Optical implementation and comparison of composite filters displayed on BPOSLMs: optimal trade-off SDF filters Jared-and-Ennis SDF filters and quantized detour-phase encoded OTSDF filters

摘要

Abstract: This paper reviews the progress of an ongoing research program at the Institute of Optical Research which addresses optical correlators dedicated to pattern recognition. A two-class discrimination problem with in-plane distortion is considered. For this purpose, we provide here a comparison between the performances of several synthetic discriminant function (SDF) filters implemented on a binary ferroelectric liquid crystal spatial light modulator (FLC SLM). While non-constrained optimal trade-off (OT) SDF filters perform very well, binary filters offer lower efficiencies. The relative merits of direct binarization of the complex transmittance of the filter and the Jared-and-Ennis method (relaxation algorithm) for filter construction are discussed. To overcome the poor modulation capability of available SLMs and take full advantage of the tuning ability of OT SDF filters, we propose to encode composite filters as detour-phase holograms. We illustrate this discussion with computer simulations as well as experimental results obtained with our optical VanderLugt correlator. In-plane rotation tolerance over 90 degrees and two-class target discrimination are experimentally achieved with a single composite filter. !18