| 摘要 |
PROBLEM TO BE SOLVED: To obtain a compact zoom lens reduced in its distortion aberration, power chromatic aberration and the variation of on-axis chromatic aberration due to zooming by forming at least one of the object side and image face side as an approximately telecentric form with respect to a lens constituted of three groups. SOLUTION: The lens system consists of a 1st group Gr1 having positive power, a 2nd group Gr2 having positive power and a 3rd group Gr3 having positive power which are arranged successively from the object side. At least one of the object side and image face side of the lens system is approximately telecentric. Thus the 1st and 3rd groups Gr1, Gr3 are constituted of groups having positive power. It is preferable to satisfy 0.2<f3/fβW<3.0. The f3 is the focal distance of the 3rd group and the fβW is the focal distance of the whole system on the smaller power side. The inequality regulates a suitable condition for satisfying an approximately telecentric state.
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