| 摘要 |
An optical pickup device includes a radiation light source (105) for radiating light of two or more different wavelengths, a diffraction element (107), a light collector (103), a hologram element (108), a plurality of photo-detectors (206), and calculation means for calculating outputs from the plurality of photo- detectors (206), so as to respond to the 3-beam method, the phase difference method, the push-pull method, and the 3-beam push-pull method. The plurality of photo-detectors (206) include at least eight photo- detectors (P1 to P8) required for executing the 3-beam method, the phase difference method, and the push-pull method. The calculation means has a switch (212) for switching between a terminal for acquiring a sub-signal of the 3-beam push-pull method and a terminal for acquiring a tracking signal of the 3-beam method.
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