Vibration reduction zoom lens system

Abstract

An object is to provide a vibration reduction (VR) zoom lens system having high optical performance and compactness suitable for an SLR camera, a video camera and the like. The zoom lens system includes, in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, a fourth lens group having negative refractive power, and a fifth lens group having positive refractive power. All distances between adjacent lens groups are moved upon zooming from a wide-angle end state to a telephoto end state. The third lens group includes a plurality of lenses including a cemented lens constructed by a negative lens cemented with a positive lens. Only the cemented lens is used as a vibration reduction lens shifting substantially perpendicularly to the optical axis for correcting camera shake. Given conditional expressions are satisfied.

What is claimed is:  
     
         1 . A vibration reduction zoom lens system comprising, in order from an object; 
 a first lens group having positive refractive power;    a second lens group having negative refractive power;    a third lens group having positive refractive power;    a fourth lens group having negative refractive power; and    a fifth lens group having positive refractive power;    all distances between adjacent lens groups being moved upon zooming from a wide-angle end state to a telephoto end state;    the third lens group comprising a plurality of lenses including a cemented lens constructed by a negative lens and a positive lens;    only the cemented lens being used as a vibration reduction lens shifting substantially perpendicularly to the optical axis for correcting camera shake; and    the following conditional expression being satisfied:   0.6 <|f   3   A|/|f   3 |<2.6   where f 3 A denotes the focal length of the vibration reduction lens of the third lens group, and f 3  denotes the focal length of the third lens group.    
     
     
         2 . The vibration reduction zoom lens system according to  claim 1 , wherein the following conditional expression is satisfied: 
       0.10 <|N   3   AN−N   3   AP|   
       where N 3 An denotes a refractive index of a medium of the negative lens of the vibration reduction lens at d-line (λ=587.6 nm), and N 3 AP denotes a refractive index of a medium of the positive lens of the vibration reduction lens at d-line (λ=587.6 nm).  
     
     
         3 . The vibration reduction zoom lens system according to  claim 2 , wherein the following conditional expression is satisfied: 
       −0.50<( R   2 + R   1 )/( R   2 − R   1 )<0.50 
       where R 1  denotes a radius of curvature of the most object side lens surface of the vibration reduction lens, and R 2  denotes a radius of curvature of the most image side lens surface of the vibration reduction lens.  
     
     
         4 . The vibration reduction zoom lens system according to  claim 3 , wherein the following conditional expression is satisfied: 
       3.0 <FT·f   1 / fT <5.5 
       where fT denotes the focal length of the vibration reduction zoom lens system in the telephoto end state, f 1  denotes the focal length of the first lens group, and FT denotes the f-number of the vibration reduction zoom lens system in the telephoto end state.  
     
     
         5 . The vibration reduction zoom lens system according to  claim 4 , wherein the following conditional expression is satisfied: 
       0.40 <|f   2 |/ fW <0.80 
       where fW denotes the focal length of the vibration reduction zoom lens system in the wide-angle end state, and f 2  denotes the focal length of the second lens group.  
     
     
         6 . The vibration reduction zoom lens system according to  claim 3 , wherein the following conditional expression is satisfied: 
       0.40 <|f   2 |/ fW <0.80 
       where fW denotes the focal length of the vibration reduction zoom lens system in the wide-angle end state, and f 2  denotes the focal length of the second lens group.  
     
     
         7 . The vibration reduction zoom lens system according to  claim 2 , wherein the following conditional expression is satisfied: 
       3.0 <FT·f   1 / fT <5.5 
       where fT denotes the focal length of the vibration reduction zoom lens system in the telephoto end state, f 1  denotes the focal length of the first lens group, and FT denotes the f-number of the vibration reduction zoom lens system in the telephoto end state.  
     
     
         8 . The vibration reduction zoom lens system according to  claim 7 , wherein the following conditional expression is satisfied: 
       0.40 <|f   2 |/ fW <0.80 
       where fW denotes the focal length of the vibration reduction zoom lens system in the wide-angle end state, and f 2  denotes the focal length of the second lens group.  
     
     
         9 . The vibration reduction zoom lens system according to  claim 2 , wherein the following conditional expression is satisfied: 
       0.40 <|f   2 |/ fW <0.80 
       where fW denotes the focal length of the vibration reduction zoom lens system in the wide-angle end state, and f 2  denotes the focal length of the second lens group.  
     
     
         10 . The vibration reduction zoom lens system according to  claim 1 , wherein the following conditional expression is satisfied: 
       −0.50<( R   2 + R   1 )/( R   2 − R   1 )<0.50 
       where R 1  denotes a radius of curvature of the most object side lens surface of the vibration reduction lens, and R 2  denotes a radius of curvature of the most image side lens surface of the vibration reduction lens.  
     
     
         11 . The vibration reduction zoom lens system according to  claim 10 , wherein the following conditional expression is satisfied: 
       3.0 <FT·f   1 / fT <5.5 
       where fT denotes the focal length of the vibration reduction zoom lens system in the telephoto end state, f 1  denotes the focal length of the first lens group, and FT denotes the f-number of the vibration reduction zoom lens system in the telephoto end state.  
     
     
         12 . The vibration reduction zoom lens system according to  claim 11 , wherein the following conditional expression is satisfied: 
       0.40 <|f   2 |/ fW <0.80 
       where fW denotes the focal length of the vibration reduction zoom lens system in the wide-angle end state, and f 2  denotes the focal length of the second lens group.  
     
     
         13 . The vibration reduction zoom lens system according to  claim 10 , wherein the following conditional expression is satisfied: 
       0.40 <|f   2 |/ fW <0.80 
       where fW denotes the focal length of the vibration reduction zoom lens system in the wide-angle end state, and f 2  denotes the focal length of the second lens group.  
     
     
         14 . The vibration reduction zoom lens system according to  claim 1 , wherein the following conditional expression is satisfied: 
       3.0 <FT·f   1 / fT <5.5 
       where fT denotes the focal length of the vibration reduction zoom lens system in the telephoto end state, f 1  denotes the focal length of the first lens group, and FT denotes the f-number of the vibration reduction zoom lens system in the telephoto end state.  
     
     
         15 . The vibration reduction zoom lens system according to  claim 14 , wherein the following conditional expression is satisfied: 
       0.40 <|f   2 |/ fW <0.80 
       where fW denotes the focal length of the vibration reduction zoom lens system in the wide-angle end state, and f 2  denotes the focal length of the second lens group.  
     
     
         16 . The vibration reduction zoom lens system according to  claim 1 , wherein the following conditional expression is satisfied: 
       0.40 <f   2 |/ fW <0.80 
       where fW denotes the focal length of the vibration reduction zoom lens system in the wide-angle end state, and f 2  denotes the focal length of the second lens group.