Patent ID: 6141156
Filing Date: 2000-10-31
Classification: G02B

Abstract:
A zoom lens having an antivibration function and capable of forming an image of an object over a zooming range from a maximum wide-angle state to a maximum telephoto state, comprising, objectwise to imagewise along an optical axis:a) a first lens group having positive refractive power;b) a second lens group, serving as an antivibration lens group, having negative refractive power and comprising at least three lens sub-groups each having negative refractive power, and wherein one of said at least three lens sub-groups is movable substantially perpendicularly to the optical axis, said antivibration lens group including a cemented lens comprising a positive lens and a negative lens;c) at least third and fourth lens groups, wherein all said lens groups are separated by respective spacings which change when zooming from the maximum wide-angle state to the maximum telephoto state; andd) wherein the following conditions are satisfied:1.0<.vertline.f2B.vertline./.vertline.f2.vertline.<3.7where f2B is a focal length of said one of said at least three lens sub-groups and f2 is a focal length of said second lens group;0.1<.vertline.Na-Nb.vertline.where an Na is an index of refraction of said positive lens of said cemented lens with respect to d-line wavelength light and Nb is an index of refraction of said negative lens of said cemented lens with respect to d-line wavelength light;-0.5<(R2+R1)/(R2-R1)<0.5where R1 is a radius of curvature of a most objectwise lens surface of said antivibration lens group and R2 is a radius of curvature of a most imagewise lens surface of said antivibration lens group;1.5<FNO.sub.T .multidot.f1/fT<3.0where fT is an overall focal length of the zoom lens in said maximum telephoto state, FNO.sub.T is an F-number of the zoom lens in said maximum telephoto state, and f1 is a focal length of said first lens group; and0.3<.vertline.f2.vertline./fW<0.7where fW is an overall focal length of the zoom lens in said maximum wide-angle state.