Abstract

Real-time optical processors have long been recognized for such potential applications as optical computing, robotic vision, radar signal processing, and pattern recognition. In particular, optical processors offer a powerful alternative to electronic processors due to their ability to process in parallel a large amount of spatial information and to perform at extremely high speeds a large number of spatial operations. One example of a real-time optical processor is a simple modification of an early optical correlator proposed by VanderLugt. In a modern version of the VanderLugt processor film is replaced by a photorefractive nonlinear optical medium. The advantage of the crystal approach over traditional wet-chemical processing is that the correlation between different scenes is carried out in real time and not limited by the time needed for development or film replacement. Despite the success of modern correlators, however, they are hampered by an old but severe limitation for practical application. Even the modern correlator has not overcome the inability of traditional correlators to recognize an object independent of its size or the viewed perspective.

© 1987 Optical Society of America