimeter characterization. Proceedings of SPIE - The International Society for Optical Engineering, 7086.
  More info

  Abstract: A computed tomographic imaging spectrometer (CTIS) is an instrument which can simultaneously obtain image spatial and spectral information without moving parts in a single focal plane array integration time. When this instrument is combined with a channeled spectropolarimeter, the instrument can also obtain complete Stokes polarization information at each resolution element. The combined instrument, called a computed tomographic imaging channeled spectropolarimeter (CTICS), has been developed in the visible wavelength region. This paper summarizes the CTICS design and results obtained from data acquired during field testing of the CTICS instrument.
• Aumiller, R. W., Dereniak, E. L., Sampson, R., & McMillan, R. W. (2007). Longwave infrared snapshot imaging spectropolarimeter. Proceedings of SPIE - The International Society for Optical Engineering, 6660.
  More info

  Abstract: A very unique imaging spectopolarimeter for use in the long wave infrared, 8 to 12 microns, is currently being constructed. The imaging system uses a novel technique first developed at the University of Arizona, which incorporates channeled spectropolarimetry with a computed tomographic imaging spectrometer (CTIS). The system is especially noteworthy because it contains no moving parts and operates in a snapshot mode, allowing it to record spectral data as well as the polarization state of each wavelength band in the spectra from every spatial location in a 2D image in a single integration period. The paper presents results from the currently constructed longwave infrared snapshot imaging spectrometer, as well as a description of what will be added to the system to obtain polarization data, and an overview of the design and operational details of the snapshot imaging spectropolarimeter.
• Dereniak, E., Hagen, N., Kupinski, M., & Dereniak, E. L. (2007). Gaussian profile estimation in one dimension. Applied optics, 46(22).
  More info

  We present several new results on the classic problem of estimating Gaussian profile parameters from a set of noisy data, showing that an exact solution of the maximum likelihood equations exists for additive Gaussian-distributed noise. Using the exact solution makes it possible to obtain analytic formulas for the variances of the estimated parameters. Finally, we show that the classic formulation of the problem is actually biased, but that the bias can be eliminated by a straightforward algorithm.
• Dereniak, E., Hagen, N., Oka, K., & Dereniak, E. L. (2007). Snapshot Mueller matrix spectropolarimeter. Optics letters, 32(15).
  More info

  We present a new snapshot technique for performing spectrally resolved Mueller matrix polarimetry. The basic approach is an extension of the channeled spectropolarimetry technique, employing frequency-domain interferometry to encode polarization information into modulation of the spectrum.
• Hagen, M. N., & Dereniak, E. L. (2007). New grating designs for a CTIS imaging spectrometer. Proceedings of SPIE - The International Society for Optical Engineering, 6565.
  More info

  Abstract: We present some new grating designs for use in a computed tomographic imaging spectrometer (CTIS) and discuss their differences with previous gratings. One of the advantages of the new designs is that they provide added flexibility for a tunable CTIS instrument, and we show some preliminary data illustrating this advantage.
• Hagen, N., & Dereniak, E. L. (2007). Snapshot Mueller matrix spectropolarimetry. Proceedings of SPIE - The International Society for Optical Engineering, 6682.
  More info

  Abstract: We present a snapshot technique for performing spectrally-resolved Mueller matrix polarimetry, based on channeled spectropolarimetry. After discussing the measurement theory in detail, we present a simulated measurement of a polymer achromatic retarder. Finally, we review some methods for modifying the technique to achieve improved performance.
• Hagen, N., Dereniak, E. L., & Sass, D. T. (2007). Fourier methods of improving reconstruction speed for CTIS imaging spectrometers. Proceedings of SPIE - The International Society for Optical Engineering, 6661.
  More info

  Abstract: A persistent barrier to the wider use of the Computed Tomographic Imaging Spectrometer (CTIS) has been the extraordinary demands it places on computational resources. Raw images can be obtained at snapshot speeds, but reconstructed datacubes typically require minutes of reconstruction time each. We present a new approach to the CTIS reconstruction problem which makes use of the spatial shift-invariance in a CTIS system to greatly reduce the dimensionality of the matrix inversion process performed during reconstruction. Preliminary results indicate that a speedup by a factor of 4000 is possible.
• Hagen, N., Kupinski, M., & Dereniak, E. L. (2007). Gaussian profile estimation in one dimension. Applied Optics, 46(22), 5374-5383.
  More info

  PMID: 17676153;PMCID: PMC2464285;Abstract: We present several new results on the classic problem of estimating Gaussian profile parameters from a set of noisy data, showing that an exact solution of the maximum likelihood equations exists for additive Gaussian-distributed noise. Using the exact solution makes it possible to obtain analytic formulas for the variances of the estimated parameters. Finally, we show that the classic formulation of the problem is actually biased, but that the bias can be eliminated by a straightforward algorithm. © 2007 Optical Society of America.
• Hagen, N., Oka, K., & Dereniak, E. L. (2007). Snapshot Mueller matrix spectropolarimeter. Optics Letters, 32(15), 2100-2102.
  More info

  PMID: 17671549;Abstract: We present a new snapshot technique for performing spectrally resolved Mueller matrix polarimetry. The basic approach is an extension of the channeled spectropolarimetry technique, employing frequency-domain interferometry to encode polarization information into modulation of the spectrum. © 2007 Optical Society of America.
• Hartke, J., & Dereniak, E. L. (2007). Snapshot dual-band visible hyperspectral imaging spectrometer. Optical Engineering, 46(1).
  More info

  Abstract: We describe a proof of concept for a snapshot dual-band visible hyperspectral imaging spectrometer. A commercially available digital camera was integrated into a computed tomographic imaging spectrometer to provide a means for this proof of concept. Two spatially coregistered data cubes covering the blue (400 to 500 nm) and red (600 to 700 nm) spectral regions were reconstructed and the results analyzed. We found that the system accurately reconstructs the spectral content of the scene and that the two data cubes are automatically spatially coregistered by virtue of the system design. © 2007 Society of Photo-Optical Instrumentation Engineers.
• Kudenov, M. W., Hagen, N. A., Dereniak, E. L., & Gerhart, G. R. (2007). Fourier transform channeled spectropolarimetry in the MWIR. Optics Express, 15(20), 12792-12805.
  More info

  PMID: 19550549;Abstract: A complete Fourier Transform Spectropolarimeter in the MWIR is demonstrated. The channeled spectral technique, originally developed by K. Oka, is implemented with the use of two Yttrium Vanadate (YVO4) crystal retarders. A basic mathematical model for the system is presented, showing that all the Stokes parameters are directly present in the interferogram. Theoretical results are compared with real data from the system, an improved model is provided to simulate the effects of absorption within the crystal, and a modified calibration technique is introduced to account for this absorption. Lastly, effects due to interferometer instabilities on the reconstructions, including nonuniform sampling and interferogram translations, are investigated and techniques are employed to mitigate them. ©2007 Optical Society of America.
• Levan, P. D., Hartke, J. P., Dereniak, E. L., & Beecken, B. P. (2007). Extending hyperspectral capabilities with dualband infrared focal plane arrays. Proceedings of SPIE - The International Society for Optical Engineering, 6479.
  More info

  Abstract: Dualband infrared focal plane arrays (FPA) were developed originally for multi-spectral imaging applications, where their advantages in compactness and band-to-band pixel registration, relative to conventional multispectral imagers, were recognized. As dualband FPA architecture is matured for quantum well and mercury cadmium telluride focal plane arrays, and becomes within the grasp of strained layer superlattice technology, applications in addition to multi-waveband imaging come to mind. In various hyperspectral applications that employ gratings, the different grating orders can sometimes be paired with the wavebands of the dual- (or multi-) waveband FPA, allowing high efficiency hyperspectral imaging over very broad wavelength regions. Exploiting the "third dimension" of FPA detecting layers for dual- and multi-waveband capability proved its usefulness for multi-waveband imaging; this paper will show similar advantages for hyperspectral applications and describe such applications.
• Scholl, J. F., Hege, E. K., O'Connell, D., & Dereniak, E. L. (2007). Model based compression of the calibration matrix for hyperspectral imaging systems. Proceedings of SPIE - The International Society for Optical Engineering, 6700.
  More info

  Abstract: In hyperspectral imaging systems with a continuous-to-discrete (CD) model, the goal is to solve the matrix equation g = Hθ + n for θ. Here g is a data vector obtained on pixels on a focal plane array (FPA), and n is the additive pixel noise vector. The hyperspectral object cube f(x, y, λ) to be recovered is represented by θ, which is the vectorized set of expansion coefficients of f with respect to a family of functions. The imaging operator is the system matrix H of which its columns represent the projection of each expansion function onto the FPA. Hence an estimate of the object cube f(x, y, λ) is reconstructed from these recovered expansion function projection coefficients. Furthermore H is equivalently a calibration matrix, and amenable to an analytic description. Since the number of expansion functions is large, and the number of pixels on an FPA is large, H becomes huge and very unwieldy to store. We describe a means by which we can reduce the effective size of H by taking advantage of the analytic model of the imaging system and converting H into a series of look-up tables. By this method we have been able to drastically reduce the storage requirements for H from terabytes to sub-megabyte sizes. We provide an example of this technique in isoplanatic and polychromatic calibration of a flash hyperspectral imaging system. These sets of lookup tables are expansion function independent and also independent of object cube sampling.
• Vandervlugt, C., Hagen, N., Sampson, R., Dereniak, E., & Gerhart, G. (2007). Visible imaging spectro-polarimeter. Proceedings of SPIE - The International Society for Optical Engineering, 6661.
  More info

  Abstract: A computed tomography imaging channeled spectropolarimeter (CTICS) is a combination of a computed tomography imaging spectrometer (CTIS) and a channeled spectropolarimeter (CHSP). The CTICS instrument can simultaneously obtain image spatial and spectral information as well as polarization Stokes vectors at each resolution element in a single focal plane array (FPA) integration time with no moving parts. An instrument has been designed and built for the visible wavelength region at the University of Arizona. Performance testing is underway. In this work, we present initial results from data acquired during testing of the CTICS instrument.
• Vandervlugt, C., Masterson, H., Hagen, N., & Dereniak, E. L. (2007). Reconfigurable liquid crystal dispersing element for a Computed Tomography Imaging Spectrometer. Proceedings of SPIE - The International Society for Optical Engineering, 6565.
  More info

  Abstract: A Computed Tomography Imaging Spectrometer (CTIS) is an imaging spectrometer which can acquire a multi-spectral data set in a single snapshot (one focal plane array integration time) with no moving parts. Currently, CTIS instruments use a specially designed computer generated hologram (CGH) to disperse the light from a given spectral band into a grid of diffraction orders. The capabilities of the CTIS instrument can be greatly improved by replacing the static CGH dispersing element with a reconfigurable liquid crystal spatial light modulator. The liquid crystal spatial light modulator is tuned electronically, enabling the CTIS to remain a non-scanning imaging spectrometer with no moving parts. The ability to rapidly reconfigure the dispersing element of the CTIS allows the spectral and spatial resolution to change by varying the number of diffraction orders, diffraction efficiency, etc. In this work, we present the initial results of using a fully addressable, 2-D liquid crystal spatial light modulator as the dispersing element in a CTIS instrument.
• Aumiller, R. W., Hagen, N. A., Dereniak, E. L., Sampson, R., & McMillan, R. W. (2006). Design of an LWIR snapshot imaging spectropolarimeter. Proceedings of SPIE - The International Society for Optical Engineering, 6295.
  More info

  Abstract: This paper covers the design and construction of a snapshot imaging spectropolarimeter for use in the long wave infrared, 8 to 12 micron region. This imaging device is unique in the fact that system is nonscanning, contains no moving parts, and in a single integration period is able to record spectral data as well as the polarization state as a function of wavelength from every spatial location in a 2D image. The system is based on the Computed Tomographic Imaging Spectrometer, commonly referred to as CTIS, and has been modified to incorporate components of Channeled Spectropolarimetry. The paper presents an overview of how both the CTIS and the CTICS (Computed Tomographic Imaging Channeled Spectropolarimeter) systems work, details on the specific components used in the LWIR system, and preliminary results from a completed LWIR CTIS system, which is the first of its kind.
• Cohen, M. J., & Dereniak, E. L. (2006). Proceedings of SPIE - The International Society for Optical Engineering: Introduction. Proceedings of SPIE - The International Society for Optical Engineering, 6119, ix-x.
• Dereniak, E., Luo, H., Oka, K., Hagen, N., Tkaczyk, T., & Dereniak, E. L. (2006). Modeling and optimization for a prismatic snapshot imaging polarimeter. Applied optics, 45(33).
  More info

  Thin birefringent prisms placed near an image plane introduce sinusoidal fringes onto a 2D polarized scene making possible a snapshot imaging polarimeter, which encodes polarization information into the modulation of the fringes. This approach was introduced by Oka and Kaneko [Opt. Express 11, 1510 (2003)], who analyzed the instrument through the Mueller calculus. We show that the plane-wave assumption adopted in the Mueller theory can introduce unnecessary error in a polarimeter design. To directly take prism effects such as beam splitting and deviating into accounts we introduce a geometric imaging model, which allows for a versatile simulation of the birefringent prisms and provides a means for optimization. A calcite visible system is investigated as an example, which essentially shows how each design parameter affects the overall image quality and how to modify the polarimeter design to optimize overall performance. The approach is applicable to any prismatic imaging polarimeter with different prism materials and different working wavelengths.
• Hagen, N., Dereniak, E. L., & Sass, D. T. (2006). Maximizing the resolution of a CTIS instrument. Proceedings of SPIE - The International Society for Optical Engineering, 6302.
  More info

  Abstract: Computed Tomographic Imaging Spectrometry (CTIS) is a technique which has been around for over a decade, providing snapshot measurements of datacubes as large as (x,y,λ) = (100,100,300). We discuss the difficulties with maximizing the resolution of a CTIS instrument and some new grating design ideas for realizing performance improvements.
• Hartke, J., Dereniak, E., & LeVan, P. D. (2006). Non-scanning dual infrared band hyperspectral imaging spectrometer design. Proceedings of SPIE - The International Society for Optical Engineering, 6295.
  More info

  Abstract: Recent advances in dual band infrared focal plane technology now enable the design and testing of a dual infrared band snapshot imaging spectrometer, the first-ever of its kind. A review of proof of concept results from a dual-visible-band Computed Tomographic Imaging Spectrometer (CTIS) system is presented. The dual-visible system demonstrates that it is possible to reconstruct two spatially co-registered hyperspectral data cubes covering different spectral bands. Based on the visible band CTIS proof of concept, a similar infrared system is now proposed. Critical to the CTIS system is the design of the Computer Generated Holographic (CGH) disperser. Several different (CGH) designs are considered. A first order optical design for the dual infrared band CTIS is presented.
• Kudenov, M. W., Hagen, N. A., Luo, H., Dereniak, E. L., Robertson, S., Montilla, L. G., Vo, T. B., Tam, J., Nichols, J. D., & Gerhart, G. R. (2006). Polarization acquisition using a commercial Fourier transform spectrometer in the MWIR. Proceedings of SPIE - The International Society for Optical Engineering, 6295.
  More info

  Abstract: A spectropolarimeter utilizing an Oriel MIR8000 Fourier Transform Spectrometer in the MWIR is demonstrated. The use of the channeled spectral technique, originally developed by K. Oka, is created with the use of two AR coated Yttrium Vanadate (YVO 4) crystal retarders with a 2:1 thickness ratio. A basic mathematical model for the system is presented, showing that the Stokes parameters are directly present in the interferogram. Theoretical results are then compared with real data from the system, an improved model is provided to simulate the effects of absorption within the crystal, and error between reconstructions with phase-corrected and raw interferograms is analyzed.
• Luo, H. T., Tkaczyk, T., Dereniak, E. L., Oka, K., & Sampson, R. (2006). High birefringence of the yttrium vanadate crystal in the middle wavelength infrared. Optics Letters, 31(5), 616-618.
  More info

  PMID: 16570416;Abstract: A high birefringence of over 0.21 for the yttrium vanadate (YVO 4) crystal in the middle wavelength infrared (i.e., 3-5 μm) was measured. A Fourier transform infrared spectrometer was employed in the channel spectra technique to obtain the measurements. © 2006 Optical Society of America.
• Luo, H., Oka, K., Hagen, N., Tkaczyk, T., & Dereniak, E. L. (2006). Modeling and optimization for a prismatic snapshot imaging polarimeter. Applied Optics, 45(33), 8400-8409.
  More info

  PMID: 17086247;Abstract: Thin birefringent prisms placed near an image plane introduce sinusoidal fringes onto a 2D polarized scene making possible a snapshot imaging polarimeter, which encodes polarization information into the modulation of the fringes. This approach was introduced by Oka and Kaneko [Opt. Express 11, 1510 (2003)], who analyzed the instrument through the Mueller calculus. We show that the plane-wave assumption adopted in the Mueller theory can introduce unnecessary error in a polarimeter design. To directly take prism effects such as beam splitting and deviating into accounts we introduce a geometric imaging model, which allows for a versatile simulation of the birefringent prisms and provides a means for optimization. A calcite visible system is investigated as an example, which essentially shows how each design parameter affects the overall image quality and how to modify the polarimeter design to optimize overall performance. The approach is applicable to any prismatic imaging polarimeter with different prism materials and different working wavelengths. © 2006 Optical Society of America.
• Luo, H., Tkaczyk, T., Sampson, R., & Dereniak, E. L. (2006). Birefringence of yttrium vanadate single crystals in the middle wavelength infrared. Proceedings of SPIE - The International Society for Optical Engineering, 6119.
  More info

  Abstract: The birefringence of the yttrium vanadate (YVO 4) crystals have been measured for the first time in the middle wavelength infrared (MWIR), i.e., 3-5μm. A Fourier transform spectrometer has been used in the channel spectra technique to achieve a quick measurement. Large birefringence over 0.21 has been observed in the YVO 4 crystals. The transmission over 2.5-17μm of the YVO 4 (0.7mm thick) has been measured, which showed a transparent range up to 5.3μm. These unique features illustrate the good potential of this material for the MWIR polarization applications.
• Scholl, J. F., Hege, E. K., Lloyd-Hart, M., & Dereniak, E. L. (2006). Figure of merit calculations for spectral unmixing and classification algorithms. Proceedings of SPIE - The International Society for Optical Engineering, 6315.
  More info

  Abstract: Abundances of material components in objects are usually computed using techniques such as linear spectral unmixing on individual pixels captured on hyperspectral imaging devices. The effectiveness of these algorithms usually depends on how distinct the spectral signatures in the libraries used in them are. This can be measured by SVD or Least Squares based figures of merit such as the condition number of the matrix consisting of the library signatures. However, it must be noted that each library signature usually is the mean of a number of signatures representing that material, or class of objects. This aspect of how individual library spectral signatures vary in real-world situations needs to be addressed in order to more accurately assess linear unmxing techniques. These same considerations also goes for signature libraries transformed into new ones by wavelet or other transforms. Figures of merit incorporating variations within each library signature (which more accurately reflects real measurements) will be implemented and compared with other figures of merit not taking these variations into account.
• Scholl, J. F., Hege, E. K., Lloyd-Hart, M., & Dereniak, E. L. (2006). Hyperspectral feature classification with alternate wavelet transform representations. Proceedings of SPIE - The International Society for Optical Engineering, 6315.
  More info

  Abstract: The effectiveness of many hyperspectral feature extraction algorithms involving classification (and linear spectral unmixing) are dependent on the use of spectral signature libraries. If two or more signatures are roughly similar to each other, these methods which use algorithms such as singular value decomposition (SVD) or least squares to identify the object will not work well. This especially goes for these procedures which are combined with three-dimensional discrete wavelet transforms, which replace the signature libraries with their corresponding lowpass wavelet transform coefficients. In order to address this issue, alternate ways of transforming these signature libraries using bandpass or highpass wavelet transform coefficients from either wavelet or Walsh (Haar wavelet packet) transforms in the spectral direction will be described. These alternate representations of the data emphasize differences between the signatures which lead to improved classification performance as compared to existing procedures.
• Scholl, J. F., Hege, E. K., Lloyd-Hart, M., O'Connell, D., Johnson, W. R., & Dereniak, E. L. (2006). Evaluations of classification and spectral unmixing algorithms using ground based satellite imaging. Proceedings of SPIE - The International Society for Optical Engineering, 6233 II.
  More info

  Abstract: Abundances of material components in objects are usually computed using techniques such as linear spectral unmixing on individual pixels captured on hyperspectral imaging devices. However, algorithms such as unmixing have many flaws, some due to implementation, and others due to improper choices of the spectral library used in the unmixing (as well as classification). There may exist other methods for extraction of this hyperspectral abundance information. We propose the development of spatial ground truth data from which various unmixing algorithm analyses can be evaluated. This may be done by implementing a three-dimensional hyperpspectral discrete wavelet transform (HSDWT) with a low-complexity lifting method using the Haar basis. Spectral unmixing, or similar algorithms can then be evaluated, and their effectiveness can be measured by how well or poorly the spatial and spectral characteristics of the target are reproduced at full resolution (which becomes single object classification by pixel).
• Cohen, M. J., & Dereniak, E. L. (2005). Proceeding of SPIE - The International Society for Optical Engineering: Introduction. Proceedings of SPIE - The International Society for Optical Engineering, 5726, ix.
• Dereniak, E. L. (2005). Infrared spectro-polarimeter. Proceedings of SPIE - The International Society for Optical Engineering, 5957, 1-10.
  More info

  Abstract: A revolutionary technique for snapshot imaging spectro-polarimetry has been developed at the University of Arizona due to the recent availability of large focal plane arrays and greater computing performance on research workstations. The technique involves the combination of an imaging polarimeter 1 with computed tomography imaging spectrometer (CTIS). This spectro-polarimeter uses modulation to encode the spectral dependence of all four Stokes parameters into a spectrum. CTIS is a snapshot imaging spectrometry method in which both spatial and spectral information is reconstructed using the inverse mathematical technique of medical computed tomography. The combination of these techniques provides the basis for a snapshot imaging complete Stokes spectro-polarimeter that can be implemented with no moving parts for the infrared spectrum.
• Hagen, N., Dereniak, E. L., & Sass, D. T. (2005). Visible snapshot imaging spectro-polarimeter. Proceedings of SPIE - The International Society for Optical Engineering, 5888, 1-10.
  More info

  Abstract: We present the first visible-spectrum snapshot imaging spectro-polarimeter based on a Computed Tomographic Imaging Spectrometer (CTIS). Improvements to our calibration methods have provided advances in the CTIS spectral resolution and in noise suppression which obstructed previous attempts to construct such an instrument. The resulting device is capable of 75 × 75 spatial resolution, 1 nm spectral resolution across the visible spectrum (400nm-720nm), at video frame rates. The instrument is also capable of complete Stokes vector polarimetry at a reduced spectral resolution (∼10nm).
• Sabatke, D. S., Locke, A. M., Dereniak, E. L., & McMillan, R. W. (2005). Linear operator theory of channeled spectropolarimetry. Journal of the Optical Society of America A: Optics and Image Science, and Vision, 22(8), 1567-1576.
  More info

  PMID: 16134852;Abstract: Channeled spectropolarimetry is a snapshot method of measuring the spectral and polarization content of light. Wave-number domain amplitude modulation is employed to encode all four Stokes component spectra into a single optical power spectrum. We model the channeled spectropolarimeter as a linear operator, which facilitates treatment of nonideal effects and provides a convenient framework for simulations, calibration, and reconstruction. The operator's singular value decomposition is treated with analytic and computational approaches. This analysis highlights the importance of the choice of object space in constraining and imparting prior knowledge to linear reconstructions of data from underdetermined systems. © 2005 Optical Society of America.
• Scholl, J. F., Dereniak, E. L., & Hege, E. K. (2005). Fast feature extraction in hyperspectral imagery via lifting wavelet transforms. Proceedings of SPIE - The International Society for Optical Engineering, 5915, 1-12.
  More info

  Abstract: Feature extraction from hyperspectral imagery consumes large amounts of memory. Hence the algorithms to do this have high computational complexity and require large amounts of additional computer memory. To address these issues previous work has concentrated on algorithms that are combinations of a fast integer-based hyperspectral discrete wavelet transform (HSDWT) with a specialized implementation of the Haar basis and improved implementations of linear spectral unmixing. Extensions of that previous work are presented here that modify and extend these algorithms to investigate feature extraction of arbitrary shaped spatial regions and incorporate more general biorthogonal bases for processing of spectral signatures. Finally, these wavelet transform implementations have also been used to simulate linear spectral unmixng techniques on spatially unresolved objects such as binary stars and globular star clusters.
• Tkaczyk, T. S., Dereniak, E. L., Gaalema, S., Bahn, W., Sun, S., Erickson, T., Rogers, J. D., Christenson, T. C., Richards-Kortum, R., & Descour, M. R. (2005). High speed CMOS for structured illumination technique. Proceedings of SPIE - The International Society for Optical Engineering, 5726, 77-84.
  More info

  Abstract: This paper discusses the selection of parameters and the design of a CMOS detector for use in a structured illumination technique implemented with a 4M device (Miniaturized Multi-Modal Microscope) for precancer detection. To obtain real time sectioning the framing rate was set on the order of 500 frames / sec. 500 images allow us to obtain 8 to 16 sections / sec reconstructed from 16 to 64 images. The reconstruction technique is a sine approximation algorithm. To obtain a 1 μm spatial resolution, the required pixel size is 4 μm with a magnification 4:1. The field of extent of 250μm required approximately 350 × 350 array size.
• Tkaczyk, T. S., Rogers, J. D., Rahman, M., Christenson, T. C., Gaalema, S., Dereniak, E. L., Richards-Kortum, R., & Descour, M. R. (2005). Multi-modal miniature microscope - 4M Device for bio-imaging applications: An overview of the system. Proceedings of SPIE - The International Society for Optical Engineering, 5959, 1-9.
  More info

  Abstract: The multi-modal miniature microscope (4M) device to image morphology and cytochemistry in vivo is a microscope on a chip including optical, micro-mechanical, and electronic components. This paper describes all major system components: optical system, custom high speed CMOS detector and comb drive actuator. The hybrid sol-gel lenses, their fabrication and assembling technology, optical system parameters, and various operation modes (fluorescence, reflectance, structured illumination) are also discussed. A particularly interesting method is a structured illumination technique that delivers confocal-imaging capabilities and may be used for optical sectioning. For reconstruction of the sectioned layer a sine approximation algorithm is applied. Structured illumination is produced with LIGA fabricated actuator scanning in resonance. The spatial resolution of the system is 1 μm, and was magnified by 4x matching the CMOS pixel size of 4 μm (a lateral magnification is 4:1), and the extent of field of the system is 250μm, An overview of the 4M device is combined with the presentation of imaging results for epithelial cell phantoms with optical properties characteristic of normal and cancerous tissue labeled with nanoparticles.
• Hagen, N., Locke, A. M., Sabatke, D. S., Dereniak, E. L., & Sass, D. T. (2004). Methods and applications of snapshot spectropolarimetry. Proceedings of SPIE - The International Society for Optical Engineering, 5432, 167-174.
  More info

  Abstract: We present adaptations of the channelled spectropolarimetry technique, a method which allows both spectral and polarization information to be captured in a single integration period. The first adaptation uses a mathematical decomposition of the system matrix, which is then modified for imaging spectropolarimetry; the second adaptation is applied first to a single-point and then to an imaging system, for which we also show applications and measurements from experimental work.
• Hartke, J., & Dereniak, E. L. (2004). Hyperspectral-dual spectral region imaging spectrometer. Proceedings of SPIE - The International Society for Optical Engineering, 5563, 156-166.
  More info

  Abstract: A temporally and spatially non-scanning imaging spectrometer covering two separate spectral bands in the visible region using computed tomographic imaging techniques is described. The computed tomographic techniques allows for the construction of a three dimensional hyperspectral data cube (x, y, λ) from the two dimensional input in a single frame time. A computer generated holographic dispersive grating is used to disperse the incoming light into several diffraction orders on a focal plane composed of interwoven pixels independently sensitive to the two bands of interest. Separating the input of the two pixel types gives co-registered output between the two bands and overcomes the limitation of overlapping orders. The proof of concept in the visible is presented using a commercially available camera and the extension to the infrared is proposed.
• Hege, K., O'Connell, D., Johnson, W., Basty, S., & Dereniak, E. (2004). Hyperspectral Imaging for Astronomy and Space Surviellance. Proceedings of SPIE - The International Society for Optical Engineering, 5159, 380-391.
  More info

  Abstract: We present results of field evaluations of computed tomography imaging spectrometer (CTIS) systems, using an adaptive optics (AO) compensated telescope, for applications in astronomical multispectral imaging and imaging spectroscopy in both visible (0.4 - 0.7 μm) and near infrared (1.2 - 2.1 μm) bands. We develop and analyze a convolution model for this hyperspectral imaging method which includes a convolution representation of the effects of the AO system. We use expectation maximization, with additional prior constraints derived from the physics of the instrumental, statistical and atmospheric effects inherent in such observations, to extract details of features in the hyperspectral images. Data for this study were obtained using the Advanced Electro-Optics System (AEOS) - a facility of the Air Force Maui Space Surviellance System.
• Johnson, W. R., Hege, K., O'Connell, D., & Dereniak, E. L. (2004). Recovery of a flawed hyperspectral imager calibration using optical modeling. Optics Express, 12(10), 2251-2257.
  More info

  PMID: 19475061;Abstract: A reconstructed hyperspectral datacube has been successfully recovered from a badly flawed point-spread function (PSF) observation. The corrected PSF alleviated unnoticed detector saturation and misregistration artifacts in the calibration of a crucial, irreplaceable near-infrared flash hyperspectral imager dataset. This flawed PSF induced a defocus-like artifact as well as spectral distortions in the three-dimensional hyperspectral estimate of the data. The PSF artifacts, which would have caused severe misinterpretation of the spatio-spectral information, were correctable post detection using an optical model of the PSF constrained by the available flawed calibration. © 2004 Optical Society of America.
• Johnson, W. R., O'Connell, D., Dereniak, E. L., & Hege, E. K. (2004). Novel calibration recovery technique for an expectation maximization tomographic reconstruction. Optical Engineering, 43(1), 10-11.
  More info

  Abstract: An experiment is conducted that successfully reduces the amount of aberration detected in a reconstructed hyperspectral datacube. The correction alleviates an unnoticed rotational misalignment in the calibration of our near-infrared flash hyperspectral imager. This alteration induces a spherical-aberration-like artifact as well as spectral defects because of the three-dimensional hyperspectral quality of the data. This artifact, which would cause severe misregistration of the spatio-spectral information, is correctable post detection. © 2004 Society of Photo-Optical Instrumentation Engineers.
• Kinder, B. A., Garcia, J. P., Habbit, R. D., & Dereniak, E. L. (2004). Ranging-Imaging Spectrometer. Proceedings of SPIE - The International Society for Optical Engineering, 5159, 73-81.
  More info

  Abstract: An imaging spectrometer that can simultaneously obtain 3-D spatial and hyperspectral data has been developed. The Ranging-Imaging Spectrometer (RIS) is based on the Computed Tomographic Imaging Spectrometer (CTIS) developed at the Optical Science Center, and the Scannerless Laser Radar (LADAR) architecture developed at Sandia National Labs. The instrument acquires hyperspectral data in a single snapshot and spatial data in a series of snapshots. The system has 29 spectral bands, 1024 range samples, and approximately 80 × 80 spatial sampling. The RIS calibration is discussed along with analysis of test data.
• Scholl, J. F., & Dereniak, E. L. (2004). Fast wavelet based feature extraction of spatial and spectral information from hyperspectral datacubes. Proceedings of SPIE - The International Society for Optical Engineering, 5546, 285-293.
  More info

  Abstract: An ongoing problem for feature extraction in hyperspectral imagery is that such data consumes large amounts of memory and transmittance bandwidth. In many applications, especially on space based platforms, fast, low power feature extraction algorithms are necessary, but not feasible. To overcome many of the problems due to the large volume of hyperspectral data we have developed a fast, low complexity feature extraction algorithm that is a combination of a fast integer-valued hyperspectral discrete wavelet transform (HSDWT) using a specialized implementation of the Haar basis and an improved implementation of linear spectral unmixing. The Haar wavelet transform implementation involves a simple weighted sum and a weighted difference between pairs of numbers. Features are found by using a small subset of the transform coefficients. More refined spatial and/or spectral identifications can then be made by localized fast inverse Haar transforms using very small numbers of additional coefficients in the spatial or spectral directions. The computational overhead is reduced further since much of the information used for linear spectral unmixing is precomputed and can be stored using a very small amount of additional memory.
• Scholl, J. F., & Dereniak, E. L. (2004). Higher-dimensional wavelet transforms for hyperspectral data compression and feature recognition. Proceedings of SPIE - The International Society for Optical Engineering, 5208, 129-140.
  More info

  Abstract: The dominant image processing tasks for hyperspectral data are compression and feature recognition. These tasks go hand-in-hand. Hyperspectral data contains a huge amount of information that need to be processed (and often very quickly) depending on the application. The discrete wavelet transform is the ideal tool for this type of data structure. There are applications that require such processing (especially feature recognition or identification) be done extremely fast and efficiently. Furthermore the higher number of dimensions implies a number of different ways to do these transforms. Much of the work in this area to the present time has been focused on JPEG2000 type compression of each component image involving fairly sophisticated coding techniques; relatively little attention has been paid to other configurations of wavelet transforms of such data, as well as rapid feature identification where compression may not be necessary at all. This paper describes other versions of the 3D wavelet transform that allow the resolution in both the spatial domain and spectral domain to be adjusted separately. Other issues associated with low complexity feature recognition with and without compression using versions of the 3D hyperspectral wavelet transforms will be discussed along with some illustrative calculations.
• Scholl, J. F., Thome, K. J., & Dereniak, E. L. (2004). Normalized difference vegetation index calculations from JPEG2000 compressed Landsat 7 images. Proceedings of SPIE - The International Society for Optical Engineering, 5561, 84-95.
  More info

  Abstract: An ongoing problem in remote sensing is that imagery generally consumes considerable amounts of memory and transmittance bandwidth, thus limiting the amount of data acquired. The use of high quality image compression algorithms, such as the wavelet-based JPEG2000, has been proposed to reduce much of the memory and bandwidth overhead; however, these compression algorithms are often lossy and the remote sensing community has been wary to implement such algorithms for fear of degradation of the data. We explore this issue for the JPEG2000 compression algorithm applied to Landsat-7 Enhanced Thematic Mapper (ETM+) imagery. The work examines the effect that lossy compression can have on the retrieval of the normalized difference vegetation index (NDVI). We have computed the NDVI from JPEG2000 compressed red and NIR Landsat-7 ETM+ images and compared with the uncompressed values at each pixel. In addition, we examine the effects of compression on the NDVI product itself. We show that both the spatial distribution of NDVI and the overall NDVI pixel statistics in the image change very little after the images have been compressed then reconstructed over a wide range of bitrates.
• Tebow, C. P., Dereniak, E. L., Garrood, D., Dorschner, T. A., & Volin, C. E. (2004). Tunable snapshot imaging spectrometer. Proceedings of SPIE - The International Society for Optical Engineering, 5159, 64-72.
  More info

  Abstract: The acquisition of a multi-spectral data set in a single FPA integration time (snapshot) with no moving parts or scanning is possible with a Computed Tomographic Imaging Spectrometer (CTIS). CTIS instruments employ specially designed computer generated holograms (CGH) etched in an appropriate media for the wavelength band of interest as the dispersing element. The replacement of current etched CGHs with an electronically tunable liquid crystal Optical Phase Array (OPA) extends the capabilities of the CTIS by adding the ability to change its configuration while maintaining its basic motivation as a non-scanning imaging spectrometer with no moving parts. This tunability allows the dispersion, number of diffraction orders, and diffraction efficiency of the orders to be changed affecting the instrument's spectral resolution, data cube reconstruction quality and speed. This publication presents the results of characterizing the OPA phase vs. applied voltage profile and the feedback algorithm used to program the OPA as a CTIS disperser.
• Dereniak, E. L., Hagen, N. A., Johnson, W. R., Sabatke, D. S., Locke, A. M., McMillan, R. W., & Hamilton, T. K. (2003). Imaging spectropolarimetry. Proceedings of SPIE - The International Society for Optical Engineering, 5074, 272-285.
  More info

  Abstract: Spectrometry and polarimetry measurements are important to modern science and engineering in an extremely wide variety of fields. The basic principle is that when light is emitted or absorbed by, scattered or reflected from, or transmitted through a physical material, its spectral content and polarization state are often affected. Analysis of the changes imposed by these processes then has the potential to reveal useful information about the sources.
• Descour, M. R., Tkaczyk, T. S., Ford, B. K., Lynch, R. M., Locke, A., & Dereniak, E. (2003). The computed tomography imaging spectrometer. Conference Proceedings - Lasers and Electro-Optics Society Annual Meeting-LEOS, 1, 460-461.
  More info

  Abstract: A review is given of the CTIS system operation principle, its capabilities and past bio-imaging applications. Additionally, future CTIS combinations with structured illumination, polarimetric imaging, and 3D spectral imaging are discussed.
• Hagen, N. A., Sabatke, D. S., Scholl, J. F., Jansson, P. A., Chen, W. W., Dereniak, E. L., & Sass, D. T. (2003). Compact Methods for Measuring Stress Birefringence. Proceedings of SPIE - The International Society for Optical Engineering, 5158, 45-53.
  More info

  Abstract: The recent development of channelled spectropolarimetry presents opportunities for spectropolarimetric measurements of dynamic phenomena in a very compact instrument. We present measurements of stress-induced birefringence in an ordinary plastic by both a reference rotating-compensator spectropolarimeter and a channelled spectropolarimeter. The agreement between the two instruments shows the promise of the channelled technique and provides a proof-of-principle that the method can be used for a very simple conversion of imaging spectrometers into imaging spectropolarimeters.
• Locke, A. M., Salyer, D., Sabatke, D. S., & Dereniak, E. L. (2003). Design of a SWIR Computed Tomographic Imaging Channeled Spectropolarimeter. Proceedings of SPIE - The International Society for Optical Engineering, 5158, 12-23.
  More info

  Abstract: We present the implementation of snapshot imaging spectropolarimetry in a short-wave infrared (SWIR) system. It is the first of its kind to provide imaging spectropolarimetry with no moving parts and snapshot capability. This has applications in many fields, such as mining, biomedical imaging, and astronomy. The SWIR Computed Tomographic Imaging Channeled Spectropolarimeter (CTICS) is a snapshot imaging spectropolarimeter with 54×46 pixel spatial resolution and 10-band spectral resolution from 1.25-1.99 μm for the purpose of object identification. First, we present the design of the two main parts: the Computed Tomography Imaging Spectrometer (CTIS) and the channeled spectropolarimetry components. A discussion follows on the reconstruction technique. We then present the final assembled system and testing results.
• Sabatke, D. S., Locke, A. M., Dereniak, E. L., & McMillan, R. W. (2003). Linear calibration and reconstruction techniques for channeled spectropolarimetry. Optics Express, 11(22), 2940-2952.
  More info

  PMID: 19471414;Abstract: Channeled spectropolarimetry is a novel method of measuring the spectral and polarization content of light. It employs amplitude modulation to encode all four Stokes component spectra into a single optical power spectrum. We describe a practical approach to system calibration and object reconstruction, which is able to account for important non-ideal effects. These include dispersion in retarder materials and limited spectral resolution in the incorporated spectrometer. The spectropolarimeter is modeled as a linear operator, represented in practice by a matrix. The matrix is estimated in the calibration, and pseudoinverted subject to a constraint on object space for reconstructions. Experimental results are shown and compared with reference measurements. An example is given of the technique's application to the characterization of time-varying, stress-induced birefringence. © 2003 Optical Society of America.
• Scholl, J. F., Dereniak, E. L., Descour, M. R., Tebow, C. P., & Volin, C. E. (2003). Phase grating design for a dual-band snapshot imaging spectrometer. Applied Optics, 42(1), 18-29.
  More info

  PMID: 12518819;Abstract: Infrared spectral features have proved useful in the identification of threat objects. Dual-band focal-plane arrays (FPAs) have been developed in which each pixel consists of superimposed midwave and long-wave photodetectors [Dyer and Tidrow, Conference on Infrared Detectors and Focal Plane Arrays (SPIE, Bellingham, Wash., 1999), pp, 434-440]. Combining dual-band FPAs with imaging spectrometers capable of interband hyperspectral resolution greatly improves spatial target discrimination. The computed-tomography imaging spectrometer (CTIS) [Descour and Dereniak, Appl. Opt. 34, 4817-4826 (1995)] has proved effective in producing hyperspectral images in a single spectral region. Coupling the CTIS with a dual-band detector can produce two hyperspectral data cubes simultaneously. We describe the design of two-dimensional, surface-relief, computer-generated hologram dispersers that permit image information in these two bands simultaneously. © 2003 Optical Society of America.
• Dereniak, E. L., & Sampson, R. E. (2002). Introduction. Proceedings of SPIE - The International Society for Optical Engineering, 4721, ix-xvi.
• Kinder, B. A., Garcia, J. P., & Dereniak, E. (2002). Development of a 4-dimensional imaging spectrometer. Proceedings of SPIE - The International Society for Optical Engineering, 4816, 381-388.
  More info

  Abstract: The development of an imaging spectrometer to acquire 3 spatial dimensions and hyper-spectral information simultaneously is detailed. The spectrometer is based on the Computed Tomographic Imaging Spectrometer (CTIS) developed at the Optical Science Center and the Scannerless Laser Radar (LADAR) architecture developed at Sandia National Labs. The new 4-D imager, called the Spectral LADAR System (SLS), operates in the visible to near-infrared portion of the spectrum (600-900 nm). The system has 30 spectral intervals (10 nm bands), 1024 range samples, and approximately 80 × 80 spatial sampling. CTIS and LADAR are discussed, as well as preliminary results of the SLS.
• Locke, A. M., Sabatke, D. S., Dereniak, E. L., Descour, M. R., Garcia, J. P., Hamilton, T., & McMillan, R. W. (2002). Snapshot imaging spectropolarimeter. Proceedings of SPIE - The International Society for Optical Engineering, 4481, 64-72.
  More info

  Abstract: We present and analyze a technique for snapshot imaging spectropolarimetry. The technique involves the combination of channeled spectropolarimetry with computed tomography imaging spectrometry (CTIS). Channeled spectropolarimetry uses modulation to encode the spectral dependence of all four Stokes parameters in a single spectrum. CTIS is a snapshot imaging spectrometry method in which a computer-generated holographic disperser is employed to acquire dispersed images of the target scene, and both spatial and spectral information is reconstructed using the mathematics of computed tomography. The combination of these techniques provides the basis for a snapshot imaging complete Stokes spectropolarimeter which can be implemented with no moving parts. We present results of a simulation that we did using four input Stokes vectors that varied with wavelength. The reconstruction took into account dispersion from the retarders and that low frequency components will be missing in CTIS.
• Sabatke, D. S., Locke, A. M., Descour, M. R., Dereniak, E. L., Garcia, J. P., Hamilton, T. K., & McMillan, R. W. (2002). Analysis of channeled spectropolarimetry using singular value decomposition. Proceedings of SPIE - The International Society for Optical Engineering, 4481, 73-80.
  More info

  Abstract: Channeled spectropolarimetry is a technique for measuring the spectral dependence of the polarization state of light. Passive polarization optics are used to encode the spectral dependence of the four Stokes components Sk into a single irradiance spectrum. We treat the technique as a linear operator and compute its singular value decomposition (SVD) numerically. The resulting singular functions divide into three distinct groups representing S0, S1, and mixtures of S2 and S3. The corresponding singular values indicate that measurements of the latter two groups (using the system as modeled) will have signal-to-noise ratios reduced from that of So by factors of 0.6 and 0.4 respectively. The structure of the singular vectors is in agreement with a separate estimate of the system's resolution.
• Sabatke, D., Locke, A., Dereniak, E. L., Descour, M., Garcia, J., Hamilton, T., & McMillan, R. W. (2002). Snapshot imaging spectropolarimeter. Optical Engineering, 41(5), 1048-1054.
  More info

  Abstract: We present and analyze a technique for snapshot imaging spectropolarimetry. The technique involves the combination of channeled spectropolarimetry with computed tomography imaging spectrometry (CTIS). Channeled spectropolarimetry uses sideband modulation to encode the spectral dependence of all four Stokes parameters in a single spectrum. CTIS is a snapshot imaging spectrometry method in which a computer-generated holographic disperser is employed to acquire dispersed images of the target scene, and both spatial and spectral information is reconstructed using the mathematics of computed tomography. The combination of these techniques provides the basis for a snapshot imaging complete Stokes spectropolarimeter that can be implemented with no moving parts. We review design considerations for the spectropolarimeter and present preliminary simulation results.
• Scholl, J. F., Dereniak, E. L., Garcia, J. P., Tebow, C. P., & Garrood, D. J. (2002). Computational modeling of the imaging system matrix for the CTIS imaging spectrometer. Proceedings of SPIE - The International Society for Optical Engineering, 4816, 437-448.
  More info

  Abstract: Imaging systems such as the Computed Tomographic Imaging Spectrometer (CTIS) are modeled by the matrix equation g = Hf, which is the discretized form of the general imaging integral equation.. The matrix H describes the contribution to each element of the image g from each element of the hyperspectral object cube f. The vector g is the image of the spatial/spectral projections of f on a focal plane array (FPA). The matrix H is enormous, sparse and rectangular. It is extremely difficult to discretize the integral operator to obtain the matrix operator H. Normally H is constructed empirically from a series of monochromatic calibration images, which is a time consuming process. However we have been able to synthetically construct H by numerically modeling how the optical and diffractive elements in the CTIS project monochromatic point source data onto the FPA. We can evaluate a CTIS system by solving the imaging equation for f using both the empirical and synthetic H from some test data g. Comparison between the two results provides a means to evaluate and improve CTIS system calibration procedures noting that the synthetic system matrix H represents a baseline ideal system.
• Tawara, Y., Yamashita, K., Ogasaka, Y., Tamura, K., Haga, K., Okajima, T., Ichimaru, S., Takahashi, S., Gotou, A., Kitou, H., Fukuda, S., Tsusaka, Y., Kunieida, H., Tueller, J., Serlemitsos, P. J., Soong, Y., Chan, K. W., Owens, S. M., Barber, B., , Dereniak, E., et al. (2002). A hard X-ray telescope with multilayered supermirrors for balloon observations of cosmic X-ray sources. Advances in Space Research, 30(5), 1313-1319.
  More info

  Abstract: We have been developing a hard X-ray telescope utilizing multilayer supermirrors. The international focusing optics collaboration for μ-Crab sensitivity (InFOCμS) project is for balloon observations of cosmic hard X-ray sky with this new type of telescope. For the first flight scheduled in the next summer, we are preparing one full telescope with outermost diameter of 40 cm, focal length of 8 m, and energy band witgh of 20 - 40 keV as a first step. At the focal plane a CdZnTe imaging detector will be prepared. In this paper, the science objectives of this project, current status of the development of gondola, X-ray telescope and hard x-ray detector, and expected performance are described. © 2002 COSPAR. Published by Elsevier Science Ltd. All rights reserved.
• Tebow, C. P., Dereniak, E. L., Garcia, J. P., Garrood, D., Volin, C. E., Wilson, D. W., & McMillan, R. (2002). CGH disperser model for a tunable snapshot imaging spectrometer. Proceedings of SPIE - The International Society for Optical Engineering, 4647, 16-21.
  More info

  Abstract: We have constructed a computed-tomography imaging spectrometer (CTIS) that uses two crossed phase-only computer generated holograms (CGH) as the dispersing elements. This imaging spectrometer collects the multiplexed spatial and spectral data simultaneously and can be used for flash spectral imaging. Previous CTIS instruments require a single CGH dispersing element which were designed with the freedom of adjusting each element in the cell profile independently during the design process. The CGHs for this instrument are designed as identical crossed gratings to model the design parameters of a crossed 1D addressable liquid crystal spatial light modulator. Future integration of a liquid crystal spatial light modulator allows for the possibility of optical preprocessing of tomographic images. The CGH disperser pair has been designed to maintain nearly equal spectral diffraction efficiency among a 5 × 5 array of diffraction orders and to minimize the diffraction efficiency into higher orders. Reconstruction of the (x,y,λ) image cube from the raw, two-dimensional data is achieved by computed-tomography techniques.
• Volin, C. E., Descour, M. R., & Dereniak, E. L. (2002). Design of broadband-optimized computer-generated hologram dispersers for the computed-tomography imaging spectrometer. Proceedings of SPIE - The International Society for Optical Engineering, 4480, 377-387.
  More info

  Abstract: This paper describes an algorithm based on the singular-value decomposition that converges to a solution for a computer-generated-hologram disperser from a random-phase starting diffuser. In this paper, we report on the application of this algorithm to the design of two-dimensional, surface-relief CGH dispersers for use in the Computed-Tomography Imaging Spectrometer (CTIS). The designed CGH's produce desired diffraction images at five wavelengths through a 1:1.67 wavelength band. Performance results are presented for a demonstration CGH designed by the SVD algorithm and fabricated in GaAs for use in the mid-wave infrared CTIS.
• Volin, C. E., Garcia, J. P., Dereniak, E. L., Descour, M. R., Hamilton, T., & McMillan, R. (2002). Midwave-infrared snapshot imaging spectrometer. Proceedings of SPIE - The International Society for Optical Engineering, 4480, 355-366.
  More info

  Abstract: We report results from a demonstration of a midwave-infrared non-scanning, high speed imaging spectrometer capable of simultaneously recording spatial and spectral data from a rapidly varying target scene. High speed spectral imaging was demonstrated by collecting spectral and spatial snapshots of blackbody targets and combustion products. The instrument is based on computed tomography concepts and operates in a mid-wave infrared band of 3.0 to 5.0 μm. Raw images were recorded at a frame rate of 60 fps using a 512 × 512 InSb focal plane array. Reconstructed object cube estimates were sampled at 46×46×21 (x, y, λ) elements, or 0.1 μm spectral sampling. Reconstructions of several objects are presented.
• Volin, C. E., Garcia, J. P., Dereniak, E. L., Descour, M. R., Hamilton, T., & McMillan, R. (2001). Midwave-infrared snapshot imaging spectrometer. Applied Optics, 40(25), 4501-4506.
  More info

  PMID: 18360489;Abstract: We report results from a demonstration of a midwave-infrared, nonscanning, high-speed imaging spectrometer capable of simultaneously recording spatial and spectral data from a rapidly varying target scene. We demonstrated high-speed spectral imaging by collecting spectral and spatial snapshots of blackbody targets and combustion products. The instrument is based on computed tomography concepts and operates in a midwave-infrared band of 3.0-5.0 μm. We record raw images at a frame rate of 60 frames/s, using a 512 × 512 InSb focal-plane array. Reconstructed object cube estimates were sampled at 46 × 46 × 21 (x, y, λ) elements, or 0.1-μm spectral sampling. Reconstructions of several objects are presented. © 2001 Optical Society of America.
• Garcia, J. P., Volin, C. E., Sabatke, D. S., Descour, M. R., Dereniak, E. L., Hamilton, T. K., McMillan, R. W., & Sass, D. T. (2000). MWIR computed tomographic imaging spectrometer experiments. Proceedings of SPIE - The International Society for Optical Engineering, 4028, 79-87.
  More info

  Abstract: We report results of experimentation with a new, high-resolution MWIR non-scanning, snapshot imaging spectrometer capable of simultaneously recording spatial and spectral data from a rapidly varying target scene. The instrument is based on computed tomography concepts and operates in a mid-wave infrared band of 3.0 to 5.0 μm. High speed spectral imaging was demonstrated by collecting spectro-spatial snapshots of an artificial target in the lab. Raw images were recorded using a 512×512 InSb focal plane array in snapshot mode.
• Sabatke, D. S., Descour, M. R., Dereniak, E. L., Sweatt, W. C., Kemme, S. A., & Phipps, G. S. (2000). Optimization of retardance for a complete Stokes polarimeter. Optics Letters, 25(11), 802-804.
  More info

  PMID: 18064189;Abstract: We present two figures of merit based on singular value decomposition, which can be used to assess the noise immunity of a complete Stokes polarimeter. These are used to optimize a polarimeter featuring a rotatable retarder and a fixed polarizer. A retardance of 132° (approximately three-eighths wave) and retarder orientation angles of ±51.7° and ±15.1° are found to be optimal when four measurements are used. Use of this retardance affords a factor-of-1.5 improvement in signal-to-noise ratio over systems employing a quarter-wave plate. A geometric means of visualizing the optimization process is discussed, and the advantages of the use of additional measurements are investigated. No advantage of using retarder orientation angles spaced uniformly through 360° is found over repeated measurements made at the four retarder orientation angles. © 2000 Optical Society of America .
• Sabatke, D. S., Locke, A. M., Descour, M. R., Sweatt, W. C., Garcia, J. P., Dereniak, E. L., Kemme, S. A., & Phipps, G. S. (2000). Figures of merit for complete Stokes polarimeter optimization. Proceedings of SPIE - The International Society for Optical Engineering, 4133, 75-80.
  More info

  Abstract: Figures of merit for optimization of a complete Stokes polarimeter based on its measurement matrix are described which are not limited in their application to cases in which four measurements are used in the determination of a single Stokes vector. Singular value decomposition and probability theory are used to investigate the behavior and significance of these figures of merit. Their use to optimize a system consisting of a rotatable retarder and fixed polarizer indicates that a retardance of 132° (approximately three-eighths wave) and retarder orientation angles of ±51.7° and ±15.1° are favorable when four measurements are used. The performance of this system is demonstrated with experimental data.
• Schau, H. C., Descour, M. R., Dereniak, E. L., Spuhler, P. T., & Volin, C. E. (2000). System and design requirements in computed tomographic imaging spectroscopy. Proceedings of SPIE - The International Society for Optical Engineering, 4132, 25-31.
  More info

  Abstract: The advent of imaging spectroscopy has enabled optical sensors to be constructed that provide hyperspectral imagery on scales previously unattainable. Whereas multiband imagery on several spectral bands have been available for some time, the new generation of instruments is capable of providing imagery in hundreds or thousands of spectral bands. The price of increased measurement resolution is both greater system complexity, and, increased data processing burden. One of the new instrument designs for producing hyperspectral imagery is the Computed Tomographic Imaging Spectrometer (CTIS). This instrument relies on a computer generated holographic mask as a dispersing element with relatively conventional optical elements and arrays. Design philosophy is discussed relative to systems requirements for using hyperspectral imaging in missile and fire control systems. Issues of optical throughput, dispersion, mask complexity, and, producability are discussed. Results are shown for masks manufactured to operate in the visible and infrared regions. In concert with the design issues of the Computed Tomographic Imaging Spectrometer, the data processing and reduction is discussed both for remote sensing, and, typical missile and fire control applications. System tradeoff between algorithm complexity and mission is presented with regard to current algorithms and their implementation. Completed systems are presented and results from both first and second-generation instruments are displayed. Deviation of actual operation from expectations is discussed relative to plans for further development.
• Spuhler, P., Willer, M. R., Volin, C. E., Descour, M. R., & Dereniak, E. L. (2000). Software for simulation of a computed tomography imaging spectrometer using optical design software. Proceedings of SPIE - The International Society for Optical Engineering, 4132, 32-39.
  More info

  Abstract: Our Imaging Spectrometer Simulation Software known under the name Eikon should improve and speed up the design of a Computed Tomography Imaging Spectrometer (CTIS). Eikon uses existing raytracing software to simulate a virtual instrument. Eikon enables designers to virtually run through the design, calibration and data acquisition, saving significant cost and time when designing an instrument. We anticipate that Eikon simulations will improve future designs of CTIS by allowing engineers to explore more instrument options.
• Garcia, J. P., & Dereniak, E. L. (1999). Mixed-expectation image-reconstruction technique. Applied Optics, 38(17), 3745-3748.
  More info

  PMID: 18319981;Abstract: An image reconstruction technique has been developed which deals effectively with the noise processes present in the majority of imaging systems. These noise processes are photon noise and signal-independent system noise. The influence of the system noise appears as an empirically determined regularization parameter in the iterative MERT algorithm.
• Miles, B. H., Goodson, R. A., Dereniak, E. L., & Descour, M. R. (1999). Computed-tomography imaging spectropolarimeter (CTISP): instrument concept, calibration and results. Proceedings of SPIE - The International Society for Optical Engineering, 3754, 235-245.
  More info

  Abstract: The U.S. Army Engineer Research and Development Center (USAERDC) and the University of Arizona's Optical Sciences Center, have designed, constructed and developed a complete Stokes imaging spectropolarimeter. Referred to as the Computed Tomography Imaging Spectropolarimeter (CTISP), this technology characterizes an object's spectropolarimetric radiance over the 440 to 740 nm range using 20 nm spectral bins and subdividing the FOV with a 32 × 32 resolution for a total of 16×32×32=16384 voxels. The output of CTISP is an estimate of the Stokes vector for each voxel.
• Miles, B. H., Goodson, R. A., Dereniak, E. L., & Descour, M. R. (1999). Computed-tomography imaging spectropolarimeter (CTISP): instrument design, operation and results. Proceedings of SPIE - The International Society for Optical Engineering, 3753, 169-179.
  More info

  Abstract: The computed-tomography imaging spectropolarimeter (CTISP) is a complete Stokes imaging spectropolarimeter developed by researchers at the U.S. Army Engineer Research and Development Center (USAERDC) in collaboration with researchers at the University of Arizona's Optical Sciences Center. In comparison with other imaging spectropolarimeters, the advantage of CTISP is its ability to acquire full spatial, spectral and polarimetric data by scanning in the polarization domain alone.
• Shaw, J. A., Descour, M., Sabatke, D., Garcia, J., & Dereniak, E. (1999). Measurements of midwave and longwave infrared polarization from water. Proceedings of SPIE - The International Society for Optical Engineering, 3754, 118-125.
  More info

  Abstract: In the largely unpolarized natural infrared environment, water stands out as a notably polarized source. Water surfaces appear partially polarized in the infrared through both reflection and emission. This polarization can be significant in environmental and military remote sensing applications where the water is either the intended source or possibly a false target. In this paper we show and interpret measurements in midwave (approx. 4-5 μm) and longwave (approx. 10-11.5 μm) infrared bands. The midwave images show up to 7% s polarization (horizontal) in regions where warm objects reflect from the water. The longwave data also show s polarization in regions of sunlight, but elsewhere exhibit p polarization (vertical). Where the background is clear sky, the longwave signal is p polarized by up to 5% at large incidence angles.
• Volin, C. E., Garcia, J. P., Dereniak, E. L., Descour, M. R., Sass, D. T., & Simi, C. G. (1999). MWIR computed tomography imaging spectrometer: calibration and imaging experiments. Proceedings of SPIE - The International Society for Optical Engineering, 3753, 192-202.
  More info

  Abstract: We report results of experimentation with a MWIR non-scanning, high speed imaging spectrometer capable of simultaneously recording spatial and spectral data from a rapidly varying target scene. High speed spectral imaging was demonstrated by collecting spectral and spatial snapshots of filtered blackbodies, combustion products and a coffee cup. The instrument is based on computed tomography concepts and operates in a midwave infrared band of 3.0 to 4.6 μm. Raw images were recorded at a video frame rate of 30 fps using a 160 × 120 InSb focal plane array. Reconstructions of simple objects are presented.
• Volin, C. E., Garcia, J. P., Descour, M. R., Dereniak, E. L., Sass, D. T., & Simi, C. G. (1999). Demonstration of a MWIR high speed non-scanning imaging spectrometer. Proceedings of SPIE - The International Society for Optical Engineering, 3718, 480-489.
  More info

  Abstract: We report results from a demonstration of a MWIR non-scanning, high speed imaging spectrometer capable of simultaneously recording spatial and spectral data from a rapidly varying target scene. High speed spectral imaging was demonstrated by collecting spectral and spatial snapshots of filtered blackbodies and combustion products. The instrument is based on computed tomography concepts and operates in a mid-wave infrared band of 3.0 to 4.6 μm. Raw images were recorded at a video frame rate of 30 fps using a 160×120 InSb focal plane array. A reconstruction of a simple object is presented.
• Descour, M. R., Volin, C. E., Sabatke, D. S., Dereniak, E. L., Thome, K. J., Schumacher, A. B., Wilson, D. W., & Maker, P. D. (1998). Demonstration of a high speed non-scanning imaging spectrometer. Proceedings of SPIE - The International Society for Optical Engineering, 3379, 250-258.
  More info

  Abstract: We report results from a field demonstration of a non-scanning high-speed imaging spectrometer capable of simultaneously recording spatial and spectral information about a rapidly changing scene. High-speed spectral imaging was demonstrated by collecting spectral an spatial snapshots of a missile in flight. This instrument is based on computed-tomography concepts and operates in the visible (420 - 740 nm). Raw image data were recorded at video frame rate (30 fps) and an integration time of 2 msec. Reconstructions of the spatial and spectral scene information from the raw image data take considerably longer, on the order of 30 seconds. Comparisons of reconstructed spectra with spectra acquired by a non- imaging reference spectrometer have shown that extended-source spectra were reconstructed accurately. We present representative missile spectral-signature data and missile- tracking linear-classifier results from the missile firing. ©2003 Copyright SPIE - The International Society for Optical Engineering.
• Hubbs, J. E., Garcia, J. P., & Dereniak, E. L. (1998). Method to validate relative spectral response curves. Proceedings of SPIE - The International Society for Optical Engineering, 3379, 510-519.
  More info

  Abstract: A methodology for validating the measured relative spectral response function of infrared detectors is described. Typically, the spectral response of sister detectors, fabricated on the same wafer as the detectors for infrared focal plane arrays (IRFPA's), are characterized in lieu of measuring the spectral response of the actual IRFPA. It is then generally assumed that the spectral characteristics of the IRFPA detectors are equivalent to the spectral characteristics of the sister detectors. To validate this assumption, a measurement methodology has been developed to assess the accuracy the measured relative spectral response curves. This methodology is based on the premise that infrared detector's measured peak responsivity is independent of the spectral content of the irradiance at the detector. The peak wavelength responsivity of the infrared detector is measured as a function of spectral photon irradiance to evaluate the accuracy of the measured detector relative spectral response. If the measured peak responsivity of the infrared detector is independent of spectral irradiance, then the measured spectral response accurately represents the spectral characteristics of the infrared detector. However, if the peak responsivity varies with spectral irradiance, then the measured spectral response is in error. The shape of the peak responsivity versus spectral irradiance curve provides insight into the spectral region where the measured spectral response is in error. Sample relative spectral response data are presented along with analysis of the spectral response curves. ©2003 Copyright SPIE - The International Society for Optical Engineering.
• Volin, C. E., Descour, M. R., & Dereniak, E. L. (1998). Signal-to-noise ratio analysis of the computed tomography imaging spectrometer. Proceedings of SPIE - The International Society for Optical Engineering, 3438, 107-113.
  More info

  Abstract: We report results from a simple signal-to-noise analysis of the Computed Tomography Imaging Spectrometer (CTIS). The CTIS is non-scanning high-speed imaging spectrometer capable of simultaneously recording spatial and spectral information about dynamic events. This instrument is based on computed-tomography concepts and operates in the visible (420-710 nm with 10 nm sampling). The numerical estimate of the noise equivalent spectral radiance (NESR) for the CTIS is 1.6 nanowatts per centimeter squared per steradian per micrometer.
• Woolfenden, J. M., Barber, H. B., Barrett, H. H., Dereniak, E. L., Eskin, J. D., Marks, D. G., Matherson, K. J., Young, E. T., & Augustine, F. L. (1998). Modular 64×64 CdZnTe arrays with multiplexer readout for high-resolution nuclear medicine imaging. Materials Research Society Symposium - Proceedings, 487, 239-243.
  More info

  Abstract: We are developing modular arrays of CdZnTe radiation detectors for high-resolution nuclear medicine imaging. Each detector is delineated into a 64×64 array of pixels; the pixel pitch is 380 μm. Each pixel is connected to a corresponding pad on a multiplexer readout circuit. The imaging system is controlled by a personal computer. We obtained images of standard nuclear medicine phantoms in which the spatial resolution of approximately 1.5 mm was limited by the collimator that was used. Significant improvements in spatial resolution should be possible with different collimator designs. These results are promising for high-resolution nuclear medicine imaging.
• Yafuso, E. S., Sass, D. T., Dereniak, E. L., Hoffman, S., Gonzalez, R., Gonzalez, M., & Rettke, D. (1998). Multiple CCD stereo acquisition system for high-speed imaging. Proceedings of SPIE - The International Society for Optical Engineering, 3460, 36-45.
  More info

  Abstract: A high-speed digital three-dimensional (3-D) imaging system has been developed using multiple independent CCD cameras with sequentially triggered acquisition and individual field storage capability. The system described here utilizes sixteen independent cameras. A stereo alignment and triggering scheme arranges the cameras into two angularly separated banks of eight cameras each. By simultaneously triggering correlated stereo pairs, an eight-frame sequence of stereo images is captured. The delays can be individually adjusted to yield a greater number of acquired frames during more rapid segments of the event, and the individual integration periods may be adjusted to ensure adequate radiometric response while minimizing image blur. Representation of the data as a 3-D sequence introduces the issue of independent camera coordinate registration with the real scene. A discussion of the forward and inverse transform operator for the digital data is provided along with a description of the acquisition system.
• Barber, H. B., Apotovskyc, B. A., Augustine, F. L., Barrett, H. H., Dereniak, E. L., Doty, F. P., Eskin, J. D., Hamilton, W. J., Marks, D. G., Matherson, K. J., Venzon, J. E., Woolfenden, J. M., & Young, E. T. (1997). Semiconductor pixel detectors for gamma-ray imaging in nuclear medicine. Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 395(3), 421-428.
  More info

  Abstract: Semiconductor pixel detectors hold great promise for replacing scintillation cameras in nuclear medicine; improvements in spatial resolution, energy resolution and sensitivity should result. The current status of this subject is briefly reviewed. The fabrication of hybrid, 48 × 48 CdZnTe pixel arrays for use in gamma-ray imaging is described. Each detector array is indium-bump bonded to a Hughes 48 × 48 multiplexer chip; the design is similar to that of an infrared focal-plane array. The 48 × 48 CdZnTe array is shown to perform well as a gamma-ray imaging system with 125 μm spatial resolution (at 60 keV), equivalent to the pixel spacing. A correction technique for charge spreading between pixels is demonstrated. The implications of macroscopic crystal defects on array performance are briefly discussed.
• Barber, H. B., Barrett, H. H., Augustine, F. L., Hamilton, W. J., Apotovsky, B. A., Dereniak, E. L., Doty, F. P., Eskin, J. D., Garcia, J. P., Marks, D. G., Matherson, K. J., Woolfenden, J. M., & Young, E. T. (1997). Development of a 64 x 64 CdZnTe array and associated readout integrated circuit for use in nuclear medicine. Journal of Electronic Materials, 26(6), 765-772.
  More info

  Abstract: Previous work has shown that hybrid semiconductor detector arrays similar to those used in infrared focal-plane arrays are very attractive for use in nuclear medicine and other gamma-ray imaging applications. In this paper, we describe the development of a 64 x 64 readout multiplexer specifically for use in gamma-ray imaging; we also describe the construction of 64 x 64 CdZnTe hybrid detector arrays using the new readout. The readout and detector array are both about one inch square (2.5 cm x 2.5 cm) and have 380 μm pixel pitch. Some initial assembly problems have been resolved by stabilizing the hybrids with epoxy. Preliminary testing results are presented that verify that the 64 x 64 CdZnTe arrays perform as excellent imaging spectrometers.
• Barber, H. B., Dereniak, E., Eskin, J. D., Hilton, N. R., Marks, D. G., Matherson, K. J., Woolfenden, J. M., & Young, E. T. (1997). Use of CdZnTe pixel arrays with multiplexer readout to map detector crystal properties. IEEE Nuclear Science Symposium & Medical Imaging Conference, 1, 286-290.
  More info

  Abstract: We demonstrate the use of pixel arrays to map CdZnTe detector materials properties in situ. Our readout technique uses a multiplexer containing a gated integrator and is sensitive to DC currents. We have made extensive measurements of leakage current in one Cd.9Zn.1Te hybrid detector array that has size 25×25×1.5 mm3 and 380 μm pixel pitch. The pixel I-V curves are essentially ohmic and the leakage pattern is qualitatively similar at different temperatures. Histograms of pixel resistivity are relatively flat in the range 5-60 GΩcm. Pixel Arrhenius plots have slopes that differ with pixel resistivity.
• Descour, M. R., Volin, C. E., Dereniak, E. L., Gleeson, T. M., Hopkins, M. F., Wilson, D. W., & Maker, P. D. (1997). Demonstration of a computed-tomography imaging spectrometer using a computer-generated hologram disperser. Applied Optics, 36(16), 3694-3698.
  More info

  PMID: 18253394;Abstract: We have constructed a computed-tomography imaging spectrometer that uses a phase-only computer-generated hologram (CGH) array illuminator as the disperser. This imaging spectrometer collects multiplexed spatial and spectral data simultaneously and can be used for flash spectral imaging. The CGH disperser has been designed to maintain nearly equal spectral diffraction efficiency among a 5 × 5 array of diffraction orders and to minimize diffraction efficiency into higher orders. Reconstruction of the (x, y, λ) image cube from the raw, two-dimensional data is achieved by computed-tomography techniques. The 'reconstructed image and spectral-signature data compare favorably with measurements by other spectrometric methods. © 1997 Optical Society of America.
• Descour, M. R., Volin, C. E., Dereniak, E. L., Thome, K. J., Schumacher, A. B., Wilson, D. W., & Maker, P. D. (1997). Demonstration of a high-speed nonscanning imaging spectrometer. Optics Letters, 22(16), 1271-1273.
  More info

  PMID: 18185817;Abstract: We report results from a field demonstration of a nonscanning high-speed imaging spectrometer [computed-tomography imaging spectrometer (CTIS)] capable of simultaneously recording spatial and spectral information about a rapidly changing scene. High-speed spectral imaging was demonstrated by collection of spectral and spatial snapshots of a missile in flight. This instrument is based on computed-tomography concepts and operates in the visible spectrum (430-710 nm). Raw image data were recorded at video frame rate (30 frames/s) and an integration time of 2 ms. An iterative reconstruction of the spatial and spectral scene information from each raw image took 10 s. We present representative missile spectral signatures from the missile firing. The accuracy of the high-speed spectrometer is demonstrated by comparison of extended-source static-scene spectra acquired by a nonimaging reference spectrometer with spectra acquired by use of CTIS imaging of the same static scenes. © 1997 Optical Society of America.
• Matherson, K. J., Barber, H. B., Barrett, H. H., Eskin, J. D., Dereniak, E. L., Marks, D. G., Woolfenden, J. M., Young, E. T., & Augustine, F. L. (1997). Progress in the development of large-area modular 64×64 CdZnTe imaging arrays for nuclear medicine. IEEE Nuclear Science Symposium & Medical Imaging Conference, 1, 276-280.
  More info

  Abstract: Previous efforts by our group have demonstrated the potential of hybrid semiconductor detector arrays for use in gamma-ray imaging applications. In this paper, we describe progress in the development of a prototype imaging system consisting of a 64×64-pixel CdZnTe detector array mated to a multiplexer readout circuit that was custom designed for our nuclear medicine application. The detector array consists of a 0.15 cm thick slab of CdZnTe which has a 64×64 array of 380 um square pixel electrodes on one side produced by photolithography; the other side has a continuous electrode biased at -150 V. Electrical connections between the detector electrodes and corresponding multiplexer bump pads are made with indium bump bonds. Although the CdZnTe detector arrays characterized in this paper are room-temperature devices, a slight amount of cooling is necessary to reduce thermally generated dark current in the detectors. Initial tests show that this prototype imager functions well with more than 90% of its pixels operating. The device is an excellent imager; phantom images have a spatial resolution of 1.5 mm, limited by the collimator bore.
• Volin, C. E., Descour, M. R., & Dereniak, E. L. (1997). High-speed imaging spectrometry. Proceedings of SPIE - The International Society for Optical Engineering, 3118, 179-183.
  More info

  Abstract: We present results of a field demonstration of the computed tomography imaging spectrometer (CTIS). The CTIS was used to collect a sequence of image cubes of a missile in flight. This instrument is based on computed-tomography concepts and operates in the visible spectrum. Raw image data was recorded at video frame rate and an integration time of 2 msec. An iterative reconstruction of the spatial and spectral scene information from each raw image took 10 seconds. We present representative missile tracking-by- spectrum results. ©2004 Copyright SPIE - The International Society for Optical Engineering.
• Woolfenden, J. M., Barber, H. B., Barrett, H. H., Dereniak, E. L., Eskin, J. D., Marks, D. G., Matherson, K. J., Young, E. T., & Augustine, F. L. (1997). Modular 64×64 CdZnTe arrays with multiplexer readout for high-resolution nuclear medicine imaging. Materials Research Society Symposium - Proceedings, 484, 267-271.
  More info

  Abstract: We are developing modular arrays of CdZnTe radiation detectors for high-resolution nuclear medicine imaging. Each detector is delineated into a 64×64 array of pixels; the pixel pitch is 380 μm. Each pixel is connected to a corresponding pad on a multiplexer readout circuit. The imaging system is controlled by a personal computer. We obtained images of standard nuclear medicine phantoms in which the spatial resolution of approximately 1.5 mm was limited by the collimator that was used. Significant improvements in spatial resolution should be possible with different collimator designs. These results are promising for high-resolution nuclear medicine imaging.
• Barber, H. B., Marks, D. G., Apotovsky, B. A., Augustine, F. L., Barrett, H. H., Butler, J. F., Dereniak, E. L., Doty, F. P., Eskin, J. D., Hamilton, W. J., Matherson, K. J., Venzon, J. E., Woolfenden, J. M., & Young, E. T. (1996). Progress in developing focal-plane-multiplexer readout for large CdZnTe arrays for nuclear medicine applications. Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 380(1-2), 262-265.
  More info

  Abstract: We report on the construction and initial testing of a 48 × 48 CdZnTe array with 125 μm pixel spacing and multiplexer readout. Large portions of the array function well but there was a loss of pixels near one corner of the array due to non-interconnecting indium bumps. This problem is readily correctable. Excellent single-pixel spectra were obtained with a 99mTc source using an adjustment technique that accounts for energy deposited in neighboring pixels. A point-spread function (PSF) taken at 140 keV yielded a spatial resolution of 230 μm, much better than required for nuclear medicine applications. No problems were found that are not readily correctable or of much less significance for CdZnTe arrays having larger pixel spacing. We are now constructing 64 × 64 CdZnTe arrays with 380 μm pixel spacing for use in an ultra-high resolution brain SPECT imaging system.
• Curtis, C. H., Peyghambarian, N., Dereniak, E. L., & Frink, E. (1996). Tissue viability assessment via laser-based fluorescence monitor. Proceedings of SPIE - The International Society for Optical Engineering, 2676, 258-262.
  More info

  Abstract: A preliminary study of the degree to which recently introduced inhalation anesthetics influence the intracellular energetic metabolism of isolated perfused rat livers is undertaken via NADH fluorometry. During liver transplantation, anesthesiologists desire to maintain a high level of metabolic energy status in newly transplanted liver tissue. Ischemic storage of donor liver tissue prior to transplantation is known to inhibit mitochondrial electron transfer, which results in decreased levels of ATP and increased levels of NADH in the stored tissue. The ability of transplanted liver tissue to regenerate ATP at normal levels is desirable for early post- operative recovery of liver function. Previous studies have examined the differential effects inhalation anesthetics have on the energetic metabolism of tissue at the cellular level; the trend of such agents is to induce a dose-dependent increase in NADH fluorescence in accordance with their strengths as general anesthetics. The present study evaluates the differential effects exhibited by new inhalation anesthetics on the return of function of energetic metabolism in liver tissue. The third-harmonic (355 nm) output of a Nd:YAG laser is spatially filtered and used as the excitation source for surface fluorometric measurements of isolated buffer-perfused rat livers. Lastly, maximum fluorescence emission versus spot-size are measured.
• Marks, D. G., Barber, H. B., Barrett, H. H., Dereniak, E. L., Eskin, J. D., Matherson, K. J., Woolfenden, J. M., Young, E. T., Augustine, F. L., Hamilton, W. J., Venzon, J. E., Apotovsky, B. A., & Doty, F. P. (1996). A 48×48 CdZnTe array with multiplexer readout. IEEE Transactions on Nuclear Science, 43(3 PART 2), 1253-1259.
  More info

  Abstract: We report results of gamma-ray imaging and energy-resolution tests of a 48×48 CdZnTe array. Our detectors have 125 μm square pixel electrodes produced by photolithography and are indium-bump-bonded to a multiplexer readout circuit. Using a collimated beam of 140 keV gamma rays of 120 μm diameter centered on one pixel, we found that the majority of events produced significant charge deposition in nearby pixels. Charge and energy are transported out of the pixel by charge diffusion, photoelectron range, Compton scattering, and escape of K × rays. These effects also distort single-pixel spectra, although photopeaks are still discernible at 140 keV. When signals from neighboring pixels are summed together to correct for this charge spreading, an energy resolution of 10 keV is obtained at 140 keV. Corrections will be simpler and energy resolution should be better for the 380 μm pixels of the 64×64 CdZnTe arrays we are constructing for an ultra-high-resolution brain imager. © 1996 IEEE.
• Anton, R. C., Dereniak, E. L., & Garcia, J. P. (1995). Characteristics of uncooled indium antimonide photoconductors. Proceedings of SPIE - The International Society for Optical Engineering, 2552(2), 592-601.
  More info

  Abstract: Uncooled indium antimonide (InSb) photoconductors were studied to determine their primary noise source, spectral response, and maximum attainable spectral detectivity. The dominant noise component was determined by theoretically analyzing the background photon generation-recombination noise, thermal generation-recombination noise, and Johnson noise, using conditions of the experimental setup. It was shown that at room temperature (300 K) Johnson noise was predominant. Using this fact, an expression was derived for spectral detectivity which gave a value of 1.3 × 10 8 cm-Hz 1/2 /watt for a 25.2 k ω photoconductor and 5.9 × 10 8 cm-Hz 1/2 /watt for a 10 k ω photoconductor. The measurements from the experiment showed a peak wavelength response at 5 micrometer and a cutoff wavelength (50% of maximum) at 5.5 micrometer. The average peak spectral detectivity for the 25.2 k ω photoconductor was 1.17 × 10 8 cm-Hz 1/2 /watt and for the 10 k ω photoconductor, 4.48 × 10 8 cm- Hz 1/2 /watt. These results compared well with theory.
• Barber, H. B., Augustine, F. L., Barrett, H. H., Dereniak, E. L., Eskin, J. D., Marks, D. G., Matherson, K. J., Venzon, J. E., Woolfenden, J. M., & Young, E. T. (1995). High-resolution imaging using a 48×48 Ge array with multiplexer readout. IEEE Nuclear Science Symposium & Medical Imaging Conference, 1, 113-117.
  More info

  Abstract: We are developing an imaging technique for nuclear medicine that makes use of semiconductor arrays having a large number of separate pixels on a single slab that are read out by a monolithic integrated circuit called a multiplexer. The device is similar to a focal-plane array used for infrared imaging. Here we present results verifying the concept by using a Hughes 48×48 Ge PIN focal-plane array as a gamma-ray imaging system. The performance of this device as an imaging spectrometer was extraordinary, with a spatial resolution of 125 μm at 30 keV and an energy resolution of 2 keV FWHM (25-140 keV). The device performed well over a temperature range of 136-200 K. It is concluded that semiconductor detector arrays with multiplexer readout are a very attractive approach for a new generation of nuclear medicine imaging systems.
• Marks, D. G., Barber, H. B., Barrett, H. H., Dereniak, E. L., Eskin, J. D., Matherson, K. J., Woolfenden, J. M., Young, E. T., Augustine, F. L., Hamilton, W. J., Venzon, J. E., Apotovsky, B. A., & Doty, F. P. (1995). 48×48 CdZnTe array with multiplexer readout. IEEE Nuclear Science Symposium & Medical Imaging Conference, 2, 752-756.
  More info

  Abstract: We report results of gamma-ray imaging and energy-resolution tests of a 48×48 CdZnTe array. Our detectors have 125 μm square pixel electrodes produced by photolithography and are indium-bump-bonded to a multiplexer readout circuit. Using a collimated beam of 140 keV gamma rays of 120 μm diameter centered on one pixel, we found that the majority of events produced significant charge deposition in nearby pixels. Charge and energy are transported out of the pixel by charge diffusion, photoelectron range, Compton scattering, and escape of K x rays. These effects also distort single-pixel spectra, although photopeaks are still discernible at 140 keV. When signals from neighboring pixels are summed together to correct for this charge spreading, an energy resolution of 10 keV is obtained at 140 keV. Corrections will be simpler and energy resolution should be better for the 380 μm pixels of the 64×64 CdZnTe arrays we are constructing for an ultra-high-resolution brain imager.
• Barber, H. B., Augustine, F. L., Barrett, H. H., Dereniak, E. L., Matherson, K. J., Perry, D. L., Venzon, J. E., Woolfenden, J. M., & Young, E. T. (1994). Gamma ray response of a 48 × 48 Ge PIN photodiode array with multiplexer readout. IEEE Nuclear Science Symposium & Medical Imaging Conference, 1381-1385.
  More info

  Abstract: We are developing a new kind of gamma-ray imaging device that will have submillimeter spatial resolution and excellent energy resolution. The device is composed of a slab of semiconductor detector partitioned into an array of detector cells by photolithography with a monolithic circuit chip called a multiplexer (MUX) for readout. The application is for an ultra-high-resolution, modular SPECT system for functional brain imaging. In this paper, we describe preliminary results obtained with a Hughes 48 × 48 array of Ge PIN photodiodes with MUX readout originally developed as an infrared focal-plane-array detector. The device operates at cryogenic temperatures. We show that the device functions as an array of individual gamma-ray detectors and describe initial results for single pixel gamma-ray response, including linearity, quantum efficiency and energy resolution as a function of gamma-ray energy. A measured energy resolution of 1.5% FWHM is found for 99mTc 140 keV gamma rays. When used as an imaging detector, the spatial resolution of this device should be similar to the pixel spacing (125 μm).
• Barber, H. B., Augustine, F. L., Barrett, H. H., Dereniak, E. L., Matherson, K. L., Meyers, T. J., Perry, D. L., Venzon, J. E., Woolfenden, J. M., & Young, E. T. (1994). Semiconductor arrays with multiplexer readout for gamma-ray imaging: results for a 48 × 48 Ge array. Nuclear Inst. and Methods in Physics Research, A, 353(1-3), 361-365.
  More info

  Abstract: We are developing a new kind of gamma-ray imaging device that has sub-millimeter spatial resolution and excellent energy resolution. The device is composed of a slab of semiconductor detector partitioned into an array of detector cells by photolithography and connected to a monolithic circuit chip called a multiplexer (MUX) for readout. Our application is for an ultra-high-resolution SPECT system for functional brain imaging using an injected radiotracer. We report here on results obtained with a Hughes 48 × 48 Ge PIN-photodiode array with MUX readout, originally developed as an infrared focal-plane-array imaging sensor. The device functions as an array of individual gamma-ray detectors with minimal interpixel crosstalk. Linearity of energy response is excellent up to at least 140 keV. The array exhibits excellent energy resolution, ∼ 2 keV at ≤ 140 keV or 1.5% FWHM at 140 keV. The energy resolution is dominated by MUX readout noise and so should improve with MUX optimization for gamma-ray detection. The spatial resolution of the 48 × 48 Ge array is essentially the same as the pixel spacing, 125 μm. The quantum efficiency is limited by the thin Ge detector (0.25 mm), but this approach is readily applicable to thicker Ge detectors and room-temperature semiconductor detectors such as CdTe, HgI2 and CdZnTe. © 1994.
• Karkkainen, A., & Dereniak, E. L. (1994). Monte Carlo simulation of multiple quantum well and superlattice infrared photodetectors. Proceedings of SPIE - The International Society for Optical Engineering, 2225, 160-165.
  More info

  Abstract: A Monte Carlo program for simulating multiple quantum well and superlattice IR detectors is described. The model is quasi-2D and uses an effective mass approximation for the superlattice minibands. These approximations make it possible to run the program with the computing power of a workstation. The average velocity of the electrons is computed as function of the bias voltage.
• Perry, D. L., Hubbs, J. E., & Dereniak, E. L. (1994). Body-effect nonlinearity in infrared focal plane array multiplexers. IEEE Transactions on Electron Devices, 41(6), 1062-1063.
  More info

  Abstract: A hypothetical source-follower-per-detector multiplexer circuit is introduced. An analysis of its dc transfer function is presented, accounting for nonlinearity produced by the body-to-substrate bias. Calculated and measured transfer functions for an actual multiplexer are discussed. Effects of nonlinearity on nonuniformity-corrected infrared imaging are illustrated.
• Sankaran, V., Barrett, H. H., Krupinski, E. A., Dereniak, E. L., & Kennedy, H. V. (1994). Hotelling trace criterion as a model for the performance of an IR imaging system. Proceedings of SPIE - The International Society for Optical Engineering, 2269, 551-562.
  More info

  Abstract: The effect of fixed-pattern noise on the detection of subtle targets embedded in Gaussian white noise was investigated, comparing human detection performance with that of an ideal linear observer characterized by the Hotelling Trace Criterion (HTC). Five signal-to-noise ratios (SNR) were tested for the two conditions: with and without fixed-pattern noise, where both sets of images also contained Gaussian white noise. In this study, the SNR was calculated using the Gaussian white noise only; the additional fixed pattern noise was not figured into the SNR. Human detection performance did not differ significantly in the two conditions. In both conditions performance increased significantly with increases in SNR. The HTC figure of merit predicted accurately the experimental results for the fixed-pattern noise.
• Barber, H. B., Barrett, H. H., Dereniak, E. L., Hartsough, N. E., Perry, D. L., Roberts, P. C., Rogulski, M. M., Woolfenden, J. M., & Young, E. T. (1993). Design for a high-resolution SPECT brain imager using semiconductor detector arrays and multiplexer readout. Physica Medica, 9(2-3), 135-145.
• Barber, H. B., Barrett, H. H., Dereniak, E. L., Hartsough, N. E., Perry, D. L., Roberts, P. C., Rogulski, M. M., Woolfenden, J. M., & Young, E. T. (1993). Gamma-ray imager with multiplexer read-out for use in ultra-high resolution brain SPECT. IEEE Transactions on Nuclear Science, 40(4 pt 1), 1140-1144.
  More info

  Abstract: We are developing an ultra-high-resolution SPECT system for brain imaging. The system uses a multiple-pinhole aperture and many modular detectors, each composted of an array of semiconductor detectors read out by a monolithic integrated circuit called a multiplexer (MUX). The modular detectors, being passive integrators, can detect individual gamma rays with good energy resolution. They will also have sub-millimeter spatial resolution and high count-rate capability. In this paper we describe the basic concept of these detectors and review some of the design considerations for them. We also report some preliminary experiments that demonstrate that semiconductor detectors with multiplexer read-out act as gamma ray detectors.
• Descour, M. R., & Dereniak, E. L. (1993). Simulation of a retinal infrared focal plane array. Proceedings of SPIE - The International Society for Optical Engineering, 1762, 56-59.
  More info

  Abstract: The effect of coupling/shunting network for non-uniformity correction is examined on a sequence of two-dimensional images. The results indicate that a network incorporating a resistive grid and lateral inhibition performs well if only small responsivity variations are to be remedied. In the case of hot or dead pixels (zero information artifacts), network connections must exhibit some form of adaptive capability. Parallels with known features of the human visual system are presented and discussed, specifically wash-out of images stationary relative to the retina and the related filling-in of obscurations.
• Marasco, P. L., & Dereniak, E. L. (1993). Uncooled infrared sensor performance. Proceedings of SPIE - The International Society for Optical Engineering, 2020, 363-378.
  More info

  Abstract: The technology behind infrared focal plane arrays capable of operating at room temperature is discussed, emphasizing bolometric and pyroelectric devices. Theoretical limitations of thermal imagers operating at room temperature are explored and presented. The results of a survey cataloging the capabilities of currently available room temperature infrared focal plane arrays are presented. An example of how this technology could perform in a real world situation is presented from a theoretical point of view to show possible imaging system limitations due specifically to the room temperature focal plane.
• Perry, D. L., Descour, M. R., & Dereniak, E. L. (1993). Photoresponse nonlinearity in platinum silicide photodiodes. Proceedings of SPIE - The International Society for Optical Engineering, 2020, 491-502.
  More info

  Abstract: Sources of photoresponse nonlinearity in charge-integrating platinum silicide photodiodes are identified. Simulation results are presented, illustrating the magnitude of this nonlinearity as a function of wavelength, initial bias voltage, and stray capacitance. Additional simulation studies are discussed, revealing the impact of photoresponse nonlinearity on slope-and-offset-corrected thermal imaging. Application charts are provided, indicating the proper choice of calibration points for platinum silicide imaging systems.
• Yafuso, E. S., & Dereniak, E. L. (1993). Infrared portable calibration unit. Proceedings of SPIE - The International Society for Optical Engineering, 1762, 89-96.
  More info

  Abstract: Often the need arises for calibration of infrared systems in the environment of intended use, or field environment. The development of a field calibration platform for performance testing of infrared (IR) imaging and spectral analysis instrumentation is discussed. The calibration hardware is required to provide precise and traceable standards over a range of tests including minimum resolvable temperature difference (MRTD), noise equivalent temperature difference (NETD), minimum detectable temperature difference (MDTD), and modulation transfer function (MTF) for imaging systems, and known spectral content output for Fourier transform infrared radiometers (FTIR) and other spectral analysis instruments. The equipment package must consist of non-development components, and be portable, reliable, and repeatable under field conditions.
• Descour, M. R., & Dereniak, E. L. (1992). Functional aspects of the retina relating to infrared focal plane arrays. Proceedings of SPIE - The International Society for Optical Engineering, 1685, 110-117.
  More info

  Abstract: Research of vertebrate and invertebrate vision systems has revealed them to be remarkable assemblies of simple cells performing collectively various image processing and analysis tasks. Among these are counted edge enhancement, noise suppression, dynamic range compression, and motion and object orientation detection. These functions are achieved due to the massively parallel structure of these systems and appropriate non-linear inter-cell interactions, among them lateral inhibition. The high degree of connectivity existent in the vertebrate retina is currently beyond reach of integrated implementations; however, even its approximations applied to focal plane arrays can result in enhanced and more sophisticated performance. These approximations are discussed mathematically by means of methods developed for analysis of neural networks. A photoreceptor lateral interaction network, Grossberg's shunting neural network, and a novel modified version of the latter are compared in their effect on spatial nonuniformity noise and edge enhancement. These two qualities are of special interest in the case of infrared imaging. The modified shunting network combines an adaptive lateral signal spread amongst photodetectors with non-linear, multiplicative lateral inhibition. The first effect serves to reduce the effects of spatial noise, while the second, by its differentiating nature, removes low spatial frequencies and enhances high spatial frequency components inherent to the image.
• Flath, L. M., Dereniak, E. L., & Shepard, S. M. (1992). Development of a high-speed PtSi IRCCD camera system. Proceedings of SPIE - The International Society for Optical Engineering, 1685, 72-78.
  More info

  Abstract: This paper describes the construction of a high-speed PtSi infrared charge-coupled device (IRCCD) camera system funded by the U.S. Army Tank-Automotive Command (TACOM) for recording periodic events in the infrared. A brief discussion of PtSi infrared detection, and an analysis of expected signal contrast and NEΔT of the device are presented. Integration times to less than 1 ms and the ability to record frames based on an external trigger allow this setup to achieve effective frame rates of over 1000 frames per second. The use of a personal computer (PC) as a controller for CCD clocking and video capture results in a flexible camera system design.
• Garcia, J. P., Dereniak, E. L., & Shepard, S. M. (1992). High-speed infrared camera. Review of Scientific Instruments, 63(7), 3662-3665.
  More info

  Abstract: We have developed a staring-mode, high-speed infrared camera based on a RCA 160×244 PtSi Schottky-barrier charge-coupled device image sensor. The camera uses a unique method to achieve greater temporal resolution of rapidly varying thermal phenomena in the 3-5 μm band. Rather than increase the imager's frame rate, we decrease the image integration time while maintaining a frame rate that is compatible with standard RS-170 video. This technique allows us to display and record repetitive events that occur at frequencies up to 5 kHz with conventional video equipment. In this article we describe the theory and operation of this system.
• Hubbs, J. E., Neamen, D., & Dereniak, E. L. (1992). Computer simulation of a switched FET readout multiplexer. Proceedings of SPIE - The International Society for Optical Engineering, 1685, 118-129.
  More info

  Abstract: This paper describes the computer simulation of a hybrid infrared focal plane array (IRFPA) readout multiplexer. The device under study is a switched field effect transistor (SWIFET) readout multiplexer that utilizes a source follower per detector (SFD) unit cell amplifier. The objective of this study is to determine if the limiting component of the IRFPA nonlinearity is the infrared detector array or the readout multiplexer. This study was performed by developing a computer simulation within which the material, fabrication, and operational parameters of the SFD readout multiplexer could be varied. The computer simulation is able to predict experimental data from a SFD readout multiplexer thereby providing validation that the device models used in the computer simulation are correct. The most significant result determined by this study is that the nonlinearity associated with the SFD readout multiplexer is approximately an order of magnitude lower than the nonlinearity from a state-of-the-art PtSi infrared detector array. The nonlinearity in the SFD readout multiplexer is dominated by the body-effect in the source follower amplifiers that comprise the SFD readout multiplexer.
• Garcia, J. P., & Dereniak, E. L. (1991). Optical detectivity considerations for high-temperature superconducting thin-film detectors. Infrared Physics, 31(2), 179-182.
  More info

  Abstract: We show that a fundamental upper limit of specific detectivity (D*) exists for high-temperature superconducting thin-film quantum detectors biased at or above the critical current, Ic. This limit is a function of the inter-electrode length, the thickness of the film, and the critical current density rather than a function of the length-to-width aspect ratio. For typical film parameters, a maximum value of D* is 6.3 × 1010cm-Hz 1 2/W. © 1991.
• Graeve, T., Dereniak, E. L., & Lamonica Jr., J. A. (1991). An improved infrared technique for sorting pecans. Review of Scientific Instruments, 62(10), 2476-2479.
  More info

  Abstract: This paper presents the results of a study of pecan spectral reflectances. It describes an experiment for measuring the contrast between several components of raw pecan product to be sorted. An analysis of the experimental data reveals high contrast ratios in the infrared spectrum, suggesting a potential improvement in sorting efficiency when separating pecan meat from shells. It is believed that this technique has the potential to dramatically improve the efficiency of current sorting machinery, and to reduce the cost of processing pecans for the consumer market.
• Thiede, D. A., & Dereniak, E. L. (1990). High-T_c superconducting thin films as optical radiation detectors. Proceedings of SPIE - The International Society for Optical Engineering, 1287, 144-149.
  More info

  Abstract: High-temperature superconducting (HTS) thin films exhibit a change in thier electrical properties when exposed to optical radiation. The spectral characteristics of this electrical response were investigated by exposing HTS thin films to radiation from laser sources with wavelengths in the visible and infrared spectra. Experimental results are interpreted with regard to bolometric and/or nonequilibrium detection mechanisms.
• Hameroff, S., Schneiker, C., Voelker, M., Jackson, H. e., Dereniak, E., & McCuskey, R. (1988). Scanning tunneling microscopy (STM) applications to molecular electronics. IEEE/Engineering in Medicine and Biology Society Annual Conference, 10(pt2), 1009-1011.
  More info

  Abstract: The authors describe their efforts to use STM (scanning tunneling microscopy) to image and manipulate biomolecular structures such as collagen. They present design considerations for a precursor to the nanotechnology workstation: a two-tip STM. The authors also note some future possibilities for scanning tunneling engineering and for nanoscale tunnel sensors and devices.
• Voelker, M. A., Hameroff, S. R., He, J. D., Dereniak, E. L., McCuskey, R. S., Schneiker, C. W., Chvapil, T. A., Bell, L. S., & Weiss, L. B. (1988). STM imaging of molecular collagen and phospholipid membranes. Journal of Microscopy, 152(2), 557-566.
  More info

  PMID: 3253448;
• Mooney, J. M., & Dereniak, E. L. (1987). COMPARISON OF THE PERFORMANCE LIMIT OF SCHOTTKY-BARRIER AND STANDARD INFRARED FOCAL PLANE ARRAYS.. Optical Engineering, 26(3), 223-227.
  More info

  Abstract: D is analyzed as a figure of merit for focal plane arrays. Spatial noise (nonuniformity) is incorporated into the signal-to-noise ratio, and its effects are examined for a Schottky barrier and for a standard photon detector (constant quantum efficiency) over the 3 to 5 mu m spectral band. The requirements for radiometric source uniformities are presented to show their effect in reduction of fixed-pattern noise. Because of the D inadequacies presented, the preferred figure of merit is the signal-to-noise ratio.
• Boreman, G., & Dereniak, E. L. (1986). METHOD FOR MEASURING MODULATION TRANSFER FUNCTION OF CHARGE-COUPLED DEVICES USING LASER SPECKLE.. Optical Engineering, 25(1), 148-150.
  More info

  Abstract: A new method has been developed to measure the modulation transfer function (MTF) of an array out to the Nyquist frequency without high quality optical or mechanical components, without precision alignment, and with only one moving part. Test results for an infrared staring array of PtSi Schottky barrier construction show that this technique is a viable MTF measurement approach in the 3 to 5 mu m spectral region.
• Walter, G. A., & Dereniak, E. L. (1986). PHOTODETECTORS FOR FOCAL PLANE ARRAYS. PART 1: EXTRINSIC SILICON.. Laser Focus (Littleton, Massachusetts), 22(3), 7p between p 108 and 118.
  More info

  Abstract: This article discusses IR photodetectors for radiation between 8 and 14 mu m, and to a lesser extent, between 3 and 5 mu m. IR detectors with applications in focal plane arrays include extrinsic silicon, mercury cadmium telluride, and some novel materials and structures. Part 1 of this article analyzes extrinsic silicon, and reviews its performance, fabrication, and use in various array architectures.
• Walter, G. A., & Dereniak, E. L. (1986). PHOTODETECTORS FOR FOCAL PLANE ARRAYS. PART 2: HgCdTe.. Laser Focus (Littleton, Massachusetts), 22(4), 8p between p 86 and 96.
  More info

  Abstract: This two-part series discusses the practical IR detectors for use in focal plane arrays. Part I, which appeared in the March Laser Focus, covered extrinsic silicon detectors and included discussion of that material's dopant uniformity and its compensation of contaminating impurities. It was concluded that Si:X has several advantages, including material maturity, high impedance, match in thermal expansion coefficient with a Si MUX, possibly superior low background performance, and mechanical strength because of detector thickness. This issue, Part II, discusses the performance of HgCdTe as an array detector. Researchers working with this material system have developed both photoconductive and photovoltaic devices, with photovoltaic showing the greatest promise and receiving the most attention. The discussion includes growth, performance, and detector array fabrication.
• Vinson, A. L., & Dereniak, E. L. (1985). MEASUREMENT OF 1/F NOISE OF HgCdTe, PtSi, AND InSb.. Proceedings of SPIE - The International Society for Optical Engineering, 572, 109-114.
  More info

  Abstract: In the application of photovoltaic diode arrays in imaging systems which use standard television frame rates, flicker noise is often observed at the output. The magnitude of the noise seems to be device dependent. The objectives of this research are to compare the 1/f noise spectra of various photovoltaic detectors used in the 3-5 mu m spectral region and isolate the dominating current source causing 1/f noise. This paper describes a preliminary investigation of 1/f noise in three infrared detector materials used in the MWIR (3-5 mu m). Noise measurements of HgCdTe, PtSi, and InSb detectors were conducted and the results are presented. The various noise sources are discussed.
• Boreman, G., & Dereniak, E. L. (1984). METHOD FOR MEASURING MODULATION TRANSFER FUNCTION OF CCD's USING LASER SPECKLE.. Proceedings of SPIE - The International Society for Optical Engineering, 501, 174-178.
  More info

  Abstract: A new method has been developed to measure the modulation transfer function (MTF) of an array out to the Nyquist frequency without high-quality optical or mechanical components, without precision alignment, and with only one moving part. Test results for an infrared staring array of PtSi Schottky barrier construction show that this technique is a viable MTF measurement approach in the 3 to 5 mu m spectral regions.
• Dereniak, E. L., Britt, J. P., Fowler, A. M., Joyce, R. R., Boreman, G., & Ewing, W. S. (1984). EVALUATION OF A PtSi SCHOTTKY INFRARED CCD FOR ASTRONOMY.. Applied Optics, 23(6), 889-895.
  More info

  Abstract: This study presents the results of a preliminary evaluation of a platinum silicide (PtSi) Schottky CCD as an imaging array for astronomical applications. The work was done in the near-infrared (1. 2 mu m less than lambda less than 2. 5 mu m) spectral regime, where there is presently a lack of commercially available panoramic arrays with acceptable performance. During an initial test run, the array detected a star of magnitude 3. 5 using an integration time of 128 msec. Proper optimization of the readout electronics, cryostat configuration, and matching of the telescope image scale to the pixel size could allow detection of a source approximately 100 times fainter in a 1-sec intergration time. A discussion is presented of the array architecture, measurement and signal processing techniques, and the observatory and laboratory evaluation tests.
• Dereniak, E. L., Roehrig, H., Salcido, M. M., Pommerrenig, D. H., Simms, R. A., Abraham, J. M., & Bredthauer, R. A. (1984). X-RAY HYBRID IMAGE INTENSIFIER WITH ELECTRICAL READOUT.. Proceedings of SPIE - The International Society for Optical Engineering, 501, 98-102.
  More info

  Abstract: Charge-coupled-device (CCD) arrays are combined with an image intensifier tube to create an x-ray imager. The x-ray image intensifier tube design uses a proximity focus arrangement with four 32 multiplied by 32 CCD arrays.
• Prettyjohns, K. N., & Dereniak, E. L. (1984). SOFTWARE FOR A UNIVERSAL CCD TEST FACILITY.. Proceedings of SPIE - The International Society for Optical Engineering, 501, 213-218.
  More info

  Abstract: A computer-controlled CCD test facility has been developed based upon the Hewlett Packard HP9836C desktop computer. This paper describes the system and its operating software. Details of the control of the CCD operating parameters and some test procedures are described.
• Ewing, W. S., Capps, R. W., & Dereniak, E. L. (1983). APPLICATIONS OF AN INFRARED CHARGE-COUPLED DEVICE SCHOTTKY DIODE ARRAY IN ASTRONOMICAL INSTRUMENTATION.. Optical Engineering, 22(3), 334-338.
  More info

  Abstract: An infrared staring mode imaging sensor was designed to operate with the NASA Infrared Telescope Facility (IRTF) at Mauna Kea, Hawaii. The sensor has a 0. 5 arc sec spatial resolution over a 10 arc sec field and is matched to the f/35 focal ratio of the telescope. The focal plane device is a back-side illuminated Schottky infrared charge-coupled device (IRCCD) mosaic with a photoresponse from 1 to 5 mu m. Astronomical observations are reported at 2. 2 mu m where the IRCCD quantum efficiency is greater than values normally reported for the 3. 4 to 4. 2 mu m thermal imaging band.
• Prettyjohns, K., DeVore, S., Dereniak, E., & Wyant, J. (1983). DESIGN AND OPERATION OF A REAL TIME INTERFEROMETER WORKING AT 3. 8 mu m.. Proceedings of SPIE - The International Society for Optical Engineering, 429, 142-147.
  More info

  Abstract: A digital heterodyne interferometer has been designed and constructed to operate at a wavelength of 3. 8 mu m. The instrument is intended for use in measuring wavefront figure error due to thickness variations in dielectric coatings applied to infrared optics. A 32 multiplied by 64 element PtSi infrared CCD detector array was used together with digital processing and graphics display on a desktop microcomputer. Preliminary results have shown a wavefront measurement repeatability of less than lambda /50.
• Amlin, D. W., & Dereniak, E. L. (1982). CHARACTERIZATION OF FIBERS FOR 10. 6 mu m TRANSMITTANCE.. Proceedings of SPIE - The International Society for Optical Engineering, 320, 106-108.
• Dereniak, E. L., Bredthauer, R. A., Hicks, E. M., Vicars, J. E., & Florence, R. A. (1982). MICROPROCESSOR-BASED CHARGE COUPLED DEVICE (CCD) TEST CONSOLE.. Optical Engineering, 21(5), 942-944.
  More info

  Abstract: A relatively inexpensive microprocessor-based charge coupled device (CCD) test console system has been built for the evaluation of CCD imaging arrays. The system consists of a commercially available microprocessor system that controls test equipment used in CCD array testing. The test console is capable of measuring charge transfer efficiency (CTE) and noise for any size CCD array. The data collection is done by the computer interface to minimize operator error. The system is interactively controlled by an operator who runs the operation of the system from the keyboard of the microprocessor.
• Dereniak, E. L., Brod, L. G., & Hubbs, J. E. (1982). BIDIRECTIONAL TRANSMITTANCE DISTRIBUTION FUNCTION MEASUREMENTS ON ZnSe.. Applied Optics, 21(24), 4421-4425.
  More info

  Abstract: The bidirectional transmittance distribution function (BTDF) is used to evaluate the scattering properties of chemically vapor-deposited (CVD) zinc selenide (ZnSe). Conceptually, the BTDF is a logical extension of the bidirectional reflectance distribution function (BRDF) relation. A working equation for BTDF based on the practical limitations of the instrumentation has been developed. The practical limitations inherent in making BTDF measurements are the finite detector size, the two scattering surfaces of the sample, and the linear radiometric responses of the detector. The instrumentation used to measure BTDF and the data collection procedure are described. Plots of BTDF vs angle from the sample normal are presented for CVD ZnSe at room temperature. The plots are for three thicknesses of ZnSe (6, 19, and 25 mm) at three laser wavelengths (0. 6328, 3. 39 and 10. 6 mu m).
• Ewing, W. S., Shepherd, F. D., Capps, R. W., & Dereniak, E. L. (1982). APPLICATIONS OF AN INFRARED CHARGE-COUPLED DEVICE SCHOTTKY DIODE ARRAY IN ASTRONOMICAL INSTRUMENTATION.. Proceedings of SPIE - The International Society for Optical Engineering, 331, 156-163.
• Bartell, F. O., Dereniak, E. L., & Wolfe, W. L. (1981). THEORY AND MEASUREMENT OF BIDIRECTIONAL REFLECTANCE DISTRIBUTION FUNCTION (BRDF) AND BIDIRECTIONAL TRANSMITTANCE DISTRIBUTION FUNCTION (BTDF).. Proceedings of the Society of Photo-Optical Instrumentation Engineers, 257, 154-160.
  More info

  Abstract: The concepts of BRDF (Bidirectional Reflectance Distribution Function) and BTDF (Bidirectional Transmittance Distribution Function) are defined and discussed as being the ratios of differential outputs of radiance divided by differential inputs of irradiance. Appropriate measurement arrangements and procedures are presented, and the problems are described that are involved in going from the differentials of theory to the finite quantities of measurement. Finally appropriate data reduction schemes are given for determining BRDF and BTDF from these measurements.
• Brod, L., & Dereniak, E. L. (1981). SCATTERING FROM ZnSe USED AS AN INFRARED WINDOW.. Proceedings of the Society of Photo-Optical Instrumentation Engineers, 253, 203-210.
  More info

  Abstract: The scattering of infrared radiation from ZnSe was measured for three laser wavelengths (0. 6328, 3. 39, and 10. 6 mu m) and three material thicknesses (6 mm, 19 mm, and 25 mm). The data from these experiments are shown and a scattering model for this material is presented.
• Crowe, D. G., Cohen, D. K., & Dereniak, E. L. (1981). DERIVATION OF THE EFFECT OF ATMOSPHERIC AND AEROSOL EMISSIONS ON IR IMAGING DEVICE PERFORMANCE.. Applied Optics, 20(22), 3958-3960.
  More info

  Abstract: The authors have previously called attention to the importance of atmospheric and aerosol emission in IR imaging device performance. The present paper obtains a more precise and general result than the empirically derived expression in the earlier paper. The same general conclusion, that atmospheric and aerosol emissions are an important factor in IR imaging performance, is supported, assuming that the system is photon noise-limited.
• Dereniak, E. L., Stuhlinger, T. W., & Bartell, F. O. (1981). BIDIRECTIONAL REFLECTANCE DISTRIBUTION FUNCTION OF GOLD-PLATED SANDPAPER.. Proceedings of the Society of Photo-Optical Instrumentation Engineers, 257, 184-191.
  More info

  Abstract: The use of gold-plated sandpaper was investigated as a standard Lambertian reference reflector. Various grit sizes from 3 mu m to 440 mu m and material types (i. e. , silicon carbide or aluminum oxide, were studied. The different gold-plated sandpaper grit sizes were measured in the same way using three laser wavelengths (0. 6328 mu m, 3. 39 mu m, and 10. 6 mu m) at five angles of incidence of the source (0 degree , 10 degree , 20 degree , 30 degree c, and 60 degree ). The best choice of sandpaper grit size was compared to other commonly used reflectors such as magnesium oxide, halon, sintered bronze, and flowers of sulfur. An attempt was made to correlate surface roughness (size of grit) to the degree of approximation to a good Lambertian reflector, but it was found that grit size is not as important as filling factor, or density of particles, over a given area.
• Stuhlinger, T. W., Dereniak, E. L., & Bartell, F. O. (1981). BIDIRECTIONAL REFLECTANCE DISTRIBUTION FUNCTION OF GOLD-PLATED SANDPAPER.. Applied Optics, 20(15), 2648-2655.
  More info

  Abstract: Gold-plated sandpaper was studied for use as a Lambertian standard reference reflector for the IR spectrum. Various grit sizes from 3 to 400 mu equals m and material types (i. e. , silicon carbide and aluminum oxide) were studied. The different gold-plated sandpaper grit sizes were measured in the same way using three laser wavelengths at five angles of incidence of the source. An attempt was made to correlate surface roughness (size of grit) to the degree of approximation to a good Lambertian reflector, but it was found that grit size is not as important as the filling factor, or density of particles, over a given area. It was found that fairly good approximations to Lambertian behavior result when the angle of incidence is small but not when the angle of incidence is as large as 30 degree .
• Crowe, D. G., Cohen, D. K., & Dereniak, E. L. (1980). INFRARED PROPAGATION AND PERFORMANCE MODELING AT THE ELECTRO-OPTICAL TEST FACILITY.. Applied Optics, 19(12), 1953-1958.
  More info

  Abstract: Fog spectral transmission data generated in the Electro-Optical Test Facility and propagation models used by the authors are presented. Preliminary results of a modeling effort are reported that support the following conclusions: (1) atmosphere emission is a major factor in IR system performance despite the fact it is commonly omitted; (2) the 3. 5-4. 1 mu m interval offers superior performance to the 3-5 band at both relatively short and long ranges; and (3) the longer wavelength 9. 5-11. 5 mu m band is superior to either the 3-5 or 3. 5-4. 1 bands in the presence of fog.
• Dereniak, E. L., Hicks, E. M., Speer, J. J., & McDevitt, A. M. (1980). MICROPROCESSOR-CONTROLLED PHOTODETECTOR TEST CONSOLE.. Proceedings of the Society of Photo-Optical Instrumentation Engineers, 230, 97-113.
  More info

  Abstract: This paper discusses the use of a microprocessor-based test station to characterize infrared photoconductors. The station is programmed in the BASIC language and has 32K of memory. It determines the optimum operating conditions for a photoconductor, and also the detector's figures of merit on an absolute basis. The program is used for large array device testing and also for screening elements of many detectors in order to select a small number of high performance devices.
• Dereniak, E. L., Palmer, J. M., & Roehrig, H. (1980). OPTICAL RADIATION DETECTOR LABORATORY.. IEEE Transactions on Education, E-23(2), 66-69.
  More info

  Abstract: This paper describes a graduate-level optical radiation detector laboratory course taught at the Optical Sciences Center of the University of Arizona, Tucson, AZ. It highlights the experiments performed with various types of detectors, including photovoltaic, photoconductive, thermal, and photoemissive detectors and discusses the figures of merit that are measured by the students.
• Dereniak, E. L., Joyce, R. R., & Capps, R. W. (1977). LOW-NOISE PREAMPLIFIER FOR PHOTOCONDUCTIVE DETECTORS.. Review of Scientific Instruments, 48(4), 392-394.
  More info

  Abstract: High-performance infrared detectors such as arsenic-doped silicon (Si:As) and bismuth-doped silicon (Si:Bi) have been successfully used in ground-based infrared telescope systems in the 2-20 mu m range. Optimum performance (BLIP operation) of these detectors is obtained by using a special feedback amplifier. The advantages of such a system are discussed in conjuction with preliminary data on Si:As and Si:Bi detectors.
• Gillett, F. C., Dereniak, E. L., & Joyce, R. R. (1977). DETECTORS FOR INFRARED ASTRONOMY.. Optical Engineering, 16(6), 544-550.
  More info

  Abstract: Many of the recent advances in infrared astronomy have been the result of improved performance of existing infrared detectors or the introduction of new detectors. This paper includes an examination of the background photon fluxes encountered in infrared astronomy and the effect on detector performance of the fluctuation in this background. The operating characteristics and limitations of thermal and photon detectors currently utilized in infrared astronomy are discussed.
• Dereniak, E. L., & Brown, F. (1975). NETD calculations using the radiation slide rule. Infrared Physics, 15(3), 243-248.
• Dereniak, E. L., & Brown, F. (1975). Pyroelectric detector evaluation. Infrared Physics, 15(1), 39-43.
• Dereniak, E. L. (1973). APPLICATION OF A SYNTHETIC APERTURE OPTICAL SYSTEM TO INFRARED IMAGING.. Applied Optics, 12(3), 487-492.
  More info

  Abstract: The application of a synthetic aperture system (SAS) for the formation of infrared images is discussed. The SAS of primary interest is a hexagonal array of six circular apertures. In imfrared images, in the 8-14- mu m region, conventional detectors are too large to sample the image without aliasing the spatial spectrum. The unusual transfer function characteristics of the SAS are shown to obtain larger sampling distances than those required by the Whittaker-Shannon sampling theory. One possible detector array that will correctly sample the image is presented.