| 摘要 |
An optical element-for use in an optical pickup apparatus for converging a light flux onto an information recording plane of an optical information recording medium, is provided with an optical path difference providing section divided coaxially around an optical axis so as to form a plurality of ring-shaped zones; and a refracting section optimizing a spherical aberration of a converged light spot of a light flux which has the operating reference wavelength lambd0 and is converged onto the information recording plane. The optical element converges an incident light flux having the operating reference wavelength lambd0 onto the information recording plane with almost no aberration, and the following formula is satisfied: |DELTAfB(lambd-lambd0)|<2000
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