Optical pickup device and optical disc apparatus for recording and reproducing information on and from optical disc including plurality of recording layers

An optical pickup device that records or reproduces information by irradiating an optical disc with laser light, comprising:

• a laser diode emitting laser light of about 405 nm in wavelength;
• a grating branching an optical beam emitted from the laser diode into at least a main beam and two sub beams;
• an objective lens irradiating the optical disc with the optical beams branched by the grating and having a numerical aperture of about 0.85;
• a detector including a detection part that receives the optical beam reflected from the optical disc, and
• a detecting lens giving astigmatism to the optical beam which is incident upon the detector,
• wherein
• each of the detection parts of the detector is divided into a plurality of regions,
• a focussing error signal is generated by an astigmatic method on the basis of a detection signal from each of the divided regions,
• a tracking error signal is generated by a Differential-Push-Pull method on the basis of a detection signal from each of the divided regions,
• the detector includes detection parts that respectively receive the main beam and the two sub beams, a light shielding zone extending in a radius direction of the disc to shield incident light across a predetermined width is installed on a central part of each of the two detection parts that detect the two sub beams, and
• an optical magnification from the optical disc to the detector is set within a range larger than 8× and smaller than 15×.

An optical pickup device that records or reproduces information by irradiating an optical disc with laser light, comprising:

• a laser diode emitting laser light of about 405 nm in wavelength;
• a grating branching an optical beam emitted from the laser diode into a main beam and sub beam;
• an objective lens irradiating the optical disc with optical beams branched by the grating and having a numerical aperture of about 0.85;
• a detector that receives the optical beams reflected from the optical disc, and
• a detecting lens giving astigmatism to optical beams that is incident upon the detector,
• wherein
• a focusing error signal is generated by an astigmatic method on the basis of a detection signal from the detector,
• a tracking error signal is generated by a Differential-Push-Pull method on the basis of a detection signal from the detector, and
• an optical magnification from the optical disc to the detector is set within a range larger than 10.5× and smaller than 13.5×.

An optical pickup device that records or reproduces information by irradiating an optical disc with laser light, comprising:

• a laser diode emitting laser light of about 405 nm in wavelength;
• a grating branching an optical beam emitted from the laser diode into a main beam and sub beam;
• an objective lens irradiating the optical disc with the optical beams branched by the grating and having a numerical aperture of about 0.85;
• a detector that receives the optical beams reflected from the optical disc, and
• a detecting lens giving astigmatism to optical beams that is incident upon the detector,
• wherein
• a focusing error signal is generated by an astigmatic method on the basis of a detection signal from the detector,
• a tracking error signal is generated by a Differential-Push-Pull method on the basis of a detection signal from the detector,
• the detector includes detection parts that respectively receive the main beam and the sub beam, a light shielding zone extending in a radius direction of the optical disc to shield incident light across a predetermined width is installed on a central part of the detection part that detect the sub beam, and
• an optical magnification from the optical disc to the detector is set within a range larger than 8× and smaller than 15×.

An optical pickup device that records or reproduces information by irradiating an optical disc with laser light, comprising:

• a laser diode emitting laser light of about 405 nm in wavelength;
• a grating branching an optical beam emitted from the laser diode into a main beam and sub beam;
• an objective lens irradiating the optical disc with the optical beams branched by the grating and having a numerical aperture of about 0.85;
• a detector that receives the optical beams reflected from the optical disc, and
• a detecting lens giving astigmatism to the optical beams that is incident upon the detector,
• wherein
• a focusing error signal is generated by an astigmatic method on the basis of a detection signal from the detector,
• a tracking error signal is generated by a Differential-Push-Pull method on the basis of a detection signal from the detector,
• the detector includes detection parts that respectively receive the main beam and the sub beam,
• the detection part of the sub beam has a zone extending in a radius direction of the optical disc not to detect incident light including central portion of the sub beam across a predetermined width, and
• an optical magnification from the optical disc to the detector is set within a range larger than 8× and smaller than 15×.

An optical pickup device that records or reproduces information by irradiating an optical disc with laser light, comprising:

• a laser diode emitting laser light of about 405 nm in wavelength;
• a grating branching an optical beam emitted from the laser diode into a main beam and sub beam;
• an objective lens irradiating the optical disc with the optical beams branched by the grating and having a numerical aperture of about 0.85;
• a detector that receives the optical beams reflected from the optical disc, and
• a detecting lens giving astigmatism to optical beams that is incident upon the detector,
• wherein
• a focusing error signal is generated by an astigmatic method on the basis of a detection signal from the detector,
• a tracking error signal is generated by a Differential-Push-Pull method on the basis of a detection signal from the detector,
• the detector includes detection parts that respectively receive the main beam and the sub beam,
• the detection part of the sub beam has a zone extending in a radius direction of the optical disc and having a predetermined width, a sub beam detected by the zone being not used to generate the focusing error signal and the tracking error signal, and
• an optical magnification from the optical disc to the detector is set within a range larger than 8× and smaller than 15×.