| 摘要 |
An objective lens for converging light onto a recording surface of an optical information recording medium in order to perform at least one of recording, reproduction and deletion of information on the optical information recording medium. The objective lens is a bi-convex single lens having at least one aspheric surface, and satisfies the following conditions: 0.8<R1/r1<0.85 and 0.9<d/f<1.1. Here, a numerical aperture NA on the optical information recording medium side of the objective lens satisfies NA≧0.85. R1 is a paraxial curvature radius [mm] on a light source side of the objective lens, r1 is an effective radius [mm] on a light source side of the objective lens, d is a thickness [mm] on the optical axis of the objective lens, and f is a focal length [mm] of the objective lens.
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