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Multiple layer, multiple track optical disk access by confocal interference microscopy using wavenumber domain reflectometry and background amplitude reduction and compensation

  • US 6,091,496 A
  • Filed: 06/02/1998
  • Issued: 07/18/2000
  • Est. Priority Date: 01/28/1997
  • Status: Expired due to Term
First Claim
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1. A method for discriminating an in-focus image of an information-bearing region within an optical disk from an out-of-focus image so as to reduce errors in reading information represented by the information-bearing region within the optical disk, comprising the steps of:

  • (a) producing a probe beam and a reference beam from a monochromatic point source;

    (b) producing antisymmetric spatial properties in the reference beam;

    (c) producing an in-focus return probe beam by directing the probe beam to an in-focus image point within the information-bearing region;

    (d) producing antisymmetric spatial properties in the in-focus return probe beam;

    (e) interfering the reference beam with a beam from an out-of-focus image point;

    (f) interfering the reference beam with the in-focus return probe beam;

    (g) reducing systematic and statistical errors in data produced by the detector to represent the information being read by detectingi. the reference beam as a nonlinear function of an amplitude of the reference beam, andii. the in-focus return probe beam as an interference term between a reference beam and the in-focus return probe beamby means of a detector, an amplitude of an interference term between an amplitude of the out-of-focus image beam and an amplitude of the reference beam being substantially reduced.

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