| 摘要 |
An objective lens for recording and/or reproducing information of an optical information recording medium, comprises at lest one aspherical surface. The objective lens is a single lens and satisfies the following formulas: 0.85<NA<0.98 0.80<d/f<3.00 0.5<PHI1<5.8 where NA is an optical information recording medium side numerical aperture, d is a thickness (mm) on an optical axis, f is a focal length (mm) for an object locating at an infinite distance, and PHI1 is an effective diameter (mm) of a light source side surface.
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