Since 1988, China has launched three polar-orbital and two geostationary meteorological satellites. This paper describes the remote sensors onboard those satellites and their main performance, and briefly presents the future development of remote sensors.

The Infrared Multispectral Scanner (IRMSS) and the CCD Camera were two of the three remote sensing payloads for China-Brazil Earth Resources Satellite (CBERS). This paper introduces their development and operation. The IRMSS is a scanning imaging multispectral remote sensor. It has 4 bands, one panchromatic band (0.50-0.90micrometers ), two short- wave infrared bands (1.55-1.75micrometers , 2.08-2.35micrometers ) and one long-wave infrared band (10.4-12.5micrometers ). Its swath is 120km. The pixel resolution of the panchromatic band and short-wave bands is 78m while the long-wave infrared band is 156m. The CCD Camera is a pushbroom multispectral remote sensor. It has 5 bands, i.e. 0.45-0.52micrometers , 0.52-0.59micrometers , 0.63-0.69micrometers , 0.77-0.89micrometers and 0.51-0.73micrometers . Its swath is 113km and pixel resolution is 20m. The development of the IRMSS and the CCD Camera took about 11 years. On October 14, 1999 the two sensors were sent into orbit. The in-orbit test proved that they had met their specifications.

Today, it becomes more and more important to provide high quantification of remote sensing information to study and utilize earth resources. Georeferenced images, as advanced remote sensing information, consist of ground images with their 3D positioning coordinates and play a key role in earth observation. So, the quantification of georeferenced images is attracting people's attentions. In this paper, an airborne sensor called the ASLRIS system for producing georeferenced images is introduced first. In succession, the fundamental and quantification of georeferenced images is analyzed, where the positioning quantification as well as its limiting factors is especially discussed on the system. Then some technical methods applied in the ASLRIS system to improve the positioning quantification of georeferenced images are studied emphatically. The technique of waveform digitization for precise time-of-flight discrimination and the technique of tapped delay line for precise time interval measurement are accomplished to improve the accuracy of airborne scanning laser ranging. Some mechanic calibrations and parameter measurements are implemented to synthetically improve the positioning accuracy. The conic scanning technique is applied to improve the horizontal positioning resolution. Finally, some test results of the ASLRIS system are described. It is indicated that the quantification level of georeferenced images is improved obviously.

In this paper, taking the Digital Infrared Thermal Imager as the object of study, infrared thermal image and its noise types and characteristics are researched into in detail, and the image noise theoretical model is described unitedly by the time and space domain stochastic process. On the basis of these, Infrared Thermal Image Processing System is set up. New types of time and space domain image processing theory and technique-interframe comparison denoise process and adaptive mode filter are put forward and taken to suppress infrared thermal image noise. Theoretical and experimental results show that interframe comparison denoise process and adaptive mode filter suppress infrared thermal image noise more effectively than image frame-accumulation method and mode filter. At last, Infrared Thermal Imager Signal and Noise Test and Analysis System is developed specially, and the test and analysis evaluation on the original and processed images are carried out.

A grayscale morphological filter has been developed for small target detection in Infrared Search and Track (IRST) applications. Applying morphological open in horizontal and vertical directions respectively, utilizing the property of open and choosing the proper one pixel by pixel from the processed data in horizontal and vertical directions, the algorithm exhibits perfect results in estimating background accurately. Represented by the stereo description of images, the performance of the algorithm could be seen intuitively in Section 4. Real IR images with cloud, ground objects as backgrounds are tested, and the detection result is satisfactory. Furthermore, this algorithm has the potential of parallel processing, which is of great importance in real-time implementation.

This paper describes a low cost, high performance, compact imager. It utilizes 64x64 pixels InSb staring FPA sensor that is a miniature dewar cooler assembly, cooled by a J-T cooler. The imager achieves NETD of less than 0.1K at 300K background with f/1.4 optics at 50Hz frame rate. It can be used in imaging guidance or other military and civil systems.

HgCdTe is the most important material for infrared detectors. Multispectral band infrared detectors made of HgCdTe are developed for space-borne remote sensing in China. This paper describes the performances and related aspects of these detectors.

The detection of SWIR radiation is very useful for earth resources, space observation and military applications. In this paper, we present a new development of short-wave infrared MCT detector assembly for resources remote sensing. Detectors operate at 150K with the uncooled preamplifer. The assembly spectral response ranges are from 1.55-1.75micrometers and 2.08-2.35micrometers . D*_(Delta (lambda) ) achieves 4- 10x10¹¹Jones, R₀A product is 10⁴- 10⁵(Omega) cm².

256x290 diffractive microlens arrays have been designed by considering the correlative optical and processing parameters for PtSi focal plane array. The microlens arrays were designed to operate at (lambda) equals4micrometers , with a lens size of 50micrometers x33micrometers and the lens speed f/2.1 located on the backside of PtSi focal plane array chip. The diffractive microlens arrays have been fabricated on the backside of PtSi focal plane array chip by successive photolithography and Ar⁺ ion-beam etching technique. The alignment of microlens arrays with PtSi focal plane array was completed by a backside aligner with IR light source. The practical processes and fabrication method are discussed. The optical characteristics and performance parameters of PtSi FPA with diffractive microlens arrays are presented.

For the purpose of cooling space-borne infrared detectors, a high frequency miniature pulse tube refrigerator (PTR) has been developed in our laboratory. The 1.06cc linear compressor made by our laboratory is used to generate the pressure waves. In order to be conveniently used, the pulse tube refrigerator has adopted the multi-bypass, co-axial and symmetry spray nozzle phase shifter structure. The cold finger of the refrigerator is only 72mm long with outer diameter 9mm. This paper also presents the recently experimental result. When the hot end of the refrigerator, cooled by air, is kept at 293K, and the input power of the motor is 30.5W, the minimum temperature of the refrigerator is 70.5K and the cooling power is 185mW at 80K and 280mW at 85K. If the hot end is cooled to 281K by water, the minimum temperature can be 61K and the cooling power is 350mW at 80K. Up to now, the life test of the cooler has been lasting for more than 1100 hours. In the experiment, the room temperature is kept at 300+/- 2K, the humidity is about 60%, and the minimum cold end temperature is generally within the range of 75.4+/- 0.5K, the total apparent cooler power consumption varied between 31.4W and 31.8W.

MSMP and BAMM were commissioned by the Air Force Space Division (AFSD) in the late seventies to generate data in support of the Advanced Warning System (AWS), a development activity to replace the space-based surveillance satellites of the Defense Support Program (DSP). These programs were carried out by the Air Force Geophysics Laboratory with planning and mentoring by Irving Spiro of The Aerospace Corporation, acting on behalf of the program managers, 1st Lt. Todd Frantz, 1st Lt. Gordon Frantom, and 1st Lt. Ken Hasegawa of the technology program office at AFSD. The motivation of MSMP was the need for characterizing the exhaust plumes of the thrusters aboard post-boost vehicles, a primary target for the infrared sensors of the proposed AWS system. To that end, the experiments consisted of a series of Aries rocket launches from White Sands Missile Range in which dual payloads were carried aloft and separately deployed at altitudes above 100 km. One module contained an ensemble of sensors spanning the spectrum from the vacuum ultraviolet to the long wave infrared, all slaved to an rf tracker locked onto a beacon on the target module. The target was a small pressure-fed liquid-propellant rocket engine, a modified Atlas vernier, programmed for a series of maneuvers in the vicinity of the instrument module. As part of this program, diagnostic measurements of the target engine exhaust were made at Rocketdyne, and shock tube experiments on excitation processes were carried out by staff members of Calspan.

We describe a model for cooled thermal imaging sensors, based on silicon Schottky diode bolometer arrays. The sensing mechanism is the modulation of Schottky diode dark current with temperature. The proposed array is identical to Schottky diode arrays, which would be used for uncooled thermal imaging, except for a change of the sensing electrode metal. We separate the thermal and electrical response of the detector elements and discuss sensor limitations related to detector thermal isolation. At a 180 K operating temperature, we project NEDT's in the 3 to 20 mK range, depending upon system f/number. A 20 cm aperture sensor based on this technology should have a noise equivalent power below 10^-11 watts.

This paper summarizes the evolution of the field of space- based remote sensing of the Earth's environment (the atmosphere, oceans, and land surface) over the period from 1980-2000. It describes how we have reached the cusp of fundamental change in 2000, and it projects trends over the next decade. The scope of this paper is international. The work that forms the basis of this paper covers systems from Argentina to Ukraine. The field is evolving away from standalone governmental systems of high complexity and expense toward increasing use of small satellites, an increasingly commercial component, increasing spectral and spatial resolution, an increasing mix of lower-cost systems, and rapid international proliferation. As of three years ago, eight countries had built and flown free-flying Earth remote sensing satellite systems, and 11 countries were owners. Projections are for 25 countries to own (but not necessarily be able to build) such systems by three years from now. Following an inauspicious start to the field of high-resolution commercial remote sensing, the first commercial one-meter system is now operating, with many more slated to follow. History, status, trends, and over 25 potential commercial applications of remote sensing will be summarized.

Several remote sensing/infrared space surveillance programs in the midst of assembly, integration and test have recently experienced delays when water vapor was deposited as ice on cold surfaces in a sensor under test or calibration. When these surfaces were at critical locations, the sensitivity or response of the sensor decreased significantly because the ice absorbed the incoming signal. The source of water vapor could be from a chamber leak or outgassing from the sensor system or the vacuum chamber itself. In order to quantify the effects of ice deposits on signals in various spectral bands, published optical constants for amorphous and crystalline water ice have been used to calculate the transmission of water ice films as a function of wavelength from 1 to 20 microns. The results are presented in two ways: spectra of the physical thickness of a layer of ice whose absorption optical depth is unity, and transmission spectra for several characteristic layer thicknesses. These tools can be used in estimating the amount of ice - and by inference water vapor - present in the system. Related calculations can also be used to assess the probability that a given hardware setup or resulting data set is showing signs of degradation of response due to ice absorption, and the implications for those trying to interpret the results.

This paper presents an insight into advances in uncooled IR sensor technology. The paper does not speculate on long term futuristic concepts, but addresses what it should be possible to achieve during the next decade. Furthermore, the subject matter is mainly concerned with resistance microbolometer and associated sensor technology. Commercial sensitivity precludes detailed description of new initiatives in this field; however it is possible to outline key avenues of development. If the full potential of uncooled IR technology is to be realized, novel production methods will need to be introduced, particularly for the high volume consumer market. This will involve new detector concepts, focal plane array fabrication technology, readout and signal processing techniques, optical design, and packaging methods. This paper will discuss many of these issues highlighting detector design, performance and fabrication.

This paper reviews the use of thin film ferroelectric materials for application in microbolometer infrared detector arrays. A key issue is the need for high temperature processing to achieve the required ferroelectric crystal phase. Results of thermal trials on silicon readout circuits are presented which indicate failure due to disruption of the AlCuSi metallisation. Higher temperatures can be used if oxygen is excluded. A low temperature lead zirconate titanate (PZT) sol-gel deposition is reported which has been used to fabricate fully integrated detector arrays directly on readout silicon wafers. Higher performance is obtained from dielectric bolometer materials, and materials merit figures nearly 4 times that of PZT are reported for sputtered lead scandium tantalate (PST) films. These require post-deposition annealing to temperatures above that allowable for silicon readout survival. Results on excimer laser annealing are presented which demonstrate crystallisation of a ferroelectric film without heating the underlying substrate. A new composite thermal detector array design is introduced, based on an indirect fabrication method. This uses a high density interconnect wafer as a high temperature substrate for ferroelectric film growth. After fabrication of the detector pixels, individual arrays are flip-chip bonded to readout silicon die.

We have been developing a total monolithic microbolometer technology for uncooled thermal sensing along the route from fabricating pixels of thin-film ferroelectric bolometers on micromachined Si substrates. Toward achieving this objective, sensor material of (Ba_0.75Sr_0.25)TiO₃ (BST) has been prepared into thin-film form and been investigated to obtain a large temperature coefficient of dielectric constant (TCD) within the ambient temperature region. Operated in our proposed dynamic pulse-biased mode, the infrared responsivity (R_v) of sensor pixels is analyzed to reflect how those materials properties of BST film dominate the ultimate array performances. This new ferroelectric bolometer is expected to provide value-added merits of chopperless operation and high sensitivity enhanced by pulsed bias. In this paper, pixels of C-C balanced BST thin-film microbolometers have been fabricated by integrating Si-bulk micromachining and ferroelectric thin-film processing. Both pulsed laser deposition (PLD) and metal organic decomposition (MOD) methods have been employed in preparing BST films on those micromachined silicon substrates. Both the films show similar insufficient bolometric behavior with TCD-values smaller than 1%/K. Under pulsed bias, chopperless operation of pixels of so- fabricated microbolometers was confirmed. PLD enabled low- temperature preparation of high-quality films at 520 degree(s)C, so renders it for cutting-edge investigations to attain the TCD-value that demonstrated in BST ceramic plate by preparing large-grained, stress-free, micrometers -thick films. Meanwhile, MOD provides us those advantages of low-cost, large-area deposition and good uniformity compared to PLD method, films with TCD-value about -0.3%/K have been developed by MOD and are being geared to fabricate arrays. Finally, the future direction towards prototyping ferroelectric arrays was formulated based on the practical view of our development expeditions.

We reported a 320 x 240 uncooled IRFPA with 40 micrometers pitch having diode detectors fabricated on an SOI wafer. Since the fabrication process of the SOI diode detector is compatible with the silicon IC process, only a silicon IC fab is necessary for manufacture of the FPAs. This enables mass production of low cost uncooled FPAs. This paper focuses on the performance of the FPA. In the previous paper, we proposed a novel infrared absorbing structure which offers a very high fill factor. Although this structure exhibited a high infrared absorption because of interference absorbing components incorporated in the structure, large thermal capacitance was an issue. Thus we have improved the infrared absorbing structure in the newly developed FPA. The improved absorbing structure has been devised making use of reflection of metal interconnections including diode metal straps. A thermal time constant of 17 msec has been achieved without degrading the responsivity compared with the conventional absorbing structure.

A low-noise architecture for uncooled microbolometer focal plane arrays is described. The on-chip readout circuit contains an integration circuit in which the bolometer current is directly injected into a capacitor, and exhibits extremely low noise with no decrease in signal. The simple configuration of the integration circuit makes it possible to operate more circuits in parallel, and increases the integration time and number of pixels. The bias circuit for the integration circuit is formed on the chip to reduce the effect of changes in the substrate temperature. The equivalent input noise, in which all readout noise is converted into that at the bolometer node, was 6.2(mu) V rms. A noise at this level is so low that can loosen the required TCR in the bolometer material. A 37-micrometers -pitch 320 x 240 ROIC was fabricated, and its expected NETD was 67-34 mK at a TCR of 1-2%/K. This architecture makes it possible to produce low-cost miniature cameras.

The performance of uncooled In_xGa_1-xAs photovoltaic devices operating in the 2-3.6 micrometers spectral range has been studied both theoretically and experimentally. Various multilayer homo- and heterojunction devices have been considered. Band-to-band Auger processes were taken into account as the dominant mechanisms of thermal generation and recombination. Calculations show that the best performance can be obtained in devices with lightly doped n-type absorber region as a result of the significant role of Auger S (spin-off band) process. The optimized heterostructures with near intrinsic n-type narrow gap InGaAs absorber were grown using molecular beam epitaxy. The performance of the present InGaAs devices remains significantly below theoretical limits. Better agreement can be observed for devices with longer cutoff wavelength as the result of increasing role of fundamental limitations and improved quality of materials with x approximately equal to 1. Improvement of performance by almost an order of magnitude has been achieved by the use of monolithic optical immersion. This has been accomplished by growth of the InGaAs heterostructures on thick SI GaAs substrates and by formation of the immersion lenses directly in the substrate. These devices are expected to find important applications in infrared systems which require better performance than existing uncooled detectors.

This paper presents an overview of the development in Australia of resistance bolometer technology and associated uncooled infrared sensors. A summary is given of research achievements, with the aim of placing in historic perspective Australian work in comparison with overseas research and development. Extensive research in this field was carried out at the Defence Science and Technology Organisation (DSTO), Salisbury, South Australia, in collaboration with the Australian microelectronic and electro-optic industries, with supporting research in Australian universities. The DSTO research has a history covering five decades, commencing with simple thin film bolometers employed in radiometric sensors, followed by protracted R&D culminating in development of micromachined focal plane detector arrays for non-imaging sensors and lightweight thermal imagers. DSTO currently maintains a microbolometer processing capability for the purposes of research collaboration and support for commercial initiatives based on patented technology. Expertise in microbolometer design, performance and processing technology has transferred to Electro-optic Sensor Design (EOSD) through a licensing agreement. Contemporary development will be described.

Third generation focal plane arrays are being actively developed for the U.S. Army and other branches of the Department of Defense. The objective is to ensure that future soldiers will have superior night-fighting equipment. The requirements defined by this objective and the technology under development to support a demonstration of this capability is described. Issues associated with the development and exploitation of the high-performance cooled component of a family of third generation imager systems are discussed. Also discussed are two classes of uncooled imagers; one having high resolution and medium-high performance, and the second being very low cost.

Raytheon's Infrared Operations (RIO) has invented and developed a new class of focal plane arrays; the Adaptive IR Sensor (AIRS) and Thinfilm Analog Image Processor (TAIP). The AIRS FPA is based upon biologically inspired on-focal- plane circuitry, which adaptively removes detector and optic temperature drift and l/f induced fixed pattern noise. This third-generation multimode IRFPA, also called a Smart FPA, is a 256x256-array format capable of operation in four modes: 1) Direct Injection (DI), 2) Adaptive Non-uniformity Correction (NUC), 3) Motion/Edge Detection, and 4) Subframe Averaging. Also the 320x240 TAIP results have shown excellent image processing in the form of Spatial and Temporal processing.

Continuing advances in CMOS technology including finer lithography, the addition of dense planarized interconnect layers, concomitant improvements in transistor performance, and the availability of design tools that facilitate large- scale circuit integration, are now enabling the development of systems on a chip. While the first such imaging systems- on-a-chip supported detection of radiation at visible wavelengths, recent imaging systems-on-a-chip extend into the infrared. The result is high-performance infrared FPAs with high functionality. We report our progress at Rockwell Science Center in exploiting submicron CMOS to produce such infrared imaging systems-on-a-chip while overcoming accompanying challenges such as lower operating voltage. Our goal is to develop third-generation infrared imagers with compelling performance and functionality advantages that not only provide high sensitivity and resolution, but also facilitate on-demand sensor selection to adeptly match each mission without need for extensive support logistics including extensive cooling and elaborate camera electronics.

The most sophisticated infrared detector technology is based on multicolor devices. Both two-color HgCdTe photodiodes as well as quantum well GaAs/AlGaAs photodetectors have been presented. More attention is devoted to HgCdTe detectors based upon an n-P-N (the capital letters mean the materials with larger bandgap energy) HgCdTe triple layer heterojunction design. Both sequential mode and simultaneous mode detectors are fabricated. Because of the complicated and expensive fabrication process, numerical simulation has become a critical tool for the development of HgCdTe bandgap engineering devices. In the paper the performance of middle wavelength/long wavelength (MW/LW) dual-band HgCdTe photovoltaic detectors are examined theoretically. It is assumed that the performance of photodiodes is due to thermal generation governed by the Auger mechanism. An original iteration scheme was used to solve the system of nonlinear continuity equations and the Poisson equation. The effect of composition and doping profiles on the complex heterojunction detector parameters are presented. All quantities are presented as function of electric potential and Fermi quasi-levels. The results of calculations are presented as the maps showing spatial distribution of electrical potential, photoelectrical gain, sensitivity, and density of noise generation. The theoretical predictions of heterojunction device parameters are compared with available experimental data.

Infrared sensors have advanced in performance and reduced in price to new and unsurpassed levels. Significant advancements in uncooled technology have recently enabled the notion of an expendable infrared sensor. Further performance and producibility improvements are still required such as the elimination of the thermal electric cooler and shutter, as well as high levels of signal processing integration. Additionally, the economy of scale associated with very large volumes will be realized as specific, enabling price points are achieved. Specific cost objectives and enabling technology requirements are discussed.

For the first time, diffractive rectangle-based multilevel steps Si microlens arrays are fabricated by a new method, named part etching. The new method proposed can increase focal length of diffractive microlenses arrays. The 256x256 element microlens arrays are designed for a center wavelength of 4micrometers , with 40micrometers (Horizontal) x 30micrometers (Vertical) quadrate pixel dimension and a speed (F number) of F/2.53 (in air). The focal length of the microlens array is 400micrometers in Si material, much longer than focal length of the microlens arrays of the same size fabricated by conventional binary optics method. The method also includes photolithography and ion beam milling process. The 256x256 element microlens arrays and the same 256x256 element PtSi IR Focal Plan Arrays (FPAs) are monolithic integrated on the same wafer. The IR response characteristics of the integration device are improved greatly.

Version 2 of the thermal range model TRM3 has recently been released. TRM3 allows performance modeling of advanced undersampled thermal imagers. The features of the model that uses MTDP (Minimum Temperature Difference Perceived) rather than MRTD are reviewed. Amendments and changes introduced in Version 2 are discussed.

The High-Definition InfraRed (HDIR) thermal-imaging system is a thermal camera with highest geometrical resolution producing a video signal according to the HDTV (High- Definition TeleVision) standard. The thermal-imaging system is a parallel-scanning device with two fold interlace. Its detector is sensitive within the 7-11 micrometers spectral region and features 576 x n elements (n being the number of TDI stages). It has been carefully optimized in terms of range performance and size of optical entrance pupil as well as feasibility of production and yield. The 16:9 aspect ratio of the HDTV standard together with the high number of 1920 pixels/line and 1152 lines propose a drastic increase in range performance. In fact, model calculations predict an increase of up to 60% for identification range as compared to present-standard TV-compatible thermal imagers with the same vertical field of view. With the HDIR having been integrated into a German main battle tank Leopard 2, trials were undertaken in comparison with other equipment like the OPHELIOS and the Common Module WBG-X.

The staring array is the basis of many modern thermal imaging systems, cooled and uncooled. A major drawback in all staring array thermal imaging systems is the need to provide thermal referencing in order that the non-uniformity inherent in all IR detector technologies can be corrected. A common approach is to use a mechanical shutter operated intermittently, typical of uncooled resistance bolometers and cooled photon detectors, or a rotating chopper, typical of ferroelectric uncooled bolometers. Although these methods are inexpensive and consume little power, they are inappropriate to environments where high g-forces or shock loads are encountered. This paper describes a solid state modulator operating on the 8-12micrometers band. The modulation mechanism is induced absorption in high-purity intrinsic germanium. Electron-hole pairs are created in the germanium modulator; the electrons are weak absorbers but the holes absorb strongly by means of the light-hole/heavy-hole inter-sub-band transition. The transmission of the modulator can thus be varied by varying the hole concentration, for example by illuminating the modulator with near IR light. Very good modulation depth (5% to 90% transmission) has been measured, at optical power densities of approximately 10 W/cm². Switching speeds are controlled by the carrier lifetime, and are a few milliseconds in our prototype device. The high power requirement rules out this approach for hand-held applications. However for intermittent use, or where the environmental constraints are dominant, this technology offers a potentially robust 8-12micrometers modulator.

The use of Unmanned Airborne Vehicles (UAVs) for different applications in surveillance and reconnaissance requires customized imaging systems fitting in size and weight into the UAVs and providing the adequate electro-optical performance in terms of field of view (FOV), field of regard (FOR) and geometrical resolution resulting in the achievable mission performance. ATTICA P256D is a very compact, extremely lightweight digital thermal camera operating in the 3-5micrometers waveband featuring an uncompromising design for low weight. Image generation is performed by a platinum-silicide (PtSi) focal plane array (FPA) detector with 256 x 256 elements, developed and produced by AIM with an integrated minicooler. Total weight of the whole IR camera is 1.7 kg. The thermal camera OPHELIOS in BREVEL configuration contains a wide-range zoom objective with a magnification change factor of 8 for large field of regard and high identification performance. The thermal imager is integrated into an internal structure which itself is mounted into a frame in a way that allows rotation of the whole camera by n x 360 degree(s) for compensation of both roll movement of the UAV and image derotation. This configuration offers the best volume/performance ratio available in this performance class.

The real-time acquiring and processing technology of three- dimension (3D) geosciences information is an important field of modern remote sensing. The Airborne Scanning Laser Ranging-Imager Sensor (ASLRIS) is a new generation of remote sensing and mapping system for providing 3D geosciences information. The system integrates the laser altimeter, IR imager, Differential Global Positioning System (DGPS) and Inertial Reference System (INS), by which Digital Elevation Model (DEM) and Georeferenced Image (GI) can be generated quickly and effectively without ground control point. The scanning laser rangefinder and the passive infrared scanning imager share the telescope and the scanning mirror. A suitable optical scanning mode is important to satisfy the demand of high-speed scanning and high-resolution laser ground sampling with limited repetitive rate of laser. The optical scanning of conical mode is studied emphatically comparing to the linear optical scanning mode in this paper, which two have been applied to the ASLRIS. The configuration, fundamental, specification and character of conical scanning technology are analyzed respectively. The principles to harmonize the conditions among scanning rate, optical aperture, scanning efficiency, platform flight height and repetitive rate of laser are specially studied. Finally the field test results of the ASLRIS are given.

For multiband sensor applications we propose an optical system that forms different spectral images with a constant magnification and distortion over all spectral bands. Spectral filter devices are introduced for three major purposes; for determining spectral range of the bands, for correcting chromatic aberrations, and for a constant magnification and distortion. The spectral filter device has an interference band pass filter on one plane surface and a refractive-diffractive hybrid element on the other surface. The diffractive element is designed to compensate chromatic aberration in each spectral band and the aspheric refractive element has a function of setting focal length of each band to a constant value. We have designed and fabricated an optical system for two bands. The diffraction orders of the diffractive element are designed to optimize the diffraction efficiencies. Experimental results show that the difference in magnification between two bands is smaller than one pixel over full field of view. Measured MTF and images indicate that aberrations including chromatic aberration of the optical system are well compensated.

Results of detector characterization are presented for quantum well infrared photodetectors (QWIPs) fabricated from a variety of III-V material systems lattice-matched to InP substrate. Extremely large responsivities of 33.2 A/W were obtained from GaInAs/InP QWIPs operating at (lambda) equals 9 micrometers which represents to the authors' knowledge the largest value of responsivity for any QWIP in this wavelength range. Devices made from AlGaInAs/InP and GaInAs/AlInAs have also been realized that extend the wavelength range of sensitivity from 3 micrometers out to 20 micrometers while remaining lattice-matched to InP. Lattice-matched multispectral detectors are demonstrated for sensitivity at both 4 micrometers and 8.5 micrometers . Localized epitaxy of GaInAs/InP superlattice structures lattice-matched to InP was performed on Si substrate for the purpose of monolithic integration of III-V QWIPs with Si-based readout integrated circuitry.

The intermixing techniques have been used to modify the behavior of the quantum well infrared photodetector (QWIP). It is demonstrated that the proton implantation assistant intermixing process is very effective to the modification of the quantum well potential. Both the inter-band transition and inter-sub-band transitions are used to study the intermixing effects. After the characterization on the modified detector, the dominant mechanisms in the QWIP are examined.

We report on novel low-noise QWIP focal plane arrays (FPAs) which allow us to improve the thermal resolution of infrared sensors in the long-wavelength infrared (LWIR) atmospheric window. Our concept uses detector structures with a small photoconductive gain in order to achieve simultaneously a high internal quantum efficiency and a small responsivity. In comparison to conventional QWIPs where each period consists of a quantum well and a thermionic barrier, our approach involves additionally a combination of a narrow quantum well and a tunnel barrier. Due to these additional layers, a high emission probability of the photoexcited carriers and an efficient capture into the ground subband of the subsequent period are simultaneously achieved. FPA cameras using these detectors show an extremely low noise- equivalent temperature difference (NE(Delta) T) and a high dynamic range. In particular, NE(Delta) Ts of only 7.2 mK and 5.2 mK (at 20 ms and 40 ms integration time, respectively) are observed for a 256x256 FPA camera system which we have realized using low-noise QWIPs. This value is the best temperature resolution ever obtained for thermal imagers operating in the LWIR.

This paper reviews recent advances in pulse tube cryocoolers and their application for cooling infrared sensors. There are many advantages of pulse tube cryocoolers over Stirling cryocoolers associated with the absence of moving parts in the cold head. Efficiencies have been improved considerably in the last few years to where they equal or even exceed the efficiencies of Stirling cryocoolers. The use of inertance effects and double inlets to improve the efficiencies will be discussed. Pulse tube cryocoolers are now being used or considered for use in cooling infrared detectors for many space applications. One disadvantage of pulse tube coolers is the difficulty in scaling them down to sizes as small as 0.15 W at 80K while maintaining high efficiency. A second disadvantage is the larger diameter cold finger required for the same refrigeration power because of the presence of the pulse tube. These two disadvantages have limited their use so far in cooling infrared sensors for many military tactical applications. Progress in overcoming these disadvantages is discussed.

Performance and reliability parameters of the AIM Stirling coolers have been presented in several previous publications. This paper focuses on recent developments at AIM for the COP improvement of cryocoolers in IR-detectors and systems applications. Improved COP of cryocoolers is a key for optimized form factors, weight and reliability. In addition, some systems are critical for minimum input power and consequently minimum electromagnetic interference or magnetic stray fields, heat sinking or minimum stress under high g-level, etc. Although performance parameters and loss mechanism are well understood and can be calculated precisely, several losses still had been excessive and needed to be minimized. The AIM program is based on the SADA I cryocooler, which now is optimized to carry 4.3 W net heat load at 77K. As this program will lead into applications on a space platform, in a next step AIM is introducing flexure bearings and in a final step, an advanced pulse tube cold head will be implemented. The performance of the SADA II cooler is also improved by using the same tools and methods than used for the performance increase of the SADA I cooler by a factor of two. The main features are summarized together with measured or calculated performance data.

Since 1997, Signaal Usfa has been working on the development of high reliability cryocoolers. These coolers have been developed with the aim to eliminate the lifetime determining factors of conventional cryogenic tactical coolers. The intention of this study was the development of a family of cryocoolers, which could be used to cover a large range of cooling powers. Today, these developments have resulted in the new range of flexure bearing cryocoolers currently available at Signaal Usfa, with cooling performances between 0.5 and 3 W at 80K and estimated lifetimes of more than 20,000 hours MTTF.

Pulse tube coolers operate without any moving solid parts inside the cold finger. This feature promises higher reliability, lower vibrations, and lower production cost, when compared to conventional Stirling coolers. We have designed and constructed a miniature-size pulse tube cooler for potential future replacement of Stirling coolers. To allow for easy access to the cold platform, a U-shaped configuration of pulse tube (diameter 4.5 mm, length 60 mm) and regenerator has been chosen. The pressure oscillation of the helium working fluid in the system is generated by means of a commercial linear compressor (AIM, model SL100) operated at a frequency of 50 Hz. A combination of capillary and buffer volume and a second-inlet capillary, which are connected to the warm end of the pulse tube, serve to adjust the phase shift between pressure and mass flow oscillation in the cooler. A maximum cooling power of about 0.3 W at 80 K and a slope of the load line of 40 mW/K have been achieved so far at a compressor input power of 90 W and a heat rejection temperature of about 330 K. The overall COP of 0.3% at 80 K is still appreciably lower than that of comparable Stirling coolers, which is related to enhanced regenerator losses and DC gas-flow in the pulse tube cold head. The experimental data are compared to a linear network model for the pulse tube cold head.

Flexure spring suspensions have demonstrated the ability to provide long operating lifetimes for cryocoolers intended for space-based applications. Insertion of this technology into coolers intended for tactical or commercial application has been slow due to cost considerations. This paper describes the development and testing of a flexure spring system for small tactical cryocoolers that provides a doubling of operating life while costing approximately the same as the traditional helical coil spring suspension system. The flexure spring system described in this paper successfully achieves the high radial stiffness characteristic of the flexure spring design in a low-cost package. In addition, the concept has been implemented in cryocoolers weighing less than a pound and smaller than a soft drink can. This design has been qualified for use in U.S. Army applications. Qualification and life test data is presented to demonstrate the robustness of the design in tactical environments. The producibility of the design is evidenced by the on-going production of these coolers for various applications.

In this paper, an effort is made to utilize mixed-gases as refrigerant in the open cycle Joule-Thomson (J-T) cryocooler used for cooling infrared devices. The theoretical analysis of the thermodynamic performance of the mixed-refrigerant J- T cryocooler is made, including the refrigeration temperature, the cooling capacity, and the cool-down period. The principle of the component selection of the mixture is presented. A simple theoretical estimation model is developed to calculate the cool-down period of the J-T cryocooler. An experimental setup is also established to test the thermodynamic performance of a miniature open cycle J-T cryocooler. The refrigeration performances of the cryocooler using pure nitrogen and mixture are compared theoretically and experimentally. Both the theoretical and experimental results show that using appropriate gas mixture can improve the thermodynamic performance of the open cycle J-T cryocooler used for cooling infrared devices.

New generations of InfraRed (IR) detectors are mature and well within the production stage at Sofradir. The two generations consist of Time Delay and Integration (TDI) long linear arrays (for second generation systems) sensitive in the 8-12 micrometers waveband and large 2D staring arrays (for second or third generation systems) sensitive in the 3-5 micrometers and 8-12 micrometers wavebands. Outstanding progress has been made in product development and production assessment during these last 10 years at Sofradir and the key points for technologies and products are presented as well as lessons learned.

We present here recent developments obtained at LETI infrared laboratory in the field of infrared detectors made in HgCdTe material and using the molecular beam epitaxial growth technique (MBE). We discuss the metallurgical points (growth temperature and flux control) that lead to achieve excellent quality epitaxial layers grown by MBE. We show a run-to-run reproducibility measured on growth run of more than 15 layers. The crystalline quality, surface morphology, and composition uniformity are excellent. The etch pits density (EPD) are in the low 10⁵.cm^-2 when HgCdTe grows on a CdZnTe substrate. Transport properties reveal a low n-type carrier concentration in the 10¹⁴ to 10¹⁵.cm^-3 range with a carrier mobility in excess of 10⁵ cm²/V/sec at 77K for epilayers grown with 10 micrometers cutoff wavelength. We describe the performances of several kinds of our HgCdTe- MBE devices: single color MWIR and LWIR detectors on HgCdTe/CdZnTe operating at 77K in respectively (3-5 micrometers ) and (8-12 micrometers ) wavelength range; single color MWIR detectors on HgCdTe grown on germanium heterosubstrate operating at 77K in the (3-5 micrometers ) wavelength range; two color HgCdTe detectors operating within the MWIR (3-5 micrometers ) band.

High resolution infrared imaging system calls for very long scanning arrays with several thousands of detectors and high performance. This paper presents the technological developments and the electro-optical performance obtained at LETI/SLIR (Infrared Laboratory) on linear HgCdTe (MCT) arrays working in the 3-5, 8-10 and 11-12.5 micrometers spectral ranges. These large arrays have an indirect hybrid architecture composed of butted HgCdTe PV detection circuits and Si readouts hybridized on a mechanically close-matched fanout substrate. Defect free dicing and butting, respecting the detector pitch, is made by accurate and nondamaging techniques.

Standard GaAs/AlGaAs QWIPs are now well established for LWIR detection. The main advantage of this technology is the duality with the technology of commercial GaAs devices. The second advantage widely claimed for QWIPs is the so-called band-gap engineering, allowing the custom design of the quantum structure to fulfill the requirements of specific applications such as multispectral detection. QWIPS are close to being optimized. The understanding of detection mechanisms has led to high performance QWIPs working at high temperature (above 77 K). However, as with all quantum detectors, the operating temperature of QWIPs is limited by the thermal current. A new skimmed architecture accommodating this offset has already been demonstrated. The optimization of a skimmed structure requires the modeling procedures and the process, to be adapted. We present the current status of QWIPs in France, including the latest performances achieved with both standard and skimmed architectures. We illustrate the development of our QWIPs by recent results on FPAs.

LETI LIR has been involved in amorphous silicon uncooled microbolometer development for a few years. This silicon IR detection is now well mastered and matured so that industrial transfer LETI/LIR technology is performed towards Sofradir. Industrial production of 320x240 microbolometer array with 45 micrometers pitch is now started. After a short description of the technology and the readout circuit architecture we focus on device reliability which is the key point for microbolometer application. Methodology for reliability enhancement is described. First results obtained on amorphous silicon reliability are presented. Electro-optical results obtained from an IRCMOS 320x240 with 45 micrometers pitch are presented. NEDT close to 70 mK can be obtained with our standard microbolometer amorphous silicon technology.

Sofradir has developed second and third generation InfraRed (IR) detectors sensitive in different wavebands covering the 1 to 16 micrometers spectral range. The main material used for cooled IR detector is HgCdTe and Sofradir extends its product range using QWIP for 8-9 micrometers large staring arrays and microbolometers based on amorphous silicon (Si:(alpha) ) thermometer material for uncooled technology. Array characteristics and performances are presented (including new results) and the maturity of technologies and products are discussed for present as well as for short term production activities.

This paper highlights two main achievements which were performed by AIR LIQUIDE during the last decade in the field of low cost Joule-Thomson coolers. On one hand, in order to comply with new geometrical requirements, AIR LIQUIDE is able to propose a flat cooler. This compact geometry is enabled by a new, cheap, type of heat exchanger. It offers a better resistance to external vibrations. On the other hand AIR LIQUIDE has developed, in the frame of a commercial program, a complete cryogenic cooling system, composed of a dual flow Joule-Thomson cooler, a pressurized gas capacity equipped with a manifold block and a pyrotechnic actuator, and the requested pipes and connectors. The dual flow is enabled by flexion of a washer made of shape memory alloy.

This paper enters in the scope of the session on 10-year update of IR in France. Cryotechnologies is a leader in both the French and European markets as a designer and manufacturer of cryogenic coolers. Serial production of the first generation of Stirling cryocoolers started at Cryotechnologies in the late eighties. A range of integral Stirling coolers is nowadays available and completes the existing range of split Stirling cryocoolers. Technical improvements are keeping up with the market evolutions and new potential applications (costs reduction, fast cooldown time, increase of cooling power, very high reliability, pulse tube cold finger).

During the last 30 years, the Space Research Department (DESPA) of Paris Observatory has developed infrared instrumentation for space and ground-based telescopes. First, we present the PbS linear detector of the ISM IR imaging spectrometer of the Phobos mission. Then the CID InSb focal plane of ISOCAM-SW is described. The studies of this CID InSb focal plane allowed us to develop an IR camera for the first astronomical observations using adaptive optics. We also describe the linear array built for the OMEGA imaging spectrometer of the Mars 96 mission. The last chapter is dedicated to the IR spectrometer of the Huygens probe. To conclude, the needs and challenges in the area of mid-band infrared astronomy are discussed.

The recent development of high performance uncooled infrared microbolometer arrays with detection limit (Noise Equivalent Temperature Difference) as low as 50 mK (f/1-60 Hz) offers a new challenge for the design of space instruments for Earth remote sensing. In this paper, we present results obtained on a 256x64 amorphous Silicon microbolometers array and on a 320x240 Vanadium Oxide (VOx) microbolometers array, from electro-optical characterizations performed at Centre National d'Etudes Spatiales. The goal of these measurements is to derive the performances of these arrays in order to study the feasibility of Earth remote sensing instruments using uncooled infrared microbolometer arrays. We find that a detection limit of approximately 0.16 K could be achieved at low spatial resolution, where the VOx microbolometer array is more adapted, due to relatively large time constant (approximately 23 ms). At medium spatial resolution, a detection limit of approximately 0.5 K could be achieved, with the amorphous Silicon microbolometer array.

We describe a mid-IR photovoltaic detector using InAsSb as active material, grown by MBE on a GaSb substrate. The purpose of this study is to show that quantum detectors can offer an alternative to thermal detectors (pyroelectric or resistive bolometers) for high temperature (near room temperature) operation. With a 9% Sb content, InAsSb is lattice matched to GaSb and thus provides an excellent material quality, with Shockley-Read lifetimes of the order of 200 ns as measured by photoconductive gain measurements as well as time resolved photoconductivity experiments. The band gap of InAsSb corresponds to a wavelength of 5 microns at room temperature. This makes InAsSb an ideal candidate for room temperature detection in the 3-5 microns atmospheric window. Photovoltaic structures are characterized by current voltage characteristics as a function of temperature. Using the absorption value obtained on the test samples, a detectivity of 7X10⁹ Jones at 3.5 micrometers is estimated at a temperature of 250 K, which can easily be reached with Peltier cooling. Considering the photovoltaic spectrum, this leads to a NETD lower than 80 mK.

ALCATEL has recently studied an infrared imaging chain, in the frame of phase A studies for the Land Surface Processes and Interactions Mission (LSPIM), which was one of the four candidate Core Missions for the European Space Agency Earth Explorer Program. The LSPIM satellite carries a single optical payload named PRISM (Processes Research by an Imaging Space Mission). PRISM is a multispectral imager based on the push broom imaging principle, operating at approximately 679 km altitude with a NADIR swath of 50 km associated to a 50 m spatial resolution. The paper presented herewith summarizes the results of the IR imaging chains study: composed of two IR focal planes (SWIR and TIR) integrated in dedicated ALCATEL dewars (one for each FPA), two proximity electronic modules and a common analog processing unit delivering digital video data to the one board mass memory unit (MMU). The main specifications of the detectors and electronic units are presented, a baseline of the imaging chain architecture complying with the requirements is then proposed with the main achieved trades off. The concept and associated performances of cutting-edge cooling systems are also introduced in this paper.

This paper presents a brief overview of military infrared sensors development and delivery in France in the 1995-2005 period. We first enumerate a number of weapons systems already in service or to be delivered before 2005. This part will show the increasing number of military equipment using infrared focal plane arrays. Then we present some examples of research initiatives sponsored by the French Ministry of Defense. By the end we mention the main research directions for the years to come.

After thirty years of production of thermal imagers of the first and second generation, all designed on the same basic architecture, the evolution of the detectors technology to starring array has given birth to the ultimate generation of thermal imagers with no scanning mechanism. In the 3-5 micrometers and 8-12 micrometers wavebands, the performances and the size of starring array are adequate to design a new generation of products which will allow the use of FLIR almost everywhere in the forces. Smaller, lighter, cost effective, for better performance are the main characteristics of the third generation FLIR. The interest of starring array in IR has been known since a long time. But for the last twenty years, IR starring arrays (difficult to produce) were used for very specific applications and costly programs. The evolution of silicon technology leads the technology of IR detectors towards producibility, low cost, availability, in parallel the tremendous increase of computation power of DSP will allow the implementation of software to obtain a good image.

This paper presents the design of HGH Systemes Infrarouges newest infrared search and track (IRST) sensor. The system incorporates a number of advanced features to achieve compact size and long detection range while maintaining a low price in comparison with previous IRST shipborne systems developed. The sensor houses a high sensitivity long wave infrared (LWIR) CMOS photovoltaic HgCdTe 288 x 4 element focal plane array coupled to a high reliability and long lifetime Stirling cycle cooler. Some of the system key features include: athermalized and gyro-stabilized f/l optics, built-in nonuniformity correction assembly, 12-bit real time digital data output and RS-422 interface for remote control capability.

AEROSPATIALE MATRA MISSILES has been involved in sensors, scenes and systems simulation for more than 10 years. These simulations are mainly used for missile guidance or target detection and tracking. They have been improved continuously and have become more and more realistic. They are now essential tools for the development and qualification of complex systems. This paper presents the evolutions of simulations through different examples (air-to-ground missile with IR terminal guidance and optronic firing post).

After a description of the flip-chip technique developed at LETI, we present its main advantages and its evolution. Using this basic method, a mass production procedure has been developed in order to decrease the cost of the technological step. With this new method, we are able to simultaneously hybridize several linear or two dimensional arrays directly onto readout circuits on 150 mm silicon wafer. The electrical accessibility to the components provided by the method enables more detailed electrical tests to be carried out with an automatic prober before manual integration in cryogenic conditions which is done only for good electrical devices. We have also developed a high reliability method in order to hybridize very large IRFPA. With this improved technique, 2D arrays can undergo several thousand 300 K - 77 K cycles without degradation.

Infrared imaging is at a transition where the market, product development and even research and development are driven by cost and applications rather than increased performance. The technology and industry are maturing and transitioning from a purely military and scientific to a predominant commercial thrust. Recent trends in infrared imaging are compared to academic technology development theories and similar past trends in other industries to draw conclusions regarding the level of technological maturization. The relationship of infrared technology to technology life cycles is discussed.

MEDUSA is a sensor network, consisting of and effectively combining a variety of different remote sensing instruments. Installed in 1998 it is operationally used in a maritime surveillance aircraft maintained by the German Ministry of Transport, Building and Housing. On one hand routine oil pollution monitoring with remote sensing equipment like Side Looking Airborne Radar (SLAR), Infrared/Ultraviolet Line Scanner (IR/UV line scanner), Microwave Radiometer (MWR), Imaging Airborne Laserfluorosensor (IALFS) and Forward Looking Infrared (FLIR) requires a complex network and communication structure to be operated by a single operator. On the other hand the operation of such a variety of sensors on board of one aircraft provides an excellent opportunity to establish new concepts of integrated sensor fusion and data evaluation. In this work a general survey of the German surveillance aircraft instrumentation is given and major features of the sensor package as well as advantages of the design and architecture are presented. Results from routine operation over North and Baltic Sea are shown to illustrate the successful application of MEDUSA in maritime patrol of oil slicks and polluters. Recently the combination of the different sensor results towards one multispectral information has met with increasing interest. Thus new application fields and parameter sets could be derived, like oceanography or river flood management. The basic concepts and first results in the fusion of sensoric information will conclude the paper.

Irvine Sensors Corporation (ISC) has pioneered the use of a chip stacking technology that allows an entire electronics system to be packaged into a single 3-dimensional cube of electronics. This stacking approach allows the elimination of traditional printed circuit boards (PCB) and as a result significantly reduces the size of the electronics. Recently this technology has been applied to electronic camera applications including both high-resolution digital still picture and video camera technologies. In addition this electronics implementation approach is under evaluation for application in the SWIR and LWIR/thermal imaging spectral bands.

Direct remote sensing of vehicle exhaust emissions under real-world driving conditions is desirable for a number of reasons, including: identifying high emitters, investigating the chemical composition of the exhaust, and probing fast reactions in the plume. A remote sensor, incorporating IR and UV spectrometers, was developed. The IR spectrometer consists of a grating system mounted on a synchronous motor, optically interfaced to a room temperature PbSe detector. UV-vis measurements are made with a CCD array spectrometer. Eight optical passes through the exhaust plume allow rapid and sensitive monitoring of the exhaust stream emitted by moving vehicles on a car-by-car basis. The combination of these two techniques resulted in unprecedented, direct measurement capability of over 25 pollutants in the exhaust plume. Emissions from a fleet of vehicles powered by a range of fuels (gasoline, diesel, natural gas, and methanol) were tested. The exhaust from hot gasoline- and methanol-powered cars contained high levels of NH₃, up to 1500 ppm. These emissions were up to 14 times higher than the corresponding NOx emissions. Unlike most previous work, NOx was measured as the sum of NO and NO₂; N₂O was also measured. Field testing at a southern California freeway on-ramp was conducted over a one week period, totaling >4,500 measurements. It was found that 66.4% of the emitted NH₃ was produced by 10% of the fleet, following the (gamma) - distribution that has been reported for criteria pollutants. Mean NH₃ emission rates were calculated at 138 mg km^-1, nearly twice as high was previous estimates.

MCT-detectors are the most sensitive detectors used for spectroscopic applications in the middle infrared (MIR) fingerprint region of spectra (5-15 micrometers ), but their exploitation requires Liquid Nitrogen (LN) cooling in specialized optical dewars and precise optical alignment systems. Polycrystalline Infrared (PIR) fibers from solid solutions of AgCl/AgBr are transparent in the spectral range of 4-18 micrometers and have been coupled with pigtailed MCT detectors. The combination of such more advanced MCT detectors with PIR-fibers' flexibility enables remote spectroscopy of chemical reaction processes in situ or biomedical diagnostics in vivo at distances up to 20 meters from Fourier Transform Infrared (FTIR), Tunable Diode Laser (TDL) or optical filter spectrometers. The main advantage of these multichannel MCT/PIR detectors for spectroscopy and multispectral sensing is that there is no need for costly and bulky optics and time consuming alignment procedures of the MCT detector and the dewar in relation to the IR sources used. In this study, PIR-fiber pigtailed 2 and 4 channel MCT-detectors are described for different spectroscopic applications where the fibers are assembled in a bundle for remote spectroscopy and for multispectral analysis of specific targets and characteristic wavelengths.

Despite major advances in cardiovascular science and technology during the past three decades, approximately half of all myocardial infarctions and sudden deaths occur unexpectedly. It is widely accepted that coronary atherosclerotic plaques and thrombotic complications resulting from their rupture or erosion are the underlying causes of this major health problem. The majority of these vulnerable plaques exhibit active inflammation, a large necrotic lipid core, a thin fibrous cap, and confer a stenosis of less than 70%. These lesions are not detectable by stress testing or coronary angiography. Our group is exploring the possibility of a functional classification based on physiological variables such as plaque temperature, pH, oxygen consumption, lactate production etc. We have shown that heat accurately locates the inflamed plaques. We also demonstrated human atherosclerotic plaques are heterogeneous with regard to pH and hot plaques and are more likely to be acidic. To develop a nonsurgical method for locating the inflamed plaques, we are developing both IR fiber optic imaging and NIR spectroscopic systems in our laboratory to detect hot and acidic plaque in atherosclerotic arterial walls. Our findings introduce the possibility of an isolated/combined IR and NIR fiber optic catheter that can bring new insight into functional assessment of atherosclerotic plaque and thereby detection of active and inflamed lesions responsible for heart attacks and strokes.

Reticle systems are considered to be the classical approach for estimating the position of a target in a considered field of view and are widely used in IR seekers. Due to the simplicity and low cost, since only a few detectors are used, reticle seekers are still in use and are subject of further research. However, the major disadvantage of the reticle trackers has been proven to be sensitivity on the IR countermeasures. To resolve this problem modification of optical trackers is analyzed here for a wide class of reticles that are producing frequency or amplitude modulated signals either by nutation or by spinning. When Independent Component Analysis (ICA) algorithms are applied on the outputs of appropriately modified trackers the reticle type dependent transmission functions, also called the source signals in the context of the ICA theory, can be recovered on the basis of the output signals only. Position of each optical source is obtained by applying appropriate demodulation method on the recovered source signals. The three conditions necessary for the ICA theory to work (statistical independence and non-Gaussianity of the source signals and nonsingularity of the mixing matrix) are shown to be fulfilled in principle for any kind of the reticle geometry. In relation to some IR counter-countermeasures algorithms which are based on heuristic and sometimes unrealistic assumptions (target performs no maneuvering) the approach exposed here has been proven to be theoretically consistent without any special constraints imposed on the optical sources.

Boeing has demonstrated Mid-Wave Infrared (MWIR) imaging performance of a large format tactical sensor based on a 1024x1024 focal plane array (FPA). The ultra-high density infrared (IR) sensor system consists of a 10.47 mm aperture optics, a 1024² Mercury Cadmium Telluride (HgCdTe) FPA, a Sterling cycle integrated cooler dewar assembly (IDA), and a pre-processor with advanced algorithms for data correction and image enhancement. In this paper, we will present measured performance parameters of the staring sensor system including minimum resolvable temperature (MRT), noise equivalent temperature difference (NEDT), and noise equivalent irradiance (NEI). Key features and attributes of the integrated hardware will also be described. A similar instrument to enhance situational awareness is under evaluation as part of a panoramic camera system to demonstrate feasibility of sensor-guided landing in adverse environments for heavy transports such as the Boeing C17 aircraft. Considerations are underway to utilize the camera as part of the Joint Strike Fighter (JSF) sensor suite. We will introduce other system applications for which the large format imagery can be strategically employed and discuss its operational advantages.

This paper describes a model-based method for the automatic recognition of high value targets in multisensor data. A production net is used to represent the knowledge about target structures. The analysis is carried out by a blackboard-based production system with a database stored in an associative memory. The efficiency of the analysis system is illustrated by an example involving the detection of bridges. For this, sensor data has been interpreted which were recorded with an experimental dualmode sensor (IIR, mmW) mounted to a helicopter while flying over the scenario. Image sequences are taken in oblique view with high frequency. The analysis starts with an intra-frame process by extracting cues in the actual sensor data and by the combination of orthogonal information of IR (intensity, direction) and radar (RCS, range) data to estimate target location in space. To improve detection and reduce false alarms, inter-frame processing is applied to exploit intra- frame results of overlapping images of the scanning sensor system resulting in a higher confirmation of the real target and a better discrimination of false alarms.

Birds are a potential source of frequent false alarms in Infrared Search and Track (IRST) systems. One reason is that the signals, generated by birds at short ranges (1-2 km) in IR sensors may be of the same magnitude as the signals generated by real targets (missiles) at long ranges (10-20 km). Another reason is that new generations of IRSTs have more sensitivity which brings more birds within the detection range. Furthermore military operations tend to be held more and more in coastal zones, where the frequency of occurrence of birds is greater than in the open ocean. Finally, the variety in type of birds and their flight characteristics and signature is larger. In the paper attention is spent on the IR signatures of birds in various backgrounds, including rapid variations in signature due to wing motions. Basically, these fluctuations and the flight pattern of a bird provide opportunities to encounter bird alarms in next generation IRSTs, using multiple Focal Plan Array cameras with high frame rates. One has to take into account in this process the difference between signal variations due to wing motions and scintillation for long range targets above the horizon.

We address the formation of a Viterbi algorithm for target tracking after detection. A target tracking after detection process can be made by a Kalman filter. The Kalman filter, however, may give some false tracks which are induced from false alarms. In this paper, we introduce an alternative approach to the target tracking based on the Viterbi algorithm. The state of the Viterbi algorithm includes the position and velocity of the target, and the measurement vector is the detected target position(in 2D). Because a target cannot maneuver abruptly due to its dynamical limitation, the velocity vector cannot be changed suddenly in direction as well as in magnitude. From this fact, we can define the state transition probability as a function of changes in angle and speed between the present state and the previous state. The proposed algorithm has been tested, and we observe that it tracks multiple targets accurately while the Kalman filter generates more tracks following clutter points. In addition, we have observed that a dynamic programming based approach fails to track the target.

This contribution presents a high-capacity computing device for the detection and recognition of objects appearing or moving in an infrared movie. A solution is shown as to how to extract objects from a data flow of up to 20 million pixels per second in real-time and how to display a target immediately after its appearance in the image observed. The hardware capability requirement is pointed out and the corresponding realization is explained on the basis of the algorithms. Currently, 17 high-performance microprocessors are combined for this special task. Modular design based on VMEbus technology, parameterization of hardware and the constraints to realize as many of the algorithms as possible in software guarantee a considerable growth potential by simply redoubling modules and adding new functions. Part of this paper discusses the human interface of the device, for it is evident that the value of the system depends on the quality of the information given to the operator. Results obtained from simulation and from functional tests on the device and possible future upgrades of the system are presented. The work performed to date has shown that image- processing software, implemented in a powerful hardware is the key issue for passive automatic target detection and recognition.

There are two kinds of video image sequence distortions caused by vibration of the camera. The first is the vibration of the line-of-sight causing location changes of the scene in successive frames. The second effect is the blur of each frame of the sequence due to frame motion during its exposure. In this work, the relative effects of these two types of degradations on the ability of observers to recognize targets are investigated. This study is useful for evaluating the amount of effort required to compensate each effect. We found that the threshold contrast needed to recognize a target in a vibrating video sequence under certain conditions is more affected by the motion blur of each frame than the oscillation of the line-of-sight. For digital sequence restoration methods, this study determines the required precision of the deblurring and registration processes. It shows that the deblurring process should not be neglected as it often is.

The changing reconnaissance tasks in the world demand new solutions which are influenced by different technical approaches. They range from individual image processing steps to powerful fusion and classification techniques. In order to develop, integrate and test image exploitation techniques, an experimental system for IR and SAR image exploitation has been realized. In this article we report on its technical features. Image data acquired during flight campaigns is fed into the experimental system to test and validate different image exploitation modules. The performance of integrated automatic target recognition algorithms is evaluated by systematic testing. This is illustrated on hand from some examples.

This paper describes a method to measure distance and attitude angle of flying target, which is based on moving or unmoving measurement platform. Related equations are presented. The method is verified and simulated in lab and applied to field trial.

China's first geostationary meteorological satellite FY-2 was successfully launched on June 10, 1997. The main effective payload onboard the satellite-the multichannel scanning radiometer (MCSR)-was developed by the Shanghai Institute of Technical Physics, Chinese Academy of Sciences. The scanning radiometer can acquire the Earth images from three channels of visible, infrared and water vapor simultaneously. From the images obtained one can see that the images are very clear with enough signal-to-noise ratio. This paper takes a brief look-back of the design and development of the optical system of the scanning radiometer.

Monte Carlo simulations are used to study the compositional changes in the near surface layer of HG_-xCd_xTe crystal substrate induced by F⁺ and Ar⁺ ion bombardment in the energy range of 0.1 to 5keV. The effects of the crystal structure of the substrate and the total dose used in the bombardment are involved in the simulations. Due to the preferential sputtering for different elements in the substrate and the difference of the displacement energies for these elements, remarkable redistribution of the constituent elements in the material are observed. The possibility of forming p-n junction by using the Hg enrichment layer near the surface as a diffusion source is discussed.

On June 10, 1997 China launched FY-2 Geostationary Meteorological Satellite into Earth-synchronous orbit with a Long March-3 rocket at Xichang Satellite Launch Center. The satellite is positioned at E105 degrees, 35800 km above the equator. Onboard the satellite there is a multichannel scanning radiometer (MSCR) which can acquire simultaneously Earth images from effective payload onboard the satellite, and it was developed by the Shanghai Institute of Technical Physics, Chinese Academy of Science. This paper mainly introduces the performances, operation principle, basic structure and in-orbit operation of the instrument.

The detection of infrared small and puny target is the critical problem for target tracking and recognition based on imaging sensors. Being limited to the complicated environment factors, measurement scale and precision of the sensors, the measurements are uncertain, imprecise or incomplete on certain level, and thus brings the difficulty for detecting target in real image. Usually the binary hypothesis method is used to examine the potential target from background in a single frame, then the detection probability can be raised and the false alarm probability can be reduced through the method of detection multiframe of the sequence image (namely K/N rule). In this paper, the target detection probability P_d and the false alarm probability P_f for a single image is calculated on the basis of the probability density function p(ZH₀) and p(ZH₁) on judgment regions Z₀ and Z₁. In N times measurement of a sequence image, the target is detected at least K times, then it can determine that the target is existent. The P_d and P_f of K/N rule are analyzed according to single frame. Applying K/N rule, the detecting probability and the false alarm probability can meet the demands of the system if choosing the value of N and K properly.

Although the interest in PtSi infrared focal plane array (IRFPA) has waned due to its low quantum efficiency compared with InSb and HgCdTe arrays, it is very potential in observing brighter celestial objects. We explored the possibility of applying it to the observation of infrared solar spectrum. In the paper, the methods of the simulation and calibration in our observation are introduced and discussed in detail. Using this kind of camera, a new observational band (FeI 1.56 micrometers ) is added to the Two- Dimensional Multi-Band Solar Spectrograph at Yunnan Observatory. The dispersion for FeI 1.56 micrometers of the new infrared solar spectrograph is 0.0722 angstrom per pixel, and each vertical pixel represents 0.51 inch of solar disk. It is specially suitable for 2D spectroscopic observation of the deepest solar photosphere. Some primary observation results are also presented.

The infrared source and detector are essential components of infrared analyzers. They basically determine the system's resolution, its size, energy demand and price. This paper describes the schematic set-up and the basic characteristics of radiators and pyroelectric single-element detectors that have been developed for the efficient application in the wavelength range 2-15 micrometers . On the one hand, the infrared sources are housed in a transistor package (TO-39, TO-8), electrical input power less than 10 watts and, on the other hand, in a glass bulb with a fitted infrared window, electrical input power 15-30 watts. They are based on tungsten filaments. It is shown that the radiators are optimized for high radiation power and a direct modulation capability with a sufficient modulation depth (50%) of up to 30 Hz. Calcium fluoride and zinc selenide were chosen as window materials. In particular for analytical applications, pyroelectric infrared sensors with small responsive elements have been developed, which are characterized by high responsivity, high specific detectivity and an optimized spectral responsivity. As a result, responsivity values S_v of (500 K; 10 Hz; 25 degree(s)C; (tau) _F equals 1)>=6,000 VW^-1 and a specific detectivity D*(500 K; 10 Hz; 1Hz; 25 degree(s)C)>=4 x 10⁸ cm Hz^1/2W^-1 have been obtained for LiTaO₃ sensors with a responsive area of 0.5 mm.

ZnS and CdTe layers are deposited by thermal evaporation on HgCdTe epilayers with xequals0.23 grown by MOCVD. Thermal evaporation is performed from commercial effusion cell in UHV chamber. The evaporation sources are ZnS and CdTe. Electrical properties of the ZnS/HgCdTe and CdTe/HgCdTe are determined by capacitance-voltage characteristics of metal- insulator-semiconductor test devices. It is found that the HgCdTe surface is slightly accumulated and the interface charge density of the order of low 10¹¹cm^-2 in both ZnS/HgCdTe and CdTe/HgCdTe structure. In the case of CdTe deposition, best results are obtained when the deposition rate is extremely slow of around 0.2A/sec. With this slow deposition rate, there is possibility of unintentional contamination from the residual gas in vacuum chamber into growing films. Thus, evaporation in a UHV environment is necessary for a sufficiently clean layer. The effect of Cd overpressure on surface charge of HgCdTe is presented. The main features of the ZnS and CdTe deposited from effusion cell in UHV chamber are low fixed surface charge density, and small hysteresis. The good electrical properties of the interface, thermal stability and chemical properties of ZnS and CdTe grown with very slow rate under ultra-high vacuum suggest that these layers can be applied for improving the surface passivation of photovoltaic devices fabricated on HgCdTe.

Experimental and theoretical studies of low-background behavior of extrinsic photoconductor detectors (EPDs) with a steady-state photoconductive gain G>1 and extrinsic double-injection photodiodes (EDIPs) were carried out. In both the cases, frequency response had two plateaus. It was established that four regions with various values of theoretical background limit of detectivity can be distinguished in the frequency range of EPDs. Temperature dependence of the 3-db cutoff frequency of low-frequency (LF) plateau for Si:Ga EPDs was found not to be described by existing models. This characteristic frequency sharply decreased with decreasing temperature (T<20K, background- limited current) and then became weakly dependent on temperature below 12 K. A model explaining this phenomenon through peculiarities of contact injection has been suggested. The responsivity of Ge:Hg EDIPs reached 2000 A/W, which corresponded to a gain of about 1000, and was about two orders of magnitude higher than that for EPDs of the same material. The ultimate detectivity in this case, nevertheless, was close to that of EPDs and the gain- bandwidth product was much greater. The decay segment between two plateaus on frequency response curve of EDIPs is more extended than that of EPDs, which is conditioned by great gain value for EDIPs. The high-frequency plateau of the curve is due to the displacement current, similar to EPD case, and the detectivity limit here is gain-dependent and lower than that for LF part of the curve, as well.

In this paper we present preliminary experimental results of static thermal mapping for the characterization of thermal properties of single or multilayer thin film membranes. Based on direct radiometric measurement, the proposed system is able to acquire, with high spatial (less than 10 micrometers ) and quite good temperature (less than 0.1 degree(s)C) resolution, the temperature maps. The results, reported here, confirm its capability. We tested a low stress LPCVD SiN membrane heated by means of a LPCVD polysilicon (PS) resistor. The experimental results obtained are in qualitative agreement with theoretical previsions.

Gallium-doped germanium (Ge:Ga) extrinsic semiconductor has been used as sensitive far-infrared detectors with a cutoff wavelength of 110 micron (2.7 THz), especially in the fields of astronomy, the spectroscopy of molecules and solids, and plasma diagnostics. Developing Ge:Ga photoconductor arrays to take two-dimensional (2D) THz images is now an important target for research fields such as the space astronomy. We present the basic idea of a 20x3 Ge:Ga far-infrared photoconductor array directly hybridized to a Si p-MOS readout integrated circuit (IC) using indium bump technology, which is an advanced structure for far-infrared detector arrays. The main issues to achieve in creating a 2D array are summarized as follows: the fabrication of a monolithic Ge:Ga 2D array with longitudinal configuration, development of the cryogenic readout electronics, and the development of technology for connecting the detector with the electronics. We report that the detector was cooled to 2.1 K, the best responsivity obtained was 16.2 A/W and the best NEP was 2.6x10^-17W/Hz^1/2 at a bias field of 1.2 V/cm. We demonstrated that p-MOS FETs can be used as the cryogenic readout electronics. And we succeeded in the far-infrared detection by using direct hybrid structure photoconductors. The results of vibration and cooling tests were conducted to confirm the strength of the direct hybrid structure. Our Ge:Ga photoconductor direct hybrid 2D array will be an excellent device for taking 3 THz images.

Dielectric polarization noise, which can be predicted by the fluctuation-dissipation theorem, is generated in materials that have dielectric loss. The materials around the gate circuit of an FET may generate dielectric polarization noise because these materials have dielectric loss. We measured the noise of both these materials and the devices, and fabricated an ultra-low-noise readout circuit by removing as many high-noise materials as possible and replacing the high-noise devices with lower-noise devices. The main noise sources in the circuit were the p-n junctions of the photodiode and the Si JFET, the feedback capacitor, and the electrode that connects them. A readout-noise level of ten electrons was achieved at 77 K using a photodiode with a capacitance below 1 pF.

We report an advanced Hg_1-xCd_xTe photovoltaic detector based on monolithic Hg_1-xCd_xTe heterostructure with 3-dimensional architecture. It consists of a narrow gap, p-type Hg_1-xCd_xTe small size (approximately equals 10x10x7 micrometers ) absorber of infrared radiation buried in a graded gap Hg_1-xCd_xTe layer surrounding absorber and heterojunction contacts obtained by selective doping of the graded gap Hg_1-xCd_xTe layer surrounding the absorber region. The heterostructure is passivated with a ZnS layer and coated with contact metallization to n^PLU and p-type regions. The device is supplied with 50x50 micrometers immersion microlens formed directly in the CdZnTe substrate. These two layers also play a role of a mirror that improves quantum efficiency for weakly absorbed infrared radiation. In addition, the mirror eliminates backside incidence of thermal radiation, which prevents generation of dark current. The design of the device is optimized to achieve the best compromise between requirements of good absorption and collection efficiency; low thermal generation; and low parasitic impedance. Test devices have been prepared using the modified isothermal vapor phase epitaxy of Hg_1-xCd_xTe on profiled CdZnTe substrates, negative epitaxy of Hg_1-xCd_xTe to widen band gap of surface regions, selective doping, multiple chemical etching and ion milling, vacuum deposition of dielectric and metal layers.

We investigated microposition sensing of micro-electro- mechanical systems (MEMS) that is based on optical readout techniques. We determined the parameters that affect or limit the performance of optical readout techniques especially as they apply to detection of infrared radiation. Such microposition sensing schemes are very important as readout mechanisms for large arrays of microstructures which are required for imaging. In addition, we explored the performance of uncooled micromechanical IR sensors using Fresnel zone plates (FZP). This type of diffractive feature diffracts along the optical axis and not perpendicular to that axis. We found that temperature fluctuation noise and background fluctuation noise, are currently the limits to the performance of uncooled micromechanical IR detectors. The noise at the output of the optical readout includes amplified noise from the micromechanical structures and noise added by the optical readout itself. However, the added noise is negligible compared to the amplified temperature fluctuation noise inherent in the microstructures. In this context an optical readout is nearly an ideal, noiseless readout method.

Full video format focal plane array (FPA) modules with up to 640 x 512 for high resolution imaging applications in either mercury cadmium telluride (MCT) mid wave (MWIR) infrared (IR) or platinum silicide (PtSi) and quantum well infrared photodetector (QWIP) technology as low cost alternatives to MCT for high performance IR imaging in the MWIR or long wave spectral band (LWIR) have been presented in several earlier publications. MCT units provide fast frame rates >100Hz together with state of the art thermal resolution NETD <20mK for short snapshot integration times of typically 2ms. PtSi and QWIP modules need longer integration times and are usually operated at frame rates of 30-60Hz to provide thermal resolutions of NETD <80mK for PtSi and NETD <20mK for QWIP, respectively. Presently, 2 new MCT detection modules are under development to provide lower geometrical resolution but much faster frame rates and dual color capability. The modules are specifically useful for missile seeker and ir search and track (IRST) applications where fast frame rates are needed or where dual color capability helps to suppress clutter, detect specific ir signatures or discriminates camouflaged targets. A high speed device with 256x256 pixels in a 40micrometers pitch is designed to provide up to 800Hz full frame rate with pixel rates as high as 80Mpixels/s.

This paper provides a review of the significant progress achieved in uncooled VO microbolometer LWIR focal plane and sensor technology at The Boeing Company during the last four years. When Boeing (formerly Rockwell) first introduced its first 320x240 uncooled FPAproduct in 1996, the U3000, it had a specified product NETD <0.1 K (F/i). Today, as a result of on-going improvements in VOx microbolometer design, processes and materials, the U3000 product is an established workhorse that is achieving an F/i NETD in the range of 0.033 to 0.040 K. The new U4000 320x240 product, that is being introduced by Boeing this year, has already demonstrated an F/i NETD <0.023 K at a 60 Hz frame rate, while having a thermal time constant <0.025 sec. In addition, significant progress has been made with innovative uncooled sensor operating concepts. Boeing has demonstrated its "TCOMP" response and offset compensation concept, which allows the uncooled IRFPA to operate without the need for temperature regulation. The elimination of the need for temperature regulation also means that uncooled LWIR imaging sensors can now have essentially instant-on operating capability, while requiring significantly less power. Spatial F/i NETD as low as 0.027 K, which is a measure of the level of spatial pattern noise in the displayed sensor image, has been demonstrated with a U4000/TCOMP sensor, and TCOMP has already been demonstrated over an at least 30 K calibration range.

This paper describes a new test bench for measuring the modulation transfer function of an infrared focal plane array. The system is based on the use of a plane target made of eight gratings that projects in polychromatic light a biperiodic pattern of small and nondiffracting spots called a nondiffracting array.

A new thermal infrared detector using temperature characteristics of a diode has been developed. This micromachined isolated silicon diode for IR detection (MISIR) utilizes an electrochemical etching technique to achieve the thermal isolation of the diode. Experimental dependence of the diode current on the junction temperature enables a high responsivity of the MISIR and the electrochemical etch stop provides an effective isolation at simple and low-cost. The fabricated MISIR has demonstrated a detectivity of 1.2x10¹⁰(cm(DOT)Hz^HLF/W) at room temperature in air ambient.

Irradiation of a photodetector by very short pulses is presented as the primary and perhaps the only remote technology for altering the SNR. Such noise manipulation will decrease the SNR value for certain types of common MIR and LWIR photodetectors. The effect is based on the differences between carrier lifetime, detector material heat transfer rate and altering pulse dwell time. When the pulse width is much less than photodetector rise time, most of the photons cannot generate free carriers, but only heat. Since the heat transfer rate in semiconductors is much slower than carrier's lifetime, high temperature will affect the detector much longer than common input signal correlation length or frame period. We describe thermal, radiometric and electronic circuit models developed to simulate the transfer of short pulses of time-dependent radiant and electrical signals through a photodetector during the alteration. The models are developed to provide an analysis tool for evaluating the time-dependent radiometric sensitivity for the remote gain control of IR photodetectors.