Patent ID: 7133215

Claim:
A varifocal zoom lens comprising: a first lens group having a negative refractive power; a second lens group having a positive refractive power, consisting of a cemented lens component L 21 formed by combining a positive lens element having a convex surface facing to an object side and a negative lens element having a concave surface facing to an image side and a positive lens component L 22 disposed on the image side of the cemented lens component L 21 , spaced from the cemented lens component L 21 by an air space and having a convex surface facing to the object side and disposed on the image side of the first lens group; and a third lens group having a positive refractive power and disposed on the image side of the second lens group; wherein at least the first and the second lens group are moved and the second lens group is moved toward the object side so as to decrease an interval between the first and the second lens group, when a lens state is changing from a shortest-focal-length lens state for the largest field angle to a longest-focal-length lens state for the smallest field angle, an aperture stop is disposed between the first and the second lens group,and the following conditions are satisfied: 0.02 <D s /( R 22 a −R 21 b )<0.1 (1) 0.6 <D a /R 21 b <0.8 (2) where D s is the length of an air space between the cemented lens component L 21 and the positive lens component L 22 , R 22 a is the radius of curvature of the surface on the object side of the positive lens component L 22 , R 21 b is the radius of curvature of the surface on the image side of the cemented lens component L 21 , and D a is the distance between the aperture stop and the surface on the image side of the cemented lens component L 21 .