Device and method for optically correlating a pair of images

Abstract

A two-dimensional optical correlation apparatus includes a transmissive optical mask having a transmissivity pattern corresponding to a two-dimensional reference image and an input image buffer that stores a sequence of pixels corresponding to a raster-scanned input image. The input buffer includes a subimage frame corresponding to a particular segment of the raster-scanned format. As the pixels are serially shifted through the image buffer, every subimage in the input image appears at some time in the subimage frame. The subimage frame is connected to an array of optical emitters. As the input image pixels are serially shifted, the emitter array produces a succession of two-dimensional optical signals corresponding to the succession of input image subimages shafted through the subimage frame. The output of the emitter array is projected onto the transparent mask. Light transmitted through the transparent mask from the emitter array is collected on a single photodiode whose output represents the correlation of the reference image and the input image subimage instantaneously stored in the subimage frame.