Nonlinear rotation-invariant pattern recognition by use of the optical morphological correlation

We introduce a modification of the nonlinear morphological correlation for optical rotation-invariant pattern recognition. The high selectivity of the morphological correlation is conserved compared with standard linear corre lation The operation pel forms the common morphological correlation by extr action of the information by means of a circular-harmonic component of a re ference. In spite of some loss of information good discrimination is obtain ed, especially for detecting images with a high degree of resemblance. Comp uter simulations are presented, as well as optical experiments implemented with a joint transform correlator. (C) 2000 Optical Society of America.