Edward F. Cross

Annular converging wave cavity.

A new type of resonator that generates an annular geometric mode by use of spherical mirrors has been developed. The four-element cavity consists of an external confocal unstable resonator with a double-sided 45 degrees coupling mirror and a flat feedback mirror. The flat feedback mirror is placed on the plane wave side of the confocal cavity to form an annular mode between the feedback mirror and the coupling mirror. A plane annular wave (matched to an annular gain medium) is fed back into the unstable resonator that alternately converges and diverges to produce a diverging annular output beam. Experiments were performed on a cw HF laser. Observations of mode patterns on the flat feedback mirror and the convex mirror and of far-field beam quality were made. Far-field measurements indicated near-diffraction-limited beam quality for a peak on-axis intensity mode on the convex mirror. A nearly uniform annular mode was observed on the flat feedback mirror.

Window-heating effects on airborne infrared system calibration

Window heating effects are an important consideration in the design and development of airborne missile seeker systems. This paper describes how sharply rising window temperatures can adversely affect detector performance during the seeker homing phase. Initially in the design approach, equations are formulated to calculate target and window radiance on the detector elements for given parameters relevant to target signature, flight aerodynamics, and seeker optics. Using these derived equations, the radiance profiles are plotted as a function of seeker flight time for a typical set of the aforementioned parameters. Then possible design trade-offs and seeker system modifications are discussed that reduce and/or negate window heating effects.

Blackbody radiators for field calibration

The design and construction of four extended-area blackbody radiators for field calibration are described, and the special performance features of each are detailed. Emphasized in design considerations is maintenance of uniform thermal profiles on high-emissivity metal plates that operate at temperatures ranging from 40 to 375 degree(s)C. For each of the four versions, individual radiator plate size and uniform blackbody temperature are the critical design parameters. Laboratory test data are presented to establish that each design configuration meets the operating specifications. The data demonstrate that reliable extended-area blackbody radiators can be built for field use at a lower cost than those of currently available radiators.

HF Laser Flow Visualization with an Infrared Television System

This paper describes an infrared television system used for observing HF continuous chemical laser gas flows. The prime goal for these experiments was the flow visualization of the supersonic free jets provided by the IR HF emissions which were generated by the reaction of hydrogen and fluorine flowing out of selected nozzle configurations. The spatial flow patterns for three IF laser configurations were observed and monitored with this IR television system. The mechanical configuration, optics, and operating parameters associated with each configuration are discussed in this report. The uniformity of the laser medium and the properties of the jet are also described.

Figures of Merit to Characterize Integrating Image Sensors: A Ten-Year Update

A ten-year update is presented on performance criteria and measurement techniques to evaluate integrating image sensors. The integrating image sensor has an irradiance-sensitive focal plane that continuously monitors the field of view and an electronic mechanism that sequentially reads out the integrated signal on each resolution element. Ten years ago, camera tubes were the integrating imagers of interest; today, staring focal plane arrays have supplanted camera tubes as integrating imagers. The adaptability of the 1978 figures of merit to the new staring devices is reviewed and, when indicated, the figures are modified.

Improved Schottky Array Performance With Lenticulated Faceplate

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.

Optical Technique For Increasing Fill Factor Of Mosaic Arrays

A novel optical technique for improving the performance of focal plane staring arrays by increasing the fill factor ratio is described. The specific mosaics considered are 64 x 32 and 128 x 64 Schottky barrier infrared detectors with charge coupled devices (IRCCD) made from monolithic silicon. The video enhancement is accomplished by means of a refracting silicon faceplate that redirects focused image irradiance from nonsensitive CCD areas to the infrared detector elements. Operational theory and design parameters for this unique faceplate construction are detailed. With the optimum faceplate configuration installed at the IRCCD front surface, a sensitivity increase of at least .200 percent is predicted from the analysis presented here.

Improved camera-tube performance with pulsed operation

Improving image-sensing parameters is a high-priority goal in the development of camera-tube (vidicon) television systems. In past efforts to enhance video output from these television systems, the emphasis has been on multiple-frame integrations of a single scene and computer data processing of the recorded video. In the electronic technique discussed in this paper vidicon performance is improved by synchronously controlling the sensing-layer bias. Specifically, camera-tube sensitivity and dynamic response are significantly increased while other tube parameters remain unaffected.

Figures Of Merit To Characterize Integrating Image Sensors

Criteria and laboratory techniques used to measure the performance of integrating image sensors are described. The integrating image sensor has a sensing layer that continually monitors the field of view and an electronic mechanism that sequentially reads out the integrated signal on an elemental basis. Test procedures are given for determining transfer characteristics, spatial response, spectral response, response uniformity, and image retention of these integrating image sensors.

An Infrared Imaging Systems for Launch and Re-entry Measurements

An infrared imaging system is described that has multiple target capability to measure infrared radiation and to obtain spatial data on missiles in the launch, boost, and re-entry phases. Unclassified aspects of measurements of launch vehicles made at the Seehorn Site, White Sands Missile Range, are discussed. Major components of the system include an infrared vidicon sensitive about 1.4 and an f/1.2 optical system with a 6-deg. field of view for focusing infrared radiation onto the vidicon sensing surface. The output video is viewed on a television monitor and simultaneously recorded in real time on video tape at normal TV rates. From the video recording, it is possible to obtain an A-scope presentation of any single video line on a per frame basis, and hence the radiant intensity of multiple targets can be quantitatively determined from a single observation.