Patent ID: 7031076

Claim:
An optical system for use in an optical pickup apparatus, comprising: a chromatic aberration correcting element having a ring-shaped zonal structure including plural ring-shaped zones on at least one optical surface thereof in which neighboring ring-shaped zones are 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 to converge a light flux from the chromatic aberration correcting element onto an information recording plane of an optical disk and having a ring-shaped zonal structure including plural ring-shaped zones on at least one optical surface thereof in which neighboring ring-shaped zones are 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; wherein 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; and the ring-shaped zonal structure of the objective lens corrects a spherical aberration caused by the objective lens due to a wavelength fluctuation of an incident light flux coming into the optical system.