We present an experimental realization of optical correlation for real-time rotational-invariance pattern recognition by means of a photorefractive joint transform correlator. Single and multiple circular harmonic components have been used to form correlation filters. The correlator operates with a liquid crystal television as the input images and a photorefractive crystal Bi12SiO20 (BSO) as the recording medium. Suitable pre-processing of the references at the object plane makes up for the lack of light transmission. The properties of circular harmonic phase-only filter and circular harmonic matched filter have been compared. Also the noise robustness of these filters has been tested by tracking an object against a non-overlapping noise background. Analysis and experimental results are presented.
Zhang, H., Cartwright, C. M., Ding, M-S., Wang, Z-Q., Cook, N. J., & Gillespie, W. A. (2000). Experimental implementation of a photorefractive joint transform correlator with circular harmonic filters. Optics Communications, 173(1-6), 129-136. https://doi.org/10.1016/S0030-4018(99)00598-2