Optical correlator for recognizing characters printed on paper

Pattern recognition is an example of data processing for which analog processors are well suited. We can optically classify various and complicated patterns in one operation instantaneously. Unfortunately, most information is written or printed on paper. From this reason they are not suited to conventional coherent processing. In this paper a coherent optical processor which is capable of recognizing characters printed on paper is presented. It is based on quasi Fourier holography adapted to diffuse illumination of optical signals. In this case the recognition correctness is diminished a little. The experiments are carried out with conventional print letters.