| 摘要 |
PURPOSE:To realize a small-sized constitution having a very small number of parts by arranging an optical element, which corrects the astigmatic difference of transmitted laser emitted light, in the optical path of the laser emitted light from a laser light source. CONSTITUTION:An optical pickup device is provided with a parallel plane plate 51 which is provided at a prescribed angle in the emitted optical path of a laser light source 52 and whose surface facing an optical disk is coated with a multilayered dielectric film, an objective lens 41, a knife edge 42, and a photodetector 60 where respective light reception faces of four-divided photodetectors 61A, 61B, 61C, and 61D are provided with analyzers. In this case, the error of focusing is detected by (A+B)-(C+D) where A, B, C, and D are light detection signals from photodetectors 61A, 61B, 61C, and 61D respectively. |
