| 摘要 |
An objective lens comprises an inner optically functional region an inner optically functional region allowing a light flux to pass through for conducting recording and/or reproducing information for a first and second optical information recording mediums, an outer optically functional region allowing a light flux to pass through for conducting recording and/or reproducing information for the first optical information recording medium; and a diffractive structure provided on the outer optically functional region. The objective lens satisfies the following formulas: lambd>700 nm, NA1>0.65 and t1<t2 wherein lambd is a wavelength, NA1 is a numerical aperture, t1 and t2 are a thickness of a transparent base board of the first information recording medium and the second information recording medium.
|
