This PDF file contains the front matter associated with SPIE Proceedings Volume 6940, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and the Conference Committee listing.

In this study, bias mediated tuning of the detection wavelength within the infrared wavelength region is demonstrated for quantum dots-in-a-well (DWELL) infrared photodetectors. In DWELL structures, intersubband transitions in the conduction band occur from a discrete state in the quantum dot to a subband in the quantum well. Compared to "conventional" quantum dot infrared photodetectors, where the transitions take place between different discrete bands in the quantum dots, new possibilities to tune the detection wavelength window are opened up, partly by varying the quantum dot energy levels and partly by adjusting the width and composition of the quantum well. In the DWELL structure used, an asymmetric positioning of the InAs quantum dot layer in a 8 nm wide In0.15Ga0.85As/GaAs QW has been applied which enables tuning of the peak detection wavelength within the long wavelength infrared (LWIR; 8 - 14 µm) region. When the applied bias was reversed, a wavelength shift from 8.5 to 9.5 µm was observed for the peak position in the spectral response. For another DWELL structure, with a well width of 2 nm, the tuning range of the detector could be shifted from the medium wavelength infrared (MWIR; 3-5 µm) region to the LWIR region. With small changes in the applied bias, the peak detection wavelength could be shifted from 5.1 to 8 µm. These tuning properties of DWELL structures could be essential for applications such as modulators and two-colour infrared detection.

This paper discusses recent and future advancements in the field of quantum dots-in-a-well (DWELL) focal plane arrays (FPAs). Additionally, for clarity sake, the fundamentals of FPA figures of merit are reviewed. The DWELL detector represents a hybrid between a conventional quantum well photodetector (QWIP) and a quantum dot (QD) photodetector (QDIP). This hybridization, where the active region consists of QDs embedded in a quantum well (QW), grants DWELLs many of the advantages of its components. This includes normally incident photon sensitivity without gratings or optocoupers, like QDIPs, and reproducible control over operating wavelength through 'dial-in recipes' as seen in QWIPs. Conclusions, drawn by the long carrier lifetimes observed in DWELL heterostructures using femtosecond spectroscopy, have recently backed up by reports of high temperature operation results for DWELL FPAs. This paper will conclude with a preview of some upcoming advances in the field of DWELL focal plane arrays.

Investigations of the performance of quantum dot infrared photodetectors (QDIPs) as compared to other types of infrared photodetectors are presented. A model is based on fundamental performance limitations enabling a direct comparison between different infrared material technologies. It is assumed that the performance is due to thermal generation in the active detector's region. In comparative studies, the HgCdTe photodiodes, quantum well infrared photodetectors (QWIPs), type II superllatice photodiodes, Schottky barrier photoemissive detectors, doped silicon detectors, and high temperature superconductor detectors are considered. HgCdTe photodiodes indicate better performance in comparison with other types of infrared detectors. HgCdTe is characterized by high absorption coefficient and quantum efficiency and relatively low thermal generation rate compared to other types of devices. Theoretical predictions indicate that only type II superlattice photodiodes and QDIPs are expected to compete with HgCdTe photodiodes. QDIPs theoretically have several advantages compared with QWIPs including the normal incidence response, lower dark current, higher operating temperature, higher responsivity and detectivity. Comparison of theoretically predicted and experimental data indicates that, as so far, the QDIP devices have not demonstrated their potential advantages and are expected to posses the fundamental ability to achieve higher detector performance. Poor QDIP performance is generally linked to nonoptimal band structure and controlling the QDs size and density (nonuniformity in QD size).

We describe a recently proposed device concept of using of the dopant-assisted intra-subband absorption mechanism in quantum wells for normal-incidence far infrared / terahertz radiation detection. The Quantum Well Intra-Subband Photodetector (QWISP) is closely related to the quantum-well infrared photodetector (QWIP), which is now been utilized routinely to fabricate large-format (mega-pixel), multi-spectral (3 to 15 μm) focal plane arrays. The QWISP is a compact device that is compatible with existing GaAs QWIP focal-plane array technology. We describe the basic physics and device concept of the QWISP, present a theoretical analysis on its far-IR detection properties, and discuss prospects toward its experimental realization.

A voltage-tunable multi-band quantum dot infrared focal plane array (FPA) is reported. The FPA consists of a 320x256 quantum dot infrared photodetector (QDIP) array hybridized to a readout integrated circuit (ROIC). Each of the QDIP pixels consists of vertically-stacked InAs quantum dots layers with three different capping layers for multi-band (SWIR, MWIR, and LWIR) absorption. By tuning the bias voltage, the FPA is capable of detecting infrared bands individually or simultaneously. High photodetectivity values of greater than 2.3×10¹⁰cmHz^1/2/W were obtained for the various detection bands. Voltage-controllable detection band selection enables real-time image contrast enhancement and discrimination.

Since 2005, the THALES Group has successfully manufactured TV/4 format QWIP sensitive arrays in high rate production at the THALES Research and Technology Laboratory. The full-TV array manufacturing started in 2007. Uniformity and stability were the key parameters which led to the selection of this technology for thermal cameras. Another widely claimed advantage for QWIPs was the versatility of the band-gap engineering and of the III-V processing allowing the custom design of quantum structures to fulfill the requirements of specific applications such as: very long wavelength (VLWIR); multi-spectral detection; and polarimetric detection. Serial production of CATHERINE-XP and CATHERINE-MP has now started for the various programs for which both cameras have been selected. A review of the QWIP Production status, CATHERINE achievements and current programs are presented. THALES has based its current strategy on very compact TI in order to address the largest range of platforms and applications, and is working in cooperation with Sofradir and TRT / III-Vlab on the evolution of the product to take advantage of the new capabilities offered by QWIP technology. In addition, future products based on dual band, multi-band and polarimetric imagery are under development. An overview of these developments is presented.

In recent years, Type-II InAs/GaSb superlattice photo-detectors have experienced significant improvements in material quality, structural designs, and imaging applications. They now appear to be a possible alternative to the state-of-the-art HgCdTe (MCT) technology in the long and very long wavelength infrared regimes. At the Center for Quantum Devices, we have successfully realized very high quantum efficiency, very high dynamic differential resistance R₀A product LWIR Type-II InAs/GaSb superlattice photodiodes with efficient surface passivation techniques. The demonstration of high quality LWIR Focal Plane Arrays that were 100% fabricated in-house reaffirms the pioneer position of this university-based laboratory.

InAs/GaSb short-period superlattices (SL) for the fabrication of mono- and bispectral thermal imaging systems in the mid-wavelength infrared region (MWIR) have been optimized in order to increase the spectral response of the imaging systems. The responsivity in monospectral InAs/GaSb short-period superlattices increases with the number of periods in the intrinsic region of the diode and does not show a diffusion limited behavior for detector structures with up to 1000 periods. This allows the fabrication of InAs/GaSb SL camera systems with high responsivity. Dual-color MWIR/MWIR InAs/GaSb SL camera systems with high quantum efficiency for missile approach warning systems with simultaneous and spatially coincident detection in both spectral channels have been realized.

3rd Generation IR detectors providing e.g. dual-color capability are of great benefit for applications like aircraft missile approach warning systems using this feature for achieving low false alarm rates by separating the hot CO2 missile plume from background and clutter. AIM and IAF selected antimonide based type II Superlattices (SL) for such kind of applications. The type II SL technology provides an accurate engineering of sensitive layers by MBE with very good homogeneity and yield. IAF and AIM already managed to realize a dual-color 384x288 IR-Module based on this technology. It combines spectral selective detection in the 3-4 &mgr;m wavelength range and 4-5 &mgr;m wavelength range in each pixel with coincident integration in a 384x288x2 format and 40 &mgr;m pitch. Excellent thermal resolution with NETD < 17 mK @ F/2, 2.8 ms for the longer wavelength range (red color) and NETD < 30 mK @ F/2, 2.8 ms for the shorter wavelength range (blue color) were already reported. In order to increase further the quantum efficiency and subsequently decrease further the spectral crosstalk between the two colors the layer thickness of the SL-layer was optimized. This paper is intended to present the current status and trends at AIM on antimonide type II Superlattices (SL) IR module developments for ground and airborne applications in the high performance range, where rapidly changing scenes - like e.g. in case of missile warning applications for airborne platforms - require temporal signal coincidence with integration times of typically 1ms.

We report on the status of focal plane arrays (FPAs) based on GaSb/InAs type-II superlattice diodes grown by molecular beam epitaxy (MBE) and designed for infrared absorption in the 2-5μm and 8-10μm bands. Recent LWIR devices have produced differential resistance-area product greater than 100 Ohmcm² at 80K with a long wavelength cutoff of approximately 10μm. The measured quantum efficiency of these front-side illuminated devices is close to 25% in the 8-9 μm range. MWIR devices have produced detectivities as high as 8x10¹³ Jones with a differential resistance-area product greater than 3x10⁷ Ohmcm² at 80K with a long wavelength cutoff of approximately 3.7μm. The measured quantum efficiency of these front-side illuminated MWIR devices is close to 40% in the 2-3μm range at low temperature and increases to over 60% near room temperature. Initial results on SiO₂ and epitaxial-regrowth based passivation techniques are also presented, as well as images from the first lot of 1kx1k MWIR arrays and our latest 256x256 LWIR arrays.

InAsSb is a promising material for high operating temperature MWIR detectors. InAsSb p-n junction detectors dark current is g-r limited in the lower temperature range and diffusion limited in the higher ones. In this work we have investigated the properties GaSb / InAs_0.91Sb_0.09 heterostructure and its performance as a sensitive MWIR photodetector. The heterostructure was obtained by MOCVD growth of lattice matched, unintentionally doped layer of InAsSb on NGaSb substrate. This rectifying N-n heterostructure has the unique type II broken gap interface. I-V and spectral response were measured at various temperatures in the range 20-300 K. The BLIP temperature was found to be 180 K. R₀A product of 2.5 and 180 Ω•cm² were measured at 300 and 180 K, respectively. Dual color detection was demonstrated. The range of spectral response, due to light absorption in GaSb or in InAsSb can be determined by the applied bias. An optical gain larger than one was observed at temperatures below 120 K. High detectivity values of 1.3•10¹⁰ and 4.9•10⁹cm•Hz^1/2W^-1 at 180 and 300 K respectively were measured.

The development of type-II InAs/(In,Ga)Sb superlattice (SL) detectors with nBn design for single-color and dual-color operation in MWIR and LWIR spectral regions are discussed. First, a 320 x 256 focal plane array (FPA) with cutoff wavelength of 4.2 μm at 77K with average value of dark current density equal to 1 x 10^-7 A/cm² at V_b=0.7V (77 K) is reported. FPA reveals NEDT values of 23.8 mK for 16.3 ms integration time and f/4 optics. At 77K, the peak responsivity and detectivity of FPA are estimated, respectively, to be 1.5 A/W and 6.4 x 10¹¹ Jones, at 4 μm. Next, implementation of the nBn concept on design of SL LWIR detectors is presented. The fabrication of single element nBn based long wave infrared (LWIR ) with λ_c ~ 8.0 μm at V_b = +0.9 V and T = 100K detectors are reported. The bias dependent polarity can be exploited to obtain two color response (λ_c1 ~ 3.5 μm and λ_c2 ~ 8.0 μm) under different polarity of applied bias. The design and fabrication of this two color detector is presented. The dual band response (λ_c1 ~ 4.5 μm and λ_c2 ~ 8 μm) is achieved by changing the polarity of applied bias. The spectral response cutoff wavelength shifts from MWIR to LWIR when the applied bias voltage varies within a very small bias range (~100 mV).

In this paper, we report the fabrication and electro-optical characterization of both long-wavelength (LWIR) and middle-wavelength (MWIR) p-on-n infrared photodiodes in HgCdTe. LWIR and MWIR HgCdTe epitaxial layers were grown by liquid phase and molecular beam epitaxy respectively. p-type doping was obtained by arsenic implantation and n-type doping by indium incorporation during growth. The arsenic concentration profile determined by Secondary Ion Mass Spectroscopy showed multi-component diffusion after Hg post-implant annealing. The process yields an arsenic activation efficiency of around 50%, estimated from MEMSA (Maximum Entropy Mobility Spectrum Analysis) measurements. The damage induced by arsenic implantation into HgCdTe have been examined by transmission electron microscopy (TEM) and suggest the formation of an array of dislocations loops after arsenic implantation. However, after annealing under Hg overpressure, the impact of implantation falls below the sensitivity of the TEM, suggesting that annealing effectively suppresses most of the defects. The p-on-n photodiodes showed low leakage currents (shunt resistance>100 MOhms) and typical RoA values comparable to the state of the art (RoA>4000 Ω.cm² for λc=9.2 μm at 77K). Finally, first results on p-on-n focal plane arrays realized at CEA-LETI will be presented.

This paper describes long wavelength (LW) infra-red detectors made from HgCdTe grown by Metal Organic Vapour Phase Epitaxy (MOVPE) and the performance in a low photon flux background compatible with a multispectral requirement. The detectors are staring, focal plane arrays consisting of HgCdTe mesa-diode arrays bump bonded to silicon read-out circuits. The HgCdTe structure is grown on GaAs and consists of an absorber layer sandwiched between wider band-gap cladding layers. Device processing is wafer-scale. Wet etching is used to define the mesas and the mesa sidewalls are passivated with inter-diffused CdTe. The GaAs substrate is removed after bump bonding to minimise the thermal stress on cooling. The technology is sufficiently advanced to enable production not only of LWIR detectors but also dual band MWIR/LWIR detectors, as reported last year. Cameras for both types have been developed. There is now increasing interest in using the technology for LWIR multispectral imaging. Due to the requirement for narrow bandwidths, resulting in low radiant flux, the diode quality, in terms of dark current and resistance, must be exceptionally good. This requirement has been difficult to achieve in many technologies, however MOVPE grown MCT has consistently provided LWIR arrays with the necessary low dark current and high resistance. Performance from arrays of size 640x512 with 24 μm pixels and having a cut-off of 10 μm will be described. These achieve diode impedances of several GΩ's with less than 1 nA dark current at 90K.

Tactical applications are very sensitive to maintenance periodicity and in lot of cases, maintenance position is critical regarding mission availability. Moreover, maintenance has a cost that becomes quickly prohibitive when the cooler or the vacuum have to be repaired too often. Sofradir has worked a lot during last years on reliability and life cycle cost optimization considering all the IR detectors subassemblies. This work has lead to an increased robustness of detectors and technologies even under severe environmental conditions, and reduced variabilities in production. This paper presents the state of the art of Integrated Detector Dewar Cooler Assembly (IDDCA)'s reliability, the production means and the methods that allow us today to propose detectors with very high reliability without maintenance. These detectors are a breakthrough for life cycle cost for tactical applications as portable cameras, airborne systems, and missiles.

HgCdTe (Mercury Cadmium Telluride / MCT) staring arrays for infrared detection do show constant improvements regarding their compactness and performances. New detectors are now proposed offering system solutions in the different IR wavebands and taking advantage of the latest technology improvements as well as MCT performance advantages and cost reduction. Based on 20 years of experience in 50μm to 15μm pitch Infrared (IR) detector production, the challenge of mass production of low-cost small-pixel pitch detectors are reviewed, from the IR chip manufacturing including detection material, hybridization, ROIC, to the integration in final packing. Taking advantage of its simple well known existing process, then the analyzes of all technological steps adapted to small pitch IR detector are presented, in terms of product performance, reliability, process statistics and capability in order to achieve high yield and low product cost. Answers given the low-cost small-pitch IR detector mass productions finally give benefits to application in terms of high performance, cost reduction, extended life time, and on the field system Life Cycle Support Among these new detectors, one can find the family of 15 μm pixel pitch detectors a TV format (640 x 512) integrated in dedicated tactical Dewars, taking advantages on last development in coolers manufacturing and Dewar assembly.

The design, development, and characterization of a new, low-power, wide operating temperature range miniature short wave infrared (SWIR) camera for military applications is described in this paper. Such applications typically require operation over an extended(<-35C to >65C) temperature range. The camera technology is based on standard indium-gallium-arsenide (InGaAs) focal plane array (FPA) technology, but eliminates the thermal electric cooler (TEC) to both expand the operating temperature range and minimize power consumption. To compensate for variable FPA temperature, new algorithms were conceived and implemented in real time camera hardware resulting in a camera with an operating temperature range wider than that possible by stabilizing with a single stage peltier cooler. The additional benefit is reduced power consumption at temperature extremes and concomitant reduction in required thermal management. Imagery and results will be presented from 320x256 and 640x512 arrays.

Boeing Spectrolab has grown, fabricated and tested InGaAs PIN arrays with less than 1 nA/cm2 dark current density at 280 °K. The PIN diodes display greater than 1 A/W responsivity at -100 mV reverse bias with about 50 fF of diode capacitance.

Low cost IR Sensors are needed for a variety of Military and Commercial Applications. SiGe based IR Focal Plane Arrays offer a low cost alternative for developing near IR sensors that will not require cooling and can operate in the visible and NIR bands. The attractive features of SiGe based IRFPA's will take advantage of Silicon based technology, that promises small feature size and compatibility with the low power silicon CMOS circuits for signal processing. A feasibility study of an infrared sensor based on SiGe material system and its performance characteristics are presented. Simulations comparing the sensitivity of the SiGe detector with spectral cutoff wavelength of 1.6 micron to other IR Focal Plane arrays are discussed. Measured electrical and optical characteristics of Ge-on-Si photodetectors are also presented.

NoblePeak Vision has developed monolithic visible to short-wave infrared (SWIR) imaging arrays. An innovative growth technique is used to integrate germanium islands with the silicon transistors and metal layers of a CMOS process. Imaging arrays of 128x128 pixels at a 10 μm pitch were designed and fabricated, with the silicon photodiodes of a conventional CMOS imager replaced by germanium photodiodes. Broadband response from 400 nm to 1650 nm has been measured. Imaging die have been packaged with a Peltier cooler and built into a camera evaluation kit.

Goodrich, SUI has developed a 15 μm pitch, 1280 x 1024 pixel InGaAs focal plane array (FPA) with low noise, and visible to near infrared (0.4 μm to 1.7 μm) wavelength response for day and night vision applications. The readout integrated circuit (ROIC), which uses a capacitive transimpedance amplifier (CTIA) pixel, is designed to achieve a noise level of less than 50 electrons, due to its small integration capacitor. The ROIC can be read out at 120 frames per second, and has a dynamic range of 3000:1 using rolling, non-snapshot integration. The ROIC was fabricated in a standard CMOS foundry process, and was bump-bonded to Vis-InGaAs^TM detector arrays. SUI has successfully hybridized 15 μm pitch 1280 x 1024 pixel FPAs, and produced imagery.

The interest in new infrared materials has grown rapidly during the last decade, one reason being the increasing cost of traditional Germanium, with in the meantime, a decrease of the cost of infrared detectors. In response to this Umicore has developed the GASIR® range of optical materials. A key strength of the new material is that it can be molded, leading to particularly cost effective solutions for high volume requirements. This paper reviews the GASIR®1 material relative to some of the existing materials and presents a case study of an optical design using GASIR®. In particular the effect of thermal cycling on survivability and performance are examined. The case study includes Umicore's recently developed iDLC(tm) coating. This coating complies with the specifications for "Diamond Like Carbon" coatings and can thus suit a broad range of applications such as thermography, fire fighting, etc.

Amorphous Materials began in 2000 a joint program with Lockheed Martin in Orlando to develop molding technology required to produce infrared lenses from chalcogenide glasses. Preliminary results were reported at this SPIE meeting by Amy Graham1 in 2003. The program ended in 2004. Since that time, AMI has concentrated on improving results from two low softening glasses, Amtir 4&5. Both glasses have been fully characterized and antireflection coatings have been developed for each. Lenses have been molded from both glasses, from Amtir 6 and from C1 Core glass. A Zygo unit is used to evaluate the results of each molded lens as a guide to improving the molding process. Expansion into a larger building has provided room for five production molding units. Molded lens sizes have ranged from 8 mm to 136 mm in diameter. Recent results will be presented

A new getter type produced as a vacuum deposited thin-film is under development (patent pending). The film serves as an efficient pumping substance and also as an efficient absorber of IR stray light. The getter film is activated in place by heating to 130^oC. The film is very thin and has excellent vibration resistance and temperature stability and is expected to serve as an advantageous new solution for IR detector dewars and cold shields.

The advancement from 2^nd Gen FLIR to 3^rd Gen FLIR provides a significant improvement in capability, but at the cost of increased optical complexity. It is not feasible to utilize optics from previous generations image adequately with a 3^rd Gen FLIR engine. Incorporating new technologies such as dual f/number dewars and dual band detectors results in very different optical design requirements from previous generations. Lack of broadband optical materials and coatings adds further complexity to the 3^rd Gen optical problem. This paper examines the new complexities that are being introduced by 3^rd Gen, some of the generic approaches that are necessary, and areas where more work is required.

Sensor performance for dual band forward looking infrared (FLIR) imagers can be substantially improved by increased simultaneous throughput of both sensor bands in the optical systems. Currently available antireflection coatings (ARs) have optimized performance for either spectral band, but not both on the same optic. Where AR coatings cover the mid and long wave infrared (LWIR) bands, or the entire broad band spectrum from visible to LWIR, performance is not sufficient for future systems. A method of designing and fabricating high performance ARs has been developed. This paper presents a discussion of the trade-off of film thickness and complexity versus transmission performance. Fabrication results for high, medium and low index lens materials are also presented.

One of the benefits of 3^rd Generation FLIR technology is the potential to maintain range performance but with a much smaller optical system. A 3^rd Gen Demonstrator (3GD) has been assembled and tested to demonstrate this capability. The 3GD features a four field of view optical system incorporating dual f/number optics with an all-reflective folded three mirror anastigmat (TMA) afocal, axial zoom dual band imager, internal thermal reference, and a beam splitter port for integrating other sensors such as a visible camera. This paper discusses the results of the fabrication of this 3^rd Gen demonstration system with an emphasis on lessons learned from the challenges of 3^rd Gen optics.

As dual band, 3rd generation FLIR systems progress from the research lab into the field, supporting technologies must also advance. This paper describes advances in Thermoelectric Thermal Reference Sources (TTRS) from single band (3 to 5 or 8 to 12 microns) to dual band in one assembly (3 to 5 and 8 to 12 microns). It will describe the optical, system, electrical, and mechanical parameters of dual band TTRS units. It provides IR system design engineers with the critical parameters of dual band TTRS units to aid in their design process. TTRS assemblies provide a temperature controllable radiometrically uniform surface. When viewed by theFLIR system detectors, the TTRS enables the system electronics to perform gain and offset calibration as well as DC restoration for each pixel's preamp Some of the parameters for 3rd Generation FLIR system TTRS units included in this paper will be: Emissivity of BB surfaces. Apparent thermal radiometric uniformity. How this is predicted and measured. Window material wavelength transmission (Hermetically sealed units only). TTRS emitter surface temperatures as a function of heat sink temperatures. Trade-off between uniformity, power consumption, and transient performance. Power consumption, Thermal interfaces and required heat sinking Types and accuracy of Temperature sensors mounted on emitter surface. Also included in this paper is a description of a Thermoelectric Black Body Test Apparatus that can be used to generate temperature coefficients needed to "burn" Proms for uncooled IRFPAs during their production and burn in processing.

Manufacturing processes have been developed to produce wafer scale optics in chalcogenide glass using semiconductor fabrication. Chalcogenide materials are amorphous and covalently bonded solids containing one or more of elements in Group VI in the periodic table, e.g. sulphur, selenium, or tellurium as a substantial constituent. For this paper, the material selected for testing to determine the etching process was IG6 - As₄₀Se₆₀. Grayscale photolithography and binary methods were used to pattern diffractive elements for use in infrared applications. Dual-band color correction, incorporating diffractive optics, will be presented in the paper as an application of this development.

We report our progress on the design, modeling, and fabrication of a step-index miniature spherical retroreflector for use in the mid- and long-wave infrared region (3 μm-12 μm). Efficient retroreflectors with large acceptance angles and isotropic performance have several defense applications - for instance, target tracking and monostatic LIDAR. The ideal isotropic spherical retroreflector is epitomized by the spherical Luneburg lens, which brings a collimated beam to a perfect focus on the rear surface of the sphere due to its gradient index profile and spherical symmetry. The ideal Luneburg lens' gradient profile, however, must have an index value equal to that of the immersion medium at its boundaries; therefore, rendering its fabrication infeasible for applications in air. Although spherical gradient index designs can provide a good approximation of the Luneburg lens, as of now there have been no demonstrated methods of fabricating such lenses, especially for mid- and long-wave infrared applications. Consequently, we have designed a retroreflector with a step-index approximation to a spherical gradient index design with comparable optical performance to the spherical gradient index ideal. This retroreflector design can be fabricated by molding a higher index chalcogenide glass shell as a cladding layer over a lower index core such as ZnS using glass compression molding.

The image contrast and clarity recorded by backside illuminated HgCdTe focal plane arrays (FPAs) is strongly dependent on minimizing signal loss and detector noise caused by scattered and reflected light from the FPA window and imaging optics. Thin film anti-reflection (AR) treatments based on stacks of thin-film materials have been exclusively used to minimize substrate reflections for this application. The performance and lifetime of these thin-film AR coatings is limited, and can be inadequate for some space based applications due to the damage produced in the coatings by radiation exposure and extreme temperature variations. A new type of high performance AR treatment for HgCdTe FPAs promising very wide bandwidth operation and increased lifetime in high radiation environments is under development as part of the MDA's Space Tracking and Surveillance System, or STSS. Based on surface relief microstructures fabricated directly in the FPA window, the new textured AR treatment replaces thin-film coatings, eliminating inherent coating limitations such as stress, thermal expansion mismatch, adhesion, radiation hardness, and low laser damage thresholds. Progress on the design, fabrication, and space qualification of AR microstructures for staring format HgCdTe FPA windows, is reported here. Transmission data for FPA windows containing AR microstructures is presented, demonstrating a reduction of reflected light loss from 21% for an untreated window down to an average of less than 1% over a six micron wide spectral range in the long wave infrared region (7-13&mgr;m). The potential for AR microstructures to perform over even wider bandwidths such as the important dual-band infrared region (3-12&mgr;m), has been demonstrated. Such high AR performance is coupled with nearly un-measurable scattered light losses as recorded by sensitive instruments operated by NIST. Initial proton radiation exposure and thermal cycling tests show no damage to the microstructures and no degradation of the AR performance. Interferometer measurements of the surface flatness of FPA windows incorporating AR microstructures indicate no change from the initial surface flatness, a result that is a significant improvement over thin-film AR coatings, and one that has great potential for large format FPA fabrication.

We introduce into optical systems, susceptible to be interrupted or damaged from laser, novel passive solid-state threshold-triggered Wideband Protection Filter (WPF) that blocks the transmission only if the power exceeds a certain threshold. We present new protection capabilities of our latest filter composed of improved technology. The WPF can be readily used for protection of detectors, cameras, or eye safety.

Deployment of compact hyperspectral imaging sensors on small UAVs has the potential of providing a cost-effective solution for rapid-response target detection and cueing based on time critical spectral information collected at low altitudes. To address this goal, a new compact hyperspectral imaging sensor is being developed with an anamorphic optical system that partially decouples image formation along both the spatial and spectral axes found in conventional push-broom hyperspectral imagers. This design concept benefits from a reduction in complexity over standard highperformance spectrometer optical designs while maintaining excellent aberration control and spatial and spectral distortion characteristics. The anamorphic optical system has the advantage of removing the spectrometer slit focus along the spatial axis and in turn eliminates nearly all aberrations in the front-end optics, regardless of field angle or aperture size. This paper presents results from the first prototype anamorphic imaging spectrometer, which weighs 4 pounds and is designed for operation in the Short Wave InfraRed (SWIR) spectral band over a wavelength range of 1 μm to 1.7 μm dictated by the uncooled InGaAs focal plane array used as the detector. The anamorphic system design will be discussed and results from characterization and field measurements will be presented.

Thin film Si_xGe_1-xO_y were deposited on glass, silicon and SiO₂ by RF magnetron sputtering using co-sputtering of silicon and germanium targets in an environment of oxygen and argon. Silicon percentage was varied from ~7% to 22%. Exact contents of each material were determined by XRD/EDS and electrical properties of amorphous compound were studied. High values of temperature coefficient of resistance were obtained in specific conditions. the highest achieved TCR at room temperature was (5.8%/K) using Si_0.177Ge_0.726O_0.097 (film deposited at 400 °C). The measured resistivity on this sample was 14.6 Ω cm.

Agiltron has demonstrated an uncooled dual-band MWIR/LWIR imager based on our previously reported photomechanical sensor technology. The readout from two separate MWIR and LWIR photomechanical sensor arrays were fused together, permitting either dual-band, MWIR-only, or LWIR-only operation of the imager. Results of the dual-band imager in response to a wide-dynamic range infrared scene are described. With the dual-band MWIR/LWIR capability, the full dynamic range of the scene was successfully captured, yet good sensitivity was still maintained when imaging near-room temperature objects. Extensive comparative performance analysis was performed for the photomechanical thermal imager and HgCdTe and InSb photon imagers. A noise model for the optical readout photomechanical thermal imager is presented. It is shown that the photomechanical pixel can be engineered to nullify the contribution of shot noise to NETD without affecting the thermal properties of the pixel. In this regime, the performance of the uncooled photomechanical imager will approach that of cooled photon imagers.

Multispectral Imaging has recently made considerable improvements to the sensitivity, uniformity and dynamic range of infrared FPAs based on capacitively read, bimorph microcantilever sensor technology. The company is presently prototyping 160x120 imaging arrays with 50 μm pitch pixels and is actively pursuing the development of next generation 25 μm pitch pixel arrays. Measured peak NETD values for recently fabricated 50μm pitch focal plane arrays are in the 40-50mK range, with individual pixels in the 10-15mK range. The modeled and measured tradeoffs discussed in this paper lead to a possible 2-3 times further improvement in average NETD. A number of factors influence the performance of these devices which includes the optimization of sometimes competing design requirements. For example, the tuning and optimization of the infrared optical resonant cavity structure while maximizing the change in sensor capacitance during IR irradiance. Similarly there are tradeoffs between structural rigidity, which increases the structure resonant frequency improving noise immunity, and thermal response times. These tradeoffs are discussed with reference to real world sensor structures. Results from detailed thermo-electromechanical-optical modeling of the operation of the 25 μm pitch pixels will be discussed in reference to the design and fabrication of 25 μm pitch test pixels. The most recent infrared sensitivity and other performance measurements from the development of the company's first commercial 160 x 120 pixel imaging array product will also be presented.

An uncooled capacitive type bimaterial infrared detector with high fill-factor and improved noise characteristic is investigated. Top electrode is insulated from the substrate thermally as well as electrically. Only small dimension (10μmx2μmx0.2μm) of SiO₂ only layer (thermal insulation leg) assures thermal conductance of 1.06x10^-7W/K, while keeping the infrared absorber (top electrode) separated from the bias signal. Due to the decreased thermal isolation leg length, high fill-factor of 0.77 is achieved. The bimaterial leg that connects the infrared absorber to the thermal insulation leg is a 38μm long cantilever structure composed of Al and SiO₂ bi-layer, which has large difference in the thermal expansion coefficient (Al:25ppm/K and SiO2:0.35ppm/K). Bimaterial leg length (38μm) is quite shorter than the previously designed device, resulting in the decreased bending of the bimaterial leg. However, the increased fill-factor reduces temperature fluctuation noise term that is inversely proportional to the absorber area, and it is found by FEM simulation that the enhanced mechanical properties such as spring constant reduce the thermo-mechanical noise term of the proposed device.

We have been developing a novel thermal-to-visible transducer (TVT), an uncooled thermal-IR imager that is based on a Fabry-Perot Interferometer (FPI). The FPI-based IR imager can convert a thermal-IR image to a video electronic image. IR radiation that is emitted by an object in the scene is imaged onto an IR-absorbing material that is located within an FPI. Temperature variations generated by the spatial variations in the IR image intensity cause variations in optical thickness, modulating the reflectivity seen by a probe laser beam. The reflected probe is imaged onto a visible array, producing a visible image of the IR scene. This technology can provide low-cost IR cameras with excellent sensitivity, low power consumption, and the potential for self-registered fusion of thermal-IR and visible images. We will describe characteristics of requisite pixelated arrays that we have fabricated.

We describe initial results from a module built using the Thermal Light Valve^TM (TLV) - a diffractive thin film spatial light modulator that provides high response to long-wavelength infrared radiation. In this paper we briefly describe a differential-mode TLV device, its solid state structure, readout system configuration, and performance parameters. We describe the architecture of an 80x60 OpTIC^TM thermal imaging module based on the TLV, and give some early imaging results. We review the manufacturability of the component and module and the implication for low-cost thermal imaging.

Carbon nanotube (CNT) has been found to be one of the promising materials for efficient detection and used in different nanoelectronic devices due to its unique electrical properties. Recently, the applications of nanostructural material to infrared (IR) sensors are considered. Our group developed a color detector using a single CNT and demonstrated the good sensitivity of CNT to the infrared light in different ranges. In this report, the CNT bandgap engineering was discussed. The design, fabrication and experimental result of the CNT based color detector were described. The results indicated the heterogeneous electrode structure increased the signal-to-dark current ratio. Moreover, the CNT based color detectors were capable to sense near-infrared signal and middle-infrared signal in room temperature environment.

Lucid Dimensions is developing Spherical Sensor Configurations (SSC) for detecting and tracking signals in three dimensions. The Spherical Sensor Configurations offer distinct advantages over contemporary imaging systems, significantly enhancing three-dimensional (3D) situational awareness. Sensor systems utilizing a spherical geometry as a foundation can be designed for a variety of applications. A singular ring of sensors provides a basic device that can monitor sources in a 2 dimensional plane. These systems calculate extremely accurate angular directions to signal sources. More sophisticated systems with full spherical sensor placement are being designed for monitoring multiple targets in any spatial orientation. Information generated from these systems can be integrated with contemporary imaging systems for further target identification. Full spherical SSC systems offer a 4 Pi steradian Field of Regard (FOR) for complete situational awareness.

During the last decade, protection of civilian and military operational platforms or vehicles against threats has been an issue of increased importance. A significant difference exists between warfare as viewed ten years ago and the nature of conflict today. More emphasis is being placed on short range positive ID, wide field of regard situational awareness and quick reaction times .The standard countermeasure is inadequate when not accompanied by a set of efficient sensor. The sensor packages primarily consisting of an alerting device of four different detection steps: pre-alert, giving the directions of possible attack, detection of an action of attack, identification of the threat and finally the precise localization (3-D). The design of the alerting device is greatly depending on which it will be used, the associated cost and the nature of the threat. Recently the requirements for these sensors have become more and more stringent due to the growing number of scenarios. The attack can practically be from any direction, implying the need for a large Field of Regard, the attack range and the type of threat can vary considerably. Especially the localization at short ranges is a challenging issue which can be addressed by an optimized panoramic imager. The new panoramic IR panomorph lens imager, considered, and evaluated at ImmerVision is presented for integration on various platforms. This innovative panomorph approach provides enhanced performance with better pixel/cost ratio by providing an increased resolution in the zone of interest. The IR panomorph based sensor is as an aberration-corrected hemispheric imager with a custom lens designed to match the resolution the IR camera (MWIR-LWIR) with improved image quality, field coverage and resolution for target detection, classification, and tracking. Various configurations and scenarios including advantages and drawbacks are discussed.

With large focal plane arrays now widely available, IR detectors have entered their third generation. Performances have increased dramatically with respect to second-generation, line array detectors, due to the longer integration times afforded. For surveillance systems such as InfraRed Search and Track (IRST), however, operational requirements generally impose a very large field of regard in relation to the instantaneous field of view. This characteristic which has traditionally been obtained through scanning motion for second generation line array detectors must now be rethought to obtain staring operation for 3rd generation FPA, lest motion blurring be incurred. This paper presents several approaches considered for naval surveillance systems at Sagem Defense Securite to tackle this challenge. Three techniques are presented and then compared: fully staring systems, step-and-stare systems, and finally a "modified" step-and-stare system.

Present-day naval operations take place in coastal environments as well as narrow straits all over the world. Coastal environments around the world are exhibiting a number of threats to naval forces. In particular a large number of asymmetric threats can be present in environments with cluttered backgrounds as well as rapidly varying atmospheric conditions. During trials executed in False Bay a large amount of target, background and atmosphere data was gathered that is of use in analysis of optical characteristics of targets and backgrounds. During the trials a variety of backgrounds were recorded. We have used these backgrounds to validate the TNO background model MIBS to incorporate also coastal backgrounds and sunlit sea backgrounds. In the paper we show results of the background analysis, for coastal bay backgrounds. In particular the detection of small targets by automatic system may be hampered by small surface structure variations at the surface and near the horizon. The data that we analyzed are sea surface structure, temporal behaviour, and spectral differences during different environmental conditions that occurred during the trials. This data is essential to feed detection algorithms, and performance models for the assessment of sensor performance in coastal environment. Some sensor management approaches for application in IRST systems is discussed.

In the maritime environment, the main goals of an infrared search and track system is to search and track the targets approaching to ships, such as sea skimming missiles, small ships, and aircrafts. In this paper, we propose a high performance infrared search and track system. Our proposed infrared search and track system is composed of a dual band infrared detection module, signal processing module, servo control module, and control console module. In the dual band infrared detection module, the sensor head of our proposed system is organized by one-dimensional MWIR and LWIR detectors (480X6) with 3-axes servo stabilization. The signal-processing module consists of several blocks such as a target detection block, target tracking block, panoramic video displaying block, video input/output block, and system control block. Those blocks perform the signal-processing algorithms involved with target search and tracking. In our proposed system, adaptive temporal and spatial filtering methods, which can reduce background clutters effectively, are used for target detection. Moreover, the extended Kalman filter and the integrated probabilistic data association (IPDA) algorithm are adapted for target tracking. Therefore, our proposed infrared search and track system can increase the defense ability of warships due to long range and high accuracy of target detection and tracking.

A miniaturized near-field observation platform is presented comprising a sensitive daylight camera and an uncooled micro-bolometer thermal imager each equipped with a wide angle lens. Both cameras are optimised for a range between a few meters and 200 m. The platform features a stabilised line of sight and can therefore be used also on a vehicle when it is in motion. The line of sight either can be directed manually or the platform can be used in a panoramic mode. The video output is connected to a control panel where algorithms for moving target indication or tracking can be applied in order to support the observer. The near-field platform also can be netted with the vehicle system and the signals can be utilised, e.g. to designate a new target to the main periscope or the weapon sight.

Aiming at night time spaceborne imaging, we compare the expected performances of a low-light-level visible sensor with a conventional IR sensor. The low-light-level visible sensor, an electron multiplier CCD (EMCCD), is a close to ideal photon counting device, with possibly negligible dark current noise and negligible readout noise. This fact, along with the significant improvement of diffraction (about an order of magnitude), suggests an interesting competition between the two technologies. In essence, this is a tradeoff between noise and optical performances (favoring the visible channel) and basic target radiance (favoring IR). Other factors such as reliability and cost can also play an important role. While we consider two different spectral ranges with different imaging content, we are able to conduct a cautious theoretical comparison based on standard targets in various lighting conditions. We show that for a given set of system parameters, even when lighting conditions are favorable, i.e. a night with a full moon, the low-light-level visible channel performances are inferior to those of an IR channel. We also comment on the significance of the system working point regarding performances under varying condition.

Current and future land warriors operate in a group or autonomously. The necessity to observe and locate targets during day, night and all weather conditions inspire developments of small, but complex handheld devices, which are able to fulfill these tasks. Observation in daylight can be achieved by means of a visual telescope with high resolution. For night operation a thermal imager is required. Navigation tasks can be fulfilled with a digital magnetic compass and a GPS receiver. For measuring ranges to targets an eye-safe laser rangefinder is necessary. OPUS H, the newest member of the ZEISS family of handheld navigational and targeting devices, combines all these functions in a light-weight instrument and analyses all data to provide first hand information about potential targets to the soldier and his group with sufficient accuracy for combat decisions.

In all recent missions our forces are faced with various types of asymmetric threads like snipers, IEDs, RPGs or MANPADS. 2^nd and 3^rd Gen IR technology is a backbone of modern force protection by providing situational awareness and accurate target engagement at day/night. 3^rd Gen sensors are developed for thread warning capabilities by use of spectral or spatial information. The progress on a dual-color IR module is discussed in a separate paper [1]. A 1024x256 SWIR array with flexure bearing compressor and pulse tube cold finger provides > 50,000h lifetime for space or airborne hyperspectral imaging in pushbroom geometry with 256 spectral channels for improved change detection and remote sensing of IEDs or chemical agents. Similar concepts are pursued in the LWIR with either spectroscopic imaging or a system of LWIR FPA combined with a cooled tunable Laser to do spectroscopy with stimulated absorption of specific wavelengths. AIM introduced the RangIR sight to match the requirements of sniper teams, AGLs and weapon stations, extending the outstanding optronic performance of the fielded HuntIR with position data of a target by a laser range finder (LRF), a 3 axis digital magnetic compass (DMC) and a ballistic computer for accurate engagement of remote targets. A version with flexure bearing cooler with >30,000h life time is being developed for continuous operation in e.g. gunfire detection systems. This paper gives an overview of AIM's technologies for enhanced force protection.

The HuntIR long range thermal weapon sight of AIM is deployed in various out of area missions since 2004 as a part of the German Future Infantryman system (IdZ). In 2007 AIM fielded RangIR as upgrade with integrated laser Range finder (LRF), digital magnetic compass (DMC) and fire control unit (FCU). RangIR fills the capability gaps of day/night fire control for grenade machine guns (GMG) and the enhanced system of the IdZ. Due to proven expertise and proprietary methods in fire control, fast access to military trials for optimisation loops and similar hardware platforms, AIM and the University of the Federal Armed Forces Hamburg (HSU) decided to team for the development of suitable fire control algorithms. The pronounced ballistic trajectory of the 40mm GMG requires most accurate FCU-solutions specifically for air burst ammunition (ABM) and is most sensitive to faint effects like levelling or firing up/downhill. This weapon was therefore selected to validate the quality of the FCU hard- and software under relevant military conditions. For exterior ballistics the modified point mass model according to STANAG 4355 is used. The differential equations of motions are solved numerically, the two point boundary value problem is solved iteratively. Computing time varies according to the precision needed and is typical in the range from 0.1 - 0.5 seconds. RangIR provided outstanding hit accuracy including ABM fuze timing in various trials of the German Army and allied partners in 2007 and is now ready for series production. This paper deals mainly with the fundamentals of the fire control algorithms and shows how to implement them in combination with any DSP-equipped thermal weapon sights (TWS) in a variety of light supporting weapon systems.

The successful mission of an autonomous airborne system like an unmanned aerial vehicle (UAV) strongly depends on an accurate target approach as well as the real time acquisition of detailed knowledge about the target area. An automatic 3D scene reconstruction of the overflown ground by a structure from motion system enables to interpret the scenario and to react on possible changes by optimization of flight path or adjustment of mission objectives. Additionally, detection of the target itself can be improved due to the analysis of the reconstructed 3D target scenario. In this work a newly developed system for automatic 3D reconstruction of a scene from aerial infrared imagery is presented. For more accuracy in the reconstruction and to overcome the drawbacks of feature tracking in IR images, pose information given by an IMU (Inertial Measurement Unit) are used for computation of 3D structure. Detected 2D image features are tracked image by image to calculate corresponding 3D information. Each estimated 3D point is assessed by means of its covariance matrix which is associated with the respective uncertainty. Finally a non-linear optimization (Gauss-Newton iteration) of the reconstruction result yields the completed 3D point cloud. As possible applications, approaches for target recognition in fused IR images and 3D point clouds as well as registration of point clouds for image based navigation update are presented.

We present SWIR advantages for realizing low-power, high-speed and small size search-detect and tracking optical systems. The characteristics of low-clutter, and robustness of the target observables when atmospheric interference occurs are discussed in detail. Next - we present the SWIR building blocks developed in order to allow for the detection systems to be built.

A low-cost muzzle flash detection based on CMOS sensor technology is proposed. This low-cost technology makes it possible to detect various transient events with characteristic times between dozens of microseconds up to dozens of milliseconds while sophisticated algorithms successfully separate them from false alarms by utilizing differences in geometrical characteristics and/or temporal signatures. The proposed system consists of off-the-shelf smart CMOS cameras with built-in signal and image processing capabilities for pre-processing together with allocated memory for storing a buffer of images for further post-processing. Such a sensor does not require sending giant amounts of raw data to a real-time processing unit but provides all calculations in-situ where processing results are the output of the sensor. This patented CMOS muzzle flash detection concept exhibits high-performance detection capability with very low false-alarm rates. It was found that most false-alarms due to sun glints are from sources at distances of 500-700 meters from the sensor and can be distinguished by time examination techniques from muzzle flash signals. This will enable to eliminate up to 80% of falsealarms due to sun specular reflections in the battle field. Additional effort to distinguish sun glints from suspected muzzle flash signal is made by optimization of the spectral band in Near-IR region. The proposed system can be used for muzzle detection of small arms, missiles and rockets and other military applications.

Understanding of the temporal and spectral behavior of the radiation emitted from fast transients such as gun shots, explosions, missile launches and kinetic ammunition is very important for the development of IRST, MWS and IRCM systems. The spectral-temporal behavior of the signature of these events is an essential factor for their detection and for the filtering of false alarms. Munitions flashes are fast transient phenomena with time duration that range from the sub-millisecond to a fraction of a second. A full characterization of the infrared signature of these events involves measurement of the evolution of its spectral distribution in time where the temporal resolution required is of the order of microseconds. We describe here a method for utilizing a four-channel radiometer to extract the above-mentioned data from these events. We show that we can derive the temporal evolution of the temperature of an explosion on time scale of 20&mgr;sec and separate energy releasing processes. Several practical examples will be given.

Development of robust compact optical imagers that can acquire both spectral and spatial features from a scene of interest is of utmost importance for standoff detection of chemical and biological agents as well as targets and backgrounds. Spectral features arise due to the material properties of objects as a result of the emission, reflection, and absorption of light. Using hyperspectral imaging one can acquire images with narrow spectral bands and take advantage of the characteristic spectral signatures of different materials making up the scene in detection of objects. Traditional hyperspectral imaging systems use gratings and prisms that acquire one-dimensional spectral images and require relative motion of sensor and scene in addition to data processing to form a two-dimensional image cube. There is much interest in developing hyperspectral imagers using tunable filters that acquire a two-dimensional spectral image and build up an image cube as a function of time. At the Army Research Laboratory (ARL), we are developing hyperspectral imagers using a number of novel tunable filter technologies. These include acousto-optic tunable filters (AOTFs) that can provide adaptive no-moving-parts imagers from the UV to the long wave infrared, diffractive optics technology that can provide image cubes either in a single spectral region or simultaneously in different spectral regions using a single moving lens or by using a lenslet array, and micro-electromechanical systems (MEMS)-based Fabry-Perot (FP) tunable etalons to develop miniature sensors that take advantage of the advances in microfabrication and packaging technologies. New materials are being developed to design AOTFs and a full Stokes polarization imager has been developed, diffractive optics lenslet arrays are being explored, and novel FP tunable filters are under fabrication for the development of novel miniature hyperspectral imagers. Here we will brief on all the technologies being developed and present highlights of our research and development efforts.