| 摘要 |
PROBLEM TO BE SOLVED: To obtain a variable focal-length lens system small in size and suitable for larger power variation by making a lens system of five-group constitution meet specific conditions. SOLUTION: This lens systems is composed of a 1st lens group G1 with positive refracting power, a 2nd lens group G2 with negative refracting power, a 3rd lens group G3 with positive refracting power, a 4th lens group G4 with positive refracting power, and a 5th lens group G5 with negative refracting power. Then the lens system meets conditions of 0.2<D1t/f1<0.3 and 0.57<D4w/|f5|<0.63, Here, D1t is the on-axis air interval between the 1st lens group G1 and 2nd lens group G2 in the telephoto state. Then D4w is the on-axis air interval between the 4th lens group G4 and 5th lens group G5 in the wide-angle state. Further, f1 is the focal length of the 1st lens group G1 and f5 is the focal length of the 5th lens group G5.
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