Patent ID: 6898168

Claim:
An optical pickup apparatus for conducting recording and/or reproducing information of an optical information recording medium, comprising: a light source; a converging optical system to converge light flux emitted from the light source on an information recording plane of the optical information recording medium so as to conduct reproducing and/or recording information of the optical information recording medium, the converging optical system comprising an objective lens; and a photo-detector to receive reflected light flux from the information recording plane; wherein the converging optical system comprises at least a plastic lens and a spherical aberration deviation correcting element to correct deviation of a spherical aberration of the converging optical system and a numerical aperture of the objective lens at an image-side is 0.65 or more, wherein the spherical aberration deviation correcting element comprises a movable element movable in a direction of an optical axis and wherein the movable element of the spherical aberration deviation correcting element is moved so as to correct a spherical aberration deviation in the objective optical system which comes from a refractive index variation according to a temperature variation in the plastic lens.