| 摘要 |
PROBLEM TO BE SOLVED: To provide an objective lens used for an optical pickup device using two laser light sources and having an interchangeability with reference to plural optical information recording media, capable of satisfactorily keeping coma aberration at reproducing/recording from/on both plural optical information recording media, to provide an optical pickup device including the objective lens, and to provide a method for adjusting the position of the objective lens in the optical pickup device. SOLUTION: The objective lens 16 satisfies a sine condition at the maximum numerical aperture, and also, the lens is provided with the 5th order coma aberration within a prescribed extent at the maximum numerical aperture in a specific direction with reference to a position reference part. By adjusting the 5th order coma aberration appearing at the maximum numerical aperture within a prescribed extent, the total 3rd order coma aberration as much as a prescribed amount can be obtained at the prescribed numerical aperture which is equal to or below the maximum numerical aperture. Besides, as for the optical pickup device, by controlling the 5th order coma aberration so that it may appear in the specified direction with reference to the position reference part, the objective lens is easily adjusted at assembling the objective lens in the device, and also, the objective lens is positioned with reference to the 2nd light source so that off-axial 3rd order coma aberration and the 3rd order coma aberration which is caused by providing the 5th order coma aberration of the prescribed amount at the maximum numerical aperture may counterbalance each other. |
