| 摘要 |
<p>In an optical pickup device (10), a difference of 140mum is provided between a height of a photodetector (15a) and a height of a photodetector (15b). Namely, an optical distance between a polarized hologram (12) and the photodetector (15a) is long, and an optical distance between the polarized hologram (12) and the photodetector (15b) is short. Since a diffracted light of the polarized hologram (12) is astigmatic, the shape of each spot beam of the diffracted light of the polarized hologram (12) on a light receiving plane of the photodetector (15a) can be elongate in an X direction, by adjusting the optical distance between the polarized hologram (12) and the photodetector (15a). Thus, an area of a light receiving part of the photodetector (15a) can be reduced.</p> |
