INVARIANT JOINT TRANSFORM CORRELATOR USING COORDINATE TRANSFORMATION

A joint transform correlator incorporating the coordinate transformati on technique is proposed to perform invariant pattern recognition. Ins tead of an input image or its Fourier transform intensity being mapped , the Fourier transform of the input image is directly transformed fro m rectangular into logarithmic-polar coordinates. All information is s aved, and as a result, multiple objects can be processed simultaneousl y. A binary optical component is designed and fabricated to perform co ordinate transformation with high efficiency. Further, a Dammann grati ng is applied to generate a two-periodicity mapped reference image to overcome correlation peak dropping due to the cyclic shift of the mapp ed image along the theta axis when the target is rotated. (C) 1996 Soc iety of Photo-Optical instrumentation Engineers.