Patent ID: 8659985
Filing Date: 2014-02-25
Classification: G11B

Abstract:
1. An optical pickup for writing and reading data on an optical storage medium that has a land and a groove, the optical pickup comprising: a laser light source for emitting a light beam; a diffractive element for diffracting the light beam to split the light beam into multiple diffracted light beams, the multiple diffracted light beams including a zero-order diffracted light beam for writing data on a track of the land or the groove of the optical storage medium and non-zero-order diffracted light beams for reading the data from the track, the diffractive element comprising first and second diffraction gratings that have mutually different grating vector directions and pitches; a lens for condensing the diffracted light beams onto the optical storage medium; and a photodetector configured to receive at least part of the diffracted light beams reflected from the optical storage medium, wherein the first diffraction grating is arranged to form light beam spots on the same track by the non-zero-order and zero-order diffracted light beams, the second diffraction grating is arranged to form a light beam spot so as to extend to both sides of said track, or arranged to form a light beam spot on one side of said track, by the non-zero-order diffracted light beams, the photodetector is configured to receive reflected light of the light beam spots formed by the diffracted light beam from the first diffraction grating, and configured to receive reflected light of the light beam spot formed by the non-zero-order diffracted light beam from the second diffraction grating so as to read data that has been written on said track, and the diffractive element is arranged so that the light beam spot formed by the non-zero-order diffracted light beam that is produced by the second diffraction grating has a broader width than the light beam spot formed by the non-zero-order diffracted light beam that is produced by the first diffraction grating.