Patent ID: 7929399
Filing Date: 2011-04-19
Classification: G11B

Abstract:
1. An optical pickup device performing at least one of reproduction, recording and deletion of information, on an optical disc having a plurality of recording layers, the optical pickup device comprising: a light source; diffraction means for generating a main beam and a pair of sub beams by diffracting at least a part of the light outputted from the light source, the main beam being a zeroth-order light beam, and the pair of sub beams being a positive first-order light beam and a negative first-order light beam which are located on both sides of the zeroth-order light beam and each has a polarization direction approximately perpendicular to a polarization direction of the main beam; an objective lens for converging the main beam and the pair of sub beams, which are diffracted by the diffraction means, on a desired one of the plurality of recording layers, first photo-detection means for detecting the main beam which is converged by the objective lens and then reflected by the optical disc; and second photo-detection means for detecting the sub beams which are converged by the objective lens and then reflected by the optical disc, wherein the diffraction means includes a substrate having double refractivity and a diffraction grating arranged on a surface of the substrate, outputs an incident ordinary beam as the main beam, and generates the pair of sub beams by diffracting an incident extraordinary beam.