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

• Current Assignee: Zetetic Institute
• Original Assignee: Zetetic Institute
• Inventors: Hill, Henry A.
• Primary Examiner(s): Turner, Samuel A.
• Application Number:
  US09/089,105
• Time in Patent Office: 777 Days
• Field of Search: 356/345, 356/349, 356/351, 356/357, 356/360, 356/359
• US Class Current: 356/491
• CPC Class Codes: G01B 2290/45 Multiple detectors for detecting interferometer signals
• CPC Class Codes: G01B 9/02027 Two or more interferometric channels or interferometers
• CPC Class Codes: G01B 9/02042 Confocal imaging
• CPC Class Codes: G01B 9/02056 Passive reduction of errors
• CPC Class Codes: G02B 21/004 fixed arrays, e.g. switchable aperture arrays
• CPC Class Codes: G02B 21/0056 based on optical coherence, e.g. phase-contrast arrangements, interference arrangements
• CPC Class Codes: G02B 21/006 focusing arrangements; selection of the plane to be imaged
• CPC Class Codes: G02B 21/0068 arrangements using polarisation
• CPC Class Codes: G02B 21/008 Details of detection or image processing, including general computer control
• CPC Class Codes: G11B 7/005 Reproducing G11B7/0065 takes precedence
• CPC Class Codes: G11B 7/14 specially adapted to record on, or to reproduce from, more than one track simultaneously

Abstract

An in-focus image of an information-bearing region within an optical memory medium is discriminated from an out-of-focus image so as to reduce errors in reading information represented by the information-bearing region within the optical memory medium by producing a probe beam and a reference beam from a wideband point source, producing antisymmetric spatial properties in the reference beam, converting the probe beam to a beam focused to a line in the information-bearing region, producing an in-focus return probe beam, and producing antisymmetric spatial properties in the in-focus return probe beam. Then the in-focus return probe beam is spatially filtered and passed through a dispersal element to focus it to a line in a detector plane. The reference beam is spatially filtered and passed through a dispersal element to focus it to the line in the detector plane. A beam from an out-of focus image point is spatially filtered and passed through a dispersal element. The spatially filtered reference beam is interfered with the spatially filtered beam from the out-of-focus image point and the spatially filtered in-focus return probe beam. The spatially filtered in-focus return probe beam is detected as an interference term between the spatially filtered reference beam and the spatially filtered in-focus return probe beam by means of the detector. An amplitude of an interference term between an amplitude of the spatially filtered out-of-focus image beam and an amplitude of the spatially filtered reference beam is thereby substantially reduced, and reduces errors in data produced by the detector to represent the information being read.

Claims

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 detecting

i. the reference beam as a nonlinear function of an amplitude of the reference beam, and

ii. the in-focus return probe beam as an interference term between a reference beam and the in-focus return probe beam

by 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.

2. 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 wideband point source;

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

(c) passing the probe beam through a dispersal element to convert the probe beam to a beam focused to a line in the information-bearing region;

(d) producing an in-focus return probe beam;

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

(f) spatially filtering the in-focus return probe beam;

(g) passing the spatially filtered in-focus return probe beam through a dispersal element to convert it to a beam focused to a line in a detector plane of a detector;

(h) spatially filtering the reference beam;

(i) passing the spatially filtered reference beam through a dispersal element to convert it to a beam focused to the line in the detector plane;

(j) spatially filtering a beam from an out-of-focus image point;

(k) passing the spatially filtered beam from the out-of-focus image point through a dispersal element;

(l) interfering the spatially filtered reference beam with the spatially filtered beam from the out-of-focus image point;

(m) interfering the spatially filtered reference beam with the spatially filtered in-focus return probe beam; and

(n) detecting (1) the spatially filtered reference beam as a nonlinear function of an amplitude of the spatially filtered reference beam and (2) the spatially filtered in-focus return probe beam as an interference term between the spatially filtered reference beam and the spatially filtered in-focus return probe beam by means of the detector, an amplitude of an interference term between an amplitude of the spatially filtered out-of-focus image beam and an amplitude of the spatially filtered reference beam being substantially reduced, to reduce errors in data produced by the detector to represent the information being read.

3. The method of claim 2 wherein step (c) includes passing the probe beam through at least one grating, wherein the line is substantially parallel to a major surface of the optical disk.

4. The method of claim 2 wherein the line is substantially perpendicular to a major surface of the optical disk.

5. The method of claim 4 including performing Fourier transforms on the data produced by the detector to convert the data to read information stored at predetermined depths in the information-bearing region within the optical disk.

6. A method for discriminating an in-focus image of an information-bearing region within an optical memory medium from an out-of-focus image so as to reduce errors in reading information represented by the information-bearing region within the optical memory medium, comprising the steps of:

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

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

(c) converting the probe beam to a beam focused to a line in the information-bearing region;

(d) producing an in-focus return probe beam;

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

(f) spatially filtering the in-focus return probe beam;

(g) passing the spatially filtered in-focus return probe beam through a dispersal element to convert it to a beam focused to a line in a detector plane of a detector;

(h) spatially filtering the reference beam;

(i) passing the spatially filtered reference beam through a dispersal element to convert it to a beam focused to the line in the detector plane;

(j) spatially filtering a beam from an out-of focus image point;

(k) passing the spatially filtered beam from the out-of-focus image point through a dispersal element;

(l) interfering the spatially filtered reference beam with the spatially filtered beam from the out-of-focus image point;

(m) interfering the spatially filtered reference beam with the spatially filtered in-focus return probe beam; and

(n) detecting (1) the spatially filtered reference beam as a nonlinear function of an amplitude of the spatially filtered reference beam, and (2) the spatially filtered in-focus return probe beam as an interference term between the spatially filtered reference beam and the spatially filtered in-focus return probe beam by means of the detector, an amplitude of an interference term between an amplitude of the spatially filtered out-of-focus image beam and an amplitude of the spatially filtered reference beam being substantially reduced, to reduce errors in data produced by the detector to represent the information being read.

7. The method of claim 6 wherein step (c) includes passing the probe beam through at least one grating wherein the line is substantially parallel to a major surface of the optical memory medium.

8. The method of claim 6 including performing Fourier transforms on the data produced by the detector to convert the data to read information stored at predetermined depths in the information-bearing region within the optical memory medium.

9. The method of claim 6 wherein the line is substantially perpendicular to a major surface of the optical memory medium.