Patent attributes
During a predetermined period of time after the operation of an optical disc drive has changed from recording to playback or from playback to recording, a first monomulti circuit outputs a pulse signal according to the operation change of the optical disc drive. On receipt of the pulse signal, a capacitor included in an integration circuit is short-circuited at a predetermined reference voltage to fix the output value of the integration circuit at the reference voltage. After the period has passed, on receipt of a pulse signal outputted from a second monomulti circuit, a resistor included in the integration circuit is short-circuited, and an envelope signal is integrated with a time constant being reduced, whereby detection of a false defect signal is avoided, and defect detection can be speedily restarted.
