Optical pickup device and optical disc apparatus
Optical pickup device including: semiconductor laser diode emitting optical flux; objective lens converging flux emitted from the diode and radiating flux to an optical disc; diffraction grating branching an optical flux reflected from the disc; and a photodetector receiving flux branched by the grating and has a plurality of light receiving parts, wherein: the grating has areas A, B and C; among diffracted beams diffracted by a track of the optical disc, only a 0-th order diffracted beam becomes incident upon area A, and 0-th and ±1-st order diffracted beams become incident upon area B; the photodetector detects a reproduction signal from optical fluxes diffracted in areas A, B and C; the plurality of light receiving parts which detect the +1-st order diffracted beam or the −1-st diffracted beam diffracted in area A are aligned in a direction substantially perpendicular or parallel to a track direction of the disc.
1. An optical pickup device adapted to interface with a multi-layer optical disc having a plurality of recording layers, comprising:
a semiconductor laser diode which emits an optical flux;
an objective lens which converges the optical flux emitted from said semiconductor laser diode and radiates the optical flux to an optical disc;
an optical branching element which branches an optical flux reflected from said optical disc; and
a photodetector which receives an optical flux branched by said optical branching element and has a plurality of light receiving parts,
wherein:
said optical branching element has three areas A, B and C;
said area C includes a center of said optical branching element;
said area A is spaced in a track direction of the optical disc relative to said area C;
said area B is spaced in a radial direction of the optical disc relative to said area C;
said photodetector detects a reproduction signal from optical fluxes diffracted in said areas A, B and C;
said plurality of light receiving parts which detect the beam diffracted in said area A of said optical branching element are disposed separated from light receiving planes which receive diffracted beams from other areas and aligned in a direction substantially perpendicular to a direction corresponding to the track of said optical disc.
2. The optical pickup device according to claim 1 , wherein four light receiving parts are used for detecting the beam diffracted in said area A of said optical branching element.
3. The optical pickup device according to claim 1 , wherein four light receiving parts are used for detecting the beam diffracted in said area B of said optical branching element.
4. The optical pickup device according to claim 1 , wherein:
a focusing error signal is detected from the beam diffracted in said areas B of said optical branching element;
a tracking error signal is detected from the beam diffracted in said areas A and B of said optical branching element;
an offset correction signal of the tracking error signal is detected from the beam diffracted in said area A of said optical branching element; and
a reproduction signal is detected from a sum of beam diffracted in said areas A, B and C.
5. The optical pickup device according to claim 1 , wherein:
said area A of said optical branching element is line symmetric relative to a center axis passing a center of said area C and line symmetric relative to an axis in a direction perpendicular to said center axis; and
said area B of said optical branching element is line symmetric relative to said center axis and line symmetric relative to an axis in a direction perpendicular to said center axis.
6. The optical pickup device according to claim 1 , wherein one light receiving part is used for detecting the beam diffracted in said area C of said optical branching element.
7. An optical pickup device comprising:
a semiconductor laser diode which emits an optical flux;
an objective lens which converges the optical flux emitted from said semiconductor laser diode and radiates the optical flux to an optical disc;
am optical branching element which branches an optical flux reflected from said optical disc; and
a photodetector which receives an optical flux branched by said optical branching element and has a plurality of light receiving parts,
wherein:
said optical branching element has three areas A, B and C;
said area C includes a center of said optical branching element;
said area A is spaced in a track direction of the optical disc relative to said area C;
said area B is spaced in a radial direction of the optical disc relative to said area C;
said photodetector detects a reproduction signal from optical fluxes diffracted in said areas A, B and C;
said plurality of light receiving parts which detect the beam diffracted in said area A of said optical branching element are aligned in a direction substantially perpendicular to a direction corresponding to the track of said optical disc; and
said plurality of light receiving parts which detect the beam diffracted in said area B of said optical branching element are aligned in a direction substantially parallel to a direction corresponding to the track of said optical disc.
8. The optical pickup device according to claim 1 , wherein four light receiving parts are used for detecting the beam diffracted in said area A of said optical branching element.
9. The optical pickup device according to claim 1 , wherein four light receiving parts are used for detecting the beam diffracted in said area B of said optical branching element.
10. The optical pickup device according to claim 1 , wherein:
a focusing error signal is detected from the beam diffracted in said area B of said optical branching element;
a tracking error signal is detected from the beams diffracted in said areas A and B of said optical branching element;
an offset correction signal of the tracking error signal is detected from the beams diffracted in said area A of said optical branching element; and
a reproduction signal is detected from a sum of beams diffracted in said areas A, B and C.
11. The optical pickup device according to claim 1 , wherein:
said area A of said optical branching element is line symmetric relative to a center axis passing a center of said area C and line symmetric relative to an axis in a direction perpendicular to said center axis; and
said area B of said optical branching element is line symmetric relative to said center axis and line symmetric relative to an axis in a direction perpendicular to said center axis.
12. The optical pickup device according to claim 1 , wherein one light receiving part is used for detecting the beam diffracted in said area C of said optical branching element.
13. An optical disc apparatus comprising:
an optical pickup device including:
a semiconductor laser diode which emits an optical flux;
an objective lens which converges the optical flux emitted from said semiconductor laser diode and radiates the optical flux to an optical disc;
an optical branching element which branches an optical flux reflected from said optical disc; and
a photodetector which receives an optical flux branched by said optical branching element and has a plurality of light receiving parts,
wherein:
said optical branching element has three areas A, B and C;
said area C includes a center of said optical branching element;
said area A is spaced in a track direction of the optical disc relative to said area C;
said area B is spaced in a radial direction of the optical disc relative to said area C;
said photodetector detects a reproduction signal from optical fluxes diffracted in said areas A, B and C;
said plurality of light receiving parts which detect the beam diffracted in said area A of said optical branching element are aligned in a direction substantially perpendicular to or substantially parallel to a direction corresponding to the track of said optical disc;
a laser lighting circuit which drives said semiconductor laser diode in said optical pickup device;
a servo signal generator circuit which generates a focusing error signal and a tracking error signal by using signals detected by said photodetector of said optical pickup device; and
an information signal reproducing circuit which reproduces an information signal recorded in said optical disc.
14. An optical disc apparatus comprising:
an optical pickup device including:
a semiconductor laser diode which emits an optical flux;
an objective lens which converges the optical flux emitted from said semiconductor laser diode and radiates the optical flux to an optical disc;
an optical branching element which branches an optical flux reflected from said optical disc; and
a photodetector which receives an optical flux branched by said optical branching element and has a plurality of light receiving parts,
wherein:
said optical branching element has three areas A, B and C;
said area C includes a center of said optical branching element;
said area A is spaced in a track direction of the optical disc relative to said area C;
said area B is spaced in a radial direction of the optical disc relative to said area C;
said photodetector detects a reproduction signal from optical fluxes diffracted in said areas A, B and C;
said plurality of light receiving parts which detect the diffracted in said area A of said optical branching element are aligned in a direction substantially perpendicular to a direction corresponding to the track of said optical disc; and
said plurality of light receiving parts which detect the beam diffracted in said area B of said optical branching element are disposed in a direction substantially parallel to a direction corresponding to the track of said optical disc;
a laser lighting circuit which drives said semiconductor laser diode in said optical pickup device;
a servo signal generator circuit which generates a focusing error signal and a tracking error signal by using signals detected by said photodetector of said optical pickup device; and
an information signal reproducing circuit which reproduces an information signal recorded in said optical disc.