Patent ID: 7639431

Claim:
A zoom lens comprising, in order from an object side to an image side thereof, a first lens group of positive refracting power, a second lens group of negative refracting power, and a third lens group of positive refracting power, with an aperture stop located in a space between said second lens group and said third lens group, wherein: upon zooming from a wide-angle end to a telephoto end of the zoom lens, said first lens group, said second lens group, and said third lens group each moves in unison, said second lens group moves toward the object side after moving toward the image side, and at the telephoto end with respect to the wide-angle end, said first lens group is positioned closer to the object side, and said third lens group is positioned closer to the object side; said first lens group comprises, in order from the object side, one negative lens, and one or two positive lenses, wherein a total number of lenses in said first lens group is 3 or less; said second lens group comprises, in order from the object side, a first negative meniscus lens convex on the object side, a second negative lens wherein an image side surface is larger in an absolute value of a paraxial curvature than an object side surface, and a third positive lens wherein an object side surface is larger in an absolute value of a paraxial curvature than an image side surface, wherein a total number of lenses in said second lens group is 3; upon focusing from a far object to a near object, the second lens group moves; and said zoom lens is a three-group zoom lens that satisfies the following conditions: −0.1 <m 2 /f t <0.4 (1) −1.3<( r 2g3 +r 2g4 )/( r 2g4 −r 2g3 )<−0.65 (2) where, f t is a focal length of the whole zoom lens system at the telephoto end, m 2 is an amount of movement of the second lens group at the telephoto end with respect to the wide-angle end with a plus sign indicative of a displacement of the second lens group toward the object side, r 2g3 is a paraxial radius of curvature of the object side surface of the second negative lens in the second lens group, and r 2g4 is a paraxial radius of curvature of the image side surface of the second negative lens in the second lens group.