| 摘要 |
An optical pickup device divides signal light so as to detect the divided signal light. For example, a photodetector can include a region A and another region B. Among diffracted light diffracted from a track on an optical disc, only zeroth-order diffraction light enters region A, whereas the zeroth-order diffraction light, + first-order diffraction light, and − first-order diffraction light enter region B. A focusing error signal from the photodetector is produced based upon a signal detected by the photodetector, whereas a tracking error signal is produced based upon signals detected from the regions A and B. A stable focusing error signal and a stable tracking error signal can be detected with respect to a dual layer optical disc, or a multi layer optical disc. |
