| 摘要 |
PURPOSE:To miniaturize and lighten a whole device and improve the positioning precision of a knife and light-shielding precision by joining a half coated plano- convex lens where a translucent film is coated on a curved surface to a lambda/4 plate and providing a second light-receiving element receiving a light flux transmitting the half coated plano-convex lens. CONSTITUTION:The light flux which is reflected from a disk recording medium 55 and which penetrates a first polarized beam splitter 53A and the second polarized beam splitter 53B is made incident on the half coated plano-convex lens 1 where the curved surface fitted to the lambda/4 plate 54B jointed to the second polarized beam splitter 53B is coated and the second light-receiving element receives it. The light flux is projected in a direction parallel to the optical axis of a colimate lens 51 and the knife 59 light-shields a part of it, whereby the first light-receiving element 60 receives the remaining flight flux. Thus, the beam splitter becomes unnecessary and the whole device can be miniaturized. Then, the precision of the positioning of the knife can be improved. |
