Patent ID: 7317676
Filing Date: 2008-01-08
Classification: G11B

Abstract:
1. An optical head device, comprising: one or a plurality of laser light sources for emitting a first light beam of a first wavelength λ an objective lens on which the first and second light beams that are emitted from the laser light source are incident and a diffraction optical element arranged in a light path of the first and second light beams; wherein the diffraction optical element includes a diffraction pattern that causes 5N-th order diffracted light (N is a natural number) to be emitted with respect to the first light beam, and causes 3N-th order diffracted light to be emitted with respect to the second light beam; and wherein the laser light source further emits a third light beam of a third wavelength λ wherein the diffraction pattern of the diffraction optical element causes 5M-th order diffracted light (2M=N, M is a natural number) to be emitted with respect to the third light beam.