| 摘要 |
PURPOSE:To reduce the size of a deflection prism in the vertical direction and to make the device thin by sharing the deflection prism for deflecting a laser beam toward an objective lens with a beam forming element for the laser beam. CONSTITUTION:A laser beam outputted through an optical path transforming element 14 is made incident on the first surface 15a of a deflection prism 15, reflected by a second surface 15b and a third surface 15c, transmitted through the second surface 15b and made incident on an objective lens 16. The angle of the first surface 15a of the prism 15 is set so that the laser beam of refracted, elliptical beam pattern becomes a circular beam pattern and the beam pattern of the laser beam transmitted from the second surface 15b becomes a circle. By this constitution the size d1 in the direction of the thickness of the optical path from a fixed optical system to the prism 15 is restricted to the value corresponding to the size of the minor axis of the beam pattern, the size h' of the prism in the vertical direction is reduced and the optical pickup device is made thin. |
