Optical information reproduction apparatus and optical information reproduction method

Patent metadata

Field	Value
Publication number	US-9373352-B2
Application number	US-201214649327-A
Country	US
Kind code	B2
Filing date	Dec 10, 2012
Priority date	Dec 10, 2012
Publication date	Jun 21, 2016
Grant date	Jun 21, 2016

Abstract

An optical information reproduction apparatus using holography can appropriately correct an angle and a wavelength of a reference beam in a direction perpendicular to multiplexing while data is reproduced. In the optical information reproduction apparatus which reproduces information from an optical information recording medium by using holography, an angular error signal in the direction perpendicular to multiplexing of the reference beam is generated by using a signal detected by a light detecting unit. A perpendicular angle adjustment element adjusts an angle of the reference beam in the direction perpendicular to multiplexing, based on the angular error signal. A wavelength error signal is generated from a signal detected by the light detecting unit, and a wavelength is adjusted based on the wavelength error signal.

First claim

The invention claimed is:

1. An optical information reproduction apparatus which reproduces information from an optical information recording medium by using holography, the apparatus comprising:
a laser beam source which generates a reference beam;
a multiplexing angle adjustment element which adjusts an angle of the reference beam in a multiplexing direction;
a perpendicular angle adjustment element which adjusts an angle of the reference beam in a direction perpendicular to multiplexing;
an imaging device which detects diffraction light which is to be reproduced from the optical information recording medium;
an optical axis division element which divides the reference beam into at least two reference beams having different angles in the multiplexing direction; and
a light detecting unit which has at least two light receiving surfaces or more detecting diffraction light which is reproduced by irradiating the optical information recording medium with the divided reference beams in a state where an angle of the divided reference beams in the multiplexing direction is shifted from an optimal angle.

2. The optical information reproduction apparatus according to claim 1 , further comprising:
an angular error signal calculation circuit which generates an angular error signal in the direction perpendicular to multiplexing of the reference beam from a signal detected by the light detecting unit,
wherein the perpendicular angle adjustment element adjusts the angle of the reference beam in the direction perpendicular to multiplexing based on a signal output from the angular error signal calculation circuit.

3. The optical information reproduction apparatus according to claim 2 , wherein
the angular error signal calculation circuit generates the angular error signal in the direction perpendicular to multiplexing of the reference beam, based on a luminescent center position of the diffraction light on the light detecting unit.

4. The optical information reproduction apparatus according to claim 2 , wherein
the angular error signal calculation circuit learns an installation error amount in the light detecting unit, corrects a calculation expression for the angular error signal in the direction perpendicular to multiplexing, by using the installation error amount, and then generates the angular error signal.

5. The optical information reproduction apparatus according to claim 2 , wherein
the light detecting unit is configured by Photodetector 1 for detecting a signal which is reproduced in a state where the angle of the reference beam in the multiplexing direction is shifted from the optimal angle in a positive direction, and Detector 2 for detecting a signal which is reproduced in a state where the angle of the reference beam in the multiplexing direction is shifted from the optimal angle in a negative direction.

6. The optical information reproduction apparatus according to claim 5 , wherein
the angular error signal calculation circuit generates the angular error signal in the direction perpendicular to multiplexing of the reference beam, based on information of a difference between a luminescent center position of diffraction light on Photodetector 1 and a luminescent center position of diffraction light on Detector 2.

7. The optical information reproduction apparatus according to claim 1 , further comprising:
a wavelength error signal calculation circuit which generates a wavelength error signal from a signal detected by the light detecting unit,
wherein the beam source adjusts a wavelength based on a signal output from the wavelength error signal calculation circuit.

8. The optical information reproduction apparatus according to claim 7 , wherein
the wavelength error signal calculation circuit generates the wavelength error signal based on a luminescent center position of the diffraction light on the light detecting unit.

9. The optical information reproduction apparatus according to claim 7 , wherein
the wavelength error signal calculation circuit learns an installation error amount in the light detecting unit, corrects a calculation expression for the wavelength error signal by using the installation error amount, and then generates the wavelength error signal.

10. The optical information reproduction apparatus according to claim 7 , wherein
the light detecting unit is configured by Photodetector 1 for detecting a signal which is reproduced in a state where the angle of the reference beam in the multiplexing direction is shifted from the optimal angle in a positive direction, and Detector 2 for detecting a signal which is reproduced in a state where the angle of the reference beam in the multiplexing direction is shifted from the optimal angle in a negative direction.

11. The optical information reproduction apparatus according to claim 10 , wherein
the wavelength error signal calculation circuit generates the wavelength error signal based on information of a difference between a luminescent center position of diffraction light on Photodetector 1 and a luminescent center position of diffraction light on Detector 2.

12. An optical information reproduction method of reproducing information from an optical information recording medium by using holography, the method comprising:
a laser emission process of generating a reference beam;
an optical axis division process of dividing the reference beam into at least two reference beams or more having different angles in a multiplexing direction;
a multiplexing angle adjustment process of adjusting the angle of the divided reference beams in the multiplexing direction;
a perpendicular angle adjustment process of adjusting an angle of the reference beam in a direction perpendicular to multiplexing;
an imaging process of detecting diffraction light which is to be reproduced from the optical information recording medium;
a detection process of causing a light detecting unit which has at least two light receiving surfaces or more, to detect diffraction light which is reproduced by irradiating the optical information recording medium with the reference beam in a state where an angle of the reference beam in the multiplexing direction is shifted from an optimal angle; and
an angular error signal calculation process of generating an angular error signal in a direction perpendicular to multiplexing of the reference beam, from a signal detected by the light detecting unit,
wherein in the perpendicular angle adjustment process, the angle of the reference beam in the direction perpendicular to multiplexing is adjusted based on a signal which is output in the angular error signal calculation process.

13. The optical information reproduction method according to claim 12 , wherein
in the angular error signal calculation process, the angular error signal in the direction perpendicular to multiplexing of the reference beam is generated based on a luminescent center position of diffraction light on the light detecting unit.

14. An optical information reproduction method of reproducing information from an optical information recording medium by using holography, the method comprising:
a laser emission process of generating a reference beam;
an optical axis division process of dividing the reference beam into at least two reference beams or more having different angles in a multiplexing direction;
a multiplexing angle adjustment process of adjusting the angle of the divided reference beams in the multiplexing direction;
an imaging process of detecting diffraction light which is to be reproduced from the optical information recording medium;
a detection process of causing a ligh

Assignees

• Hitachi Consumer Electronics

Inventors

• Hosaka Makoto

Classifications

• G11B7/0065 Primary

  Recording, reproducing or erasing by using optical interference patterns, e.g. holograms · CPC title

• G11B7/1381

  Non-lens elements for altering the properties of the beam, e.g. knife edges, slits, filters or stops (G11B7/1353 - G11B7/1369 take precedence) · CPC title

• G11B7/1362

  Mirrors · CPC title

• G11B7/1395

  Beam splitters or combiners (G11B7/1353, G11B7/1356 take precedence {; beam splitting or combining per se G02B27/10}) · CPC title

• G11B7/08564

  using galvanomirrors · CPC title