| 摘要 |
A three-group zoom lens includes, in order from the object side, first, second and third lens groups having negative, positive and positive refractive power, respectively. During zooming from the wide-angle end to the telephoto end, the second lens group moves monotonically toward the object side while moving closer to the first lens group and farther from the third lens group, and the first and third lens groups reverse directions to define curved paths. The third lens group is closer to the object side at the wide-angle end and moves toward the object side for close focusing. The focal lengths of the zoom lens and its lens groups, the zoom ratio, the length of the zoom lens, and the half-field angle at the wide-angle end satisfy certain conditions in order to achieve a zoom ratio of at least three with favorable correction of aberrations.
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