| 摘要 |
PROBLEM TO BE SOLVED: To provide a zoom lens suitable for a photographing system using a solid-state image pickup element, constituted of a small number of lenses, especially, suitable as a collapsible zoom lens and having excellent optical performance that a variable power ratio is about 3. SOLUTION: In the zoom lens provided with three lens groups, that is, a 1st lens group having negative refractive power, a 2nd lens group having positive refractive power, and a 3rd lens group having positive refractive power in order from an object side and performing variable power by changing space between the respective groups, the 1st lens group is constituted of two lenses, that is, one negative lens and one positive lens, and the 2nd lens group is constituted of three lenses, that is, a positive lens whose both lens surfaces are convex and a doublet consisting of a negative lens and a positive lens in order from the object side, and the 3rd lens group has at least one positive lens. The zoom lens satisfies a condition: 1.5<f2/fw<2.5 when it is assumed that the focal distance of a wide angle end is fw and the focal distance of the 2nd lens group is f2. COPYRIGHT: (C)2004,JPO
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