| 摘要 |
PROBLEM TO BE SOLVED: To obtain excellent optical performance, to make sensitivity low and to obtain specified back focus by providing a zoom lens with 1st to 5th lens groups and making it satisfy a specified condition. SOLUTION: The 2nd and the 4th groups are moved in an optical axis direction so as to perform variable power and the automatic correction of an image surface associated with the variable power. Assuming that a distance from a 1st lens surface on an object side to a paraxial image surface is TD and the focal distance of an entire system at a telephoto end is fT, the zoom lens satisfies a conditional expression TD/fT<1.2. Assuming that the tertiary coma aberration coefficients of the 3rd group to the 5th group at the telephoto end in the case of setting that the initial value of the angle of an axial marginal light beam at a wide-angle end is 0, the initial value of the height thereof is 1, and the initial value of the angle of an off-axis principal light beam is -1 are II3r, II4r and II5r in order, and the tertiary astigmatism coefficients of the 3rd group to the 5th group at the telephoto end are III3r, III4r and III5r in order, the lens satisfies conditional expressions (II3r)2+(II4r)2 (II5r)2 <2 and (III3r)2+(III4r)2+(III5r)2 <2.
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