| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a phase shift grating for phase shift differential push-pull tracking. <P>SOLUTION: The present invention relates to the phase shift grating 12 for phase shift differential push-pull (PS-DPP) tracking and an apparatus for performing playback and/or recording in an optical recording medium 8 using such phase shift diffraction grating 12. The phase shift grating 12 has two phase gratings 121 and 122, and diffraction grating parts on both sides of line 123 which separates the two phase gratings 121 and 122, phase-shift by π. The two phase gratings 121 and 122 have a curved grating line designed so that first diffraction order of a divergent light beam 3 diffracted by the phase shift grating 12 substantially becomes a TEM01 mode. The phase shift grating 12 is suitable for a divergent light beam 3. <P>COPYRIGHT: (C)2008,JPO&INPIT |
