Kabushiki Kaisha Toshiba

Yasuo Otsubo

Shigeru Hoshina

Hisao Kodama

An objective lens for focusing a laser beam onto an optical information medium is disclosed. The objective lens comprises a lens body and a flange portion arranged on the periphery of the lens body. The surface of the lens body facing the optical information medium is formed with a convex shape having a radius of curvature R as follows: 0.05 m&lt;R&lt;0.5 m. In this way, a dynamic pressure is generated due to the convex-shaped surface and the rotation of the optical disk. This generates a buoyancy which overcomes the maximum acceleration of the objective lens. In this manner, it becomes possible to avoid collision of the objective lens with the optical information medium even in the presence of relative tilts, such as tangential tilts, radial tilts, and shift tilts, between the optical information medium and the objective lens.

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Ibaragi-ken, Japan

Yasuo Otsubo