Abstract:
A camera system comprising a camera body and an interchangeable lens detachably set to the camera body, includes a distance measuring part configured to measure a focusing error of the interchangeable lens through detecting a flux of light passed through the interchangeable lens, an intermediate adapter arranged for detachably being set between the camera body and the interchangeable lens, a data storing part configured to store first data and second data, a reading part configured to read the first data and the second data from the data storing part, and a correcting part configured to correct the detection result of focusing error received from the distance measuring part by using the first data when the intermediate adapter is not set, and correct the detection result of focusing error received from the distance measuring part by using the second data when the intermediate adapter is set.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This is a Continuation Application of PCT Application No. PCT/JP2004/011094, filed Aug. 3, 2004, which was published under PCT Article 21(2) in Japanese.  
         [0002]     This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2003-292267, filed Aug. 12, 2003, the entire contents of which are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0003]     1. Field of the Invention  
         [0004]     The present invention relates to a technology of correcting the AF action of a camera in response to a degree of spherical aberration of a camera lens, and particularly to a camera equipped with an AF sensing unit, an interchangeable lens, an intermediate adapter, and a camera system including the same.  
         [0005]     2. Description of the Related Art  
         [0006]     It happens that a camera equipped with a TTL phase difference type AF sensing unit yields out-of-focus images when shooting at full open aperture in spite of the lens being adjustably focused on the basis of focusing data detected by the AF sensing unit. This results from a difference in the spherical aberration of the camera lens between a F-number of full-open aperture and a F-number of AF sensing aperture for measuring the focal point, which thus dislocates the best imaging plane.  
         [0007]     Disclosed in Jpn. Pat. Appln. KOKAI Publication No. 59-208514 is a technique of correcting the output of the AF sensing unit with displacement correcting data of the best imaging plane (referred to as “AF correcting data” hereinafter) which has been decided from a difference in the spherical aberration between two F-numbers and stored in the camera lens.  
         [0008]     A lens interchangeable camera has an intermediate adapter provided between the camera and the interchangeable lens for modifying the focal length. The intermediate adapter may be known as a telescopic converter for lengthening the focal length. When mounted on the camera, the spherical aberration of the intermediate adapter as well as the spherical aberration of the camera lens has to be concerned for affecting the focal length.  
         [0009]     Disclosed in Jpn. Pat. Appln. KOKAI Publication No. 4-93824 is a technique of correcting the output of the AF sensing unit through using a combination of the two AF correcting data stored in the interchangeable lens and the intermediate adapter respectively.  
       BRIEF SUMMARY OF THE INVENTION  
       [0010]     A camera system according to an aspect of the present invention includes: a distance measuring part configured to measure a focusing error of the interchangeable lens through detecting a flux of light passed through the interchangeable lens; a first intermediate adapter and a second intermediate adapter arranged for detachably being set between the camera body and the interchangeable lens; a first storing part configured to store first data decided by the optical characteristics of the interchangeable lens and second data decided by the optical characteristics of a combination of the interchangeable lens and the first intermediate adapter; a second storing part configured to store third data to correct the second data; and a correcting part configured to correct the output received from the distance measuring part by using the first data when neither the first nor second intermediate adapters is set, correct the output received from the distance measuring part by using the second data when the first intermediate adapter is set, and correct the output received from the distance measuring part by using both the second and third data when the second intermediate adapter is set. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       [0011]      FIG. 1  is a block diagram showing an arrangement of a camera system.  
         [0012]      FIG. 2  is a view showing a first variation of the camera system according to the invention.  
         [0013]      FIG. 3  is a view showing a second variation of the camera system according to the invention.  
         [0014]      FIG. 4  is a view showing a third variation of the camera system according to the invention.  
         [0015]      FIG. 5  is a flowchart schematically showing a procedure of the camera CPU receiving the lens information.  
         [0016]      FIG. 6  is a flowchart schematically showing a procedure of the camera CPU calculating a focusing error correcting data for correct focusing. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0017]      FIG. 1  is a block diagram showing a typical arrangement of a camera system.  
         [0018]     The camera system consists mainly of an interchangeable lens  10 , an intermediate adapter  20 , and a camera body unit  30 . The interchangeable lens  10 , the intermediate adapter  20 , and the camera body unit  30  are detachably joined together by mounting fittings (not shown).  
         [0019]     The interchangeable lens  10  includes camera lenses  11   a  and  11   b , a diaphragm  12 , a lens driving mechanism  13 , a diaphragm driving mechanism  14 , a lens CPU  15 , and a data storage unit  16 .  
         [0020]     The lens CPU  15  is provided for exclusively controlling the action of the interchangeable lens  10 . More particularly, its control signal is received by the lens driving mechanism  13  which in turn drives the camera lenses  11   a  and  11   b  forward and backward for focusing. The control signal is also received by the diaphragm driving mechanism  14  which in turn drives the diaphragm  12  for exposure control. Moreover, the lens CPU  15  exchanges signals of various information with the camera body unit  30 .  
         [0021]     The data storage unit  16  is provided for storage of specific information about the lens unit.  
         [0022]     The intermediate adapter  20  includes a telescopic lens  21 , an adapter CPU  22 , and an adapter storage unit  23 .  
         [0023]     The telescopic lens  21  is provided for varying the focal length of the interchangeable lens  10 . The magnification of the lens can thus be increased, for example, two times by the movement of the telescopic lens  21 .  
         [0024]     The adapter storage unit  23  is provided for storage of specific information about the intermediate adapter (for example, the type of lens or the AF correcting data). The adapter CPU  22  is provided for exchanging signals with the camera body unit  30  to transmit specific information about the intermediate adapter for AF correcting action.  
         [0025]     The camera body unit  30  consists mainly of a quick return mirror  32 , a shutter  33 , an imaging device  34 , an image processing circuit  35 , a camera CPU  36 , an image monitor  37 , an image memory  38 , a camera storage unit  40 , a pentagonal prism  41 , a light measuring circuit  42 , an AF lens  43 , a sub mirror  44 , an AF sensor  45 , a distance meter  46 , a shutter driving mechanism  47 , and a mirror driving mechanism  48 .  
         [0026]     The quick return mirror  32  has a half mirror provided at the center thereof for transmitting an optical image of the object to the pentagonal prism  41  and the AF sensor  45  in a non-shooting mode. The imaging device  34  converts the optical image of the object into an electric signal of image data using, for example, CCD. The camera CPU  36  is provided for exclusively controlling the action of the camera system and subjecting the image data to a variety of processing actions by controlling the image processing circuit  35 . A group of data required for operating the camera CPU  36  is stored in the camera storage unit  40 .  
         [0027]     The camera CPU  36  also communicates with the lens CPU  15  in the interchangeable lens  10  and the adapter CPU  22  in the intermediate adapter  20  for receiving the characteristic information of the camera lenses  11   a  and  11   b  and the AF correcting information respectively.  
         [0028]     There are provided four signal lines ASEL, LSEL, DATA, and CONT for exchanging the information. The signal line ASEL is provided for selectively supplying the intermediate adapter  20  with its desired information. The signal line LSEL is provided for selectively supplying the interchangeable lens  10  with its desired information. The signal line DATA is a common line for supplying the CPUs with the lens characteristic information. The signal line CONT is provided for supplying the CPUs with control signals (for example, a demand for lens information or a command for diaphragm driving) from the camera CPU.  
         [0029]     The image monitor  37  may be a liquid crystal display monitor or the like and is provided for displaying an image data. The image memory  38  is provided in the form of a recording medium, such as Smart Media (registered trademark), in which the image data is recorded.  
         [0030]     The light measuring circuit  42  is provided for receiving with its optoelectric converter element (not shown) a reflection of the optical image from the pentagonal prism  41  to measure the brightness of the object to be imaged. The camera CPU  36  calculates exposure conditions from the measurement of the brightness. The AF sensor  45  is provided for receiving the optical image of the object divided in two by the sub mirror  44  and passed through the AF lens  43 . The distance meter  46  is provided for calculating from an output of the AF sensor  45  the movement of the lens for correct focusing. The AF distance meter is of so-called TTL phase difference type in which the flux of light used for measuring the focal point is equivalent to the one with the camera lens aperture stopped down to F8.  
         [0031]     Then, the action of the camera system will be described.  
         [0032]     The action starts with a photographer pressing down the release button (not shown) on the camera body unit  30  to its first position. The camera CPU  36  then calculates the aperture value for an appropriate exposure from brightness of a object to be shot measured by the light measuring circuit  42 , and the result is received by the lens CPU  15 . The lens CPU  15  provides the diaphragm driving mechanism  14  with its output signal for obtaining a desired size of the aperture.  
         [0033]     Also, the camera CPU  36  calculates from the measurement of the distance meter  46 , the lens information from the interchangeable lens  10 , and the lens information from the intermediate adapter  20  the movement of the camera lenses  11   a  and  11   b  which is then received by the lens CPU  15  for correct focusing. In response to the movement data, the lens CPU  15  provides the lens driving mechanism  13  with a control signal for moving the camera lenses  11   a  and  11   b  to their correct focusing positions.  
         [0034]     When the photographer presses down the release button (not shown) on the camera body unit  30  to its second position, the camera CPU  36  retracts the quick return mirror  32  from the optical path of the camera and actuates the shutter  33  for directing the optical image of the object to the imaging device  34  and subjects the image data output of the imaging device  34  to relevant image processing actions. The image processing actions of the camera CPU  36  including color correction are carried out based on the lens information from the interchangeable lens  10  and the lens information from the intermediate adapter  20 .  
         [0035]     The camera system of the present invention including the interchangeable lens  10 , the intermediate adapter  20 , and the camera body unit  30  shown in  FIG. 1  is arranged operable in three different variations described below.  
         [0036]      FIG. 2  illustrates the first variation of the camera system of the present invention. The first variation of the camera system employs the interchangeable lens  10  and the camera body unit  30 .  
         [0037]     In the data storage unit  16 , the AF correcting data is saved as a combination of a first AF correcting data  16   a  (ΔAFD 0 ) without the intermediate adapter  20  and a second AF correcting data  16   b  (ΔAFD 1 ) with the intermediate adapter  20 .  
         [0038]     Accordingly, as the camera CPU  36  corrects the measurement of focusing error (AFD) of the distance meter  46  calculated by TTL phase difference technique with the AF correcting data, the movement amount of the camera lens for correct focusing is transmitted to the lens CPU  15 .  
         [0039]      FIG. 3  illustrates the second variation of the camera system of the present invention. The second variation of the camera system employs the interchange-able lens  10 , a type A intermediate adapter  20  (a first intermediate adapter)  20   a , and the camera body unit  30 . The type A intermediate adapter  20   a  means an initial version of the intermediate adapter.  
         [0040]     In the data storage unit  16 , the AF correcting data is saved as a combination of an AF correcting data  16   a  (ΔAFD 0 ) without the intermediate adapter  20  and an AF correcting data  16   b  (ΔAFD 1 ) with the type A intermediate adapter  20   a . The type A intermediate adapter  20   a  includes an adapter CPU  22   a  and an adapter storage unit  23   a . The adapter storage unit  23   a  holds a specific information about the intermediate adapter  20   a  but not the AF correcting data.  
         [0041]     Accordingly, as the camera CPU  36  corrects the measurement of focusing error (AFD) of the distance meter  46  calculated by TTL phase difference technique with the AF correcting data, the movement amount of the camera lens for correct focusing is transmitted to the lens CPU  15 .  
         [0042]      FIG. 4  illustrates a third variation of the camera system of the present invention. The third variation of the camera system employs the interchangeable lens  10 , a type B intermediate adapter (a second intermediate adapter)  20   b , and the camera body unit  30 . The type B intermediate adapter  20   b  means an improved version of the type A intermediate adapter  20   a.    
         [0043]     In the data storage unit  16 , the AF correcting data is saved as a combination of an AF correcting data  16   a  (ΔAFD 0 ) without the intermediate adapter  20  and an AF correcting data  16   b  (ΔAFD 1 ) with the type A intermediate adapter  20   a . The type B intermediate adapter  20   b  includes an adapter CPU  22   b  and an adapter storage unit  23   b . The adapter storage unit  23   b  holds a correction factor α or third data used for converting the AF correction data for the type A intermediate adapter  20   a  into an AF correction data for the type B intermediate adapter  20   b.    
         [0044]     Accordingly, as the camera CPU  36  corrects the measurement of focusing error (AFD) of the distance meter  46  calculated by TTL phase difference technique with the AF correcting data, the movement amount of the camera lens for correct focusing is transmitted to the lens CPU  15 .  
         [0045]     The action of the camera system for AF correction has mainly two steps: 
    (1) the camera CPU  36  in the camera body unit  30  receiving the lens information from both the inter-changeable lens  10  and the intermediate adapter  20 ; and     (2) the camera CPU  36  in the camera body unit  30  calculating the movement of the lenses for correct focusing.    
 
         [0048]     The two steps will now be described in more detail. The camera CPU  36  is designed for functioning with the three different variations of the camera system.  
         [0049]      FIG. 5  is a flowchart schematically showing a procedure of the camera CPU  36  receiving the lens information. The procedure starts when the camera body unit  30  is switched on or set to the interchangeable lens  10  and the intermediate adapter  20 .  
         [0050]     In step S 01 , the camera CPU  36  dispatches a lens select signal for receiving the lens information from the interchangeable lens  10 . More particularly, the signal line LSEL is turned from a low level to a high level. It is then examined in step S 02  whether or not a response is received from the interchangeable lens  10 . When the signal line is conducted, the lens CPU  15  releases a response signal indicating that the interchangeable lens  10  is ready for starting the communication.  
         [0051]     When it is determined “no” in step S 02 , i.e., no response is received from the interchangeable lens  10 , the camera CPU  36  ends the action.  
         [0052]     When it is determined “yes” in step S 02 , i.e., a response is received from the interchangeable lens  10 , the action advances to Step S 03  where the camera CPU  36  demands to receive the lens information. More specifically, the signal line CONT is conducted for transmitting a lens information demand signal. Upon receiving the demand signal, the lens CPU  15  retrieves the lens information from the data storage unit  16  and transmits the same to the camera CPU.  
         [0053]     The lens information to be transmitted may include the type of lens, the F-number at full opening, and the AF correcting data (ΔAFD 0  and ΔAFD 1 ). In step S 04 , the lens information is received by the camera CPU  36  and saved in the camera storage unit  40 .  
         [0054]     This is followed by Step S 05  where an adapter select signal for receiving the adapter information from the intermediate adapter  20  is dispatched from the camera CPU  36 . More particularly, the signal line ASEL is turned from a low level to a high level. It is examined in step S 06  whether or not a response is received from the intermediate adapter  20 . When the signal line is conducted, the adapter CPU  22  releases a response signal indicating that the intermediate adapter  20  is ready for starting the communication.  
         [0055]     When it is determined “no” in step S 06 , i.e., no response is received from the intermediate adapter  20 , the camera CPU  36  ends the action of the camera system having an arrangement shown in  FIG. 2 .  
         [0056]     When it is determined “yes” in step S 06 , i.e., a response is received from the intermediate adapter  20 , the action advances to Step S 07  where the camera CPU  36  checks the response to identify the type of the intermediate adapter. In other words, the camera CPU  36  examines whether or not the intermediate adapter is of the type B.  
         [0057]     When it is determined “no” in step S 08 , i.e., the intermediate adapter is of not the type B but the type A such as shown in  FIG. 3 , the camera CPU  36  ends the action as having received the lens correction data (ΔAFD 1 ).  
         [0058]     When it is determined “yes” in step S 08 , i.e., the intermediate adapter is of the type B such as shown in  FIG. 4 , the camera CPU  36  demands to receive the adapter information. More specifically, the signal line CONT is conducted for transmitting an adapter data demand signal. Upon receiving the demand signal, the adapter CPU  22   b  retrieves the adapter information from the adapter storage unit  23   b  and transmits the same to the camera CPU  36 .  
         [0059]     The adapter data may to be transmitted include the correction factor α. In step S 09 , the adapter data is received by the camera CPU  36  and saved in the camera storage unit  40 .  
         [0060]     Through conducting the above described procedure, the camera CPU  36  can receive and save the AF correct-ing data corresponding to each variation of the camera system arrangement in the camera storage unit  40 .  
         [0061]      FIG. 6  is a flowchart schematically showing a procedure of the camera CPU  36  calculating the focusing error for correct focusing. The procedure involves steps of the AF controlling action initiated prior to shooting action by the photographer pressing down the release button (not shown) on the camera body unit  30 .  
         [0062]     In step S 11 , the camera CPU  36  dispatches a command for starting the action of the AF sensor  45 . In step S 12 , a measurement of focusing error (the number of pitches across the sensor surface) is received from the AF sensor  45 . In step S 13 , the distance meter  46  calculates the focusing error (AFD) of the camera lenses  11   a  and  11   b  from the measurement of the number of pitches.  
         [0063]     This is followed by step S 14  where the camera CPU  36  examines whether the intermediate adapter  20  is set or not.  
         [0064]     When it is determined “no” in step S 14 , i.e., the intermediate adapter  20  is not set in the camera system shown in  FIG. 2 , the procedure goes to step S 15  where the camera CPU  36  adds the measurement of focusing error (AFD) from the distance meter  46  with the AF correcting data (ΔAFD 0 )  16   a  to obtain a focusing error (AFD′) at no presence of the intermediate adapter  20 .  
         [0065]     When it is determined “yes” in step S 14 , i.e., the intermediate adapter  20  is set, the procedure goes to Step S 16  where the camera CPU  36  retrieves the AF correcting data (ΔAFD 1 )  16   b  at the presence of the intermediate adapter  20  from the camera storage unit  40 .  
         [0066]     In step S 17 , the camera CPU  36  accesses the camera storage unit  40  and examines whether the intermediate adapter is of the type B or not.  
         [0067]     When it is determined “no” in step S 17 , i.e., the intermediate adapter is of not the type B but the type A and the camera system is as shown in  FIG. 3  where the camera CPU  36  has received the AF correcting data (ΔAFD 1 )  16   b , the procedure goes to Step S 18 . In step S 18 , the camera CPU  36  adds the measurement of focusing error (AFD) from the distance meter  46  with the AF correcting data (ΔAFD 1 )  16   b  to obtain a focusing error (AFD′) at the presence of the intermediate adapter  20 .  
         [0068]     When it is determined “yes” in step S 17 , i.e., the intermediate adapter is of the type B and the camera system is as shown in  FIG. 4 , the procedure goes to Step S 19 . In step S 19 , the camera CPU  36  retrieves the correcting factor α from the camera storage unit  40 . This is followed by Step S 20  where the camera CPU  36  adds the measurement of focusing error (AFD) from the distance meter  46  with a multiplication of the AF correcting data (ΔAFD 1 )  16   b  by the correcting factor α to obtain a focusing error (AFD′) at the presence of the intermediate adapter  20 .  
         [0069]     Finally, the corrected focusing error (AFD′) is transmitted from the camera CPU  36  to the lens CPU  15  where it is used for driving the camera lenses  11   a  and  11   b  to focus correctly.  
         [0070]     The calculation of the corrected focusing error (AFD′) in step S 20  is not limited to the multiplication of the AF correcting data (ΔAFD 1 )  16   b  by the correcting factor α but may involve addition (or subtraction) of the AF correcting data (ΔAFD 1 )  16   b  with the correcting factor α or use a function in which the AF correcting data (ΔAFD 1 )  16   b  and the correcting factor α are parameters.  
         [0071]     It is also possible for the camera CPU  36  to receive the AF correcting data (ΔAFD 1 )  16   b  and the correcting factor α to be used for AF correcting action not from the interchangeable lens  10  and the intermediate adapter  20  respectively but from any appropriate external peripheral (for example, a server) over a communicating means.  
         [0072]     While the foregoing embodiment includes different stages of the present invention, it is understood that various modifications are made by different combinations of the stages or disclosed members of the embodiment. For example, even if some members of the embodiment are deleted, the remaining members can overcome the drawbacks described in the paragraph of problems that the invention is to solve and provide the advantages described in the paragraph of the advantages of the invention, thus remaining in the scope of the present invention.