Abstract
Optical pattern recognition is important in machine vision, target tracking, missile homing and guidance, automation in space station, and unmanned space explorations, One of the most significant techniques used in optical pattern recognition is the acquisition of 2-D correlation signals between any two images. The intensity of the correlation signals indicate the similarity between the two images. Well-known basic correlation techniques include the VanderLugt matched-filters and the pint Fourier-transform correlator. Various modifications of these correlation techniques have been developed for the improvement of their capability in pattern recognition. These include circular harmonic filters, phase-only filters, synthetic discrimination functions, and multiple-channel large-capacity filters, in addition to nonreal-time recording by photographic films, photorefractive crystals (PRCs) have been used for recording realtime matched filters in a four-wave mixing scheme in which a low-level reading (third) beam is used to detect the signal diffracted by the filter.
© 1992 Optical Society of America
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