| 摘要 |
PURPOSE:To record and reproduce with high accuracy by providing an optical system in which a laser light source and a photodetector are placed so as to be opposed to each other, and using a laser luminous flux whose sectional shape is an ellipse. CONSTITUTION:An elliptical diffusion laser luminous flux which is radiated from a semiconductor laser light source 7 is converted to parallel rays whose sectional shape is an ellipse by a condensing lens 6, and made incident on a polarizing prism 5, and reflected by a reflecting plate 9 after passing through a 1/4 wavelength plate 3 through the polarizing prism 5. This reflected light is given to cylindrical lenses 4, 4', and these lenses changes said sectional shape to a circle from an ellipse. In this way, the laser luminous flux whose section is a circle, which has been made incident on a lens 2 brings a light whose very small section is a circle, to an image formation on a disk 1 by the lens 2. This reflected light is given to the lenses 4, 4' again through the lens 2 and the wavelength plate 3, reflected by the prism 5, and sent to a photodetector 12. In such a way, recording and reproducing can be executed easily with high accuracy. |
