OPTICAL SYSTEM USING BLUE-VIOLET SEMICONDUCTOR LASER AS LIGHT SOURCE, OPTICAL PICKUP DEVICE, AND APPARATUS FOR RECORDING OR/AND REPRODUCING SOUND AND/OR IMAGE

摘要

PURPOSE: An optical system, an optical pickup device, and an apparatus for recording or/and reproducing sound and/or image are provided to correct a change in a focal position of a converging spot of light caused by a change in wavelength of the light by using a simple configuration. CONSTITUTION: An objective system converges a light beam emitted from a light source on an optical recording media. An optical aberration correcting element includes two lenses installed on an optical path between the light source and the objective system and has an adjustable distance in the direction of the optical axis. The optical aberration correcting element has a ring-shaped phase structure formed in at least one lens surface of the optical aberration correcting element. The ring shaped phase structure is non-periodic and has a plurality of concentric ring surfaces k(k=1 to N), and each of the ring surfaces has a stepped part in the direction of the optical axis between the adjacent ring surfaces.