Patent ID: 8094535

Claim:
An optical disk device comprising: a light source configured to irradiate a laser pulse onto an optical disk medium on which information data are written; a unit configured to generate a readout signal based on a data pattern written on the optical disk medium, by irradiating a light ray from the light source onto the optical disk medium and detecting resulting reflected light; an A/D converter, configured to convert the readout signal into a readout signal bit stream, and controlled by edges of a clock signal; a binarizing circuit configured to generate binarized information data based on the readout signal bit stream; a digital PLL (Phase Locked Loop) circuit configured to detect binarized information data corresponding to a phase difference between an edge point of the readout signal bit stream and an edge point of the clock signal, and configured to allow a frequency of the clock signal to be adjusted 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 is configured to perform an A/D conversion at a timing that is shifted a half of a clock signal, in order to interpose an edge point of the data pattern of the readout signal bit stream; wherein the FIR filter is configured to perform one of equalization and phase compensation of the readout signal bit stream, in order to generate an equalized readout signal bit stream with a data point corresponding to the edge point of the data pattern of the readout signal bit stream; wherein the edge detection unit is configured to detect the edge point of the equalized readout signal bit stream; wherein an accumulating unit is configured to accumulate at least one of a data value of the edge point and an absolute value thereof, for a predetermined period, in order to obtain at least one of (i) an equalized edge shift value and (ii) an equalized jitter value; and wherein a determination unit is configured to determine a pulse condition of the laser pulse in order to selectively minimize at least one of (i) the equalized edge shift value and (ii) the equalized jitter value, or to make at least one of (i) the equalized edge shift value and (ii) the equalized jitter value smaller than a predetermined value.