An overview of the DRS HDVIP architecture for realization of large-area infrared focal plane arrays (IRFPAs) is given. Improvements needed to meet more stringent application requirements are discussed and modeled. Both theoretical and experimental data are presented.

An overview on DRS' approaches towards realization of HgCdTe photonic infrared detectors based on DRS's proven HDVIP technology is given. The first approach involves the use of a silicon microlens array attached to the detector array, and the second reduction of dark currents in each detector itself. Recent progress is presented.

A Pulse Coupled Neural Network (PCNN) has been developed in order to segment image data to reduce the amount of downstream processing. This paper discusses the results of applying the PCNN algorithm to data generated by various sensor platforms. The PCNN algorithm was applied to data generated by a Long Wave Infrared Imaging Polarimeter. The PCNN correctly identified the concealed vehicles and the disturbed earth and rejected 96% of the remaining pixels because they had no information content. Next, the results of applying the PCNN algorithm to noisy infrared seeker data are presented. The PCNN correctly idnetified the target even though the background was quite noisy. Finally, the PCNN algorith was applied to images containing solar glint. It correctly passed only 3& of the pixels to the downstream target/glint decision algorithm. To obtain maximum data throughput, the PCNN can be implemented in hardware.

Recent developments at Rockwell Scientific in the advancement of infrared and visible Focal Plane Array (FPA) technologies is presented. The technologies reviewed are hybrid silicon PIN visible, substrate-removed IR/VIS, MCT on silicon, 2-color, large format NIR FPAs, system-on-a-chip technology, and mosaic packaging. The basic aspects of each technology is described followed by a review of present performance achieved and the path for further development.

Future infrared space missions will undoubtedly employ passively cooled focal plane arrays (T ~ 30K), as well as passively cooled telescopes. Most long-wave detector arrays (e.g. Si:As IBC) require cooling to temperatures of ~ 6-8K. We have been working with Rockwell Scientific Company to produce <= 10 micron cutoff HgCdTe detector arrays that, at temperatures of ~30K, exhibit sufficiently low dark current and sufficiently high detective quantum efficiency, as well as high uniformity in these parameters, to be interesting for astronomy. Our goal is to achieve dark current below the target value of ~ 30 e-/s/pixel with at least 60mV of actual reverse bias across the diodes at T ~ 30K. To this end, Rockwell Scientific Company has delivered three 10 micron cutoff HgCdTe low dark current detector arrays with small capacitance diodes for characterization in Rochester. The most recent presentation showed the remarkable preliminary performance of the first of these devices. We present further results on the first device along with results on the subsequent two deliveries.

This paper details significant improvements in current-voltage (I-V) modeling capabilities using an automated iterative non-linear fitting program. The properties of a particular infrared (IR) detector's I-V curve are dependent upon the current limiting mechanisms in the device which depend upon the temperature, applied bias, and cutoff wavelength or detector bandgap. This model includes ideal diode diffusion, generation-recombination, band-to-band tunneling, trap-assisted tunneling, shunt resistance, and avalanche breakdown as potential current limiting mechanisms in an IR detector diode. The modeling presented herein allows one to easily distinguish, and more importantly to quantitatively compare, the amount of influence each current limiting mechanism has on various detector's I-V characteristics. Modeling of the trap-assisted-tunneling mechanism leads to an estimate of the density of occupied trap states at a given temperature. This model is now routinely applied to Raytheon Vision Systems’ test structures to better understand detector current limitations.

BAE Systems is the leading producer of uncooled microbolometer based thermal imaging engines in the world. Initial investments to develop and produce uncooled infrared (IR) technology were primarily driven by military applications, but it was the commercial market with the potential for large product volumes which provided BAE Systems with the business model required for investment in uncooled IR technology. This paper reviews the heritage of BAE Systems technology and current products and is an example of the success of a Dual-Use technology area which DARPA invested in during the 1990s.

CMC Electronics Cincinnati (CMC) is now in production on 1Kx1K InSb focal plane arrays (FPAs), and continuing efforts on a third production run of 2Kx2K large format IR FPAs. These FPAs are based on our unique reticulated InSb architecture that has been shown to be inherently scalable across format size while maintaining performance properties. Performance in the 10mk to 15mk NETD range will be shown. The design and fabrication of these advanced FPAs has challenged the state of the art in fabrication processing, testing, and qualification of both InSb detectors and silicon ROICs. Program sponsored manufacturing improvement activities, as well as CMC internal R&D, continue to improve both the yields and the performance characteristics of these large arrays. The latest yield, operability, and performance data will be shown. Data will be drawn from a population of approximately 30 2Kx2K FPAs and 50 1Kx1K FPAs. A novel approach to rapid thermal cycling FPAs will we described and recent developments that enable the fabrication of reticulated, smaller pixel pitch devices and practical Ultra Large Format FPAs with additional capability and features will be discussed.

InGaAs/InGaP quantum-dots have been grown by low-pressure metalorganic chemical vapor deposition technique on GaAs substrate. The important growth parameters, such as growth temperature, V/III ratio, etc, have been optimized. A 10-stack quantum-dot infrared photodetector based on these InGaAs dots showed a detectivity of 3.6x10¹⁰ cmHz^1/2/W at 95K. The peak photoresponse was 4.7 μm with a cutoff at 5.2μm. A 256x256 middle-wavelength infrared focal plane array based on our quantum-dot detectors was fabricated via dry etching technique. The detector array was bonded to a silicon readout integrated circuit via flip chip bonding with indium bumps. A noise equivalent temperature difference of 509 mK was achieved for this array at 120K. With the goal of improving array uniformity, exploratory work into nanopillar structure IR detectors was also performed. Experimental methods and characterization results are presented here.

A common technique in the design of a spectral imaging system is the use of a prism as the dispersive element to disperse the colors onto the focal plane. The imaging system can serve as a spectrometer for point events with minimal computational load because the spectral data from a point event is spread directly on the FPA. The fidelity of the spectrum depends in this case on several factors, including the relative orientation between prism and FPA; the relative sizes of pixel pitch and sensor point spread function; and algorithms to determine spectral calibration and content. In this paper, we elucidate some methods for extracting the spectral data from the two-dimensional array of measurements, including the use of radial basis functions, and demonstrate the procedure with data from a spectral imager.

The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) will launch in 2005 on the Mars Reconnaissance Orbiter (MRO) mission, with its primary science objective to characterize sites with aqueous mineral deposits hyperspectrally at high spatial resolution. CRISM’s two Offner relay spectrometers share a single entrance slit with a dichroic beamsplitter. The IR focal plane contains a 640 (spatial) x 480 (spectral) HgCdTe FPA with a 980 nm to 3960 nm spectral bandpass. It is cooled to 110 K to minimize dark current, and coupled to a 28 mm long cold shield to minimize thermal background. The spectrometer housing is cooled to -90 C for the same reason. A three-zone IR filter consisting of two broadband filters and a linear variable filter overlays the IR focal plane, eliminating multiple grating orders and providing additional attenuation of the thermal background. The visible focal plane contains a 640 (spatial) x 480 (spectral) silicon photodiode array, with a 380-1050 nm spectral bandpass occupying approximately 106 rows of the detector. A two-zone filter comprised of two different Schott glasses eliminates multiple grating orders. The two focal planes together cover 544 spectral channels with a dispersion of 6.55 nm/channel in the VNIR and 6.63 nm/channel in the IR. The optics and focal planes are gimbaled, and a pre-programmed slew can be used to remove groundtrack motion while superimposing a scan across a target. CRISM will operate in two basic modes: a scanning, high resolution mode to hyperspectrally map small, targeted areas of high scientific interest, and a fixed, nadir-pointed, lower resolution pixel-binned mode using selected wavelength channels to obtain near-global coverage to find targets. Preliminary performance of the CRISM instrument is presented, and is compared with prior system design predictions.

The exploitation of infrared polarimetry has been shown to yield good results when applied to target discrimination in military applications and to civilian remote sensing problems. Similarly, numerous workers have shown that imaging sensors operating in the far infrared spectral bands may be useful in such counter-terror applications as concealed weapon and biological and chemical agent detection. Unfortunately, these detection and discrimination techniques have not been exploited because of the lack of suitable sensors capable of making the necessary measurements with acceptable sensitivity. In this paper we present and discuss several methods for measuring the polarization signature of a target scene using sensors with no moving parts. We also present and analyze a far infrared imaging system based on an uncooled bolometer focal plane array. The methods of measuring polarization signature with no moving parts include a coherent in-phase and quadrature approach suitable for both broad- and narrow-band sensors, a broadband sensor using channeled spectropolarimetry, a variant of this latter method that involves correlation of the spectral signatures with those of known targets, and another variant that uses an electro-optic or an acousto-optic modulator. A focal plane array of uncooled bolometers has been proposed before as a far infrared imaging system. One problem with such devices is that they are not sensitive enough to detect the low-intensity emission from a room-temperature blackbody in the far infrared bands. A potential solution to this problem is to use a high- or low-temperature blackbody to illuminate the scene to be imaged. In this paper, methods of measuring the infrared polarimetric signature and the far-infrared spatial signature of a scene will be presented and discussed.

The design and performance of a commercial short-wave-infrared (SWIR) InGaAs microcamera engine is presented. The 0.9-to-1.7 micron SWIR imaging system consists of a room-temperature-TEC-stabilized, 320x256 (25 μm pitch) InGaAs focal plane array (FPA) and a high-performance, highly customizable image-processing set of electronics. The detectivity, D*, of the system is greater than 10¹³ cm-&sqrt;Hz/W at 1.55 μm, and this sensitivity may be adjusted in real-time over 100 dB. It features snapshot-mode integration with a minimum exposure time of 130 μs. The digital video processor provides real time pixel-to-pixel, 2-point dark-current subtraction and non-uniformity compensation along with defective-pixel substitution. Other features include automatic gain control (AGC), gamma correction, 7 preset configurations, adjustable exposure time, external triggering, and windowing. The windowing feature is highly flexible; the region of interest (ROI) may be placed anywhere on the imager and can be varied at will. Windowing allows for high-speed readout enabling such applications as target acquisition and tracking; for example, a 32x32 ROI window may be read out at over 3500 frames per second (fps). Output video is provided as EIA170-compatible analog, or as 12-bit CameraLink-compatible digital. All the above features are accomplished in a small volume < 28 cm³, weight < 70 g, and with low power consumption < 1.3 W at room temperature using this new microcamera engine. Video processing is based on a field-programmable gate array (FPGA) platform with a soft-embedded processor that allows for ease of integration/addition of customer-specific algorithms, processes, or design requirements. The camera was developed with the high-performance, space-restricted, power-conscious application in mind, such as robotic or UAV deployment.

Over the years there has been considerable investments in dualband infrared focal plane array (FPA) technology. Both quantum well photodetector and HgCdTe photovoltaic approaches have now achieved dualband-imaging capability. The fruits of these investments are being realized with FPAs that approach levels of performance and maturity sufficiently high to meet end-user needs. Dualband FPAs were developed primarily in support of conceptual surveillance, acquisition and tracking scenarios for a variety of target types. These dualband FPAs may be considered the functional equivalent of dual-channel imagers comprising a dichroic beamsplitter and two distinct FPAs. The volume and cooling requirements of the dual-channel imagers are appreciable relative to the single, dualband FPA. Novel spectral imaging concepts are also enabled with the current dual band, and future multi-waveband, FPA technologies.

A mid-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) 1024x1024 pixel quantum well infrared photodetector (QWIP) focal plane array has been demonstrated with excellent imagery. MWIR focal plane has given noise equivalent differential temperature (NETD) of 19 mK at 95K operating temperature with f/2.5 optics at 300K background and LWIR focal plane has given NEDT of 13 mK at 70K operating temperature with same optical and background conditions as MWIR array. Both of these focal plane arrays have shown background limited performance (BLIP) at 90K and 70K operating temperatures with the same optics and background conditions. In this paper, we will discuss their performance in quantum efficiency, NETD, uniformity, and operability.

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.

A high performance hand held thermal imaging camera has been developed based upon 320 x 256 elements InSb focal plane array (FPA) operating in MWIR region. The primary design goal of this camera was to design a low cost, compact, lightweight and man portable thermal camera with a recognition range of 2 Km. A staring FPA based upon the InSb technology with long and variable integration time provides the answer best suited under these requirements. The system provides the various features such as non-uniformity correction (NUC), bad pixel detection and replacement (BPR), contrast enhancement, histogram equalization and digital scan conversion for CCIR-B compatible output. The design methodology and the performance are presented.

We designed and built an electro-optical sensor to detect human bodies. The aim of this paper is to describe a device to make easier the localization of lost people in natural disasters or in dangerous environments. The detection is realized in base of the infrared radiation emitted by the human body. We employ point commercial pyloric quantum sensors, the electronic assembly integrates the captured infrared energy by using low noise chip. The optical device include a Cassegrain antenna, a diffraction grating which besides to choose in automatic way the correct wavelength emitted by the human body, it is useful as optical filter.

The NASA Solar Dynamics Observatory (SDO), scheduled for launch in 2008, incorporates a suite of instruments including the EUV Variability Experiment (EVE). The EVE instrument package contains grating spectrographs used to measure the solar extreme ultraviolet (EUV) irradiance from 0.1 to 105 nm. The Multiple EUV Grating Spectrograph (MEGS) channels use concave reflection gratings to image solar spectra onto CCDs that are operated at -100°C. MEGS provides 0.1nm spectral resolution between 5-105nm every 10 seconds with an absolute accuracy of better than 25% over the SDO 5-year mission. MEGS-A utilizes a unique grazing-incidence, off-Rowland circle (RC) design to minimize angle of incidence at the detector while meeting high resolution requirements. MEGS-B utilizes a double-pass, cross-dispersed double-Rowland circle design. MEGS-P, a Ly-α monitor, will provide a proxy model calibration in the 60-105 nm range. Finally, the Solar Aspect Monitor (SAM) channel will provide continual pointing information for EVE as well as low-resolution X-ray images of the sun. In-flight calibrations for MEGS will be provided by the on-board EUV Spectrophotometer (ESP) in the 0.1-7nm and 17-37nm ranges, as well as from annual under-flight rocket experiments. We present the methodology used to develop the MEGS optical design.

High quality imaging is a key parameter in many scientific applications. CCD and ICCD cameras have proven to be powerful tools and are consequently used in a wide range of fields such as engineering research and physical or biological sciences. The very new Electron Multiplying CCD technology seems now to provide the most sensitive detection capabilities. Here we compare analytically the signal-to-noise performance of the three systems and identify the most influencing parameters. The SNR provided by CCDs is strongly influenced by the readout noise and is also a significant function of the pixel rate. ICCD cameras are practically not at all affected by the CCD chip temperature and are shown to be mostly shot-noise-limited because readout and dark current noises are negligible. Therefore no cooling is needed for ICCDs. Although EMCCDs unite the quantum efficiency of CCDs and the gain of ICCDs, their performance is constricted by charge transfer and dark current noises which will be multiplied up along with the signal by the gain register. Therefore, EMCCDs must be strongly cooled (down to -70°C) and slowly read out in order to get rid of any unwanted "pseudo signal". In addition, their properties limit exposure times to milliseconds time scales and longer. We conclude that ICCD cameras remain the most efficient systems in all gated experiments and perform very well in extreme low light situations. They still keep great advantages over standard CCDs and the new incoming generation of EMCCDs.

Image intensifiers (I2) have gained wide acceptance throughout the Army as the premier nighttime mobility sensor for the individual soldier, with over 200,000 fielded systems. There is increasing need, however, for such a sensor with a video output, so that it can be utilized in remote vehicle platforms, and/or can be electronically fused with other sensors. The image-intensified television (I2TV), typically consisting of an image intensifier tube coupled via fiber optic to a solid-state imaging array, has been the primary solution to this need. I2TV platforms in vehicles, however, can generate high internal heat loads and must operate in high-temperature environments. Intensifier tube dark current, called "Equivalent Background Input" or "EBI", is not a significant factor at room temperature, but can seriously degrade image contrast and intra-scene dynamic range at such high temperatures. Cooling of the intensifier's photocathode is the only practical solution to this problem. The US Army RDECOM CERDEC Night Vision & Electronic Sensors Directorate (NVESD) and Ball Aerospace have collaborated in the reported effort to more rigorously characterize intensifier EBI versus temperature. NVESD performed non-imaging EBI measurements of Generation 2 and 3 tube modules over a large range of ambient temperature, while Ball performed an imaging evaluation of Generation 3 I2TVs over a similar temperature range. The findings and conclusions of this effort are presented.

Current developments in head mounted night vision systems involve the use of various video cameras and displays. Many development efforts are aimed at generating digital video images of different parts of the EM spectrum and fusing this information into a single real time video image for the user. Image intensified video cameras are one of the camera types that are undergoing continuing development to serve this purpose. The topic of this paper is a discussion of the electronic architectures that may be used in designing such cameras. This camera development area has highlighted the importance of the downstream electronics that receives and processes the "raw" digital video signal coming from the miniature camera. Some of the significant video system architecture decisions bear on the partitioning of these downstream video processing functions throughout the overall vision system in which the camera resides. The rapidly evolving capabilities of the digital video electronic hardware that provides the video processing functions offer a wide choice of system architectures for video system design. In this paper the camera and its associated digital processing functions are discussed as an integrated camera system.

A new family of miniature nano-tunable narrowband infrared filters has been developed based on the thermo-optic properties of thin film semiconductors. Originally developed for fiber optic telecommunications networks at 1.5 μm, the technology has now been extended to the 3-5 μm range, leading to very compact tunable filters with passbands on the order of 0.5% of center wavelength and tuning ranges up to 4% of center wavelength. Two applications are described. First, a prototype carbon monoxide sensor testbed based on a 4550-4650 nm tunable filter is shown to be capable of detecting less than 20 ppm of CO. Second, we show how nano-tunable thin film filters can be integrated with miniature blackbody sources to create a new family of ultra low cost integrated tunable IR emitters, which we have named Firefly. Packaged in TO cans, Firefly devices enable precision detection of gases including carbon dioxide, carbon monoxide, sulphur dioxide, hydrogen cyanide, water vapor, nitric oxide or methane.