| 摘要 |
PURPOSE:To reduce cost and to improve an optical characteristic by using a composite function prism constituted of a single prism beam shaping a luminous flux and provided with a surface separating a reflection beam from a light source beam. CONSTITUTION:A laser beam outputted from a semiconductor laser element 21 is converted to parallel beams by a coupling lens 22, and are made incident on the surface 23a of the composite function prism 23 of a triangular column shape whose section is a right angled isosceles triangle to be refracted. At the time of the refraction, the luminous flux is beam shaped, and is emitted from the surface 23b. Then, an outgoing beam is polarized by a polarizing prism 5, and is led to an objective lens 6 to be converged on an optical recording medium 7. The reflection beam from the medium 7 is reflected by the prism 5 through the lens 6, and is incident on the prism 23 from the surface 23b, and is reflected by the surface 23a, and is emitted from the surface 23c to be led to a detection optical system. Thus, the beam shaping and the function separating the reflection beam from the light source beam are realized by one prism 23, and the number of parts are reduced. |
