Patent ID: 6437922
Filing Date: 2002-08-20
Classification: G02B

Abstract:
A zoom lens system comprising a plurality of zooming lens groups which are relatively moveable in order to vary the focal length of said zoom lens system,wherein among said plural zooming lens groups, a predetermined zooming lens group which comprises a switching lens group comprising at least two sub-lens groups; wherein one of said sub-lens groups of said switching lens group is made moveable, with respect to other sub-lens groups, to either an object-side end or an image-side end; wherein in a short-focal-length side zooming range from the short focal length extremity to an intermediate switching focal length, said plural zooming lens groups and said predetermined zooming lens group are moved towards said object, while distances among said zooming lens groups are varied, and while said moveable sub-lens group of said predetermined zooming lens group is being made stationary at one of said object-side end and said image-side end; wherein at said intermediate switching focal length, said moveable sub-lens group is moved to the other of said object-side end and said image-side end, and each of plural zooming lens groups and said predetermined zooming lens group are moved towards the image plane; wherein in a long-focal-length side zooming range from said intermediate switching focal length to the long focal length extremity, said plural zooming lens groups and said predetermined zooming lens group are moved towards said object, while distances among said zooming lens groups are varied, and while said moveable sub-lens group is being made stationary at said other of said object-side end and said image-side end; and wherein said zoom lens system satisfies the following condition: mNtâˆ’mNw<0 wherein mNt designates the transverse magnification, at said intermediate switching focal length, of the most image-plane-side zooming lens group among said plural zooming lens groups, under the condition that said moveable sub-lens group of said switching lens group is being made stationary at said other of said object-side end and said image-side end; and mNw designates the transverse magnification, at said intermediate switching focal length, of the most image-plane-side zooming lens group among said plural zooming lens group, under the condition that said moveable sub-lens group of said switching lens group is being made stationary at said one of said object-side end and said image-side end.