Abstract

Edge enhancement is one of the most important preprocessing techniques utilized in optical pattern recognition. In an optical correlator, cross-correlations among similar input objects can be greatly reduced by using the edge enhancement technique. Traditionally, optical edge enhancement is obtained by high-pass filtering at the Fourier plane. However, the system SNR is generally lowered by this filtering process. Recently, two differentiating spatial light modulators, specifically designed to generate edge-enhanced output, have been reported. Casasent et al. have demonstrated real-time edge enhancement using a Priz light modulator [1]. The Priz light modulator is a transverse modification of the Pockel’s Read-out Optical Modulator (PROM) with a [111] BSO crystal cut. Armitage and Thackara have designed a BSO photo-addressed nematic liquid crystal differentiating spatial light modulator [2, 3]. A layer of liquid crystal is tuned in a transverse configuration (i.e. the electro-optic response is optimized for E_x and E_y rather than E_z) to achieve the edge-enhancement. The BSO crystal is used as a photo-addressing medium. This SLM is functionally optimized as an edge-enhancing SLM.

© 1988 Optical Society of America