Hybrid optoelectronic joint transform correlator for the recognition of targets in cluttered scenes

Abstract

Hybrid optoelectronic joint transform correlator (HOJTC), exploiting the Fourier transform property of a lens, implements target detection in real time. Adaptive nonlinear digital filtering in the joint transform power spectrum (JTPS) plane improves the immunity against the noise and clutter. In this paper, electrically addressed liquid crystal devices (EALCD) are used as the space light modulators (SLM), Charge Coupled Device (CCD) matrix camera as the square law detector and Ar⁺ laser as the light source. We develop the hybrid optoelectronic joint transform correlator controlled by computers, which can successfully detect and recognize the target in cluttered scenes in real time. The speed rate of the recognition is 25 frames per second. As the experiment examples, the target recognition of a tank and a car in cluttered scenes is presented. The experiments show that the intensity of cross-correlation peaks after adaptive nonlinear digital filtering is increased greatly, the performance of the joint transform correlator is improved, and it can detect the distorted and noisy targets in cluttered scenes in real time. It was found that using wavelet filter in frequency domain is a very effective way to suppress clutter noise while maintaining high tolerance for distortion.