Patent attributes
An objective lens for use in an optical pickup apparatus for recording and/or reproducing information on a first optical information recording medium having a protective substrate with a thickness t1 using a light flux with a wavelength λ1, on a second optical information recording medium having a protective substrate with a thickness t2 using a light flux with a wave length λ2 and a third optical information recording medium having a protective substrate with a thickness t3 using a light flux with a wavelength λ2, the objective lens includes: an optical surface including a central area and a peripheral area, wherein when the objective optical lens forms the portion of the light flux with the wavelength λ2 passed the central area into a converged spot through a substrate with a thickness t4, the objective optical lens makes a spherical aberration of the converged spot a minimum value.
