| 摘要 |
PROBLEM TO BE SOLVED: To provide a zoom lens that satisfactorily ensures balance among compactness, variable power ratio, and optical performance. SOLUTION: The zoom lens includes, in the order starting from the object side, a first lens group G1 with positive refractive power, a second lens group G2 with negative refractive power, a third lens group G3 with positive refractive power, and a fourth lens group G4 with positive refractive power. When zooming takes place from the wide-angle end to the telephoto end, the gap between the first and the second lens groups G1 and G2 increases, the gap between the second and the third lens groups G2 and G3 decreases, and the gap between the third and the fourth lens groups G3 and G4 changes. The first lens group G1 comprises one lens with positive refractive power. The second lens group G2 comprises a lens with negative refractive power and a lens with positive refractive power, in this order starting from the object side. The lens with the negative refractive power in the second lens group G2 is concave on both of its sides. The third lens group G3 comprises, in the order starting from the object side, a lens with positive refractive power, a lens with positive refractive power, and a lens with negative refractive power. The focal distance of a combination of the second and the third lens groups G2 and G3 is negative at the telephoto end. COPYRIGHT: (C)2008,JPO&INPIT
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