Optical system for recording and reproducing an optical 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 of the objective lens in which a wavefront aberration within a Marechal criterion is minimum, satisfies the following conditional expression, $where\; M\; represents\; the\; lateral\; magnification\; of\; the\; objective\; lens.\mathop{\mathrm{image}}$