Zoom lens system, imaging apparatus, and camera

Abstract

A zoom lens system according to the disclosure, in order from an object side to an image side, includes a first lens group with positive optical power, a second lens group with negative optical power, and a subsequent lens group composed of at least three lens groups. During zooming operation, the first lens group moves along the optical axis and the second lens group does not move. The second lens group has an aperture stop. The second lens group satisfies following condition (1), −9.0≦fG1/fG2≦−2.0   (1) where fG1 is the focal length of the first lens group, and fG2 is the focal length of the second lens group.

What is claimed is: 
     
         1 . A zoom lens system,in order from an object side to an image side, comprising:
 a first lens group with positive optical power;   a second lens group with negative optical power; and   a subsequent lens group with positive optical power as a whole including at least three lens groups,   wherein during zooming operation,
 the first lens group moves along an optical axis, and 
 the second lens group does not move along the optical axis, and 
   wherein the second lens group has an aperture stop and satisfies condition (1) below,
   −9.0 ≦fG 1/ fG 2≦−2.0   (1)
 
   
       where
 fG 1  is a focal length of the first lens group, and 
 fG 2  is a focal length of the second lens group. 
 
     
     
         2 . The zoom lens system of  claim 1 , wherein the zoom lens system satisfies condition (2) below,
   0.4≦LG2 a /LG2≦0.9   (2)
   
       where
 LG 2   a  is a largest size of air spaces inside the second lens group, and 
 LG 2  is a thickness of the second lens group in a direction of the optical axis. 
 
     
     
         3 . The zoom lens system of  claim 1 , wherein some lens element of the second lens group move so as to have a component vertical to the optical axis in image blur correction. 
     
     
         4 . The zoom lens system of  claim 1 , wherein the first lens group is composed of three single lenses. 
     
     
         5 . The zoom lens system of  claim 1 , wherein the subsequent lens group is composed of:
 a third lens group with positive optical power;   a fourth lens group with negative optical power; and   a fifth lens group with negative optical power.   
     
     
         6 . The zoom lens system of  claim 1 , wherein the subsequent lens group is composed of:
 a third lens group with positive optical power;   a fourth lens group with positive optical power;   a fifth lens group with negative optical power; and   a sixth lens group with negative optical power.   
     
     
         7 . An imaging apparatus comprising:
 a zoom lens system that forms an optical image of an object; and   an imaging element that converts the optical image formed by the zoom lens system to an electrical image signal,   wherein the zoom lens system, in order from an object side to an image side, includes:   a first lens group with positive optical power;   a second lens group with negative optical power; and   a subsequent lens group with positive optical power as a whole including at least three lens groups, and   wherein, during zooming operation,   the first lens group moves along an optical axis, and   the second lens group does not move along the optical axis, and   wherein the second lens group has an aperture stop and satisfies condition (1) below,
   −9.0 ≦fG 1/ fG 2≦−2.0   (1)
 
   where   fG 1  is a focal length of the first lens group, and   fG 2  is a focal length of the second lens group.   
     
     
         8 . A camera comprising:
 a zoom lens system that forms an optical image of an object; and   an imaging element that converts the optical image formed by the zoom lens system to an electrical image signal,   wherein the zoom lens system, in order from an object side to an image side, includes:   a first lens group with positive optical power;   a second lens group with negative optical power; and   a subsequent lens group with positive optical power as a whole including; at least three lens groups, and   wherein, during zooming operation,   the first lens group moves along an optical axis, and   the second lens group does not move along the optical axis,   wherein the second lens group has an aperture stop and satisfies condition (1) below,
   −9.0 ≦fG 1/ fG 2≦−2.0   (1)
 
   where   fG 1  is a focal length of the first lens group, and   fG 2  is a focal length of the second lens group, and   wherein the camera performs at least one of displaying and storing the image signal converted by the imaging element.