Patent ID: 7782735
Filing Date: 2010-08-24
Classification: G11B

Abstract:
1. An optical pickup device that emits laser light beams having different wavelengths to a recording medium, comprising: a semiconductor laser including three laser elements having emitting wavelengths of λ1, λ2, and λ3, where λ1<λ2<λ3, which are housed in the same case such that two laser elements are arranged to sandwich the laser element having the shortest emitting wavelength; a plurality of diffraction gratings that substantially align optical axes of the laser light beams emitted from the laser elements with one another by diffracting action; an objective lens through which the laser light beams emitted from the laser elements converges on the recording medium; and an optical detector that receives the laser light beams reflected from the recording medium, wherein the diffraction gratings include the first diffraction grating is provided to align an optical axis of the laser light beam having the wavelength of λ3 with the optical axis of the laser light beam having the wavelength of λ1 before the laser light beam having the wavelength of λ3 is incident on the objective lens, and the second diffraction grating is provided to align an optical axis of the laser light beam having the wavelength of λ2 with the optical axis of the laser light beam having the wavelength of λ1 after the laser light beam having the wavelength of λ2 is incident on the objective lens but before the laser light beam having the wavelength of λ2 reflected from the recording medium is incident on the optical detector.