White light joint transform correlator

Abstract

A joint transform correlator (JTC) was proposed to avoid the alignment problem of the spatial filter in the traditional VanderLugt system. By incorporating some spatial light modulators in the optical systems, the JTC was applied to real time pattern recognition. Due to the many advantages, including higher signal-to-noise ratio, associated with the white light optical processing system, we investigate the possibility of utilizing white light illumination in the JTC. The spatial spectra belonging to different wavelengths are dispersed by a phase grating. One of the first-order spectrum is recorded and the coherence requirements are estimated. In the read-out process, the incident light is predispersed by a pair of parallel gratings before shining on the joint transform hologram. Only the object with the line joining its center and that of the reference object parallel to the grating lines can produce correlation spots. This suggests that, when spatial light modulators are placed in position, a 2-D correlation pattern can be generated with correlation spots at their corresponding positions if the input plane and the output detector are rotated synchronously.