Method and apparatus for transmission of information in a photographic camera

Abstract

A photographic camera has a camera body, an interchangeable lens assembly mounted on the camera body, and an automatic exposure control mechanism located in the camera body. The mechanism responds to a first binary signal representative of a maximum lens aperture value in binary code and a second binary signal representative of a minimum lens aperture value in binary code. The first signal has a given number of binary bits. The second signal is generated in the lens assembly. A third signal representative of the arithmetic difference between the first and second signals is also generated in the lens assembly. The third signal has a number of binary bits fewer than the given number. The second and third signals generated in the lens assembly are transmitted to the camera body. In the camera body, the second signal is applied to the mechanism and the transmitted second and third signals are arithmetically added to derive the first signal, which is applied to the mechanism.

What is claimed is: 
     
       1. In a photographic camera having a camera body, an interchangeable lens assembly mounted on the camera body, and an automatic exposure control mechanism located in the camera body, the mechanism responding to a first binary signal representative of a maximum lens aperture value in binary code and a second binary signal representative of a minimum lens aperture value in binary code, the first signal having a given number of binary bits, a method comprising the steps of: generating in the lens assembly a second signal representative of the minimum aperture value for the lens assembly;   generating in the lens assembly a third signal representative of the arithmetic difference between the first and second signals for the lens assembly, the third signal having a number of binary bits fewer than the given number;   transmitting the second and third signals generated in the lens assembly to the camera body;   applying the second signal to the mechanism;   arithmetically adding the transmitted second and third signals to derive the first signal for the lens assembly; and   applying the derived first signal to the mechanism.   
     
     
       2. In a photographic camera having an interchangeable lens mounted on the camera body, the combination comprising: a source of a first signal in binary code located in the lens assembly, the first signal having a given number of binary information bits;   a source of a second signal in binary code located in the lens assembly;   means for transmitting the first and second signals from the source in the lens assembly to the camera body;   means for arithmetically adding the first and second signals in the camera body to derive a third signal in binary code having a number of binary information bits one more than the given number; and   means partially responsive to the third signal for automatically controlling light exposure.   
     
     
       3. The combination of claim 2, in which the controlling means is responsive to the transmitted second signal and the derived third signal. .Iadd. 
     
     
       4.  An interchangeable lens for a photographic camera using lenses interchangeably, the lens having means for transmitting information representative of a maximum lens aperture value from the lens to the camera body and means for transmitting and information representative of a minimum lens aperture value from the lens to the camera body, wherein a signal representative of the maximum lens aperture value is generated as the signal representative of a difference between a signal representative of the actual maximum lens aperture and a signal representative of the actual minimum lens aperture of the lens. .Iaddend. .Iadd.5. In an interchangeable lens having a minimum aperture in F-value of 22 or 32, a maxinum aperture in F-value of 1.2, 1.4, 1.7, 2, 2.5, 2.8, 3.5, or 4 if the minimum aperture in F-value is 22, and a maximum aperture in F-value of 1.7, 2, 2.5, 2.8, 3.5, 4, 4.5, or 5.6 if the minimum aperture in F-value is 32, means for generating at least one bit of binary information representative of the minimum aperture of the lens and means for generating a three-bit maximum aperture signal, a 2 , a 1 , a 0 , of binary information representative of the maximum aperture of the lens, the correspondence between the maximum aperture signal and the maximum aperture in F-value being in accordance with the following table when the minimum F-value is 22   ______________________________________                                    
Maximum aperture                                                          
            Actual maximum                                                
signal      signal        Maximum aperture                                
a.sub.2                                                                   
     a.sub.1 a.sub.0                                                      
                    C.sub.3                                               
                         C.sub.2                                          
                             C.sub.1                                      
                                  C.sub.0                                 
                                      in F-value                          
______________________________________                                    
0    0       0      0    0   0    0   1.2                                 
0    0       1      0    0   0    1   1.4                                 
0    1       0      0    0   1    0   1.7                                 
0    1       1      0    0   1    1   2                                   
1    0       0      0    1   0    0   2.5                                 
1    0       1      0    1   0    1   2.8                                 
1    1       0      0    1   1    0   3.5                                 
1    1       1      0    1   1    1   4                                   
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     and the correspondence between the maximum aperture signal and the maximum aperture in F-value being in accordance with the following table when the minimum F-value is 32     ______________________________________                                    
Maximum aperture                                                          
            Actual maximum                                                
signal      signal        Maximum aperture                                
a.sub.2                                                                   
     a.sub.1 a.sub.0                                                      
                    C.sub.3                                               
                         C.sub.2                                          
                             C.sub.1                                      
                                  C.sub.0                                 
                                      in F-value                          
______________________________________                                    
0    0       0      0    0   1    0   1.7                                 
0    0       1      0    0   1    1   2                                   
0    1       0      0    1   0    0   2.5                                 
0    1       1      0    1   0    1   2.8                                 
1    0       0      0    1   1    0   3.5                                 
1    0       1      0    1   1    1   4                                   
1    1       0      1    0   0    0   4.5                                 
1    1       1      1    0   0    1   5.6                                 
______________________________________                                    
     
     
     
        .Iaddend. 6.  In an interchangeable lens having one of a plurality of minimum F-.Iadd.values no more than 2 m , a plurality of maximum F-values no more than 2 n , where the choice of maximum F-values is partially different for each minimum F-value, the improvement comprising first means for generating an m bit binary signal representative of a minimum F-value and second means for generating an n-1 bit binary signal representative of a maximum F-value. .Iaddend. .Iadd.7. The interchangeable lens of claim 6, in which m=1, n=4, the first generating means generates one bit and the second generating means generates three bits. .Iaddend. .Iadd.8. The interchangeable lens of claim 6, in which m=2 and n=4, the first generating means generates two bits and the second generating means generates three bits. .Iaddend. .Iadd.9. A family of interchangeable lens assemblies adapted for mounting on a camera body, the lens assemblies having a minimum aperture value and a maximum aperture value, there being among the lens assemblies a total of no more than 2 n  different maximum aperture values and a total of no more than 2 m  different minimum aperture values, the maximum aperture values being assigned in increasing order n bit binary numbers according to natural binary code, the minimum aperture values being assigned in increasing order m bit binary numbers according to natural binary code, each lens assembly comprising means for generating an m bit minimum aperture binary signal representative of the binary number assigned to the minimum aperture value of such lens and means for generating an n-1 bit maximum aperture binary signal representative of the binary number assigned to the maximum aperture value of such lens assembly minus the binary number assigned to the minimum aperture value of such lens 
     
     
        assembly. .Iaddend. .Iadd.10.  The family of lens assemblies of claim 9, in which n=4 and m=1. .Iaddend. .Iadd.11. The family of lens assemblies of claim 9, in which n=4 and m=2. .Iaddend. .Iadd.12. A lens assembly, which is one of a family of interchangeable lens assemblies adapted for mounting on a camera body, the lens assemblies each having a minimum aperture value and a maximum aperture value, there being among the lens assemblies a total of no more than 2 n  different maximum aperture values and a total of no more than 2 m  different minimum aperture values, the maximum aperture values being assigned in increasing order n-bit binary numbers according to natural binary code, the minimum aperture values being assigned in increasing order m-bit binary numbers according to natural binary code, the lens assembly comprising means for generating an m bit minimum aperture binary signal representative of the binary number assigned to the minimum aperture value of such lens assembly and means for generating an n-1 bit maximum aperture binary signal representative of a binary number equal to the binary number assigned to the maximum aperture value of such lens assembly minus the binary number assigned to the minimum aperture value of such lens assembly. .Iaddend.