Optical head and optical disc apparatus

摘要

To improve the quality of a tracking error signal when reproducing information recorded in an optical disc having tracks with two or more different pitches, using a diffraction element which is given a diffraction pattern configured to provide diffracted rays on the light-receiving surface of a photodetector which receives a reflected laser beam reflected on the recording layer of an optical disc and outputs a corresponding signal, to use diffracted rays generated according to pitches of optical tracks of an optical disc having different track pitches by switching to a predetermined combination in each of a phase different detection method (DPD) and a push pull method (PP).