| 摘要 |
A three-group zoom lens includes first, second, and third lens groups, of negative, positive, and positive refractive power, respectively. The second lens group includes a stop and the third lens group moves for focusing. When zooming from the wide-angle end to the telephoto end, the first and second lens groups become closer together and the second and third lens groups become farther apart. The zoom lens preferably satisfies specified conditions that ensure compactness, case of manufacture, and favorable correction of aberrations. The zoom lens includes at least one aspheric lens surface defined by an aspheric lens equation that includes at least one non-zero coefficient of an even power of Y, and at least one non-zero coefficient of an odd power of Y, where Y is the distance of a point on the aspheric lens surface from the optical axis.
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