Method for detecting focus dislocation error signal of optical head and optical writing playback apparatus using the same

摘要

The present invention relates to an optical recording to the medium condensing the light beam in the focus of the optical head used for the focus position control of the objective lens shift error signal detection method and an optical recording and reproducing apparatus using the same, the physical track pitch of a plurality of optical recording another in the medium, and an object thereof is to provide a track cross signal by the focus displacement error signal of the optical head capable of detecting the attenuation of focus deviation error signal detection method and the optical recording and reproducing apparatus it. ; A laser diode (3) diffracts in a light beam the diffraction grating (19) projected from the main beam 27 and the ± 1 order of the sub-beams (29a, 29b) split and reflected from the optical recording medium 15 weeks beam 27 and the ± 1 order of the sub-beams (29a, 29b) to the light-receiving element (23, 25a, 25b) receiving the, focus which attenuates the track cross signal on the basis of the photoelectrically converted electrical signal deviation error signal (FES in ) it is detected in the error signal detector 31.