Patent ID: 6456578
Filing Date: 2002-09-24
Classification: G11B

Abstract:
An optical disk apparatus, comprising:a pick-up unit which reads out information from an optical disk, the information being recorded on the optical disk in a form of pits, and produces an information signal by photoelectric conversion; a first reproducer which processes the information signal by one of a waveform slice method and a PRML method, and produces a first reproduction signal; a second reproducer which detects a minimum value of a level of the information signal and produces a second reproduction signal; and a switch with selects, as a reproduction information signal, one of the first reproduction signal produced by the first reproducer and the second reproduction signal produced by the second reproducer, in accordance with a recording density of the optical disk to be produced, wherein the information is recorded on the optical disk by pulse width modulation recording, and the second reproducer comprises a differential circuit which differentiates the information signal, a rising zero-cross detector which detects a zero-cross point of a differential waveform, a rising detector which detects a rising of an output pulse from the rising zero-cross detector, and a PWM circuit which subjects an output signal from the rising detector to pulse width modulation.