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Optical scanning and recording apparatus for fingerprints

  • US 5,233,404 A
  • Filed: 09/26/1990
  • Issued: 08/03/1993
  • Est. Priority Date: 09/28/1989
  • Status: Expired due to Fees
First Claim
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1. An apparatus for use in a fingerprint imaging system comprising:

  • a) a source of illumination,b) a prism comprising a body transparent to light having;

    an imaging surface against which the finger to be imaged is placed,an apex opposite the imaging surface and located proximate the source of illumination such that light from the source of illumination may enter the prism through the apex to strike the finger to be imaged,a viewing surface located between the imaging surface and the apex which lies at an acute angle with respect to the imaging surface,a further surface located between the imaging surface and the apex and generally opposite the viewing surface such that the further surface is imaged on the viewing surface, the further surface being coated with a light absorbing coating to absorb light within the prism and prevent transmission of light into the prism from outside;

    c) imaging means for capturing a fingerprint image arranged on an optical path which exits the viewing surface, the optical path within the prism intersecting the imaging surface at the location of the finger to be imaged at an angle greater than the critical angle; and

    d) a light shield means to prevent light from the source of illumination being transmitted directly to the imaging means;

    whereby, when a finger is placed on the imaging surface, a fingerprint image appears on the viewing surface on the optical path, the fingerprint image consisting of bright fingerprint ridges on a dark background.

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