Interference filters as nonlinear decision-making elements for three-spot pattern recognition and associative memories

Abstract

Simple patterns consisting of three spots (V and Gamma) have been recognized by dividing, shifting, and recombining beams onto bistable ZnS interference filters. This experiment demonstrates AND-gate operation, cascading, and a moderate amount of parallelism, but a laser power of several watts was required and the response times were several milliseconds. An associative memory for fingerprint identification has been constructed using a VanderLugt correlator and an interference filter as a reflective thresholding device.