| 摘要 |
PROBLEM TO BE SOLVED: To obtain a zoom lens achieving rapid focusing, having a wide viewing angle and a high zoom ratio and accomplishing high optical performance all over the zoom area. SOLUTION: The zoom lens has a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having negative refractive power, a fourth lens group having positive refractive power, and a fifth lens group having negative refractive power in order from an object side to an image side. When zooming, the respective lens groups move independently, and when focusing from an infinity object to a short-distance object, the fifth lens group moves to the image side. When it is assumed that (i) is the order of the lens group counted successively from the object side to the image side, the focal length of the i-th lens group is (fi), the focal length of the zoom lens at a wide angle end is (fw) and the back focus thereof at the wide angle end is (skw), the zoom lens satisfies conditions; 4.0<¾f5¾/fw<10.0 and 0.5<¾f1¾/skw<1.0. COPYRIGHT: (C)2008,JPO&INPIT
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