Optical system for recording and reproducing for use in optical information recording medium

摘要

An optical system for recording or reproducing of information to or from an optical information recording medium, includes a light source, a coupling lens for converting a diverging light emergent from the light source to a converging light, and an objective lens for further converging the converted converging light and for focusing on an information recording surface of the optical information recording medium. A lateral magnification Mc of the coupling lens on an image side for a light source side and a numerical aperture NAo on the light source side of the coupling lens satisfy the following expressions respectively, -7.0