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Device for forming and detecting fingerprint images with valley and ridge structure

  • US 5,974,162 A
  • Filed: 02/27/1995
  • Issued: 10/26/1999
  • Est. Priority Date: 02/18/1994
  • Status: Expired due to Fees
First Claim
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1. A device for producing an image of a fingerprint having ridges and valleys, said device comprising:

  • light producing means for producing light rays;

    a light transmitting substrate capable of transmitting the light produced by said light producing means;

    a fingerprint illuminating region for physical placement of a finger bearing a fingerprint;

    an image detection means for detecting an image of said fingerprint;

    an optical element affixed to a portion of said light transmitting substrate and being disposed between said fingerprint illuminating region and said image detection means, said optical element embodying a light diffracting grating;

    wherein said fingerprint illuminating region, said optical element and said image detection means are each disposed substantially along a common optical axis; and

    wherein during the operation of said device,(1) light rays produced by said light producing means, propagate within said light transmitting substrate towards said optical element and are diffracted by said light diffracting grating,(2) diffracted light rays produced by said light diffracting grating, propagate directly towards said fingerprint illuminating region and fall incident upon and are intensity modulated by the ridges and valleys of said fingerprint, and(3) intensity modulated light rays produced from said ridges and valleys propagate directly back through light transmitting substrate and said optical element and fall incident upon said image detection means, whereupon an image of said fingerprint is detected, said detected image including information corresponding to said ridges and valleys of said fingerprint.

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