| 摘要 |
An optical pickup device radiates laser light to a disc having a plurality of recording layers in a direction of lamination. The optical pickup device includes a laser light source, a collimator lens, and an objective lens. The collimator lens changes a spread angle of the laser light emitted from the laser light source. The objective lens converges the laser light having passed through the collimator lens onto the disc. With the laser light in a parallel state having passed through the collimator lens, if a distance f between the laser light source and the collimator lens and a distance L between the collimator lens and the objective lens are in a relation of f<L, the objective lens brings the laser light into focus with minimum spherical aberration at a designed focal position on an inner side of an intermediate position between the foremost and innermost recording layers. |
