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US 8,427,923 B2Granted
Optical pickup device, optical disc device and focus adjusting method
AssigneeSanyo Electric Co., Ltd.
InventorsSatoshi Kanai, Kenji Nagatomi
Life of this patent
Estimating the term…
Abstract
An optical pickup device includes an astigmatism element which imparts astigmatism to laser light reflected on a disc, a spectral element which changes propagating directions of four light fluxes obtained by dividing a light flux of the laser light reflected on the disc to disperse the four light fluxes from each other, and a photodetector having a sensor group which receives the four light fluxes. The optical pickup device is further provided with a memory which holds a correction value for suppressing a DC component in a tracking error signal resulting from a positional displacement of the spectral element. The tracking error signal is corrected by the correction value to thereby suppress the DC component.
Claims6
An optical pickup device comprising:
- a laser light source;
- an objective lens which converges laser light emitted from the laser light source on a disc;
- an astigmatism element which imparts astigmatism to the laser light reflected on the disc to set a first focal line position to be defined by convergence of the laser light in a first direction, and a second focal line position to be defined by convergence of the laser light in a second direction perpendicular to the first direction away from each other in a propagating direction of the laser light;
- a spectral element which changes propagating directions of four light fluxes obtained by dividing a light flux of the laser light reflected on the disc by a first straight line and a second straight line respectively in parallel to the first direction and the second direction to disperse the four light fluxes from each other;
- a photodetector including a sensor group which receives the four light fluxes dispersed by the spectral element;
- and
- a memory which holds a correction value for suppressing a DC component in a tracking error signal resulting from a positional displacement of the spectral element with respect to an optical axis of the laser light.
4 more elements
An optical disc device comprising:
- an optical pickup device;
- a computing circuit which computes a signal to be outputted from the optical pickup device;
- and
- a memory which holds a control parameter, the optical pickup device including:
- a laser light source;
- an objective lens which converges laser light emitted from the laser light source on a disc;
- an astigmatism element which imparts astigmatism to the laser light reflected on the disc to set a first focal line position to be defined by convergence of the laser light in a first direction, and a second focal line position to be defined by convergence of the laser light in a second direction perpendicular to the first direction away from each other in a propagating direction of the laser light;
- a spectral element which changes propagating directions of four light fluxes obtained by dividing a light flux of the laser light reflected on the disc by a first straight line and a second straight line respectively in parallel to the first direction and the second direction to disperse the four light fluxes from each other;
- and
- a photodetector which receives the four light fluxes dispersed by the spectral element, wherein
- the memory holds a correction value for suppressing a DC component in a tracking error signal resulting from a positional displacement of the spectral element with respect to an optical axis of the laser light, and
- the computing circuit includes a computing section which generates the tracking error signal based on an output from the photodetector, and a correcting section which corrects an output from the computing section based on the correction value.
9 more elements
A focus adjusting method for controlling a focal point of irradiated light to follow a track on a target surface, the focus adjusting method comprising:
- imparting astigmatism to the irradiated light reflected on the target surface to set a first focal line position to be defined by convergence of the irradiated light in a first direction, and a second focal line position to be defined by convergence of the irradiated light in a second direction perpendicular to the first direction away from each other in a propagating direction of the irradiated light;
- changing propagating directions of four light fluxes obtained by dividing a light flux of the irradiated light reflected on the target surface by a first straight line and a second straight line respectively in parallel to the first direction and the second direction to disperse the four light fluxes from each other;
- generating a focus error signal by an astigmatism method based on a light amount balance between the four light fluxes to adjust a position of the focal point in an optical axis direction of the irradiated light based on the generated focus error signal;
- generating a push-pull signal based on a light amount balance, of the irradiated light reflected on the target surface, in a direction perpendicular to a diffraction image of the track to adjust a position of the focal point in a direction of the irradiated light crossing the track, based on the generated push-pull signal;
- and
- obtaining a correction value for suppressing a DC component in the push-pull signal, based on a light amount balance in a direction perpendicular to the diffraction image, the light amount balance being obtained by converging the irradiated light on a flat reflection surface devoid of formation of the track, before the position of the focal point is adjusted in the direction crossing the track to correct the push-pull signal based on the obtained correction value, and to adjust the position of the focal point in the direction crossing the track, based on the corrected push-pull signal.
3 more elements
Dependencies are inferred from the claim text.