| 摘要 |
A zoom optical system at least includes in the order from an object side: a first lens group having a positive optical power; a second lens group having a negative optical power; and a third lens group having a positive optical power. In zooming from a wide angle end to a telephoto end, a distance between the first lens group and the second lens group is increased, and a distance between the second lens group and the third lens group is decreased. The first lens group includes at least one negative lens element, and the second lens group includes a negative lens element closest to the object side, with a lens surface of the negative lens element being concave toward an image side. The zoom optical system satisfies the following conditional expressions (1) and (2): <?in-line-formulae description="In-line Formulae" end="lead"?>vd<SUB>2</SUB><30 (1)<?in-line-formulae description="In-line Formulae" end="tail"?> <?in-line-formulae description="In-line Formulae" end="lead"?>50>vd<SUB>1n</SUB>>30 (2)<?in-line-formulae description="In-line Formulae" end="tail"?> where vd<SUB>2 </SUB>represents the Abbe number of the negative lens element closest to the object side in the second lens group, and vd<SUB>1n </SUB>represents an Abbe number of a negative lens element, or an average Abbe number of negative lens elements in the first lens group.
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