| 摘要 |
PURPOSE:To detect a focus error signal and a tracking error signal and to reduce the number of parts by arranging a condenser lens between an optical path changing means and an optical detector in a prescribed form and providing plural photodetecting surfaces in the optical detector. CONSTITUTION:A light beam from a light source 10 is passed through a splitter 5, a 1/4 wavelength board 4 and an objective lens 2 and condensed on an optical disk 1 is faint light and the reflected light is passed through a reverse route and separated by the splitter 5. Next, about the half in the upper side of the light is incoming between a surface which is cut by a plain which includes the optical axis of a condenser lens 11, and a plain including a surface which is cut by a parallel surface, and the optical axis. Then, the light receives the operation of and lens 11 and it is condensed on a photo-detecting surface 13 for focus of an optical detector 12 and the remaining half of the reflected light straightly proceeds in a part, where is no lens 11, and it is directly incoming to a photo-detecting surface 14 for tracking. As a result, a focus error and a tracking error are detected. |
