Zoom lens for super 8 film

Abstract

A main lens unit having a fixed focal length and consisting of a positive lens member is preceded by an afocal forward lens unit having a variable magnification and consisting of a positive forward lens member, a negative intermediate lens member which is axially movable to change the magnification, and a positive rear lens member. The intermediate lens member is arranged to direct divergent bundles of rays to said rear lens member. The rear lens member is arranged to convert said divergent bundles or rays into bundles of rays which are substantially parallel to the optical axis of the lens and to direct them to said main lens unit. The forward lens member is axially movable to control the position of the image plane. The lens is designed to meet the condition f.sub.min -f.sub.11 < 6y where f min is the smallest focal length of the lens, f 11 the focal length of the intermediate lens member, and 2y the image field diagonal.

What is claimed is: 
     
       1. A zoom lens, which comprises a main lens unit having a fixed focal length and consisting of a positive lens member, and   an afocal forward lens unit preceding said main lens unit and having a variable magnification,   said forward lens unit consisting of a positive forward lens member, a negative intermediate lens member which is axially movable to change the magnification, and a positive rear lens member,   the positive forward lens member of the afocal part consists of a negative .[.meniscue.]. .Iadd.meniscus .Iaddend.lens element convex towards the front followed by two biconvex lens elements,   said negative intermediate lens member consists of a negative .[.meniscue.]. .Iadd.meniscus .Iaddend.convex toward the front followed by a negative doublet composed of a biconcave lens cemented to a positive lens element,   said positive rear lens member consists of a biconvex lens element,   said intermediate lens member being arranged to direct divergent bundles of rays to said rear lens member,   said rear lens member being arranged to convert said divergent bundles of rays into bundles of rays which are substantially parallel to the optical axis of the lens and to direct them to said rear lens member,   said forward lens member being axially movable to control the position of the image plane, and   said lens being designed to meet the condition   f.sub.min -f.sub.11 <6y       where f min  is the smallest focal length of the lens, f 11  the focal length of said intermediate lens member, and 2y the image field diagonal.   
     
     
       2. A zoom lens as set forth in claim 1, which lens elements define a performance number Z= 2yD/f min  of at least 1.9, where 2y is the image field diagonal, D the zoom ratio and f min  the smallest focal length of the lens. 
     
     
       3. A zoom lens which comprises a main lens unit having a fixed focal length and consisting of a positive lens member, and   an afocal forward lens unit preceding said main lens unit and having a variable magnification,   said forward lens unit consisting of a positive forward lens member, a negative intermediate lens member which is axially movable to change the magnification, and a positive rear lens member,   said intermediate lens member being arranged to direct divergent bundles of rays to said rear lens member,   said rear lens member being arranged to convert said divergent bundles of rays into bundles of rays which are substantially parallel to the optical axis of the lens and to direct them to said rear lens member,   said forward lens member being axially movable to control the position of the image plane,   said lens being designed to meet the condition   f.sub.min -f.sub.11 < 6y       where f min  is the smallest focal length of the lens, f 11  the focal length of said intermediate lens member, and 2y the image field diagonal,   said forward lens member consists of three lens elements,   said intermediate lens member consists of three lens elements,   said zoom lens having the following data:   ______________________________________                                    
r.sub.1 + 5.308                                                           
          d.sub.1 = 0.08                                                  
                      n.sub.d 1 = 1.805                                   
                                  .sub.d 1 = 25.4                         
r.sub.2 + 1.750                                                           
          d.sub.2 = 0.07                                                  
r.sub.3 + 2.104                                                           
          d.sub.3 = 0.28                                                  
                      n.sub.d 2 = 1.603                                   
                                  .sub.d 2 = 60.6                         
r.sub.4 - 25.054                                                          
          d.sub.4 = 0.01                                                  
r.sub.5 + 1.660                                                           
          d.sub.5 = 0.28                                                  
                      n.sub.d 3 = 1.658                                   
                                  .sub.d 3 = 50.9                         
r.sub.6 - 30.293                                                          
           f.sub.min f.sub.M f.sub.max                                    
r.sub.7 + 7.378                                                           
          d.sub.7 = 0.06                                                  
                      n.sub.d 4 = 1.658                                   
                                  .sub.d 4 = 50.9                         
r.sub.8 + 0.648                                                           
          d.sub.8 = 0.14                                                  
r.sub.9 - 1.310                                                           
          d.sub.9 = 0.06                                                  
                      n.sub.d 5 = 1.670                                   
                                  .sub.d 5 = 47.1                         
r.sub.10 + 0.800                                                          
          d.sub.10 = 0.14                                                 
                      n.sub.d 6 = 1.805                                   
                                  .sub.d 6 = 25.4                         
r.sub.11 + 23.022                                                         
           f.sub.min f.sub.M f.sub.max                                    
r.sub.12 + 1.767                                                          
          d.sub.12 = 0.10                                                 
                      n.sub.d 7 = 1.689                                   
                                  .sub.d 7 = 49.5                         
r.sub.13 - 17.389                                                         
          d.sub.13 = 0.50                                                 
r.sub.14 + 0.544                                                          
          d.sub.14 = 0.18                                                 
                      n.sub.d 8 = 1.713                                   
                                  .sub.d 8 = 53.8                         
r.sub.15 - 5.043                                                          
          d.sub.15 = 0.11                                                 
r.sub.16 - 0.985                                                          
          d.sub.16 = 0.20                                                 
                      n.sub.d 9 = 1.785                                   
                                  .sub.d 9  = 26.1                        
r.sub.17 + 0.474                                                          
          d.sub.17 = 0.20                                                 
r.sub.18 - 2.559                                                          
          d.sub.18 = 0.12                                                 
                      n.sub.d 10 = 1.641                                  
                                  .sub.d 10 = 60.1                        
r.sub.19 - 0.744                                                          
          d.sub.19 = 0.01                                                 
r.sub.20 + 0.690                                                          
          d.sub.20 = 0.17                                                 
                      n.sub.d 11 = 1.641                                  
                                  .sub.d 11 = 60.1                        
r.sub.21 - 4.020                                                          
          s' = 0.59                                                       
          f.sub.min = 0.575                                               
          f.sub.M = 1.018                                                 
          f.sub.max = 1.800                                               
          2y = 0.440                                                      
______________________________________                                    
       where r 1  to r 21  are .[.in millimeters.]. the radii of curvature of boundary surfaces of lens elements, d 1  to d 20  are .[.in millimeters.]. the distances between adjacent vertices of adjacent boundary surfaces of lens elements, n d .sbsb.1 to n d .sbsb.11 are the indices of refraction and v d .sbsb.1 to v d .sbsb.11 are the Abbe numbers of the lens elements, all in a succession from the forward end to the rear end of the lens, s' is the back focal length and 2y the image diagonal, and   which data unless otherwise stated are applicable to a setting for a mean focal length f M , which is the geometric mean of the shortest focal length f min  and the longest focal length f max  of the lens.   
     
     
       4. A zoom lens, which comprises a main lens unit having a fixed focal length and consisting of a positive lens member, and   an afocal forward lens unit preceding said main lens unit and having a variable magnification,   said forward lens unit consisting of a positive forward lens member, a negative intermediate lens member which is axially movable to change the magnification, and a positive rear lens member,   said intermediate lens member being arranged to direct divergent bundles of rays to said rear lens member,   said rear lens member being arranged to convert said divergent bundles of rays into bundles of rays which are substantially parallel to the optical axis of the lens and to direct them to said rear lens member,   said forward lens member being axially movable to control the position of the image plane,   said lens being designed to meet the condition   f.sub.min -f.sub. 11 < 6y     where f min  is the smallest focal length of the lens, f 11  the focal length of said intermediate lens member, and 2y the image field diagonal,     said forward lens member consists of three lens elements,   said intermediate lens member consists of three lens elements,   said zoom lens having the following data:   ______________________________________                                    
r.sub.1 + 4.661                                                           
          d.sub.1 = 0.07                                                  
                      n.sub.d 1 = 1.805                                   
                                  .sub.d 1 = 25.4                         
r.sub.2 + 1.423                                                           
          d.sub.2 = 0.05                                                  
r.sub.3 + 1.567                                                           
          d.sub.3 = 0.25                                                  
                      n.sub.d 2 = 1.604                                   
                                  .sub.d 2 = 53.6                         
r.sub.4 - 25.437                                                          
          d.sub.4 = 0.01                                                  
r.sub.5 + 1.427                                                           
          d.sub.5 = 0.25                                                  
                      n.sub.d 3 = 1.624                                   
                                  .sub.d 3 = 47.0                         
r.sub.6 - 25.437                                                          
           f.sub.min f.sub.M f.sub.max                                    
r.sub.7 + 64.139                                                          
          d.sub.7 = 0.06                                                  
                      n.sub.d 4 = 1.717                                   
                                  .sub.d 4 = 48.0                         
r.sub.8 + 0.646                                                           
          d.sub.8 = 0.14                                                  
r.sub.9 - 1.254                                                           
          d.sub.9 = 0.05                                                  
                      n.sub.d 5 = 1.622                                   
                                  .sub.d 5 = 53.2                         
r.sub.10 + 0.710                                                          
          d.sub.10 = 0.14                                                 
                      n.sub.d 6 = 1.755                                   
                                  .sub.d 6 = 27.6                         
r.sub.11 flat                                                             
           f.sub.min f.sub.M f.sub.max                                    
r.sub.12 + 1.967                                                          
          d.sub.12 = 0.10                                                 
                      n.sub.d 7 = 1.623                                   
                                  .sub.d 7 = 58.1                         
r.sub.13 - 4.076                                                          
          d.sub.13 = 0.50                                                 
r.sub.14 + 0.544                                                          
          d.sub.14 = 0.18                                                 
                      n.sub.d 8 = 1.713                                   
                                  .sub.d 8 = 53.8                         
r.sub.15 - 5.043                                                          
          d.sub.15 = 0.11                                                 
r.sub.16 - 0.985                                                          
          d.sub.16 = 0.20                                                 
                      n.sub.d 9 = 1.785                                   
                                  .sub.d 9 =  26.1                        
r.sub.17 + 0.474                                                          
          d.sub.17 = 0.20                                                 
r.sub.18 - 2.559                                                          
          d.sub.18 = 0.12                                                 
                      n.sub.d 10 = 1.641                                  
                                  .sub.d 10 = 60.1                        
r.sub.19 - 0.744                                                          
          d.sub.19 = 0.01                                                 
r.sub.20 + 0.690                                                          
          d.sub.20 = 0.17                                                 
                      n.sub.d 11 = 1.641                                  
                                  .sub.d 11 = 60.1                        
r.sub.21 - 4.020                                                          
          f.sub.min = 0.606                                               
          f.sub.M = 0.979                                                 
          f.sub.max = 1.581                                               
          2y = 0.440                                                      
______________________________________                                    
       where r 1  to r 21  are .[.in millimeters.]. the radii of curvature of boundary surfaces of lens elements, d 1  to d 20  are .[.in millimeters.]. the distances between adjacent vertices of adjacent boundary surfaces of lens elements, n d .sbsb.1 to n d .sbsb.11 are the indices of refraction and v d .sbsb.1 to v d .sbsb.11 are the Abbe numbers of the lens elements, all in a succession from the forward end to the rear end of the lens, s' is the back focal length and 2y the image diagonal, and   which data unless otherwise stated are applicable to a setting for a mean focal length f M , which is the geometric mean of the shortest focal length f min  and the longest focal length f max  of the lens.