OBJECT LENS, OPTICAL PICKUP DEVICE AND OPTICAL INFORMATION RECORDING/REPRODUCING DEVICE

摘要

A finite conjugate type object lens having interchangeability with a plurality of types of optical disk and being capable of correcting astigmatism occurring due to tracking and astigmatism provided by a light source itself; an optical pickup device and an optical information recording/reproducing device provided with this object lens. The optical pickup device comprises a first light source for outputting a first light flux, and second light source for outputting a second light flux, and a finite conjugate object lens for condensing the first and second light fluxes. The object lens has astigmatism to a light flux with a wavelength lambda1 and is disposed in such a direction that an astigmatism occurring direction decreases the astigmatism of a light flux with a wavelength lambda1 occurring due to tracking. In addition, the astigmatism of the object lens has a minimum value when an image height in the tracking direction of the object lens is within a specified range.