| 摘要 |
PURPOSE:To detect a focusing error state satisfactorily even when focus setting is performed by making a reflecting plane to reflect split light pass the intersection of the reflecting plane and the optical axis of the split light, and extending the split that at both sides of a straight line in parallel with a knife edge. CONSTITUTION:A photometric sensor 11 to detect each error state and recording state of focusing and tracking is arranged in the optical path of detecting light 10. The bottom plane of a prism 16 is stuck closely with the light receiving plane 13a of a photodiode 13 on a substrate 12, and polarized reflecting planes 17 and 18 which pass the P-polarized component of the detecting light 10 and reflect the S-polarized component are arranged at the inside of the prism 16 so that the end parts of them can be abutted with each other at a position to pass the optical axis of the detecting light 10. And only the S-polarized component of the detecting light 10 is bi-sected in semicircular shape in a direction intersecting orthogonally to the incident direction of the detecting light 10 setting the abutted end part 19 as the knife edge, and bi-sected light are reflected as split light 10a and 10b in a direction in parallel with the substrate 12. The split 10a and 10b pass the intersection of the reflecting planes 21 and 23 and the optical axis of each split light, and are extended at the both sides of the straight line in parallel with the abutting part 19. |
