US 2010/0061202 A1Published application

Optical pickup device and optical disc apparatus

AssigneeHitachi Media Electronics Co., Ltd.

InventorsKazuyoshi Yamazaki, Yasuo Kitada

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Abstract

In the optical pickup device, while reflection light reflected from the optical multi-layer disc is divided into a plurality of regions so as to produce a plurality of divided optical beams, the divided optical beams are focused onto different positions on a photodetector, and a focus error signal is detected by employing a plurality of the divided optical beams by utilizing the knife edge method, and further, a tracking error signal is detected by employing a plurality of the divided optical beams. Furthermore, the dividing regions of the optical beam and light receiving parts are arranged in such a manner that stray light derived from other layers of the optical disc is not entered to a servo signal-purpose light receiving part of the photodetector when the divided optical beam is focused onto a target layer of the optical disc.

Claims12

Dependent claims

An optical pickup device comprising:

a semiconductor laser for emitting laser light;
an objective lens for irradiating luminous flux emitted from said semiconductor laser to an optical disc;
a diffraction grating for branching luminous flux reflected from the optical disc;
and
a photodetector having a plurality of light receiving parts which receive luminous flux branched by said diffraction grating;
wherein:
said diffraction grating has 3 sets of regions “A”, “B”, and “C”;
among disc diffraction light diffracted by a track formed on said optical disc,
zero-order disc diffraction light is entered to said region “A” of the diffraction grating;
and
the zero-order disc diffraction light, +first-order disc diffraction light, and −first-order disc diffraction light are entered to the region “B” thereof;
said photodetector detects a reproduction signal from grating diffraction light diffracted by said regions “A”, “B”, and “C”;
two, or more light receiving parts of said photodetector for detecting either +first-order grating diffraction light or −first-order grating diffraction light of said diffraction grating region “A” are arrayed in a substantially straight line along a direction which is made substantially coincident with a radial direction of said optical disc;
and wherein:
two, or more light receiving parts of said photodetector for detecting either +first-order grating diffraction light or −first-order grating diffraction light of said diffraction grating region “B” are arrayed along a direction which is made substantially coincident with a tangential direction of said optical disc.

12 more elements

An optical pickup device comprising:

a semiconductor laser for emitting laser light;
an objective lens for irradiating luminous flux emitted from said semiconductor laser to an optical disc;
a diffraction grating for branching luminous flux reflected from the optical disc;
and
a photodetector having a plurality of light receiving parts which receive luminous flux branched by said diffraction grating;
wherein:
said diffraction grating has 3 sets of regions “A”, “B”, and “C”;
among disc diffraction light diffracted by a track formed on said optical disc,
zero-order disc diffraction light is entered to said region “A” of the diffraction grating;
and
the zero-order disc diffraction light, +first-order disc diffraction light and −first-order disc diffraction light are entered to the region “B” thereof;
said photodetector detects a reproduction signal from luminous flux diffracted by said regions “A”, “B”, and “C”;
two, or more light receiving parts of said photodetector for detecting either +first-order grating diffraction light or −first-order grating diffraction light of said diffraction grating region “A” are arrayed along such a direction substantially perpendicular to a direction which is made substantially coincident with a radial direction of said optical disc;
two, or more light receiving parts of said photodetector for detecting either +first-order grating diffraction light or −first-order grating diffraction light of said diffraction grating region “B” are arrayed in a substantially straight line which is made substantially coincident with a tangential direction of said optical disc;
a quadrangle connected by both ends of a line segment “A” and both ends of a line segment “B” corresponds to a parallelogram, while said line segment “A” connects the respective light receiving parts for detecting the +first-order diffraction light of said diffraction grating region “A”, and said line segment “B” connects the respective light receiving parts for detecting the −first-order diffraction light of said diffraction grating region “A”;
and wherein:
a line segment “C” which connects two, or more light receiving parts for detecting both the +first-order diffraction light and the −first-order diffraction light of said diffraction grating region “B” is equal to a distance between the line segment “A” and the line segment “B.”

14 more elements

An optical pickup device comprising:

a semiconductor laser for emitting laser light;
an objective lens for irradiating luminous flux emitted from said semiconductor laser to an optical disc;
a diffraction grating for branching luminous flux reflected from the optical disc;
and
a photodetector having a plurality of light receiving parts which receive luminous flux branched by said diffraction grating;
wherein:
said diffraction grating has 3 sets of regions “A”, “B”, and “C”;
among disc diffraction light diffracted by a track formed on said optical disc,
zero-order disc diffraction light is entered to said region “A” of the diffraction grating;
and
the zero-order disc diffraction light, +first-order disc diffraction light and −first-order disc diffraction light are entered to the region “B” thereof;
said photodetector detects a reproduction signal from luminous flux diffracted by said regions “A”, “B”, and “C”;
two, or more light receiving parts of said photodetector for detecting either +first-order grating diffraction light or −first-order grating diffraction light, or both the +first-order grating diffraction light and the −first-order grating diffraction light of said diffraction grating region “A” are arrayed along a direction which is made substantially coincident with the radial direction of said optical disc;
two, or more light receiving parts of said photodetector for detecting either +first-order grating diffraction light or −first-order grating diffraction light of said diffraction grating region “B” are arrayed along a direction which is made substantially coincident with a tangential direction of said optical disc;
and wherein:
said photodetector further has a light receiving part into which the zero-order diffraction light of said diffraction grating regions “A”, “B”, and “C” is entered.

13 more elements

Dependencies are inferred from the claim text.

Facts

Application: 12/417,053Filed 2 Apr 2009
Priority: JP 2008-2277415 Sep 2008
Published: 11 Mar 2010
Term ends: Not estimatedThe source records don’t support an estimate.

Classification6 codes

G11B 7/0903
For track following only: multi-beam tracking systems
G11B 7/131
Optical detectors therefor: arrangement of detectors in a multiple array
G11B 7/1353
Means for guiding the beam from the source to the record carrier or from the record carrier to the detector: diffractive elements, e.g. holograms…
G11B 7/08582
Arrangements for mechanically moving the whole head: sled-type positioners