Abstract

Current methods for real-time joint transform correlation (JTC) use a spatial light modulator (SLM) in the focal plane to store the interference intensity which is subsequently readout by coherent light. Because the resolution required for accurate representation of the image transform is extremely high, the spatial light modulators that have met the specifications are expensive. Recently, a novel approach to real-time JTC using an optical heterodyning technique had been proposed.¹ The proposed technique obviates the use of a SLM in the focal plane. The patterns to be correlated are coherently illuminated at two different optical frequencies in the front focal plane of a lens. By scanning the interference intensity in the back focal plane of the lens with a chirp grating and subsequent optical heterodyning with a photodetector, spatial correlation between the two patterns carried by the heterodyne frequency can be extracted at the output of the photodetector.

© 1991 Optical Society of America