Patent ID: 6580564
Filing Date: 2003-06-17
Classification: G02B

Abstract:
A wide-angle zoom lens comprising five lens groups of negative, positive, positive, negative, and positive refractive power, respectively, in sequential order from the magnification side, wherein:the first lens group is fixed during zooming and moves during focusing; the second, third and fourth lens groups are each moved along the optical axis such that the spacing between these lens groups varies for zooming and correction of what would otherwise be excessive curvature of field caused by zooming; the fifth lens group is fixed during zooming; said first lens group is formed of, in sequential order from the magnification side, a first lens subgroup having negative refractive power and a second lens subgroup having negative refractive power, each of said lens subgroups moving relative to the other lens subgroup as well as along the optical axis during focusing; and the following Conditions are satisfied 1.52/f<4.0 2.03/f<5.0 1.55/f<3.0 âˆ’1.81/f0.9 0.41/f1A<1.0 wheref is the focal length of the zoom lens at the wide-angle end, f1 is the focal length of the first lens group, f2 is the focal length of the second lens group, f3 is the focal length of the third lens group, f5 is the focal length of the fifth lens group, and f1A is the focal length the first lens subgroup of the first lens group.