Identification of complex scattered signals with a fast real-time hybrid electro-optical correlator

The goal of this work was to develop a fast optical correlator for automatic real-time target recognition. The tremendous importance of optical correlators for military and civilian applications was recognized recently and approved by a US conference committee of senators nd representatives. This publication presents the experimental results of detecting and identifying complex scattered signals by using an innovative, hybrid electro-optical correlator. Our technique is based on achieving optical correlation by utilizing state-of-the-art devices: time delay integration, charge coupled devices, liquid crystal displays, and electronically controllable light sources. Results of the experiment with our optical correlator, performed with simulated sonar signals with a center frequency of 100 kHz and duration of 8 to 512 pulses, show the possibility of recognizing a Doppler shift of 20 Hz. This Doppler shift corresponds to a target velocity of 20.7 m/sec. Simulation results indicate that we can achieve significant correlation for a noisy signal by using appropriate signal length. Our experiments demonstrate that we can perform approximately 1010 multiply accumulate operations per second with the high parallel optical corrector, compared to approximately 106 multiply accumulate operations per second using a Pentium 133 MHz personal computer. This new optical correlation scheme can provide solutions for overcoming the inherent shortcomings attributable to the low dynamic range of CCD, and the problem of compatibility caused by different pixel patterns between LCD and CCD by making use of high-quality optics and modern means of achieving uniform illumination.