Patent ID: 7317676

Claim:
An optical head device, comprising: one or a plurality of laser light sources for emitting a first light beam of a first wavelength λ 1 (400 nm to 415 nm) and a second light beam of a second wavelength λ 2 (650 nm to 680 nm); 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 3 (780 nm to 810 nm); and 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.