Patent ID: 8699146
Filing Date: 2014-04-15
Classification: G02B

Abstract:
1. A 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, the distance between said first lens group and said second lens group increases, the distance between said second lens group and said third lens group decreases, and the distance between said third lens group and said fourth lens group changes, wherein said second lens group includes a negative lens element having a concave surface on an image side, a negative lens element having a concave surface on the image side, and a plastic positive lens element having an aspherical surface on at least one side of the plastic positive lens element and having a convex surface on the object side, in that order from the object side, wherein the following condition is satisfied: z2=m2t/m2w; z3=m3t/m3w; m2t designates the lateral magnification of said second lens group when focused on an object at infinity at the long focal length extremity; m2w designates the lateral magnification of said second lens group when focused on an object at infinity at the short focal length extremity; m3t designates the lateral magnification of said third lens group when focused on an object at infinity at the long focal length extremity; and m3w designates the lateral magnification of said third lens group when focused on an object at infinity at the short focal length extremity.