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.

This paper discusses the performance difference of two long-wave (8 to 12 microns) cooled infrared focal plane arrays applied to spectral imaging, one using a HgCdTe detector array and the other using a QWIP detector array. QWIP detectors tend to have a much narrower spectral response than HgCdTe detectors, therefore applications can be limited. For applications for the detection of specific gases, such that the signature of the gas absorption is within the narrower band, the QWIP can be a viable alternative to HgCdTe detectors. Such is the case for detection of sulfurhexafluoride (SF₆). In this paper we compare the performance of two different imaging spectrometers where one has a cooled HgCeTe detector array and the other has a cooled QWIP detector array. The gases used in this comparison were sulfurhexafluoride (SF₆), 1,1- difloroethane, and 1,1,3 trichloroethane. Figures of merit that will be compared are the noise equivalent spectral radiance (NESR), and visibility. Both detectors have 340 x 256 pixel elements in the array. A paper written comparing HgCdTe and QWIP dual band detectors by Arnold Goldberg et. al. discussed the difference between the two detector materials. To our knowledge, a comparison of a broadband (HgCdTe) and narrow band (QWIP) detector as applied to spectral imaging of gases has never been done before.

A dualband infrared focal plane array is the central component of a compact, low mass, multispectral imaging spectrometer with perfect spectral registration. The prototype spectrometer design uses a grating blaze chosen to be efficient over both 3.75-6.05 and 7.5-12.1 μm, although the mercury cadmium telluride focal plane array limits the bandwidths with cutoff wavelengths near 5.2 and 10.5 μm. The spectrometer has been spectrally calibrated with flooded blackbody illumination and offset and gain corrections have been performed. The wavelength resolution is ±0.024 μm in the MWIR and ±0.083 μm in the LWIR, however this limitation is caused by the calibration method and not by the design. The potential for determining the temperature of a blackbody or greybody from the ratio of two narrow wavebands has been demonstrated.

A novel technique of NIR imaging is presented that gives access to most of the applications currently published as being solely suitable for Terahertz (THz) waves. The technique uses NIR beams wavelengths found in ordinary domestic remote controls (circa 850 nm) and various signal recovery techniques commonly found in astronomy. This alternative technique can be realised by very simple and inexpensive electronics and is inherently far more portable and easy to use and no special sources are required. Transmission imaging results from this technique are presented from several industrial examples and various security applications and are compared and contrasted directly with their THz-derived counterparts. It would appear possible to very cheaply and simply emulate the performance of commercial terahertz systems at a fraction of the cost and with greatly reduced processing times Another advantage is that apart from imaging, this technique affords the means to provide simultaneous in-situ chemical-bond analysis for stand-off detection of certain chemical signatures - for example, those found in drugs and explosives (both molecular and oxidiser based). Also, unlike THz, this technique can penetrate bulk water and high humidity atmospheres and be used in transmission mode on biological and medical samples. Several results are presented of non-ionising X-ray type images that even differentiate between separate types of soft tissue

A high-visibility infrared array emitter for identification and display screen has been demonstrated. The silicon-based MEMS Infrared emitter was fabricated on silicon-on-insulator (SOI) wafer. The infrared emitter cell can be operated at 1100K with a total power of 2.5W, and the modulation frequency can reach to 50Hz at 50 modulation depth. The Infrared array emitters consist of 1*2, 2*2 and 3*3 emitter cells, respectively, which can be made as an infrared indicator or display screen for object identification and information displaying with a recognition ranges determined by input power. The experiments shown that due to the problems of structure and stress, the modulation frequency and lifetime of the infrared array emitter were reduced with increasing array dimension.

This paper presents two different architectures for the design of Analog to Digital Converters specifically adapted to infrared bolometric image sensors. Indeed, the increasing demand for integrated functions in uncooled readout circuits leads to on-chip ADC design as an interface between the internal analog core and the digital processing electronics. However specifying an on-chip ADC dedicated to focal plane array raises many questions about its architecture and its performance requirements. We will show that two architecture approaches are needed to cover the different sensor features in terms of array size and frame speed. A monolithic 14 bits ADC with a pipeline architecture, and a column 13 bits ADC with an original dual-ramp architecture, will be described. Finally, we will show measurement results to confirm the monolithic ADC is suitable for small array, as 160 x 120 with low frame speed, while a column ADC is more compliant for higher array, as 640 x 480 with a 60 Hz frame speed or 1024 x 768 arrays.

The high level of accumulated expertise by ULIS and CEA/LETI on uncooled microbolometers made from amorphous silicon layer enables ULIS to develop 384 x 288 (1/4 VGA) IRFPA formats with 25 μm pixel-pitch designed for high end applications. This detector ROIC design relies on the same architecture as the full TV format ROIC one (detector configuration by serial link, user defined amplifier gain, windowing capability ...). The detector package is identical as the 384 x 288 / 35 μm and 640 x 480 / 25 μm ones, enabling an easier system update or less non recurrent cost for different systems developments. This paper will give results of the IRFPA characterization. NETD in the range of 30 mK (f/1, 300 K, 60 Hz) and operability higher than 99.99 % are routinely achieved.

The Laboratoire Infrarouge (LIR) of the Electronics and Information Technology Laboratory (LETI) has been involved in the development of Uncooled IR technology since 1986. Along these years, more and more technology improvements have been done at LETI and ULIS for large-scale production and broad commercialisation of advanced devices. With ULIS support, LETI is still pushing forward the technology, taking advantage of the well-established user-friendly properties of amorphous silicon. These developments are primarily driven by performance enhancement and cost reduction. In this outlook, the paper will first report on the recent improvements we have brought to microbolometer FPAs with 35 μm pixels, resulting in 11 mK NETD measurements. At the same time, 25 μm pixels have been demonstrated for high performance achievement. LETI is also developing a 1024 x 720, 17 μm pitch IRFPA that aims very challenging NETD < 40 mK; the paper will give the main concerns we have focused on to achieve this result. Finally, the LETI is preparing the next generation of very low cost Uncooled IRFPA, thanks to passing on all the microbolometer technology developments to the LETI 8 inches wafer facility.

The high level of accumulated expertise by ULIS and CEA/LETI on uncooled microbolometers made from amorphous silicon enables ULIS to develop 1024 x 768 (XGA) IRFPAs with 17 μm pixel-pitch to build up the currently available product catalog. This detector has kept all the innovations developed on the full TV format Read Out Integrated Circuit (ROIC) (detector configuration by serial link, two video outputs, low power consumption and wide electrical dynamic range ...). The specific appeal of this unit lies in the high image resolution it provides. The reduction of the pixel-pitch turns this XGA array into a product well adapted for high resolution and compact systems. In the last part of the paper, we will look more closely at high electro-optical performances of this IRFPA; we will highlight the wide thermal dynamic range as well as the high characteristics uniformity and high pixel operability achieved thanks to the mastering of the amorphous silicon technology coupled with the ROIC design.

The Laboratoire Infrarouge (LIR) of the Laboratoire d'Electronique et de Technologie de l'Information (LETI) has been involved in the development of microbolometers for over fifteen years. Two generations of technology have been transferred to ULIS and LETI is still working to improve performances of low cost detectors. Simultaneously, packaging still represents a significant part of detectors price. Reducing production costs would contribute to keep on extending applications of uncooled IRFPA to high volume markets like automotive. Therefore LETI is developing an on-chip packaging technology dedicated to microbolometers. This paper presents an original microcap structure that enables the use of IR window materials as sealing layers to maintain the expected vacuum level. The modelling and integration of an IR window suitable for this structure is also presented. This monolithic packaging technology is performed in a standard collective way, in continuation of bolometers' technology. The CEA-LETI, MINATEC presents status of these developments concerning this innovating technology including optical simulations results and SEM views of technical realizations.

The high level of accumulated expertise by ULIS and CEA/LETI on uncooled microbolometers made from an amorphous silicon layer enables ULIS to develop 384 x 288 (1/4 VGA) IRFPA format with 25 μm pixel-pitch designed for low end application. This detector has kept all the innovations developed on the full TV format ROIC (detector configuration by serial link, low power consumption or wide electrical dynamic range ...). The specific appeal of this unit lies in the miniaturization of the TEC-less (Thermo-Electric Cooler) package and its extremely light weight. The reduction of the pixel-pitch and the innovative package turn this array into a low cost product well adapted for mass production. We will present first the simple TEC-less operating mode which has been developed. The electro-optical characterization versus environmental temperature will be presented.

In this paper we report on new developments associated with SCD VOx μ-Bolometer product line. Lately, we have introduced the BIRD6401,2, which is a high-sensitivity (< 50 mK @ F/1, 60Hz) VGA format detector with 25 μm pitch. In the first part we present new data extracted from extensive measurements. These measurements were conducted under various environmental and power constraints, exhibiting superior temporal sensitivity, long-term stability and operational flexibility. In the second part we describe the system implications of special features that were embedded within the FPA. Explicitly, we will address the benefits of some special features aimed at lowering the system power dissipation while maintaining low temporal and spatial NETD. Finally, in the last part we outline SCD's future roadmap and development directions. We will elaborate on our latest progress towards improved pixel sensitivity (25mK@F/1), advanced 0.18um ROIC technology, and the combination of the two towards smaller pitch (17 μm) arrays.

BAE Systems has advanced its 17 μm pitch LWIR 640 x 480 microbolometer technology with improvements in pixel performance and introduction of a new 17 μm pitch ROIC. We have fabricated, characterized, and demonstrated high-yielding 17 μm pitch FPAs using our new ROIC, and have successfully demonstrated them at the system level. This new technology builds on our 28 μm FPA production experience and implements our high-performance single-level microbolometer process at 17 μm pitch. We present initial results and imagery. These 17 μm FPAs have exceptional performance and provide the path to next generation microbolometer applications.

RVS has made a significant breakthrough in the development of an athermal (TECless) 640 x 480 uncooled sensor with a unit cell size of 17 μm x 17 μm, and performance approaching that of the 25μm arrays. The sensor design contains a highly productized FPA and is designed to achieve excellent sensitivity (low NETD and low spatial noise) with good dynamic range. The improved performance is achieved through bolometer structure improvements, innovative ROIC design, and flexible, low power electronics architecture. We will show updated performance and imagery on these sensors, which is currently being measured at <50mK, f/1, 30 Hz. Pixel operability is greater than 99 % on most FPAs, and uncorrected responsivity nonuniformity is less than 3% (sigma/mean). The combination of reduced FPA pixel size and improved effective thermal sensitivity enhances performance by providing smaller, lighter-weight systems via reduced optics size. Or, alternatively, increased range via enhanced pixel resolution without increasing mass (maintaining optical size). We will also show the advancements made in our uncooled common architecture electronics in terms of reduced power and size for man-portable and missile applications.

This paper presents recent developments in next generation microbolometer Focal Plane Array (FPA) technology at L-3 Communications Infrared Products (L-3 CIP). Infrared detector technology at L-3 CIP is based on hydrogenated amorphous silicon (a-Si:H) and amorphous silicon germanium(a-SiGe:H). Large format high performance, fast, and compact IR FPAs are enabled by a low thermal mass pixel design; favorable material properties; an advanced ROIC design; and wafer level packaging. Currently at L-3 CIP, 17 micron pixel FPA array technology including 320x240, 640 x 480 and 1024 x768 arrays is under development. Applications of these FPAs range from low power microsensors to high resolution near-megapixel imager systems.

This paper describes the development of an enhanced performance passive infrared (PIR) upgrade for current pyroelectric security sensors. This new microbolometer technology has two significant advantages over current sensors: extended detection range and ability to detect developing fire or equipment failure. It may thus be seen as an IR fire detection device complementing other sensors whilst having an extended range for human detection. The results of measurements for targets of interest will be given for a technology demonstrator. Projected performance is described for a new 16x16 FPA, readout and optics designed specifically for this application.

The uncooled infrared imaging revolution began when ferroelectric detectors based on barium strontium titanate (BST) demonstrated NETDs less than 100mK at prices sufficiently low for commercial applications. Although this technology produces unsurpassed image quality, it has been largely supplanted by microbolometer technology, which can be fabricated in smaller pixel sizes, leading to smaller systems, and which produces a monolithic device using simpler fabrication processes than hybrid BST devices. In order to achieve the superior image quality of BST and at the same time benefit from the simpler manufacturing process and performance improvement potential of microbolometers, we have developed thin-film ferroelectric (TFFE) detector arrays. This technology has been under development for a decade, and it has lived up to its promise in spite of development difficulties. The image quality is superior to BST because of improved MTF, and it is superior to bolometers because of low spatial noise. TFFE arrays operate in all existing BST systems. The detectors require no temperature stabilization, and a single-point room-temperature calibration suffices for operation from -40°C to +85°C and beyond. Dynamic range is improved relative to BST by a factor of ten or more, and the optical local-area processing enables simultaneously viewing of detail in parts of the scene that differ by hundreds of degrees. It is also immune to sustained direct exposure to the sun.

This paper presents a new, low power readout circuit approach for uncooled resistive microbolometer FPAs. The readout circuits of the microbolometer detectors contain parallel readout channels whose outputs are driven and multiplexed on large bus capacitances in order to form the output of the readout circuit. High number of opamps used in the readout channel array and large output capacitances that these opamps should drive necessitates the use of high output current capacity structures, which results in large power dissipation. This paper proposes two new methods in order to decrease the power dissipation of the readout circuits for uncooled thermal FPAs. The first method is called the readout channel group concept, where the readout channel array is separated into groups in order to decrease the load capacitance seen by the readout channel output. The second method utilizes a special opamp architecture where the output current driving capacity can be digitally controlled. This method enables efficient use of power by activating the high output current driving capacity only during the output multiplexing. The simulations show that using these methods results in a power dissipation reduction of 80% and 91% for the readout channels optimized for a single output 384x288 FPA operating at 25 fps and for a two-output 640x480 FPA operating at 30 fps, respectively.

This paper introduces a new method to estimate the total absorption coefficient of uncooled infrared detectors. Current approaches in the literature model the infrared detectors as cascaded transmission lines representing the detector layers, and this model can easily be used to estimate the absorption coefficient if the detector has the same structure at every point. However, the state of the art uncooled infrared detectors do not have same structure at every point, making it not feasible to use this simple model. According to the proposed method, the detector structure is divided into subregions having different layer combinations, and the absorption coefficient of each subregion is calculated separately. Then, the area ratios of the subregions together with these coefficients are used in order to calculate the total absorption coefficient of the detector. As the estimation of the absorption coefficient for complex detector structures can easily be done, the absorption in the required part of the infrared spectrum can be optimized by adjusting the layer properties and layer thicknesses. This approach can be used both for single and double layer uncooled infrared detector structures.

This paper introduces an optimum reference detector design for uncooled resistive microbolometer focal plane arrays (FPAs). Reference detectors are mainly used for canceling the bias heating and for decreasing the ambient temperature dependence of the system. The proposed method in this paper determines an optimum thermal conductance value for the reference detector such that it is almost infrared blind, but still has the same bias heating characteristics as the active microbolometer detector. Infrared blindness of the reference detector is further increased by covering the top of the detector with an infrared reflective material. An optimum number of reference detectors are determined such that the over-heating of the reference detectors is prevented. Simulation results show that, with the use of the proposed method, it is possible to compensate the resistance change due to bias heating by 87% for the specific case where the detector has 60 kΩ resistance biased at 2 V, 10 ms thermal time constant, and 0.5x10^-7 W/K thermal conductance.

The function of most readout integrated circuits (ROIC) for microbolometer focal plane arrays (FPAs) is supplying a bias voltage to a microbolometer of each pixel, integrating the current of a microbolometer, and transferring the signals from pixels to the output of a chip. However, the scale down of CMOS technology allows the integration of other functions. In this paper, we proposed a CMOS ROIC involving a pixel-level analog-to-digital converter (ADC) for 320 × 240 microbolometer FPAs. Such integration would improve the performance of a ROIC at the reduced system cost and power consumption. The noise performance of a microbolometer is improved by using the pixelwise readout structure because integration time can be increased up to 1ms. A Pixel circuit is consisted of a background skimming circuit, a differential amplifier, an integration capacitor and a 10-bit DRAM. First, the microbolometer current is integrated for 1ms after the skimming current correction. The differential amplifier operates as an op-Amp and the integration capacitor makes negative feedback loop between an output and a negative input of the op-Amp. And then, the integrated signal voltage is converted to digital signals using a modified single slope ADC in a pixel when the differential amplifier operates as a comparator and the 10-bit DRAM stores values of a counter. This readout circuit is designed and fabricated using a standard 0.35μm 2-poly 3-metal CMOS technology.

Design of novel, portable and aurally undetectable cryogenically cooled infrared imagers often relies on compliant vibration protective pads for mounting the integrated dewar-detector-cooler assembly upon the imager's enclosure. Extensive analytical study and experimental effort have shown that for the best acoustic performance the visco-elastic properties of such pads need to be matched with the dynamic properties of the typically undamped enclosure, subjected to the tight limitations imposed on the low frequency cooler-induced line of sight jitter resulting from the oscillations of the gasodynamic torque and compliance of the above pads. Unfortunately, the regular approach to a design of the optimal vibration protective pad does not seem to exist. As a result, the development of the suitable vibration protective pad is widely regarded as a purely empirical process and requires a great deal of experimental trial-and-error effort. The authors are attempting to apply the regular finite element modeling approaches to an optimal design of such vibration protective pads. In doing so, they are making use of the full finite elements models of infrared imager enclosure with vibration mounted integrated dewar-detector-cooler assembly. The optimal geometry and dynamic properties of a compliant layer of vibration protective pad are evaluated using the optimisation procedure with purpose of attenuation the volume velocity of the active radiating surface. The theoretical findings are in fair agreement with the outcomes of the full-scale experimentation.

Low frequency vibration isolation of airborne gyrostabilised electrooptic payloads is an ultimate and life proven solution aimed at improving their imagery performance primarily during relatively quiet cruise flight. This portion of airborne mission is characterised by rather moderate environmental conditions, under which the vibration mounts operate mostly in a linear working range within the predefined working rattle space thus delivering their best performance. Compliant snubbers are the indispensable emergency components in such vibration protection arrangements coming into play during exposure to environmental extremes typical for the relatively short periods of the airborne mission such as take-off, landing, weapon application, etc. Their primarily objective is to safely protect the above soft vibration mounts from bottoming and disintegration without developing ruining impulsive accelerations compromising the integrity of the payload frame and the internal fragile components mounted upon it. The optimal approach to designing such a snubbed vibration isolator delivering a fail-safe environment for both payload frame and critical components subject to the tight constraints imposed on size, weight and price does not seem to exist. It is the author's intention to devise such an optimal design approach and to demonstrate its application to low frequency vibration mounted electro-optic payload comprising the vibration sensitive Integrated Dewar-Detector-Cooler Assembly.

Wide use of so called "dry-cooling" technology, eventually replacing the LN2 cooling approach in high-resolution instrumentation, such as Scanning Electronic Microscopes, Helium Ion Microscopes, Superconductive Quantum Interference Devices, etc., motivates further quieting of appropriate cryogenic refrigerators. Linear Stirling cryogenic refrigerators are known to be a major source of harmful vibration export compromising the overall performance of vibration-sensitive equipment. The dual-piston approach to a design of a linear compressor yields inherently low vibration export and, therefore, is widely accepted across the industry. However, the residual vibration disturbance originated even from the technological tolerances, natural wear and contamination cannot be completely eliminated. Moreover, a vibration disturbance produced by a pneumatically driven cold head is much more powerful as compared to this of a compressor. The authors successfully redesigned the existing Ricor model K535 Stirling cryogenic refrigerator for use in vibration-sensitive electronic microscopy, where the image resolution is specified in angstroms. The objective was achieved by passive mechanical counterbalancing of the expander portion of the refrigerator, in a combination with an active two-axis control of residual vibrations, relying on National Instruments CompactRIO hardware, incorporating a real-time processor and reconfigurable FPGA for reliable stand-alone embedded application, developed using LabVIEW graphical programming tools. The attainable performance of the Ultra-Low Vibration linear Stirling cryogenic refrigerator RICOR model K535-ULV was evaluated through the full-scale experimentation.

The intent of this investigation is to replace the low fill factor visible sensor of a Cellular Neural Network (CNN) processor with an InGaAs Focal Plane Array (FPA) using both bump bonding and epitaxial layer transfer techniques for use in the Ballistic Missile Defense System (BMDS) interceptor seekers. The goal is to fabricate a massively parallel digital processor with a local as well as a global interconnect architecture. Currently, this unique CNN processor is capable of processing a target scene in excess of 10,000 frames per second with its visible sensor. What makes the CNN processor so unique is that each processing element includes memory, local data storage, local and global communication devices and a visible sensor supported by a programmable analog or digital computer program.

We present architectures, CMOS circuits and CMOS chips to process image flows at very high speed. This is achieved by exploiting bio-inspiration and performing processing tasks in parallel manner and concurrently with image acquisition. A vision system is presented which makes decisions within sub-msec range. This is very well suited for defense and security applications requiring segmentation and tracking of rapidly moving objects.

Polaris Sensor Technologies, Inc. is identifying target pixels in IR imagery at signal to noise (SNR) ranges from 1.25 to 3 with a mixed set of algorithms that are candidates for next generation focal planes. Some of these yield less than 50 false targets and a 95% probability of detection in this low SNR range. What has been discovered is that single frame imagery combined with IMU data can be input into a host of algorithms like Neural Networks and filters to isolate signals and cull noise. Solutions for nonlinear thresholding approaches can be solved using both genetic algorithms and neural networks. What is being addressed is how to implement these approaches and apply them to point target detection scenarios. The large format focal planes will flood the down stream image processing pipelines used in real time systems, and this team wonders if data can be thinned near the FPA using one of these techniques. Delivering all the target pixels with a minimum of false positives is the goal addressed by the group. Algorithms that can be digitally implemented in a ROIC are discussed as are the performance statistics Probability of Detection and False Alarm Rate. Results from multiple focal planes for varied scenarios will be presented.

We address the problem of target discrimination using hyperspektral and multisensor data. The problem is of significance to detection and classification of low signature targets such as landmines. The problem will be described with stochastic models and by using information theoretic concepts we will derive limits to system performance in terms of probability of false alarm and probablility of detection. The stochastic model is suitable to evaluate and optimize sensor parameters and sensor configurations. We will for example investigate how much information different combinations of spectral and spatial data will give. With the stochastic model sensors with different types of characteristics can be compared and the contribution of the different sensors and configurations can be evaluated. Besides the optimization of different sensor configurations with respect to specific applications, the stochastic model will be used to evaluate different anomaly detectors. The strength of our approach is shown by examples from an analysis of measurements on a natural scene with various objects using an electro-optical hyperspectral sensor and several other sensors. We expect that our approach will give significant indications on how to choose and configure sensors for efficient and reliable target discrimination.

We have previously discussed the potential of using a Hg_1-xCd_xTe source as a reference plane for the non-uniformity correction of thermal imagers and which is being developed as an option for the UK 3rd generation, high performance thermal imaging program (Albion). In this paper we will present our first results on a large area (1.5 cm x 1.5 cm) source which was grown on a silicon substrate and can simulate a range of temperatures from -10 °C to +30 °C. Due to the fast switching speed, the apparent temperature can be changed on a frame by frame basis. Also, the operation of the device can be synchronized to the integration time of the camera to reduce the mean power requirements by a factor of 10 and reduce thermal heating effects. The main applications for Hg_1-xCd_xTe devices as high-performance, cryogenically-cooled detectors typically require very low drive currents. The use of this material for large-area LEDs has generated new challenges to deal with the high peak currents. These are typically in the range 1-2 A/cm² for a MWIR waveband source and have led to a need to reduce the common impedance, reduce the contact resistances and consider the effects of current crowding.

Active systems, using a near-infrared pulse laser and a fast, gated detector, are now adopted for most long range imaging applications. This concept is often called laser-gated imaging (LGI) or burst-illumination LIDAR (BIL). The SELEX solid state detector is based on an array of HgCdTe avalanche photodiodes, and a custom-designed CMOS multiplexer to perform the fast gating and photon signal capture. This paper describes two recent developments. The first is aimed at reducing the size, weight, power and cost of steerable platforms which often have to contain a large number of electrooptic tools such as lasers, range finders, BIL, thermal imaging and visible cameras. A dual-mode infrared detector has been developed with the aim of shrinking the system to one camera. The detector can be switched to operate as a passive thermal imager, a laser-gated imager or a solar flux imager. The detector produces a sensitivity in the MW thermal band of 16-18mK and a sensitivity in the BIL mode as low as 10 photons rms, in other words close to the performance of dedicated imagers. A second development was to extend the current BIL capability to 3D. In complex scenes, with camouflage and concealment, the ability to generate 3D images provides a signal-to-clutter advantage. Also in airborne applications, especially, it is useful to have 3D information to provide agile, feedback control of the range gating in a dynamic environment. This report describes the development of the 3D detector and camera, and the results of field trials using a prototype system.

CEA Leti has demonstrated the good performances of its MWIR HgCdTe avalanche photodiode arrays. Gains above 20 at a moderate bias voltage of 5V have typically been measured with an excess noise factor of only 1.2. The next generation of infrared focal plane arrays will take advantage of these characteristics to address new applications, reduce system complexity and enhance performances. One of the main opportunities offered by avalanche photodiode detectors concerns long range active imaging. This paper reports the development of two novel pixel architectures for 3D active imaging based on flash LADAR technology. Both pixels have been designed in a standard 0.35μm CMOS process and perform time-of-flight measurement in addition to 2D intensity imaging with a single emitted laser pulse. The analog input circuits have been optimized to allow fast pulse detection while providing robustness to process variability. A small readout IC demonstrator has been fabricated and coupled to a 10x10 avalanche photodiode array at 40μm pixel pitch. The first test results in lab conditions show good electro-optical performances with a ranging resolution around 30cm (2ns).

We report the latest developments of MW HgCdTe electron initiated avalanche photo-diodes (e-APDs) focal plane arrays (FPAs) at CEA-LETI. The MW e-APD FPAs are developed in view of ultra-sensitive high dynamic range passive starring arrays, active 2D/3D and dual-mode passive-active imaging, which is why both the passive imaging performance and the gain characteristics of the APDs are of interest. A passive mode responsivity operability of 99.9% was measured in LPE and MBE e-APDs FPAs associated with an average NETD=12mK, demonstrating that dual mode passive-active imaging can be achieved with LETI e-APDs without degradation in the passive imaging performance. The gain and sensitivity performances were measured in test arrays and using a low voltage technology (3.3V) CTIA test pixel designed for 3D active imaging. The CTIA and test arrays measurements yielded comparable results in terms of bias gain dependence (M=100 at V_b=-7V), low excess noise factor (=1.2) and low equivalent input current (I_{eq_in}<1pA). These results validated the low voltage CTIA approach for integrating the current from a HgCdTe e-APD under high bias. The test array measurements demonstrated a relative dispersion below 2% in both MBE and LPE e- APDs for gains higher than M>100, associated with an operability of 99%. The operability at I_{eq_in}<1pA at M=30 was 95%. A record low value of Ieq_in=1fA was estimated in the MBE e-APDs at M=100, indicating the potential for using the MW e-APDs for very low flux applications. The high potential of the MW e-APDS for active imaging was demonstrated by impulse response measurements which yielded a typical rise time lower than 100ps and diffusion limited fall time of 900ps to 5ns, depending on the pixel pitch. This potential was confirmed by the demonstration of a 2ns time of flight (TOF) resolution in the CTIA e-APD 3D pixel. The combined photon and dark current induced equivalent back ground noise at f/8 with a cold band pass filter at λ=1.55μm was 2 electrons rms for an integration time of 50ns.

Advanced LADAR receivers enable high accuracy identification of targets at ranges beyond standard EOIR sensors. Increased sensitivity of these receivers will enable reductions in laser power, hence more affordable, smaller sensors as well as much longer range of detection. Raytheon has made a recent breakthrough in LADAR architecture by combining very low noise ~ 30 electron front end amplifiers with moderate gain >60 Avalanche Photodiodes. The combination of these enables detection of laser pulse returns containing as few as one photon up to 1000s of photons. Because a lower APD gain is utilized the sensor operation differs dramatically from traditional "Geiger mode APD" LADARs. Linear mode photon counting LADAR offers advantages including: determination of intensity as well as time of arrival, nanosecond recovery times and discrimination between radiation events and signals. In our talk we will present an update of this development work: the basic amplifier and APD component performance, the front end architecture, the demonstration of single photon detection using a simple 4 × 4 SCA and the design and evaluation of critical components of a fully integrated photon counting camera under development in support of the Ultra-Sensitive Detector (USD) program sponsored by AFRL-Kirtland.

The Molecular Beam Epitaxy (MBE) approach was under investigation for several years to prepare both the very large array fabrication and the 3rd generation developments. This large step in Infrared (IR) detector mass production is also necessary for producing third generation of IR detectors such as bicolor and dual band FPAs which use more complex multi hetero-junctions architectures. These new advanced HgCdTe technologies necessary for third generation developments have been validated and their producibility have been improved. As far as dual band IR detectors are concerned, the technologies are developed and a full TV format (24μm pixel pitch) is currently under development with a first application in bicolor within medium waveband. Future improvements including avalanche photodiodes (APD), will lead to more compact systems as well as a low cost approach.

The use of silicon substrates has been very successful for producing large area focal plane arrays operating in the MWIR waveband using the MBE growth process. More recently, promising results have been obtained in the LWIR waveband using a MOVPE growth process on a buffered silicon substrate. The MOVPE growth process is also suitable for more complex multi-layer structures and we have now used this technique to produce our first MW/LW dual waveband focal plane arrays. In this paper we show that close to background limited performance can be achieved in both wavebands, however the main challenge with arrays grown on silicon is to obtain low defect counts. These first arrays are promising in this respect and operabilities of 99.4% and 98.2% have been achieved in the MWIR band and LWIR band respectively. The availability of dual waveband arrays allows the correlation of defects in the two wavebands to be compared. In general, we find that the correlation is low and this suggests that defect generation mechanisms which would affect both bands (such as threading dislocations) are currently not the main source of defective devices in MOVPE grown devices on silicon.

Raytheon has developed a 3rd-Generation FLIR Sensor Engine (3GFSE) for advanced U.S. Army systems. The sensor engine is based around a compact, productized detector-dewar assembly incorporating a 640 x 480 staring dual-band (MW/LWIR) focal plane array (FPA) and a dual-aperture coldshield mechanism. The capability to switch the coldshield aperture and operate at either of two widely-varying f/#s will enable future multi-mode tactical systems to more fully exploit the many operational advantages offered by dual-band FPAs. RVS has previously demonstrated high-performance dual-band MW/LWIR FPAs in 640 x 480 and 1280 x 720 formats with 20 μm pitch. The 3GFSE includes compact electronics that operate the dual-band FPA and variable-aperture mechanism, and perform 14-bit analog-to-digital conversion of the FPA output video. Digital signal processing electronics perform "fixed" two-point non-uniformity correction (NUC) of the video from both bands and optional dynamic scene-based NUC; advanced enhancement processing of the output video is also supported. The dewar-electronics assembly measures approximately 4.75 x 2.25 x 1.75 inches. A compact, high-performance linear cooler and cooler electronics module provide the necessary FPA cooling over a military environmental temperature range. 3GFSE units are currently being assembled and integrated at RVS, with the first units planned for delivery to the US Army.

This paper describes the design, fabrication and performance of dual-band MW/LW infrared detectors made from HgCdTe (MCT) grown by Metal Organic Vapour Phase Epitaxy (MOVPE). The detectors are staring, focal plane arrays consisting of HgCdTe mesa-diode arrays bump bonded to silicon read-out circuits. Each mesa has one connection to the ROIC and the bands are selected by varying the applied bias. Arrays of 320x256 pixels on a 30 μm pitch have performed exceedingly well. For example, arrays with a cut-off wavelength of 5 μm in the MW (mid-wave) band and 10 μm in the LW (long-wave) band have median NETDs of 10 and 17 mK and defect levels of 0.3% and 0.05%, in the MW and LW bands respectively. Interestingly the LW defect level is often lower than the MW defect level and the defects are not correlated; i.e. a pixel that is defective in the MW band is usually not defective in the LW band. Arrays of 640x512 pixels on a 24 μm pitch have been developed. These use a read-out integrated circuit (ROIC) that has two capacitors per pixel and the ability to switch bands during a frame giving quasi-simultaneous images. The performance of these arrays has been excellent with NETDs of 14mK in the MW band and 23mK in the LW band. Dual band-pass filters have been designed and built into a detector.

Mid-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) 1024x1024 pixel InGaAs/GaAs/AlGaAs based quantum well infrared photodetector (QWIP) focal planes and a 320x256 pixel dualband pixel co-registered simultaneous QWIP focal plane array have been demonstrated as pathfinders. In this paper, we discuss the development of 1024x1024 MWIR/LWIR dualband pixel co-registered simultaneous QWIP focal plane array.

A barrier photodetector is a device in which the light is absorbed in a narrow bandgap semiconductor layer whose bands remain essentially flat or accumulated at the operating bias so that all carrier depletion is excluded. In a conventional photodiode below a threshold temperature T₀, typically 130-150K for MWIR devices, the dark current is due to Generation-Recombination (G-R) centres in the depletion layer. In a barrier detector, the absence of depletion in the narrow bandgap semiconductor ensures that the G-R contribution to the dark current is negligible. The dark current in the barrier detector is thus dominated by the diffusion component, both above and below T₀. Therefore, at a given temperature below T₀, a barrier detector will exhibit a lower dark current than a conventional photodiode with the same cut-off wavelength. Alternatively, for a given dark current, a barrier detector will operate at a higher temperature than a conventional photodiode, provided that this temperature is below T₀. Device architectures are presented for barrier detectors with photon absorbing layers based on InAs_1-xSb_x alloys and type-II InAs/GaSb superlattices (T2SL). The thermionic and tunneling components of the dark current are analyzed and shown to be negligible for typical device parameters. An operating temperature of ~150K is estimated for a MWIR barrier detector with f/3 optics and a cut-off wavelength of 4.2μ.

The design and development of a new, flexible, linear array readout integrated circuit (ROIC) for a new family of linear array detectors are described in this paper. The detector technology used is based on indium-gallium-arsenide (InGaAs) and includes low dark current versions with room temperature wavelength response cutoff of 1.7 microns and versions with altered stoichiometry to shift the room temperature absorbance cutoff wavelength to 2.55 microns. Discussion includes choice of features to cover many applications, testing methods, and evaluation of the first versions produced. The result will be a highly flexible linear array family, with versions matched to biological imaging, hot process inspection, pharmaceutical pill inspection, agricultural sorting and contaminant rejection, plastics recycling, moisture monitoring of continuous web processes.

LETI has been involved in IRFPA development since 1978; the design department (LETI/DCIS) has focused its work on new ROIC architecture since many years. The trend is to integrate advanced functions into the CMOS design to achieve cost efficient sensors production. Thermal imaging market is today more and more demanding of systems with instant ON capability and low power consumption. The purpose of this paper is to present the latest developments of fixed pattern noise continuous time correction. Several architectures are proposed, some are based on hardwired digital processing and some are purely analog. Both are using scene based algorithms. Moreover a new method is proposed for simultaneous correction of pixel offsets and sensitivities. In this scope, a new architecture of readout integrated circuit has been implemented; this architecture is developed with 0.18μm CMOS technology. The specification and the application of the ROIC are discussed in details.

The CMOS silicon focal plan array technologies hybridized with infrared detectors materials allow to cover a wide range of applications in the field of space, airborne and grounded-based imaging. Regarding other industries which are also using embedded systems, the requirements of such sensor assembly can be seen as very similar; high reliability, low weight, low power, radiation hardness for space applications and cost reduction. Comparing to CCDs technology, excepted the fact that CMOS fabrication uses standard commercial semiconductor foundry, the interest of this technology used in cooled IR sensors is its capability to operate in a wide range of temperature from 300K to cryogenic with a high density of integration and keeping at the same time good performances in term of frequency, noise and power consumption. The CMOS technology roadmap predict aggressive scaling down of device size, transistor threshold voltage, oxide and metal thicknesses to meet the growing demands for higher levels of integration and performance. At the same time infrared detectors manufacturing process is developing IR materials with a tunable cut-off wavelength capable to cover bandwidths from visible to 20μm. The requirements of third generation IR detectors are driving to scaling down the pixel pitch, to develop IR materials with high uniformity on larger formats, to develop Avalanche Photo Diodes (APD) and dual band technologies. These needs in IR detectors technologies developments associated to CMOS technology, used as a readout element, are offering new capabilities and new opportunities for cooled infrared FPAs. The exponential increase of new functionalities on chip, like the active 2D and 3D imaging, the on chip analog to digital conversion, the signal processing on chip, the bicolor, the dual band and DTI (Double Time Integration) mode ...is aiming to enlarge the field of application for cooled IR FPAs challenging by the way the design activity.

The authors tried real-time imaging of THz radiation from Quantum Cascade Laser (QCL), using vanadium oxide (VOx) microbolometer focal plane arrays (FPAs) of 320x240 with pitches of 37 μm and 23.5 μm as well as 640x480 with 23.5μm pitch. The QCL has such parameters as 3.1 THz emission frequency (97μm in wavelength), 300-400 nsec pulse width, 1.07 msec repetition period, 30 mW peak intensity, 15K operation temperature. The THz radiation from QCL is collimated by off-axis parabola (OAP) and focused on FPA by another OAP. The 10 μm range infrared radiation from scene is blocked by sapphire disk or metal mesh filter. Noise Equivalent Power (NEP) at 3.1 THz is estimated to be 200~400 pW.

The Longwave Infrared Camera (LIR), which mounts an uncooled micro-bolometer array (UMBA), is under development for the Japanese Venus orbiter mission, PLANET-C. LIR detects thermal emission from the top of the sulfur dioxide cloud in a wavelength region 8--12 μm to map the cloud-top temperature which is typically as low as 230 K. The requirement for the noise equivalent temperature difference (NETD) is 0.3 K. Images of blackbody targets in room temperature (~300 K) and low temperature (~230 K) have been acquired in a vacuum environment using a prototype model of LIR, showing that the NETD of 0.2 K and 0.8 K are achieved in ~300 K and ~230 K, respectively. We expect that the requirement of NETD<0.3 K for ~230 K targets will be achieved by averaging several tens of images which are acquired within a few minutes. The vibration test for the UMBA was also carried out and the result showed the UMBA survived without any pixel defects or malfunctions. The tolerance to high-energy protons was tested and verified using a commercial camera in which a same type of UMBA is mounted. Based on these results, a flight model is now being manufactured with minor modifications from the prototype.

We have developed a two-dimensional thermal infrared array sensor called the Infrared Position Sensitive Detector (IRPSD). The IRPSD has two thermometers for row and column in a pixel, and thermometers in a row or column are serially connected. The serial connection of thermometers produces the sum of signals from the pixels in each row and column. With this array architecture, the IRPSD can extract some specific information without digital image processing. The IRPSD is capable of performing position detection and number counting operations for hot (or cold) objects. Information on the position can be obtained from the row and column that has maximum outputs, and the number can be counted by adding all outputs in rows or columns. We adapt a thermopile made of a p-type polysilicon and aluminum as thermometers. We have developed two IRPSDs. One is a prototype device for verifying the concept, and the other is an improved device with higher responsivity. Evaluation of these devices has shown that the IRPSD has the potential to be applied to a wide variety of applications.

This paper describes three low-cost infrared focal plane arrays (FPAs) having a 1,536, 2,304, and 10,800 elements and experimental vehicle systems. They have a low-cost potential because each element consists of p-n polysilicon thermocouples, which allows the use of low-cost ultra-fine microfabrication technology commonly employed in the conventional semiconductor manufacturing processes. To increase the responsivity of FPA, we have developed a precisely patterned Au-black absorber that has high infrared absorptivity of more than 90%. The FPA having a 2,304 elements achieved high resposivity of 4,300 V/W. In order to reduce package cost, we developed a vacuum-sealed package integrated with a molded ZnS lens. The camera aiming the temperature measurement of a passenger cabin is compact and light weight devices that measures 45 x 45 x 30 mm and weighs 190 g. The camera achieves a noise equivalent temperature deviation (NETD) of less than 0.7°C from 0 to 40°C. In this paper, we also present a several experimental systems that use infrared cameras. One experimental system is a blind spot pedestrian warning system that employs four infrared cameras. It can detect the infrared radiation emitted from a human body and alerts the driver when a pedestrian is in a blind spot. The system can also prevent the vehicle from moving in the direction of the pedestrian. Another system uses a visible-light camera and infrared sensors to detect the presence of a pedestrian in a rear blind spot and alerts the driver. The third system is a new type of human-machine interface system that enables the driver to control the car's audio system without letting go of the steering wheel. Uncooled infrared cameras are still costly, which limits their automotive use to high-end luxury cars at present. To promote widespread use of IR imaging sensors on vehicles, we need to reduce their cost further.

The aim of this study is to design and develop a wireless distributed pyroelectric infrared sensor system which can track multiple humans. By using TI’s micro-controller MSP430149 and RF transceiver TRF6901, we have implemented a prototype multiple human tracking system, which can track two people in both follow-up and crossover scenarios with average tracking errors less than 0.5 m. The proposed wireless distributed infrared sensor system can not only run as a stand alone inmate/patient monitoring system under all illumination conditions, but also serve as a complement for conventional video and audio human tracking systems.

One goal of our research is to make wireless distributed pyroelectric sensor nodes an alternative to the centralized infrared video sensors, with lower cost, lower detectability, lower power consumption and computation workload, and less privacy infringement. To improve the identification rate and the number of people that can be recognized, one-by-one or simultaneously, we employ multiple sensor nodes to leverage the performance of the distributed sensor system. By using multiple sensor nodes the proposed biometric modality can be extended to the higher-security applications of walker recognition, and facilitate multiple human tracking.

Double-functional (optical and electrical) interferometer was realized using holographic recording of dynamic gratings in the semiconductor crystals of CdTe: V, CdTe:Ti and ferroelectric-pyroelectric crystal Sn2P2S6 (SPS). Also we introduce novel holographic single-beam wave-front division interferometer that is compact, do not need stabilization and are well suited for real-world applications.

Verification of the low measurement uncertainty of a group of eight newly developed pyroelectric detectors at the output of a traditional monochromator is described. The frequency compensated hybrid detector-amplifier packages have fixed 1010 Ω feedback resistors. The characterizations verified that the 3 dB upper roll-off frequencies of the signal-gain curves are close to 100 Hz and the temperature coefficient of responsivity is 0.14 %/oC. The hybrid packages were tested for noise performance in the f/8 beam of a grating monochromator between 900 nm and 2.7 μm. The monochromator output beam-power, the output signal, and the output noise of the hybrid packages were measured and compared. The NEPs were between 3.3 nW/Hz1/2 and 10 nW/Hz1/2. The relative standard uncertainty of the noise measurements was 20 % (k=1). The noise tests were utilized to select hybrid packages with NEPs that are one order of magnitude lower than that of traditional pyroelectric detectors and current-amplifiers. The power responsivity of one hybrid was calibrated against an absolute cryogenic radiometer. With this detector, the measured signal-to-noise ratios were higher than 400 between 1.1 μm and 2.1 μm and 250 at 2.5 μm using a lock-in integrating time-constant of 1 s. The noise test results show that using a hybrid detector with an NEP equal to the group average of about 6 nW/Hz1/2, spectral responsivity measurements with a relative standard uncertainty of 0.2 % to 0.4 % (k=1) can be achieved.

Historically, the natural structure of Indium Gallium Arsenide backside illuminated FPAs has allowed them to detect light with wavelengths between 0.9 and 1.7 μm. However, new wafer growth and processing methods have allowed extended response InGaAs imagers to be used in high sensitivity cameras to detect light down to 0.7 μm. These extended response imagers hold many advantages over standard cut-on InGaAs. One of these advantages is being able to detect beacons, lasers, and illuminators in the 800-900 nm range, light sources that have historically only been detectable with I²CCD cameras or night vision tubes, while simultaneously being able to detect the longer wavelength convert illuminators and lasers. Another advantage is capturing any additional available photons with wavelengths between 0.7 μm and 0.9 μm. This improves overall imaging capability in most low light level situations. This paper will address the methods used to achieve stable, high sensitivity extended response imagers, as well expand on the applications of this breakthrough.

Short-wave infrared detectors and regular-glass optics are used to construct a calibrator for infrared collimators. The advantages of using short-wave infrared detectors with thermo-electric cooling instead of cryogenically-cooled infrared detectors are shown. Diffraction-limited imaging is obtained using off-the-shelf achromats for rejection of stray radiation and for collection of the thermal radiation. The design of a prototype calibrator is shown and the noise-equivalent irradiances (NEI) are determined using a separately calibrated, off-axis infrared collimator. The measured NEI of 7 fW/cm2 demonstrates at least several orders of magnitude better performance than existing infrared calibrators.

As more and more spectral ranges are used by different threat detecting sensors, the effectiveness of a countermeasure is becoming more and more dependent on how similar its emitted spectrum is to the object that it is supposed to simulate. As a result, the need to model and test the countermeasure radiometric output (in radiance units) and contrast (in radiant intensity units) or effective temperature at different wavelengths simultaneously increases in importance during both R&D and production for both the producer of countermeasures (to confuse the seekers) and the producer of missile seekers (to prevent seeker confusion). We have developed a family of multi-spectral radiometers (ColoRad) specifically designed to quantitatively measure countermeasure spectral signatures dynamically for precise characterization. In this paper we describe the design of such instrumentation, including the various modes of operation and highlighting the important instrument features for the present application. In addition an example of measurement is given here to demonstrate its usefulness. The ColoRad performance parameter values are also given in this paper.

A high-speed flexible transistor made with an ultrapure carbon nanotube (CNT) solution is reported. The carrier transport layer of the CNT-based flexible transistor is formed at room temperature by dispensing a tiny droplet of an electronics-grade CNT solution. Ultra high field-effect mobility of ~ 48,000 cm2/(V×s) has been demonstrated on a thin-film field effect transistor (TFT). A simple trans-impedance voltage follower circuit was made using the CNT-TFT on a transparency film. The circuit exhibited a high modulation speed of 312 MHz and a large current-carrying capacity beyond 20 mA. The transparency and the sheet resistance of the CNT-film were also characterized at different wavelengths. The ink-jet printing-compatible process would enable mass production of large-area electronic circuits on virtually any desired flexible substrate at low cost and high throughput.

Rare earth doped upconverting nanoparticles have been synthesized via laser vaporization controlled condensation (LVCC) and their photoluminescence properties were characterized using 980 nm laser diode excitation. This procedure is highly tunable, specifically by increasing the Yb³⁺ to Er³⁺ concentration the observed green emission decreases and the observed red emission increases. We have also shown that nearly equal peaks of blue, green and red emissions producing a virtually white upconverter could be synthesized by appropriately mixing Tm³⁺, Ho³⁺, and Er³⁺. We have also investigated the upconversion efficiency in a variety of lattices including Y₂O₃, Gd₂O₃ and La₂O₃. TEM confirmed that the as-formed particles were ~ 10 nm in size and XRD indicated that the overall crystal structure was predominately cubic.

This paper reports preliminary results obtained on 1.7µm InGaAs, Vis-InGaAs, extended-wavelength InGaAs, InSb, and HgCdTe 320x256 FPAs fabricated at Judson. Test structures designed to characterize fundamental detector parameters are presented. FPA performance and imaging analysis are reported. Possible performance improvements by means of architectural design and fabrication process refinement are described. Future development plan and preliminary experimental results on FPAs with larger format and smaller pitch are also discussed. Relatively low dark current and NEI values, as well as high operability, are achieved for 1.7µm InGaAs FPAs at room temperature. High quantum efficiency in the visible wavelength range is achieved for Vis-InGaAs FPAs. Low NETD values are achieved for InSb FPAs at LN2 and MWIR HgCdTe FPAs at -70°C (203°K).

The interdigitation concept demonstration utilized lc[60 K] ~ 15 &mgr;m HgCdTe pixels in a 96 × 96 array format. Each pixel consisted of four interdigitated sub-pixels. Electronic circuitry on the ROIC deselects defective sub-pixels. High detector response is maintained across the pixel, even if one or two interdigitated sub-pixels are deselected, because interdigitation provides that the predominance of minority carriers photogenerated in the pixel is collected by the selected sub-pixels. An interdigitated sub-pixel is deselected where there is a short in at least one of the detectors of the sub-pixel. The configuration of the interdigitated sub-pixels for a pixel is selected such that photogenerated charge carriers generated anywhere within the pixel would be collected by any adjacent, interdigitated sub-pixels within the same pixel that are not deselected because the diffusion length for the charge carriers is long enough. Deselected interdigitated sub-pixels are disconnected so that no charge will be collected on deselected sub-pixels. Therefore, only detectors of adjacent selected interdigitated sub-pixels collect substantially all of the photogenerated charges corresponding to the impinging radiation. Photoresponse modeling of the interdigitated subpixel approach was performed. An example is that for a 20 &mgr;m diffusion length, the calculated QE changed from 85 % with 0 sub-pixels deselected, to 78 % with 1 sub-pixel, 67 % with two sub-pixels and 48 % with three sub-pixels deselected. A good comparison has been obtained between modeled and measured performance as a function of sub-pixel deselect.