Optical disk apparatus and its reproducing method
View Patent ↗Amplitude and frequency of a high-frequency signal superposed on a reproduction laser beam are changed in accordance with a reproduction spot diameter on the surface of the recording layer upon discrimination of an optical disk in initial adjustment after insertion of the optical disk and change of a layer of a multi-layer optical disk. Further, the high-frequency signal is not superposed on the reproduction laser beam until end of the discrimination and change to a target layer upon discrimination of the optical disk and change of a layer of a multi-layer optical disk.
1. An optical disc apparatus which reproduces information recorded on a first recording layer disposed at a first distance from a surface of an optical disc having a plurality of recording layers and information recorded on a second recording layer disposed at a second distance from the surface of the optical disc, comprising:
a laser which emits a laser beam having a predetermined wavelength;
an objective lens which focuses the laser beam having the predetermined wavelength emitted from the laser on the first recording layer and the second recording layer of the optical disc;
a laser driver which supplies a laser driving current on which a high-frequency current having a first amplitude is superposed to the laser when reproducing information recorded on the first recording layer and supplies a laser driving current on which a high-frequency current having a second amplitude which is different from the first amplitude is superposed to the laser when reproducing information recorded on the second recording layer; and
a laser power control circuit which controls a laser power of the laser such that the laser having a first laser power is emitted to the first recording layer when supplying a laser driving current on which a high-frequency current having the first amplitude is superposed to the laser and controls a laser power of the laser such that the laser having a second laser power which is different from the first laser power is emitted to the second recording layer when supplying a laser driving current on which a high-frequency current having the second amplitude is superposed to the laser;
wherein a ratio of the first amplitude to the first laser power is nearly equal to a ratio of the second amplitude to the second laser power.
2. An optical disk apparatus according to claim 1 , wherein
the first amplitude is lower than the second amplitude;
the first laser power is lower than the second laser power; and
the laser driver supplies the laser driving current on which a high-frequency current having the second amplitude is superposed to the laser and the laser power control circuit controls the laser power of the laser such that the laser having the second laser power is emitted to the second recording layer after reproducing information recorded on the first recording layer.
3. An optical disc reproduction method of reproducing information recorded on a first recording layer disposed at a first distance from a surface of an optical disc having a plurality of recording layers and information recorded on a second recording layer disposed at a second distance from the surface of the optical disc, comprising:
emitting a laser beam having a predetermined wavelength;
focusing the laser beam having the predetermined wavelength emitted from a laser on the first recording layer and the second recording layer of the optical disc;
supplying a laser driving current on which a high-frequency current having a first amplitude is superposed to the laser and controlling a laser power of the laser such that the laser having a first laser power is emitted to the first recording layer when reproducing information recorded on the first recording layer; and
supplying a laser driving current on which a high-frequency current having a second amplitude is superposed to the laser and controlling a laser power of the laser such that the laser having a second laser power is emitted to the second recording layer when reproducing information recorded on the second recording layer;
wherein a ratio of the first amplitude to the first laser power is nearly equal to a ratio of the second amplitude to the second laser power.
4. An optical disc reproduction method according to claim 3 , wherein
the first amplitude is lower than the second amplitude;
the first laser power is lower than the second laser power; and
supplying the laser driving current on which a high-frequency current having the second amplitude is superposed to the laser and controlling the laser power of the laser such that the laser having the second laser power is emitted to the second recording layer after reproducing information recorded on the first recording layer.
5. An optical disc apparatus which reproduces information recorded on a first recording layer disposed at a first distance from a surface of an optical disc having a plurality of recording layers and information recorded on a second recording layer disposed at a second distance from the surface of the optical disc, comprising:
a laser which emits a laser beam having a predetermined wavelength;
an objective lens which focuses the laser beam having the predetermined wavelength emitted from the laser on the first recording layer and the second recording layer of the optical disc;
a high-frequency current generation circuit which generates a high-frequency current having a first amplitude and a second amplitude;
a laser power control circuit which controls a laser power of the laser;
wherein the laser having a first laser power is emitted to the first recording layer when reproducing information recorded on the first recording layer and the laser having a second power is emitted to the second recording layer when reproducing information recorded on the second recording layer;
wherein a high-frequency current having the first amplitude is superposed to the laser having the first laser power, and a high-frequency current having the second amplitude is superposed to the laser having the second laser power; and
wherein a ratio of the first amplitude to the first laser power is nearly equal to a ratio of the second amplitude to the second laser power.
6. An optical disk apparatus according to claim 5 , wherein
the first amplitude is lower than the second amplitude;
the first laser power is lower than the second laser power; and
the laser having a second power is emitted to the second recording layer after reproducing information recorded on the first recording layer.
7. An optical disc reproduction method of reproducing information recorded on a first recording layer disposed at a first distance from a surface of an optical disc having a plurality of recording layers and information recorded on a second recording layer disposed at a second distance from the surface of the optical disc, comprising:
emitting a laser beam having a predetermined wavelength;
focusing the laser beam having the predetermined wavelength emitted from a laser on the first recording layer and the second recording layer of the optical disc;
generating a high-frequency current having a first amplitude and a second amplitude; controlling a laser power of the laser;
wherein the laser having a first laser power is emitted to the first recording layer when reproducing information recorded on the first recording layer and the laser having a second laser power is emitted to the second recording layer when reproducing information recorded on the second recording layer;
wherein a high-frequency current having the first amplitude is superposed to the laser having the first laser power, and a high-frequency current having the second amplitude is superposed to the laser having the second laser power; and
wherein a ratio of the first amplitude to the first laser power is nearly equal to a ratio of the second amplitude to the second laser power.
8. An optical disk apparatus according to claim 7 , wherein
the first amplitude is lower than the second amplitude;
the first laser power is lower than the second laser power; and
the laser having a second power is emitted to the second recording layer after reproducing information recorded on the first recording layer.