Patent Number: 7,133,215

Title: Varifocal zoom lens and camera system

Abstract: A varifocal zoom lens includes: a first lens group having a negative refractive power; a second lens group having a positive refractive power, including a cemented lens component L21 formed by combining a positive lens having a convex surface on the object side and a negative lens having a concave surface on an image side and a positive lens component L22 disposed on the image side with respect to the cemented lens component L21, spaced from the cemented lens component L21 by an air space and having a convex surface on the object side and disposed behind the first lens group with respect to an object side; and a third lens group having a positive refractive power and disposed behind the second lens group with respect to the object side. 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 changed from a shortest-focal-length lens state to a longest-focal-length lens state, an aperture stop is disposed between the first and the second lens group, and the second lens group includes and satisfies conditions expressed by: 0.02<D.sub.s/(R22.sub.a-R21.sub.b)<0.1 (1) 0.6<D.sub.a/R21.sub.b<0.8 (2) where D.sub.s is the length of an air space between the cemented lens component L21 and the positive lens component L22, R22.sub.a is the radius of curvature of the surface on the object side of the positive lens component L22, R21.sub.b is the radius of curvature of the surface on the image side of the cemented lens component L21, and D.sub.a is the distance between the aperture stop and the surface on the image side of the cemented lens component L21.

Inventors: Otake; Motoyuki (Saitama, JP)

Assignee: Sony Corporation

International Classification: G02B 15/14 (20060101)

Expiration Date: 2019-11-07 0:00:00