Abstract

A real-time image recognition system that can perform complex signal detection under partially coherent illumination is presented. The unique features of the correlator are that the target under study may be a diffusely illuminated real object, and the real-time correlation signal is produced using a narrowband extended light source. The system employs an optical correlator used with a spatial light modulator (liquid crystal image transducer). Pattern recognition experiments using naturally illuminated real objects are provided and the effects of partially coherent illumination on the spatial phase variations in the output wavefront of the device are investigated. Such nonuniformities may arise from nonflatness and mismatch of various output layers in some liquid crystal image transducers which can degrade the performance of the correlator. The experimental results indicate that the distortion effects present in the output surface of the device can be reduced by relaxing the coherence requirements of the system. A quantitative analysis is presented to study the effects of partially coherent illumination on the real-time correlation signal.

© 1986 Optical Society of America