| 摘要 |
PROBLEM TO BE SOLVED: To drive a CD-ROM, a magneto-optical disk and a changing type optical disk by deflecting the reflected light from a recording medium in different directions from one another and calculating a focus error signal and a track error signal from individual outputs of a photodetection system. SOLUTION: A light beam from a semiconductor laser is converged via an objective lens 20 on a track 21a of a disk 21, and the refleted light from the disk 21 is incident via the lens 20 on a prism 26 of a signal detection system. Each light beams deflected by the prism 26 are incident upon bisected photodetectors 27-30. The focus error signal is calculated in a calculating part from outputs of the individual detecting parts of the detectors 29 and 30 by a Foucault method. When the track 21a is of a re-writable disk, etc., the track error signal is calculated by a push-pull method. Then, when the track 21a is of a ROM disk, etc., the track error signal is calculated by obtaining a phase difference between a heterodyne signal and an information signal. |
