Patent ID: 6252834
Filing Date: 2001-06-26
Classification: G11B

Abstract:
An optical disc device comprising:a laser light source for radiating a laser light beam illuminated via an objective lens on a signal surface of an optical disc;laser light intensity detection means for detecting the light intensity of the laser light radiated from said laser light source;automatic power controlling means for controlling a laser output of said laser light source so that a detection output by said laser light intensity detection means will be constant for two laser light intensities corresponding to two types of optical discs having different numbers of signal surfaces and unique reflectivities;return light detection means for detecting the return light of the laser light beam radiated by said laser light source and reflected by the signal surface of said optical disc;focusing control means for displacing said objective lens along the optical axis responsive to the focusing error signals generated on the basis of a detection output of said return light detection means for controlling the focusing state of a beam spot of said laser light on the signal surface of said optical disc; andcontrolling means for controlling a closed-loop gain of said automatic power controlling means to a gain in meeting with the reflectivity of the optical disc based on a detection output of said return light detection means which prevails when focusing is applied to the signal surface of the optical disc by said focusing control means,wherein said laser light intensity varies depending on the closed loop gain.