| 摘要 |
PROBLEM TO BE SOLVED: To provide a high variable power ratio zoom lens which is a four- group zoom system, that is, positive, negative, positive and positive groups, whose photographic viewing angle at a wide angle end is about 75 degrees, whose f-number at the wide angle end is about 3 to 4, whose f-number at a telephoto end is about 6 to 7, whose variable power ratio is about 10, and which is made small in size and light in weight. SOLUTION: The variable power ratio zoom lens has a 1st lens group having positive refractive power, a 2nd lens group having negative refractive power, a 3rd lens group having positive refractive power and a 4th lens group having positive refractive power in order from an object side. In the case of varying power from the wide angle end to the telephoto end, space between the 1st and the 2nd lens groups is widened, space between the 2nd and the 3rd lens groups is narrowed and space between the 3rd and the 4th lens groups is narrowed, and the 1st, the 3rd and the 4th lens groups are moved toward the object. In the case of focusing, only the 2nd lens group is moved. Then, the zoom lens satisfies a specified condition. COPYRIGHT: (C)2003,JPO
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