Image recognition by spectral intensity filtering

A description is given of a coherent-optical filtering method which makes it possible to obtain output signals unaffected by shifts in the input plane. The method is based on intensity filtering of the Fourier spectra and integrated measurements of the intensity of light transmitted by a filter. At each processing stage, a pair of binary filter masks makes it possible to assign the image to one of the two classes of a general set of patterns. The method is illustrated by an example.