Data playback device to control a laser illuminating position by comparing phase of a laser drive signal and a laser tracking error detection signal

摘要

A data playback device includes a laser to produce light to illuminate a disk form of data recording medium and to playback data stored on the disk, the data being recorded on the disk in a first group of data tracks and a second group of data tracks, which exist in concentric or spiral form, wherein the first group of tracks and the second group of tracks exist with a mutual difference in level in the radial direction in the disk form of data recording medium. The data playback device further includes a rotary device to rotate the recording medium, a tracking control unit to cause the illumination location of the laser light to follow the first group of tracks or the second group of tracks, and a setting unit to set the control condition in the tracking control unit for tracking with respect to the first group of tracks or for tracking with respect to the second group of tracks. The data playback device maintains the setting in the setting unit in a control condition which has been set with respect to the track last played back.