| 摘要 |
The positional displacement of a recording medium results in a spatial filter significantly blocking the diffracted light generated by the recording medium during playback, thus reducing the quantity of diffracted light collected by an optical detector and preventing satisfactory playback signals from being obtained. Further, the position of the spatial filter needs to be fixed in the path of a light ray to remove unnecessary frequency components of a light beam emitted from a light source which stays fixed at the same position during recording. In the present invention, in actuators having at least two spatial filters, one spatial filter is mounted on an actuator having two or more axes so as to move independently from the other spatial filters, and another spatial filter is fixed to a common one-axis actuator. The common one-axis actuator is used to switch the positions of the spatial filters. |
