Objective lens, optical pickup device having the same, and recording and/or reproducing apparatus for optical recording medium, equipped with the optical pickup device

Abstract

An objective lens consists of a single lens element. A light source side surface is formed into a convex surface having a large curvature, and an optical recording medium side surface has a small curvature. The both surfaces are formed into aspheric surfaces. Also, the objective lens satisfies the following expressions (1) to (3): 0.70<NA<0.98  (1) 0.70<d/f<3.00  (2) 0.50<g/d<0.80  (3) where NA denotes a numerical aperture of the objective lens on an optical recording medium side, d denotes a thickness, in mm, of the objective lens on an optical axis, and g is a distance, in mm, from a tangential plane that is perpendicular to the optical axis and is tangent to a vertex of the light source side surface of the objective lens, to a center of gravity of the objective lens.

Dependencies are inferred from the claim text.