Patent ID: 7852735
Filing Date: 2010-12-14
Classification: G11B

Abstract:
1. An optical pickup device for irradiating an optical disk having a plurality of recording layers in a laminated direction with a laser beam, the optical pickup device comprising: a light source which emits the laser beam; a diffraction grating which divides the laser beam into a main beam and two sub-beams; an objective lens which causes the main beam and the two sub-beams to converge on a target recording layer among the plurality of recording layers; a photodetector including three light receiving units for separately receiving the main beam and the two sub-beams reflected from the target recording layer; a beam branching element which separates the laser beam traveling from the light source toward the objective lens and the reflected light toward the photodetector; and a diffraction element disposed between the beam branching element and the photodetector to further segment an interference fringe of light reflected from a recording layer except the target recording layer on the light receiving unit, the interference fringe being generated by optical action in the diffraction grating.