Optical system for recording and/or reproducing an optical information recording medium

摘要

An optical system for recording or reproducing information in an optical information recording medium, includes: a light source having a wavelength lambda thereof; an objective lens; tracking device for tracking the objective lens by moving the objective lens in a direction perpendicular to an optical axis of the optical system; and a coupling lens optical system including at least one plastic lens and having a positive focal length, and being provided between the light source and the objective lens for guiding a light emitted from the light source to the objective lens. A maximum amount of change in a wavefront aberration of the coupling lens optical system in a numerical aperture corresponding to a maximum amount of tracking is 0.02 lambda rms or less.