<title>Hybrid pattern recognition system</title>

Abstract

A closed loop digital/optical pattern recognition system is presented, using a photorefractive correlator. A personal computer is used to control an optical cross-correlator, consisting of a 4f-Fourier processor with a BaTiO₃ crystal in its Fourier plane. A test pattern is inserted into the optical system, via a modified liquid crystal television. The test pattern is stored in the photorefractive crystal, using a two-wave mixing technique. Several master patterns are compared to the test pattern using the optical cross-correlation technique. The output signal of the optical cross-correlator is detected by a CCD camera, and is transferred to the PC for evaluation. The spatial resolution of the optical system is examined both theoretically and experimentally.