| 摘要 |
Provided is an objective lens for which expressions 0.83<(pM/pL)<1.17 and 0.83<(pM/pT)<1.17 or expressions 0.80<(pM/pL)<1.20 and 0.86<(pM/pT)<1.14 are satisfied, where pL is the ratio of fifth-order spherical aberration to third-order spherical aberration, the spherical aberrations being caused by a difference in the thickness of a cover layer of an optical recording medium, pT is the ratio of fifth-order spherical aberration to third-order spherical aberration, the spherical aberrations being caused by a change in the temperature of an environment of the objective lens, and pM is the ratio of fifth-order spherical aberration to third-order spherical aberration, the spherical aberrations being caused by a change in incident magnification.
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