| 摘要 |
In a zoom lens of a four-group configuration comprising, successively from the enlargement side, negative, positive, negative, and positive lens groups, the focal lengths of the respective groups are set within predetermined ranges, whereby the lens system can have a compact configuration for its imaging size, the back focus can have an appropriate extent, various kinds of aberration can be made favorable, and the bundle of rays on the reduction side can be made similar to those of a telecentric type. Disposed successively from the enlargement side are a first lens group which is fixed during zooming and has a negative refractive power for focusing, a second lens group having a positive refractive power and a third lens group having a negative refractive power which are moved with a relationship therebetween so as to vary power and correct movement of imaging surface caused by thus varied power, and a fourth lens which is fixed during zooming and has a positive refractive power, while the following conditional expressions: -2.0<F1/F<-0.9,0.65<F2/F<1.4,0.9<F4/F<1.7 are satisfied.
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