Patent ID: 6665250
Filing Date: 2003-12-16
Classification: G11B

Abstract:
A playback apparatus for reading marks written to an optical disc, comprising:an optical head means for emitting a light spot to a mark, reading the mark, and outputting a playback signal; a trimmer means for limiting amplitude in the positive direction and amplitude in the negative direction for the playback signals of an (n+2)T or longer mark length, and not limiting amplitude in the positive direction and amplitude in the negative direction for the playback signals of an nT or (n+1)T mark length in modulation code where the shortest mark is nT (where n is a positive integer and T is the period of the channel clock), so as to make positive and negative amplitudes substantially equal to each other; a waveform equalization circuit for amplifying the high frequency band of the output signal from the trimmer means; and a digitizing circuit for converting the output signal from the waveform equalization circuit to a binary signal using a predetermined threshold value.