| 摘要 |
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 lambda1, on a second optical information recording medium having a protective substrate with a thickness t2 using a light flux with a wave length lambda2 and a third optical information recording medium having a protective substrate with a thickness t3 using a light flux with a wavelength lambda2, 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 lambda2 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.
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