| 摘要 |
PURPOSE:To reduce the size of a pickup and simplify its adjustment by utilizing a polarizing beam splitter as 4-terminal network, and superposing the optical path between a semiconductor laser and the polarizing beam splitter as well as between the polarizing beam splitter and a photodetector virtually perfectly spacially. CONSTITUTION:The linearly polarized light emitted from a semiconductor laser 1 is reflected by a polarizing beam splitter 4 through a collimating lens 2, and is made incident to a grating 11 through a 1/4 wavelength plate 51. The diffracted light thereof passes through the plate 51, the beam splitter 4 then through a 1/4 wavelength plate 52 and is condensed onto a disc surface 21 by a condenser lens 6. The reflected light thereof goes backward, is reflected by the splitter 4, passes through a 1/4 wavelength plate 53 and is made incident to a cylindrical lens which is inclined slightly. The reflected light thereof passes through the splitter 4, and is condensed at a photodetector 9 located in the position slightly differing from the laser 1 by the lens 2. Thereby, the pickup is made small in size and its adjustment is simplified. |
