| 摘要 |
PROBLEM TO BE SOLVED: To obtain a zoom lens system consisting of a small number of lenses, having superior performance in all the focal distance range, made small in size and having a high zoom ratio by making the entire length of a lens at a long focal distance end to be short and the effective diameter of a front lens to be small. SOLUTION: This zoom lens system is constituted of a 1st positive lens group, a 2nd negative lens group, a 3rd positive lens group and a 4th negative lens group in this order starting from an object side, performs zooming by moving the respective groups in the optical axis direction and satisfies the conditional expressions (1) to (3): (1) 1.1<f23 T/f23 W<1.8 (2) 0.2<LD23 W/fW<0.45 and (3) 0.01<(D23 W-D23 T)/fW<0.05 (f23 W is the combined focal distance of the 2nd lens group and the 3rd lens group at a short focal distance end, f23 T is the combined focal distance of the 2nd lens group and the 3rd lens group at the long focal distance end, LD23 W is the distance from the surface nearest to the object side of the 2nd lens group to the surface nearest to an image side of the 3rd lens group at the short focal distance end, fW is the focal distance of the entire system at the short focal distance end, D23 W is the axial distance between the 2nd lens group and the 3rd lens group at the short focal distance end, and D23 T is the axial distance between the 2nd lens group and the 3rd lens group at the long focal distance end).
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