Patent ID: 7362674

Claim:
A defect detection apparatus comprising: an amplifier circuit for amplifying a reflection signal which is obtained according to the intensity of reflected light of a light beam that is applied onto an optical disc, on the basis of a control signal indicating whether an optical disc drive performs playback or recording, with a gain according to the operation of the optical disc drive; an envelope detection circuit for obtaining an envelope of an output signal of the amplifier circuit; a first pulse generation circuit for outputting a pulse of a predetermined length every time the control signal is changed; an integration circuit for integrating the output signal of the envelope detection circuit with a predetermined time constant, with its output value being changed during a period when it receives the pulse outputted from the first pulse generation circuit; a slice level setting circuit for setting, on the basis of an output signal from the integration circuit, a slice level used when detecting a defect detection signal indicating presence/absence of a defect on the optical disc; and a comparator for comparing the output signal of the envelope detection circuit with the slice level, to output the defect detection signal.