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OPTICAL PROCESSOR FINGERPRINT IDENTIFICATION APPARATUS

  • US 3,771,129 A
  • Filed: 07/27/1972
  • Issued: 11/06/1973
  • Est. Priority Date: 07/27/1972
  • Status: Expired due to Term
First Claim
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1. Pattern inspection apparatus comprising a rotatable grating having alternate light transmissive and reflective lines, means including a light source for directing a light beam onto the grating, means disposed in the path of light propagated from a part of said grating irradiated by the light beam of the light source for directing light received from the grating back onto the grating to produce in superposed relation with said grating part an equivalent size image thereof wherein the image light impinges on alternate lines of the grating, said grating image producing means including means for supporting an input pattern to be inspected in the light received from the grating, said input pattern being characterized by light transmissive or reflective lines of random orientation over the area of the pattern having the effect when present at said supporting means of diffracting light which is spatially separated from the grating image light at the location of the grating, means for rotating the grating to move the grating lines illuminated by the grating image in a common plane transversely of the light beam directed thereon from the light source whereby the superposed grating image light continuously impinges on alternate lines of the grating, means disposed to receive, under the condition of an input pattern present at said supporting means, light diffracted by the pattern and filtered by the grating to the exclusion of substantially all of the grating image light for producing an image of the pattern, a detector array disposed for receiving the light of the pattern image, said detector array including a plurality of detectors each arranged to receive light forming an image of a discrete sample area of the input pattern, the image light of each said descrete sample area being diffracted in a prescribed direction in accordance with the line orientation in the respective sample areas whereby the diffracted light reaching each detector passes through an extremum value during each half revolution of the grating, and means for determining the angular orientation of the grating relative to a reference orientation at the instant of an extremum value of the light intensity at the respective light detectors.

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