Objective lens, optical system and optical pickup apparatus

摘要

An optical system for use in an optical pickup apparatus has a chromatic aberration correcting element having plural ring-shaped zones divided with a stepped section in such a way that one of the neighboring ring-shaped zones located apart from the optical axis has a longer optical path than the other one located closer to the optical axis, and an objective lens having plural ring-shaped zones divided with a stepped section shaped in the optical axis direction in such a way that the stepped section causes a optical path difference between light fluxes having passed through the neighboring ring-shaped zones. The ring-shaped zonal structure of the chromatic aberration correcting element corrects a deviation of a focal point caused by the objective lens due to a wavelength fluctuation of an incident light flux coming into the optical system.