A variety of modern test equipment is available to measure the NEDT, SITF, MRT, and MTF of thermal imaging systems. Since this equipment processes data in the digital domain, it may introduce artifacts such as image blurring, uncertainty in edge location and aliasing. These effects are pronounced in undersampled situations which may be encountered with frame grabbers or image analyzers. Although the performance measures are usually specified in terms of target-background temperature differential, thermal imaging systems respond to power or photon differences. Since power differences are not linearly related to temperature differences, the NEDT, SITF and MRT are functions of the ambient temperature.

This paper reviews automated methods and procedures used in the final stages of Thematic Mapper dynamic testing. The Thematic Mapper (TM) is a scanning, multispectral mapping radiometer having a 16 inch aperture and a focal plane array of 100 detectors covering 7 spectral bands. From a polar orbit of 705 km., TM scans a ground track 185 km. wide, using an oscillating plane mirror to view the earth surface. The scan mirror is attached to the telescope frame, raising the possibility of coupling significant vibration displacements into the electro-optical system. An important aspect of TM dynamic spatial testing (in vacuum) was to determine deviations from ideal spatial performance, as might be influenced by scan mirror operation, in the following areas: (1) Channel-to-channel (cross-scan) IFOV registration. (2) Spectral band-to-band (along scan) IFOV registration. (3) Scan slope and linearity in two directions. (4) Vibration-induced scan-to-scan IFOV footprint jitter. By designing a suitable test arrangement and software, as well as a unique two-dimensional reticle pattern, it was possible to automatically collect and analyze a composite data set which provided all of the above measurements, and demonstrated that system performance in these areas was within specifications.

The minimum resolvable temperature (MRT) is an important thermal imager performance measure. A desire to automate this subjective test has several motivations: no trained observer would be required, the test would have better repeatability between different observers and facilities, and the test flow of an automated computer controlled test station would not be interrupted by operator inputs. A figure of merit calculated from digitized video frames at multiple blackbody temperatures was related to a simultaneous subjective measurement using a linear scale factor. A measurement data base was compiled which gives a surprisingly good correspondence to subjective measurements over a wide range of conditions.

The test and support of Electro-Optical (EO) systems introduces numerous unique demands that are not encountered when testing other types of equipment. This demand is amplified when test and support is undertaken using automated test techniques or Automatic Test Equipment (ATE). This latter case is increasingly becoming not only the method of choice but the method of necessity as EO systems become increasingly complex. This paper will acquaint the reader with some of the special requirements that are encountered when testing and/or supporting EO systems. It will concentrate on automatic testing and illustrate how the demands of EO testing were successfully satisfied particularly as regards software methods and techniques needed for EO systems using ATE within the DoD environment.

This paper describes the principles of supporting Electro-Optical equipment, and three types of Test Systems used for factory and field testing of FLIR and Multi-Sensor systems. The tests performed by one of these systems are: FOV, Focusing, Boresight various L.O.S., MRTD, NEI, Laser Power level, Laser Mapping and ATR. I will emphasize special considerations implemented for optical performance in field conditions, and for enhanced automation and realism of the test process. (Dynamic MRT, and Scene Simulation capabilities). The paper will describe a system for testing a sensor with TV, NIR, FLIR and laser designators-targeting rangers.

A three-mirror unobstructed all-reflective f/2.7, 12-inch focal length, 3° circular field laboratory telescope requiring 80% of encircled energy in a spot size of 65 micrometers at 10 micron wavelength was designed, manufactured, and assembled by the Contraves Goerz Corporation. The design and optimization methods for this off axis system and the computer assisted techniques for assembly and alignments of the telescope are described. The method of testing the secondary convex mirror, with aspheric terms to 10th order, and the oblate spheroid concave tertiary are of interest. The finished telescope was tested by interferometry by the Boeing Aerospace Company's Optics Group. A Zygo Mark III Fizeau interferometer measured the optical path difference (OPD's) and the ACCOSV lens design/analysis program computed the OPD's from the telescope prescription. The OPD's from the ZYGO were passed to a Perkin Elmer 3200 mini computer for data reduction. The measured and computed wavefronts were analyzed by Zernike polynomial least-squares fitting in the U. of Arizona FRINGE program. The combining and enhancing of several optical programs in a single computer provided flexibility and increased capability. Both measured and design wavefronts are plotted and tables of aberrations are given at each field position. Point spread functions and encircled energy are computed at several wavelengths. The telescope design performance is limited by astigmatism. All five field positions showed coma as the dominant aberration when measured by interferometry.

The effects of background temperature changes and detector spectral characteristics on apparent blackbody temperature are analyzed. The error sources are quantified for representative thermal imaging system detector spectral responses and system optical bandpass. In addition, a method is presented for correcting background temperature variations for each of the detector responses.

This paper describes a method developed for precompensating the front-end (telescope) optical alignment of the Imager and Sounder radiometric instruments, which will be launched as components of the GOES I - M series of meteorological satellites. To satisfy the severe pointing accuracy requirements on these instruments, their alignments must be offset in the one - G field of the laboratory, in order that they will be correct in orbit. A method was developed to make the necessary alignment offset, using a counterweight mechanism; autocollimation returns frau reference mirrors on the instrument structure and supporting fixturing provided feedback for adjusting the counterweight mechanism. A series of experiments was performed to verify that these autocollimation return measurements were a good predictor of telescope line-of-sight changes; these experiments are described and their results summarized.

A non-contact optical means of accurately measuring the separation between a single-mode fiber and laser diode chip is presented along with the method to automatically set the gap separation to any pre-determined distance or to lock-in on the maximum light level. The procedure also provides a fail-safe mechanism to avoid the serious problem of running the fiber into the chip. The method will work with any size chip and any geometrically shaped fiber (from lensed to cleaved). The accuracy of the method is a function of the mechanical tolerances of the alignment machine plus the alignment of the chip with +3, -.5 micron being typical and +1, -.2 micron being state of the art.

The Advanced Sensors Directorate of the Army Missile Command's Research, Development, and Engineering Center (RD&EC) provides specialized technical support to the HELLFIRE and COPPERHEAD Project Offices for the HELLFIRE missile, the COPPERHEAD projectile, and ground laser designators. The HELLFIRE and COPPERHEAD laser seekers are supported by RD&EC's Automated Laser Seeker Performance Evaluation System (ALSPES). This facility was conceived by RD&EC engi-neers and put into operation in 1978. Laser energy incident from different angles test the seeker's ability to track target reflections; while multiple lasers aimed at the seeker test the false target rejection capability of the seeker. The following tests can be performed on the seeker from a computerized test console: spin-up time, scan pattern, threshold sensitivity, AGC calibration, transfer function, static track rate error, guidance noise, gimbal angle linearity, dynamic boresight shift, correlation/decorrelation logic, last pulse logic (false target discrimination), field-of-view, frequency response, guidance noise vs energy, and gyro drift. The 15 characterization tests can be accomplished in approximately 4 hours using this computerized facility. The ALSPES has identified several design abnormalities in laser seekers, resulting in corrective actions that have increased system performance and reliability.

Avionic systems are incorporating an increasing amount of fiber optics. FORTE is a 6.2 R&D program developed atthe Naval Air Engineering Center (NAVATRENGCEN) to support fiber optic avionic systems. In the 4th quarter FY85 an electro-optical test device design was initiated. The design is required to be modular, digitally controlled and fully duplexed. FORTE will be utilized in automatic test equipment as an "asset" to handle the optical signal portion of testing. The Breadboarding phase of the design has been completed and the brassboard is under fabrication. The system capabilities are three bidirectional independent channels at 820nm, 860nm and 1300nm. The fiber size is 100/140nm GRIN Multimode. Programmability is achieved through the IEEE-488 interface bus. One of the future directions of the program is to build an in-house capability, with lab facilities to support, maintain and develop fiber optic systems. Follow-on work will constitute a fiber optic system requirements analysis with fiber optic application and their fault modes. This will be followed by a development program to augment the current brassboard.

A specific application of ATE to laser optical measurements is discussed including the measurement requirements, selection of available computer and peripheral equipment, identification of any special equipment to be fabricated and computer language limitations. As the ATE is developed, hardware and software choices are made to maximize the speed, accuracy and reliability of the measurements. The application is completed with a brief summary of equipment performance in use.

The software and computing power of the WYKO LADITE interferometer make it a desirable tool in applications that are outside the factory set wavelength. However, the focus shift involved in going from the factory set wavelength to, for example, Nd:YAG's 1.06 micron line introduces systematic errors. This paper describes a method to refocus the commercially available instrument without compromising measurement accuracy. This modification allowed testing of a high quality laser system at its operational wavelength.

The vibration of the spindle system of the diamond turning lathe has a great influence on the geometry of workpieces. The low frequency vibration will distort form of the workpieces, and the high frequency vibration will damage finish of them. The author has developed a optical method for testing form and roughness of optical surfaces simultans., eously. By using this method, the form and the roughness of the diamond turned surfaces is tested, the readings are sent to microcomputer, the relation between the frequency characters of the spindle system vibration and the power spectrum of the form and roughness of the diamond turned surfaces are set up by FFT analysis. This is a simple, high speed, automated, and non-destructive testing technique, and workpieces needn't removing from the lathe. So that it is easy to realize on-line monitoring of the diamond turned surfaces by means of this technique. Furthermore it is possible to diagnose the diamond turning lathe by using this method.

As a result of air bearing and CNC technique, the diamond turning machine can cut the optical surfaces in very high accuracy ( e.g. the iiSG-325 Jiamond Turning Lathe can cut the surfaces with form accuracy in the range of o.5 o.25 micrometer, and finish 20 -- l0 nm ). Naturally it is very important to test the form and the roughness of the diamond turned surfaces. however almost all of the current methods for testing form and routhress of surfaces are difficult to test form and roughness simultaneously, and uneasy to be used as an on-line testing method. In this paper the author developes a simultaneous method for testing the form and the roughness of the diamond turned surfaces. A laser beam is used to scann over the surface under test, the angular distribution of the scattered light is received by a CCD array. The direction of the specular reflective light gives out the slope of the surface under test, and the scattering spectrum gives out the roughness of the surface. Moreover this method can be used as a fast automated on-line monitoring and diagnosing of the diamond turning machine.