High-temperature superconducting microbolometer silicon microstructure infrared arrays offer the potential of lowest possible production cost combined with high performance for use in infrared imaging systems. Linear arrays employing thin films of yttrium barium copper oxide have been prepared. Small two-dimensional arrays are under development. A 240 X 336 array of 50 micrometers X 50 micrometers pixels operating at 85 K at 30 frames per second with f/1 optics has a theoretical noise equivalent temperature difference of 2.0 X 10^-3 deg K.

Utilizing the low temperature silicon molecular beam epitaxy (MBE) growth of degenerately doped SiGe layers on Si, long wavelength stacked SiGe/Si heterojunction internal photoemission (HIP) infrared detectors with multiple SiGe/Si layers have been fabricated and demonstrated. The detector structure consists of several periods of degenerately boron doped thin (20 cm^-3) has been achieved and high crystalline quality multiple SiGe/Si layers have been obtained. For the experiment several stacked Si_0.7Ge_0.3/Si HIP detectors with various SiGe layer thickness and doping concentration have been fabricated. The detectors have exhibited strong infrared absorption and near ideal thermionic-emission dark current characteristics. For the stacked Si_0.7Ge_0.3/Si HIP detectors with [B] equals 4 X 10²⁰ cm^-3, strong photoresponse at wavelengths ranging 2 to 20 micrometers has been measured. The effects of doping concentration on the detector optical and electrical characteristics have been studied. Using the measured quantum efficiency and dark current data, detectivity (D_(lambda )*) of detectors has been estimated.

A precise evaluation of the photodiode storage capacitance in a platinum silicide Schottky- barrier IR image sensor with an optical cavity and in which an aluminum reflector is electrically grounded has revealed that the cavity capacitance between the aluminum reflector and the platinum silicide film, which is one of four components in the photodiode storage capacitance, is dominant. While this area of the photodiode has previously been investigated for its optical characteristics, the present study represents the first reported investigation on its electrical characteristics. In order to increase the saturation level of an image sensor, it is essential to increase the storage capacitance in its photodiode. The storage capacitance in the photodiode was shown to be increased not only by newly using but also by increasing the cavity capacitance. When the SiO₂ film between the aluminum reflector and the platinum silicide film was replaced with SiN, total storage capacitance in the photodiode was successfully increased by a factor of 1.6, while the optical characteristics of the photodiode remained the same.

By incorporating a 1-nm-thick p⁺ doping spike at the PtSi/Si interface, we have successfully demonstrated extended cutoff wavelengths of PtSi Schottky infrared detectors in the long wavelength infrared (LWIR) regime for the first time. The extended cutoff wavelengths resulted from the combined effects of an increased electric field near the silicide/Si interface due to the p⁺ doping spike and the Schottky image force. The p⁺ doping spikes were grown by molecular beam epitaxy at 450 degree(s)C using elemental boron as the dopant source, with doping concentrations ranging from 5 X 10¹⁹ to 2 X 10²⁰ cm^-3. Transmission electron microscopy indicated good crystalline quality of the doping spikes. The cutoff wavelengths were shown to increase with increasing doping concentrations of the p⁺ spikes. Thermionic emission dark current characteristics were observed and photoresponse in the LWIR regime was demonstrated.

A monolithic PtSi charge coupled device (CCD) focal plane array (FPA) has been developed. The array contains 656 X 492 pixels with 46% fill-factor and 26.5 micrometers square pitch. A single on-chip amplifier is used to read out the video at 12.5 MHz to provide standard 30 frames per second format. The devices are produced in Loral Fairchild's CCD facility in Milpitas, California. Excellent performance and yield have been achieved from initial wafers. Device design and performance test results are described.

The HgCdTe (MCT) 64 X 64 focal plane array (FPA) for long wavelength infrared (LWIR) detection was developed, using MCT epilayers grown by molecular beam epitaxy (MBE). The n-on-p photodiode array has a cutoff wavelength of 10.7 micrometers . The readout circuit, with off focal plane integration capacitance, was designed for 77 K operation. These components were fabricated independently and were hybridized. The 97.8% operability was obtained. Photodiode characteristics for each pixel were measured directly. Mean R$o)A value of 1.9 (Omega) (DOT) cm² and quantum efficiency of 0.3 were obtained. Using an infrared camera system with nonuniformity correction function, the infrared image was successfully demonstrated. An NETD (noise equivalent temperature difference) value of 0.117 K was attained with an F/2.5 optical lens under the 300 K background condition.

We have developed a hybrid HgCdTe focal plane array (FPA) for wavelengths from 8 to 11 micrometers . We describe how we fabricated our back illuminated 64 X 64-element photodiode array on a liquid phase epitaxial (LPE) HgCdTe wafer, and a Si CCD multiplexer with line address readout. We optimized carrier concentration in the p-type HgCdTe layer to maximize charge injection efficiency to the Si CCD readout circuit to more than 99.3%. We achieved excellent uniformity of characteristics of the photodiode array, which is very important for an IRFPA, by using LPE HgCdTe grown with a tipping method, and passivating the photodiode array with an anodic sulfide of HgCdTe. We obtained an average product of zero-bias resistance and area (RoA) of 9.1 (Omega) cm² with a cutoff wavelength of 10.6 micrometers at 77 K. We used line address readout to give a large charge storage capacity of 4 X 10⁷ electrons. We estimated a noise equivalent temperature difference (NETD) of 0.08 K with F/2.5 optics, including fixed pattern noise. We tried some preliminary experiments to reduce the crosstalk from photogenerated carriers which spread laterally into the epitaxial layer. We improved the modulation transfer function (MTF) at Nyquist spatial frequency from the conventional 35% to 60% by using a crosswise drain structure around each photosensitive n⁺ on p diode.

A new current readout circuit for infrared (IR) detectors, called the share-buffered direct- injection (SBDI) circuit, is proposed and analyzed. It is found that the proposed SBDI readout structure can achieve the high readout performance as the conventional buffered direct- injection structure (BDI), but only with half chirp area and power dissipation. A new output stage with a dynamic discharge structure is also used to overcome the conventional readout speed bottleneck. It is clearly shown through the analysis that the proposed SBDI structure and the associated design technique can be applied to the readout circuit design of the two- dimensional focal plane array and achieve the same performances as the one-dimensional BDI structure.

The Advanced Air Defense Electro-Optical Sensor (AADEOS) is an Advanced Technology Demonstration (ATD) Program ground-based Infrared Search and Track (IRST) system intended for use by U.S. Army Forward Area Air Defense (FAAD) units. It is designed to provide automatic detection and tracking of rotary wing and fixed-wing aircraft. The AADEOS has been built and is currently being evaluated at Fort A. P. Hill, Virginia. The evaluation includes collecting IRST video data of military aircraft and background clutter used to train target/clutter discrimination algorithms. The operational performance of the system (i.e., the declaration range and false alarm rate) is being estimated.

Design criteria for IRST systems are investigated based on calibrated imagery of sea backgrounds under different weather conditions with and without fixed and moving point targets. Image sequences are taken using the GEC DUWIR camera (3 - 5 and 8 - 12 micrometers ) equipped with a 2 degree(s) field-of-view (FOV) telescope. Image sequences of backgrounds are analyzed with respect to their inherent `point structure content' for complexity classification using a specific multi window operator. The behavior of the fixed point targets with respect to apparent spatial and temporal intensity variations in the imagery is separated into atmospheric and sensor systems effects. The original imagery [image sequence: 25 Hz, instantaneous field-of-view (IFOV): 0.08 mrad] is used with reduced spatial and temporal resolution to test point detection and tracking algorithms for realistic IRST sensor layouts. Various optical and signal processing configurations were explored and merits of each are discussed in this paper.

Our algorithm development for point target surveillance is closely meshed to our laboratory IR cameras. The two-stage approach falls into the category of `track before detect' and incorporates dynamic programming optimization techniques. The first stage generates merit scores for each pixel and suppresses clutter by spatial/temporal subtractions from N registered frames of data. The higher the value of the merit score, the more likely that a target is present. In addition to the merit score, the best track associated with each score is stored; together they comprise the merit function. In the second stage, merit functions are associated and dynamic programming techniques are used to create combined merit functions. Nineteen and thirteen frames of data are used to accumulate merit functions. Results using a total of 38 and 39 frames of data are presented for a set of simulated targets embedded in white noise. The result is a high probability of detection and low false alarm rate down to a signal to noise ratio of about 2.0. Preliminary results for some real targets (extracted from real scenes and then re- embedded in white noise) show a graceful degradation from the results obtained on simulated targets.

The all-sky infrared mapper Scorpio has been developed at TNO-FEL. This system operates in the 3 - 5 micrometers and 8 - 13 micrometers wavelength bands, and creates calibrated all-sky images in 80 seconds with a resolution of 0.8 mrad. This cloud mapper is used to obtain infrared images of the sky (mainly at 10 micrometers ) in an on-going study for statistical properties of the sky and cloud infrared radiation, i.e., infrared clutter and cloudiness. Scorpio is also useful for more general cloud and sky background studies. In this paper all-sky images are presented together with all-sky clutter maps. A method is developed to obtain these clutter maps and to derive clutter information from these clutter maps. An analysis of clutter variations with cloud height and with elevation is presented. Preliminary results show a dependence between clutter and cloud height and elevation.

The use of the 3 - 5 micrometers (MWIR) spectral region for IR search and track (IRST) systems is sometimes dictated by operational and technological factors. In daytime, sun scatter from the background may cause the inherent target contrast in this band to be washed out or even reversed in polarity. This paper examines the effect of scattered sun radiation on target contrast for three types of sensor scenarios -- surface based, airborne, and space based. The analysis was carried out using the LOWTRAN 7 computer code. Critical angular relations between the sensor line-of-sight and the sun direction were identified and optimum spectral bands, based on target contrast considerations, are suggested for sensors employing InSb and PtSi detectors. A set of field measurements in a surface-based sensor scenario is presented to illustrate the sun scatter analysis.

The effect of global clutter is discussed from the vantage point of selecting the best model for background IR scenery. Methods based on the human visual system and on the latest models for image composition are discussed.

An ideal infrared search and track sensor will cover 4 (pi) steradians, but will have diffraction limited resolution for clutter rejection, noise control, and raid count. In addition it will have an imbedded active sensor that will complement the clutter rejection, provide instantaneous object range, and will provide other object recognition. This sensor will have no moving parts and will be very producible. Such an ideal sensor would be very sensitive, so it can be used to detect and track low temperature targets at long range. While the complete goals specified above are beyond intermediate term state of the art an approach does exist to satisfy these goals in the intermediate term. This approach is to use a coarse resolution passive sensor and use the active sensor to eliminate false alarms. A random access pointing capability is required from the active sensor. Optical space fed phased array technology is discussed as a method of providing that random access pointing capability.

The paper describes an infrared scene generator (IRSG) mounted on a Flight Motion Simulator (FMS) for hardware in the loop simulation of IR air to air missile seekers. The scene generator projects target, flare and background images, that are optically collimated to the seeker under test. The target and flare images are generated using high temperature (1200 degree(s)C) blackbody sources and controllable irises. A dynamic Variable Neutral Density Filter (VNDF) is used in the target and flare channels to simulate the range closure and attenuation effect of the atmosphere. The background channel consists of a back illuminated IR transparency located in front of an extended area blackbody. The target flare and background images are combined using two beam combiners. One of the beam combiners has two degrees of freedom to simulate the motion of the flare relative to the target within the field of view (FOV) of the IRSG.

In this paper methods and software for analysis and optimization of IR optical-electronic systems (OES) with on-board computer for detection of point target signals in complex natural background are discussed. Analysis and optimization are based on simulation of background and signals situations, optical-electronics highway and on-board information processing. The software is intended for OES computer aided design. It takes into account the non-linear characteristics of elements and the technological confusion of OES parameters. The software realizes natural background and point target signal situations classification with background brightness fields non-stationary. The fields of view are over 100 sq. degrees. Software includes region and climate model of regions of monitoring.

On-board information processing of high productive optical-electronic systems for point target signals detection in complex background is presented in this paper.

The use of infrared sensors in the Netherlands is substantial. Users can be found in a variety of disciplines, military as well as civil. This need for IR sensors implied a long history on IR technology and development. The result was a large technological-capability allowing the realization of IR hardware: specialized measuring equipment, engineering development models, prototype and production sensors for different applications. These applications range from small size, local radiometry up to large space-borne imaging. Large scale production of IR sensors has been realized for army vehicles. IR sensors have been introduced now in all of the armed forces. Facilities have been built to test the performance of these sensors. Models have been developed to predict the performance of a new sensor. A great effort has been spent on atmospheric research, leading to knowledge upon atmospheric- and background limitations of IR sensors.

Results are presented of noise reduction by motion compensated temporal filtering in a noisy IR image sequence and of moving target detection in an air-to-ground IR image sequence. In the case of motion compensated temporal filtering our approach consists of estimating the optical flow between successive frames and subsequently averaging a small number of images. Moving targets are detected by first estimating the optical flow between successive frames. Target detection amounts to comparing a predicted frame, based on the estimated optical flow, to the actual frame. Thus, it is possible to detect targets without making assumptions on their appearance. The particular motion estimator used was found to be especially useful in the case of IR imagery, because the estimator is relatively insensitive to noise and global brightness variations.

Propagation of electro-magnetic radiation in the marine atmospheric boundary layer is discussed, with emphasis on aerosol effects on extinction. An outline of the atmospheric module of the FEL-TNO range predictor is presented. This model is developed to predict the maximum detectable range of a sensor-target combination both for open ocean and coastal marine environments. The effect of meteorological parameters (wind speed, wind direction, relative humidity and air-sea temperature difference) on the maximum detectable range is discussed.

Detection, recognition, and identification ranges for targets in backgrounds are determined by the combined signatures of both target and background. Since the signatures of backgrounds are determined by many variable conditions, such as by illumination, weather, season, time, range and line of sight, the recognition and identification ranges for targets embedded in backgrounds will vary with these conditions, even when the target signature is kept constant. In order to improve our understanding of the temporal behavior of cluttered backgrounds at infrared (IR) wavelengths in varying meteorological conditions, a series of experiments are described to model sequences of acquired IR images using basic meteorological parameters recorded by a synoptic weather station. The acquired imagery contains two sequences of 335 and 490 thermal images recorded every 5 minutes over a period of approximately 2 days in stable, clear weather conditions in mid-latitude winter and summer respectively. Multi-variate linear regression algorithms using basic meteorological variables are used to model the temporal character of each pixel in the sequences of images.

The IR contrast of ships at sea is of importance for those who want to detect or identify the ship and for those who worry about this. This IR contrast is determined by a large number of parameters. Of course temperatures of the ship's structure and those of the ambient sea and air are important, but also important are the reflection properties of the sea background and the radiance distribution of the surrounding sky. Modeling of these phenomena appears to be very complicated and the accuracy of the results is rather course in many cases. Therefore, at FEL- TNO an approach has been followed, using a package of sensors on board the ship, giving radiometric or real temperature data of specific surface elements and background radiometric data. These data are taken into a PC system, providing radiant contrast data in any IR-spectral band. Taking into account atmospheric propagation effects and sensor performance, a simplified detection model provides range data in the form of polar diagrams with elevation as parameter. The commander of the ship uses the system as an IR Tactical Decision Aid (TDA), as he may decide upon countermeasures, if the vulnerability of his ship exceeds certain limits.

This paper gives an overview of the activities on Infrared Fourier Transform Spectroscopy at the TNO-Physics and Electronics Laboratory. Spectra are shown for aircraft plume emission and transmission through wildfire smoke and missile plume smoke. These examples demonstrate the possibilities of these techniques to identify gases and to determine their concentrations and temperatures. Calibration techniques are discussed, which are required to obtain quantitative data on emission and transmission.

In the Netherlands, the information need in water management is to a large extent met by water quality monitoring programs based on point measurements. Remote sensing techniques can provide additional information, as a synoptic view over larger areas. Thermal infrared remote sensing is used for water surface temperatures mapping. The potential of this technique was tested in a number of projects with thermal scanner survey flights. Results of selected case studied are presented. It was concluded that the particular value is in effluent and waste water discharge detection, stream patterns and modeling studies. Procedures for implementation were not formulated. Application of the technique is primarily in the framework of the Pollution of Surface Waters Act. Evaluation has shown that implementation at user's level requires (near) real time detection of discharges followed by rapid action by ground control teams. These requirements can be met by using the new remote sensing airplane of the Netherlands Coast Guard. Results of a test program in the summer of 1993 are expected to show that this airplane using thermal infrared remote sensing is a powerful instrument in enforcement of environmental legislation.

The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) has been selected by ESA for the ENVISAT-Mission, scheduled for launch in 1998. The instrument will measure the concentration of a number of atmospheric trace gases in the earth atmosphere in a spectral region from 4.15 - 14.6 micrometers . Within this region measurements are performed with high spectral resolution. The MIPAS optical system consists of scan mirrors, a telescope, a Michelson interferometer, an afocal reducer and a focal plane assembly. TNO Institute of Applied Physics is involved in the design and development of the afocal reducer and the focal plane assembly. The beam reducing optics of the afocal reducer consist of 2 concave and one convex mirror. Both the housing and the mirrors are made of aluminum to ensure temperature invariance. The optics of the focal plane assembly consist of aluminum mirrors, dichroic beamsplitters and Ge lenses in front of the detectors. The optical/mechanical design is developed to the level that phase C2/D activities can start.

A review of infrared readout electronics for space science sensors is presented. General requirements for scientific IR FPA readout are discussed. Specific approaches to the unit cell electronics are described with respect to operation, complexity, noise and other operating parameters. Recent achievements in IR FPA readout electronics are reviewed. Implementation technologies for realization of IR FPA readout electronics are discussed. Future directions for addressing NASA and other scientific users' needs are suggested.

An overview is presented of the status of a family of miniature linear coolers currently under development by Hughes Aircraft Co. for use in handheld, volume limited or power limited infrared applications. These coolers, representing the latest additions to the Hughes family of TOP^TM (twin-opposed piston) linear coolers, have been fabricated and tested in three different configurations. Each configuration is designed to utilize a common compressor assembly resulting in reduced manufacturing costs. The baseline compressor has been integrated with two different expander configurations and has been operated with two different levels of input power. These various configuration combinations offer a wide range of performance and interface characteristics which may be tailored to applications requiring limited power and size without significantly compromising cooler capacity or cooldown characteristics.

The discovery of high temperature superconductors (HTS) spawned many potential applications, including optical detectors. Realizing viable superconducting detectors requires achieving performance superior to competing and more mature semiconductor detector technologies, and quantum detector technologies in particular. We review why quantum detectors are inherently more sensitive than thermal or bolometric detectors. This sensitivity advantage suggests that for operation at cryogenic temperatures we should be developing only quantum superconducting detectors. Accordingly, we introduce and describe the structure and the operation of a superconducting quantum detector with a SQUID read-out circuit. The superconducting quantum detector, consisting of a superconducting loop, produces a photosignal in response to photoinduced changes in the condensate's kinetic inductance. The superconducting quantum detector is designed to operate only in the superconducting state and not in the resistive or transition states.

1. Review of HIDAD Focal Plane Development • Ferroelectric Detector • Bolometric Detector 2. Performance Status 3. Theoretical Underpinnings 4. LOCUSP • Prototype Description • Field Test 5. Future Directions • Military/Civilian 6. Conclusions 7. Video Tape

This article summarizes the characteristics of Honeywell's two-dimensional (2-D) arrays of micromachined microbolometers, discusses practical methods of operating these arrays in high-sensitivity room-temperature infrared (IR) imaging systems, and describes recent performance measurements.

Texas Instruments is active in productizing uncooled thermal imaging systems for commercial and military products. The technology is based on the field-enhanced pyroelectric effect in ferroelectric barium-strontium titanate. The detector is mated to a readout IC (ROIC) via bump-bonding, and the single output from the ROIC is processed serially to provide both 8-bit digital and NTSC video outputs. Overall system cost is minimized and the electronics are simplified by using a scene-averaging chopper and operating the detector in its inherently ac- coupled mode. The past two years have been devoted to improving producibility, primarily of the uncooled focal plane array (UFPA) and its package. The result is a detector process that is 95% compatible with standard silicon processing. Although explicit performance improvement has been a secondary priority, the producibility improvements have led to a factor of two improvement in sensitivity. Recently demonstrated NETD is 0.047 degree(s)C with f/1 optics.

For an uncooled, `room temperature,' ambient temperature near 300 K, IR detector array for resolved ground targets such as vehicles, a bolometric array is superior to other types. Of the several bolometric types, the thermistor is probably the best. Large arrays (about 350 by 250 pixels) can be built using standard silicon lithographic technology. The time constant of a detector element is about 10 ms so that standard TV raster and display can be used. Though NEdT below 30 mK is attainable with detectors on 50 micrometers centers, inversely proportional to the spacing of the detectors, it is more likely that NEdT of only 40 mK will be available because of practical problems in the focal plane array design and operation. A comparison is made between MWIR photodiode and wide band bolometric detector arrays. A static noise model is developed including radiation noise both from the scene and from the detector itself (considering its heating by the bias power of the thermistor), the thermistor resistor, the bias current and the preamplifier. This model is modified to include low duty cycle pulsed bias.

Operation Desert Storm has identified the need for improved battlefield surveillance sensors to see and assess enemy threats under all battlefield conditions, including darkness. Current imaging sensors usually employ visible light cameras, Low Light Level (L³), Image Intensified (I²), or conventional Infrared (IR) cameras to detect and observe hostile forces. However, these sensors have serious deficiencies. The visible TV camera requires well lighted areas and cannot image in darkness. The L³ TV cameras have a difficult time operating in bright sunlight or in total darkness. Image intensifiers require some ambient light and cannot penetrate camouflage or battlefield obscurants. Conventional FLIRS are costly, require an initial cool down period, and need additional power for cooling pump or periodic gas replenishment for long-term operation. Uncooled Focal Plane Array (FPA) LWIR sensors offer advantages over other imaging sensors. Uncooled IR sensors operating from 8 to 12 microns can easily operate in bright sunlight, or total darkness. They use the naturally radiated IR scene energy to create high resolution images and are not dependent on artificial light sources. Their long wave-length of operation also provides better weather penetration. Enemy vehicles and soldiers can easily camouflage themselves in the visible, but cannot hide their thermal emissions from the IR sensor.

The technology behind infrared focal plane arrays capable of operating at room temperature is discussed, emphasizing bolometric and pyroelectric devices. Theoretical limitations of thermal imagers operating at room temperature are explored and presented. The results of a survey cataloging the capabilities of currently available room temperature infrared focal plane arrays are presented. An example of how this technology could perform in a real world situation is presented from a theoretical point of view to show possible imaging system limitations due specifically to the room temperature focal plane.

Large arrays of bolometer elements have considerable potential for thermal imaging applications, offering uncooled operation, and a performance which challenges the cooled semiconductor detectors. A hybrid array technology, exploiting ferroelectric materials, is the basis of a successful range of linear and 2-D arrays. The success is based on hot-pressed ceramics (operating in both pyroelectric and dielectric modes), and the technologies for solder bump bonding and element reticulation. Arrays are increasing in size, from 10⁴ elements up to 10⁵ elements while the pitch is reducing, thus providing high resolution in compact systems. Ferroelectric thin films have recently shown marked improvement in the merit figures and, if compatible with the silicon IC, will allow a more direct array fabrication. These integrated array technologies have potential for high yield and low cost in very large area devices.

We have developed a `1M-IRCSD imager' for thermal imaging in the 3 to 5 micrometers band. The device of this imager is a 1040 X 1040 monolithic PtSi Schottky-barrier (SB) array using the charge sweep device (CSD) readout architecture. In this imager system, four video signals are read out from four independent channels on the chip. The processing of these four outputs, such as sample and hold (S/H), offset control and image correction, is performed in parallel, after which these outputs are combined to produce High Definition TV (HDTV; 1125 lines, 30 Hz) format thermal image in real time. The noise equivalent temperature difference (NETD) with F1.2 optics at 27 degree(s)C background is 0.13 degree(s)C at the HDTV output stage.

A self-contained IR camera system has been developed with preliminary performance measurements reported herein. The camera system includes a 256 X 256 indium antimonide (InSb) FPA, closed-cycle cryogenic cooling, and DSP-based electronics. All camera functions are contained within a small volume. Measured performance indicates the camera has very high sensitivity, low noise, and wide dynamic range.

A high performance 640 X 480 focal plane array has been developed for the 1 - 5 micron band with excellent sensitivity at temperatures below 120 K. The detectors are processed on 2' or 3' diameter PACE-I (producible alternative to CdTe for epitaxy) HgCdTe material. The multiplexer is a direct injection input, switched-FET device with four independent quadrants. The detector is hybridized to the multiplexer through indium columns and is characterized. A mean camera NE(Delta) T (noise equivalent temperature difference) of 13 mK has been achieved for temperatures <EQ 120 K. Background-limited (BLIP) D* of 1 X 10¹² Jones (cm-(root)Hz/W) has been measured for 10¹⁴ phs/cm²-s background at 95 K. The hybrids have been thermally cycled for 15 times with no interconnect loss. Interconnect yields as high as 99.3% have been achieved.

Segmenting of the incident wavefronts at the entrance pupil of an imaging system occurs in systems with segmented windows and in certain configurations of scanning systems that include a polygon as the scanning element. The segmenting of the wavefronts may cause a serious degradation of the MTF of the system. In some cases, the resolution of such systems may be decreased by a factor of two. The degradation of the MTF is calculated for monochromatic and polychromatic light. It is shown how such cases may be simulated using Code-V software.

A survey is presented of algorithms for the display and enhancement of infrared images developed over the last several years by the author and his colleagues. Our algorithms were driven by the need to map the raw recorded signal (digitized to 12 bits for single frames grabbed with our cameras) into 8-bit values for soft-copy display or real-time automatic- contrast operation on live camera imagery. We group the algorithms into two broad classes: global monotonic mappings in which the radiometric trend from low to high in the recorded image is retained in the displayed images; and mappings which depart from the global/monotonic constraint for purposes of local contrast enhancement. In the discussion of global display algorithms, we compare the Histogram Projection algorithm devised several years ago and widely used in auto-contrast circuits with the standard technique of Histogram Equalization. For complex histograms and wide dynamic range scenes, a compromise or `hybrid' of the display allocation specified by these two histogram techniques is desirable.

An objective method has been developed for measuring the minimum resolvable temperature difference (MRTD) of infrared imaging systems employing focal plane detector arrays. The resulting MRTD is uniquely determined by applying discrete Fourier transform techniques, thus avoiding the previous multi-valued problem associated with the non-isoplanatic property of discrete devices. The derivation is based on sinusoidal wave input targets but a practical measuring procedure has been developed using conventional bar patterns; alternatively the MRTD may be calculated by measuring the MTF using the line spread function. This objective MRTD has also been compared with conventional subjective measurements.

Restoration of thermal images distorted by the atmosphere is presented. The method is based upon atmospheric modulation transfer function (MTF) analysis, both theoretical and experimental. Thermal infrared (IR) atmospheric MTF measurements carried out simultaneously in both atmospheric IR windows (3 - 5 and 8 - 12 micrometers wavelengths) are presented too. The MTFs were evaluated via point spread function (PSF) measurements, under various meteorological conditions and different signal to noise ratios (SNRs). Results are analyzed and shown to be in very good agreement with theoretical predictions.

This work focuses on characterizing the performance of various staring PtSi infrared cameras, based on estimating their spatial frequency response. Applying a modified knife edge technique, we arrive at an estimate of the edge spread function (ESF), which is used to obtain a profile through the center of the two-dimensional Modulation Transfer Function (MTF). The MTF of various cameras in the horizontal and vertical direction is measured and compared to the ideal system MTF. The influence of charge transfer efficiency (CTE) on the knife edge measurement and resulting MTF is also modeled and discussed. An estimate of the CTE can actually be obtained from the shape of the ESF in the horizontal direction. The effect of pixel fill factor on the estimated MTF in the horizontal and vertical directions is compared and explained.

Sources of photoresponse nonlinearity in charge-integrating platinum silicide photodiodes are identified. Simulation results are presented, illustrating the magnitude of this nonlinearity as a function of wavelength, initial bias voltage, and stray capacitance. Additional simulation studies are discussed, revealing the impact of photoresponse nonlinearity on slope-and-offset- corrected thermal imaging. Application charts are provided, indicating the proper choice of calibration points for platinum silicide imaging systems.

The use of focal plane arrays (FPAs) in infrared imaging systems is becoming increasingly important, but in the long wave infrared the number of detector elements in the array is limited by the current state of technology and this in turn restricts the available spatial resolution or field of view. This paper describes an image processing scheme which is able to interpolate and enhance an image in a unified moving window operation. The image is first expanded to the required size by pixel replication and then processed so that the resulting spectrum approximates to that of the original scene. A numerical method has been developed to calculate the interpolator and its use has been demonstrated in a computer simulation.

A scanning imaging system that simultaneously generates visual or near-infrared (NIR, < 2 micrometers ) and far infrared (FIR, 8 to 12 micrometers ) digitized images is described. The visible or NIR images are presentations of reflected radiation at the corresponding wavelengths. The FIR emission is calibrated with thermostated black bodies to yield a thermal image. The system was designed to produce twin images, with identical perspective and scale factor, that can be overlayed to allow unambiguous identification of the observed object and precise location of thermal features on the observed object. This system has a variety of uses, especially in clinical applications of telethermometry. The visual imaging system is designed to use the same optical scanning configuration as that which generates the thermometric data. The camera's optical scanning system is described, as are the electronics of the imaging system, including the design of the photodiode amplifier, pixel trigger generator, digitizer and the computer interface circuits. A few experimental images taken by this system are also presented.

This paper presents an algorithm used for 2-D parameters estimation, it takes into account the low amount of data provided by dedicated infrared sensors. We use fuzzy modelization to cope with reconstruction uncertainty. The concept of entropy adapted to fuzzy sets is used as a decision criterion to provide a best regularized solution for the ill-posed problem of the reconstruction of 2-D parameters.

Under certain experimental conditions a semiconductor-discharge gap structure can be used as detector for spatio-temporal resolved measurements on IR radiation. We investigate experimentally the speed properties of this kind of converter by using a streak camera system and a semiconductor laser diode ((lambda) equals 1.3 micrometers ). The experimental results are compared with the predictions of a simple theoretical model.

A kind of liquid crystal light valve (LCLV) based on a CdS-CdSe photoconductor that can convert visible image to infrared at video rate is introduced in this paper. A prototype of a visible to infrared dynamic image converting system using a CO₂ laser as the infrared source is built with this device. Results of the converter are presented in this paper.

Two-dimensional infrared focal plane array detectors in general are characterized by a significantly larger size and thermal mass than the traditional discrete element detectors. Usually, they contain an `on-board' signal processor. The size and thermal mass impact is significant in the radiation shield/cold optics subassembly. In order to achieve miniaturization, low input power and fast cool down time, a combined team of Cincinnati Electronics Corporation, Mason, Ohio and RICOR-Cryogenic and Vacuum Systems, EnHarod (IHUD), Israel are working on the development of a Miniature Integral Cooler/Dewar Assembly-IDCA specially tailored for 2-D FPA type detectors. A progress report, based on accumulated experimental data gathered through the operation of engineering models of this type in a laboratory level and in a system level under various conditions, is presented.

Lead scandium tantalate (PST) has been shown to have exceptionally good pyroelectric figures-of-merit, especially for small detectors of the type involved in the large arrays needed for uncooled solid state thermal imaging. This paper reviews the properties of PST in relation to those of other materials which have been considered for use in this role and discusses how dopants, including K/Bi, Nb, Ti and Zr, can be used to modify the properties of the material in a way which would be beneficial to certain modes of detector operation, particularly with respect to the elimination of the requirement for cooling. F_D figures-of-merit of over 20 X 10^-5Pa^-1/2 are reported. A concern for the user of devices under electrical bias is the possible change in the properties of the active material with time. This is particularly so in the case of dielectric bolometers where they are subject to high bias fields (up to 5 V micrometers ^-1) for extended periods. The results of measurements of the properties of PST after aging under such fields are presented.

Until recently, problems resulting from fires in forests and natural areas were solved on a national rather than international level. This resulted in duplicating research efforts. The Commission of the European Communities (CEC) tries to enhance the cooperation between European countries to stimulate research on the causes and the technological developments for wildfire prevention, detection, and fighting. One result of these efforts has been the start of an international project on the development of a demonstration system that will be used to aid wild land managers and fire fighters in preventing and fighting wild fires. The system will consist of a decision support system and an autonomous wild fire detection system. The basic information that is used by the decision support system is on the one hand a database system with historical, topographical, logistic, meteorological and geographic information and on the other hand `real-time' data from automated cameras and weather sensors. Also, in other large countries outside Europe, such as Canada, the United States and Australia, technological approaches are being developed to reduce hazards as a result of wild fires. In this paper a summary is given on the various problems and solutions in the area of autonomous wild fire detection and surveillance in the CEC and some other parts of the world.

Infrared sensing systems are nothing new. They have been in operation in military applications for decades. The unsolved challenge is to develop a tactical system for target designation -- high sensitivity, low false alarm rate, lightweight and cost competitive.