| 摘要 |
PROBLEM TO BE SOLVED: To obtain a zoom lens constituted of a small number of lenses and having high optical performance though its variable power ratio is high such as 20-22. SOLUTION: The zoom lens is constituted of 1st, 2nd, 3rd and 4th lens groups having positive, negative, positive and positive refractive power in order from an object side to an image side, and the 2nd lens group L2 and the 4th lens group L4 are moved in the case of zooming. The 1st lens group L1 is constituted of a 11th negative lens, a 12th positive lens and a 13th positive lens in order from the object side to the image side, the 2nd lens group L2 is constituted of a 21st negative lens, a 22nd negative lens and a 23rd positive lens, the 3rd lens group L3 is constituted of a 31st positive lens whose one or more surfaces are aspherical, and the 4th lens group L4 is constituted of a doublet obtained by bonding a 41st negative lens and a 42nd positive lens. Assuming that the focal distance of an i-th lens group is f<SB>i</SB>and the focal distance of the entire system at a wide angle end is f<SB>W</SB>, the zoom lens satisfies conditional expressions -7.0<f<SB>1</SB>/f<SB>2</SB><-5.5 and 9.4<f<SB>1</SB>/f<SB>W</SB><14.0. COPYRIGHT: (C)2005,JPO&NCIPI
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