Importance

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Abstract

A zoom optical system includes a negative first lens group having a first deflection optical element, a positive second lens group, a positive third lens group, a positive fourth lens group, and a second deflection optical element, in that order from the object side. The first lens group is provided at a fixed position relative to an imaging plane. Zooming is performed by moving at least the second and third lens groups so that distances between adjacent lens groups of the first through fourth lens groups change. The third lens group is a focusing lens group which moves along the optical axis during focusing. The following condition (1) is satisfied:

description='In-line Formulae' end='lead'0.2<f3/f4<1.0  (1),description='In-line Formulae' end='tail'

wherein f3 designates the focal length of the third lens group, and f4 designates the focal length of the fourth lens group.

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First Claim