| 摘要 |
PROBLEM TO BE SOLVED: To realize an excellent optical performance by reducing the size and weight of a focus lens group, thereby performing speedy, quiet focusing, and by correcting a field curvature satisfactorily when power is varied.SOLUTION: A zoom lens system comprises, in order from an object side, a first lens group of positive refractive power, a second lens group of negative refractive power, and a subsequent lens group of positive refractive power. At least the first lens group and at least part of the subsequent lens group in the zoom lens system move such that when power is varied from a wide end to a tele-end, an interval between the first lens group and a second lens group increases and an interval between the second lens group and the subsequent lens group decreases. In the zoom lens system, the second lens group comprises, in order from an object side, a 2a-th lens group of negative refractive power, which is immovable when focusing takes place, and a 2b-th lens group of negative refractive power, which is moved in the direction of an optical axis when focusing takes place. The subsequent lens group of positive refractive power comprises at least two lens groups that change the interval between them when power is varied from a short focal distance end to a long focal distance end. |
