The ability of the eye to distinguish different colors is clearly an important source of information gathering. It has long been recognized that infrared systems would profit greatly by such an ability in areas such as target acquisition and identification, clutter and decoy rejection. No technology, however, has as yet emerged which could offer this capability at an affordable cost to most weapon systems. The present in-house program has been successful in demonstrating a new technical approach to multi-color infrared systems which is simple, straightforward and inexpensive. The new technology is based upon multilayers of thin epitaxial film detectors sandwiched in small dots, each dot being capable of detecting three or more infrared colors.

Pyroelectric detectors have been developed at Los Alamos Scientific Laboratory (LASL) for use with high-frequency applications such as laser fusion. Less than 50 ps total response time devices have been measured, The voltage responsivity with a 50-Ω load is abut 5 to 10 V/MW, requiring 10 to 20 mJ/cm² to poduce 1-V, 1-ns pulses. The latter are 1 mm in area. High-speed devices with up to 1 cm² area have been developed. A novel method of fabrication now permits voltage responsivities up to 50 V/MW with a 50-Ω load. This improved sensitivity detector is slower than the fastest design but is still suitable for measuring 1-ns pulses.

Infrared detectors for operation at intermediate cold temperatures (190°K to 270°K) are finding many applications in night sights, airborne tracking systems, shipboard trackers and night viewing devices. Detectors, such as lead sulfide, lead selenide, photoconductive mercury cadmium telluride, and photovoltaic mercury cadmium telluride in single-element or array configurations, are well suited to such systems, and thermoelectric coolers are one convenient method of producing the required operating temperatures for these detectors. Recent advances in coolers, packages, and detectors have brought this total technology to a point of high reliability, long vacuum life, and higher detector sensitivity. This paper shows some of the options and tradeoffs which are open to the system designer for thermoelectrically cooled infrared devices.

A broad-area optical lightning telescope sensor (BOLTS) has been designed to provide full-time (day/night) coverage of the continental United States from a geosynchronous orbit. The average ground resolution will be 8 km and the probability of detecting 107 watt lightning strokes will be 0.9 with a false alarm rate (FAR) of 0.1. The system's requirements and constraints are presented together with the design rationale. Contrast enhancement is achieved with a fast refractive optical system incorporating a relatively narrow bandpass interference filter. The focal plane is an 800 x 800 pixel CCD array, electronically subdivided to allow for the high data rates (1000 frames per sec) imposed by the short duration and random occurrence of lightning flashes. A subtraction algorithm using similar CCD arrays as buffer memory provides the cluttered background filtration. The emerging data are subjected to a threshold test, and signals above threshold are encoded with respect to time, location, and intensity, and are transmitted to the ground station. Variations of this system are discussed that could cover the whole globe from several geo-synchronous satellites or that could cover a smaller U.S. area with a higher resolution.

Voltage noise measurements have been made at temperatures from 77 to 150 K with three JFET's and a preamplifier which closely resembles one used with InSb photovoltaic detectors. noise minima were detected with the three JFET's at temperatures of 100-115 K, but the level Df voltage noise for two of the three JFET's was found to be below the noise level of InSb detector systems.

A mathematical model is given for a frequency-compensated detector/preamplifier appropriate for cryogenically-cooled infrared sensors operating under low background conditions. By use of a digital computer, this model is used to rapidly select the optimal combination of design values. These parameters include load resistance, compensation resistance, com-pensation capacitance, chopping frequency and detector area to meet desired specifications of noise equivalent power, frequency response, dynamic range, and level of output noise. This computer-aided optimal design approach is demonstrated using a contemporary infrared sensor application.

An electrochemically deposited LiTa0₃ thin film and detector, a room-temperature photoconductive HgCdTe detector, a PbSnTe detector and a lead sulfide detector are described. Also mentioned are a two-color thermometer and a multi-spectral scanner which may find potential application in remote sensing.

The paper describes a fourth-generation liquid-helium-cooled medium wavelength infrared spectrometer. The sensor incorporates a rotating circular-variable filter to scan the 2 to 22.5 pm range at =2% resolution. The spectrometer design is optimized for high throughput and low background measurements and hardened for upper atmospheric measurements aboard sounding rockets. Two of the significant new features of the sensor are totally reflective cold optics and the use of a vibrating-reed chopper. These advances led to a 30% reduction in size and weight, 50% increase in hold time, five times increased sensitivity, spectrally independent field of view and 100% improvement in linearity of response.

Optical thin films which are electrically conductive, (EC), are finding increasing use in infrared instruments. This paper describes three application examples in which three different functions are performed by the EC coating. One example describes an electro-magnetic shielding application of an EC coating on IR sensor windows. Example two, discusses a deicing/defogging application on the XM-1 tank laser (1.06 μm) range finder window. The third example describes an unusual EC coating application as a 655 nm/10.6 μm beamsplitter for an advanced CO₂ laser range finder system.

This paper will discuss the spectral and optical effects of coating ninholes, coating spatter, scratches, and digs. Limits to minimum physical filter dimensions will be presented. The advantages and disadvantages of alternate methods of miniature filter fabrication will be discussed.

PbTe is unique amongst coating materials because of its negative temperature coefficient of refractive index. In combination with a conventional II-VII) material it can confer immunity to temperature variation from at least -23^oC to +110^oC for a narrowband filter. It also has an absolutely large refractive index so that filters are attainable with minimal degradation when tilted, and a minimum number of layers overall particularly towards 20 µm. Excellent transmission can be obtained.

During the past several years, the Optical Signatures Technology Group of the Boeing Military Airplane Company has created an experimental facility for the measurement of infrared radiation from jet engine exhaust systems. Using the Large Test Chamber (LTC) of the Boeing Commercial Airplane Company, the largest anechoic propulsion chamber in the United States, a capability for obtaining a large variety of data on the infrared signatures of exhaust systems has been developed. A preliminary test was conducted in 1978; this test demonstrated that the LTC was highly suitable for such measurements and provided information for facility development and additional equipment purchase. Another test in 1979 fully validated the LTC as a facility for infrared signature measurements and provided extensive data on several nozzle and mixer configurations.

A variety of difficulties have been encountered while testing diamond turned optics with a standard HeNe interferometer. This is especially true in multiple-pass test configurations, where scattering and moire' effects create an ambiguity in interpretation of the interferogram, making slope error and finish determina-tion difficult if not impossible. In a production environment it is also desirable to speed inspection and "buy-off" by viewing the surface at the wavelength of use, namely in the 8-12 micron region. A 10.6 micron laser unequal path interferometer was designed and built to satisfy these needs. Zinc selenide optics are used throughout to facilitate alignment in the visible and allow expansion to near infrared wavelengths in the future. The output is displayed on a TV monitor through the use of a pyroelectric vidicon(PEV). Examples are given of standard interferometric tests in the IR as compared to visible interferograms, clearly showing the reduced effects of surface errors.

Michelson interferometers used in airborne measurements of infrared emissions are described in the context of their mechanical and electromechanical characteristics. Methods of coping with the harsh aircraft environment of high vibration and unstable cabin tempera-tures are described. The use of position sensing servo drives, flexure pivots in the moving mirror transport system, and piezoelectric crystal auto-alignment of stationary mirrors is also described. The newest interferometer to be placed in service is described with regard to its sliding piston mirror drive and associated electronic control systems. This instrument has already provided promising spectra with 0.125 cm^-1 resolution.

A lead sulphide (PbS) sixteen detector (4 x 4 array) multiple filter radiometer suitable for balloon borne platforms was developed by Electro-Dynamics Laboratories at Utah State University. The hostile environment associated with balloon borne systems required that thermal, electrical interface, stabilization, and atmospheric problems be studied. The radiometer design deals mainly with instrument requirements.

A TAOF combination radiometer/spectrometer covering the 2 to 5 micron range with a 7 cm^-1 constant resolution across the band has been designed and constructed. The instrument is computer controlled, capable of acquiring and reducing data at a faster rate than conventional grating spectrometers and radiometers. It has been extensively evaluated in the laboratory, and has been used to acquire the spectra of a rocket in the field.

Thermographic inspection is an invaluable diagnostic technique for detecting thermal abnormalities indicative of failure mechanisms in current-carrying equipment. No other maintenance procedure can provide such fast and accurate evaluation of the operating con-dition of electrical apparatus. Infrared line scanners and infrared imagers are both used successfully for thermographic inspection surveys. Each system has certain advantages and disadvantages. The Barnes Thermatrace single-line scanner and the AGA Thermovision 750 imager are compared. Periodic thermographic inspection surveys in commercial and industrial plants substantially reduce the frequency of equipment failures and unscheduled power outages. Proper planning and organization increases the efficiency of a survey and reduces the cost. Several examples illustrate some of the types of failure mechanisms frequently encountered.

The pyroelectric vidicon television camera has had its utility extended from the laboratory environment to field use by the development of a portable camera system. These systems are battery powered, light weight, and extremely mobile. This development has greatly increased the applications of the pyroelectric television systems. These systems offer complete compatibility with existing video equipment such as monitors, video tape recorders, and image analysis systems.

As applications for infrared imagery continue to expand, the need for extracting more data from each image increases. Today, the primary goal of commercial infrared imagery is to provide a means to measure thermally related phenomenon about an object under test. The thermal information may be static or dynamic, but in many cases, it is very complex. Digital analysis offers time saving opportunities to reduce complex thermal data into a meaningful but also simplified format. The heart of the digital analysis is the analog to digital (A/D) conversion and storage that interfaces between the infrared world and the computer world. On the digital side two alternatives exsists: Mini-computer and Microprocessor. Each has distinct advantages and dis-advantages, which must be considered by the end user. Future developments will probably involve still greater use of Microprocessors that will be more dedicated to specific applications

Between the "qualitative" use areas of infrared thermography (hot spot detection, etc.) and those which require the determination of precise thermal values lies an intermediate or semi-quantitative area of considerable utility. Use of relatively inexpensive auxiliary equipment to "colorize" the primary infrared scanner image is a practical mode of operating in this area and two industrial examples are discussed.

An existing Barnes Engineering,Inc, slow scanning infrared spectral imaging system has been modified to accent an ultraviolet detector, thereby allowing for a two channel ultra-violet or infrared imagery acquisition system. The infrared optical channel has been al-tered to accept a beam splitter for redirecting ultraviolet scenery and transmitting infrared scenery. The ultraviolet optical channel further incorporates a relay lens, optical filters, and a photomultiplier tube detector. The imagery system controller has been changed to allow for interfacing to several data acquisition systems for increased mission flexibility. In existing data acquisition control system program has been modified to acquire and record data on computer compatible digital tape. Digital image data and synchronizing signals were extended from the original Barnes interface and made available for use by an external digital video real-time display. Existing data editing programs were rewritten to accommodate imagery data, and data reduction programs were written for gray level data reduction. Preliminary ultraviolet and infrared measurements have been conducted with some apparent optical performance and throughput degradations in the ultraviolet channel. References to ultraviolet negative/positive contrasts, atmospheric effects, and system optical performance were analyzed. Video and computer reduced gray scale plots have been acquired, and photographs of video gray scale scenery are presented.

This paper discusses the capabilities and limitations of a pyroelectric vidicon camera used to profile 10 lisec CO₂ laser pulses. Points examined include dynamic range, signal-to-noise ratio capabilities, spatial resolution capabilities, uniformity of sensitivity, maximum faceplate irradiance, and required EMI and RF shielding. The relationship between camera performance and pulse length is also discussed. Samples of data acquired and requirements of an adequate data processing system are presented.