Abstract

Motion detection, velocity filtering and the detection of change in a given scene are all important aspects for optical processing architectures and systems. So far several different techniques have been reported in the literature that use either all optical [1-4], or hybrid (optical plus electronic) [5-6], schemes to implement novelty filter [1] type operations. The electronic techniques however may have only limited applications due to the sequential nature of the process. For essentially all-optical schemes the intrinsic advantages of parallel image subtraction are clear. In this paper we report a different scheme for motion detection and velocity filtering which uses two spatially multiplexed gratings with a relative phase shift of 180 degrees, (known as complementary gratings). Such grating recording has already been implemented in a LiNbO₃ crystal [7].

© 1991 Optical Society of America