| 摘要 |
PURPOSE:To access both faces of an optical disc with one pickup in high speed with simple constitution by providing a polarized beam splitter transmitting a light or reflecting a 90 deg. direction depending on the linearly polarized direction from a laser. CONSTITUTION:When a linearly polarized light in the direction perpendicular to this paper is made incident, the light is reflected to the upper side by a polarized beam splitter 16 and focus is formed on a recording medium 21. Simi larly, the reflected light from a recording medium face is reflected in the splitter 16 and returns to the incident direction 23. When a linearly polarized light in parallel with this paper is made incident, the polarized beam splitter 16 transmits the light beam. The light becomes a circularly polarized light once through a 1/4 wavelength plate 19 and the light beam incident on the reflecting plate 20 is transmitted again through the 1/4 wavelength plate 19 and converted into a linearly polarized light in perpendicular to this paper. Thus, the light beam incident on the splitter 16 is made incident on the 2nd objective lens 18 and focus is formed to the 2nd recording medium face. Further, the light passes through the same path as the incidence and is reflected into a light beam 23. |
