| 摘要 |
PROBLEM TO BE SOLVED: To provide a zoom lens which has a large aperture and a wide field angle and secures sufficiently long back focus even when applied to a system whose picture size is smaller than a 35-mm film size. SOLUTION: The zoom lens includes, in order from the object side to the image side, a negative first lens group, a positive second lens group, a negative third lens group, and a positive fourth lens group. For zooming from the wide angle end to the telephoto end, the lens groups move on an optical axis such that an interval between the first and second lens groups decreases, an interval between the second and third lens group increases, and an interval between the third and fourth lens group decreases. In addition, refractive powers of the second and third lens groups are appropriately set. COPYRIGHT: (C)2009,JPO&INPIT
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