| 摘要 |
PROBLEM TO BE SOLVED: To provide a zoom lens suitably used in a digital still camera using a CCD, having a variable power ratio being about 2 to 3 and having high image- forming performance. SOLUTION: This zoom lens is 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 the 2nd lens group is constituted of a positive lens, a doublet consisting of a positive lens and a negative lens, and one lens in order from the object side. In the case of varying power from a wide-angle side to a telephoto side, the power is varied by moving the 1st, the 2nd and the 3rd lens groups on an optical axis so that space between the 1st and the 2nd lens groups may be decreased and space between the 2nd and the 3rd lens groups may be increased. The zoom lens satisfies a conditional expression 0.4<fW/f2<1.0 when the focal distance of the 2nd lens group is defined as f2 and the focal distance at the wide-angle end of an entire optical system is fW.
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