| 摘要 |
PROBLEM TO BE SOLVED: To obtain the zoom lens which consists of <=10 lens elements, has various aberrations sufficiently compensated including the distortion and spherical aberration at the short-focus end, and also has a >=×2.5 power variation ratio. SOLUTION: The zoom lens which has at least three lens groups, i.e., a 1st lens group IG with positive focal length, a 2nd lens group 2G with negative focal length, and a 3rd lens group 3G with positive focal length in order from the object side and varies in power by moving the 2nd lens group and 3rd lens group meets a condition of 0.60<(β2 T/β2 W).(β3 W/β3 T)<4.0, whereβ2 W andβ3 W are the lateral magnifications of the 2nd and 3rd lens groups at the short- focus end andβ2 T andβ3 T are the lateral magnifications of the 2nd and 3rd lens groups at the long-focus end. Further, the power variation ratio which is the ratio of the focal lengths at the short-focus end and long-focus end is >=×2.5.
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