Patent Document ID: 20070121463
Application ID: 11492923
Patent Flag: 0

Claim One:
1. An optical disk device comprising: a light source that irradiates a laser pulse to an optical disk medium on which information data are written; a unit of generating a readout signal by irradiating a light lay from the light source to the optical disk medium to read a data pattern written thereon; an A/D converter that converts the readout signal into a readout signal bit stream by each clock; a binarizing circuit that binarizes the information data based on the readout signal bit stream; a digital PLL (Phase Locked Loop) circuit that detects information data corresponding to a phase difference between an edge position of the readout signal bit stream and the clock to allow a frequency of the clock to follow so as to bring the phase difference to be close to zero; an FIR (Finite Impulse Response) filter having an even tap number; and an edge detection unit, wherein: the A/D converter performs an A/D conversion at timing half clock shifted to interpose an edge point of the data pattern; the FIR filter performs one of equalization and phase compensation of the readout signal bit stream to generate an equalized readout signal bit stream with a data point corresponding to the edge point of the data pattern; the edge detection unit detects the edge point of the equalized readout signal bit stream; and when a determination level with respect to mark and space is set to zero, an accumulating unit that accumulates at least one of a data value of the edge point and an absolute value thereof for a predetermined period to obtain at least one of an equalized edge shift value and an equalized jitter value such that a pulse condition of the laser pulse is determined to selectively make at least one of the equalized edge shift value and the equalized jitter value minimum, and make one of those values smaller than a predetermined value.