Real-time joint-transform correlation using optical heterodyning

Driven by potential applications in military, biology, robot navigation and other areas, various methods for optical pattern recognition have been proposed and studied over the past decades. The key feature in current real-time optical pattern recognition systems among these methods is the use of a spatial light modulator (SLM) at the Fourier transform plane in the so-called joint-Fourier transform correlation (JTC) system [C.S Weaver et al. (1966)]. We propose a novel hybrid (optical/electronic) processing technique to achieve real-time joint-transform correlation. The technique employs acousto-optic heterodyne scanning [T.-C. Poon et al., 1979] and it does not require a SLM at the Fourier plane as in other conventional real-time JTC systems. This departure from the conventional scheme is extremely important, as it does not depend on SLM design considerations and issues such as phase uniformity and contrast ratio. The effectiveness of the novel proposed system will be demonstrated with some experimental results. Future work will be focused on exploring scale-invariant, rotation-invariant and multiobject joint-transform correlation with this hybrid optical pattern recognition method.