| 摘要 |
PURPOSE:To prevent the quantity of light from being lost and to improve the life of a light source and the reliability of the titled device by allowing a lens system united by shifting respective optical axes to perform optical deflection and the focusing of an optical detector. CONSTITUTION:Light reflected by a disc 5 is separated from incident light by a beam splitter 3 through an objective lens 4 and then is made arrive at the optical detector 7 divided into 4 parts including the shifted directions of the optical axes through the lens system consisting of lenses 6a, 6b shifted at the optical axes. The lens system 6 is obtained by adhering the convex lenses 6a, 6b so as to be shifted at their plane parts and has two shifted optical axes 9, 10 and the reflected light 8 is made incident to the lens system 6. Since the detector 7 is divided into four detecting elements 7a-7d including the shifted directions of the optical axes 9, 10, the reflected light 8 is condensed on the detecting elements at the points separated by the shifted distances of the optical axes, i.e. the condensing points 11a, 11b of the lenses 6a, 6b. |
