Patent ID: 8675278
Filing Date: 2014-03-18
Classification: G02B

Abstract:
1. A high zoom-ratio zoom lens system comprising: a positive first lens group, a negative second lens group, a positive third lens group, and a positive fourth lens group, in that order from an object side, wherein upon zooming from a short focal length extremity to a long focal length extremity, at least the first through third lens groups move along an optical axis in a manner so that a distance between said first lens group and said second lens group increases, a distance between said second lens group and said third lens group decreases, and a distance between said third lens group and said fourth lens group increases, wherein an amount of movement of said first lens group during zooming is larger than that of said third lens group, wherein the lens element which is provided closest to the object side within said third lens group has an aspherical surface formed on each side thereof, wherein said third lens group comprises an image-shake correction lens group which is moved in a direction orthogonal to the optical axis to change an imaging position in order to correct image shake, and wherein the following conditions (4), (5) and (6) are satisfied: F1 designates a focal length of said first lens group, F2 designates a focal length of said second lens group, M3t designates a lateral magnification of said third lens group when focusing on an object at infinity at the long focal length extremity, M3w designates a lateral magnification of said third lens group when focusing on an object at infinity at the short focal length extremity, M2t designates a lateral magnification of said second lens group when focusing on an object at infinity at the long focal length extremity, M2w designates a lateral magnification of said second lens group when focusing on an object at infinity at the short focal length extremity, and ν1P1 designates an Abbe number with respect to the d-line of a positive lens element which is provided closest to the object side within said first lens group.