| 摘要 |
PURPOSE:To reduce light-sensing elements and to dispense with knife adjustment by integrating a beam shaping prism, a lambda/4 plate, a concave mirror, a lambda/2 plate and optical glass with a polarizing beam splitter and by utilizing the double refraction property of a Wollaston prism. CONSTITUTION:A light flux emitted from a semiconductor laser 1 is made to be a parallel light by a collimate lens 2 and made to be a circular light flux by a beam shaping prism 3 and the flux enters a polarizing beam splitter 4. The light flux entering the splitter 4 is reflected and transmitted through a lambda/4 plate 5, and then it turns to be a circularly polarized light and is condensed on a disk-shaped recording medium 7. The light flux reflected by the medium 7 is transmitted through the plate 5 and falls on a concave mirror 8. The light flux falling on the mirror 8 is reflected and enters a lambda/2 plate 9 and optical glass 10. At which time, an emission surface of the splitter 4 is divided in four, and two sectoral light fluxes are emitted simultaneously and enter a Wollaston prism 11. The two sectoral light fluxes entering the prism 11 correspond to ordinary rays and extraordinary rays respectively, and the ordinary rays are sensed on the objective lens 6 side, while the extraordinary rays are sensed by a light-sensing element 12. |
