Patent ID: 8315142
Filing Date: 2012-11-20
Classification: G11B

Abstract:
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.