| 摘要 |
PURPOSE:To decrease the number of optical system parts and also to make an optical pickup device small in size by containing a semiconductor laser element and a photodetector for detecting a signal, in the same containing body, and also leading the laser light oscillated from the semiconductor laser element to a signal detecting photodetector by a double image prism. CONSTITUTION:A photodetector 16 for detecting a signal is contained in a semiconductor laser 21. When laser light of an outward path of laser light having a polarizing characteristic is made to conform with an ordinary ray characteristic of a double image prism 22, laser light of a return path, namely, laser light which is reflected by a disk 17 and is converted to linearly polarized light from circularly polarized light by a lambda/4 plate 13 becomes an abnormal ray, and passes through the double image prism 22 through an optical path being different from that of laser light of the outward path. Accordingly, a condensed position by a collimator lens 11 of such reflected laser light is shifted from a position of a semicondutor laser element 5. Therefore, when the condensed position of the reflected laser light is made to conform with a position of the photodetector 16 for detecting a signal, which is placed in the semiconductor laser 21, the reflected laser light can be detected by the photodetector 16. |
