| 摘要 |
According to the present invention, a tracking error signal can be obtained with good stability by the three-beam differential push-pull method even if the track guide groove direction of the optical disc changes as viewed from the objective lens. An optical pickup 30 according to the present invention includes: a grating element 110 for splitting light emitted from a light source 121 into multiple light beams including zero-order, −first-order and +first-order diffracted light beams; an objective lens 118 for condensing the zero-order and ±first-order diffracted light beams, which have come from the grating element 110, onto an optical disc; and a photosensor 101 with multiple photodetectors for receiving respectively the three diffracted light beams reflected from the optical disc. The grating element 110 is designed so that when measured perpendicularly to tracks on the disc, sub-light beam spots formed on the disc by the ±first-order diffracted light beams are larger than a main light beam spot formed on the disc by the zero-order diffracted light beam. |
