Patent ID: 7092170

Claim:
A three-group zoom lens, comprising, in order from an object side thereof: a first lens group having a negative refractive power, comprising in order from the object side: a negative-power first lens; and a positive-power second lens, wherein the first lens group has no third lens, and the first lens group includes at least one aspherical surface, a second lens group having a positive refractive power, comprising in order from the object side thereof, a positive-power first lens; a positive-power second lens; and a negative-power third lens; wherein the positive-power second lens and the negative-power third lens are cemented together to form a meniscus-shaped cemented lens that faces a convex surface to the object side and the second lens group has aspherical surfaces on at least two surfaces other than a cemented surface of the cemented lens; and a third lens group having a positive refractive power, comprising: a positive-power single lens having two spherical surfaces on the two sides, wherein the third lens group has no second lens, wherein the first lens group moves to the object side after moving to an image side, the second lens group moves only to the object side, and the third lens group moves in an amount different from that of the second lens group upon focusing an object point at infinity from a wide-angle end to a telephoto end, and the third lens group is configured to be movable for focusing, wherein and the following conditional formula are satisfied: 2.3 <L t /f 2 <3.7 1.15 <|f 1 /f 2 |<2.0 where L t is a distance between a lens surface that is closest to the object side of the three-group zoom lens and the image plane at the telephoto end, f 2 is a focal length of the second lens group, and f 1 is a focal length of the first lens group.