Over a year ago, I was asked by SPIE to serve as Guest Editor for an issue on applications of infrared technology. Inasmuch as infrared technology is being used in more and varied applications every day, the task of identifying the specific applications to be included in this issue was difficult. Suggestions were solicited from a number of people in the field regarding the composition of this issue. From their responses, it became readily apparent that interest existed in discussing applications of infrared technology from the view-point of a system engineer. Also, it seemed appropriate to discuss certain components from the same view-point. Personally, I found this concept intriguing in that what is often of interest to the component engi-neer may not be of major significance to the system engineer. The system engineer generally desires to know how a given component will affect the design and performance of a particular system. The paper by Dr. Barhydt on the performance of nearly-Blip detectors exemplifies this point of view. In any case, each author was encouraged to write his paper for the infrared system engineer.
Application of infrared technology to problems in a systems engineering effort must be based upon an understanding of target-background-atmospheric radiation interactions as well as electro-optical systems and their components. This paper presents a brief tutorial review of these fundamentals in a treatment derived from the long-standing University of Michigan Engineering Summer Conference and ERIM's short course on this topic.
This paper addresses the problem of the sensor engineer to determine what actual performance he might expect from a real (non-ideal) photodetector and how his sensor design may affect that performance. The paper shows the relationship between the external electrical parameters of the detector and its internal parameters and how these internal parameters may be deduced from the electrical measurements. The paper shows how geometrical and spectral shielding of the detector affects the sensor performance and how the detector performance when mounted in the sensor may differ from that measured on the detector test bench. The conditions where the detectivity may exceed the "classical" theoretical limit for photoconductors are derived. Finally, the theoretical ideas developed are applied to actual HgCdTe detectors in a practical illustration.
Pyroelectric vidicons (PEV) are low-cost, infrared TV camera tubes which operate at room temperature. They image in any wavelength band within the 2-400 /.1M range. For the 8-14 band, the PEV has a typical Minimum Resolvable Temperature (MRT) of less than 1C at 250 TVL. When operated with increased pedestal current, the MRT can be reduced to 0.6C at 250 TVL. This paper reviews the significant parameters of the PEV, viz., electron-beam discharge lag, sensitivity, and thermal spread in the target, and some applications. These include fire location (specifically, forest fire mapping), security, industrial uses, and medical diagnostics. Forest fire mapping has been cooperatively done by Philips Laboratories and the Canadian Forestry Service. During that exercise, local sources of burning totally obscured by smoke were readily located by the PEV system. The unique ability of the PEV to detect motion lends itself to security applications. A chopping and storage mode of operation has been developed for industrial and medical applications. With this technique, the integrated signal from several frames can be displayed as a static image. Images of a circuit board show components operating at elevated temperatures. Veinal structures in various parts of the human body have been easily imaged with this system.
Mirrors with very low-scattering optical surfaces (BRDF <1 x 10-5 sr-1) are being used in military applications. Energy scattered from dust particles on the surface of these mirrors can cause a degradation of the performance of the sensor. A study was made to determine the effect of particle contaminant on the mirror-scattering properties. The study involved contaminating low-scatter mirrors, characterization of the contamination level, and measurement of the Bidirectional Reflectance Distribution Function (BRDF). Comparison of experimental measurements was made with values of BRDF predicted by the Mie particle-scattering theory.
The optical properties of the atmosphere are important considerations in the design of infrared remote sensing systems. For example, the selections of the appropriate spectral region, spectral resolution or filter bandpass and the calculations of system performance all require data on background radiance and atmospheric transmittance. This paper will present previously unpublished high resolution (0.07, 0.44 cm-1) measured and computer modeled atmospheric transmittance and sky radiance data in the infrared. Included also is discussion of measurement methods and calculation procedures.
Performance models can be used to design systems to meet specific applications, evaluate competitive designs, or direct research into areas of potentially large payoffs in system performance. This paper presents a validated performance model for thermal imaging devices, where performance is defined as static (non-time varying) detection, recognition and identification as a function of target range. The target, atmosphere, device, and subjective observer behavior are described by mathematical equations which result in predictions of system noise equivalent temperature, minimum resolvable temperature and minimum detectable temperature. Detection, recognition, and identification are then based on these quantities through experimentally determined algorithms using required signal-to-noise ratio and subjective resolution.
A guide to preparing specifications for thermal imaging systems has been prepared by a tri-service working group under the sponsorship of the Joint Technical Coordinating Group-Thermal Imaging Systems (JTCG-TIS). The document covers all phases of system development from advanced development through production prototypes. It acts as a guide for imaging system requirements and the quality assurance test procedures necessary to check those requirements. Because of the length of this document a short synopsis has been prepared. Emphasis in this synopsis is placed on imaging quality requirements with MRT as an example to describe both the limitations and versatility of using the overall tri-service document. This shorter paper should aid in making the thermal imager community aware of the tri-service guide while describing its content and how it might be used.
The presentation of the history of radiometry is divided into two periods separated by 1959, the year that the first laser was reported. In contrast to the coverage of the second period which relies heavily on the original sources, the coverage of the first period relies mostly on review material. The presentation is slanted toward work reported in the English language. This is particularly true of the second period. The presentation also tends to emphasize radiometric standards.
This paper is a status report covering the development of detector-based standards for optical calibration. It briefly treats, in historical perspective, the philosophy and technology underlying the use of detectors as standards and assesses the impact of recent technological developments. Next, the development and operation of the Electrically Calibrated Pyroelectric Radiometer (ECPR) are described, and the methods used to characterize this instrument are outlined. Finally, we review the present capabilities of the ECPR and summarize some of the measurements to which it has been applied.
The AEDC infrared (IR) test facilities include several equipment assemblies: a 7 foot diameter low background sensor performance evaluation and calibration chamber, a sensor out-of-field rejection measurement system, mirror scatter measurement apparatus, and a sensor closed-loop control system test capability. These facilities, their optics, and the IR radiation sources used are described, along with improvements currently in work or planned.
The objective of the investigation described here was to determine the feasibility of an infrared (8-14 pm) scene simulation concept; the concept is called a PTS (Passive Thermal Screen). It is passive because it does not contain any heat generating elements, but receives its energy from a visible image that is cast upon its working surface by a slide (or motion picture) projector, instead. Measurement data presented show that thermal contrasts of up to 16 C can be produced using bar pattern images and an input irradiance of 0.09 W/cm2. Contrast and temporal response measurements were made using a Thermo-vision infrared imaging camera (and display) in combination with a magnetic-disc recorder. The most severe problem area that remains before the concept can be put to practical use as part of a full-scale IR simulator is that of producing input slides that can accommodate the high radiance levels required of the projector.
The scalar theory of microdensitometer performance developed in previous papers is revised and expanded to include coherent illumination. The central ideas of scalar microdensitometry are combined from several basic sources and summarized ; this paper serves as a convenient single source of microdensitometer theory. Eight distinct variations of instrument configuration and operation are identified, and the image characteristics and conditions for linear microdensitometry are developed for each. The concept of effective incoherence is summarized and discussed. Further consideration of the problems associated with aperture sizes, determination of the sampling aperture size and image vs sample scanning are presented. An experimental test program, carried out with the Mann-Data Microanalyzer, by experienced operators, under closely controlled conditions to test the theory, is reported. Among the conclusions is that the instrument manifests its best performance with overfilled optics and sample scanning, and that an increased reduction factor on the influx side would be useful with image scanning. Several fundamental problems surface during the course of the investigation. These are discussed and the need for further study in certain areas is emphasized.
Slotted aperture filter masks can be used to "tune" a photographic system to an integral multiple of a fundamental grating frequency. Such a procedure can be used in moire photography for multiplying sensitivity and for obtaining improved rendering of fringe patterns. Depth of field is increased, and a camera lens of poorer quality than is normally required for high resolution photography of moire gratings is adequate. Also gained is flexibility in optical data processing of moire photographs and in the use of two-dimensional grid and dot specimen arrays.
This column is a review of the seminar on Modern Utilization of Infrared Technology, which was held in San Diego on August 26-27, 1976. Separate sessions were devoted to (I) Infrared Astronomy, Captain Robert H. Weber, USAF(SAMSO), Chairman; (2) Infrared Methodology as Applied to Environmental Monitoring, Claus B. Ludwig, Science Applications, Inc., Chairman; (3) Military Applications, Captain Howard Stears, USAF(SAMS0), Chairman; (4) Infrared Applications, I.J. Spiro, Chairman. These sessions presented recent advancements in infrared astronomical instruments, methods of data processing, astronomical measurements, environmental monitoring instruments and techniques, charged coupled devices, and detectors, as well as many civilian and military applications.