PHASE SHIFT GRATING FOR PHASE SHIFT DIFFERENTIAL PUSH-PULL TRACKING

摘要

Phase shift grating for phase shift differential push-pull tracking. The present invention relates to a phase shift grating (12) for phase shift differential push-pull tracking (PS-DPP), and to an apparatus for reading from and/or writing to optical recording media (8) using such a phase shift grating (12). According to the invention, the phase shift grating (12) has two phase gratings (121, 122), with grating sections on opposite sides of a line (123) separating the two phase gratings (121, 122) being phase shifted by π, which have curved grating lines which are designed such that the first diffraction order of a divergent light beam (3) diffracted by the phase shift grating (12) essentially is a TEM01 mode. The phase shift grating (12) is suitable for a divergent light beam (3) . Fig. 3