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Optical pattern recognition using multiple reference images

  • US 5,175,775 A
  • Filed: 07/22/1991
  • Issued: 12/29/1992
  • Est. Priority Date: 07/27/1990
  • Status: Expired due to Fees
First Claim
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1. A pattern recognition method for an optical pattern recognition apparatus which is comprised of means for converting a composite input image composed of a group of reference images and at lest one object image into a composite coherent image, means for Fourier-transforming the composite coherent image, means for Fourier-transforming the composite coherent image to produce a joint Fourier-transformed image of the reference images and the object image, means including an optical spatial modulator for recording an optical intensity distribution of the joint Fourier-transformed image on the optical spatial modulator, means for reading the recorded optical intensity distribution with a coherent light to reproduce a corresponding coherent image, means for Fourier-transforming the reproduced coherent image to produce a correlation image, means including a photodetector for detecting the correlation image to produce a corresponding correlation signal, means for processing the correlated signal to determine two-dimensional correlation coefficients between the object image and each respective one of the reference images, and means including a regulating spatial modulator disposed in an optical path extending through the reference images for regulating brightness of each respective one of the reference images according to the corresponding correlation coefficients so as to discriminate a most-associated reference image relative to the object image to thereby effect pattern recognition of the object image, the pattern recognition method comprising the steps of:

  • preparing a plurality of initial groups each containing a given number of individual reference images and carrying out the pattern recognition of the object image with respect to each of the initial groups to discriminate each of the most-associated reference images having a maximum correlation coefficient in each initial group;

    regrouping all of the discriminated most-associated reference images into new groups the number of which is less tan that of the initial groups, and again carrying out the pattern recognition of the object image with respect to the new groups so as to enable a next regrouping; and

    repeatedly carrying out the regrouping so as to reduce the number of the groups to thereby form a final group and carrying out the pattern recognition of the object image using the final group of the reference images to thereby determine a particular reference image corresponding to the object image.

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