| 摘要 |
A zoom optical system comprises a lens group 1 having one negative lens component and a lens group 2 wherein a distance on the optical axis between the lens group 1 and the lens group 2 is changed for magnification purpose. The negative lens component consists of a cemented lens of positive lens and a negative lens, and when a straight line expressed by thetagFp=alphapxnudp+betap (alphap=-0.00163) is set up in a rectangular coordinate system in which a horizontal axis is expressed by nudp and an vertical axis is expressed by thetagFp, nudp and thetagFp of the positive lens are included in domains specified by the following conditions. <?in-line-formulae description="In-line Formulae" end="lead"?>0.6400<betap<0.9000<?in-line-formulae description="In-line Formulae" end="tail"?> <?in-line-formulae description="In-line Formulae" end="lead"?>3<nudp<27<?in-line-formulae description="In-line Formulae" end="tail"?> here, theta gFp is a ratio of a partial dispersion (ng-nF)/(nF-nC) of the positive lens LAP; nudp is Abbe number (nd-1)/(nF-nC) of the positive lens LAP; nd, nC, nF, and ng are refractive indices of d,C,F and g line, respectively.
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