| 摘要 |
PURPOSE:To obtain a reproduced signal with high S/N by providing a rotary actuator that has a fulcrum in the center of curvature of principal direction of radial direction of an optical disk substrate, mounting an optical head on the rotary actuator and shifting the optical head in radial direction. CONSTITUTION:When an optical head 2a is mounted on a swing arm 3, and rotated around the fulcrum 4 of the swing arm, the head is shifted from inner circumference to outer circumference of an optical disk substrate 1 and comes to a position of an optical head 2b shown by dotted lines. At this time, the direction of the plane of linear polarization of outgoing light of the optical head 2b is slanted from radial direction 14 of the optical disk substrate 1. When the distance from the fulcrum 4 of the swing arm is made to the length of the swing arm, it is possible to make the slant of the plane of linear polarization of radial direction follow the slant of principal direction of radial direction by changing the length and position of the fulcrum 4 of the swing arm. Thus, reproduced signals with high S/N can be obtained without influenced by double refraction of the substrate.
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