Objective lens, light converging optical system, optical pickup apparatus, and recording and/or reproducing apparatus

摘要

An objective lens for recording and/or reproducing information of an optical information recording medium, is a single lens having an aspherical surface on at least one surface. The objective lens is a finite conjugate type to converge a divergent light flux from a light source onto an information recording plane of the optical information recording medium and satisfies the following formula: <?in-line-formulae description="In-line Formulae" end="lead"?>NA>=0.7<?in-line-formulae description="In-line Formulae" end="tail"?> where NA is an image-side numerical aperture necessary for conducting recording and/or reproducing information of the optical information recording medium.