Sensors using linear arrays of pyroelectric detectors are capable of fulfilling a number of infrared sensing roles in which the detector signal bandwidth is limited to a few tens of Hertz. In these circumstances they can have an NETD of 0.25K while maintaining low cost, low power consumption, and operation at ambient temperature. An experimental imager has been designed and built to evaluate linear pyroelectric arrays, its performance has been analysed, and it has been tested in the field for a number of applications.

Zoom telescopes offer the system designer great flexibility and give the user an uninterrupted change from wide angle to narrow angle fields of view. This has been recognised by the selection of a zoom telescope for the U.K. MoD's Phoenix RPV programme. The mechanical design of such a telescope is described. Those aspects relating to volume production are considered in more depth.

The paper is intended to familiarize engineers with zoom lens tolerances and their bearing upon optical, mechanical and electronic design aspects. Conceptual design solutions for typical system requirements, such as athermalization and boresighting, are described by way of a broad tolerance analysis of a high performance infrared zoom lens.

The infrared zoom lenses are of prime interest for thermal imagery, IR systems simulation or missiles guiding. They are composed of germanium chiefly, which main drawback is the important variation of its refraction index according to the temperature. Generally, this problem can be solved while refocusing the image by displacement of front or rear lens-elements of the zoom lens. Therefore, this involves new translation guidings, not necessary to the zooming function. There appears the possibility and interest of using a converter element already in translation for the zooming function, to perform the functions of thermal compensation and focusing. Then the displacement of the considered element takes the focal-length, the focusing and the temperature into account.

A supplementary infrared optical system has been developed at the National Physical Laboratory (NPL) to attach to a far-focus wide-angle telescope supplied for use with a TICM II thermal imager. It uses just two germanium lenses, of 75 mm and 90 mm diameter, and allows object distances from infinity down to 0.27 m. When combined with the high quality telescope and the scanner optics, the complete system has no discernible field curvature at any working distance, an important requirement for the NPL application of measuring the spatial distribution of emissivity of extended flat surfaces. The geometrical MTF data computed for 32 combinations of object distance, field angle and aperture plane show that under most conditions the effect of aberrations is significantly less than that of diffraction. In fact spatial resolution is ultimately limited by the diffusion spread in the detector, and the performance of the optical system is always fully adequate for the 512 x 512 pixel image processing involved.

This paper discusses methods of achieving the optimum in high resolution galvanometric scanning. When scanning systems have problems of repeatability, jitter, and wobble, the difficulties are often caused by inadequate mirror design, bonding, and/or alignment and the dynamic forces engendered by the driving torque. These issues are examined, and integral metal mirror mounts are compared with the conventional composite mirrors bonded to metal mounts. Galvanometer bearing suspension and drive electronics and how they relate to optimal high resolution are also addressed.

Focal plane arrays (FPA) of CdHgTe detectors have been incorporated successfully into infrared imagers with sensitivities in either the 3-5 µm or 8-14 µm bands. Whilst it has been possible to obtain good imagery with minimal fixed pattern noise using digital non-uniformity correction electronics, these imagers suffer from problems caused by the sampling of the scene by the FPA; in particular, aliasing results in the obscuration of high frequency detail in the scene and its appearance at lower frequencies below the Nyquist frequency. It is demonstrated how microscanning may be used to reduce these sampling effects and in addition, ways of improving the ease of viewing of the final image by reducing the degree of pixelation are discussed.

SOPELEM is equipped with a high precision diamond turning MCOPE machine to manufacture our own aspheric components. We present results obtained with this process along with the tests carried out. Several applications with 1NFRA-RED systems are shown, in spectral bandwidths : 3 to 5 microns and a to 12 microns.

Single point diamond machining of infra-red optical components such as aluminium mirrors, germanium lenses and zinc sulphide domes is potentially the most cost effective method for their manufacture since components may be machined from the blanks to a high surface finish, requiring no subsequent polishing, in a few minutes. Machines for the production of flat surfaces are well established. Diamond turning lathes for curved surfaces however require a high capital investment which can be justified only for research purposes or high volume production. The present paper describes the development of a low cost production machine based on a Bryant Symons diamond turning lathe which is able to machine spherical components to the required form and finish. It employs two horizontal spindles one for the workpiece the other for the tool. The machined radius of curvature is set by the alignment of the axes and the radius of the tool motion, as in conventional generation. The diamond tool is always normal to the workpiece and does not need to be accurately profiled. There are two variants of this basic machine. For machining hemispherical domes the axes are at right angles while for lenses with positive or negative curvature these axes are adjustable. An aspherical machine is under development, based on the all mechanical spherical machine, but in which a ± 2 mm aspherecity may be imposed on the best fit sphere by moving the work spindle under numerical control.

The principles of precision temperature control are presented in this paper. Emphasis is placed on the use of heat exchangers with large flowrates of coolant. Design considerations for such systems are highlighted. In particular, the selection of system components appropriate to the desired level of performance is discussed. Several feedback control techniques are also presented.

A diamond machining facility has been established at British Aerospace capable of generating optical quality surface finishes with a range of rotationally symmetric shapes on a large number of different materials. In particular fresnel lens shapes have been produced on different substrate materials. An investigation into the design and manufacture of fresnel lens forms having constant depth spherical facets has been carried out. Some details of the diamond machining manufacturing process and considerations given to the diamond tool geometry and their design are described. In order to produce flawless lenses the conditions of manufacture are critical. The final lens must be thin enough to obtain adequate transmission in the infra-red and the lens facets must be accurately formed requiring that the material have a good melt flow index. High density polyethylene was chosen as the most suitable material for the manufacture of the fresnel lenses described here. Optical testing and evaluation of the plastic moulded lenses made from the diamond machined metal dies are discussed.

The design and manufacture of a large chisel window assembly is reviewed, the intended application being for a mirror-stabilized narrow field of view thermal imager in a high speed aircraft. Aerodynamic heating was expected to be significant, and this placed restrictions on the choice of material and the configuration of the window assembly. The practical problems of procurement and manufacture are discussed, including material supply, edging, polishing, coating and assembly. The results of IR interferometric tests on individual panes and on the final assembly are presented. The window is shown to achieve diffraction-limited performance, while being capable of withstanding high temperature and pressures, and is resistant to rain erosion.

The lack of durability of the outermost coated lens or window of thermal imaging systems had been a problem for many years. It was overcome in the mid-seventies by the development within RSRE of the infra-red transparent diamond-like carbon coating. This material was chemically durable, abrasion resistant and a near perfect match to germanium as a single layer anti-reflection coating. Originally the coatings had reasonable infra-red transmission but their hardness and adhesion were variable. Using our own processes we obtained consistently good coatings with optimised transmission. The application and excellent performance of these coatings on germanium components is described. Another application is the protection of diamond flycut aluminium surfaces where the off-normal reflectivity in the infra-red using conventional coatings can be poor. Having developed these coatings it was then necessary to develop specifications before they could be used in service. The development of coatings test procedures and specifications is also described.

The rain erosion resistance of germanium may be improved by hydrogenated amorphous carbon (a-C:H) film coatings. a-C:H films are prepared by plasma deposition from hydrocarbons in RF diode glow discharge. The deposition parameters are adjusted to obtain controlled deposition rate and H/C ratio. The coatings are a quarter-wave thick at 10.6 μm. Their knoop micro-hardness is from 1800 to 2200 kgmm-2 for a 10-grams, 30-seconds load. The rain erosion is achieved with the Saab-Scania whirling-arm (Linkoping, Sweden). The impact velocity varies from 200 to 300 ms-l. The optical damage is characterized after each exposure, by modulation transfer function measurement. For 1.2 mm drop diameter the occurrence time of a given optical damage is increased by a factor of 6 to 7. For a 2 mm drop diameter, a factor of about 3 improvement is achieved. This last result is in good agreement with R.A.E. work. For 1.2 mm drop diameter the impingement angle effect is also reported and found in agreement with the sinus law.

The techniques generally used for measuring spectral transmission of lenses in the visible wavelength range are difficult to apply in the range of thermal wavelengths (2 to 14 Microns). The paper describes a more appropriate technique which can be used both for measuring the axial transmission factor of a lens system as well as the variation of transmission over the aperture. Two particular equipment configurations are described, one is designed to integrate with a computerised MTF instrument, whilst the other is based on the use of a commercial radiometer.

The design and development of an infrared lens centering machine is described. The device works in transmission mode so that access is not required to the rear surface of the test component. Although developed for the centration of germanium lenses it works equally in the visible and also with other IR materials, allowing centration accuracies better than 2 arc sec to be achieved. A theoretical analysis is given and an expression for the noise equivalent decentration (NED) is derived. A design example is given followed by a calculation of expected performance. The method of discriminating between front and rear surfaces is described.

A heterodyne interferometer was developped to be used in the visible and in the infrared. If the RMS wavefront error is used to determine a datum focal plane, MTF measurements differ by less than 3% from calculated values for two special test lenses. The interferometers are compared to other MTF measuring techniques.

For a number of years we have been conducting modulation transfer function (MTF) analyses on infra-red lenses and windows using (1) line spread function (LSF) and (2) interferometric measurements. Although generally comparisons between results obtained from the two methods have been good, there have been some occasions when differences have been observed. This paper presents some of the results and discusses possible causes for the discrepancies.

An operational MTF measuring bench operating in both visible and infra-red regions is described. Measurements can be made at both room and climatic chamber temperatures. The basic mathematics for measuring the MTF from the edge spread function (ESF) or from the line spread function (LSF) are given. Optimal criteria for the measurement are derived taking into account the spatial sampling frequency and spectral resolution. The results obtained with standard lenses are compared with theoretical calculations. The microcomputer software has been optimized in order to give the result in form of graphs in a few seconds. If also provides options for measuring focal lengths or magnification, distortion, field curvature and transmission.

Two levels of evaluation are implemented for the assessment of IR optical systems. The first level takes place during the fabrication process. It consists in interferometric measurements at a wavelength of 10 microns, for the control of the homogeneity of raw IR materials, and for the alignment of the whole lens system. It also consists in phase interferometry operated on each critical surface in the visible range for the prevision of the optical quality of the finished lens system. The second level consists in the conformance tests performed on the finished optical system. It includes measurements of such quantities as line spread function, optical transfer function, focal length, angular shift of optical axis and variation of transmission factor with temperature. Results on several lenses are presented.

The action of rain on irdome materials can lead to important damages. A comparative study of optical damages and of erosion is conducted for various infrared materials. The sample erosion is characterized by conventional mass loss measurements. The optical damage is characterized, after each rain exposure, by the modulation transfer function (MFT) measurement. An optical infrared set-up allows MFT measurements for spatial frequencies from 66 to 1000 cycles/rad. and various spectral ranges: 2-12 μm,2-3 μm,3.5-6 μm and 8-12 μm. The dependence of MFT wear on impact velocity is similar to that of the mass loss: occurence time of damages is inversely proportionnal to a high-exponent power law of the velocity. This exponent is characteristic of the material. The optical damage depends on the spectral range and the spatial frequency. This last point justifies the use of the MFT measurement. For some materials, the optical damage occurs in synchronism with the erosion, and for others before the beginning of the erosion. Thereby, the infrared material screening must be achieved by MFT measurements rather than by mass loss measurements.

The noise frequency spectrum of over 100 SPRITE infrared detector filaments has been measured, at 5 different bias fields, between 600Hz and 10MHz. A 5-variable parametric equation has been fitted to each data set to enable the variations of different parameters to be assessed.

The paper discusses some of the crtieria used to characterise the performance of thermal imaging systems and describes equipment which has been developed for their measurement. Particular attention is paid to the measurement of MRTD (minimum resolvable temperature difference) and recent work on an objective measurement technique is described.

The minimum resolvable temperature difference of a thermal imager is generally accepted as being the performance parameter most closely related to the imager's performance in the field. It is, however, universally conceded that an objective test technique is urgently required to replace the current subjective method of measurement, thus removing the dependence on trained operators. Simplistically this can, at first sight, be easily achieved via the measurement of the system modulation transfer function, noise power spectrum and signal transfer function. However, the practice of measuring these system parameters is not so straight forward. This paper deals with a practical implementation of such an objective method of testing, based upon a method proposed by the Royal Aircraft Establishment, Farnborough, subsequently developed at GEC Avionics, Basildon. It deals with the mathematical subtleties of applying the required discrete Fourier transforms in software and of integrating waveforms to achieve acceptable signal to noise ratios. The paper also gives examples of the objective results achieved, and a comparison with the corresponding subjective results.

Thermal imaging system performance is described by its Minimum Resolvable Temperature Difference (MRTD), which is the spatial frequency dependent thermal sensitivity. Three different MRTD models are described in this work: two of which are based on the adaptive matched filter concept in order to describe the human eye-brain combination while the Third uses the limited synchronous integrator concept. In all three models the generally used assumptions of periodicity and of one dimensional targets are replaced by two dimensional and more realistic representation of the targets. MRTD expressions are derived for the above mentioned models and the values calculated from them are compared with the Ratches-Lawson model predictions and with measured results for two different systems with known parameters. It is shown that the limited synchronous integrator model results in a more accurate functional dependence ot the MRTD on the spatial frequency. The prediction error commonly found in the low frequency region is reduced and the overall accuracy is enhanced throughout the frequency range of the system in comparison to the Ratches-Lawson model.

Broad bandwidth infrared display systems have been developed for use in evaluating infrared imagers and processors. The displays use electrically heated diode resistor arrays as the emitting devices which are line at a time addressed. The displays have a black body emission spectrum and accept data electronically. Maximum display temperature exceeding 25K, temperature resolution of 0.1K and a time constant of 10 msec have been demonstrated in a 100 line system.

In a previous paper we have introduced a new computerized system approach to the field of infrared spectroradiometric measurements. In this paper, after reviewing the basic definitions and design principles, we present a number of important capabilities and applications of the measuring system. The power of the system finds its expression in several aspects: i) in producing calibrated spectral data in almost real time; ii) in enabling the user to perform a large number of mathematical and statistical treatments to the processed spectra without need of an additional large computer; iii) in being able to control the parameters of external systems such as the temperature of calibration sources, temperature and position of samples, scanning mechanisms etc., in an automatic or keyboard-operated, and user-friendly manner; iv) in giving the user an almost unlimited freedom to program his own measurements and data processing for special applications; v) in offering a recording and filing capability for data comparison, which was never known before.

Photoacoustic spectroscopy uses optically induced heat fluxes to characterise chromophore type and distribution in solids. Recent developments extending the range of the technique are described in this paper. In particular, the use of optical detection schemes for non-contacting photoacoustic spectroscopy, and the use of impulse response photoacoustic spectroscopy for the study of chromophore distribution.

Recently it was pointed out that photothermal deflection spectroscopy (PDS) is an important tool capable of measuring either very small absorption coefficients or low sample concentrations 1-5. In this method, two laser beams are focused in an interaction region of the sample. One laser, a pump laser which has relatively high power is pulsed and can be tuned to an absorption of the gaseous sample. The advantages of using pulsed laser are that much higher power is available and also measurements related to a transient effect can be made. The other laser, a probe laser, has a lower power, low divergence and high stability. When the pump laser is turned on, the temperature of the gas begins to increase, initially having the same spatial profile as the pump laser, resulting in a temperature gradient. This temperature gradient causes a gradient in the index of refraction due to the density gradient. The index gradient bends the probe laser beam and the deflection is measured by a position sensitive detector.

We have previously used real time visible T.V. image processing to monitor road traffic. Searches for simpler scene information have led us to infrared imaging with a pyroelectric vidicon. Our paper will compare the visible and infrared information and its real time preprocessing requirements. Use of these features will be described in the areas of simple vehicle classification, tracking through entry and exit points of simple road junctions and for vehicle separation. The real time information processing operations are carried out on our pipeline processing system which uses dedicated processors and reconfigurable processing routes operating at full frame T.V. rates.

Non-destructive, rapid optical techniques are particularly amenable to the analysis of semiconductor and device-related materials. This paper briefly considers three particular applications of IR spectroscopy in the routine assessment of electronic materials at the GEC Hirst Research Centre. These include the analysis of impurity levels in silicon, their location and interaction behaviour, the physical and compositional analysis of dielectric glassy films used in planar devices in silicon, and the compositional and thickness mapping of II-VI alloy IR detector materials.

Infrared thermovision technique is used in investigating thermal fields on microelectronic circuits. The recorded thermograms indicate both the chip-thermal distribution and chip faults if any. The results are in agreement with the simulated circuit model used.

The measurement of the infrared energy emitted from materials has been of interest since at least the time of Coblentz. Applications for Space, Solar Energy, etc. have increased the interest in the field in the last twenty-five years. The emittance of a sample at any given wavelength is one minus the sum of the reflectance and transmittance (E=1.-(R+T)). The instrument described here illuminates the sample at near normal incidence and collects all of the reflected or transmitted flux with an integrating sphere. Since the flux on the detector in this case is orders of magnitude less than if it could be focused, it is necessary to use a Fourier Transform spectrophotometer to get adequate signal to noise. To obtain good photometric accuracy, a true double beam system is used which simultaneously observes the sample and a reference. This eliminates the effects of drift in the source, detector, interferometer, etc. This system also has an advantage over hohlraum and ellipsoidal reflector systems in that very little energy irradiates the sample and therefore no heating occurs. This system uses an IBM-PC for the data processing. The transmittance of lenses and irregular samples can also be measured. Representative sample spectra are shown for a variety of applications.

Homodyne interferometry has been largely used for optical surfaces characterization. However, when quantitative data are required, this technique is very time consuming. Direct phase measurement by heterodyne interferometry can provide a fast and accurate means of obtaining surface profiles. In the following paper, we describe such a method making it possible to determine surfaces shapes.

A new and versatile experimental stress analysis technique has recently been developed, based on the measurement of the infra-red radiation emitted from the surface of a body as a result of temperature changes caused by cyclic loading within the elastic range (i.e. the thermoelastic effect). The theory is outlined and the apparatus (referred to as the SPATE equipment) is described. A number of applications are described to illustrate the principal characteristics of the technique which is now regarded as a valuable new approach in the stress analysis and design assessment of a wide range of engineering components and structures. Possible future developments in this area are outlined.

The use of infra-red techniques for full field stress analysis has increased rapidly in the last two or three years, due mainly to the introduction of a production model of the SPATE (Stress Pattern Analysis by Thermal Emission) equipment, developed by Sira Ltd. The Sira technique makes use of the thermoelastic effect by measuring the very small temperature changes which occur when structures are cyclically loaded. This paper describes the investigation of structures under broad-band random loading, using a standard SPATE 8000 together with an add-on hardware/software system developed for this purpose at the National Engineering Laboratory.

With the fast growing utilisation of composite materials in aircraft structures, manufacturers have to acquire appropriate non destructive testing systems. A large effort have been devoted for the last ten years to the improvement of two major techniques : ultrasonics and radiography. Up to now, these methods have been fully automated and their efficiency proven. However a demand exists for new methods which can offer a higher inspection rate than ultrasonics and can detect a wider range of defects than radiography. These considerations led us to look to thermography. Infrared non destructive testing is attractive since it requires no physical contact. It is potentially very rapide and easy to set up. It can be applied when only one side of a surface is accessible. Real time display and recording associated with image treatment make the interpretation of thermograms easy. A large investigation programme is carried out in order, to define the field of application of thermography to composite materials evaluation, to set up a method which can be industrialised, to write down specifications for an industrial installation. Thermophysical properties of the materials, different heat sources, infrared detectors and image processing systems are investigated. Calibration of the apparatus is also considered. An original method using the combination of a line heater, a line scanner and a real time digital signal processing and recording system is presented.

Non-destructive testing (NDT) of materials can be achieved via proper photonic excitation and radiometric monitoring of the induced thermal changes. The theoretical support for this photothermal conversion in bi-layered materials is proposed, single-pulse and periodically modulated fluxes being considered. Some practical proposals are derived concerning the various aims of NDT: coatings thickness measurements, detection of defective bondings or delaminations, measurements of contact resistances between two layers. Measurements performed with a commercially available infra-red scanner and a digital data acquisition and processing system are reported.

The introduction, over the past few years, of thermal imagers with Sprite detectors and optical scanning systems compatible with TV video standards has opened up many new fields of application. A particular example which this paper describes is a thermal pulse technique pioneered by Harwell for the non-destructive inspection of different materials for sub-surface defects and other structural features(1)(2). The method is now commonly referred to as Pulse Video Thermography or PVT. Its success depends on the differing thermal properties of materials as defined by their thermal diffusivities. When a short pulse of heat incident at time to is absorbed by a surface it diffuses through the material until a new equilibrium is regained. During this time any obstructions to the diffusion or any local differences in the thermal properties of the material, will at certain times after time to give rise to detectable temperature differences or contrasts on the external surfaces. These transient thermal events can be monitored by a thermal imager and recorded on a video cassette recorder for a subsequent field-by-field interpretation and analysis. In this paper the basic principles are described and some examples are given on how PVT has been successfully applied to materials of widely different thermal properties. The use of Pulse Video Thermography as a non-destructive method of inspection is now well established. But its wider adoption is at present inhibited by the comparatively high costs of thermal imagers and their supporting logistics. If cheaper pyro-electric Vidicons can achieve comparable performance to the optical scanners then PVT would soon be recognised as a complementary technique to those traditionally used for industrial nondestructive testing.

Conventional infra-red gas analysers require the gas stream to be sampled, introducing problems associated with cleaning the sample and, in the case of water vapour, ensuring that no condensation occurs in the sampling lines and analyser. The paper presents the development of instruments designed to solve these problems at source by obtaining the measurements in situ over open paths, thus eliminating the need to sample the gas stream. The technique presented for the analysis of water vapour is to transmit across the waste gas ducting a narrow spectral band of radiation which coincides with the 1.87μm water vapour absorption band. In addition, two wavelengths outside the absorption band, are employed as a reference to compensate for the attenuation of the beam by other agents, such as particulate matter transported by the gas stream. The method presented for the analysis of carbon monoxide differs in that instead of using interference filters to define narrow spectral bands the gas cell correlation technique is employed.

This report presents an automated analyzer which continuously monitors oil content of a sample water stream that flows through the analyzer. The measuring principle is based on the absorption of infrared radiation by oil molecules contained in the sample water. The wavelength band that is used in the measurement is at 3.4 μm, where different types of oils show nearly equal absorption. Another wavelength band of 3.6 μm, where oil has no absorption, is used to compensate the effect of turbidity, which is due to solid particles and oil droplets contained in the sample water. Before entering the analyzer the sample water flow is properly homogenized. To compensate the strong absorption by water molecules in these wavelength bands the sample water is compared with reference water. This is done by directing them alternately through the same measuring cell. The reference water is obtained from the sample water by ultrafiltration and it determines the base line for the contaminated sample water. To ensure the stability of the base line, temperature and pressure differences of the two waters are kept within adequate ranges. Areas of application of the analyzer are wide ranging i.a. from ships' discharge waters to waste waters of industrial processes. The first application of the analyzer is on board oil tankers to control the discharge process of bilge and ballast waters. The analyzer is the first that fully corresponds to the stringent regulations for oil content monitors by the International Maritime Organization (IMO). Pilot installations of the analyzer are made on industrial plants.

Infrared absorption measurement techniques are widely used in both laboratory and production plant, to measure the thickness and composition of extruded polymer films. Recent developments in film production technology permit the manufacture of transparent films of relatively high refractive index with optically flat and parallel surfaces. Since the optical thickness of such films is comparable with the coherence length of the infrared radiation used, optical interference effects can cause serious errors in the measurement. Various strategies for suppression of interference effects are presented and practical techniques based on these strategies are described.

The paper is mostly a review of the evolution of the attitude control systems requirements, of the concepts and equipment developed by Sodern for the spacecraft attitude sensing with respect to the Earth and of the experience gained from sensors operation on board satellites. It ends with remarks about the future of sensing techniques for the spacecraft attitude control with respect to the Earth.

Infrared television cameras, based upon platinum silicide photodiode arrays, have advanced in sensitivity, resolution and reliability to where they could have wide ranging application to medical, industrial and scientific measurement. In this paper we will present examples of silicide camera imagery which show the sort of data which might be expected from such measurements.

The Honeywell MiniFLIR, a serial scan TV-compatible system, can be equipped with single or double rows of discrete detectors or with nondelineated bars of detectors. In this paper various configurations and electronic enhancements are described and their related FLIR performance demonstrated through recorded video imagery.

Laboratory evaluation is provided of the improved focal plane array performance realized with a novel optical technique that increases the fill factor of Schottky IRCCD mosaics. Specifically, a lenticulated silicon faceplate is installed on the IRCCD chip to redirect focused image irradiance away from nonsensitive areas in the focal plane and to the infrared-sensitive elements. A technique has been developed for successfully fabricating these optical faceplates with the necessary geometrical requirements. The performance data contained herein were obtained with an RCA-supplied 32 x 63 Schottky IRCCD mosaic having a lenticulated faceplate installed on a portion of the array surface. The adjacent dual construction allowed sensitivity and resolution differences to be easily evaluated under identical operating conditions. The enhanced performance was determined experimentally and then compared to predicted fill-factor improvement.

Focal plane arrays built with indium antimonide charge injection device technology are made of a group of two coupled MIS capacitors which collect and store photon generated charge carriers. The selection of a site is accomplished by an X-Y decoding technique. This adressing method allows to read out arrays either sequentially or in group (line or area). For applications at 77 K SAT has developped bidimensionnal structures (8 x 8 and 32 x 32 elements). To extend their application to astronomy, structure parameters have been analysed at very low operating temperature and low backgrounds. For a temperature near 4 K, a saturation time over 10 seconds and a noise of 1400 carriers combined with great filling factor of the focal plane (> 80%) and the read-out efficiency (25 %), these values allow to plan the use of this device for efficient imaging. Low to very low background conditions are generally met in infrared astronomical experiments, especially in space where cold optics can be used. On the other hand very high sensitivities are required because of the weakness of the sources. Thus arrays cooled by liquid He are well adapted to such conditions since long integration times are allowed. Two prototypes of ground based infrared cameras using 8 x 8 and 32 x 32 InSb CID arrays have been developped and used on a 2 meter telescope at the "Observatoire du Pic du Midi". The systems are described and first results given. An infrared camera has been proposed by a consortium of european laboratories as a focal plane instrument for the Infrared Space Observatory project (ISO). First test results on noise, particle immmunity and integration time are given. This shows that a CID InSb array is an extremely serious candidate for such an application.

The Space Infrared Telescope Facility (SIRTF) is a space-borne astronomical near-infrared to submillimeter telescope. Because of its high sensitivity, SIRTF will significantly increase observational capability over what is currently available. SIRTF is being developed by NASA to fly in the mid 90's. It will be carried to orbit by the Space Transportation System and placed in its final orbit by the Orbiting Maneuvering Vehicle.

This paper presents methods used to quantify the resolution and thermal sensitivity of an airborne Thermal Imaging System (TIS) in the in-flight environment. By determining in-flight resolution and sensitivity of the total system including sensor, aircraft inter-face, display and pilot, a realistic measure of the system's true operational performance capabilities can be determined. The effects of target radiation and atmospheric transmittance are included in the evaluation. Descriptions of two types of aircraft systems, the Single Seat Night Attack (SSNA) A-10 and the Low Altitude Navigation and Targeting Infrared System for Night (LANTIRN), are presented.

While 1,06 µm laser rangefinders (LRF) have already a widespread use in fire-arm control, developments have taken place in order to both miniaturize and lower the cost of those equipments mostly designed for ground-to-ground applications. On the other hand, ground-to-air or air-to-ground applications require a target tracking capability which, in turn, asks for rangefinders with higher repetition rates. Through proper design, such LRF become adapted as well to target illumination and designation, thus leading to multi-purpose equipments. More recently, many attractive advantages of the carbone dioxide laser opera-ting in the 9-11 µm range have been put into use to design equipments which have been already field-tested and present the designers with very interesting possibilities : simultaneous target ranging and radial velocity measurement, coupling with forward looking infra-red (FLIR) imagers, frequency hoping rangefinding as well as remote sensing of nerve agents.

This paper deals with a breadboard of CO2 laser Doppler rangefinder based upon the "chirp pulse compression" technique, and realized in common by Thomson-CSF and Cilas. It recalls some design considerations derived from properties of heterodyne detection and basic radar theory, then describes the principle and main components of this equipment, and evaluates its overall performance.

An infrared FM-CW Lidar has been built that uses pulse compression techniques. This system has been interfaced with a real time computer and field tested allowing the generation of a 3-D imagery whose statistics will be discussed.

This dynamic and calibrated infrared imagery simulation system displays realistic variable aspect moving targets in battlefield environment for the evaluation of infrared imaging equipments . The simulation is based on a two stage process : -Generation of a video tape of the desired scenario -Display of the pictures at the input of a visible-to-infrared converter (liquid cristal light valve) .

This paper describes a dynamic infrared images generator based on the use of a visible to infrared transducer. The performances of this generator are discussed. The frame rate (25 Hz), the spatial resolution (3 points per millimeter), the thermal contrast (from 0.1° to 40°C), the mean temperature adjustable between - 40° and + 40°C make possible the test of a lot of infrared existing or future systems.

Using computer simulation proves to be a good way of assessing new concepts or the application of new technologies both to existing and future systems. It has therefore been used during the specification phase for new thermal imagers. Thanks to computer simulation, the humain operator, who will be the user of the system, has also been taken into account in the assessment.

Two dimensional arrays of infrared detectors can form the basis of many systems, offering a number of features not shared by existing thermal imagers. MCCS Frimley and RSRE have been engaged in the development of this form of thermal imaging for operation in both the 3-5 and 8-14 micron wavebands. In this paper, the utilisation of such systems will be discussed and examples of the imaging obtained will be shown.