| 摘要 |
PURPOSE:To enable the reproducing of recording information by providing a driving device that makes retire a plate of 1/4 wave length from an optical path between a recording medium and a polarization beam splitter when a beam reflected by the recording medium is detected. CONSTITUTION:A beam 13 transmitted a polarization beam splitter 14 transmits an objective lens 15 and if focused on the recording surface of a disk 15. However, when the disk is an optical one, a plate of 1/4 wave length 17 is positioned in the optical path between the polarization beam splitter 14 and the objective lens 15 by the driving device. When the disk 16 is a photomagnetic disk, the plate of 1/4 wave length is made retire from the optical path by the driving device. The beam 13 that is reflected by the disk 16 and transmits the objective lens 15 and farther, reflected by the polarization beam splitter 14 transmits a plate of 1/2 wave length and is made incident on a polarization beam splitter 22. Thereby, it is possible to reproduce the recording information from both of the recording media of reflectance of changeable type and of plane of polarization of rotatable type. |
