A very large-scale hybrid module incorporating laminated ceramic boards, deposited PbS detectors, and wirebonded filter/MUX chips is described. This module can be used as an element of a large staring mosaic detection array or a high density multiple linear array. The paper reviews the module design for the staring sensor application and discusses material and process developmental issues. Test results are presented for both module components and the module itself.

Two-dimensional x-y addressed mosaic arrays of more than 12,000 lead-sulfide detectors (64 x 192 detectors in an active area slightly larger than 1/4 by 3/4 inch) have been successfully developed, tested, and demonstrated at Aerojet ElectroSystems Company. This paper describes the pulse-bias modulation concept used to operate the detectors and process their outputs, the design and fabrication techniques used to implement this concept, and the measured performance of these arrays, which was independently verified by the Naval Ocean Systems Center in San Diego.

This paper presents theoretical analysis for a staring mosaic infrared sensor with representative examples of data processing from a computer simulation. The analysis treats: (1) generation of synthetic two-dimensional scenes with specified cloud geometry and desired statistical characteristics, (2) the processing of frames of data from two-dimensional scenes to represent temporal, spatial, and multispectral filtering, and (3) the thresholding and examination of the processed scenes to implement track association. The temporal filtering includes multiple differencing, statistically optimal non-recursive filtering, and recursive filtering. Methods are presented for reducing the computation load when calculating the optimal coefficients in spatial and multispectral filtering. The track association uses thresholding and examination to eliminate stationary objects with track assembly similar to the "streak algorithm." For visual display, the two-dimensional scenes and the processed frames are output with a forty-eight level gray scale.

The effect of spacecraft induced line-of-sight (LOS) jitter on the performance of a spaceborne IR sensor in the presence of spatially varying earth background is analyzed. This paper presents a one-dimensional stochastic model of the spatially varying background process as seen by a staring sensor with its LOS under-going jitter which is in turn prescribed by a stochastic process. More specifically, the background and jitter processes are combined in deriving a closed-form expression for the temporal autocorrelation function of the irradiance. A method of quantitatively evaluating the effect of LOS jitter on sensor performance in terms of signal-to-noise ratio degradation is also included.

When a satellite-borne mosaic sensor stares at a fixed point on earth, most of the detectors have a relative motion with respect to the earth. The effects of this motion on sensor performance have been presented in earlier SPIE papers. In these earlier examples the rates were calculated using the differential position during a time interval. The rate equations presented in this paper are true derivatives rather than differentials. The rate equations are also presented for several sets of angles related to this problem, including off-line-of-sight angles.

The derivation of earth relative motion (or "smear rate") in a step-stare spaceborne optical system is presented. Suggested methods of compensating for the smear by focal-plane manipulation are also given. The simulation results of smearing for a 4-hour orbit optical system operating in a step-stare mode (above 45° North Latitude) are provided.

With the advent of large arrays of IR detectors, it is possible to construct quasi-staring sensors whose function is to detect weakly radiating moving targets against an intensely cluttered background. The detection philosophy is based on the fact that as the target passes across a detector's footprint, the irradiance on the detector during the current frame is different than the irradiance during the previous frame when the target was outside the detector's field-of-view. By comparing (i.e., differencing) the detector's output signal from the current frame against the output from the previous frame, the presence of the moving target can be recognized while the effects of spatial variation in the background are completely nullified. If for some reason, however, the background scene moves even slightly relative to the detector during a frame, the comparison process is unable to completely reject background clutter-background spatial variations, i.e., clutter, now produce changes in the detector's output, and background clutter leaks through the signal processor. We have investigated the statistics of clutter leakage and options in signal processor design for a satellite-borne sensor whose goal is to detect moving aircraft against the earth background when the sensor has a slowly drifting line-of-sight. We have developed a statistical methodology and corresponding formulas to allow us to evaluate the peak signal-to-rms clutter (and peak signal-to-rms shot noise) for a general sig-nal processor based on digital filtering. Taking advantage of the diffraction limit in the optics transfer function, which insures that there is a (temporal frequency) region in the detector output spectrum in which there is no clutter noise, we found that we could configure a digital filter which let a significant portion of the target spectrum through its passband, but only allowed clutter through by leakage in its side lobes. The achieved signal-to-clutter ratio and the allowable line-of-sight drift velocity were impressively high for this signal processor-much better than for a differencing processor. Details of the signal processor designs and sample quantitative results will be presented, along with trade-off-considerations.

Recent advances in technology, in particular monolithic detector arrays, make it possible to detect and track aircraft from space. A number of options and trade-offs are discussed and a baseline concept of step-stare infrared sensors is described which performs both search and track over wide areas. Phenomenological modeling and technology advances needed for further sensor optimization are discussed.

Various figures of merit that can be used to describe different aspects of infrared sensor performance are described for sensors using photon detectors in a nearly photon background limited mode. Since photon detectors generate charges or currents by absorption of photons, the analyses are based on photon detectivity rather than power detectivity. Consistent use of such an approach could eliminate much confusion in the specification of infrared detectors and sensors and simplification of performance analyses. Performance parameters are presented for both scanning and staring systems and include optical, detector, and front-end signal processing characteristics.

The problem of target identification and track assembly from successive image frames from a satellite based infrared mosaic detection is considered. The wide variety of digital and electronic algorithms for bulk filtering, target identification, and track assembly are described. Optical pattern recognition techniques are also described.

Several fast, three element refractive objectives have been designed for use with narrow bandpass filters and cooled detector arrays in the 8-13 μm infrared band. The performance of these designs, measured by the fraction of incoming radiation concentrated within the boundaries of a typical detector element, approaches the theoretical maximum. The designs also illustrate the extent to which performance can be improved through the use of aspheric surfaces.

The results of liquid phase epitaxially grown single crystal Pb₀,₈Sn₀,₂Te films and the hetero-epitaxially grown PbTe/Pb0,₈Sn₀,₂Te are reported. The substrates used are cut from' the vapor-phase transportation grown single crystal Pb₀,₈Sn_0.2Te with (100) orientation. PbSnTe films epitaxially grown with relatively low temperature on these substrates exhibit peak responte in the 10-10.6 um range. λς≤ 12um. Typical heterojunction detectors have a D⁺(500K,1000,1) of 2-4x10⁹cmHz ^½w^-1. it is now limited by the noise of the preamplifier. The I-V characteristic of the heterojunction is analysed. The zero bias resistance is measured to be in the range of 20-80 ohms, the quantum efficiency n to be approximately 30%. There are some generation-recombination current contributions to the diode current.

Cryogenic cooling by solid cryogens has been utilized in recent years to provide long term instrument cooling in orbit and has demonstrated excellent temperature stability and reliability. Thus far, the solid cryogen system for a given instrument has been specifically developed for each instrument. In an effort to reduce system cost and development time and risk, a study has been conducted to determine the feasibility of a multi-mission cooler. This cooler would have a wide range of application for various instruments and missions and would be reusable and compatible with a variety of cryogens to cover the 10-90°K temperature range. Preliminary design studies have been performed for this system and show the range of application and the characteristics of this cooler. The baseline cooler which evolved utilizes two stages of solid cryogen and incorporates an optional higher temperature third stage which may be cooled by a passive radiator or by other means. An easily adaptable interface is provided which can accommodate a wide variety of instrument configurations through its "drop-in" shrink fit connection.

The Department of Energy (DOE) Building Diagnostics Program includes as a major element the controlled development of the IR sensor technology as a basic tool in the analysis of heat loss and overall energy efficiency of both industrial buildings and private homes. In fact, a substantial industry has already developed to conduct both ground and aerial surveys of building structures with the intent of locating building thermal faults and in many cases actually diagnosing the causes. Unfortunately, standards describing the proper procedures for conducting these surveys and a clear methodology for choosing the proper IR sensor hardware for various types or qualities of surveys are almost non-existent. This paper describes the methodology now being proposed through newly developed standards. In particular, it outlines the requirements for IR imagers which might be used for interior building heat loss surveys. The requirements depend heavily on a simplification of the minimum resolvable temperature difference (MRTD) parameter presently forming the core of image evaluation (IE) and performance modeling technology in the Department of Defense (DOD).

Staring and scanning electro-optic sensors for many future satellite and airborne systems will use advanced technology focal plane arrays involving very large numbers of detectors. This requirement exists for both the visible and infrared spectrums. Sophisticated computer-aided measurement facilities and software are needed for mosaic sensor test and calibration, detailed evaluation and characterization of advanced mosaic focal plane arrays, processing and analysis of mosaic sensor flight data, and laboratory sensor simulations. This paper describes the Mosaic Sensor Test and Calibration facility (MOSTAC) which uses a fully dedicated Eclipse S/230 minicomputer with many associated peripherals configured specifically for high-speed acquisition, processing and display of data from mosaic sensors and focal plane arrays, and for the measurement and control of experimental parameters. The system is designed specifically as a research tool for the characterization of advanced infrared and visible focal plane arrays, and as a facility for the testing and calibration of mosaic sensors, processing of flight data, and real-time laboratory simulations. Several of the present and planned test programs will be described along with examples of processed test data from infrared and visible CCD focal plane arrays.

An oscillating mirror is frequently used as a scan mechanism in thermal imagers. The correct location of the rotation axis to minimise unwanted displacements of a beam whose direction is being changed has been determined using a ray-tracing technique well suited to many problems in optomechanical scanner design. Numerical analysis reveals that a ray may be rotated by at least 20° about a point 10 units in front of a plane mirror if the mean deflection angle at the mirror is 120° and the rotation axis of the mirror is located 16.7 units in front and 5.8 units on the incidence side of the mirror.

We describe the construction, operation, and performance of a staring IRCCD focal plane that utilizes platinum silicide Schottky barrier diodes on p-type silicon as the infrared detector. The 25X50 element array is fabricated with standard integrated circuit grade silicon and uses an interline transfer scheme consisting of 25 vertical column buried channel CCD shift registers and one horizontal shift register. The device is operated at a temperature of about 80°K and is sensitive in the 1.2 to 4.5 pm spectral region. A signaL processor is also described which provides a non-interlace television compatible video signal from the IRCCD and interfaces with the normal drive electronics. The processor provides phase locked clocks and digitally derived control pulses for accurately synchronized signals to insure excellent video stability. Central to the design of this processor is a slow in/fast out CTD time compressor which allows the video signal to be displayed as a normal full field picture on a standard television monitor. We discuss the operation and characterization of the Schottky IRCCD imager including measurements of bias dependence of the transfer characteristic and device quantum yield. In addition, data are presented on thermal response, integration element size, transfer efficiency, MRT and noise characteristics. Future improvementsin Schottky IRCCD technology are discussed.

The spatial and spectral characteristics of the radiance from the earth atmosphere have been measured by a recent satellite experiment over the range 1100-2900 Å. This radiation forms the background for applications such as observation of targets or pollutants in the atmosphere. From the data acquired between April and September 1978 on a polar orbiting satellite, improved radiance levels can be given for a number of viewing conditions such as day maximum, night minimum, auroral zone, twilight, and night tropical airglow. The initial results from the data presently reduced indicate low levels in the day.Rayleigh scatter found at minima between Lyman-Birge-Hopfield bands of nitrogen between about 1400 and 1700 Å. Detailed spatial structure in the auroral regions indicate methods for day and night identifiption of disturbed atmospheric regions. The equatorial enhancement of atomic oxygen lines at 1304 and 1356 Å provides additional evidence linking vacuum ultraviolet observational techniques with ionospheric irregularities. The experiment consists of a spectrometer with either 1, 5, or 25 Å resolution and a VUV photometer with four interference filters and four fields of view. Radiance levels, spectrometer records, and global photometer profiles will be described as well as the relation of these observations to previous data and present aeronomical models.

This paper is a report on the progress of the Balloon Altitude Mosaic Measurements (BAMM) Program. The first report was given at the SPIE symposium in August 1977. Since that time, two flights have been conducted and approximately 14 hours of background data collected. This paper begins with a review of the BAMM objectives and experiment design as covered in the SPIE Proceedings, Vol. 124 (1977). As the program has matured, certain design changes have become necessary and these are described. Details of the two flights are covered with a summary of the data obtained. An outline of future plans is presented.

A simple digital recursion relation has been developed to restore images which have been degraded by the AC coupling characteristics of infrared imaging sensors. The recursion relation is derived and shown to be equivalent to inverse filtering. To indicate the magnitude of the distortion due to AC coupling the RMS deviation between input and output signals is calculated for a single rectangular pulse and a series of rectangular pulses. Examples of images before and after the recursive restoration process are shown.

The near-millimeter wavelength region (3.2mm - 0.3mm) is being investigated for military systems applications during adverse weather and in the presence of smokes, dust and other particulate clouds. The use of near-millimeter wavelengths (NMMW) has advantages and disadvantages relative to the use of the infrared and microwave regions. The atmosphere is a dominant factor in determining the operation of military systems in the NMMW region. Systems currently under consideration for NMMW applications include beam rider and command guidance, missile plume detectors, low-angle tracking radars, terminal homing systems, target acquisition radars, fuze systems, quasi-imaging radars and hybrid (IR/NMMW) systems. Recent NMMW technological developments (e. g., sources, receivers, components, phenomenology and measurements) have been advancing at a rapid pace to meet system needs.

A significant development in infrared measurement instrumentation is described. A high resolution (0.1 cm^-1) Block Engineering Fourier transform spectrometer (FTS) has been tailored for field measurements of atmospheric transmittance, and the emission from sources such as aircraft and rocket plumes, and high powered lasers. The instrument is described and a data example is given.

As indicated in Figure 1, the problem we are addressing is that of battlefield clutter due to the presence of aerosols which diffuse in the atmosphere under the action of wind turbulence and buoyant convectimi. We have a variety of aerosol sources such as dirt kicked up by explosions, dust clouds due to wind storms and vehicular motion, haze and fog, smoke from fires, and screening smokes. Each of these aerosol sources can contribute serious degradation to the operation of electro-optical systems. Our work has been directed towards describing and developing an understanding of the various aerosol source terms and their subsequent diffusion in the atmosphere. From this, we have been developing a disturbed IR transmission (DIRTRAN) model to describe the degradation effects produced by battlefield clutter.(1) Validation of this model is being performed with the aid of data obtained at several recent Army infrared obscuration field trials.

A Near Infrared Mapping Spectrometer (NIMS) will fly past Jupiter on the Galileo spacecraft in 1982. The infrared detector assembly (focal plane) used in the instrument is to be passively cooled to 80 K by radiation into space. The focal plane contains InSb and two silicon detectors, each with an associated dual J-FET preamp and feedback resistor. Preliminary fabrication and test experience will be described for an experimental five-channel hybrid detector assembly. At 80 K, a 5μ D* of 2 x 10¹³ has been demonstrated. Measurements of spectral noise density along with a plasma cleaning technique will also be described. The final NIMS focal plane will contain much of the design experience gained from the experimental hybrid detector assembly.

Measurements of infrared (2.7-μm) source positions and flux densities have been derived based on an additional 60.6 hours of satellite observations beyond those considered in the preparation of the Equatorial Infrared Catalogue No. 1 (EIC-1). These data have been processed together with the EIC-1 data to produce EIC-2. The new catalogue differs from EIC-1 as follows: there are 1278 sources (vs. 896 in EIC-1); there is a larger percentage of unidentified sources (17% vs. 10%); there are increased numbers of sources identified with Two-Micron Sky Survey sources (101 more than in EIC-1), AFGL sources (38 more), AGK3 stars (91 more) and SAO stars (187 more).

The S-192 conical multispectral scanner, which acquired data during the 1973-1974 Skylab mission, represents one of the best sources of high resolution medium and long wave infrared data obtained by a space based sensor. The 2.1-2.35 pm and 10.2-12.5 pm spectral bands are of considerable interest since they represent spectral bands or resolutions not available from LANDSAT, DMSP, or HCMM. In this study, four S-192 data sets were investigated from the viewpoint of the statistical properties of the scenes themselves. These S-192 data sets contained scene data not normally acquired by aircraft-based remote sensors, but of interest to many applications. Represented in the data sets were: several cloud types, coastal mountains, snow covered mountains and valleys, and ocean backgrounds. The data sets were studied by choosing areas of homogeneous background and obtaining the power spectral density (PSD). The statistics of like areas were compared. Particularly of interest was the effect of clouds, both optically thin and thick, on the statistics of terrain backgrounds. In this paper, PSDs based on Skylab S-192 will be presented and infrared and statistical measures for specific background classes will be discussed.

A wide band laser modulator is designed on the basis of electro-optic modulation principle. A trgvelling wave mode is adopted. A piece of 3x3x80 mm³ single crystal GaAs is used as the modulating crystal. The output power from the high frequency generator'is over 250W with 50ohm output impedance in the frequency range of 30 MHz to 400 MHz. The electrical matching between the modUlator and the generator is good. The bandwidth of the modulator is measured to be 400 MHz. Intensity modulation experiments are performed with a CO₂ laser. High frequency HgCdTe infrared detectors in metal dewar are measured with this system to have a time constant below 1 ns.

An infrared forest fire alarm for surveillance of initial small forest fire is described. It is made up of a reflective opto-mechanical scanning system and a display unit with an audible alarm. The scanning system is controlled by an automatic mechanism which makes the Spiral scanning proceeds continuously from 0 to 12 degrees in'elevation and vice verse. The optics with an IFOV of 1 mr scans 360degrees in azimuth. The design assures that the radiant beam from the target falls stably on the thertoelectridally cooled HgCdTe detector which is situated in the center of the rotating axis. The spectral filter before the detector suppresses all background radiation below 3 um. The display unit is consisted of a CRT 'screen and a loudspeaker. The target can be displayed by two selectable modes: a light spot on the screen to indicate the position of the target or a waveform to show the amplitude of the signal. The audio frequency used is 400hz. The scanning system and the display unit can be mounted together or separately with a distance of 1 km. For example, the former can be located on a hill top and the latter situated at the foot of that hill with a cable linking the two.

A passive system for the classification of isolated infrared signatures is briefly described. The hardware consists of magnifying optics,infrared filters and a beam splitter. The detector is a specially designed array consisting of two crosses 45° apart , with 8 or 16 pyroelectric detectors on each of the eight radial directions. The classification hardware consists in an analog parallel read-out and amplification,followed by a digital processor . The feature parameters by which the I.R. signature is classified into 6 alternative classes are : distributions of the detector outputs along each of the 8 radial directions,iso-radiation contours of the apparent picture of the source, and global I.R. emiss-on in two wavelength bands . Experimental as well as simulation results have been obtained .

This review describes the sources and optical components used in infrared spectrometers, analysers, pyrometers and thermal sensors, particularly in relation to their use in industrial applications. Attention is drawn to those areas where improvements would be desirable.

The basic theory of Kubelka and Munk for diffuse reflectance from powdered solids is critically examined for its applicability to quantitative analysis in the near-infrared region of the spectrum (0.5-2.5μm). The effect of regular reflection, layer thickness, particle size, moisture, background absorption, and other aspects are considered, and the implications for available methods used for such analytical measurements are discussed. Examples are presented of severe departures from expected behaviour (i.e. irregular analytical calibration curves), and it is shown that these 'anomalies' arise from inexact definition of the nature of the species being measured.

Two new automatic control systems for paper machines are described. The first is concerned with moisture variations across the width of the paper machine using variable crown rolls in the press section to level the profile. The theory of variable crown rolls, control strategy and operating experience are discussed. The system makes use of the "true" moisture profile to calculate optimum conditions for minimizing the moisture profile variability. The measurements are provided by a scanning on-line infrared gauge. SADACOLOR, the second control system to be described is based on Reed's original stand-alone sampled data controller SADAC, but includes colour display of cross machine variables and multirate sample and control techniques. The successful application of these techniques has led us to develop a new stand-alone sampled data controller SADAC-M which is microprocessor based and should have a wide industrial appeal.

Infrared technology finds many applications in the field of combustion, ranging from pollution monitoring, through military systems, to the control of industrial furnaces and boilers. This review of some selected concepts highlights the interaction between the diagnostic role of infrared measurements and the current status of mathematical modelling of combustion systems. The link between measurement and computing has also evolved to the point where a digital processor is becoming an inherent part of many new instruments. This point is illustrated by reference to the diffraction particle size meter, fire detection and alarm systems, and furnace control. In the future, as fuels become scarce and expensive, and micro-electronics become more available and inexpensive, it is certain that infra-red devices will find increasing application in smaller industries and the home.

The principal markets that exist for industrial infrared systems are considered. There is a discussion on the relevance of detector figures of merit and specifications. The particular needs of each part of the industrial market - consisting of thermal imaging, pyrometry, intruder alarms, flame and fire detectors, and process composition analysers - are summarised. Individual detectors are then considered, but this is restricted to types of known industrial application, and the limitations and advantages of each one listed. There is a brief discussion of amplifying and cooling requirements.

In the past twenty years, great technological advances have occurred in the fields of non-contact infra-red thermometry and fibre optic production. This paper will show how the two areas have overlapped resulting in the manufacture of industrial temperature measuring systems using fibre optic light guides.

Radiation thermometry can be used to measure the thermal conductivities of many solids and also the thermal resistances at interfaces of solids. Results are given for a diamond and a silicon sample and also for a sample of diamond and tungsten carbide brazed together.

The characteristic properties of the tunable solid state infrared laser sources: spinflip Raman lasers, optically pumped solid state tunable lasers, optical parametric oscillators, nonlinear frequency converters and semiconductor diode lasers are compared and their working principles are briefly discussed. Emphasis is put on systems which are already commercially available or which show promise for future applications. The use of diode lasers in ultrafine spectroscopy and pollution monitoring is reviewed.

Optical coatings are required in the infra red for mirrors, anti-reflection coatings, filters and radiation absorbers. The most widely used optical coating technique is vacuum evaporation and its variant reactive evaporation. These are employed for depositing films of metals and oxide sulphide and halide compounds. Thermal evaporation imposes limitations on usable materials for reasons of compound dissociation or low volatility as for refractory metals. Evaporation in ionized activated gas can aid growth of stoichiometric compound films. Also developments in magnetron sputtering harq raised sputtering and deposition rates and with r.f. sputtering extended the range of film materials but surface damage can result when coating solid state devices from impact of energetic particles in the discharge. The foregoing processes are physical in their material emission and condensation mechanisms. Reeen4].y increased attention has bean given to chemical deposition processes in which a glow discharge is used at low gas temperature to initiate or accelerate dissociation of a gaseous compound or reaction between gases in a mixture. The work of the writer and that of others on three types of plasma deposition processes is reviewed. The processes which afford film thickness growth rates of several hundred angstrUms per minute are: plasma polymerization of hydrocatbonoilicone and fluorocarbon gases, the growth of amorphous carbon and silicon films in hydrocarbon and silane plasmas respectively and the formation of oxides and nitrides by plasma gas reactions. These processes have potential use for preparing anti-reflection films (e.g. a C-films on Ge) and polymer moisture protective films on halide crystals. Finally it is proposed that interference systems based on a Si/a C-layers could be made by plasma chemical processes.

This paper describes a novel method of stress determination in structures under dynamic loading conditions. The principle is based on the thermodynamic property of a material in which, under adiabatic conditions, heat is produced or absorbed in direct proportion to the magnitude of the stresses to which it is being subjected. An instrument is described which uses infra-red radiation to measure, remotely, the resulting minute local temperature changes in the material, with oscillating mirrors to provide a raster type scan of the item under test. Spatial resolution down to 1 mm and a temperature discrimination of about 0.002 °C have been achieved, this latter representing a stress change of less than 300 lb/in² in steel.

Work at RSRE on the optical and signal processing techniques of CO₂ laser velocimetry is described together with recent applications at the Royal Aircraft Establishment Bedford and the Drax power station. The present capabilities of the method for remote sensing of the atmosphere in the contexts of study of atmospheric turbulence and wind shear, building wakes and pollution dispersal are outlined. The future potential for measurement from aircraft of true airspeed, shear warning and clear air turbulence is discussed.