| 摘要 |
PURPOSE:To make the constitution of an optical pickup simple, compact and inexpensive by using a composite function prism formed by joining a wedge- shaped prism and a wedge-shaped prism or parallel flat plate prism via a semi transmissive membrane. CONSTITUTION:This composite function prism 3A is constituted by joining the parallel flat plate prism 34 and the wedge-shaped prism 35 having the refractive indices equal to each other via the semi transmissive membrane 36. Illuminating light is refracted by the incident surface of the prism 34, is reflected by the prism surface on the lower side of the prism 35 and is further refracted at the time of emission from the prism 34. Then, a beam shaping function and deflection function are effected by not paralleling but inclining of the incident side surface and the prism surface on the lower side with each other and the effect of two times of refraction. The reflected luminous flux is refracted at the time of incidence on the prism 34, is reflected by the membrane 36, is again refracted by the incident side surface and is emitted as detecting light to the same side as the incident side of the illuminating light. As a result, the structure of the optical pickup is simplified. |
