| 摘要 |
PURPOSE: A zoom lens system is provided which has a high zoom performance capable of achieving an appropriate optical performance over the whole focus distance range. CONSTITUTION: According to the zoom lens system comprising a positive first lens group(10), a negative second lens group(20), a positive third lens group(30) and a negative fourth lens group(40) in this order from an object, zooming is performed by moving each of the above first through fourth lens groups in the optical axis direction. And the above zoom lens system satisfies the following conditions "1.1<f23T/f23w<1.8, 0.2<LD23W/fw<0.45, 0.01<(D23W-D23T)/fw<0.05" wherein f23W designates the combined focal length of the second and third lens groups at the short focal length extremity, and f23T designates the combined focal length of the second and third lens groups at the long focal length extremity, and LD23W designates the distance between the most object-side surface of the second lens group and the most image-side surface of the third lens group at the short focal length extremity, and fw designates the focal length of the entire zoom lens system at the short focal length extremity, and D23W designates the axial air-distance between the second lens group and the third lens group at the short focal length extremity, and D23T designates the axial air-distance between the second lens group and the third lens group at the long focal length extremity.
|
