Zoom lens and camera device

Abstract

The zoom lens comprises the foremost or first lens group of positive refractive power located the closest to an object, the succeeding second lens group of negative refractive power, and the third lens group of positive refractive power, all arranged in this order, and if any, the rearmost lens group(s) closer to the imaging plane than the third lens group, all or part of the lens group(s) of negative refractive power behind the third lens group being moved in directions normal to the optical axis to serve as an anti-vibration lens for shifting an image. The zoom lens meets requirements as defined in the formula regarding a displacement of the first lens group, a focal length of the zoom lens at the wide-angle end, a focal length of the zoom lens at the telephoto end, and a focal length of the first lens group.

1 . A zoom lens comprising three or more groups of lens pieces, the foremost or first lens group of positive refractive power located the closest to an object, the succeeding second lens group of negative refractive power, and the third lens group of positive refractive power, all arranged in this order, and if any, the rearmost lens group(s) closer to the imaging plane than the third lens group, all or part of the lens group(s) of negative refractive power behind the third lens group being moved in directions normal to the optical axis to serve as an anti-vibration lens for shifting an image; and the zoom lens meeting the requirements as defined in the following formula:
   0.11 ≦X 1 /fT≦ 0.28  (1)
     0.5 ≦f 1/√{square root over (( fw×fT ))}≦1.3  (2)
     0.20 ≦f 3/√{square root over (( fw×fT ))}≦0.45  (3)
   where X1 is a displacement of the first lens group when the zoom lens is extended from the wide-angle end to the telephoto end to vary optical power, fw is a focal length of the zoom lens at the wide-angle end, fT is a focal length of the zoom lens at the telephoto end, f1 is a focal length of the first lens group, and f3 is a focal length of the third lens group.   
     
     
         2 . A zoom lens comprising five or more groups of lens pieces, the foremost or first lens group of positive refractive power located the closest to an object, the succeeding second lens group of negative refractive power, the third lens group of positive refractive power, the fourth lens group, and the fifth lens group, all arranged in this order, all or part of the lens group(s) of negative refractive power behind the third lens group being moved in directions normal to the optical axis to serve as an anti-vibration lens for shifting an image; and the zoom lens meeting the requirements as defined in the following formula:
   0.11 ≦X 1 /fT≦ 0.28  (1)
     0.5 ≦f 1/√{square root over (( fw×fT ))}≦1.3  (2)
   where X1 is a displacement of the first lens group when the zoom lens is extended from the wide-angle end to the telephoto end to vary optical power, fw is a focal length of the zoom lens at the wide-angle end, fT is a focal length of the zoom lens at the telephoto end, and f1 is a focal length of the first lens group.   
     
     
         3 . The zoom lens according to  claim 2 , wherein the zoom lens meets the requirements as defined about the third lens group in the following formula (3):
   0.20 ≦f 3/√{square root over (( fw×fT ))}≦0.45  (3)
   where f3 is a focal length of the third lens group.   
     
     
         4 . The zoom lens according to  claim 1 , wherein the zoom lens comprises a lens group(s) of positive refractive power and/or a component lens piece(s) of positive refractive power located closer to the object than all or part of the lens group(s) of negative refractive power moved to serve as an anti-vibration lens for shifting an image. 
     
     
         5 . The zoom lens according to  claim 1 , wherein the zoom lens has one or more lens pieces of positive and negative refractive power in all or part of the lens group(s) of negative refractive power moved to serve as an anti-vibration lens for shifting an image. 
     
     
         6 . The zoom lens according to  claim 1 , wherein part or all of the lens group(s) moved to serve as an anti-vibration lens for shifting an image meet the requirements as defined in the following formula (4):
   −2.8≦(1 −βa )×β b≦− 1.0  (4)
   where βa is an optical power of the lens group(s) movable in directions normal to the optical axis when the zoom lens is taking a posture of the telephoto end, and βb is a synthetic optical power of a lens group(s) closer to the imaging plane than the lens group(s) movable in directions normal to the optical axis.   
     
     
         7 . The zoom lens according to  claim 1 , wherein the zoom lens meets the requirements as defined in the following formula (5):
   0.60 ≦Lt/fT≦ 0.75  (5)
   where Lt is an entire length of the optical system of the zoom lens at the telephoto end, and fT is a focal length of the zoom lens at the telephoto end.   
     
     
         8 . The zoom lens according to  claim 1 , wherein the zoom lens has two or more lens groups located behind the third lens group and moved to vary optical power. 
     
     
         9 . A camera device comprising image sensors disposed on or behind the imaging plane of the zoom lenses according to  claim 1 , for converting an optical image created by the zoom lens into electrical signals. 
     
     
         10 . The zoom lens according to  claim 2 , wherein the zoom lens comprises a lens group(s) of positive refractive power and/or a component lens piece(s) of positive refractive power located closer to the object than all or part of the lens group(s) of negative refractive power moved to serve as an anti-vibration lens for shifting an image. 
     
     
         11 . The zoom lens according to  claim 2 , wherein the zoom lens has one or more lens pieces of positive and negative refractive power in all or part of the lens group(s) of negative refractive power moved to serve as an anti-vibration lens for shifting an image. 
     
     
         12 . The zoom lens according to  claim 2 , wherein part or all of the lens group(s) moved to serve as an anti-vibration lens for shifting an image meet the requirements as defined in the following formula (4):
   −2.8≦(1 −βa )×β b≦− 1.0  (4)
   
       where βa is an optical power of the lens group(s) movable in directions normal to the optical axis when the zoom lens is taking a posture of the telephoto end, and βb is a synthetic optical power of a lens group(s) closer to the imaging plane than the lens group(s) movable in directions normal to the optical axis. 
     
     
         13 . The zoom lens according to  claim 2 , wherein the zoom lens meets the requirements as defined in the following formula (5):
   0.60 ≦Lt/fT≦ 0.75  (5)
   where Lt is an entire length of the optical system of the zoom lens at the telephoto end, and fT is a focal length of the zoom lens at the telephoto end.   
     
     
         14 . The zoom lens according to  claim 2 , wherein the zoom lens has two or more lens groups located behind the third lens group and moved to vary optical power. 
     
     
         15 . A camera device comprising image sensors disposed on or behind the imaging plane of the zoom lenses according to  claim 2 , for converting an optical image created by the zoom lens into electrical signals.