A Time-Sequenced Rotation And Scale-Invariant Optical Correlator For Multiple Target Recognition

Abstract

A rotation and scale-invariant optical correlator has been developed, assembled, and evaluated for use as a multiple target recognition system. The system consists of an optical correlator with magneto-optic spatial light modulators (MOSLMs) at the input and filter planes and a vidicon at the correlation plane. A COMPAQ 386 (IBM compatible) personal computer with a frame grabber board is used to acquire, binarize and load binary amplitude-only video images to the input MOSLM, to write sequential stored binary phase-only filters to the filter MOSLM, and to sample and statistically analyze correlation plane data in order to locate and recognize objects of interest in the input scene. The sequential correlations and output data samples are obtained at near video rates (15 per second), allowing multiple targets at any scale and in-plane rotation in a given input image to be located and classified in seconds. Experimental results indicate that this system can correctly identify objects within its target class more than 90% of the time, even in the presence of severe clutter and noise.