Proceedings Volume 2744

Infrared Technology and Applications XXII

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Proceedings Volume 2744

Infrared Technology and Applications XXII

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Volume Details

Date Published: 27 June 1996
Contents: 10 Sessions, 76 Papers, 0 Presentations
Conference: Aerospace/Defense Sensing and Controls 1996
Volume Number: 2744

Table of Contents

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Table of Contents

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  • Japanese Detectors and Applications
  • Advanced IR Technologies
  • IR Line Scanners
  • Space-Related Technologies
  • Thermal Imagers and Their Technologies
  • Infrared-Seeker-Related Issues
  • Infrared Technology in the UK: a 10-year Update
  • Infrared Systems in the UK: a 10-year update
  • Civilian Applications of IR Technology
  • IR Technology and Application in JPL Systems
  • Thermal Imagers and Their Technologies
  • Space-Related Technologies
  • Thermal Imagers and Their Technologies
  • Space-Related Technologies
Japanese Detectors and Applications
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Performance improvement of HgCdTe photoconductive detectors
Masahiko Sano, Keiji Miyamoto, Naoki Oda, et al.
Highly sensitive HgCdTe infrared photoconductive detectors have been developed for detecting 5 - 8 micrometer wavelength band. HgCdTe crystals were grown with the solid state recrystallization method and Cd composition was adjusted to 23.5%. The detectors possess an optical mask and asymmetric electrodes. The responsivity of the detectors depends on bias current direction. Higher responsivity was obtained with bias current flowing from a wide electrode to a narrow one. This responsivity value is 5 to 10 times larger than that of a standard detector which has symmetric electrodes and no optical mask. One of the new highly sensitive detectors was installed in a thermal imaging system and was found to be applicable to non-destructive diagnoses of buildings.
Direct MOVPE growth of HgCdTe on Si substrates for long-wavelength infrared photodiodes
Kenji Maruyama, Hiroji Ebe, Hironori Nishino, et al.
Antiphase- and twinning-free (111)B HgCdTe layers were directly grown on (100) Si substrates by metalorganic vapor phase epitaxy (MOVPE). The quality of the HgCdTe layers was evaluated for long-wavelength infrared (LWIR) photodiodes. Direct growth of (111)B CdTe on (100) Si tended to contain antiphase and twinning due to a lack of polarity in the Si crystal structure. To polarize the nonpolar Si surface, we adsorbed polar molecules on Si surface with metalorganic tellurium (Te). A metalorganic tellurium adsorption and annealing technique is effective for growing high quality CdTe buffer layers on Si substrates. This technique eliminates antiphase domains and prevents twinning. The crystallinity of the Hg1-xCdxTe (x equals 0.22 to 0.24) layers grown on Si was evaluated. We have achieved 119 arc sec. full width at half maximum (FWHM) by x-ray analysis and 1.5 multiplied by 106 cm-2 etch pit density (EPD) for a 17-micrometer-thick layer. LWIR photodiodes were fabricated from the p-type (111)B HgCdTe layers on (100) Si substrates using planer technology. The n-type regions, formed by boron ion implantation, were 50 micrometer by 75 micrometer by design. A quantum efficiency of 42% was obtained at a cutoff wavelength of 9.0 micrometer at 78 K. The zero bias resistance-area product (R0A) was 8.9 multiplied by 101 (Omega) cm2. We were able to increase the R0A and quantum efficiency with MOVPE grown HgCdTe/Si wafers by 50% of those obtained with liquid phase epitaxy (LPE) grown HgCdTe/CdZnTe.
410K pixel PtSi Schottky-barrier infrared CCD image sensor
Masahiro Shoda, Keiichi Akagawa, Tsuneyuki Kazama
We developed an 811 by 508-element monolithic focal plane array detector using a PtSi Schottky-barrier photodiode, which has the greatest number of pixels for the Standard TV format. This detector array uses an interlined CCD configuration and 1.0-micron design rules. The pixel size of this detector was 18 by 21 microns square. From many experiments, the process conditions needed for obtaining the high responsivity were determined. To obtain high responsivity, we focused on two important aspects. The first one was an effective fill factor, and the second one was the properties of the PtSi Schottky barrier. Applying the new procedure to the wafer fabrication process, we reduced the nonactive portion of the pixel and obtained the ideal optical cavity structure. This new procedure was also a damage-free process, so good PtSi Schottky-barrier properties were obtained, which is related to the second aspect. We investigated the dependence of Schottky-barrier height on Pt deposition substrate temperature. Based on the results of the investigation, typical (Phi) b (Schottky- barrier height) and typical C1 (quantum efficiency coefficient) of 0.22 eV and 0.28/eV, respectively, were obtained. The NETD (noise equivalent temperature difference), calculated as the ratio of noise to response, was 0.06 K. The responsivity nonuniformity was estimated to be 0.45%. These measurements were done for a scene temperature of 300 K, f/1.2 cold shield, a 3 micrometer- long-wavelength pass filter, and 1/60-second integration time. Excellent thermal imaging was obtained without uniformity correction. We also show that the combination of electrical shutter operation and ND filter is suitable for high-temperature measurement.
PtSi FPA with improved CSD operation
Tadashi Shiraishi, Hirofumi Yagi, Kazuyo Endo, et al.
Over the past ten years we have been developing PtSi focal plane arrays (FPAs) using the charge sweep device (CSD). FPAs are going to high resolution and the power of the FPAs are on an upward trend. Now we have developed a low-power CMOS CSD scanner (LOCCS) for a high resolution FPA. The conventional CSD scanner operates at the same frequency as that of the horizontal CCD to prevent fixed pattern noise (FPN), and generates a frequency pulse higher than the minimum requirement. The LOCCS is a kind of CMOS dynamic shift resistor, which generates clock pulses for vertical signal transfer without the low frequency input pulses that cause FPN. Because the LOCCS generates multi-phase clock pulses, the power consumption can be reduced. We have fabricated test devices to evaluate the improved CSD operation by the LOCCS, and confirmed that the devices operate normally and the reduction of power consumption is in good agreement with the theory. We also applied the LOCCS to a 256 by 256 PtSi FPA and obtained thermal images.
Antenna-coupled thin-film far-infrared radiation detectors
Yoshizumi Yasuoka, Hiroaki Kobayashi, Takashi Shimizu
The 4 slot array antenna for 700 GHz far-infrared radiation are fabricated on the fused quartz substrates, making use of the dimensions obtained from the model experiments in the microwave region, and the power gain and directivity are obtained experimentally. The properties of fabricated array antenna agree with the theory, and 4 slot array antenna on the substrate of which thickness is odd multiples of a quarter dielectric wavelength improve the power gain by 5 dB compared with the single slot antenna on both sides of air and dielectric. These experimental data indicate that the fabricated antennas show the antenna pattern expected from the theory and work as array antennas for 700 GHz far- infrared laser radiation.
Performance of new handheld IR camera using uncooled bolometer FPA
Takanori Sone, Norio Ohkawa, Yasuo Kawashima, et al.
A camera using an uncooled infrared image sensor has been developed. This image sensor is a bolometer focal plane array (FPA), of which the readout circuit is designed to minimize the temperature drift or the pattern noise caused by the changes of the ambient temperature. The circuit has a bolometer for the load resistor, which has the same temperature coefficient of resistance as that of the pixel bolometer. Therefore the signal change induced by the temperature change of the FPA substrate is reduced because the resistance change of the load bolometer compensates for that of the pixel bolometer. The effectiveness of the drift- compensating circuit has been confirmed with a prototype handheld camera.
Simulation of visible/infrared sensor images
Tomohiro Akiyama, Yasuhisa Tamagawa, Takayuki Yanagisawa
For developing an imaging system, a computer based imaging simulator that predicts the performance of the system is desired. The simulator synthesizes images by various sensors under a wide variety of field conditions in the early design stage. The advantages of eliminating unnecessary trial manufacturing and field testing under severe environmental conditions are given herewith. In the simulator described in this paper, spectral radiance of an object is assumed as being the sum of the reflection of solar irradiance and sky radiance and the emission obtained from the emissivity and temperature of an object. Wavelength bands are selected from the visible to the far-infrared wavelength region. Spatial resolution, noise, shading, ghosts, narcissus and mechanical vibration of the optical components are considered to be image degradations by the use of sensors. This paper describes the simulation procedure and illustrates synthesized images with several objects and scenarios such as wavelength band, atmospheric conditions and degradations by the use of sensors. These images show that the presented simulator is effective in determining the specifications of a desired system.
Flight performance of the Infrared Telescope in Space (IRTS)
Hiroshi Murakami, Hiroshi Shibai, Takashi Onaka, et al.
The Infrared Telescope in Space (IRTS) is a cryogenically cooled 15 cm telescope on board the Space Flyer Unit (SFU), a small space platform. The SFU was launched in March 1995 by Japanese H-2 rocket and retrieved by NASA's Space Shuttle in January 1996 after successful execution of the mission. The IRTS has performed an infrared sky survey successfully in the wavelength range from 1.4 micrometer to 700 micrometer. About 7% of the entire sky has been surveyed. The cryogenic system of the IRTS held the telescope and the focal plane instruments at a stable temperature of 1.9 K for more than one month. The infrared sensors worked well, although remarkable radiation effects were observed especially at the South Atlantic Anomaly. We need further analysis to clean these radiation effects, but the obtained data will give important scientific information on the interstellar matter, extragalactic background light.
Infrared Imaging Surveyor (IRIS) project
Hiroshi Shibai, Hiroshi Murakami
In this paper we describe the concept and the design of the InfraRed Imaging Surveyor (IRIS), the first Japanese satellite solely dedicated to infrared astronomy. It will follow a successful precursor, the Infrared Telescope in Space (IRTS) onboard the Space Flyer Et (SFU) in 1995. The IRIS has a 70 cm telescope cooled down to 7 K by using superfluid helium assisted by two-state Stirling cycle coolers. The expected hold time of the super-fluid helium is one year. After consumption of the helium, near-infrared observation can be continued by using the mechanical coolers. Two focal plane instruments are planned; the infrared camera (IRC) and the far-infrared surveyor (FIS). The total spectral coverage is 2 to 200 microns. The major scientific objectives are to investigate birth and evolution of galaxies in the early universe by survey of young normal galaxies and starburst galaxies. The orbit is a sun- synchronous orbit, in which the cooled telescope can avoid huge emissions from the Sun and the Earth by pointing the telescope on the great circle perpendicular to the Sun. The IRIS project is expected to start in 1997 and it will be launched by a M-V rocket in 2002.
PtSi infrared camera for astronomical observations
Munetaka Ueno
The PtSi IR CSD was evaluated for astronomical purposes. The device has enough potential to apply for the astronomical uses. Several collaborations are being promoted with the camera. The infrared cameras are reopening infrared windows to the universe since they realize very efficient observations. The appearance of the infrared camera is one of the biggest breakthroughs in the astronomical instrument like that of the photographic plate. The collaboration of the infrared camera is very important both in science and scientific activity of the countries where the camera is not available because of less efficiency of the conventional infrared instrument. The PtSi camera projects under collaboration with Mitsubishi Electric Co. are summarized in this paper.
Evaluation of the 1040x1040 PtSi CSD for astronomical use
We present the performance of the 1040 by 1040 PtSi CSD manufactured by Mitsubishi Electric Co. for an application of astronomical imaging. The sensor was evaluated both in laboratory and in real observing conditions. The results of noise, quantum efficiency, linearity, dark current and photometric accuracy are presented.
Astronomical wide-field imaging with the Mitsubishi PtSi 1040x1040 CSD
A new infrared camera equipped with a 1040 by 1040 PtSi CSD array is in operation as a common-use instrument at Kiso Observatory of the University of Tokyo. The camera attached to the prime focus (F/3.1) of the 105 cm Schmidt telescope gives a field of view of 18'.4 by 18'.4 with a spatial resolution f 1'.1 per pixel. The image resolution, detection limit, and other performances in an astronomical application are presented. Based on the observations of nearby galaxies and Galactic objects, we demonstrate that the camera is very powerful for wide-field imaging in astronomy.
PANIC (PtSi Astronomical Near-Infrared Camera) in South Africa and its astronomical applications
Toshihiko Tanabe, Shinji Nishida, Yoshikazu Nakada, et al.
A large-format PtSi array (effectively 1040 by 520 pixels) has been incorporated into an astronomical infrared camera (named PANIC: PtSi astronomical near-infrared camera) intended for wide-field survey work using the 0.75-m telescope at Sutherland and the 0.4-m one at Capetown. Here we briefly describe our camera and its astronomical applications.
K-band imaging observations of the collision of Comet P/Shoemaker-Levy 9 and Jupiter
Kazuhiro Sekiguchi, Ian S. Glass
We present results of K (2.2 micrometer)-band imaging observations of the collision of Comet P/Shoemaker-Levy 9 and Jupiter obtaind using PANIC (PtSi astronomical near- infrared camera) on the 0.75-m telescope at the South African Astronomical Observatory, Sutherland. Time resolved (30 sec and 10 sec interval) observations of the impacts by 8 fragments (A, E, H, P2, Q1, Q2, S and T) were analyzed and K-band light curves of the impacts A, E, H, Q1 and S were constructed.
Advanced IR Technologies
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MBE flexible manufacturing for HgCdTe focal plane arrays
J. David Benson, John H. Dinan, James R. Waterman, et al.
To achieve the DoD objective of low cost high performance infrared focal plane arrays a manufacturing technique is required which is intrinsically flexible with respect to device configuration and cutoff wavelength and easily scaleable with respect to volume requirements. The approach adopted is to fully develop the technology of molecular beam epitaxy (MBE) to a level where detector array wafers with a variety of configurations can be fabricated with first pass success at a reduced cost. As a vapor phase process, MBE lends itself directly to: (1) the inclusion of real-time monitoring and process control, (2) a single or multiple wafer growth mode, (3) nearly instantaneous changes in growth parameters. A team has been assembled to carry out the program. It is composed of four industrial organizations -- Rockwell International, Hughes Aircraft Company, Texas Instruments, and Lockheed-Martin, and a university -- Georgia Tech Research Institute. Since team members are committed suppliers and users of IRFPAs, technology transfer among team members is accomplished in real-time. The technical approach has been focused on optimizing the processes necessary to fabricate p-on-n HgCdTe double layer heterostructure focal plane arrays, reducing process variance, and on documenting flexibility with respect to cutoff wavelength. Two device structures have been investigated and fabricated -- a 480 by 4 and a 128 by 128.
Range-gated active-imaging system for search-and-rescue and surveillance operations
Deni Bonnier, Vincent Larochelle
Search and rescue (SAR) and general surveillance missions pose a number of challenges to imaging system. These systems must work often in low-light level, low-visibility conditions to find and identify targets. A new airborne payload has been developed to overcome several deficiencies encountered with conventional or low-light level cameras as well as thermal imaging sensors. The recent developments in laser diode arrays, laser diode beam collimation and gatable micro-channel plate intensifier have made it possible to build a compact active imaging system. This Airborne Laser Based Enhanced Detection and Observation System (ALBEDOS) is particularly efficient at night and in degraded weather conditions. ALBEDOS is based on a powerful laser diode array illuminator and a range-gated low-light-level TV camera. Therefore, it is immune to the blooming effect specific to highly sensitive cameras and eliminates most of the light backscatter caused by the presence of aerosols. It was proven to detect small retroreflective tapes over many kilometers. In October 1995, the system was installed on a Bell 412 helicopter and tested in various scenarios.
Overview of recent advances in passive millimeter-wave imaging in the UK
Alan H. Lettington, Qi He Hong, Andrew Dean, et al.
Passive millimeter wave (MMW) imaging systems have attracted an increasing interest over the past years due to their superior poor weather performance compared with visible and infrared (IR) systems. In the UK the Defence Research Agency Malvern developed its first MMW radiometers in the late 1950s. These systems were bulky and had poor spatial resolution and low thermal sensitivity, but the considerable advances in semiconductor solid state devices have allowed the size and weight of images to be reduced. Advantage can also be taken of sophisticated on-line signal processing and of complex theoretical modeling and analysis. This paper examines the impact of these advances of technology and to identify new methods to overcome the usual difficulties of poor spatial resolution and slow response time. High quality images are presented to demonstrate the potential of this emerging technology.
Uniformity compensation for high-quantum-efficiency focal plane arrays
Stephen Roger Horman, Kenneth C. Hepfer, Matthew W. Zurasky
NSWCDD has developed a new nonuniformity correction (NUC) technique that promises to significantly reduce both fixed pattern and temporal noise in sensors using high quantum efficiency (QE) infrared (IR) staring focal plane arrays (FPA). Sensors using this technique will also have good response in every pixel. There will be no dead or anomalously noisy pixels anywhere in the field of view (FOV). This technique will also enable development of sensors with very small apertures as well as those which can dynamically trade off sensitivity, resolution and frame rate. In addition, effective yield of detector production will be enhanced, since these benefits can be obtained using arrays that would be rejected for most applications, were conventional NUC used. This technique has been demonstrated to work as claimed through non-real time post-processing of field data. A high performance, concept demonstration sensor, is being developed, with delivery planned for August 1996.
Fusion of optical, infrared, and radar imagery for coastal surveillance
Melanie Dutkiewicz, Michael Davenport, Maria T. Rey, et al.
Imaging instruments such as optical, infrared and radar sensors can provide valuable input for monitoring coastal waters. We show how the data obtained from these three sensor types can be useful for coastal surveillance, in particular for ship detection and identification. The paper addresses various aspects of the data fusion process as applied to these sensors, including data alignment, target detection, and target feature (attribute) extraction for target identification.
Active-matrix liquid crystal display (AMLCD): an important component in next-generation imaging systems
Ray Leerentveld, John C. Wright
The AMLCD has proven to be the flat-panel display technology of choice for a wide range of commercial, industrial and military applications. Its excellent visual qualities, structural resilience/compactness and broad environmental performance have contributed to its acceptance and make it a natural selection for next-generation portable/mobile imaging systems. This paper outlines the underlying technology, expands upon its operational merits and discusses important opto-electronic and electronic considerations required to extract optimal performance from this class and kind of display in this mode of operation.
Compact infrared zoom lens for the 3- to 5-um spectral band
R. Barry Johnson, Allen Mann, Patrick J. Reardon, et al.
The results of a comprehensive design study for the development of a compact infrared zoom lens suitable for use in guided munitions are discussed. The continuously variable zoom of the lens offers significant operational performance benefits to weapon systems using fixed or switchable FOV optics. Two practical zoom lens systems were designed that showed potential to meet typical guided munitions system requirements by utilizing in the first system conventional surfaces and a combination of conventional and diffractive surfaces in the second system. Significant weight savings, enhanced optical performance, and excellent athermalization over conventional lenses were realized. The optical performance over the entire 4:1 zoom range and 5-20 degrees field-of-view is near-diffraction limit while maintaining a constant F-number.
Current status of quantum well focal plane arrays
William A. Beck, Thomas S. Faska
The state of the art in quantum well infrared photodetectors (QWIPs) is reviewed, with emphasis on the current status of QWIP focal plane arrays (FPAs). These FPAs are progressing rapidly in size from 256 by 256 to 640 by 480 pixels, and typically have temporal and spatial noise below 20 mK when operated up to 77 K in an f/1.7 camera system. Frames from videotapes recorded with recent FPAs are presented.
IR Line Scanners
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IRLS: basic design and future challenges
William L. McCracken
Infrared line scanners (IRLS) are a powerful means of gathering very large amounts of pictorial and spectral information from airborne and space platforms. Types of line scanners are reviewed and some of their more important applications are noted ranging from the ultra-violet to the 7.5 to 14 micrometer spectral bands. Prior to detail design a thorough system requirements analysis and tradeoff study is recommended to assure that the IRLS will meet the objectives of its military, commercial or scientific mission. This process is outlined for a low altitude penetration reconnaissance mission using the 7.5 to 14 micrometer IR band. Detail IRLS design is outlined and the most important system equations are discussed, including NER (noise equivalent radiance), NETD (noise equivalent temperature difference), MRTD (minimum resolvable temperature difference) and MTF (modulation transfer function). Tradeoffs involved in data processing and display to end users are noted. Future challenges include sensor fusion, size and cost reduction with improved spatial and thermal resolution. Both present and new IRLS designs will play important roles well into the next century.
Deploying the Honeywell Scanner Receiver Unit
Graham Pye, Werner Hansli, Curtis A. Vock
The scanner receiver unit (SRU) is an infrared line scanner developed for the German Airforce Electronic Combat and Reconnaissance (ECR) Tornado. Its unique, variably sampled sensor array provides horizon-to-horizon coverage without bow tie distortion, normally associated with line scanners at long slant ranges, thus obviating the need for supplementary sensors. A serial input enables an external processor to calculate and provide a number of 'mapping' parameters. These effectively steer the SRU, determining where and how many samples are to be taken within the scanned field of view. This programmable field of view feature enables a standoff capability for heavily defended areas such as airfields. Now in service with the German Airforce, SRU acceptance was not without teething problems, all of which have been rectified. While the effects were not directly associated with the SRU itself, the solutions were applied to the SRU to assure compatibility within different systems; the main improvement being the incorporation of a correction signal derived from the spin mirror and coupled into the sampling clock to eliminate image break up caused by variations in spin mirror rotation due to external influences. In the infrared imaging system developed for the ECR Tornado, the SRU is coupled to a recorder using dry silver film, which provides for on board development and viewing. Honeywell is now in the final phase of developing a highly integrated Reconnaissance Management Unit for the German Airforce Reconnaissance Program, to facilitate use of digital tape recorder technology. This development will extend the SRU's capabilities and ensure its use into the next century.
Infrared line scanner that digitally corrects for bow-tie distortions
Raymond J. Silva, William Shaw, Kurt Nordhaus
This paper describes the infrared line scanner (IRLS) developed by Loral Infrared & Imaging Systems for the Advanced Tactical Air Reconnaissance System (ATARS). Features include very wide fields of view, up to 140 degrees in wide mode; high resolution in the 8 - 14 micrometer band; and the ability to collect contiguous ground imagery at velocity to height (V/H) ratios of up to 5 rad per second. In real terms, a V/H ratio of five equates to an aircraft altitude of 200 feet at speeds approaching Mach 1. The ATARS IRLS is an evolution of the AN/AAD-5 and D-500 line scanners that provides several key improvements over its predecessors. Imagery is exported in digital format allowing for real time imagery exploitation. Additionally, by using some novel system approaches that combined the elements of receiver optics, detector geometry, and electronic signal processing, output data rates were held at tolerable levels. The combination of these techniques results in a system that is optimized for best ground area coverage with a minimum number of detector channels. As a consequence the bow-tie effect at the edges of the field of view has been virtually eliminated while simultaneously reducing data storage requirements.
Space-Related Technologies
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Space-based multisensor multispectra nonstationary image analysis
George A. Lampropoulos, James F. Boulter
A method to compose multi-sensor multi-spectra images is presented in this paper. In addition, a method that can estimate the motion of small targets between two frames of the same spectra band also is shown. Objects which were not present in one frame are automatically detected by utilizing this technique. For the composite multi-sensor and/or multi- spectra images, the Karhunen-Loeve (K-L) and Gram-Schmidt (G-S) orthogonalization techniques are used in combination with our blur estimation and 3-D restoration methods. For the motion estimation or target detection in a set of two frames of the same spectral band, the G-S orthogonalization is used. Results procured from real data of satellite images will be offered fittingly in this presentation.
Thermal Imagers and Their Technologies
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640x480 PtSi infrared engine
Frank B. Lang, Peter J. Coyle, Paul J. Stabile, et al.
The design and performance of a compact, light-weight, low power infrared engine is presented. The 3 - 5 micron MWIR imaging subsystem consists of a Stirling-cooled, 640 (H) by 480 (V) staring PtSi infrared focal plane array (IRFPA) with associated drive and analog video processing electronics. The IR engine provides user-selectable integration time control. This infrared imaging subsystem is designed to be gimbal-mounted, and has been qualified to be operated in minus 10 Celsius to plus 50 Celsius environments. The infrared engine is also designed to meet the requirements of demanding shock and vibration environments.
Ultrareliable pulse tube cryocooler with a flexure-bearing linear- drive compressor
Patrick Curlier
The requirements for ultrareliable miniature cryocoolers with affordable price is growing up for the military, space and commercial Infrared applications. For surveillance application operating 24 hours around the clock, a MTTF in the range of 20 000 hours is targeted today by the potential users. To reach this goal, a technical breakthrough is necessary and a combination of an ultrareliable linear drive compressor based on flexure bearings and a Pulse Tube coldfinger is proposed. The progress on miniature pulse tube and the development status of the compressor assembly is presented. Keywords: Ultrareliable cryocooler Pulse Tube, flexure bearings, affordable price.
IRNG-camera family
Michael Dupiech, Pierre M. Marche
Further to the development of the SYNERGI set of modules dedicated to new generation multipurpose high performance thermal cameras based on the SOFRADIR 288 by 4 element IRCCD detector, THOMSON-CSF OPTRONIQUE have decided to extend the family of second generation cameras with the development of SOPHIE. SOPHIE is a handheld infra-red camera, also organized around the 288 by 4 element detector, corresponding to a different cost/performance trade-off. It is an ultralow-cost, ultralight, medium range imager designed for passive observation and surveillance. It exhibits growth potential such as low cost infra-red sights for light armored vehicles firing posts.
High-performance IR cameras
Yifal Jeff Shaham, R. Schellhase
Aerojet has developed high performance infrared (IR) cameras based on Kodak's 640 by 486 pixels platinum silicide (PtSi) array. Several versions of the camera have been developed for the various applications. The cameras have multiple field-of-view (FOV) optics, with the narrow FOV used for long range observation. The use of the large array of PtSi leads to very high image quality as well as high resolution. The operation in the medium-wavelength infrared (MWIR) allows observation at very long ranges in high humidity, warm atmospheres. Field tests have shown the advantage of these cameras, particularly in coastal and marine applications.
Thermal imagers based on MCT LWIR staring FPAs: design review and achieved performances
CEDIP is the first company to produce commercially available LWIR cameras using HgCdTe (MCT) staring arrays. This range of thermal imagers is available in various configurations including split Stirling cooler and integrated micro machine coolers. The design of thermal imagers with this technology requires advanced signal and image processing in order to correct for array non-uniformities, thermal drift and to display the highest quality images. This paper focuses on some of the technical solutions used inside the camera such as the proprietary DSP electronic board which controls in real time the image quality parameters as well as the optical solutions and lens arrangements which provide sharp and clear images. Experimental data and obtained performances are presented and discussed.
Derivation of an optomechanical tolerance budget for a bistatic sensor pod
Pointing errors can compromise the performance of laser systems and cause numerous operational problems. In this paper, alignment tolerances for a bistatic sensor pod are derived from first principles. The method applies to a sizeable class of problems but is particularly relevant to military applications like laser target designation and rangefinding. It yields exact or conservative estimates in most cases of practical interest. Various results are explored from the point-of-view of employment methods and military deployment.
Stabilized FLIR for long-range airborne surveillance
R. Lawrence Sinclair, Steve Tritchew
In this paper, the design and performance of an airborne long range thermal imaging system, operating in the 3 - 5 micrometer spectral band, is described. Comparisons of predicted and measured performance are provided. The system, which contains a dual field-of-view telescope, is stabilized to better than 5 microradians rms jitter and provides high quality thermal images with a spatial frequency resolution greater than 8 cycles per mradian.
Infrared-Seeker-Related Issues
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High-performance MCT LWIR and MWIR staring array for high-frame-rate applications
Philippe M. Tribolet, Valery Compain, Raymond Boch
There is a great demand for staring arrays adapted to high frame rate applications. These applications cover military fields (seekers for example) and also commercial fields for process monitoring or surveillance. To answer this need MCT staring arrays offer a very wide range of possibilities covering different wavebands from MWIR to LWIR and operating at rather high FPA temperatures. In this paper some trade- offs between different parameters of a MCT staring array are proposed for typical applications such as a seeker and a surveillance system.
New developments in small cryocoolers
Alain Cottereau, Marc Ben David
An overview of the new developments in small cryocoolers at L'Air Liquide-DTA is presented. The results of a pulse tube refrigerator developed in collaboration with l'Ecole Normale Superieure, the first French laboratory which worked on this subject, are discussed. An original two flowrate flat Joule- Thomson cooler is extensively described. This last development shows the historic willingness of L'Air Liquide- DTA to be present in demand flow cryostat and fast cool-down systems for defense programs.
Real-time thermal infrared scene-generation technology and its application in the test and calibration of infrared sensors and seekers for laboratory and field environments
R. Barry Johnson, Ronald Chung, Michael Gaitan
For more than two decades, researchers have investigated a wide variety of technologies for use as a real-time infrared scene generator. During the past several years, the most promising technology to meet the myriad of applications appears to be the silicon micromachined resistive-array approach. Each thermal pixel is created by a micro-scale resistor. The present investigation reports the recent results achieved by using the standard commercial CMOS foundry process, rather than a costly custom fabrication process, to produce the chip and the subsequent post-foundry etching. Both chip-level and pixel-specific electronics are readily included on the chip since IC technology is employed. The principles used in device architecture formulation, chip design, and fabrication of large arrays of these thermal pixels are discussed along with experimental results of recent array designs. The application of this technology in the development of a low-cost, real-time infrared test set for field evaluation of infrared sensors and seekers is presented to illustrate that low-cost, high- performance flat-panel thermal infrared displays are now viable and practicable.
SHIPIR/NTCS: a naval ship infrared signature countermeasure and threat engagement simulator
David A. Vaitekunas, Karim Alexan, Owen E. Lawrence, et al.
An integrated naval infrared target, countermeasure and threat model is presented. The target modeling capabilities include complex 3-D surface geometries, a thermal system model with auto-generated solar heating, sea/air convection, sea/sky radiation and inter-surface radiation, a surface radiance model which accounts for multiple diffuse reflections, observer-to-target atmospheric absorption and path radiance, and an exhaust gas dispersion and IR emission model. The IR images of any number of targets can be rendered simultaneously within a full-hemispherical sea/sky/sun background relative to an observer at a specified altitude, based on the atmospheric radiance, solar irradiance, path radiance and time-average solar sea-glint. Flare countermeasures are added to the scenario through definition of canisters, submunitions, burn characteristics and deployment tactics. The IR missile model has been constructed from a minimum number of parameters to keep the model generic and provide a reasonable estimate of IR susceptibility. The purpose of the model is to provide the tools necessary to develop and assess the effectiveness of infrared signature suppression and infrared countermeasures. A number of analysis methods are provided, including on- screen image analysis, polar signature plots, polar lock-on range and engagement simulation.
Automatic air-to-ground target recognition using LWIR FPAs
Jean-Louis Amadieu, Vincent Fraysse
The theoretical potential of optical sensors in terms of geometrical resolution makes them the ideal solution for achieving the terminal precision guidance of today's missiles. This paper describes such a sensor, working in the 8 to 12 micrometer spectral domain by using a 64 by 64 IRCCD focal plane array, and whose main mission is to recognize various types of armored vehicles within complex scenes that possibly include other vehicles of similar nature. The target recognition process is based upon a Bayesian approach and can be briefly described as follows: after a classical processing stage that performs the filtering and the multi- thresholding, the target recognition algorithm evaluates a similarity level between the objects, including the target, seen in the IR scene and the 'theoretical' target whose some mean, generic features have been implemented in a database. The surroundings of the target and its orientation in the IR scene are 'a priori' unknown. The similarity level is based on calculation of the Mahalanobis distance between the object features vector and the mean features vector of the model; this calculation involves a covariance matrix which is significant of the errors affecting the measured features and that in particular stem form the limited spatial resolution of the sensor, the detector noise and the sensor- to-target range estimation error. With respect to the sensor hardware, its main opto-mechanical characteristics as well as some electro-optics data are indicates; some examples of target acquisition in complex scenes involving different kinds of IR counter measures are also presented.
Improved reticle seeker using the segmented focal plane array
HyunKi Hong, Sung-Hyun Han, Jong Soo Choi
Reticle seekers temporally modulate target location onto the incoming spatial signal. When large or multiple targets are present in the FOV, however, it is hard to precisely modulate the incoming target signal by the reticle. To solve this loss of modulation depth problem, we present an improved reticle seeker using the segmented focal plane array (FPA). The new reticle system uses the normalized difference as well as the modulated signal of each detector output in the segmented FPA. In simulation, we have ascertained the proposed system can make an effective analysis and tracking for multiple or large targets.
New technique for noisy target discrimination
Arezki Halet, George A. Lampropoulos, Tue Huynh
A new linear discriminant technique that results in better classification performance over existing techniques is presented in this paper. This new approach is formulated in a similar manner to that of the Fisher linear discriminant. However, the matrix which corresponds to within classes has been replaced by a new matrix. This matrix takes into consideration the cross-correlation properties of the classes of interest. It has been shown through simulations that this matrix replacement results in a better classification performance over other linear discrimination methods, including the Fisher discriminant. Finally, the proposed new discriminant is presented in parametric and non-parametric forms, and is found to exhibit better classification in both cases over other parametric and non- parametric methods, respectively. With this new approach, the non-parametric method will prove to be more successful than its parametric counterpart.
Infrared Technology in the UK: a 10-year Update
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Advanced heterostructures for In1-xAlxSb and Hg1-xCdxTe detectors and emitters
Multilayer, epitaxial, heterostructure devices have been fabricated in In1-xAlxSb by molecular beam epitaxy and in Hg1-xCdxTe by metallo-organic vapor phase epitaxy. The principal motivation was to produce devices which will operate with little or no cooling. Results are presented for InSb and MCT diode detectors operating in both equilibrium and non-equilibrium modes at ambient and near ambient temperatures. An uncooled MCT detector has demonstrated near shot-noise limited detection of carbon- dioxide laser radiation in a heterodyne receiver. Uncooled, light-emitting diodes have demonstrated useful power outputs in both positive and negative luminescence at wavelengths out to 11 micrometers. A diode injection laser has been demonstrated in InSb giving an output at 5.1 micrometer and 90 K.
CMOS/HgCdTe 2D array technology for staring systems
Ian M. Baker, Graham J. Crimes, Roger A. Lockett, et al.
This paper describes the technology used for large, medium wavelength infrared arrays based on HgCdTe/CMOS hybrids. Such arrays are being produced for lightweight imagers and for space applications at wavelengths from 2.5 to 7.0 micrometers. The paper concentrates on a detector for the EUCLID CEPA 8 program. This is a 384 by 288 staring HgCdTe infrared array designed for the 3 - 5 micrometer band. The use of HgCdTe enables operation at temperatures up to 140 K and provides sensitivities (NETDs) around 17 to 20 mK. The array has a 20 micrometer pixel to minimize the size and cost of the focal plane subcomponents. The silicon architecture uses alternate stare and scan, or so-called blinking mode, so that the array can be used with microscan. The aim is to produce full PAL-TV resolution (768 by 576) when the four frames are combined. The benefits to the overall system of a small image diagonal (9.6 mm), a relatively high operating temperature (for low cooler power) and the low power consumption of CMOS technology are assessed during the program. The EUCLID dewar designed by Alenia is a purpose built encapsulation that offers some unique features over existing products. It has small physical size, low weight and low intrinsic heat load (50 mW). The dewar is designed for low cost and is fully integrated with the engine. The benefits in future of newer heterojunction detector technology to increase the operating temperature and further reduce cooler power and cool-down time are described.
CMOS/CdHgTe hybrid technology for long-linear arrays with time delay and integration and element deselection
C. P. Arthurs, Ian M. Baker, Graham J. Crimes, et al.
This paper discusses the technology used by GMIRL for high performance long linear arrays based on CdHgTe/CMOS hybrid multiplexers. Modern silicon processes allow the realization of a high degree of functionality within focal plane detectors. GMIRL have used this enhanced functionality to facilitate the deselection of defective elements within a diode array and provide time delay and integration. Two design approaches have been evaluated leading to the design and manufacture of high performance arrays for imaging applications. The resulting detector allows the enhancement of the signal to noise ratio at low IR flux levels and has a low overall power consumption, while requiring the minimum of real time correction for nonuniformities. The design can be readily adapted to suit arrays of varying length. The infrared sensor technology is based on CdHgTe (CMT) material grown by a tellurium rich, liquid phase epitaxy (LPE) process. Lateral collection photodiode arrays are fabricated within this material as a silicon CMT hybrid structure.
Uncooled IR imaging: hybrid and integrated bolometer arrays
Rex Watton, Paul Antony Manning, Michael C.J. Perkins, et al.
Uncooled, compact and low power IR imaging is offered by large arrays of bolometer elements, at a pitch of 40 micrometers to 100 micrometers. A hybrid array technology, exploiting the pyroelectric property of ferroelectric ceramic materials in the bolometer elements, has produced a range of successful linear and 2-D arrays. High merit figures for the ferroelectric ceramic have been coupled to fabrication technologies including reticulation and solder bump bonding of the elements to the readout multiplexer IC. However, other designs will compete for cost-effectiveness in the large arrays now required for security and other civil applications such as night driving aids. In particular, direct deposition of thin film ferroelectric material onto suitable thermal microstructures on the silicon readout IC could provide substantial reductions in costs and improved performance. This integration will require processes compatible with the silicon IC. Already, lead-based perovskite films are showing considerable potential but other bolometer types are also candidates, such as thin film resistance bolometers. Thermal imaging systems research has resulted in signal conditioning and processing architectures which are optimized for the bolometer arrays. The ac coupling of the ferroelectric response to the IR radiation has been exploited through the use of radiation chopping and image difference processors (IDP), which remove fixed pattern noise and limit low frequency noise. The image detail observable with the pixellated aery has been enhanced by microscan modes. The successful technology will form the basis for a rapid growth of commercial IR imaging and monitoring into the next century.
Passively athermalized hybrid objective for a far-infrared uncooled thermal imager
Andrew P. Wood, L. Lewell, Paul Antony Manning, et al.
The development of a Petzval objective lens which is passively athermalized over the temperature range minus 20 degrees Celsius to plus 50 degrees Celsius is described. The lens is compatible with a latest generation uncooled staring array imager operating in the far infrared band, currently under development at the UK Defence Research Agency (DRA). In order to minimize the number of lens components which are required, a diamond turned hybrid refractive-diffractive element is employed. Design options are presented and the manufacturing issues relating to the diffractive surface are described. The goal is to produce a cost effective solution rather than placing the emphasis on achieving the ultimate in performance. Results from optical performance tests are given, including interferometry at a range of temperatures and broadband MTF.
Aberration athermal optics for second-generation FIR thermal imagers
Don R. Barron
The new generation of FIR thermal imagers require extremely high optical image quality to fully exploit the very high sensitivity available from detector arrays of several thousands of very small elements. Earlier optical designs and builds for FIR cameras generally suffer from a change in image quality arising from the change in refractive index of germanium. This paper shows that there are optical configurations whose image quality is virtually independent of temperature. A demonstrator using these optical designs is presently under construction jointly funded by the UK DRA and Pilkington Optronics. The demonstrator will be used to assess the practical performance of a camera designed to meet the very high specifications demanded of the next generation of thermal cameras.
Target recognition, identification, and tracking using real and synthetic IR imagery
H. Tim A. Pentecost, Andrew M. Rogoyski, Douglas R. McCann, et al.
In the development of automatic target detection (ATD) and automatic target recognition/identification (ATR/I) systems, the issue of image data is commonly given inadequate consideration. All too often a poorly managed collection of real data, or unrealistic synthetic data is used during development, resulting in a loss of performance when used in the field with imagery having different characteristics. Some of the most promising approaches to ATD and ATR/I, such as neural networks, are particularly susceptible to this problem due to their direct dependence on the training data. This paper highlights the issues involved, with reference to a generic detection and classification approach and to the use of real and synthetic infra-red imagery at the Defence Research Agency at Fort Halstead in the United Kingdom.
Infrared Systems in the UK: a 10-year update
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UK fast-jet IR systems evolution: a 10-year update
Andrew J. Seedhouse
This paper is a review of IR technology and systems as developed for UK fast jet aircraft, both for experimental purposes and in-service equipment. It covers both navigation and targeting systems. The paper also discusses the way ahead, proposing new programs to take this technology well into the next century.
Firefly: a wide-field surveillance system for long-range target detection and recognition
David A. Huckridge, W. R. M. Pomeroy, M. W. Thomas, et al.
There is a widespread requirement for wide area surveillance with target detection and recognition. To achieve the above aims with a single sensor is difficult and inevitably performance compromises have to be made. A system, designated Firefly, has been developed which splits the task of surveillance/target detection from that of recognition. Firefly uses separate sensors for both tasks, each sensor can then be optimized for the role it has to perform For surveillance and target detection, Firefly makes use of a previously developed scanned thermal imager operating in the 8 - 11 micrometer waveband. There was no suitable sensor available for the recognition role and so a 3 - 5 micrometer imager based on a 2D starring array was developed for this purpose. The Firefly system is described in this paper with emphasis being given to a description of the high resolution, recognition sensor where the development effort was concentrated. Results of performance also are given.
Life-saving uncooled IR camera for use in firefighting applications
Mel V. Bennett, Iain Matthews
A recent description by a firefighter on the experience of entering a building that is on fire was to liken it to being blindfolded, then being lead to a maze and told there is a victim at the center which you have to recover. In simple terms, firefighters are totally blind and what they need are 'eyes' that can see in the dark and through dense smoke. The development of lightweight thermal cameras using uncooled IR staring arrays and a helmet mounted display has now given the firefighter the 'eyes' in such situations which means less time to achieve a rescue and enhanced personal safety for the firefighter. This paper gives details on the development of the uncooled array camera and how it's been configured to withstand the extreme temperature conditions encountered during a firefighting environment. Also, how the camera and display system have been designed to provide the firefighter with a helmet mounted configuration to enable total 'hands free' operation. This is followed by a description of the special tests required to prove that the complete system can survive in a fire environment and finally a short video which demonstrates how the system performs in real life situations.
Implementation of a second-generation long-linear imager for the high-performance application
William Douglas McGinn, Robert P. A. Booker
This paper describes the implementation of the UK long linear array infrared detector technology in a high performance second generation imaging system. The paper also explains both the background to the development 8 - 12 micrometer waveband long linear array sensor. The key components form the basis of the description; the detector, the referencing system and the selected scan system.
Submarine periscope thermal imaging: its evolution in the UK
George R. Armstrong
The first submarine periscope to carry a thermal imaging sensor started sea trials in 1978. As a leading EO company and the sole supplier of periscopes to the Royal Navy since 1917, Pilkington Optronics (Barr & Stroud) has led the evolution of this technology in the UK. As is often the case, the evolutionary path has been IR detector technology- led. The first operational periscope TI system (1981) used a serial/parallel array of first generation photoconductive detectors operating in the LWIR (8 - 12 micrometer) waveband. The advent of SPRITE detectors in the 1980s opened the way to greatly improved performance within a reduced space volume, culminating in 1993 with the entry into fleet service of the SPRITE-based IR028 modular system for Vanguard, the new class of RN ballistic submarines. Today, second generation focal plane array detectors, along with the concept of the non-hull penetrating optronics mast, are ready to revolutionize periscope TI. The Pilkington Optronics CM10 Optronics Mast, presently under development, has been bid for the next class of RN submarines, Trafalgar Batch 2. CM10 exists in two versions, allowing the user to choose the operational waveband most suited to his operational needs. The sensor in the LWIR version is the PO high definition thermal imager (HDTI), which makes optimum use of SPRITEs to achieve very high performance within a compact space. The MWIR version features dual-band (TV plus 3 - 5 micrometer) optics viewing through a single pressure window; the TI sensor is based on a microscanned CMT FPA, yielding high spatial resolution and thermal sensitivity with small aperture optics.
STAIRS C: the UK next-generation high-performance thermal-imaging system
Adrian W. Glass, Frank G. Leaver, Peter N. J. Dennis
The Defence Research Agency and Pilkington Thorn Optronics are jointly developing a generic next generation high performance thermal imaging system, known as STAIRS C. The relationship of this program to other thermal imaging programs in the UK and the evolution from first to second generation systems at Pilkington Thorn Optronics is discussed. A detailed review of the technology selection process and the key aspects which enable the STAIRS C system to satisfy the requirements for significantly enhanced target recognition and identification ranges is presented including the detector technology, optical constraints, manageable data rates, image processing and display techniques. The paper concludes with a summary of the functionality and design flexibility of the imager.
Superresolution by spatial-frequency aliasing
Alan H. Lettington, Qi He Hong, Sophie Tzimopoulou
A super-resolution scheme based on the use of a sampling grating has been proposed to extend the spatial resolution of an IR imager operating in the 8 - 14 micrometer spectral region, where there are at present technological difficulties in manufacturing large arrays of photon detectors. An intrinsic property associated with any sampling device is the aliasing effect which transfers the higher spatial frequency content of the scene down onto the lower frequency regions. While this property is regarded as a problem for many image processing algorithms, it is used in this paper as a spatial frequency encoding technique which enables all the spatial frequency information of the scene to pass through the imaging system. A new higher resolution image is then reconstructed from a series of images obtained with the grating in a series of different positions. This method is illustrated by computational and experimental simulations and is compared with super- resolution algorithms based on inverse transform techniques.
Modeling and simulation of IR scenes and sensors in the UK: current and future capabilities
A. Marshall, Kevin St. John Murphy
The Defence Research Agency at Malvern (Electronics Sector) has developed a computer model called SMARTI (simulation and modeling of array thermal imagers) which allows simulation of the effects of the various components of a focal plane array infra-red imager on a thermal scene. It can include a range of dynamic effects such as sinusoidal vibration, random jitter and linear motion, and can simulate both staring arrays and long linear arrays with TDI (time delay and integrate). The present version of SMARTI incorporates a thermal scene generator called IFS (image formation system) which can create scenes for the 3 - 5 and 8 - 14 micron wavebands. It also includes the ORACLE visual acquisition model. The Electronics Sector at Malvern is now planning to develop a real-time scene and sensor simulation facility called SORCERESS (software for realistic computer-generation of environments in real-time for evaluation of sensors and scenarios). This model will include the same functionality as the present SMARTI model, but will run on a silicon graphics reality engine at real or near-real-time speeds and thus permit a more extensive range of studies to be performed. It also will be able to create scenery for any range of wavelengths between 0.42 and 14 microns, thereby extending the scene and sensor modeling capability into the visible and near IR wavebands. This will enable the benefits of multi-sensor systems to be established.
Modeling of an IRST system
Moira I. Smith, Duncan Hickman
The development of a mathematical model of an aircraft- mounted infra-red search and track (IRST) system is reported. In addition to accurately simulating the detection, tracking and classification aspects of the IRST sensor, the model also encompasses the generation of artificial IR scenes with embedded targets, atmospheric effects, an aircraft and target dynamics model, an inertial navigation system error model and a simple weapons system simulation. External files containing modeled IR backgrounds or real recorded IR data can be accepted via a test harness as scenic input for a simulation run in order to analyze system performance during flight trials. This paper reviews the evolution of the mathematical model from IR system concepts and focuses on the techniques used to produce a performance model of a new IRST system. Design and performance aspects of a number of components within the model are described and the methodology used to achieve an accurate simulation which is both representative and efficient is also discussed.
Model to predict the probability of recognition of shapes viewed through a thermal imager
Alison M. Fairhurst, Alan H. Lettington, Kevin St. John Murphy
A computer model has been developed to predict the probability of recognition of particular shapes when viewed through a thermal imager employing either scanned or focal plane array detectors. This model is based on the results of a series of psychophysical trials during which human observers have considered over 120,000 images of shapes having a range of initial contrasts, and which have been degraded by various combinations of blurring and sampling. These computer generated images were presented to the observers in a random order and with a random degradation, using programs to select images and display them on a computer monitor. After each presentation the observer decided which was the most likely shape to represent the image displayed on the screen. The responses collected have been used to calculate the human recognition probability of each image. A correlation has been found between the probability of recognition of any specified degraded shape and the relative contrast between the image of that shape, and the image of a similarly degraded circle of the same area. The present work is related to earlier models of human detection and recognition probabilities, and has recently been extended to include the effect of contrast.
Civilian Applications of IR Technology
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Development of an urban thermal environment measurement system using a new spherical thermography technique
Koichi Asano, Akira Hoyano, Tetsushi Matsunaga
The present paper describes a newly developed thermal environment measurement system that incorporates 'spherical thermography.' Spherical thermography is a new application of conventional thermography in which the visual plane is extended to a spherical field (4(pi) sr). Spherical thermography is highly effective for performing three- dimensional (3D) analysis of the thermal environment in an urban area containing large and/or tall buildings.
New applications of the infrared CCD camera
Yasujiro Kiyota
In Japan, two dimensional IRCCD cameras such as Nikon's LAIRD 3 have been sold by various manufacturers. In addition to the staring type IR cameras, there are mechanical scanning type IR cameras which are also receiving much attention in the market. The primary applications of the IR camera market have been night-time security surveillance, non-destructive testing and/or process control in the industrial environment. In such applications, infrared radiation emitted from the observed object is seen as heat. Thus, many IR cameras have been designed to maximize the amount of IR radiation collected from an observed object. One new application for the LAIRD3 camera is to observe the spectral signature of an object over a specific spectral band in order to determine the presence and location of a specific gas. This paper described the results of using this method to detect the presence and location of methane in an observed environment.
Coregistration of multispectral imagery for spaceborne detection of incipient forest fires
Paul J. Thomas, Ran Gilad, Elise Hug
Discrimination of small wildfires by dual-wavelength imaging at high spatial resolution (10 m) must be made against a variable background (scene clutter) caused by diffuse and specular sunlight reflections and self-emission from the scene. Small fires can be readily detected at wavelengths longer than about 1400 nm in the near infrared. From a specific ground spot, the ratio of signal intensities in bands near 2400 and 3700 nm gives an 'effective temperature' that is a useful discriminant against scene clutter. Co- registration of the scene images in the two wavelength regions is important when applying the technique, particularly from a space platform where the angular size of the ground footprint is small. This paper shows that atmospheric refraction and turbulence can be ignored, while window wedge angles, lens centration errors and spectral variations in the size of the ground footprint must be dealt with by calibration or additional signal processing.
NightSight: thermal imaging for both worlds
Robert D. Stephens Jr.
Thermal imaging, once reserved almost exclusively for the military, is now becoming accessible for many new lower cost applications. By spinning-off defense technology for commercial use, while spinning back the benefits of commercial best practices, TI is drawing on the best of both worlds to give users an affordable visual advantage.
Atmospheric remote sensing with a ground-based spectrometer system
Jean-Marc Theriault, Claude Bradette, Jacques Gilbert
Recent developments in atmospheric monitoring with a ground- based FTIR spectrometer are presented. Several aspects of the inversion method for the retrieval of temperature and humidity profiles from IR emission spectra are reported. The potential of the remote sensing method is analyzed in the context of three specific applications: As an aid for predictions of atmospheric transmittances, in support to the remote detection of atmospheric pollutants (CFCs) and to the evaluation of cloud parameters.
First derivative versus absolute spectral reflectance of citrus varieties
Carlos H. Blazquez, H. N. Nigg, Lou E. Hedley, et al.
Spectral reflectance measurements from 400 to 800 nm were taken from immature and mature leaves of grapefruit ('McCarty' and 'Rio Red'), 'Minneola' tangelo, 'Satsuma' mandarin, 'Dancy' tangerine, 'Nagami' oval kumquat, and 'Valencia' sweet orange, at the Florida Citrus Arboretum, Division of Plant Industry, Winter Haven, Florida. Immature and mature leaves of 'Minneola' tangelo had greater percent reflectance in the 400 to 800 nm range than the other varieties and leaf ages measured. The slope of the citrus spectral curves in the 800 nm range was not as sharp as conventional spectrometers, but had a much higher reflectance value than those obtained with a DK-2 spectrometer. Statistical analyses of absolute spectral data yielded significant differences between mature and immature leaves and between varieties. First derivative data analyses did not yield significant differences between varieties.
Temperature of shocked materials measured with an infrared pyrometer through a window
Eric Fribourg-Blanco, Christian Remiot, Jean-Marc Mexmain, et al.
We describe an experimental measurement technique which allows us to determine the interface temperature and the emissivity of shocked sample through window material (the lithium fluoride). We determine the temperature upon the partial release pressure of the sample. The infrared radiation emitted by the sample through the window material is collected and carried out to detectors by a four core fluoride glass optical fiber. The spectral bandwidth of this fiber is 1.5 micrometer to 4 micrometer. In order to deduce the temperature from the electrical signals amplified and recorded on a numerical oscilloscope, four narrow filters are used with different spectral bandwidth. A static calibration of the detectors with a black body is performed. Different ratios between static and dynamic measurements give access to the temperature as well as to the variation law of the emissivity versus wavelength. The shock generator for the dynamic experiment is an explosive plane wave generator. The shock pressure obtained is about 50 GPa. The purpose of this experimental measurement technique is the study of materials in solid phase as well as in liquid phase. Two samples have been studied, bismuth with solid- liquid transition at about 20 GPa and copper which remains solid in our pressure range.
Development of a miniaturized integrated optical spectrometer for the infrared spectral range
Roman V. Kruzelecky, Stephane Paquet, Asoke Kumar Ghosh, et al.
A miniaturized, planar-grating optical spectrometer for the 2 to 6 micrometer range has been designed and fabricated. This has entailed development of a slab waveguide structure suitable for the infrared, a broad-band optical grating structure and fiber-based, IR input/output optics. Broad- band light is coupled into the spectrometer through a pig- tailed IR fiber and is subsequently dispersed into its spectral components and can be focused either onto a thermo- electrically (TE) cooled HgCdZnTe detector array or an IR fiber array. Integration of the optics and detector provides exceptional optical alignment and a very compact package that is suitable for various airborne and terrestrial applications.
IR Technology and Application in JPL Systems
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Planetary Integrated Camera Spectrometer (PICS): a new approach to developing a self-sequencing, integrated, multiwavelength instrument
Patricia M. Beauchamp, Robert T. Benoit, Robert H. Brown, et al.
The planetary integrated camera-spectrometer, PICS, is a highly integrated sensor system which performs the functions of three optical instruments: a near infrared (IR) spectrometer, a visible imaging camera, and an ultraviolet (UV) spectrometer. Integration serves to minimize the mass and power required to operate a complex suite of instruments, and automatically yields a comprehensive data set, optimized for correlative analysis. This approach is useful for deep space missions such as Pluto Express and will also enable Galileo/Cassini class remote observations of any object within the solar system. In our baseline concept, a single set of lightweight multiwavelength foreoptics is shared by a UV imaging spectrometer (80 spectral channels 70 - 150 nm), a two-CCD visible imaging system (shuttered in two colors 300 - 500 nm and 500 - 1000 nm), and a near-IR imaging spectrometer (256 spectral channels 1300-2600 nm). The entire structure, including its optics, is built from silicon carbide (SiC) for thermal and dimensional stability. In addition, there are no moving parts and each spectrometer covers a single octave in wavelength. A separate port is provided for measurement of a UV solar occultation and for spectral radiance calibration of the IR and visible subsystems. The integrated science that the PICS will yield meets or exceeds all of the Priority-1A science objectives, and many Priority 1-B science objectives as well, for the Pluto Express Mission. This paper provides details of the PICs instrument design, fabrication and testing, both at the sub-assembly and the instrument level. In all tests, including optical, thermal vacuum, and structural/dynamics, the PICS hardware prototype met or exceeded functional requirements.
Atmospheric Infrared Sounder (AIRS) on the Earth-Observing System: in-orbit radiometric and spectral calibration
Hartmut H. Aumann, Kenneth Overoye
The atmospheric infrared sounder (AIRS) is a high spectral resolution IR spectrometer. AIRS, together with the advanced microwave sounding unit (AMSU) and the microwave humidity sounder (MHS), is designed to meet the operational weather prediction requirements of the National Oceanic and Atmospheric Administration (NOAA) and the global change research objectives of the National Aeronautics and Space Administration (NASA). The three instruments will be launched in the year 2000 on the EOS-PM1 spacecraft. Testing of the AIRS engineering model starts in 1996. The AIRS instrument represents a major step forward in satellite based remote sensing technology. In particular, improvements in second generation PV:HgCdTe detector array/readout technology coupled with a rapid advance in long life, low vibration, Stirling/pulse tube cryocooler design have been instrumental. This paper focuses on in flight radiometric and spectral calibration of AIRS.
Long-wavelength quantum well infrared photodetector (QWIP) research at Jet Propulsion Laboratory
Sarath D. Gunapala, John K. Liu, Mani Sundaram, et al.
One of the simplest device realizations of the classic particle-in-a-box problem of basic quantum mechanics is the quantum well infrared photodetector (QWIP). Optimization of the detector design and material growth and processing have culminated in the realization of a 15 micrometer cutoff 128 by 128 focal plane array camera and a camera with large (256 by 256 pixel) focal plane array of QWIPs which can see at 8.5 micrometer, holding forth great promise for a variety of applications in the 6 - 25 micrometer wavelength range. This paper discusses the physics of the QWIP and QWIP technology development at Jet Propulsion Laboratory.
SIRTF: the fourth great observatory
Larry L. Simmons, James L. Fanson, William R. Irace, et al.
The Space Infrared Telescope Facility (SIRTF) will explore the birth and evolution of the Universe with unprecedented sensitivity. SIRTF will be the first mission to combine the high sensitivity achievable from a cryogenic space telescope with the imaging and spectroscopic power of the new generation of infrared detector arrays. The scientific capabilities of this combination are so great that SIRTF was designated the highest priority major mission for all of U.S. astronomy in the 1990s. The astronomical community will use SIRTF to explore the infrared universe with a depth and precision complementary to that achieved by NASA's other great observatories -- the Hubble Space Telescope (HST), the Advanced X-ray Astrophysics Facility (AXAF), and the Compton Gamma Ray Observatory (GRO) in their respective spectral bands. The launch of SIRTF in 2001 will permit contemporaneous observations with HST to study forefront problems of astrophysics. This paper provides a comprehensive review of the SIRTF program -- the science, the mission design, the facility, the instruments, and the implementation approach. Emphasis is placed on those features of the program including the use of a solar (heliocentric) orbit and the adoption of a novel warm-launch cryogenic architecture -- which will allow us to realize the great scientific potential of SIRTF in a resource- constrained environment.
SIRTF telescope test facility
Daniel R. Coulter, Steven A. Macenka, Mark J. Lysek, et al.
In this paper we describe the key features of the SIRTF Telescope Test Facility developed at the Jet Propulsion Laboratory. Information on the cryogenic performance including details of the test cycle time and cryogen hold time are included. Emphasis is on the operation of the facility. Data are presented on the cryogenic optical testing of the ultra-lightweight 85 cm diameter beryllium primary mirror assembly for the infrared telescope technology testbed.
Wide-field Infrared Explorer (WIRE)
Helene R. Schember, John C. Kemp, Harry O. Ames, et al.
The wide-field infrared explorer (WIRE) is a small spaceborne telescope specifically designed to study the evolution of starburst galaxies. This powerful astronomical instrument will be capable of detecting typical starburst galaxies at a redshift of 0.5, ultraluminous infrared galaxies beyond a redshift of 2, and luminous protogalaxies beyond a redshift of 5. The WIRE survey, to be conducted during a four month period during 1998, will cover over 100 deg2 of high galactic latitude sky at 12 and 25 micrometer. WIRE will measure the ratio of 12 and 25 micrometer flux of detected sources, which is a powerful statistical luminosity indicator. The distribution of starburst galaxy 12-25 micrometer colors as a function of flux density will reveal their evolutionary history and perhaps the presence of protogalaxies at high redshifts. This mission, which is part of the NASA Small Explorer program, takes advantage of recent advances in infrared array detector technology to provide a large sensitivity gain over previously flown missions. During its four-month mission lifetime, WIRE will amass a catalog exceeding the size of the 1983 Infrared Astronomy Satellite (IRAS) Point Source Catalog at flux levels over 500 times fainter than the IRAS Faint Source Catalog. WIRE has been designed to maximize detections of high-redshift starburst galaxies using an extremely small and simple instrument. The 30 cm aperture Cassegrain telescope has no moving parts, no reimaging optics and a wide 33 by 33 arcminute field of view. The optics and detectors are cooled during the mission using a lightweight two-stage solid hydrogen cryostat. The three-axis stabilized spacecraft bus is provided by the Goddard Space Flight Center Small Explorer Project Team. The mission, to be launched in September 1998 using an Orbital Sciences Corporation Pegasus XL Launch Vehicle, is managed by GSFC.
Thermal Imagers and Their Technologies
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Conductive polymer films for microbolometer applications
James Kaufmann, Mary G. Moss, Yongqiang Wang, et al.
In order to maximize the responsivity of a thermal detector, the detector is often fabricated on a thin membrane which is suspended over a substrate. Maximizing responsivity requires minimizing the thermal conductance and heat capacity while keeping the thermal time constant below the bandwidth of the system; maximizing the temperature coefficient of resistance (TCR) of the sensor materials, and reducing system noise. Uniformity of the detector elements greatly impacts the performance of a focal plane array. We report here a new material for IR bolometer applications. The material is a polymer film which has been made conductive by ion implantation. Implanted films which have a thickness of 1500 angstrom may be patterned by conventional photoresist processes to form small geometry elements with dimensions of 10 to 50 micrometers. Suspended conducting polymer bridges are then formed from the implanted films by etching of a sacrificial layer of silicon dioxide. High quality films with resistivities from 400 ohms/square to 10 megaohms/square can be produced by the ion implantation technique. Temperature coefficient of resistance (TCR) as a function of implantation energy and film resistivity are presented.
Space-Related Technologies
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Technology of automated shaping of aspherical off-axis mirrors
Vladimir A. Gorshkov, Alexander Yu. Papaev, Alexey S. Savel'ev, et al.
Achievements of computer technology of automated shaping of large-sized optical details with achieving of diffraction quality of the image, developed by the state research-and- production association 'Optics,' permit us to expand technological opportunities of the method on creation of aspherical off-axis mirrors of a complex configuration. One example of automated shaping of off-axis paraboloids of 300 - 400 mm in diameter demonstrates opportunities of the method. Technical parameters of made off-axis aspherical mirrors are listed. Problems of automated shaping of off- axis mirrors and technological ways of their decision are specified.
Thermal Imagers and Their Technologies
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Optical and infrared detection using microcantilevers
Patrick Ian Oden, Eric A. Wachter, Panos G. Datskos, et al.
The feasibility of micromechanical optical and infrared (IR) detection using microcantilevers is demonstrated. Microcantilevers provide a simple means for developing single- and multi-element sensors for visible and infrared radiation that are smaller, more sensitive and lower in cost than quantum or thermal detectors. Microcantilevers coated with a heat absorbing layer undergo bending due to the differential stress originating from the bimetallic effect. Bending is proportional to the amount of heat absorbed and can be detected using optical or electrical methods such as resistance changes in piezoresistive cantilevers. The microcantilever sensors exhibit two distinct thermal responses: a fast one ((tau) 1thermal less than ms) and a slower one ((tau) 2thermal approximately 10 ms). A noise equivalent temperature difference, NEDT equals 90 mK was measured. When uncoated microcantilevers were irradiated by a low-power diode laser ((lambda) equals 786 nm) the noise equivalent power, NEP, was found to be 3.5 nW/(root)Hz which corresponds to a specific detectivity, D*, of 3.6 multiplied by 107 cm (DOT) (root)Hz/W at a modulation frequency of 20 Hz.
Space-Related Technologies
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Extrasolar-system planet detection problem: radiometric signal and resolution considerations
Gonzalo Paez, Marija S. Scholl
Blackbody radiation laws for photons and the simple power transfer equation are used to calculate the number of photons originating at a representative nearby solar system and incident on a unit area collecting aperture near Earth. The signal due to the planet is prohibitively small in comparison with that due to a star. The radiometric signal- to-noise ratio of 10-5 necessitates an indirect, non-imaging detection scheme, such as interferometry, that searches for a single spatial frequency corresponding to the star-planet vector distance.
Extrasolar-system planet detection problem: planet signature isolation with a rotating, rotationally shearing interferometer
Marija S. Scholl, Gonzalo Paez
An infrared, rotating, rotationally shearing interferometer may be used for a detection of a potential planet orbiting around a nearby star. We derive an expression for the signal, generated by a star and its faint companion, and detected by a rotationally shearing interferometer. It shows that the planet signal may be detected, despite the presence of a much larger star signal, because the planet produces a faint modulation superimposed on a large star signal when the aperture rotates. In the particular case of a rotating, rotationally shearing interferometer, the argument of the cosine term is shown to depend only on the planet and observational parameters. However, the amplitude of the modulation term in the interferometric signal is shown to be proportional to the star intensity.