OPTICAL LENS SYSTEM AND SCANNING DEVICE PROVIDED WITH SUCH A SYSTEM

摘要

In a lens system for focusing a divergent beam (7) in a small spot (18) and comprising a collimator lens (9) and an objective lens (10), the collimator lens is composed of a positive plastics lens element (31) and a negative glass lens element (32). This collimator corrects the temperature-dependent spherical aberration of the objective lens. This lens system is very suitable for a scanning device and an apparatus for reading/writing high-density optical discs (2, 3).