| 摘要 |
PROBLEM TO BE SOLVED: To simplify and miniaturize an entire optical pickup device and reduce costs by simplifying a signal detecting system in a multi-wavelength optical pickup for individually recording and reproducing to/from plural optical recording media differing in applied wavelengths. SOLUTION: This multi-wavelength optical pickup device is an optical pickup device used in common to optical recording media 7, 8 differing in the wavelength for the use, and is provided with plural light sources 1, 2 which differ in the wavelength from each other and are selectively used according to the wavelengths used for the optical recording media, one or more object lenses 6 for condensing luminous fluxes from each light source 1, 2 on the recording surfaces of the corresponding optical recording media 7, 8 as light spots, a hologram element 9 to which the return luminous fluxes from each optical recording medium 7, 8 are made incident in common and which acts on each return luminous flux by specified diffraction, and a single photo-detector 10 which receives the luminous fluxes diffracted by this hologram element 9 and generates a predetermined signal. The hologram element 9 is a combination of plural holograms H1, H2 optimized in the holographic action corresponding to each luminous flux wavelength emitted from the plural light sources 1, 2. |
