Patent ID: 7443780

Claim:
An optical pickup device comprising: a first light source for emitting a first light beam having a first wavelength generally alone an optical axis; a second light source for emitting a second light beam having a second wavelength different from the first wavelength generally along the optical axis; a beam splitter disposed on the optical axis in order to reflect and deflect the first and second light beams by 90° relative to the optical axis along a first reflect/deflect optical axis and a second reflect/deflect optical axis extending parallel to the first reflect/deflect optical axis; a two-type optical recording medium disposed on and extending perpendicularly to the first reflect/deflect optical axis, the optical recording medium having two signal recording surfaces; an objective lens disposed on the first reflect/deflect optical axis for focusing said first light beam or said second light beam from the beam splitter to the signal recording surface of the optical recording medium of a first type matching to the first wavelength or that of the optical recording medium of a second type matching to the second wavelength, whichever appropriate; a photodetector for detecting the light beam focused on the signal recording surface of the optical recording medium of the first type or that of the optical recording medium of the second type, whichever appropriate, by the objective lens and reflected by the signal recording surface; and a diffraction element disposed on the second reflect/deflect optical axis between the beam splitter and the photodetector, the diffraction element carrying a pair of diffraction gratings arranged on the opposite surface planes of a single plate of a diffraction medium; at least either the first light beam adapted to be used for reading information signals from the signal recording surface of the optical recording medium of the first type and reflected by the reflecting surface or the second light beam adapted to be used for reading information signals from the signal recording surface of the optical recording medium of the second type and reflected by the reflecting surface being diffracted by the diffraction element, the first reflected light beam and the second reflected light beam being focused to a same spot on a light receiving surface of the photodetector.