Abstract

Photorefractive crystals are promising materials for real time correlation detection. However, the finite thickness of the crystal severely limits the size of the objects to be correlated and the shift invariance of the correlator due to Bragg diffraction. In this paper a beam compression technique in a joint transformation correlator is employed for reducing the writing angle. The technique greatly alleviates the Bragg diffraction limitation on the thickness of the crystal and increases the diffraction efficiency from the reading beam. On the other hand, the technique requires a proportional increase in the transverse size of the crystal to keep the correlation resolution constant.

© 1989 Optical Society of America