| 摘要 |
Theme To inhibit the lens aberration in an objective lens for recording and reproducing optical information, which is composed of a molded aspherical single lens, while attaining at the same time good lens productivity, and also to ensure excellent optical properties and to obtain a high production efficiency in a mold processing step and a press molding step conducted to manufacture the lens. Means for Solving the Problems An objective lens 1 is a lens wherein a convex aspherical surface is formed at the first surface and a numerical aperture NA satisfies the condition, NA>=0.8. It is preferable to have an aspherical surface also at the second surface. A molding material that was premolded to a prescribed shape and is in a heated and softened state is press molded by using a pair of upper and lower molds having opposing molding surfaces, a molding surface shape is transferred by using a spherical molding material with a radius r and pressing the molding material between a pair of upper and lower molds, and the paraxial curvature radius R of the convex aspherical surface satisfies the following relation r/R<=1.35. The objective lens optical system comprises an objective lens 1 and a cover glass (CG) 2.
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