Optical disc information device and information processing device

Patent metadata

Field	Value
Publication number	US-9484054-B2
Application number	US-201514848882-A
Country	US
Kind code	B2
Filing date	Sep 9, 2015
Priority date	Jun 21, 2013
Publication date	Nov 1, 2016
Grant date	Nov 1, 2016

Abstract

An optical disc information device is an optical disc information device for reproducing and/or recording information with respect to an optical disc including a track in the form of a groove, and capable of recording information in a land portion and in a groove portion of the groove. The optical disc information device includes a laser light source, an objective lens, a transmittance limiting element, a dividing element, a light detector, a central amplifier, at least two end amplifiers, a gain controller, an adder, a reproduction signal processor, and a control signal processor. The transmittance limiting element includes a first central region, and at least two first end regions which interpose the first central region therebetween, and attenuates light passing through at least the first end regions out of a light flux emitted from the laser light source more strongly than light passing through the first central region.

First claim

The invention claimed is:

1. An optical disc information device that performs at least one of reproducing information or recording information with respect to an optical disc having a track in the form of a groove, and capable of recording information in a land portion and in a groove portion of the groove, comprising:
a laser light source which emits a light flux of a wavelength λ;
an objective lens having a numerical aperture NA and configured to collect the light flux emitted from the laser light source and to form a light collecting spot on the optical disc;
a transmittance limiting element including a first central region, and at least two first end regions which interpose the first central region therebetween, and configured to attenuate light passing through at least the first end regions out of the light flux emitted from the laser light source more strongly than light passing through the first central region;
a dividing element including a second central region, and at least two second end regions which interpose the second central region therebetween, and configured to divide reflected light that is reflected and diffracted on the optical disc into a light flux of the second central region and light fluxes of the second end regions;
a light detector including a central light receiving portion which receives the light flux of the second central region, and at least two end light receiving portions which receive the light fluxes of the second end regions, and configured to output a light amount signal in accordance with a light amount of each of the received light fluxes;
a central amplifier which receives the light amount signal from the central light receiving portion and outputs a central amplification signal amplified by a predetermined gain;
at least two end amplifiers which receive the light amount signals from the end light receiving portions and output end amplification signals amplified by a predetermined gain;
a gain controller which controls the gain of the central amplifier and the gains of the end amplifiers;
an adder which sums up the central amplification signal from the central amplifier and the end amplification signals from the end amplifiers, and outputs an information signal;
a reproduction signal processor which processes the information signal and outputs a reproduction signal; and
a control signal processor which receives reflected light that is reflected and diffracted on the optical disc, and generates a focusing control signal and a tracking control signal.

2. The optical disc information device according to claim 1 , wherein
the transmittance limiting element is divided into three regions in directions associated with a radial direction of the optical disc, and includes the first central region and the two first end regions, and
the dividing element is divided into three regions in directions associated with the radial direction of the optical disc, and includes the second central region and the two second end regions.

3. The optical disc information device according to claim 1 , wherein
the transmittance of the first end regions of the transmittance limiting element is 50% or more.

4. The optical disc information device according to claim 1 , wherein
the transmittance limiting element is divided into five regions in directions associated with a radial direction of the optical disc,
the first end regions include two third end regions which interpose the first central region therebetween, and two fourth end regions which interpose the third end regions therebetween, and
the dividing element is divided into three regions in directions associated with the radial direction of the optical disc, and includes the second central region and the two second end regions.

5. The optical disc information device according to claim 4 , wherein
the transmittance of the third end regions and of the fourth end regions of the transmittance limiting element is 50% or more.

6. The optical disc information device according to claim 1 , wherein
the transmittance limiting element is disposed on an optical path between the laser light source and the objective lens.

7. The optical disc information device according to claim 6 , wherein
the transmittance limiting element is integrally formed with the objective lens.

8. The optical disc information device according to claim 1 , wherein
a difference between a ratio of a width of the second central region of the dividing element in a direction associated with a radial direction of the optical disc with respect to a width of the light flux, and a ratio of a width of the first central region of the transmittance limiting element in the radial direction of the optical disc with respect to a width of the light flux is within ±15%.

9. The optical disc information device according to claim 1 , wherein
a width of the second central region of the dividing element in a radial direction of the optical disc is within 45%±15% of a width of the light flux.

10. The optical disc information device according to claim 1 , wherein
the central amplifier and the end amplifiers include a digital filter having frequency characteristics such that a gain to be given to the central amplifier and to the end amplifiers by the gain controller is determined by a tap coefficient, and
the gain controller repeats computation from a gain initial value so that an evaluation value that is correlated with an error rate to be obtained by the reproduction signal processor is minimized and outputs an optimized gain.

11. The optical disc information device according to claim 1 , wherein
the gain controller stores in advance a gain initial value for a land portion and a gain initial value for a groove portion which are different from each other,
when a polarity of the tracking control signal is inverted, and a track to be scanned by the light collecting spot is the land portion, the gain initial value for a land portion is set in the central amplifier and in the end amplifiers, and when a polarity of the tracking control signal is inverted, and a track to be scanned by the light collecting spot is the groove portion, the gain initial value for a groove portion is set in the central amplifier and in the end amplifiers.

12. The optical disc information device according to claim 1 , wherein
the gain controller sets a gain initial value for the central amplifier and a gain initial value for the end amplifiers which are different from each other in accordance with a track pitch of the optical disc.

13. The optical disc information device according to claim 1 , further comprising:
a tilt detector which detects a tilt amount of the optical disc in a radial direction, wherein
the gain controller sets a gain initial value in the central amplifier and a gain initial value in the end amplifiers in accordance with the tilt amount detected by the tilt detector.

14. The optical disc information device according to claim 1 , wherein
the control signal processor detects an off track amount of the light collecting spot with respect to a track of the optical disc, and
the gain controller sets a gain initial value in the central amplifier and a gain initial value in the end amplifiers in accordance with the off track amount.

15. The optical disc information device according to claim 1 , further comprising:
a lens shift detector which detects a lens shift amount of the objective lens, wherein
the gain controller sets a gain initial value in the central amplifier and a gain initial value in the end amplifiers in accordance with the lens shift amount detected by the lens shift

Assignees

• Panasonic Ip Man Co Ltd

Inventors

• Wakabayashi Kanji
• Sano Kousei
• Yamasaki Fumitomo
• Komma Yoshiaki
• Tanaka Toshiyasu

Classifications

• G11B7/1395

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

• G11B7/005

  Reproducing (G11B7/0065 takes precedence) · CPC title

• G11B7/24073

  Tracks · CPC title

• G11B7/1381 Primary

  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

• G11B7/1353

  Diffractive elements, e.g. holograms or gratings {(diffraction gratings per se G02B5/18; holograms per se G02B5/32; grating systems G02B27/44)} · CPC title