| 摘要 |
PURPOSE:To reduce a reflected return light to a light source from a polarizing beam splitter or a phase-shifting plate by installing the polarizing beam splitter or the phase-shifting plate, or both of them so that a normal line of its boundary face is inclined against the beam advancing direction. CONSTITUTION:A polarizing beam splitter (PBS) consisting of a 45 deg.-90 deg.-45 deg. prism is installed so that a normal line of its boundary 24 makes a small angle delta1 against the advancing direction of an optical beam 30a, and a phase-shifting plate 20 is installed so that a normal line of its boundary face makes an angle delta2 against the advancing direction of the optical beam 30a. The optical beam 30a emitted from a light source 18 is made incident to the BPS19a, and beams of reflected light 31, 32 from the boundary faces 24, 25 advance in the direction of an angle of 2delta1 with the optical beam 30a. In the phase-shifting plate 20, too, beams of reflected light 33, 34 by boundary faces 27, 28 advance in the direction of an angle of 2delta2 with the optical beam 30a. With respect to a regular reflected light beam 30b from an information recording carrier 21, as well, the same relation is formed, and the reflected return light to the light source is reduced. |
