Patent ID: 7978578
Filing Date: 2011-07-12
Classification: G11B

Abstract:
1. An optical disc device, comprising: an optical head section configured to generate a wobble signal to indicate wobbling of a track formed on a recording surface of an optical disc medium, based on a reflected light reflected by the optical disc medium; a regularity monitoring section, comprising a regularity monitoring circuit, configured to judge an existence or absence of a defect on the optical disc medium, based on a difference between the wobble signal and a signal indicating the wobble under a normal condition; an Automatic Gain Control (AGC) circuit comprising an amplifier, the AGC configured to control a gain of the amplifier such that the amplifier outputs an adjusted wobble signal wherein an amplitude of the wobble signal is made uniform, and also to output a control gain signal indicating the controlled gain, wherein the regularity monitoring circuit is configured to judge the existence or absence of the defect of the optical disc medium based on a variation of the control gain signal, wherein the regularity monitoring circuit comprises an amplitude variation detector configured to detect a varied amplitude which locally varies and is included in the adjusted wobble signal outputted from the AGC circuit, and wherein the regularity monitoring circuit is configured to judge the existence or absence of the defect of the optical disc medium based on the varied amplitude.