Programs in both the U.S. and Britain are attempting to apply staring array technology to the ship-board infrared search and track (SBIRST) problem. A prime objective is to speed processing time, the previous generation of 360 deg scanners having a refresh rate of only 0.5-1.0 Hz. Another objective is to enhance sensitivity using much longer integration times. An impediment, though, is that if all pixels of resolution angle ∅ were to be viewed simultaneously with dedicated detectors each of width w, the total net length of detector material would then have to be very large: 2πw/∅ = 1.57 m = 60" for 100 μRad resolution and 25 μm detectors. So the application of staring array technology to horizon surveillance needs some form of wide viewing technique involving a combination of asymmetric resolution, reduced resolution, split optics or LOS stepping. The present paper suggests that conventional NEI is not the preferred unit of measure for guiding design choices but that instead a form of BLIP S/N can be both simple and intuitive. This S/N unit of measure is used to compare the two main choices for how to adapt staring technology to the horizon surveillance problem.

40x40 element InAlAs/InGaAs APD arrays have been fabricated and characterized for performance in short wave infrared (SWIR) applications. Characterization data collected to date indicate that the arrays have >99% operability at operating gains of 10. The median un-multiplied dark current for an array element is about 170 pA, and the un-multiplied responsivity at 1550 nm is about 0.75 A/W.

Range-gated imaging using indium gallium arsenide based focal plane arrays enables both depth and intensity imaging with eye-safe lasers while remaining covert to night vision goggles. We report on a focal plane array consisting of an indium gallium arsenide photodiode array hybrid-integrated with a CMOS readout circuit, resulting in an all solid state device. A 5 V supply avoids the complication of high voltage supplies and improves reliability, while also allowing the device to be small and lightweight. The spectral sensitivity of InGaAs extends from 0.9 microns to 1.7 microns, allowing the use of commercially available pulsed lasers with 1.5 micron wavelength, several millijoule pulse energies, and nanosecond scale pulse durations. SUI is developing a 320 x 256 pixel imager with the ability to conduct range gated imaging with sub-100 ns gates, while also allowing a 16 ms integration time for imaging in a staring mode. The pixels are fabricated on a 25 micron pitch for a compact device, and all pixels are gated simultaneously for “snapshot” exposure. High in-pixel gain with nearly noiseless amplification and low dark current enable high sensitivity imaging from ultra-short gates to video rate imaging.

Cu-doped HDVIP detectors with different cut-off wavelengths are routinely manufactured. The DRS HDVIP detector technology is a front-side-illuminated detector technology. There is no substrate to absorb the visible photons as in backside-illuminated detectors and these detectors should be well suited to respond to visible light. However, HDVIP detectors are passivated using CdTe that absorbs the visible light photons. CdTe strongly absorbs photons of wavelength shorter than about 800 nm. Detectors with varying thickness of CdTe passivation layers were fabricated to investigate the visible response of the 2.5-μm-cutoff detectors. A model was developed to predict the quantum efficiency of the detectors in the near infrared and visible wavelength regions as a function of CdTe thickness. Individual photodiodes (λ_c = 2.5 μm) in test bars were examined. Measurements of the quantum efficiency as a function of wavelength region will be presented and compared to the model predictions.

We report on recent results in using InGaAs/InP focal plane arrays for visible light imaging. We have fabricated substrate-removed backside illuminated InGaAs/InP focal plane arrays down to a 10 μm pitch with high quantum efficiency from 0.4 μm through 1.7 μm. This focal plane array can be used for visible imaging as well as imaging eye-safe lasers. Using the InGaAs/InP materials system for visible imaging applications has several advantages over silicon based CMOS or CCD imagers including inherent radiation hardness, the ability to simultaneously achieve low crosstalk (less than 1%), and bandwidths exceeding 1 GHz, as well as the ability to image out to 1.7 μm.

We describe innovations in short wave infrared (SWIR) InGaAs focal plane arrays and cameras which now allow imaging under starlight only conditions at video rates. These lattice matched In_.53Ga_.47As imagers detect 0.9 μm to 1.7 μm SWIR band light, which is generally reflected from the imaged target. At night, the sources of light are the night glow, stars, the moon, or light pollution from nearby towns and cities. Detectivities, D*, greater than 6 x 10¹³ cm-√Hz/W and no image lag are necessary to image under starlight only conditions at RS-170 video rates. The InGaAs arrays are now commercially available in formats as large as 640 x 512 on a 25 μm pitch, and custom arrays are being manufactured on a 15 μm pitch with pixel counts as large as 1280 x 1024. The cameras are capable of adapting to the different light conditions that may occur in a scene over a 24-hour period, without the need for new corrections; this illumination variation can be over 5 orders of magnitude. The InGaAs material is stable, making new field corrections unnecessary for the life of the camera and eliminating the need for mechanical parts. The cameras have a dual output design to produce corrected analog output at video rates without the assistance of a computer, and corrected digital output through a 14 bit Camera Link interface.

A long wave infrared (LWIR) computational imaging system has been designed and fabricated that has a decreased hyperfocal distance compared to traditional optics. Through the combination of aspheric optics and signal processing the near point with clear imagery has been reduced from 50m to less than 10m. Both systems deliver high quality imaging when the object is at infinity. The decrease in the hyperfocal distance was realized though the use of Wavefront Coding, a technology where all system components are jointly optimized. The system components include the optics, detector and signal processing. System optimization is used with optical/digital constraints such as manufacturability, cost, signal processing architecture, FPA characteristics, etc. Through a special design of the system’s optical phase, the system becomes invariant to the aberrations that traditionally limit the effective operational range. In the process of becoming invariant, the specialized phase creates a uniform blur across the detected image. Signal processing is applied to remove the blur, resulting in a high quality image. In this paper imagery from the Wavefront Coded system is described and compared to traditional imagery.

In the design of optical systems, simple straightforward requirements are often complicated by unusual and unique constraints. In this particular case a design mapping a 20° square field of view onto a CCD sensor is complicated by the requirement that the wide field of view must not vignette through a narrow-diameter, finite-length cylindrical aperture. Furthermore, the design must use off-the-shelf optics available from any major vendor. The imaging system is designed to operate in the near IR. The 20° square field of view must pass through a 20.32mm diameter, 40mm long cylindrical tube without vignetting. This constraint prohibits the use of a simple achromat whose back focal length would place the image within the cylindrical tube. Two design approaches are discussed, a Keplerian telescope with a field lens, and a reverse telephoto system. Matlab programs have been written that evaluate the first-order optical principles to arrive at a design solution space. Representative solutions are then evaluated in Zemax using the built-in lens catalog to select appropriate lenses. The results show the advantages and limitations of each particular design approach.

We describe the optical and mechanical design of an athermal infrared objective lens with an afocal anamorphic adapter. The lens presented consists of two modules: an athermal 25mm F/2.3 mid-wave IR objective lens and an optional panoramic adapter. The adapter utilizes anamorphic lenses to create unique image control. The result of which enables an independent horizontal wide field of view, while preserving the original narrow vertical field. We have designed, fabricated and tested two such lenses. A summary of the assembly and testing process is also presented.

This paper describes a novel design of a 1:30 zoom FLIR in the MWIR. Special emphasis is spent on the design considerations of such a FLIR and on the specific challenges associated with the design of a high zoom ratio FLIR. The problems and their solutions are discussed through out the paper and quantitative results are tested.

A low-cost polymer infrared imaging lens well suited to military and security applications in the 8 to 14 μm region has been made. It has a focal length of 50 mm, and an f/number of 0.8. The design requires four aspheric or Fresnel surfaces. Improvements in molding have allowed significant improvements over a 25 mm focal length design previously discussed.

Umicore IR Glass has developed an industrial process to manufacture low cost chalcogenide glasses with well controlled properties. These materials called GASIR 1 and GASIR 2 are transparent in the 3-5 and 8-12 μm atmospheric windows allowing a great range of applications in thermal imaging. A high precision industrial moulding process has been developed and set up allowing to mould GASIR material directly into high quality finished spherical, aspherical and diffractive lenses. This process is especially attractive for medium and high volume applications. Specific antireflection coatings have also been developed offering a maximum transmission of 98% when coated with high efficiency coating. Several optics from 17.5 mm F/1 to 100 mm F/1.25 focal length based on existing germanium optics have been redesigned especially for GASIR 1 and GASIR 2 glasses. The lenses have been manufactured using Umicore’s moulding technology. These chalcogenide moulded optics are used in various applications like imaging, process control, military applications and their performances (modulation transfer function has been measured) are reviewed and compared to the existing solutions made of traditional IR optics.

Bodenseewerk GmbH generally works on challenging projects comprising Microsystems, e.g. micro-optics (micro-lenses, micro-mirrors). We utilize state-of-the-art laboratory equipment and simulation software (e.g. optical design with ZEMAX, ASAP and GLAD). Our recent activities on the development of several infrared micro-optical devices focus on high speed imaging of scenes with high angular resolution including the analysis of physical properties of the detected light (e.g. spectral content, polarization) utilizing staring IR sensors with focal-plane-arrays operating in a snap shot mode at high frame rates. We report about the development of so called micro-optical multiplexers which: (a) comprise micro-optical arrays and electro-mechanical micro-actuators, (b) image several fields of view with high resolution onto a single focal-plane-array, (c) image several fields of view with enhanced spatial resolution [by the factor of four compared to (b)] in a modified realization onto one focal-plane-array and (d) analyze the spectral content of an image using a single-band photon detector-array and multi-frame processing. The micro-opto-electro-mechanical multiplexer (MOEM) systems all consist of a primary objective, a MOEM image-steering respectively image coding device and a secondary objective. The primary objective images one or more suitable formed individual fields of view onto a common intermediate image plane. The MOEM devices comprise combinations of focusing and defocusing micro-lens-arrays, micro-shutter-arrays and micro-filter-arrays which are mounted parallel to each other near the intermediate image plane. The MOEM devices exhibit their above mentioned function modes by laterally displacing the micro-arrays with the help of modern micro-actuators. The secondary objective is utilized as relay optical stage. A modern common focal-plane-array is used as detector device. The micro-actuators responsible for the relative displacement of the micro-arrays are highly miniaturized while maintaining large displacement ranges and high linearity, reproducable positioning and reliability. This paper outlines the general sensor concept, explains the underlying principles and delineates the optical systems layout. Recent hardware realizations useful in military applications concerning image and laser beam steering are presented.

Earlier studies have shown that multiple capture can achieve high SNR, but cannot satisfy the high dynamic range (HDR) and high speed requirements of the Vertically-Integrated-Sensor-Array (VISA) project. Synchronous self-reset, on the other hand, can achieve these requirements, but suffers from poor SNR. Extended counting can achieve high dynamic range at high frame rate and with good SNR, but at the expense of high power consumption. The paper proposes a new HDR focal plane array architecture, denoted by folded-multiple capture (FMC), which by combining features of the synchronous self-reset and multiple capture schemes, can satisfy the VISA requirements at a fraction of the power dissipation and with more robustness to device variations than extended counting. The architecture is also capable of detecting subframe disturbances, e.g., due to laser jamming, and correcting for it.

This paper serves as a companion to SPIE paper 4820-36, presented in Seattle in 2002. Advances in the design and application of “Variable Spatial Acuity” focal plane arrays are reported here, with specific examples of large format imagers and applications to which they are being applied. These devices have been developed through the combined requirements of (a) covering a wide total field of view while (b) retaining the highest possible spatial resolution on the objects of interest while at the same time (c) operating at the highest possible frame rate. Many thousands of frames per second are possible with the prototype imager while maintaining high spatial resolution. The prototype device operates as a visible imager, and we are pursuing the transition of this technology into the infrared domain. This paper will concentrate on applications of the technology and will show some imagery collected with the systems developed for their use.

In this paper, we present the algorithm and operation of an aVLSI chip that can extract normal optical flow by using the gradient approach without interfering with the imaging process. This approach is feasible for scaling to larger arrays without affecting the processing or the processing area. Our system has a 92 x 52 photosensitive array of APS pixels at the core with processing circuits on the periphery. We discuss the approach and the different blocks in the design and then demonstrate the working of the individual blocks and of the system as a whole. The chip outputs the image, the spatial and temporal gradients and the normal flow at the read-out frame-rate with no penalty to the imaging process. The chip occupies an area of 4.5 mm² and consumes 2.6 mW (at V_dd = 5V). Once normal flow is obtained, the chip can be used to compute focus of expansion, time to contact and many other motion properties of images that can be used to control robots. Tracking systems can use the velocity and segmentation of moving objects can be realized using motion discontinuity.

Several useful but computationally expensive sensor processing tasks can be mapped to the natural behavior of networks of ideal, passive analog components. For example, spatially smoothing an image can be achieved by convolving it with a Gaussian kernel, or by applying it to a 2-D resistor-capacitor network, and then relying on the diffusive behavior of the network to provide a smoothed image. Numerical computation is replaced with physical computation. But implementing analog networks is challenging due to the limitations of real analog components. They have low precision, vary with temperature, and are non-uniform from unit to unit. Moreover, physics limits the size of analog components. For example, to achieve a particular capacitance, using material of a given dielectric constant, a VLSI capacitor must occupy a certain area on the chip. Twice the capacitance will require twice the area. We describe a set of digital circuits that emulate analog components. These circuits provide analog behavior with arbitrary precision, uniformity, noise immunity, and no temperature dependence. Their size is limited by VLSI linewidths and the circuit approach taken. Networks of these digital circuits behave as do their analog equivalents, making physical computation practical for sensor processing closely coupled to the FPA.

This work reports on progress on development of polycrystalline PbSe infrared detectors at the Centro de Investigación y Desarrollo de la Armada (CIDA). Since mid nineties, the CIDA owns an innovative technology for processing uncooled MWIR detectors of polycrystalline PbSe. Based on this technology, some applications have been developed. However, future applications demand smarter, more complex, faster yet cheaper detectors. Aiming to open new perspectives to polycrystalline PbSe detectors, we are currently working on different directions: 1) Processing of 2D arrays: a) Designing and processing low density x-y addressed arrays with 16x16 and 32x32 elements, as an extension of our standard technology. b) Trying to make compatible standard CMOS and polycrystalline PbSe technologies in order to process monolithic large format arrays. 2) Adding new features to the detector such as monolithically integrated spectral discrimination.

Current mid-wave infrared detector technologies, such as Indium Antimonide, Mercury Cadmium Telluride, and Platinum Silicide, require the use of expensive, heavy, and power hungry cryogenic coolers or expensive multistage thermoelectric coolers. There is a need for a low cost uncooled mid-wave infrared (MWIR) technology for use in applications where cost, power, size, and reliability are of most importance. Northrop Grumman Electro-Optical Systems (EOS) is currently developing such a sensor based upon its low cost Lead Selenide (PbSe) detector technology. Utilizing its extensive production experience in producing high performance linear PbSe arrays, EOS has developed a 320X256 staring PbSe Focal Plane Array. This paper provides a summary and status of the development efforts and associated performance of EOS' new PbSe FPA's.

TV/4 format (320×256) detectors are today the most produced. They have demonstrated high thermal performance and are cost effective at the mass production level. However, in response to system requirements of very high resolution, miniaturization and cost reduction, SOFRADIR is now offering full TV format (640x512) detectors with graduated levels of performances regarding pitch size and cryogenics. In particular a TV format with 15 μm pitch is offered allowing the integration of highly miniaturized cryogenics dedicated to compact systems or, depending of the applications, the upgrade of existing systems by using the same miniature cryogenics as the ones used for TV/4 format. Regarding TV format (640x512) with 15μm pitch, technological adaptations were validated at CEA-LETI/LIR (France) at the beginning of 2002. With respect to the 20μm pitch TV formats whose purpose is to offer high resolution performances in slightly modified cryogenics, this new 15μm pitch MCT TV format exhibits even higher performances in very small size optimized cryogenics in order to fit the system requirements of miniaturization and cost reduction and to achieve a cost effective production level. In this way, this 15μm pitch 640x512 MWIR MCT detectors will become, in the coming years, the most affordable large format at production level.

Detector characteristics of Au- and Cu-doped High Density Vertically Integrated Photodiode (HDVIP) detectors are presented in this paper. Individual photodiodes in test bars were examined by measuring I-V curves under dark and illuminated conditions at high bias values. Noise as a function of frequency has been measured on Au- and Cu-doped MWIR [λ_c(78 K) = 5 μ] HDVIP HgCdTe diodes at several temperatures under dark and illuminated conditions. No excess currents are observed above the photocurrents for reverse bias values out to 500 mV. Both Au- and Cu-doped detectors measured at 85 K, exhibit gain values between 40 and 50 at 8 V reverse bias. Gain values fell in this same range even when the flux incident on each type of detector was varied. The excess noise factor for the Cu-doped detectors ranged from 1.35 to 1.69 depending on the incident flux. Variation is probably due to measurement error. The noise at 8 V reverse bias is white for the Cu-doped detectors. The Au-doped detectors exhibited 1/f noise at 8 V reverse bias. At higher frequencies where the noise spectrum was quasi-white, the excess noise factor for the Au-doped detector was in the 1.0 to 1.5 range.

After completing the development of a digital detector with a format of 640x512 elements ("Sebastian"), SCD is now developing a mid format digital detector with 480x384 elements. This detector is based on the same concept as Sebastian, which was introduced last year at the SPIE conference in Orlando. The 480x384 element detector has all the features and performance of Sebastian as then introduced, and in addition exhibits some additional functionality. The format of the 480x384 element detector was chosen in order to maintain the same active area as in a standard format 320x256 element detector of today. Thus with specific system optics, a higher resolution is achieved with our new detector. As a direct consequence, the detection range is increased by 22-35% depending on the target type, when using this detector instead of the conventional 320x256 element detector in a typical system. The 480x384 element detector is designed to be integrated both into imaging systems and into head seekers missile-applications. In this paper we present the concept and the basic structure of the detector, the special operation modes unique to the digital detector, and the results of detection range calculations.

The Albion programme aims to develop high pixel count third generation infrared modules for medium, long and dual band infrared imager systems. The medium wave Albion detector having 1024x768 pixels on a 26μm pitch is the largest detector of its type in Europe. With a typical NETD of 12mK and capable of 50Hz frame rate output, this high performance detector has been encapsulated and combined with a high reliability cryogenic cooler to form a core module. To illustrate the high performance of the detector and to demonstrate the use of the core module a complete thermal imaging camera has been built. Although designed as an experimental system this camera, being only 300x420x180mm in size shows the relatively small step required to take the system to a fully productionised state. This paper describes the detector technology and other subsystems (e.g. optics, electronics and uniformity correction) which have been integrated into a high performance thermal imaging system.

An attempt is made to connect the material parameters of Hg_1-xCd_xTe layer growth to the parameters measured following photovoltaic detector fabrication. We found that the Cd composition X value extracted from spectral response measurements on detectors at 78 K are lower than the X values obtained from the room temperature transmission measurements, or the X value used to fit the measured material minority carrier lifetime versus temperature data. The lateral collection length L_c that determines the thermally generated carriers that contribute to the diffusion current and L_opt extracted from the "flood-illuminated" to "focused-spot" photocurrent ratio are in excellent agreement. Devices exhibit near theoretical R_oA uniformity at 77K for MWIR, LWIR and VLWIR. R_oA_opt was also found to be uniform throughout the range of detector dimensions measured such as 8 μm diameter circular to 250 μm x 250 μm square. Median R_oA_opt values are 1266, 66 and 0.75 ohm-cm² for the 9.7, 11.3 and 15.4 μm cutoff wavelengths respectively. The uniformity in R_oA_opt confirms that the detector performance is limited by the bulk properties of the material, and not by surface effects.

SCD has developed a High Performance Detector Dewar Cooler (DDC) called “Piccolo” for IR detection in the MWIR, which has low power consumption, low weight and low cost. The DDC characteristics are optimized for handheld camera applications. The Piccolo DDC is based on the advanced “Blue Fairy” Focal Plane Processor (FPP) which is bonded to a 320x256 element InSb FPA. The Blue Fairy FPP is used in a special mode of operation for very low power consumption of less than 25mW. A special dewar has been developed for the Piccolo which has a low heat load of less than 140mW. A new cooler designed for low power consumption and low weight is integrated into the dewar. This results in a total power consumption for the DDC at an ambient temperature of 23°C of below 5W. The total weight of the whole DDC is less than 400gr. All the components of the Piccolo were designed for low cost production while keeping the high performance and reliability standards of all SCD detectors.

For evaluation of the possibilities and potentials of multispectral infrared imaging a filter wheel camera system was developed. The camera is designed for high speed operation permitting acquisition of subsequent MWIR spectral images in short time. Potential applications of a multispectral camera are temperature measurement, gas and fire visualisation. Some experiments were performed to validate the applicability of the camera system.

Photoconductors based on multi-layer structure consists of homogeneous narrow-gap n-Hg_1-xCd_xTe absorbing layer (n-absorber) blocked by thin adjacent graded-gap Hg_1-xCd_xTe layers have been fabricated and examined. A possible giant increase in responsivity of Long-Wave Infrared (LWIR) photoconductor (spectral range from 8 to 14 μm) and Very Long-Wave Infrared (VLWIR) photoconductor (spectral range longer than 14 μm) at 78-100K operating temperature was predicted. Prediction is based on suggestion that interfaces in three-layer sensitive structure grown by MBE in single run and consists of n-absorber and adjacent graded-gap layers of native material and same type of conductivity will be free of both recombination centers and charge states. Theoretical analysis has shown that formation of diffusion barrier within graded-gap layers is occurred during illumination of photoconductor. That diffusion barrier prevents excess holes excited in homogenous absorber layer from moving to surfaces. Therefore excess holes will recombine preferably in active region of photoconductor, thus giving high quantum efficiency and good responsivity. Measurements performed on fabricated photoconductors showed near ideal background limited performance (BLIP) with significantly increased value of peak responsivity. Wide shape of spectral responsivity curves is evidence that surface recombination at interfaces was eliminated.

Programs in both the U.S. and Britain are attempting to apply staring array technology to the ship-board infrared search and track (SBIRST) problem. A prime objective is to speed processing time, the previous generation of 360 deg scanners having a refresh rate of only 0.5-1.0 Hz. Another objective is to enhance sensitivity using much longer integration times. An impediment, though, is that if all pixels of resolution angle ∅ were to be viewed simultaneously with dedicated detectors each of width w, the total net length of detector material would then have to be very large: 2πw/∅ = 1.57 m = 60" for 100 μRad resolution and 25 μm detectors. So the application of staring array technology to horizon surveillance needs some form of wide viewing technique involving a combination of asymmetric resolution, reduced resolution, split optics or LOS stepping. The present paper suggests that conventional NEI is not the preferred unit of measure for guiding design choices but that instead a form of BLIP S/N can be both simple and intuitive. This S/N unit of measure is used to compare the two main choices for how to adapt staring technology to the horizon surveillance problem.

The Navy faces an ever evolving threat scenario, ranging from sub-sonic sea skimming cruise missiles to newer, unconventional threats such as that experienced by the USS Cole. Next generation naval technology development programs are developing “stealthy” ships by reducing a ships radar cross section and controlling electromagnetic emissions. To meet these threat challenges in an evolving platform environment, ONR has initiated the “Wide Aspect MWIR Array” program. In support of this program, Raytheon Vision Systems (RVS) is developing a 2560 X 512 element focal plane array, utilizing Molecular Beam Epitaxially grown HgCdTe on silicon detector technology. RVS will package this array in a sealed Dewar with a long-life cryogenic cooler, electronics, on-gimbal power conditioning and a thermal reference source. The resulting sub system will be a component in a multi camera distributed aperture situation awareness sensor, which will provide continuous surveillance of the horizon. We will report on the utilization of MWIR Molecular Beam Epitaxial HgCdTe on Silicon material for fabrication of the detector arrays. Detector arrays fabricated on HgCdTe/Si have no thermal expansion mismatch relative to the readout integrated circuits. Therefore large-area focal plane arrays (FPAs) can be developed without concern for thermal cycle reliability. In addition these devices do not require thinning or reticulation like InSb FPAs to yield the high levels of Modulation Transfer Function (MTF) required by a missile warning sensor. HgCdTe/Si wafers can be scaled up to much larger sizes than the HgCdTe/CdZnTe wafers. Four-inch-diameter HgCdTe/Si wafers are currently being produced and are significantly larger than the standard 1.7 inch x 2.6 inch HgCdTe/CdTe wafers. The use of Si substrates also enables the use of automated semiconductor fabrication equipment.

BAE SYSTEMS has developed a laser-illuminated, gated imaging system for long range target identification which has generated bright images at ranges in excess of 10km from modest laser energies. The system is based on a short pulsewidth laser and a custom detector for sensing the return pulse. The source is a Nd YAG laser converted by an optical parametric oscillator (OPO) to 1571nm and producing 20ns pulses at 15Hz. The detector (named SWIFT) is a 320x256 array of HgCdTe photodiodes operating with high avalanche gain to achieve sensitivities as low as 10 photon rms. A custom silicon multiplexer performs the signal injection and temporal gating function, and adds additional electronic gain. Trials show that the current detectors have gate edges equivalent to 1.5m in range and complete extinction of signals outside of the gated range. The detector is encapsulated in an integrated-detector-cooler-assembly and utilises standard productionised thermal imaging electronics to perform non-uniformity correction and grey scale images. Imaging trials using the camera have shown little excess noise, crosstalk or non-uniformity due to the use of avalanching in the HgCdTe photodiodes up to gains of over 100. The images have shown high spatial resolution arising from the use of solid state focal plane array technology. The imagery, collected both in the laboratory and in field trials, has been used to explore the phenomenology unique to laser-illuminated targets and to verify system models.

We have demonstrated the successful growth of mercury cadmium telluride (MCT) infrared detector material on silicon substrates. Growth on silicon increases the maximum achievable array size, reduces manufacturing costs, and paves the way for infrared detector growth directly on multiplexing circuits. In addition, the thermal match with multiplexing circuits eliminates the requirement for complex thinning procedures. Since the crystal lattice of MCT is not matched to that of silicon, an intermediate buffer layer is required. We have developed a buffer layer technique that is compatible with MCT grown by Metal Organic Vapour Phase Epitaxy (MOVPE). Long-wavelength heterostructure device designs were grown using this technique. Test devices and 128x128 focal plane arrays were fabricated by wet etching mesa structures and passivating the mesa side-walls with a thin layer of CdTe. An indium flip-chip technique was used to form interconnects between the detector material and test or multiplexing circuit. At 77K, 50x50μm test devices with a 10.2μm cut off wavelength have been measured with R₀A~1x10³Ohm cm² at zero bias and R.A~1x10⁴Ohm cm² at 0.1V reverse bias. Arrays from this material have been demonstrated with operabilities up to 99.7%.

At the Army Research Laboratory (ARL), a new ternary semiconductor system CdSe_xTe_1-x/Si(211) is being investigated as an alternative substrate to Bulk-grown CdZnTe substrates for HgCdTe growth by molecular beam epitaxy. Under optimized conditions, best layers show surface defect densities less than 400 cm^-2 and full width at half maximum as low as 100 arcsec with excellent uniformity over 3 inch area. LWIR HgCdTe on CdTe/Si substrates have also been grown and characterized with optical, x-ray diffraction, etch pit etching and Hall effect measurements. Photo Voltaic devices fabricated on these LWIR material shows G-R limited performance at 78K indicating detector performance is not limited by the bulk properties of the grown material.

The VISA program has been sponsored by DARPA to enable a significant enhancement in signal conditioning, processing, and digitalization on the focal plane of visible and infrared sensors. The approach being developed builds on the traditional “hybrid” structure of a detector with a 2D array of indium-bump interconnects to a silicon readout. VISA will allow additional layers of silicon processing chips to be connected below the readout to provide more complex functionality. Connections will be fully arrayed two-dimensionally with one or more vias per pixel possible. The structural overview will be presented along with several application candidates that appear to be most promising to exploit this technology. These include active/passive sensors, expanded charge storage capacity for full flux utilization in the LWIR, cameras on a chip, high speed sub-frame collection to defeat pulsed laser interference, together with digital output with greater bit depth than currently possible from analog outputs. An A/D candidate circuit to achieve this performance within each pixel will be described.

The paper investigates the suitability of ΣΔ modulation based FPA readout schemes for use in Vertically Interconnected Sensor Arrays requiring ultra high dynamic range and frame rate. It is shown that the extended counting scheme is capable of achieving the DR and frame rate requirements but at the expense of high power consumption. Extended counting is also shown to outperform several other HDR schemes in terms of SNR at the ultra high DR and frame rate.

Infrared detectors based on Hg_1-xCd_xTe and grown by the MOVPE process can be designed to have very low dark currents, even for temperatures above 200K. These low dark currents are compatible with achieving background-limited performance at a temperature of 200K in f/2. However, in practice the detectors suffer from high 1/f noise. In this paper, a novel approach is explored in which most of the low frequency noise can be eliminated by operating the arrays at near zero bias. Using this technique, imaging arrays have been demonstrated at temperatures up to 220K giving a NETD of around 60mK in f/2.

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 which has been shown to be inherently scalable across format size without losing performance properties. Current offerings range from 256x256 to 2Kx2K formats ranging in between 30um and 20um pixel pitch, with 15um pixel pitch FPAs in development. 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 of both InSb detectors and silicon ROICs. Improvements made to enable large format fabrication have improved the yields and lowered the cost of smaller format FPAs as well. 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. This has resulted in breakthroughs in FPA size, performance, reliability and yeilds. The latest yield, operability, and performance data will be shown. Data will be drawn from a population of approximately 30 2K FPAs and 50 1K FPAs. Recent developments in smaller pixel pitch and other R&D areas will be discussed.

Antimonide Based Compound Semiconductors (ABCS) and a new family of advanced analogue and digital silicon read-out integrated circuits form the basis of the SCD 3^rd generation detector program, which builds on the firm platform of SCDs existing InSb-FPA technology. In order to cover the MWIR atmospheric window, we recently proposed the epitaxial alloys: InAs_1-y Sb_y on GaSb with 0.07 < y < 0.11 and In_1-zAl_z Sb on InSb with 0 < z < 0.03. In this paper we focus on the results of some of our recent work on epitaxial In_1-zAl_z Sb grown on InSb by Molecular Beam Epitxay (MBE). In epitaxial InSb (_z = 0), we demonstrate the performance of Focal Plane Arrays (FPAs) with a format of 320x256 pixels, at focal plane temperatures between 77K and 100K. An operability has been achieved which is in excess of 99.5%, with a Residual Non-Uniformity (RNU) at 95K of less than 0.03% (standard deviation/dynamic range). Moreover, after a two point Non-Uniformity Correction (NUC) has been applied at 95K, the RNU remains below ~0.1% at all focal plane temperatures down to 85K and up to 100K without the need to apply any further correction. This is a major improvement in both the temperature of operation and the temperature stability compared with implanted diodes made from bulk material. We also demonstrate rapid progress in the development of low current epitaxial InAlSb photodiodes with high uniformity and low dark current that offer a range of cut-off wavelengths shorter than in InSb. Preliminary results are presented on FPAs with a cut-off wavelength in the range λ_C~5μ.

By measuring the spectral responses of infrared focal plane arrays (IRFPAs), one can extract at a given wavelength the cartography of the pixels responses, called the hyperspectral cartography. Recently, hyperspectral cartographies have been obtained from IRFPAs that exhibited small defects of substrate thickness. These defects produce Fizeau fringes across the FPA. By purposely amplifying this phenomenon during the process of realisation, one can easily generate a good approximation of a two-beam interferometer in the immediate neighbourhood of the FPA. Like a classic Michelson interferometer with tilted plane mirrors, this on-a-chip interferometer produces a spatially-modulated interferogram, the Fourier-transform of which yields the spectral content of the illuminating beam. A first prototype of this Fourier-transform microspectrometer on a chip (MICROSPOC) has been realised and tested. Experimental results will be presented and the potential of this approach will be discussed.

Raytheon Vision Systems (RVS) has invented and demonstrated a new class of advanced focal plane arrays. These Advanced FPAs are sometimes called 3^rd Generation or “Next Generation” FPAs because they have integrated onto the FPA the ability to sense multiple IR spectrums, have improved resolution and performance, and conduct image processing on the FPA ROIC. These next generation of FPAs are allowing more functionality and the detection of a more diverse set of data than previously possible with 2^nd Gen FPAs. Examples and history of advanced next generation FPAs are reviewed including RVS’s Multispectral, Uncooled, Adaptive Sensors and other advanced sensors.

The 3rd generation of infrared (IR) detection modules is expected to provide advanced features like higher resolution 1024x1024 or 1280x720 pixels and/or new functionalities like multicolor or multi band capability, higher frame rates and better thermal resolution. This paper is intended to present the current status at AIM on the Mercury Cadmium Telluride (MCT), quantum well (QWIP) and antimonide superlattices (SL) detection modules for ground and airborne applications in the high performance range. For high resolution a 1280x720 MCT device in the 3-5μm range (MWIR) is presently under development. For spectral selective detection, a QWIP detector combining MWIR and 8-10μm (LWIR) detection in each pixel has been developed in a 384x288x2 format with 40 μm pitch, NETD < 35mK @ F/2, 6,8 ms for both peak wavelengths (4.8 μm and 8.0 μm). The device provides synchronous integration of both bands for temporal and spatial coincidence of the events observed. QWIP dual band or dual color detectors provide good resolution as long as integration times in the order of 5-10ms can be tolerated. This is acceptable for all applications where no fast motions of the platform or the targets are to be expected. For rapidly changing scenes - like e.g. in case of missile warning applications for airborne platforms - a material system with higher quantum efficiency is required to limit integration times to typically 1ms. For this case, several companies work on molecular beam epitaxy (MBE) of MCT to have access to double or multi layer structures. AIM and IAF selected antimonide based type II superlattices (SL) for such kind of applications. The SL technology provides -- similar to QWIP's -- an accurate engineering of sensitive layers by MBE with very good homogeneity and yield. While promising results on single SL pixels have been reported since many years, so far no SL based detection module could be realized. Just recently, IAF and AIM managed to realize first most promising SL based detectors. Fully integrated IDCAs with a MWIR SL device with 256 x 256 pixels in 40 μm pitch have been integrated and tested. The modules exhibit excellent thermal resolution of NETD > 12 mk @ F/2 and 5 ms. The next step will now be to stabilize the technology and to start the development of a dual color MWIR device based on SL technology and the existing 384 x 288 read out circuit (ROIC) used in the dual band QWIP device.

The detailed design of the Target Acquisition/Fire Control (TA/FC) system for the XM29 combat rifle was completed in mid-2003, not long after the system was first presented to the SPIE technical community at the 2003 AeroSense Conference. The system which was described at that time successfully underwent its Critical Design Review. Prototypes were built and tested for the 25-μm pixel pitch uncooled thermal imager, laser rangefinder, display, processor/ballistic computer, environmental sensors and digital compass. Weighing less than 2.6 lbs, the highly integrated package meets both its weight requirement and a projected run time of over 15 hours on a single rechargeable battery, while performing its required mission. In addition the laser rangefinder is expected to operate at twice its required range. This paper provides an update on the final design of the fire control system, the development status and the XM29 program itself.

INO in collaboration with DRDC Valcartier has been involved in the design and development of uncooled IR bolometric detector technology since the early 1990s for a broad range of military and commercial applications. From the beginning, the strategy has been to develop small-size bidimensional detector arrays and specialty linear arrays, both equipped with on-chip readout electronics. The detector arrays have been implemented in various instruments for both imaging and non-imaging applications. This paper describes two TWS1 and TWS2 prototypes of single band thermal weapon sights (TWS) making use of a novel catadioptric, i.e. refractive/reflective, optics and INO's miniature IR cameras. These cameras employ a 160x120 pixel uncooled bolometric FPA with a 52 µm pitch and NETD at 50 mK, and modular electronics consisting of three boards stacked together to fit into a 3-inch cube volume. The ultra lightweight catadioptric objective is inherently athermalized in the -30°C to +40°C range. The TWS1 is also equipped with a miniature RF link allowing bi-directional video transmission. This TWS1 weighs only 900 g and has a total volume of about 75 in³. Its power consumption is 2 W. The experimental performance showed that human detection, recognition and identification could be achieved at 800 m, 200 m, and 120 m, respectively. Construction of an improved TWS2 model is in progress. The objective is the reduction of TWS2 model weight down to 700 g, its volume down to 50 in³, replacing the RF video link with a wireless digital link, and increasing resolution to 320x240 pixels.

The Laboratoire Infrarouge (LIR) of the Laboratoire d’Electronique, de Technologie et d’Instrumentation (LETI) has been involved in the development of microbolometers for several years. Therefore a first generation of a high performance technology made from amorphous silicon thermometer has been transferred to ULIS in 2000 and a second generation has been transferred in 2003 for being able to manufacture small pixel pitch uncooled IRFPA. LETI is still working to improve uncooled IRFPA and two principal research orientations are currently studied. First LETI improves performances of low cost detectors for both military and civil applications. Secondly LETI develops a very low cost packaging technology for high volume applications like automotive. Since packaging operations represent today the most significant part of detectors price, LETI has studied an original on-chip packaging structure less expensive than wafer level packaging structure. Il means, that after standard collective technology of bolometers, the process continues with microcaps manufacturing over the microbolometer or over the array of microbolometers. It requires specific technological developments in order to build this micro-caps and the main difficulty consists in closing hermetically exhausts holes manufactured previously in the caps, while maintaining expected vacuum around the detector. Another difficulty consists in choosing window cap materials and thickness to minimize IR absorption that is crucial for our application. LETI will present status of its developments of this innovating technology and SEM views from the first lab test device.

BAE Systems has made dramatic progress in uncooled microbolometer sensors and applications in the last year. The topics covered in this paper are: results and video from our latest 640x480 FPAs with sensitivities of better than 50 mK (f/1) and overviews of systems for military and commercial applications.

This paper proposes a new thermally isolated pixel structure, having a twice-bent beam structure and eaves structure, suitable for high-resolution uncooled infrared (IR) focal-plane arrays (FPAs). It also describes the properties of test devices, fabricated to verify the effect of the new pixel structure. Although the pixel size of the test devices is 23.5 μm × 23.5 μm, which represents a smaller area by a factor of about 2.5 than the 37 μm × 37 μm pixel size for the 320 × 240 bolometer-type uncooled IRFPA, previously developed by the authors, the test devices have beams with almost the same length as in the previous IRFPA by utilizing the new beam structure. In addition, the cross-sectional area of the beam is reduced. Accordingly, the thermal conductance of the test devices can be reduced by a factor of about 2.5. The eaves structure, which is adopted to increase the fill factor of pixels, improves the responsivity by a factor of 1.3, which is consistent with our calculations. By utilizing the new thermally isolated pixel structure, the test devices with 23.5 μm pixels enable us to achieve thermal sensitivity equivalent to the previous 37 μm pixels.

The 300K background limit is routinely achieved by cryogenic LWIR photon detectors such as Hg_0.795Cd_0.205Te operating at 77K. Will uncooled thermal detectors be able to do so? It appears that only resistive bolometers can. The necessary steps are described. The state-of-the-art of VO_X and a-Si bolometers are compared with theory.

Uncooled microbolometer technology has shown dramatic improvements in recent years as tens of thousands of imaging systems have been delivered. This paper outlines the performance limits that must be overcome to continue to achieve performance improvements.

Substantial activity over the past few years has been devoted to improving the performance of uncooled IR detectors. These efforts have been rewarded by impressive progress in the reduction of pixel size, with sustained further improvements in NETD. Recent bolometer arrays are only a factor of two or three away from the temperature-fluctuation noise limit for current values of thermal isolation, and optimism remains high for further advances. However, essentially all bolometer-based thermal imaging sensors are currently limited by spatial noise, not by temporal noise. Whenever temporal noise is visible on the display of an uncooled IR imager, it is a good bet that spatial noise will be visible as well. Although fixed-pattern noise is an important part of spatial noise, it is not the only part. Spatially coherent temporal noise, 1/f noise, and drift all contribute to degrading sensor performance, and, like fixed-pattern noise, the degradation exceeds the expectation set by simple numerical comparison. These effects degrade imager performance more significantly than an equal variation from truly random temporal noise, because the eye integrates both temporally and spatially to suppress the latter. By including in our analysis a simple model of the eye-brain response we can determine the specifications necessary to suppress these effects so that true background-limited performance can be realized. This paper examines the sources of spatial noise, analyzes the effect on performance, and attempts to set expectations for performance limits. To limit the scope, the analysis is restricted to pulse-biased, current-mode bolometers.

The advent of uncooled thermal imaging has produced an order-of-magnitude reduction in the cost of thermal imaging compared to first-generation cooled systems. To reach a truly mass market, this process needs to be continued. One of the key cost constraints is the specialist nature of the sensitive material used in infrared detectors. This paper describes thermal imaging technology which can be entirely manufactured in a silicon IC foundry on a standard CMOS process. As a result the detector cost in volume production is extremely low. Careful optimisation of the other system components such as packaging, optics, and signal processing maintains this low-cost approach, giving a predicted production cost well below $100.

One common requirement of microbolometers fabricated on both rigid and flexible substrates is the need for vacuum packaging to eliminate the thermal conductivity of air and achieve high performance. However, vacuum packaging of microbolometers is expensive and is a limiting factor in achieving truly low-cost uncooled infrared detection. Vacuum packing of microbolometers on flexible substrates requires a novel approach unless flexibility is to be sacrificed. This paper explores the vacuum packaging of microbolometers through self-packaging. In this case, the micromachined encapsulation in a vacuum cavity is investigated through computer simulation of microbolometers in flexible polyimide films and through the encapsulation of microbolometers on rigid Si substrates with a Si₃N₄ shell. In this manner, self packaged uncooled microbolometers were fabricated on a Si wafer with semiconducting yttrium barium copper oxide (YBCO) as the infrared sensing material. The self-packaged structure is designed such that it can be covered with a superstrate, yielding low stress in the flexible skin sensors and better detection figures of merit. The devices have demonstrated voltage responsivities over 10³ V/W, detectivities above 10⁶ cm Hz^1/2/W and temperature coefficient of resistance around -3.3% K^-1. Computer simulations using CoventorWare and MEMulator have been used to determine suitable materials for the process, the optimum design of a vacuum element and a streamlined process flow.

Thales Angenieux has been developing for almost two decades, compact and flexible light intensifier goggles that are in service through numerous countries. More recently, a new product line, called Elvir, has been launched which is based upon uncooled sensitive arrays: as a consequence, Thales Angenieux has now at command a full set of night vision equipment's, answering most of the operational purposes. A 'blocks' policy has been used to cut the non-recurring expenses: the thermal camera re-uses some upgraded sub-assemblies of the previous IL goggles. This paper reviews the main trades off, showing how we relied on earlier and successful designs to meet the best compromises between performances, costs and compactness. Some issues, such as the front infrared optics set up, will be emphasized later on. The choices that have ruled the visualization unit design will be outlined. Future prospects backing the latest technologies breakthroughs wil be sketched out: topics such as new infrared materials and hybrid lenses made of subwavelength features are addressed.

Pixel scaling for SOI diode uncooled infrared focal plane arrays (IRFPAs) was investigated in order to achieve the realization of small size and low cost IRFPAs. Since the SOI diode pixel has two different layers -- one for the temperature sensor and the thermal isolation structure, and the other for the infrared absorption structure -- each layer can be independently designed. Hence, a high fill factor can be maintained when reducing pixel size without changing the basic structure of the pixel, which is advantageous in reducing the pixel size. In order to verify this, the authors have developed an SOI diode IRFPA with the pixel size of 28 μm x 28 μm which is 49% of the previous pixel size (40 μm x 40 μm) and achieved a noise equivalent temperature difference (NETD) of 87 mK. In order to further reduce the pixel size and to improve device sensitivity, we propose a new pixel structure. In this structure, a reflector is fabricated between the infrared absorption structure and support legs. Therefore, the infrared rays which are incident on the support legs, which do not sufficiently function as a reflector, can be used effectively. A new pixel structure with a pixel size of 25 μm x 25 μm was fabricated and realized the thermal conductance of 1.0 x 10^-8 W/K and the infrared absorption structure was then verified for its effectiveness.

DRS has developed and demonstrated a family of miniaturized, low-power uncooled infrared focal plane camera products integrated with our 1-mil pixel size 640 x 480 and 320 x 240 uncooled infrared focal plane arrays (UIRFPA). The UIRFPA cameras operate from -40°C to +55°C without UIRFPA temperature regulation using our patented TCOMP sensor concept. Furthermore, they are software based, with significant memory and signal processing overcapacity, which supports significant camera setup reconfigurations without having to undergo camera firmware and hardware modifications. The elimination of the UIRFPA temperature regulation requirement results in reduced sensor power and prompt sensor turn-on. The new 320 x 240 camera weighs less than a quarter pound (including batteries and a 23 mm aperture F/1.2 optic), and dissipates approximately one watt when operated at a full 60 Hz frame rate. The 640 x 480 camera dissipates about two watts when operated at a TV compatible 30 Hz frame rate. This paper describes the UIRFPA camera products, their features and capabilities, and their key performance characteristics. Illustrative examples of thermal image quality are also included.

Raytheon is producing high-quality 320 x 240 microbolometer FPAs with 25 μm pitch pixels. The 320 x 240 FPAs have a sensitivity that is comparable to microbolometer FPAs with 50 μm pixels. Typical NETD values for these FPAs are <50mK with an f/1 aperture and operating at 30 Hz frame rates. Pixel operability is greater than 99.9% on most FPAs, and uncorrected responsivity nonuniformity is less than 4% (sigma/mean). These 25 μm microbolometer detectors also have a relatively fast thermal time constant of approximately 10 msec. These arrays have produced excellent image quality, and are currently fielded in a variety of demonstration systems. The pixel size reduction facilitates a significant FPA cost reduction since the number of die printed on a wafer can be increased, and also has enabled the development of a large-format 640 x 480 FPA array. Raytheon is producing these arrays with excellent sensitivity and typical NETD values of <50mK with an f/1 aperture and operating at 30 Hz frame rates. These arrays have excellent operability and image quality. Several dual FOV prototype 640 x 480 systems have been delivered under the LCMS and UAV programs. RVS has developed a flexible uncooled front end (UFE) electronics that will serve as the basis for the camera engine systems using 320 x 240 arrays. RVS has developed a 640 x 480 Common Uncooled Engine (CUE) which is intended for small pixel, high performance applications. The CUE is the ideal cornerstone for ground and airborne systems, multi-mode sensor, weapon sight or seeker architectures, and commercial surveillance.

Thermal weapon sights have been used by the U.S. military for decades. More recently, there has been a growing interest in infrared imagers for paramilitary and civilian applications such as law-enforcement and homeland defense. However, traditional weapon sights are not always ideal products for these applications because they do not typically have form-factor or features allowing them to be readily employed as general-purpose imagers off the weapon. Simply stated, most law-enforcement agencies cannot afford a dedicated sniper scope. Instead, this market demands a thermal imager that can be employed in a variety of situations, both weapon-mounted and handheld. Described herein is a new infrared sight that provides this multi-use capability. Based around the Omega imaging core developed by Indigo Systems, this lightweight system employs a unique housing design that mounts to a weapon rail or tripod or is held comfortably in one hand for use as a short-range “pocket scope”. Key aspects of the design are discussed, with particular focus on ergonomics, human factors, and advanced features that enhance its utility in a multi-use role.

Uncooled infrared focal plane arrays are being developed for a wide range of thermal imaging applications. Developments are focused on the improvement of their sensitivity, enabling the possibility of reducing the pixel pitch in order to decrease the total system (size and weight) by using smaller optics. The amorphous silicon technology is the latest one developed by CEA/LETI and transferred to ULIS to manufacture uncooled infrared 2D arrays. We developed for this device a low cost package based on existing technologies. This device is well adapted to multipurpose high volume applications where spatial resolution (in term of pixel number) is less important than device costs.

Indigo’s emergence as a production source of uncooled microbolometers was reported in the SPIE proceeding in 2003. With now over a year of modest volume production history on the small-format FPAs, the details of the production experiences are reported. Progress on the mid-format arrays is discussed as are the efforts towards large-format, small pixel devices. Also discussed is the status of the production ramp that will lead to the supply of uncooled FPAs into the automotive market.

In this paper, the fabrication of microbolometers with electronically controllable responsivity is presented. The first generation devices are built in a standard polysilicon-based micromachining process with HF etch-release and demonstrated with a responsivity that can be tuned over a factor of 50. The responsivity is controlled by applying a voltage between the microbolometer and the substrate. The resulting electrostatic force causes a small portion of the support beam to contact the substrate, which thermally shorts the device at that point. The thermal contact points are defined using curved support beams with residual-stress from a Cr/Au metallization. The lowest portion of the beams contacts the substrate, and the curvature protects the device from full “snap-down,” which might induce stiction. The fabrication of the second generation microbolometers based on VO_x and silicon nitride materials with a polyimide etch-release is also described. The thermal contact points for these devices are defined by beam mechanics rather than by beam curvature induced by stress, and they actuate at 17 volts. The test array has a fill-factor of 91% for a pixel period of 140μm limited by our photolithography equipment.

With the variety of advanced payloads available in E/O systems, operators can easily become confused or overwhelmed with the amount of data available to them. FLIR systems has taken the approach of backing sensor applications with advanced signal processing and control systems to reduce the data set to relevant information and reduce operator workload. Architectures are discussed for signal processing and implementations with FPGA and DSP chips are compared and contrasted. Three signal processing case studies are covered in detail: autofocus, haze penetration and image blending.

The U. S. Army Research Laboratory (ARL) is investigating visible and infrared impact flash signatures of kinetic energy and other munitions. The effort has two phases; one examines the detailed spectral and photometric characteristics of flash from controlled impacts at indoor ranges and is intended to provide a detailed, systematic database about impact signatures, while the second gathers similar impact signatures of U.S. rounds striking potential opponents’ vehicles in the field. In both cases, the signatures are subsequently correlated with high-speed photography and the physical damage created. The results indicate that with minor modifications of basic KE rounds, flash signatures may have the potential to reveal who fired a round and whether it struck, penetrated, or even perforated the target.

Hyperspectral imaging in the 2-5 um band has held interest for applications in detection and discrimination of targets. Real time instrumentation is particularly powerful as a tool for characterization and field measurement. A compact, real-time, refractive MWIR hyperspectral imaging instrument has been designed and is undergoing integration and test. The system has been designed for cryogenic operation to improve signal to noise ratio, reduce background noise, and enable real-time hyperspectral video processing. Partial testing has been completed on cryogenic elements and “first light” 2-5 μm hyperspectral images have been collected at room temperature.

A small, hand held, battery operated imaging infrared spectrometer, Sherlock, has been developed by Pacific Advanced Technology and was field tested in early 2003. The Sherlock spectral imaging camera has been designed for remote gas leak detection, however, the architecture of the camera is versatile enough that it can be applied to numerous other applications such as homeland security, chemical/biological agent detection, medical and pharmaceutical applications as well as standard research and development. This paper describes the Sherlock camera, theory of operations, shows current applications and touches on potential future applications for the camera. The Sherlock has an embedded Power PC and performs real-time-image processing function in an embedded FPGA. The camera has a built in LCD display as well as output to a standard monitor, or NTSC display. It has several I/O ports, ethernet, firewire, RS232 and thus can be easily controlled from a remote location. In addition, software upgrades can be performed over the ethernet eliminating the need to send the camera back to the factory for a retrofit. Using the USB port a mouse and key board can be connected and the camera can be used in a laboratory environment as a stand alone imaging spectrometer.

Mosaic technology has gained considerable popularity and has become mainstay in commercial digital color cameras. In a mosaicked sensor, each pixel detector is covered with a wavelength-specific optical filter. Since only one spectral band is sensed at each pixel, the other bands must be estimated from neighboring pixels. In the commercial digital color cameras, sophisticated algorithms have been developed to perform this estimation, based upon properties of the human visual system to minimize artifacts. To expand this technology for use in military applications such as missiles and smart ordnance, various modifications need to be made. Two of the bigger problems are the choice of spectral sensitivities for the filters and the pattern used in the mosaic. We propose a novel seven-band setup for multispectral imaging systems along with a choice of spectral sensitivities that "best" distinguish target from clutter in an information theoretic sense. These ideas are illustrated with hyperspectral visible/near-infrared images taken by the AVIRIS sensor. Following the image-capture stage, the display of these multispectral images on a three-channel display is also addressed.

A new family of light handheld military thermal imagers for reconnaissance and targeting applications was developed based on AIM's IR components like IR detection modules, command and control electronics and image processing units. Three different types of imagers provide solutions for different requirements in identification ranges of targets. The highest performance device makes use of a FPA MCT 384x288 MWIR detector with a motorized double field of view optics. An identification range up to 2400m for the NATO standard target was proven according to the FGAN-FOM TRM3 range model. The device provides a mechanical adaptation to weapon systems and provides target markers for common hand weapons of the German army. A single field of view MCT device for 1000m ranges and an uncooled device on the lower performance end complete the imager family. Electronics for intelligent power management from batteries and display electronics were developed to provide stand alone operation. The modular concept allows the use of the same image processing unit for all devices providing special features for best performance like scene-based non-uniformity correction together with an optical calibration element and dynamic reduction including automatic histogram equalization for optimized scene display and text or graphics overlay. Due to the modular concept the components like the image processing unit are already used and validated in programs like the thermal sight for the self defense gun of the reconnaissance vehicle FENNEK together with a 320x240 LWIR uncooled microbolometer detector or with the MCT 384x288 MWIR detection module in a thermal imager for the German army UAV Luna.

This paper first briefly describes the Laser Detection and Reciprocal Targeting (LDART) system being developed under the DARPA NEST program, whose purpose is to detect and locate enemy target designators. The system's sensor is an array of microelectronic (MEMS) detectors, each of which can measure the directional angle of incident light with a random error, whose distribution is known. The detector errors cause the sensor to perceive the source as if in a location that is generally different from its actual location. The paper's main contribution is to show how to optimally estimate the actual laser source location. We derive the probability distribution of perceived locations and show how it depends on both the source and sensor parameters. The distribution is then used to develop the maximum likelihood estimator of the actual source location, which allows to pinpoint the source with very good precision in spite of noisy measurements furnished by individual detectors.

An infrared signal or a laser beam propagating along a horizontal near-surface path will encounter substantial perturbations. The fluxes of momentum and heat near the surface are relatively large, and these in turn cause large changes in the propagated intensity, direction, and coherence. It is important to be able to accurately model the separate effects that generate changes in a propagated beam, and it is also important to combine the different factors accurately. We will present some evidence from field experiments to demonstrate how refractivity changes on a ten-minute scale are manifested in a recorded infrared transmission signal. The EOSTAR (Electro-Optical Signal Transmission and Ranging) model is used to provide performance predictions for the experimental work. The EOSTAR model is built upon a geometrical optics approach to infrared propagation: a ray is traced through the propagation environment, and path-dependent perturbations to the signal can be determined. The primary computational tool for analysis of refractive effects in the EOSTAR model is a geometrical optics module that produces a ray-trace calculation for a given refractive environment. Based on the vertical profiles of temperature, humidity, refractive index structure parameter, and the calculated ray trajectories, EOSTAR calculates the path-integrated and spectrally-resolved transmission, background-radiation and path-radiation, as well as the scintillation and blur for a point source at any range and height position.

Programs at Nova Biomimetics have led to the design and development of a set of miniature electronics to be used for the application of a wide variety of point- and area-type mathematical operations to be applied in real time to the digital data produced by a variety of real-time digital video camera systems. Nova is planning to market these electronics in partial satisfaction of Small Business Innovation Research (SBIR) Program dual-use commercialization requirements.

This paper describes the design, growth and fabrication characterization of novel multi-wavelength QWIP wafers based on InP material systems. We designed, grew, fabricated and characterized AlGaInAs/GaInAs QWIPs suitable for operation at 3-5 μm, and 8-12 μm spectral range. We fabricated mid-wave IR 320 x 250 focal plane arrays, hybridized them with Si -readout circuits and performed radiometric and imaging tests. Excellent imaging results of the mid-wave IR focal plane arrays with an operability of 88% and mean NEDT of 0.09K have been achieved. To our knowledge, this is the first imaging with InP based QWIPs focal plane array.

A mid-wavelength 1024x1024 pixel quantum well infrared photodetector (QWIP) focal plane array has been demonstrated with excellent imagery. Noise equivalent differential temperature (NETD) of 19 mK was achieved at 95K operating temperature with f/2.5 optics at 300K background. This focal plane array has shown background limited performance (BLIP) at 90K operating temperature with the same optics and background conditions. In this paper, we will discuss its performance in quantum efficiency, NETD, uniformity, and operability.

Corrugated quantum well infrared photodetectors (C-QWIPs) offer simple detector architecture for large format infrared focal plane arrays. The detector relies on inclined sidewalls to couple normal incident light into the absorbing material. In this work, we describe the light coupling characteristics of C-QWIPs based on a simple geometrical-optics model and a rigorous modal transmission-line model. Based on these two theoretical models, we optimize the detector structure toward a large quantum efficiency η. In addition, we investigated material structures that give both high photoconductive gain and large spectral bandwidth. Combining these two material properties with a large η offered by the corrugated structure, the detector photocurrent can be greatly increased, which will be useful in high speed infrared imaging.

We investigated the mechanism of the photocurrent transmission in mid-wavelength quantum-well infrared photodetectors that were made using InGaAs/AlGaAs quantum wells so that their peak absorption would be at a wavelength near 5 μm. Analyzing the bias-voltage dependence of the photocurrent for the samples with different well layer thicknesses, we found that the photocurrent transmission could be accounted for by taking into account the tunneling process via the triangular barrier, the effect of the intrinsic electric field due to the unintentional impurities, and the effect of the drift velocity.

In recent years quantum well infrared (IR) photodetector (QWIP) focal plane array (FPA) technology has developed to the point where it may be considered a candidate for insertion into 3rd generation FLIR systems. Both large format (1024x1024 pixels) and multicolor (MWIR/LWIR and LWIR/LWIR) FPAs have been produced using QWIP technology. We report on the application of these new FPAs to the challenges facing today's military. These include the collection of signatures of buried land mines with a LWIR/LWIR dual-color QWIP and long-range target detection/identification using a 1024x1024 FPA. The FPAs were produced from several sources. Large format LWIR FPAs were made by an ARL/NASA/Rockwell team using ARL’s C-QWIP optical coupling scheme. Another large-format FPA was obtained from QWIP Technologies, Inc. and is commercially available. The dual-color LWIR/LWIR FPA was produced by BAE Systems. Laboratory and field imagery from both types of FPAs are presented and analyzed.

Following on the success of the BIRC clip on thermal imaging sight for the BILL Anti-Tank Missile System, which was in fact the world's first military QWIP based thermal imager, and which has been successfully delivered to the Swedish Army in serial quantities, several new QWIP-based products from FLIR Systems AB in Sweden are now under contract for defense customers worldwide. These include the new Forward Observation Systems for Norway and Sweden, Airborne Search & Rescue Systems, and a new clip on thermal imager for the Bofors RBS 70 Air Defense Missile System. The latest of these products is the development of a High Resolution QWIP Thermal Imager, LIRC, under contract for an upgrade of a number of Swedish CV9040C Armored Fighting Vehicles for Swedish Army International Operations. The paper will focus on the rationale behind the system selection, the development of the military qualified QWIP Thermal Imagers and the current status of the program.

Standard GaAs/AlGaAs Quantum Well Infrared Photodetectors (QWIP) are coming out from the laboratory. In this presentation we demonstrate that production and research cannot be dissociated in order to make the new generation of thermal imagers benefit as fast as possible from the building blocks developed by researchers. Since 2002, the THALES Group has been manufacturing sensitive arrays using QWIP technology based on AsGa techniques through THALES Research and Technology Laboratory. This QWIP technology, integrated in IDDCA built by Sofradir, allows the realization of large staring arrays for Thermal Imagers (TI) working in the IR band III (8-12 μm). A review of the current QWIP products, offered by Sofradir, is presented. In the past researchers claimed many advantages of QWIPs. Uniformity was one of these and was the key parameter for the production start. Another advantage widely claimed also for QWIPs was the so-called band-gap engineering, allowing the custom design of quantum structure to fulfill the requirements of specific applications like very long wavelength or multispectral detection. In this presentation, we present the performances for Middle Wavelength InfraRed (MWIR) detection and demonstrate the ability of QWIP to cover the two spectral ranges (3-5 μm and 8-20 μm). At last but not least, the versatility of the GaAs processing appeared for QWIPs as an important gift. This assumption was well founded. We give here some results achieved on building blocks for two color QWIP pixels. We also report the expected performances of focal plane arrays we are currently developing with the CEA-LETI-SLIR.

A test bench has been developed at ONERA in order to measure the spectral responses of infrared focal plane arrays (IRFPAs). This test bench can deliver hyperspectral cartographies with rather good resolutions (better than 16 cm^-1) on large spectral ranges (from 1.3 μm to 20 μm). The principle of this test bench will be described. Using this technique, tests have been performed on a large format (640x512) IRFPA of quantum-well technology operating in the 8- to 10-μm spectral range. The prototype tested had several small defects that produce spectacular hyperspectral cartographies. To explain the hyperspectral structures observed across the array, an empirical model based on Fourier optics will be presented.

For the past 18 years Carleton Life Support Systems has produced over 15,000 tactical cryogenic coolers that are primarily used in military infrared systems with excellent demonstrated reliability. As system reliability has improved, the cooler performance has emerged as a dominant component for reliability predictions. This has driven cooler reliability requirements to increase from a 1500-hour rotary cooler in chiefly ground applications to current requirements of 20,000 hours for linear coolers in advanced airborne applications. At the same time there is a push for improved cooldown time, lower power, lighter weight and smaller package. This paper reviews our progress on extending cooler life. It reviews recent product returns and contends that the majority of issues are not primarily related to reliability. It also reviews how system performance specifications are restrictive to the cooler designer in achieving higher reliability in tactical coolers.

Low vibration Stirling cryocoolers, which find use in numerous vibration sensitive electronic and electro-optic applications, typically comprise a dual-piston linear compressor and a pneumatically driven expander. While such compressors have inherently low level of vibration export, the unbalanced motion of the displacer-regenerator of the traditional expander inevitably leads to an essential vibration export into the supporting structure to which the cryogenic cooler is normally rigidly attached. The authors report on the novel approach to a passive cancellation of vibration export from a pneumatically driven displacer of a split Stirling cryogenic cooler. This patent pending technique relies on the principle of dynamic counterbalancing, where an auxiliary movable mass is flexibly attached to a hot part of the movable displacer-regenerator assembly and to the stationary expander casing using two auxiliary mechanical low-damped springs. A theoretical analysis yields the simple condition of canceling the fundamental component of vibration export at the same power consumption and cooling performance. The authors successfully attempted to redesign the existing expander of the Stirling Ricor model K535 cryocooler, where the vibration export at the driving frequency was reduced 150-fold under typical thermal loading at the same power consumption.

Several thousands of 1st Gen IR Systems operated by Integral Stirling Cooler HD1033 are still in service worldwide. Replacing the HD 1033 Stirling by a Linear Drive Cooler will result in a significant reliability enhancement of these IR system of about a factor of three. These attempts had been unsuccessful in the past due to excessive EMI noise induced by the linear cooler compressor. So a main goal for such a development is the elimination of various EMI distortions in the IR system by EMI filtering and shielding. Additionally, the synchronization of the cooler power to the predominant scanning frequency of the IR system significantly improves the image quality. Technical details of the solution, MTTF data and performance data are described in detail.

Numerous military thermal imagers operating under hostile environmental conditions rely on tactical rotary split Stirling cryocoolers, the pneumatically driven expanders of which are known to be the source of considerable vibration export. The cold tip temperature in such a cooler is typically stabilized by controlling the driving frequency in accordance with thermal loading and ambient temperature, leading to a frequency-swept harmonic vibration export into the optomechanical structure of the thermal imager. The active vibration cancellation systems are basically capable of suppressing such vibration, but are still quite bulky, complicated and expensive. In this paper, the authors report on the recent efforts towards developing a low cost vibration counterbalancer for a pneumatically driven expander in a rotary cryogenic cooler. In this approach, the flexurally suspended auxiliary mass - counterbalancer - is arranged to oscillate coaxially with the expander’s displacer and is driven pneumatically by the pulses of the working fluid produced by the compressor. Based on the results of analytical modeling and Sage optimization, the counterbalancer was designed and manufactured as an integral part of such an expander. The full-scale experimentation has shown essential cancellation of vibration export within the working frequency range from 30 to 60Hz without noticeable effect on cryocooler performance.

In the mid-1990's, DRS Infrared Technologies began an effort to extend the application of flexure spring technology into cryogenic coolers being supplied for tactical military applications. Previous papers have explored the design challenges and reported performance, life, and environmental testing results. In addition, DRS has now extended the flexure spring design into cryocoolers designed to operate in high ambient temperature ranges previously deemed too severe for linear drive cryocoolers. This paper discusses the design considerations that must be addressed at these high temperatures. Performance and test results for one such cooler, designed for a U.S. Navy threat warning sensor, with cryocooler case temperatures of 120°C, are presented.

As far as calibrated radiometric imaging is concerned, a complete prediction of oblique incidence effect on the FPA pixels’ response is required. Since a light coupling scheme needs to be used in QWIP detectors, this effect is particularly complicated to understand. This article presents two complementary test benches which allow to quantify the effect of oblique incidence on cooled infrared detectors issued from different technologies. The first test bench performs measurements over a wide angular range with low background emission levels, but gives spectrally integrated measurements. The second one delivers spectrally resolved responses for incident angles lower than 30°. In order to validate both experimental concepts, we studied QWIPs equipped with 2D periodic gratings. Relatively large pixels (100x100μm²) were chosen to ease comparison with models. Calculations based on the modal expansion method reveal that diffraction off an infinite grating does not account very well for the observed spectral responses.

Surface treatment is one of the key issues for fabricating long-wavelength infrared (LWIR) detectors having good performance. In this paper, a novel surface treatment using hydrazine has been proposed for HgCdTe and its validity has been confirmed with ellipsometry and C-V analysis. The fixed charge density and trap oxide charge density of hydrazine-treated sample have shown so small value of 1.29×10⁹ cm^-2 and 4.35×10¹⁰ cm^-2, respectively, comparing with those obtained with the conventional Br-MeOH-treated sample. In addition, the hydrazine-treated sample has shown high frequency characteristic in the C-V curve, which means the large effective minority carrier lifetime on the surface. By applying the new surface treatment using hydrazine to vacancy-doped wafers, LWIR photodiodes have been successfully fabricated. Current-voltage (I-V) characteristics of the hydrazine-treated Hg_0.77Cd_0.23Te diodes were also measured. Average R₀A products of these diodes with the junction area of 30x30 μm² were about 2.54 Ωcm², which satisfy 95% BLIP (background limited infrared photodetector) condition for LWIR photodiodes.

Multispectral imaging is a well accepted technique for object discrimination. Hyperspectral imaging can result in highly complex optical systems that have frame rate limitations. For fast frame rate applications, dual band imaging can provide sufficient discrimination without sacrificing signal to noise ratio. The design of a fast frame rate (> 200 Hz) SWIR/MWIR and MWIR/LWIR camera is described. Two strategies for cooling the array are explored.

This paper describes the set-up and the essential features of pyroelectric single-element detectors on the basis of lithium tantalate (LiTaO₃). They have been developed for special applications in pyrometry, analytics and security techniques and are optimized for a maximum possible signal-to-noise ratio. Important detector characteristics (responsivity, specific detectivity) and of disturbances (acceleration sensitivity) as a function of the chopper frequency and the detector layout can be theoretically calculated on the basis of various mathematical and physical models. The latter take particular account of the thermal, electric, mechanical and optical conditions in the sensor. It is shown that the specific detectivity of the components can be essentially increased by using selected components (low-noise SFET, inert gas) for the detector and by applying various technologies for the manufacturing of the responsive element for certain chopper frequencies. For example, a specific detectivity of D* (500 K; 10 Hz; 1 Hz; τ_F = 1) ≥ 1.5 x 10⁹ cmHz^1/2W^-1 has been obtained for LiTaO₃ detectors with a responsive area of [3x3] mm². Moreover, the acceleration sensitivity could be reduced by choosing special chip and detector layouts. As a result, this paper confirms a good correspondence between the measured and calculated values of the detector characteristics. This paper also presents innovative detector designs (integrated optics, three-dimensionally structured LiTaO₃ chips) and their basic properties.

A dual band camera for long-range airborne reconnaissance has a large common Cassegrain objective, a beam splitter, VNIR and MWIR channels. Non-uniformity correction (NUC) must be especially accurate in this type of application, due to the low dynamic range of a raw image acquired through tens of kilometers of atmosphere. Accurate calibration of non-uniformity in the MWIR band represents a challenge, because of considerable emissivity of the optics, variable optics temperature, high cos⁴ effect, vignetting, complex focal plane geometry, residual misalignment between the exit pupil and the dewar's cold stop, and insertion of a blackbody temperature reference source (TRS) directly in front of the dewar window. The paper describes a special calibration method which overcomes the complexities and achieves high NUC accuracy. The method combines in-laboratory transmissibility measurement with two-stage in-flight periodic calibration. The detector non-uniformity is calibrated in wide signal range. The TRS temperature follows a curve giving linear rise of radiance in time. Inner surface of the pod between the optical windows is used as a uniform source for evaluation of a pattern caused by the optics radiation. This method was successfully implemented in the ElOP long-range oblique photography (LOROP) camera.

Uncooled bolometric detectors used in infrared imaging systems have slow time constants (~10 ms) which makes them impractical for fast-frame-rate applications. Antenna-coupled microbolometers are fast uncooled detectors with good sensitivity, directivity and can be polarization and wavelength selective. These detectors have collection areas in the order of 10 μm² which are too small for infrared imaging systems where a typical pixel area ranges from 20 × 20 μm² to 50 × 50 μm². In this paper two different types of detectors that can cover a typical pixel area are fabricated and their performance measured. The first type of IR pixel is a two-dimensional array of serially connected antenna-coupled microbolometers. These arrays can cover any pixel area and increase the signal-to-noise ratio of a single detector by a factor of N for an N×N array. The second IR pixel was fabricated by using a Fresnel Zone Plate Lens (FZPL) to collect and focus energy to a single antenna-coupled detector. An FZPL-coupled detector of 200 µm in diameter showed a 2× increase in D* compared to single element detectors. An 8 × 8 array of antenna-coupled pixels were fabricated on a commercial ROIC, measurements made on this antenna-coupled infrared focal plane array showed that the integration of antenna-coupled detectors to a commercial ROIC is possible.

Emergency Responders (Fire, Police, Medical, and Emergency Management) face a high risk of injury or death. Even before September 11, 2001, public and private organizations have been driven to better protect Emergency Responders through education, training and improved technology. Recent research on Emergency Responder safety, health risks, and personal protective requirements, shows infrared (IR) imaging as a critical need. Today’s Emergency Responders are increasingly challenged to do more, facing demands requiring technological assistance and/or solutions. Since the introduction of Fire Service IR imaging in the mid 1990s, applications have increased. Emergency response IR is no longer just seeing through smoke to find victims or the seat of a fire. Many more mission critical needs now exist across the broad spectrum of emergency response. At the same time, Emergency Responder injuries and deaths are increasing. The Office of Domestic Preparedness (ODP) has also recognized IR imaging as critical in protecting our communities -- and in preventing many of the injuries and deaths of Emergency Responders. Currently, only 25% of all fire departments (or less than 7% of individual firefighters) have IR imaging. Availability to Police, EMS and Emergency Management is even lower. Without ERCI, Emergency Responders and our communities are at risk.

High temperature diffusion of Cu into GaAs was used to prepare infrared filters for the 8 - 13 μm atmospheric transmission window. Copper was evaporated to thickness ~ 100 nm on both sides of double-side polished 1.7 mm thick GaAs samples, then sealed in evacuated quartz ampoules back filled with 250 torr of helium. The ampoules were heated at temperatures between 600 C and 1200 C for periods of 15 min to 16 hours, and then quenched in water. Infrared spectra were collected using a Fourier spectrometer at 1.7 K - 20 K sample temperature, 500 to 3500 cm^-1 spectral range, and 1 cm^-1 resolution. The well known Cu:GaAs sharp-line absorption spectrum was observed near 1200 cm^-1 together with a strong photo-ionization band at higher wave numbers. The latter provides zero transmission for wavelengths shorter than 8 μm. The sharp cut-off shifts to longer wavelengths as diffusion times and temperature increase. This process allows for the simple preparation of infrared long pass filters. The concentration profile was modeled to better understand the relation between Cu concentration and spectrum.

This contribution presents a rapid prototyping approach for the real-time demonstration of image processing algorithms. As an example EADS/LFK has developed a basic IR target tracking system implementing this approach. Traditionally in research and industry time-independent simulation of image processing algorithms on a host computer is processed. This method is good for demonstrating the algorithms' capabilities. Rarely done is a time-dependent simulation or even a real-time demonstration on a target platform to prove the real-time capabilities. In 1D signal processing applications time-dependent simulation and real-time demonstration has already been used for quite a while. For time-dependent simulation Simulink from The MathWorks has established as an industry standard. Combined with The MathWorks' Real-Time Workshop the simulation model can be transferred to a real-time target processor. The executable is generated automatically by the Real-Time Workshop directly out of the simulation model. In 2D signal processing applications like image processing The Mathworks' Matlab is commonly used for time-independent simulation. To achieve time-dependent simulation and real-time demonstration capabilities the algorithms can be transferred to Simulink, which in fact runs on top of Matlab. Additionally to increase the performance Simulink models or parts of them can be transferred to Xilinx FPGAs using Xilinx' System Generator. With a single model and the automatic workflow both, a time-dependant simulation and the real-time demonstration, are covered leading to an easy and flexible rapid prototyping approach. EADS/LFK is going to use this approach for a wider spectrum of IR image processing applications like automatic target recognition or image based navigation or imaging laser radar target recognition.

In many applications of camera systems such as for surveillance a combination of a large field-of-view (FOV) with a high spatial resolution is desirable. Classical focal plane array (FPA) cameras can only fulfill this requirements with a very large number of pixels. We present a novel method to enlarge the FOV of a camera equipped with an FPA keeping the spatial resolution of the system untouched. Four images taken at different directions of the line of sight (LOS) are stitched together to a large image resulting in a significantly enlarged FOV in both directions. For this purpose two continuously rotating scan elements are placed in front of the optics which move the LOS with a highly non-uniform scan velocity. Image exposure is triggered when the scan velocity is almost zero. The influence of the residual LOS-movement to the image blur is controllable by various parameters of the system. We present the results of the simulation for an enlarged FOV with 584 x 488 pixels obtained with a scanned infrared FPA of 384 x 288 pixels working in the 3-5μm regime. The resulting system modulation transfer function (MTF) is calculated and the correlation of system performance parameters with the design parameters of the scanner is discussed.

Near infrared detectors in the 1 to 2.4 μm spectral range are important for many applications such as atmospheric remote sensing, where several species have strong absorption spectra in that range. Antimonide-based III-V compound semiconductor materials are good candidates for developing detectors in that spectral range. Electrical and optical characteristics of In_1-xGa_xSb p-n photodetectors at different temperatures are presented. The devices were fabricated either on bulk InGaSb substrates by zinc diffusion or InGaSb epitaxial layers grown on GaSb substrates by organo-metallic vapor phase epitaxy (OMVPE). Variable area devices were fabricated. Current-voltage measurements indicated higher dark current in InGaSb devices grown on GaSb substrate, due to defects generated by the lattice-mismatch. Spectral response measurements were obtained in the 1 to 2.4 μm wavelength range at different temperatures. At room temperature, the cut-off wavelengths were observed at 2.3 and 2.1 μm for InGaSb devices grown on GaSb and for devices fabricated on bulk InGaSb substrates respectively. Reducing the operating temperature shifts the cut-off wavelength to shorter values and increases the responsivity. Noise calculations indicated a room temperature detectivities of 3.3x10¹⁰ and 5.5x10¹⁰ cmHz^1/2/W at 2 μm for the GaSb and InGaSb respectively. Detectivity variation with wavelength will be presented and compared to the background limited performance.

A frequency selective surface (FSS) is designed and fabricated to resonate in the infrared. This IR FSS is designed using Periodic Method of Moments (PMM) software and is based on circuit-analog resonance of square loop conducting elements. The FSS is fabricated via electron beam lithography. The spectral characteristics of this surface are studied in the mid-infrared employing a spectral radiometer. The IR FSS may operate as an emissive narrowband source or reflective bandpass filter centered at a wavelength of 6.5μm, sharply cutting off short wavelength radiation and gradually filtering longer wavelengths. The addition of a superstrate layer, intended to further shape the FSS spectral signature, is also studied and the results discussed.

A 1D IR lock-in focal plane array (FPA) for extremely weak signal imaging has been demonstrated. The experimental system consists of an object with modulated image signal, a high speed InGaAs linear photodetector array as receiver, a CMOS lock-in linear array read-out circuit, and a focal plane array test system. The system can detect extremely weak signals immersed in strong background. Preliminary test shows that under room temperature each of the pixels in the 1D lock-in FPA can read out modulated signal 5 orders smaller than the background. The InGaAs detector array response is from 0.8 μm to 1.6 μm (peak at 1.2 μm). The lock-in array read-out circuit uses a correlated multi-cycle integrator, which can operate in several modes such as gated integration, and phase-sensitive integration with background subtraction. The 1D lock-in FPA works as a pixel to pixel lock-in amplifier, wherein very small signals may be extracted from a much strong background if the frequency of the illuminating source (usually IR light sources) is known. Simulation results are also reported. Experimental results based on an IR illuminating source are demonstrated.

This paper concludes the large effort sustained by OPGAL in designing a radiometer instrument based on the uncooled microbolometer detector. A detailed description of the design considerations, temperature drift model and the expected accuracy is presented. The idea is to enable temperature measurement at a relatively high accuracy for any uncooled microbolometer based FLIR, even if the detector is not a radiometric one, by using the NUC flag as an extremely low frequency chopper.

This paper covers the development of 2 new major cameras in the defence product line, the JADE LR and the RUBY. Test Flight centers nowadays require 24h/day capability to in tracking fast and/or far targets such as fight aircraft, missiles or battle ships. Furthermore, radiometric measurements might be requested by the customer, requiring ability to sort out and process digital images. The JADE LR will be described in the first section of this paper. Based on uncooled technology, the RUBY light handheld infrared imager has been designed with in mind to enhance all weather capabilities for police and paramilitary task forces. Performances and innovative architecture will be discussed in section 2.

To improve its capacity to meet customer needs, DRS Infrared Technologies began technology transfer of the VOx uncooled FPA process from its Anaheim facility to its Dallas facility in the Fall of 2002. The new facility delivered its first U3000 arrays (320x240, 51μm pitch) three months after the VOx deposition system was installed, and produced over 300 units of U3000 per month just twelve months after beginning the transfer. Process enhancements and tool upgrades have enabled excellent control of the microbolometer process. Today, this line selectively fabricates arrays with NETD varying from 30mK to 80mK in 15mK bins with less than 30 ms time constant. The same arrays also have low defect density of less than 2% dead pixels and no more than one row and one column out. The arrays are packaged in imager or radiometer (F/1.4) packages. DRS also transferred small and large format arrays with 25μm pitch under the PEO-Soldier Sensor Producibility to the Dallas facility. Production of the 25μm pitch devices is currently more that 100 units per month and is ramping up to meet customer demand. This paper reports on production progress on the U3000s and the status of U3500 and U6000 25μm pitch array.

In this paper we present the design, fabrication and characterization of arrays of boron doped polycrystalline silicon bolometers. The bolometer arrays have been fabricated using CMOS compatible wafer-level transfer bonding. The transfer bonding technique allows the bolometer materials to be deposited and optimized on a separate substrate and then, in a subsequent integration step to be transferred to the read-out integrated circuit (ROIC) wafer. Transfer bonding allows thermal infrared detectors with crystalline and/or high temperature deposited, high performance temperature sensing materials to be integrated on CMOS based ROICs. Uncooled infrared bolometer arrays with 18x18 pixels and with 320x240 pixels have been fabricated on silicon substrates. Individual pixels of the arrays can be addressed for characterization purposes. The resistance of the bolometers has been measured to be in the 50 kΩ range and the temperature coefficient of resistance (TCR) of the bolometer has been measured to be -0.52%/K. The pixel structure is designed as a resonant absorbing cavity, with expected absorbance above 90%, in the wavelength interval of 8 to 12 μm. The measured results are in good agreement with the predicted absorbance values.