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“Nonlinear Real-Time Optical Signal Processing, Annual Technical Report”
by A.A. Sawchuk, T.C. Strand, A.R. Tanguay, Jr., A. Armand, J. Michaelson, P. Chavel, R. Forchheimer, M. Muha
April 14, 1980
The results of the third year of a three year research program in nonlinear real-time optical signal processing are described. The goal of the program is to extend fast parallel nonlinear operations to optical processing systems with large time-bandwidth and space-bandwidth products. Work on real-time halftone nonlinear processing which was originally begun on this project has been completed. A detailed analysis of degradation due to the finite gamma and other non-ideal effects of the recording medium has been completed along with an extensive study of techniques for precompensating these effects. Further improvements in experimental work await a liquid crystal light valve (LCLV) with a sharper threshold and better uniformity and repeatability. The direct nonlinear technique of parallel A/D conversion previously investigated is also limited by the same problems and will be continued to be studied if better LCLV's are available. A detailed theoretical analysis of liquid crystal devices and associated photoconductors has been completed and provides an excellent fit to experimental data obtained on several devices provided by Hughes Research Laboratories. These results have been used to make a flexible multiple light valve system (MLVS) in which the form of the nonlinearity can be varied. Continued experimentation on variable-grating mode (VGM) devices has revealed many interesting effects with useful applications in both analog and numerical optical signal processing. Preliminary theoretical modeling work to explain these effects has begun. Experimental implementation of binary combinatorial logic functions is presented. The project has been a joint effort between the University of Southern California Image Processing Institute (USCIPI) and the Hughes Research Laboratories (HRL), Malibu, California. The USC group has developed new systems and techniques for nonlinear optical processing and the HRL group has performed work on various real-time devices.