| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a diffraction element which accurately records and reproduces information without deteriorating the information, and also to provide an optical head device using the same. <P>SOLUTION: The optical head device is used for recording and reproducing an optical signal with respect to an optical disk such as a Blu-ray disk and an HD-DVD. The optical head device has a laser beam source generating a laser beam L and the diffraction element 13 rotating a polarization direction of the laser beam L and generating a beam used for tracking control of the optical signal. The diffraction element 13 has a half-wave plate 21 of a single plate made of a quartz substrate which is cut at such an angle that the normal of the principal plane of the quartz substrate forms 90° to an axis Z being a crystal optical axis of a quartz. The diffraction element 13 also has a diffraction grating 22 generating 0th order diffraction beam L0 (main beam) used for reading information and ±1st diffraction beam L±1 (side beam) used for tracking control from the laser beam L formed on the half-wave plate 21. <P>COPYRIGHT: (C)2008,JPO&INPIT |
