Patent ID: 8098562
Filing Date: 2012-01-17
Classification: G11B

Abstract:
1. An optical pickup device for performing recording and/or reproduction of information on a plurality of types of optical disks having different thicknesses of protective layer from one another by using light beams of a first wavelength λ 1 , a second wavelength λ 2 and a third wavelength λ 3 which are different from one another, the optical pickup device comprising: a first light source for emitting the light beam of the first wavelength λ a second light source for emitting the light beam of the second wavelength λ a third light source for emitting the light beam of the third wavelength λ an objective lens comprising a diffraction structure, wherein when the light beam having the third wavelength λ wherein the sum of diffraction efficiencies of two diffracted lights of the third wavelength λ wherein the objective lens performs recording or reproduction of information on an optical disk having a thickest protective layer of the plurality of types of optical disks by converging the diffracted light of the third wavelength λ wherein a distance from the objective lens to a surface of the thickest protective layer along an optical axis is shorter than a distance between focuses of the two diffracted lights of the wavelength λ