| 摘要 |
PURPOSE:To decrease the number of optical components and to facilitate manufacturing by using a prism comprising one optical base applying beam form- shaping and returned light branching on one and same face. CONSTITUTION:An incidence face for beam shaping and a face reflecting a returned light from a recording medium are formed as one and same face. The prism 3 comprising an optical base is used. A laser beam emitted from a semiconductor laser 1is a collimated light via a collimate lens 2 and made incident in a face (d) of the prism 3 in terms of (p) polarized light. In transmitting through the face (d), the elliptic rate the laser beam is improved, the transmitted light transmits again through an objective lens 5 and a 1/4 wavelength plate 4 and transmits further through the prism 3 and is made incident in the face (d). Since the incident light (i) in this case is reciprocated through the 1/4 wavelength plate 4, the (s) polarized light is obtained to the face (d) and the light is almost reflected in the base (d) and its reflected light is made incident in a single lens 7. |
