| 摘要 |
At least one exemplary embodiment is directed to a telephoto type optical system capable of reliably correcting and/or reducing aberrations such as chromatic aberration. The optical system includes a refractive optical element which includes a solid-state material, a negative lens component and a positive lens component, respectively disposed on a front side relative to a pupil, the solid-state material meeting conditions of an Abbe number nud(GNL) and of a partial dispersion ratio thetagF(GNL) as follows: <?in-line-formulae description="In-line Formulae" end="lead"?>-2.100x10<SUP>-3</SUP>.nud(GNL)+0.693<thetagF(GNL)<?in-line-formulae description="In-line Formulae" end="tail"?> <?in-line-formulae description="In-line Formulae" end="lead"?>0.555<thetagF(GNL)<0.9<?in-line-formulae description="In-line Formulae" end="tail"?> Then, a refractive power of the refractive optical element, a mean partial dispersion ratio of a material of the negative lens component, and a mean Abbe number of a material of the positive lens component are properly set.
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