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Optical pattern recognition apparatus with coordinate conversion function

  • US 5,528,702 A
  • Filed: 05/20/1992
  • Issued: 06/18/1996
  • Est. Priority Date: 05/31/1991
  • Status: Expired due to Term
First Claim
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1. An optical pattern recognition apparatus for automatically identifying and measuring specified patterns by performing optical correlation processing, by using coherent light, on two-dimensional images obtained from a photographing means, the optical pattern recognition apparatus comprising:

  • an optical coordinate convertor unit for converting simultaneously and in parallel at least one entered reference image and at least one entered input image from an entered coordinate system to a desired coordinate system to produce a coordinate-converted reference image of each entered reference image and a coordinate-converted input image of each entered input image,the optical coordinate convertor unit comprisingmeans for producing a two-dimensional reference image and input image of said each reference image and said each input image, respectively,at least one coherent light source,at least one object image spatial light modulator for recording the two-dimensional reference image and the two-dimensional input image,at least one coordinate conversion optical filter placed close to the object image spatial light modulator, andat least one lens; and

    a joint transform correlator for generating a correlation coefficient between each coordinate-converted reference image and each coordinate-converted input image, the joint transform correlator comprisingmeans for converting said each coordinate-converted reference image add said each coordinate-converted input image produced by the optical coordinate convertor into respective coordinate-converted intensity distribution images and then displaying the coordinate-converted intensity distribution images on a coordinate-converted image spatial light modulator,means for converting the coordinate-converted intensity distribution images displayed on the coordinate-converted image spatial light modulator into respective coherent images,means for converting the coherent images into a joint Fourier-transformed image of the coordinate-converted intensity distribution images using a Fourier-transform lens,means for converting the joint Fourier-transformed image into a Fourier-transformed intensity distribution image and displaying the Fourier-transformed intensity distribution image on a Fourier-transformed image spatial light modulator,means for reading the Fourier-transformed intensity distribution image displayed on the Fourier-transformed image spatial light modulator using coherent light,means for generating a correlation output image by Fourier-transforming the Fourier-transformed intensity distribution image,means for converting the correlation output image into a correlation signal using either a photographing device or light receiving element, andmeans for processing the correlation signal to determine two-dimensional correlation coefficients of said each two-dimensional reference image and said each two-dimensional input image so that a correlation between said each entered reference image and said each entered input image is obtained to effect pattern recognition in real time.

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