| 摘要 |
An optical pickup device includes three laser light sources, one objective lens, and a beam shaping mirror. The beam shaping mirror converts light intensity distribution of the laser beams having the respective wavelengths from an elliptic shape to a circular shape by inputting the respective laser beams from a transmission surface, reflecting the laser beams by a reflection surface that is not parallel to the transmission surface and outputting the laser beams from the transmission surface. Two kinds of diffraction gratings are formed on the reflection surface and the plurality of diffraction gratings are formed alternately and side by side. The two kinds of diffraction gratings diffract the laser beams having two out of the three wavelengths such that dispersion by the refracting action at the transmission surface is canceled out using the dispersion by the diffracting action at the reflection surface.
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