Patent Publication Number: US-11650483-B2

Title: Interchangeable lens, camera body, and electronic device

Description:
This is a Continuation of U.S. application Ser. No. 16/793,003 filed Feb. 18, 2020, which in turn is a Continuation of U.S. application Ser. No. 15/794,771 filed Oct. 26, 2017 (now U.S. Pat. No. 10,599,017), which is a Continuation of U.S. application Ser. No. 14/627,532 filed Feb. 20, 2015 (now U.S. Pat. No. 9,823,548), which is a Continuation of U.S. application Ser. No. 13/940,768 filed on Jul. 12, 2013 (now U.S. Pat. No. 8,995,069), which is a Continuation of U.S. application Ser. No. 13/745,464 filed Jan. 18, 2013 (now abandoned), which is a Continuation of U.S. application Ser. No. 13/033,166 filed Feb. 23, 2011 (now U.S. Pat. No. 8,400,722), which claims the benefit of U.S. Provisional Application No. 61/425,506 filed Dec. 21, 2010, and U.S. Provisional Application No. 61/430,211 filed Jan. 6, 2011. This application also claims priority to Japanese Application No. 2010-202104 filed Sep. 9, 2010, and Japanese Patent Application No. 2010-294513 filed Dec. 29, 2010. The disclosure of each of the earlier applications is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an interchangeable lens, a camera body and an electronic device. 
     2. Description of Related Art 
     There has been known a camera which electrically performs communication between the camera body and the interchangeable lens. Japanese Patent Laid-open Publication No. H07-234432 discloses an interchangeable lens that includes terminals for communicating with the camera body and terminals for communicating with an adapter such as an intermediate ring or rear focus converter. These two types of terminals constitute communication systems. When an adapter is attached, the interchangeable lens first communicates with the adapter via one of the communication systems. Then, the interchangeable lens communicates with the camera body via the other of the communication systems. 
     SUMMARY OF THE INVENTION 
     In the case of the camera body and interchangeable lens disclosed in the above publication, there is the possibility that when communication is performed by two independent communication systems simultaneously, the communication performed by one communication system could give an adverse effect on the communication performed by the other communication system. 
     An interchangeable lens to be detachably attached to a camera body, according to 1st aspect of the present invention, that includes a holding unit at which a plurality of contacts is arranged, the interchangeable lens comprises: a first communication contact system arranged at the holding unit, including a first contact through which a first clock signal output from the camera body is input, a second contact through which a first data signal output from the camera body in synchronization with the first clock signal is input, a third contact through which a second data signal is output to the camera body in synchronization with the first clock signal, and a fourth contact through which a first asynchronous signal that is asynchronous with the first clock signal is output to the camera body; and a second communication contact system different from the first communication contact system, arranged at the holding unit at a position different from a position at which the first communication contact system is arranged, the second communication contact system including a fifth contact through which a second clock signal is output to the camera body, a sixth contact through which a third data signal is output to the camera body in synchronization with the second clock signal, a seventh contact through which a second asynchronous signal that is asynchronous with the second clock signal is input from the camera body, and an eighth contact through which a third asynchronous signal that is asynchronous with the second clock signal is output to the camera body, wherein: the fourth contact is arranged at a position closer to the second communication contact system than the first contact, the second contact, and the third contact are, and the seventh contact and the eighth contact are arranged at positions closer to the first communication contact system than the fifth contact and the sixth contact are. 
     An interchangeable lens to be detachably attached to a camera body, according to a 2nd aspect of the present invention, that includes a holding unit at which a plurality of contacts is arranged, the interchangeable lens comprises: a first communication contact system arranged at the holding unit, including a first contact through which a first clock signal output from the camera body is input, a second contact through which a first data signal output from the camera body in synchronization with the first clock signal is input, a third contact through which a second data signal is output to the camera body in synchronization with the first clock signal, and a fourth contact through which a first asynchronous signal that is asynchronous with the first clock signal is output to the camera body; a second communication contact system different from the first communication contact system, arranged at the holding unit at a position different from a position at which the first communication contact system is arranged, the second communication contact system including a fifth contact through which a second clock signal is output to the camera body, a sixth contact through which a third data signal is output to the camera body in synchronization with the second clock signal, a seventh contact through which a second asynchronous signal that is asynchronous with the second clock signal is input from the camera body, and an eighth contact through which a third asynchronous signal that is asynchronous with the second clock signal is output to the camera body; a first communication device that receives the first data signal from the camera body using the second contact and transmits the second data signal to the camera body using the third contact based on the first asynchronous signal output from the fourth contact and the first clock signal input at the first contact; and a second communication device that transmits the third data signal to the camera body using the sixth contact based on the second asynchronous signal input at the seventh contact, the third asynchronous signal output from the eighth contact, and the second clock signal input at the fifth contact, wherein: the fourth contact is arranged at a position closer to the second communication contact system than the first contact, the second contact, and the third contact are, and the seventh contact and the eighth contact are arranged at positions closer to the first communication contact system than the fifth contact and the sixth contact are. 
     According to a 3rd aspect of the present invention the interchangeable lens according to the 1st aspect may further comprise: a driving device that drives a driven member; and a first power source contact system arranged at the holding unit at a position different from positions at which the first communication contact system and the second communication contact system are arranged, respectively, the first power source contact system including a ninth contact through which a drive voltage for driving the driving device is supplied from the camera body, and a tenth contact that is a ground germinal corresponding to the drive voltage, wherein the first power source contact system is arranged opposite to the first communication contact system with respect to the second communication contact system. 
     According to a 4th aspect of the present invention, in the interchangeable lens according to the 3rd aspect, in the first power source contact system, the tenth contact may be arranged closest to the second communication contact system. 
     According to a 5th aspect of the present invention, in the interchangeable lens according to the 4th aspect, in the second communication contact system, the sixth contact may be arranged closest to the tenth contact. 
     According to a 6th aspect of the present invention, the interchangeable lens according to the 5th aspect may further comprise: a second power source contact system arranged at the holding unit at a position different from positions at which the first communication contact system, the second communication contact system, and the first power source contact system are arranged, respectively, the second power source contact system including an eleventh contact through which an operation voltage having a different voltage value from the drive voltage is supplied from the camera body, and a twelfth contact that is a ground terminal corresponding to the operation voltage, wherein: a value of the operation voltage supplied to the eleventh contact is smaller than a value of the drive voltage supplied to the ninth contact; the first power source contact system is arranged opposite to the second communication contact system with respect to the first communication contact system; and the twelfth contact is arranged at a position closer to the first communication contact system than the eleventh contact is. 
     According to a 7th aspect of the present invention, in the interchangeable lens according to the 6th aspect, it is preferable that: the first contact is arranged opposite to the eleventh contact with respect to the twelfth contact; the third contact is arranged opposite to the second communication contact system with respect to the fourth contact; the second contact is arranged between the first contact and the third contact; the seventh contact is arranged opposite to the third contact with respect to the fourth contact; and the eighth contact is arranged opposite to the fourth contact with respect to the seventh contact. 
     According to a 8th aspect of the present invention, in the interchangeable lens according to the 6th aspect, the eleventh contact, the twelfth contact, the first contact, the second contact, the third contact, the fourth contact, the seventh contact, the eighth contact, the fifth contact, the sixth contact, the tenth contact, and the ninth contact may be arranged in that order at the holding unit in the form of a circular arc. 
     According to a 9th aspect of the present invention, in the interchangeable lens according to the 6th aspect, a difference between an upper limit and a lower limit of current that flows through the tenth contact may be greater than a difference between an upper limit and a lower limit of current that flows through the twelfth contact. 
     According to a 10th aspect of the present invention, the interchangeable lens according to the 2nd aspect may further comprise: a driving device that drives an optical member; a first power source contact system arranged at the holding unit at a position different from positions at which the first communication contact system and the second communication contact system are arranged, respectively, the first power source contact system including a ninth contact through which a drive voltage for driving the driving device is supplied from the camera body, and a tenth contact that is a ground terminal corresponding to the drive voltage; and a second power source contact system arranged at the holding unit at a position different from positions at which the first communication contact system, the second communication contact system, and the first power source contact system are arranged, respectively, the second power source contact system including an eleventh contact through which an operation voltage for the first communication device and the second communication device are supplied from the camera body, and a twelfth contact that is a ground terminal corresponding to the operation voltage, wherein: a value of the operation voltage supplied to the eleventh contact is smaller than a value of the drive voltage supplied to the ninth contact; the first power source contact system is arranged opposite to the second communication contact system with respect to the first communication contact system; the twelfth contact is arranged at a position closer to the first communication contact system than the eleventh contact is; the first contact is arranged opposite to the eleventh contact with respect to the twelfth contact; the third contact is arranged opposite to the second communication contact system with respect to the fourth contact; the second contact is arranged between the first contact and the third contact; the seventh contact is arranged opposite to the third contact with respect to the fourth contact; and the eighth contact is arranged opposite to the fourth contact with respect to the seventh contact. 
     According to a 11th aspect of the present invention, in interchangeable lens according to the 2nd aspect, one of the first communication device and the second communication device may be capable of performing communication with the camera body even when another of the first communication device and the second communication device performs communication with the camera body. 
     An interchangeable lens to be detachably attached to a camera body, according to a 12th aspect of the present invention, that includes a driven member, the interchangeable lens comprises: a first contact through which a first clock signal output from the camera body is input; a second contact through which a first data signal output from the camera body in synchronization with the first clock signal is input; a third contact through which a second data signal is output to the camera body in synchronization with the first clock signal; a fourth contact through which a first asynchronous signal that is asynchronous with the first clock signal is output to the camera body; a fifth contact through which a second clock signal is output to the camera body; a sixth contact through which a third data signal is output to the camera body in synchronization with the second clock signal; a seventh contact through which a second asynchronous signal that is asynchronous with the second clock signal is input from the camera body; an eighth contact through which a third asynchronous signal that is asynchronous with the second clock signal is output to the camera body; a ninth contact through which a drive voltage for driving the driven member is supplied from the camera body; a tenth contact that is a ground germinal corresponding to the drive voltage; an eleventh contact through which an operation voltage having a different voltage value from the drive voltage is supplied from the camera body; a twelfth contact that is a ground terminal corresponding to the operation voltage; and a holding unit at which the first to twelfth contacts are arranged, wherein: the eleventh contact is arranged on one end and the ninth contact is arranged on another end of the arrangement of the twelve contacts; the twelfth contact is arranged next to the eleventh contact in the arrangement of the twelve contacts; the first contact is arranged opposite to the eleventh contact with respect to the twelfth contact in the arrangement of the twelve contacts; the second contact is arranged opposite to the twelfth contact with respect to the first contact in the arrangement of the twelve contacts; the third contact is arranged opposite to the first contact with respect to the second contact in the arrangement of the twelve contacts; the fourth contact is arranged opposite to the third contact with respect to the second contact in the arrangement of the twelve contacts; the seventh contact is arranged opposite to the third contact with respect to the fourth contact in the arrangement of the twelve contacts; the eighth contact is arranged opposite to the fourth contact with respect to the seventh contact in the arrangement of the twelve contacts; the fifth contact is arranged opposite to the seventh contact with respect to the eighth contact in the arrangement of the twelve contacts; the sixth contact is arranged opposite to the fifth contact with respect to the eighth contact in the arrangement of the twelve contacts; and the tenth contact is arranged opposite to the fifth contact with respect to the sixth contact and next to the ninth contact in the arrangement of the twelve contacts. 
     According to a 13th aspect of the present invention, in the interchangeable lens according to the 12th aspect, a value of the drive voltage may be greater than a value of the operation voltage. 
     According to a 14th aspect of the present invention, in the interchangeable lens according to the 1st aspect, the driven member may include any of a member movable in a direction of optical axis of an optical system, a member movable in a direction perpendicular to the optical axis, and a member that is movable so as to change a size of an aperture through which a light flux passes. 
     A camera body, according to a 15th aspect of the present invention, which an interchangeable lens is to be detachably attached to and which includes a holding unit at which a plurality of contacts is arranged, the camera body comprises: a first communication contact system arranged at the holding unit, including a first contact through which a first clock signal is output to the interchangeable lens, a second contact through which a first data signal is output to the interchangeable lens in synchronization with the first clock signal, a third contact through which a second data signal is input from the interchangeable lens in synchronization with the first clock signal, and a fourth contact through which a first asynchronous signal that is asynchronous with the first clock signal is input from the interchangeable lens; and a second communication contact system different from the first communication contact system, arranged at the holding unit at a position different from a position at which the first communication contact system is arranged, the second communication contact system including a fifth contact through which a second clock signal is output to the interchangeable lens, a sixth contact through which a third data signal is input from the interchangeable lens in synchronization with the second clock signal, a seventh contact through which a second asynchronous signal that is asynchronous with the second clock signal is output to the interchangeable lens, and an eighth contact through which a third asynchronous signal that is asynchronous with the second clock signal is input from the interchangeable lens, wherein: the fourth contact is arranged at a position closer to the second communication contact system than the first contact, the second contact, and the third contact are; and the seventh contact and the eighth contact are arranged at positions closer to the first communication contact system than the fifth contact and the sixth contact are. 
     A camera body, according to a 16th aspect of the present invention, which an interchangeable lens is to be detachably attached to and which includes a holding unit at which a plurality of contacts is arranged, the camera body comprises: a first communication contact system arranged at the holding unit, including a first contact through which a first clock signal is output to the interchangeable lens, a second contact through which a first data signal is output to the interchangeable lens in synchronization with the first clock signal, a third contact through which a second data signal is input from the interchangeable lens in synchronization with the first clock signal, and a fourth contact through which a first asynchronous signal that is asynchronous with the first clock signal is input from the interchangeable lens; a second communication contact system different from the first communication contact system, arranged at the holding unit at a position different from a position at which the first communication contact system is arranged, the second communication contact system including a fifth contact through which a second clock signal is output to the interchangeable lens, a sixth contact through which a third data signal is input from the interchangeable lens in synchronization with the second clock signal, a seventh contact through which a second asynchronous signal that is asynchronous with the second clock signal is output to the interchangeable lens, and an eighth contact through which a third asynchronous signal that is asynchronous with the second clock signal is input from the interchangeable lens; a first communication device that transmits the first data signal to the interchangeable lens using the second contact and receives the second data signal from the interchangeable lens using the third contact based on the first asynchronous signal input at the fourth contact and the first clock signal output from the first contact; and a second communication device that receives the third data signal from the interchangeable lens using the sixth contact based on the second asynchronous signal output from the seventh contact, the third asynchronous signal input at the eighth contact, and the second clock signal output from the fifth contact, wherein: the fourth contact is arranged at a position closer to the second communication contact system than the first contact, the second contact, and the third contact are; and the seventh contact and the eighth contact are arranged at positions closer to the first communication contact system than the fifth contact and the sixth contact are. 
     According to a 17th aspect of the present invention, the camera body according to the 15th aspect may further comprise: a first power source contact system arranged at the holding unit at a position different from positions at which the first communication contact system and the second communication contact system are arranged, respectively, the first power source contact system including a ninth contact through which a drive voltage for driving a driven member of the interchangeable lens is supplied, and a tenth contact that is a ground terminal corresponding to the drive voltage, wherein: the first power source contact system is arranged opposite to the first communication contact system with respect to the second communication contact system. 
     According to a 18th aspect of the present invention, in the camera body according to the 17th aspect, in the first power source contact system, the tenth contact may be arranged closest to the second communication contact system. 
     According to a 19th aspect of the present invention, in the camera body according to the 18th aspect, in the second power source contact system, the sixth contact may be arranged closest to the tenth contact. 
     According to a 20th aspect of the present invention, the camera body according to the 19th aspect may further comprise: a second power source contact system arranged at the holding unit at a position different from positions at which the first communication contact system, the second communication contact system, and the first power source contact system are arranged, respectively, the second power source contact system including an eleventh contact through which an operation voltage having a different voltage value from the drive voltage is supplied to the interchangeable lens, and a twelfth contact that is a ground terminal corresponding to the operation voltage, wherein: a value of the operation voltage supplied to the eleventh contact is smaller than a value of the drive voltage supplied to the ninth contact; the first power source contact system is arranged opposite to the second communication contact system with respect to the first communication contact system; and the twelfth contact is arranged at a position closer to the first communication contact system than the eleventh contact is. 
     According to a 21st aspect of the present invention, in the camera body according to the 20th aspect, it is preferable that: the first contact is arranged opposite to the eleventh contact with respect to the twelfth contact; the third contact is arranged opposite to the second communication contact system with respect to the fourth contact; the second contact is arranged between the first contact and the third contact; the seventh contact is arranged opposite to the third contact with respect to the fourth contact; and the eighth contact is arranged opposite to fourth contact with respect to the seventh contact. 
     A camera body, according to a 22nd aspect of the present invention, which an interchangeable lens including a driven member is to be detachably attached, the interchangeable lens comprises: a first contact that outputs a first clock signal to the interchangeable lens; a second contact outputs a first data signal to the interchangeable lens in synchronization with the first clock signal; a third contact that inputs a second data signal from the interchangeable lens in synchronization with the first clock signal; a fourth contact that inputs a first asynchronous signal that is asynchronous with the first clock signal from the interchangeable lens; a fifth contact that outputs a second clock signal; a sixth contact that inputs a third data signal from the interchangeable lens in synchronization with the second clock signal; a seventh contact that outputs a second asynchronous signal that is asynchronous with the second clock signal to the interchangeable lens; an eighth contact that inputs a third asynchronous signal that is asynchronous with the second clock signal from the interchangeable lens; a ninth contact that supplies a drive voltage for driving the driven member of the interchangeable lens; a tenth contact that is a ground terminal corresponding to the drive voltage; an eleventh contact that supplies an operation voltage having a value different from a value of the drive voltage to the interchangeable lens; a twelfth contact that is a ground terminal corresponding to the operation voltage; and a holding unit at which the first to twelfth contacts are arranged, wherein: the eleventh contact is arranged on one end and the ninth contact is arranged on another end of the arrangement of the twelve contacts; the twelfth contact is arranged next to the eleventh contact in the arrangement of the twelve contacts; the first contact is arranged opposite to the eleventh contact with respect to the twelfth contact in the arrangement of the twelve contacts; the second contact is arranged opposite to the twelfth contact with respect to the first contact in the arrangement of the twelve contacts; the third contact is arranged opposite to the first contact with respect to the second contact in the arrangement of the twelve contacts; the fourth contact is arranged opposite to the third contact with respect to the second contact in the arrangement of the twelve contacts; the seventh contact is arranged opposite to the third contact with respect to the fourth contact in the arrangement of the twelve contacts; the eighth contact is arranged opposite to the fourth contact with respect to the seventh contact in the arrangement of the twelve contacts; the fifth contact is arranged opposite to the seventh contact with respect to the eighth contact in the arrangement of the twelve contacts; the sixth contact is arranged opposite to the fifth contact with respect to the eighth contact in the arrangement of the twelve contacts; and the tenth contact is arranged opposite to the fifth contact with respect to the sixth contact and next to the ninth contact in the arrangement of the twelve contacts. 
     An electronic device, according to a 23rd aspect of the present invention, which an interchangeable lens including a driven member is to be detachably attached, the electronic device comprises: a first contact that outputs a first clock signal to the interchangeable lens; a second contact outputs a first data signal to the interchangeable lens in synchronization with the first clock signal; a third contact that inputs a second data signal from the interchangeable lens in synchronization with the first clock signal; a fourth contact that inputs a first asynchronous signal that is asynchronous with the first clock signal from the interchangeable lens; a fifth contact that outputs a second clock signal; a sixth contact that inputs a third data signal from the interchangeable lens in synchronization with the second clock signal; a seventh contact that outputs a second asynchronous signal that is asynchronous with the second clock signal to the interchangeable lens; an eighth contact that inputs a third asynchronous signal that is asynchronous with the second clock signal from the interchangeable lens; a ninth contact that supplies a drive voltage for driving the driven member of the interchangeable lens; a tenth contact that is a ground terminal corresponding to the drive voltage; an eleventh contact that supplies an operation voltage having a value different from a value of the drive voltage to the interchangeable lens; a twelfth contact that is a ground terminal corresponding to the operation voltage; and a holding unit at which the first to twelfth contacts are arranged, wherein: the eleventh contact is arranged on one end and the ninth contact is arranged on another end of the arrangement of the twelve contacts; the twelfth contact is arranged next to the eleventh contact in the arrangement of the twelve contacts; the first contact is arranged opposite to the eleventh contact with respect to the twelfth contact in the arrangement of the twelve contacts; the second contact is arranged opposite to the twelfth contact with respect to the first contact in the arrangement of the twelve contacts; the third contact is arranged opposite to the first contact with respect to the second contact in the arrangement of the twelve contacts; the fourth contact is arranged opposite to the third contact with respect to the second contact in the arrangement of the twelve contacts; the seventh contact is arranged opposite to the third contact with respect to the fourth contact in the arrangement of the twelve contacts; the eighth contact is arranged opposite to the fourth contact with respect to the seventh contact in the arrangement of the twelve contacts; the fifth contact is arranged opposite to the seventh contact with respect to the eighth contact in the arrangement of the twelve contacts; the sixth contact is arranged opposite to the fifth contact with respect to the eighth contact in the arrangement of the twelve contacts; and the tenth contact is arranged opposite to the fifth contact with respect to the sixth contact and next to the ninth contact in the arrangement of the twelve contacts. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    presents a perspective view showing a camera system with interchangeable lenses according to the present invention; 
         FIG.  2    presents a cross-sectional view showing a camera system with interchangeable lenses according to the present invention; 
         FIG.  3    presents a schematic diagram showing details of holding units; 
         FIGS.  4 A and  4 B  present front views showing lens mounts; 
         FIG.  5    presents a timing chart illustrating an example of command data communication; and 
         FIGS.  6 A and  6 B  present timing charts illustrating examples of hot line communication. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     First Embodiment 
       FIG.  1    presents a perspective view showing a camera system with interchangeable lenses according to the present invention. In  FIG.  1   , only equipment and devices that relate to the present invention are shown but illustration and explanation on other equipment and devices are omitted. A camera  1  includes a camera body  100  and an interchangeable lens  200  that is detachably attached to the camera body  100 . 
     The camera body  100  is provided with a lens mount  101  which the interchangeable lens  200  can be detachably attached to. As shown in  FIG.  4 B , a holding unit that holds contacts (electrical connection part)  102  is provided at a position near the lens mount  101  (on an inner periphery side) of the camera body  100  such that the holding unit  102  partially projects on the inner periphery side of the lens mount  101 . The holding unit  102  is provided with a plurality of contacts. 
     The interchangeable lens  200  is provided with a lens mount  201  corresponding to the lens mount  101  on the camera body side, to which the camera body  100  can be detachably attached. As shown in  FIG.  4 B , a holding unit  202  is provided at a position near the lens mount  201  (on an inner periphery side) of the interchangeable lens  200  such that the holding unit  202  partially projects on the inner periphery side of the lens mount  201 . The holding unit is provided with a plurality of contacts. 
     When the interchangeable lens  200  is attached to the camera body  100 , the holding unit  102  provided with a plurality of contacts (which will be described later in detail) is electrically and physically connected to the holding unit  202  provided with a plurality of contacts (which will be described later in detail). The holding units  102  and  202  are used for supplying power from the camera body  100  to the interchangeable lens  200  and for transmitting and receiving signals between the camera body  100  and the interchangeable lens  200 . 
     At the back of the lens mount  101  in the camera body  100 , there is provided an image sensor  104 . Above the camera body  100 , there is provided a button  107  that serves as an input device. The user may send instructions to the camera body for imaging and for setting imaging conditions. 
       FIG.  2    presents a cross-sectional view showing a camera system with interchangeable lenses according to the present invention. The interchangeable lens  200  includes an imaging optical system  210  that forms an image of a subject. The imaging optical system  210  includes a plurality of lenses  210   a  to  210   c.  The plurality of lenses  210   a  to  210   c  includes a focusing lens  210   b  that controls a point of focus of a subject image. 
     Inside the interchangeable lens  200 , there is provided a lens-side control unit  203  that controls each unit of the interchangeable lens  200 . The lens-side control unit  203  includes a microcomputer (not shown) and its peripheral circuits (not shown). The lens-side control unit  203  is connected to a lens-side first communication unit  217 , a lens-side second communication unit  218 , a lens driving unit  212 , a lens position-detecting unit  213 , a ROM  215 , and a RAM  216 . 
     The lens-side first communication unit  217  and the lens-side second communication unit  218  transmit and receive data to and from the camera body  100  through the holding units  102 ,  202 , respectively. The lens-side first communication unit  217  and the lens-side second communication unit  218  are lens-side communication interfaces, respectively. A lens CPU  203  performs communications (hot-line communication and command data communication) which will be described later between it and the camera body  100  (a body-side control unit  103  on the camera side, which will be described later) by using these communication interfaces, 
     The lens driving unit  212  has an actuator such as a stepping motor and drives the focusing lens  210   b  in response to a signal that is input to the lens driving unit  212 . A lens position-detecting unit  213  counts the number of pulses that are input to the stepping motor in the lens driving unit  212  and detects the position of the focusing lens  210   b . Alternatively, the position of the focusing lens  210   b  may be detected by using a well-known distance encoder or the like provided in the interchangeable lens  200 . 
     A driven member other than the focusing lens  210   b  may be provided in the interchangeable lens  200 . For example, similarly to the focusing lens  210   b,  there may be provided, in the interchangeable lens  200 , a zoom lens as a member that can move in the direction of an optical axis of the interchangeable lens (imaging optical system  210 ) and a mechanism that electrically drives the zoom lens (which is also referred to as “power zoom mechanism”). Also, there may be provided, in the interchangeable lens  200 , an image blur correction mechanism including an image blur correction lens that can move in a moving direction containing components (X- and Y-direction components) perpendicular to the direction of the optical axis of the imaging optical system  210 . The image blur correction mechanism drives the image blur correction lens to perform image blur correction. Furthermore, there may be provided, in the interchangeable lens  200 , a power diaphragm mechanism that controls driving of diaphragm members (diaphragm blades), which are movable so that they can change the size of the aperture through which light flux from a subject passes. When such a driven member is provided, the lens-side control unit  203  controls the image blur correction lens, the diaphragm members, and the zoom lens for their driving and position detection by using the lens driving unit  212  and the lens position detecting unit  213 . 
     The ROM  215  is a nonvolatile storage medium, in which a predetermined control program or the like to be executed by the lens-side control unit  203  is stored in advance. The RAM  216  is a volatile storage medium, which is used as a storage area in which various data are stored by the lens-side control unit  203 . 
     In front of the image sensor  104 , there is provided a shutter  115  that controls an exposure state of the image sensor  104 , and an optical filter  116  that is combined with an optical low pass filter or an infrared cut filter in combination. A subject light that has been transmitted through the imaging optical system  210  is input to the image sensor  104  through the shutter  115  and the filter  116 . 
     Inside the camera body  100 , there is provided a body-side control unit  103  that controls each unit of the camera body  100 . The body-side control unit  103  includes a microcomputer (not shown), a RAM (not shown) and peripheral circuits therefor (not shown). 
     The body-side control unit  103  is connected to a body-side first communication unit  117  and a body-side second communication unit  118 . The body-side first communication unit  117  is connected to the holding unit  102  and can transmit data to and receive data from the lens-side first communication unit  217 . Similarly, the body-side second communication unit  118  can transmit data to and receive data from the lens-side second communication unit  218 . In other words, the body-side first communication unit  117  and the body-side communication unit  118  are communication interfaces, respectively, on the body side. The body-side control  103  performs communications (hot-line communication and command data communication) which will be described later between it and the interchangeable lens  200  (lens-side control unit  203 ) by using these communication interfaces. 
     On the back side of the camera body  100 , there is arranged a display unit  111  including an LCD panel or the like. The body-side control unit  103  an image of a subject based on the output from the image sensor  104  (so-called “through-image”) and various menu screens for setting various conditions including conditions for imaging. 
     Explanation on Holding Units  102 ,  202   
       FIG.  3    presents a schematic diagram showing details of the holding units  102 ,  202 .  FIG.  3    schematically illustrates the structure of the mount. As a result, the lens mount and the holding unit  102  of the camera body  100  are shown to be present on the same plane. However, in the actual structure of the mount, the holding unit  102  is set back far from a mount surface of the lens mount  101  of the camera body  100  (positioned on the right hand side with respect to the lens mount  101  in  FIG.  3   ). 
     Also,  FIG.  3    schematically illustrates the structure of the mount on the interchangeable lens side and the lens mount  201  of the interchangeable lens  200  and the holding unit  202  are shown to be present on the same plane. However, in actuality, the holding unit  202  is arranged at a position projected from the mount surface of the lens mount  101  (positioned on the right hand side with respect to the lens mount  201  in  FIG.  3   ). As such, when the mount surface of the lens mount  101  and the mount surface of the lens mount  201  are brought in contact with each other to mount and connect the camera body  100  and the interchangeable lens  200 , the holding unit  102  and the holding unit  202  are connected to each other and hence the electric contacts provided in the holding units also come to be connected to each other. Such a mount structure per se is well known and further explanation and illustration thereof is omitted here. 
     As shown in  FIG.  3   , twelve contacts BP 1  to BP 12  are present in the holding unit  102 . Also, in the holding unit  202 , there are twelve contacts LP 1  to LP 12  that correspond to BP 1  to BP 12 , respectively. 
     The contacts BP 1  and BP 2  are connected to a first power circuit  120  in the camera body  100 . The first power circuit  120  supplies to the contact BP 1  operation voltage for each unit in the interchangeable lens  200  exclusive of the lens driving unit  212 . That is, the contacts BP 1  and LP 1  supply operation voltage to each unit in the interchangeable lens  200  exclusive of the lens driving unit  212  (including a lens-side first communication unit  217  and a lens-side second communication unit  218 ). A value of voltage that can be supplied to the contact BP 1  is within the range of a minimum voltage value and a maximum voltage value (for example, in a voltage width in the order of 3 V). However, the value of voltage that is normally supplied is near an intermediate value of the maximum and minimum voltage values. From this it follows that the current value of current that is supplied from the camera body  100  to the interchangeable lens  200  is about several tens milliamperes (mA) to several hundreds milliamperes (mA) when the power is ON. 
     The contact BP 2  is a ground terminal corresponding to the operation voltage given to the contact BP 1 . That is, the contacts BP 2  and LP 2  are ground terminals corresponding to the operation voltage. 
     In the following explanation, a signal line via the contact BP 1  and the contact LP 1  is referred to as a signal line V 33 . A signal line via the contacts BP 2  and LP 2  is referred to as a signal line GND. The contacts LP 1 , LP 2 , BP 1 , and BP 2  constitute a power source system contacts dedicated for supplying power from the camera body  100  side to the interchangeable lens  200  side. 
     The contacts BP 3 , BP 4 , BP 5 , and BP 6  are connected to the body-side first communication unit  117 . The contacts LP 3 , LP 4 , LP 5 , and LP 6  on the interchangeable lens  200  side corresponding to the contacts BP 3 , BP 4 , BP 5 , and BP 6 , respectively, are connected to the lens-side first communication unit  217 . The body-side first communication unit  117  and the lens-side first communication unit  217  transmit and receive data therebetween using these contacts (communication system contacts). The contents of communication performed between the body-side first communication unit  117  and the lens-side first communication unit  217  will be described in detail later. 
     In the following explanation, a signal line via the contacts BP 3  and LP 3  is referred to as a signal line CLK. Similarly, a signal line via the contacts BP 4  and LP 4  is referred to as a signal line BDAT, a signal ling via the contacts BP 5  and LP 5  is referred to as a signal line LDAT, and a signal line via the contacts BP 6  and LP 6  is referred to as a signal line RDY. 
     The contacts BP 7 , BP 8 , BP 9 , and BP 10  are connected to the body-side second communication unit  118 . The contacts LP 7 , LP 8  LP 9 , and LP 10  on the interchangeable lens  200  side corresponding to the contacts BP′ 7 , BP 8 , BP 9 , and BP 10 , respectively, are connected to the lens-side second communication unit  218 . The lens-side second communication unit  218  transmits data to and receives data from the body-side second communication unit  118  using these contacts (communication contacts). The contents of communication between the body-side second communication unit  118  and the lens-side second communication unit  218  will be described in detail later. 
     In the following explanation, a signal line via the contacts BP 7  and LP 7  is referred to as a signal line HREQ. Similarly, a signal line via the contacts BP 8  and LP 8  is referred to as a signal line HANS, a signal ling via the contacts BP 9  and LP 9  is referred to as a signal line HCLK, and a signal line via the contacts BP 10  and LP 10  is referred to as a signal line HDAT. 
     The contacts BP 11  and BP 12  are connected to a second power circuit  121  in the camera body  100 . The second power circuit  121  also supplies to the contact BP 12  driving voltage for driving the lens driving unit  212 . That is, driving voltage for driving the driving unit  212  is supplied from the contacts BP 12  and LP 12 . The second power circuit  121  supplies ground voltage corresponding to the operation voltage. That is, ground voltage corresponding to the driving voltage is supplied from the contacts BP 11  and LP 11 . A value of voltage that can be supplied to the contact BP 12  is within the range of a minimum voltage value and a maximum voltage value. The range of the voltage value for the contact BP 12  is greater than the range of voltage value that can be supplied to the contact BP 1  (for example, the maximum value of the voltage that can be supplied to the contact BP 12  is on the order of several times the maximum value of the voltage that can be supplied to the contact BP 1 ). That is, the value of the voltage supplied to the contact BP 12  differs in magnitude from the value of the voltage supplied to the contact BP 1 . The value of the voltage normally supplied to the contact BP 12  is near an intermediate value of the maximum and minimum voltage values. From this it follows that the current value of current that is supplied from the camera body  100  to the interchangeable lens  200  is about several tens milliamperes (mA) to several amperes (A) when the power is ON. 
     The contact BP 11  is a ground terminal corresponding to the drive voltage given to the contact BP 12 . That is, the contacts BP 11  and the contact LP 11  are ground terminals corresponding to the drive voltage. 
     In the following explanation, a signal line via the contacts BP 11  and LP 11  is referred to as a signal line PGND. A signal line via the contacts BP 12  and LP 12  is referred to as a signal line BAT. The contacts LP 11 , LP 12 , BP 11 , and BP 12  constitute power source system contacts dedicated for supplying power from the camera body  100  side to the interchangeable lens  200  side. 
     From the magnitude relation between the value of the voltage (value of current) supplied to the contact BP 12  and the contact LP 12  and the value of the voltage (value of current) supplied to the contact BP 1  and the contact LP 1 , the following is apparent. That is, a difference between a maximum value and a minimum value of current that flows through the contacts BP 11  and LP 11  that serve as ground terminals for voltages supplied to the respective contacts is greater than a difference between a maximum value and a minimum value of current that flows through the contacts BP 2  and LP 2 . This is due to the fact that the driving unit  212  having a driving system such as an actuator consumes more power than that consumed by an electronic circuit of the lens-side control unit  203  or the like in the interchangeable lens  200  and that when the focus lens  210   b  does not have to be driven, the lens driving unit  212  consumes no power. 
       FIGS.  4 A and  4 B  present front views showing the lens mounts  101  and  201 , respectively.  FIG.  4 A  prevents a diagram showing the lens mount  201  for the interchangeable lens  200  as seen from the camera body  100  side.  FIG.  4 B  presents a diagram showing the lens mount  101  for the camera body  100  as seen from the interchangeable lens  200  side. 
     As shown in  FIG.  4 A , the contacts LP 3 , LP 4 , LP 5 , and LP 6  are arranged in an orderly fashion in the form of a circular arc in the direction along the lens mount  201  (circumferential direction along a part of the lens mount having a substantially circular shape) in the holding unit  202 . The contacts LP 7 , LP 8 , LP 9 , and LP 10  are arranged in an orderly fashion in the form of a circular arc in a direction of extension of the direction in which the contacts LP 3  to LP 6  is arranged. Here, the contact LP 6  is arranged at a position closer to the contacts LP 7  to LP 10  than to the contacts LP 3  to LP 5 . The contacts LP 7  and LP 8  are arranged at respective positions closer to the contacts LP 3  to LP 6  than the contacts LP 9  and LP 10  are. 
     The contacts LP 11  and LP 12  are arranged in an orderly fashion in the form of a circular arc in a direction of extension of the direction in which the contacts LP 3  to LP 6  are arranged (circumferential direction). The contacts LP 7  to LP 10  are arranged between the contacts LP 3  to LP 6  and the contacts LP 11  and LP 12 . The contact LP  10  is arranged next to the contact LP 11 . 
     The contacts LP 1  and LP 2  are arranged in an orderly fashion in the form of a circular arc in a direction of extension of the direction in which the contacts LP 3  to LP 6  are arranged (circumferential direction). The contacts LP 3  to LP 6  are arranged between the contacts LP 7  to LP 10  and the contacts LP 1  and LP 2 . The contact LP 2  is arranged at a position closer to the contacts LP 3  to LP 6  than the contact LP is. 
     That is, the twelve contacts LP 1  to LP 12  are arranged in an orderly fashion in the form of a circular arc. In the present embodiment, an angle of θ 1  of the circular arc (a sector formed by connecting the center of the mount, the center of the contact LP 1  and the center of the contact LP 12 ) is about 105 degrees. An angle of arc θ 2  between any two adjacent contacts is about 9.5 degrees. In the present embodiment, the width in the circumferential direction of each of the twelve contacts is about 1.5 mm. The distance between the center of mount and the center of each contact (LP 1  to LP 12 ) is about 15 mm. Therefore, the distance between the centers of any adjacent two contacts in the circumferential direction is about 2.5 mm. Since the width of each contact in the circumferential direction is about 1 mm, the clearance between any two adjacent contacts in the circumferential direction is about 1 mm. 
     The width of each contact and the clearance between any two adjacent contacts may be changed appropriately if needed or desired. For example, the width of each contact in the circumferential direction may be increased or decreased by a unit of 1/10 mm (by several tenths millimeters) and the clearance between any two adjacent contacts in the circumferential direction may be changed appropriately accordingly by a unit of 1/10 mm (by several tenths millimeters, for example, ±0.2 mm). 
     The contact LP 3  is arranged at a position adjacent to the contact LP 2 . The contact LP 5  is next to the contact LP 6 . The contact LP 4  is arranged between the contact LP 3  and the contact LP 5 . The contact LP 7  is arranged next to the contact LP 6 . The contact LP 8  is arranged next to the contact LP 9 . 
     Focusing on the contacts that supply voltage from the camera body  100  to the interchangeable lens  200 , the contacts are arranged as follows. The twelve contacts LP 1  to LP 12  are arranged in a circular arc in the holding unit  202 . The contact LP 12  is arranged at one end of the circular arrangement and the contact LP 1  is arranged at the other end of the circular arrangement. The contact LP 11  is arranged next to the contact LP 12  and the contact LP 2  is arranged next to the contact LP 1 . The contacts LP 3  to LP 6  are arranged next to the contact LP 2  in the form of a circular arc. The contacts LP 7  to LP 10  are arranged next to the contact LP 11  in the form of a circular arc. 
     That is, among the contacts arranged in a circular arc the contacts LP 1 , LP 11  that supply source voltage are arranged on both ends thereof. The contacts LP 2  and LP 11 , which are ground terminals corresponding to the source voltage, are arranged by one contact inner than the contacts LP 1  and LP 12 . The other communication system contacts LP 3  to LP 10  are arranged between the two contacts LP 2 , LP 11 , which are ground terminals. 
     The construction in which the contacts LP 3  to LP 10 , which are contacts for the communication system (communication system contacts), and the contacts LP 1  and LP 12 , which are power source system contacts that supply the power source voltage (the above-mentioned operation voltage and driving voltage) are intervened by the contacts LP 2  and LP 11  which are ground terminals therefor, is adopted in order to minimize influences that the power source system contacts (signal line) would give on the communication system contacts (signal line). 
     The signal line (i.e., signal line that includes LP 1  and LP 12 ) that supplies source voltage yields a large change in voltage in response to a change in load in a supply destination to which the source voltage is supplied. The large change in voltage may give adverse influences on the communications signal line. According to the present embodiment, a measure is taken to suppress the adverse influence as follows. That is, the contacts for ground terminals (ground contacts LP 2  and LP 11 ), which are more stable with respect the change in voltage than the power source contacts (LP 1  and LP 12 ), are arranged as intervening between the communication system contacts LP 3  to LP 10  and the power source contacts LP 1 , LP 12 . 
     The contacts LP 3  to LP 6  connected to the lens-side first communication unit  217  and the contacts LP 7  to LP 10  connected to the lens-side second communication unit  218  are arranged next to each other. On the contrary, the contacts LP 3 , LP 4 , and LP 5  of the lens-side first communication unit  217  and the contacts LP 9 , LP 10  of the lens-side second communication unit  218  are arranged such that the contacts belonging to one communication unit ( 217  or  218 ) are not arranged next to the contacts belonging to different (the other) communication unit ( 218  or  217 ). That is, at positions near the contacts connected to the different (other) communication unit, the contacts LP 6 , LP 7 , and LP 8  are arranged in lump. This is because the contacts LP 6 , LP 7 , and LP 8  are designed to transmit signals that do not synchronize with a clock signal (i.e., signals that will change to a relatively less extent as compared with the clock signal or a signal synchronizing therewith, for example, signals whose state change per unit time is on the order of 1 kilo Hertz (kHz) to several kilo Hertz (kHz)). Generally, the clock signal or signal synchronizing therewith will change vigorously to such an extent that change per unit time is on the order of several mega Hertz (MHz) (for example, in the case where the clock signal is at 8 MHz and data signal synchronizing therewith is 4 MHz (though depending on the amount of data)), they tend to be a source of noises. Therefore, it is desirable that such a terminal be arranged remote from the contacts connected to the different (other) communication unit so that the influence on communication can be minimized. Accordingly, in the present embodiment, the following countermeasure is adopted. That is, the group of the contacts that transmit signals that do not synchronize with the clock signal (contacts LP 6 , LP 7 , LP 8 ) are arranged so as to intervene between the group of the contacts that transmit clock signal or signals synchronizing therewith (contacts LP 3 , LP 4 , LP 5 ) in the lens-side first communication unit  217  and the group of the contacts that transmit the clock signal or signals synchronizing therewith in the lens-side second communication unit  218  (contacts LP 9 , LP 10 ). 
     The contacts LP 7  to LP 10  are arranged nearer the second power circuit  121  with respect to the contacts LP 3  to LP 6  whereas the contacts LP 3  to LP 6  are arranged nearer the first power circuit  120  with respect to the contacts LP 7  to LP 10 . This is because the contacts LP 7  to LP 10  are less influenced by noises. The second power circuit  121  supplies power to the lens driving unit  212 . The power consumption by the lens driving unit  212  changes considerably depending on whether or not the focusing lens  210   b  is driven. Therefore, the intensity of current that flows through the contact LP 11  changes considerably, so that the influence on the contact belonging to the adjacent communication system is greater than that given by the contact LP 2 . However, as described later, communication using the contacts LP 7  to LP 10  is of a shorter period than communication using the contacts LP 3  to LP 6  (that is, the period in which the communication is performed using the contacts LP 7  to LP 10  is on the order of 1/10 or less of the period of the communication performed using the contacts LP 3  to LP 6  and though described later, in the present embodiment, the communication performed using the contacts LP 7  to LP 10  is at a period of 16 msec whereas the communication performed using t e contacts LP 3  to LP 6  is at a period of 1 msec). As a result, even if the communication fails due to the influence of the contact LP 11 , the communication can be performed again immediately. In other words, the contacts LP 7  to LP 10  receive less influence by noises than the contacts LP 3  to LP 6  even when they are arranged next to the contact LP 11 . 
     The contact LP 10  is arranged next to the contact LP 11 . This is because the contact LP 10  is more resistant to noises than the contact LP 9 . As described later, the clock signal is transmitted through the contact LP 9  and data signal that synchronize with the clock signal are transmitted through the contact LP 10 . The clock signal cannot be synchronized on the receiving side when the leading edge or falling edge thereof becomes vague due to influences by noises. On the other hand, the data signal is sampled with respect to signal level at the timing of leading edge or falling edge of the clock signal. Therefore, it is only necessary that the signal level is clear at the above-mentioned timing, so that the data signal has a higher resistance to noises than the clock signal. 
     The contacts BP 1  to BP 12  arranged in the holding unit  102  on the camera body  100  side shown in  FIG.  4 B  are the same as the above-mentioned contacts LP 1  to LP 12  on the interchangeable lens  200  side. Accordingly, explanation thereof is omitted. As will be apparent from  FIGS.  1 ,  4 A and  4 B , the mount  101  on the camera body side is configured such that it can be engaged with the mount  201  on the interchangeable lens side by first facing the both mounts  101  and  201  each other and then rotating one with respect to the other. Therefore, the order in which the contacts BP 1  to BP 12  are arranged in the circumferential direction is in reverse to the order in which the contacts LP 1  to LP 12  are arranged in the circumferential direction as shown in  FIGS.  4 A and  4 B . That is, in  FIGS.  4 A and  4 B , the contact LP 1  is at the leftmost position and the contact LP 12  is at the rightmost position whereas the contact BP 1  is at the rightmost position and the contact BP 12  is at the leftmost position. 
     Explanation on Command Data 
     The lens-side control unit  203  controls the lens-side first communication unit  217  to receive control data from the body-side first communication unit  117  and transmit response data to the body-side first communication unit  117  through the contacts LP 3  to LP 6 , i.e., the signal lines CLK, BDAT, LDAT, and RDY concurrently in a first predetermined period (16 msec in the present embodiment). Hereafter, details of the communication performed between the lens-side first communication unit  217  and the body-side first communication unit  117  is explained. 
     In the present embodiment, the communication performed between the lens-side control unit  203  and the lens-side first communication unit  217  and the body-side control unit  103  and the body-side first communication unit  117  is referred to as “command data communication”. 
       FIG.  5    presents a timing chart illustrating an example of command data communication. The body-side control unit  103  and the body-side first communication unit  117  first check a signal level of the signal line RDY. The signal level of the signal line RDY indicates whether or not the communication of the lens-side first communication unit  217  is possible. The lens-side control unit  203  and the lens-side first communication unit  217  output a signal at a high (H) level through the contact LP 6  when communication is impossible. That is, the level of the signal line is set to an H level. When the signal line RDY is at an H level, the body-side control unit  203  and the body-side first communication unit  117  will not start communication until the signal line RDY becomes at an L (low) level. During communication, the following processes are not performed. 
     When the signal line RDY is at the L (low) level, the body-side control unit  103  and the body-side first communication unit  117  output a clock signal  401  through the contact BP 3 . That is, the body-side control unit  103  and the body-side first communication unit  117  transmit the clock signal  401  to the lens-side first communication unit  217  via the signal line CLK. The body-side control unit  103  and the body-side first communication unit  117  outputs a body-side command packet signal  402 , which is a front half of the control data through the contact BP 4  in synchronization with the clock signal  401 . That is, the body-side control unit  103  and the body-side first communication unit  117  transmit the body-side command packet signal  402  to the lens-side first communication unit  217  via the signal line BDAT. 
     When the clock signal  401  is output in the signal line CLK, the lens-side control unit  203  and the lens-side first communication unit  217  output a lens-side command packet signal  403 , which is a front half of the response data, through the contact LP 5  in synchronization with the clock signal  401 . That is, the lens-side control unit  203  and the lens-side first communication unit  217  transmit the lens-side command packet signal  403  to the body-side first communication unit  117  via the signal line LDAT. 
     The lens-side control unit  203  and the lens-side first communication unit  217  set the signal level of the signal line RDY to an H level in response to completion of transmission of the lens-side command packet signal  403  (T 2 ). The lens-side control unit  203  starts a first control process  404  (which will be described later). 
     When the first control process  404  is completed, the lens-side control unit  203  gives a notice of completion of the first control process  404  to the lens-side first communication unit  217 . In response to this notice, the lens-side first communication unit  217  outputs a signal at an L level through the contact LP 6 . That is, the lens-side first communication unit  217  sets the signal level of the signal line RDY to an L level (T 3 ). The body-side control unit  103  and the body-side first communication unit  117  outputs a clock signal  405  through the contact BP 3  in response to this change in the signal level. That is, the body-side control unit  103  and the body-side first communication unit  117  transmit the clock signal  405  to the lens-side first communication unit  217  via the signal line CLK. 
     The body-side control unit  103  and the body-side first communication unit  117  output, through the contact BP 4 , a body-side data packet signal  406 , which is a rear half of the control data, in synchronization with the clock signal  405 . That is, the body-side control unit  103  and the body-side first communication unit  117  transmit a body-side data packet signal  406  to the lens-side first communication unit  217  via the signal line BDAT. 
     When the clock signal  405  is output in the signal line CLK, the lens-side control unit  203  and the lens-side first communication unit  217  output a lens-side data packet signal  407 , which is a rear half of the response data, through the contact LP 5  in synchronization with the clock signal  405 . That is, the lens-side control unit  203  and the lens-side first communication unit  217  transmit the lens-side data packet signal  407  to the body-side first communication unit  117  via the signal line LDAT. 
     The lens-side control unit  203  and the lens-side first communication unit  217  again sets the signal level of the signal line RDY to an H level in response to completion of transmission of the lens-side data packet signal  407  (T 4 ). The lens-side control unit  203  starts a second control process  408  (which will be described later). 
     The first control process  404  and the second control process  408  performed by the lens-side control unit  203  are described hereafter. 
     For example, a case where the received body-side command packet signal  402  is to request specified data from the interchangeable lens is described. The lens-side control unit  203  performs, as the first control process  404 , an analysis process for analyzing the content of the command packet signal  402  and a process for generating the requested specified data. Further, the lens-side control unit  203  performs, as the first control process  404 , communication error check process in which whether an error has occurred in the communication of the command packet signal  402  is easily checked by based on the number of bytes of data by using check sum data contained in the command packet signal  402 . The signal of the specified data generated by the first control process  404  is output to the camera body as a lens-side data packet signal  407 . In this case, a body-side data packet signal  406 , which is output from the camera body after the command packet signal  402  has been output, is a dummy data signal (containing check sum data) which is meaningless to the interchangeable lens. In this case, the lens-side control unit  203  performs the above-mentioned communication error check process using the check sum data contained in the body-side data packet signal  406  as the second control process  408 . 
     For example, a case where the received body-side command packet signal  402  is, an instruction to drive a driven member in the lens is described. For example, a case where the command packet signal  402  is an instruction to drive the focus lens  210   b  and the received body-side data packet signal  406  indicates an amount of drive of the focus lens  210   b  is described. The lens-side control unit  203  performs, as the first control process  404 , an analysis process for analyzing the content of the command packet signal  402  and generates a roger signal indicating that the content of the command packet signal  402  has been understood. Further, the lens-side control unit  203  performs, as the first control process  404 , the communication error check process as mentioned above by using the check sum data contained in the command packet signal  402 . The roger signal generated in the first control process  404  is output to the camera body as a lens-side data packet signal  407 . The lens-side control  203  performs, as the second control process  408 , an analysis process for analyzing the content of the body-side data packet signal  406  and the communication error check process as mentioned above by using the check sum data contained in the body-side data packet signal  406 . 
     When the second control process  408  is completed, the lens-side control unit  203  gives a notice of completion of the second control process  408  to the lens-side first communication unit  217 . After this, the lens-side control unit  203  controls the lens-side first communication unit  217  to output a signal at an L level through the contact LP 6 . That is, the signal level of the signal line RDY is set to an L level (T 5 ). 
     When the received body-side command packet signal  402  is an instruction to drive the lens-side driven member (for example, a focusing lens) as mentioned above, the lens-side control unit  203  controls the lens-side first communication unit  217  to set the signal level of the signal line RDY to an L level and controls the lens driving unit  212  to perform a process to drive the focus lens  210   b  by the amount of drive instructed. 
     Each communication performed in a period from time T 1  to time T 5  constitutes a command data communication at one time. As mentioned above, in the command data communication at one time, one body-side command packet signal  402  and one body side-data packet signal  406  are transmitted by the body-side control unit  103  and the body-side data packet signal  406 , respectively. That is, although separately transmitted for the sake of convenience of processing, the two data, i.e., the body-side command packet signal  402  and the body-side data packet signal  406  constitute a single piece of control data. 
     Similarly, in the command data communication at one time, one lens-side command packet signal  403  and one lens-side data packet signal  407  are transmitted by the lens-side control unit  203  and the lens-side first communication unit  217 , respectively. That is, the lens-side command packet signal  403  and the lens-side data packet signal  407  together constitute one piece of response data. 
     As mentioned above, the lens-side control unit  203  and the lens-side first communication unit  217  receive control data from the body-side first communication unit  117  and transmit response data to the body-side first communication unit  117  concurrently. The contacts LP 6  and BP 6  used in the command data communication are contacts, through which other asynchronous signals that are not synchronized with the clock signal (the signal level of the signal line RDY being H (High) level or L (low) level) are transmitted. 
     Explanation on Hot-Line Transmission 
     The lens-side control unit  203  controls the lens-side second communication unit  218  to transmit lens position data to the body-side second communication unit  118  through the contacts LP 7  to LP 10 , i.e., via the signal lines HREQ, HANS, HCLK, and HDAT. Hereafter, communication performed between the lens-side second communication unit  218  and the body-side second communication unit  118  is explained in detail. 
     In the present embodiment, the communication performed between the lens-side control unit  203  and the lens-side second communication unit  218  and the body-side control unit  103  and the body-side second communication unit  118  is referred to as “hot-line communication”. 
       FIG.  6    presents a timing chart illustrating an example of hot-line communication. The body-side control unit  103  according to the present embodiment is configured such that hot-line communication is started for every second predetermined period (for example, 1 msec in the present embodiment). This period is shorter than the period in which the command data communication is performed.  FIG.  6 A  presents a diagram illustrating a state in which hot-line communication is performed for every predetermined period Tn.  FIG.  6 B  illustrates a state in which a time Tx required for one communication among repeatedly performed hot-line communications is shown in magnification. Hereafter, the procedure of hot-line communication is explained with reference to the timing chart shown in  FIG.  6 B . 
     The body-side control unit  103  and the body-side second communication unit  118  first output a signal at an L level through the contact BP 7  at the time of start of the hot-line communication (T 6 ). That is, the signal level of the signal line HREQ is set to an L level. The lens-side second communication unit  218  gives a notice indicating that the signal is input to the contact LP 7  to the lens-side control unit  203 . In response to this notice, the lens-side control unit  203  starts execution of a generation process  501  to generate lens position data. The generation process  501  is a process in which the lens-side control unit  203  controls a lens position detection unit  213  to detect the position of the focus lens  210   b  and generate lens position data that represents a result of the detection. 
     When the lens-side control unit  203  has completed execution of the generation process  501 , the lens-side control unit  203  and the lens-side second communication unit  218  output a signal at an L level through the contact LP 8  (T 7 ). That is, the signal level of the signal line HANS is set to an L level. The body-side control unit  103  and the body-side second communication unit  118  output a clock signal  502  through the contact BP 9  in response to the inputting of the signal in the contact BP 8 . That is, body-side control unit  103  and the body-side second communication unit  118  transmit the clock signal to the lens-side second communication unit  218  via the signal line HCLK. 
     The lens-side control unit  203  and the lens-side second communication unit  218  output a lens position data signal  503  through the contact LP 10  in synchronization with the clock signal  502 . That is, lens-side control unit  203  and the lens-side second communication unit  218  transmit the lens position data signal  503  to the body-side second communication unit  118  via the signal line HDAT. 
     When the transmission of the lens position data signal  503  is completed, the lens-side control unit  203  and the lens-side second communication unit  218  output a signal at an H level through the contact LP 8 . That is, the signal level of the signal line HANS is set to an H level (T 8 ). The body-side second communication unit  118  outputs a signal at an H level through the contact LP 7  in response to the inputting of the signal into the contact BP 8 . That is, the signal level of the signal line HREQ is set to an H level (T 9 ). 
     The communications performed during a period from time T 6  to time T 9  constitute a hot-line communication at one time. As mentioned above, in the hot-line communication at one time, only one lens position data signal  503  is transmitted by the lens-side control unit  203  and the lens-side second communication unit  218 . The contacts LP 7 , LP 8 , BP 7 , and BP 8  that are used for the hot-line communication are other contacts through which asynchronous signals that are not synchronized with the clock signal are transmitted. That is, the contacts LP 7  and BP 7  are contacts through which asynchronous signal (the signal level of the signal line HREQ being H (High) level, or L (low) level) are transmitted. The contacts LP 8  and BP 8  are contacts through which asynchronous signal (the signal level of the signal line HANS being H (High) level, or L (low) level) are transmitted. 
     The command data communication and the hot-line communication can be performed either simultaneously or partially concurrently. That is, one of the lens-side first communication unit  217  and the lens-side second communication unit  218  can perform communication with the camera body  100  even when the other of them is performing communication with the camera body  100 . 
     With the camera system according to the first embodiment as described above, the following advantageous effects can be obtained. 
     (1) At the holding unit  202  on the lens mount  201 , there are arranged in a circular arc the contact LP 3  through which the clock signals  401 ,  405  are transmitted from the camera body  100 , the contact LP 4  through which the body-side command packet signal  402  and the body-side data packet signal  406  are transmitted in synchronization with the clock signals  401 ,  405 , the contact LP 5  through which the lens-side command packet signal  403  and the lens-side data packet signal  407  are transmitted to the camera body  100  in synchronization with the clock signals  401 ,  405 , and the contact LP 6  through which asynchronous signals that are not synchronized with the clock signals  401 ,  405  are transmitted to the camera body  100 . At the holding unit  202  on the lens mount  201 , there are arranged in the direction of an extension of a circular arc the contact LP 9  through which the clock signal  502  is transmitted from the camera body  100 , the contact LP 10  through which the lens position data signal  503  is transmitted to the camera body  100  in synchronization with the clock signal  502 , the contact LP 7  through which an asynchronous signal that is not synchronized with the clock signal  502  is transmitted from the camera body  100 , and the contact LP 8  through which an asynchronous signal that is not synchronized with the clock signal  502  is transmitted to the camera body  100 . The lens-side first communication unit  217  receives control data from the camera body  100  and transmits response data to the camera body  100  through the contacts LP 3  to LP 6  concurrently. The lens-side second communication unit  218  transmits lens position data to the camera body  100  through the contacts LP 7  to LP 10 . One of the lens-side first communication unit  217  and the lens-side second communication unit  218  can perform communication with the camera body  100  even when the other of them performs communication with the camera body  100 . The contact LP 6  is arranged at a position closer to the contacts LP 7  to LP  10  than to the contacts LP 3  to LP 5 . The contacts LP 7  and LP 8  are arranged at positions closer to the contacts LP 3  to LP 6  than the contacts LP 9  and LP 10  are. With this construction, influences of the communication by one of the two independent communication systems upon the communication by the other can be minimized. 
     (2) At the holding unit  202  on the lens mount  201 , there are arranged the contact LP 12  through which the driving voltage of the lens drive unit  212  is supplied from the camera body  100 , and the contact LP 11  which serves as a ground terminal corresponding to the drive voltage in a direction of extension in a circular arc. Here, the contacts LP 7  to LP 10  are arranged between the contacts LP 3  to LP 6  and the contacts LP 10 , LP 11 . The contact LP 10  is arranged next to the contact LP 11 . With this construction, influences of the signal line BAT via which drive voltage of the driving unit  212  on the signal line via which hot-line communication is performed can be minimized. 
     (3) At the holding unit  202  on the lens mount  201 , there are arranged the contact LP 1  through which operation voltages for command data communication and hot-line communication (i.e., operation voltages for the lens-side first communication unit  217  and the lens-side second communication unit  218 ) are supplied from the camera body  100  and the contact LP 2  that serves as a ground terminal corresponding to the operation voltages in a direction of extension of in a circular arc. Here, a difference between an upper limit and a lower limit of current that flows through the contact LP 11  is greater than a difference between an upper limit and a lower limit of current that flows through the contact LP 2 . The contacts LP 3  to LP 6  are arranged between the contacts LP 7  to LP 10  and the contacts LP 1 , LP 2 . The contact LP 2  is arranged at a position closer to the contacts LP 3  to LP 6  than the contact LP 1  is. With this construction, influences of the signal line V 33  on the signal line for command data communication can be minimized. Influences of a change in current that flows in the signal line PGND upon the signal line of the communication system can be minimized. 
     (4) The contact LP 3  is arranged next to the contact LP 2 . The contact LP 5  is arranged next to the contact LP 6 . The contact LP 4  is arranged between the contacts LP 3  and LP 5 . The contact LP 7  is arranged next to the contact LP 6 . The contact LP 8  is arranged next to the contact LP 9 . As a result, influences by noises that occur between the respective contacts can be minimized. 
     (5) At the holding unit  202  on the lens mount  201 , there are arranged in the form of a circular arc twelve contacts: the contact LP 12  through which drive voltage for operating the lens driving unit  212  is supplied from the camera body  100 ; the contact LP 11  which is a ground terminal corresponding to the drive voltage; the contact LP 3  through which the clock signals  401 ,  405  are transmitted from the camera body  100 ; the contact LP 4  through which the body-side command packet signal  402  and the body-side data packet signal  406  are transmitted from the camera body  100  in synchronization with the clock signals  401 ,  405 ; the contact LP 5  through which the lens-side command packet signal  403  and the lens-side data packet signal  407  are transmitted to the camera body  100  in synchronization with the clock signal  401 ,  405 ; the contact LP 9  through which the clock signal  502  is transmitted from the camera body  100 ; the contact LP 10  through which the lens position data signal  503  is transmitted to the camera body  100  in synchronization with the clock signal  502 ; the contact LP 6  through which an asynchronous signal that is not synchronized with any of the clock signals  401 ,  405  and  502  is transmitted to the camera body  100 ; the contact LP 7  through which an asynchronous signal that is not synchronized with any of the clock signals  401 ,  405  and  502  is transmitted from the camera body  100 ; the contact LP 8  through which an asynchronous signal that is not synchronized with any of the clock signals  401 ,  405  and  502  is transmitted to the camera body  100 ; the contact LP 1  through which operation voltages for the lens-side first communication unit  217  and the lens-side second communication unit  218  are supplied from the camera body  100 ; and the contact LP 2  which is a ground terminal corresponding to the operation voltages. Here, the contact LP 12  is arranged on one end of the sequence of the twelve contacts and the contact LP 1  is on the other end of that sequence. The contact LP 11  is arranged next to the contact LP 12  and the contact LP 2  is arranged next to the contact LP 1 . With this construction, influences on the communication system by noises from outside can be suppressed. 
     (6) The contacts LP 3 , LP 4 , LP 5 , and LP 6  are arranged next to the contact LP 2  in the form of a circular arc. The contacts LP 7 , LP 8 , LP 9 , and LP 10  are arranged next to the contact LP 11  in the form of a circular arc. With this construction, mutual influences between two independent communication lines can be minimized. 
     Modifications described below are within the scope of the present invention and one or more variations may be combined with the above-mentioned embodiment(s). 
     Variation 1 
     In the above-mentioned embodiments, a plurality of contacts is arranged in a single row along the edge of the mount as shown in  FIGS.  4 A and  4 B . The plurality of contacts may be arranged in a single row in a form other than that shown in  FIGS.  4 A and  4 B . For example, a plurality of contacts may be arranged in a straight line. The plurality of contacts may be arranged at any desired positions of the lens mount  101 ,  201 .  FIGS.  4 A and  4 B  show the arrangement of the plurality of contacts on the lower part of the respective lens mounts  101  and  201 . However, they may be arranged on the upper part of the lens mounts  101 ,  201  or on both sides of the lens mounts  101 ,  201 . 
     Variation 2 
     In the above-mentioned embodiment, the position data of the focus lens  210   b  has been explained to be transmitted from the interchangeable lens  200  to the camera body  100  by hot-line communication. However, the system may be configured such that state information of a driven member other than the focus lens can be transmitted by hot-line communication. For example, when the interchangeable lens  200  is provided with an image blur correction lens, the position (X- and Y-position) of the image blur correction lens may be transmitted. Alternatively, the position of diaphragm in the interchangeable lens (information related to the diaphragm aperture size) may be transmitted. When the interchangeable lens is a zoom lens, information on focal length may be transmitted. In this case, the generation process  501  shown in  FIG.  6 B  includes a process for the generation of data of the position of the image blur correction lens, a process for the generation of data of control position of the diaphragm that forms a diaphragm aperture (information on position corresponding to aperture size), and a process for the generation of the data of the position of the zoom lens. 
     Variation 3 
     In the above-mentioned embodiment, the holding unit  102  (on the body side) and the holding unit  202  (on the interchangeable lens side) are each formed as an integrated component (a single component). However, the holding units  102  and  202  may each be configured to include a plurality of holding unit components divided into several groups (corresponding to respective contacts) which can be combined to provide an integrated holding unit. 
     Variation 4 
     In the above-mentioned embodiment, separate communication interfaces are provided for two types of communications (i.e., hot-line communication and command data communication). However, these interfaces may be integrated into a single interface. That is, referring to the interchangeable lens, the lens-side first communication unit  217  and the lens-side second communication unit  218  may be configured as one integrated unit. Similarly, referring to the camera body, the body-side first communication unit  117  and the body-side second communication unit  118  may be configured as one integrated unit. Further, a body-side control unit and a lens-side control unit each having the function of such a communication interface may be used instead of the body-side control unit  103  and the lens-side control unit  203 . 
     Variation 5 
     In the above-mentioned embodiment, the camera system including the camera body  100  and the interchangeable lens  200  has been described. However, the present invention is not limited to camera systems. The construction (the construction of the camera body) explained in the above-mentioned embodiment may be applied to any electronic device that includes a mount to which the interchangeable lens  200  can be detachably attached, is communicable with the interchangeable lens  200 , and can supply power to the interchangeable lens  200 . An example of such an electronic device is a projector. By configuring the projection lens component of a projector as a projection lens that can be detachably attached and interchangeable, a projector system similar to the above-mentioned embodiment can be obtained. 
     Variation 6 
     In the above-mentioned embodiment, explanation has been made on the image blur correction mechanism including an image blur correction lens that can move so as to have a motion vector containing a component in the direction perpendicular to the direction of optical axis of the imaging optical system  210  and can perform image blur correction by driving the image blur correction lens. However, the image blur correction mechanism is not limited to the above-mentioned one but may be one which performs image blur correction by rotating or swinging the image blur correction optical system in the pitching direction and the yawing direction of the camera system. 
     According to the above embodiments, an influence of the communication performed by one of two independent communication systems on the communication performed by the other of the communication systems can be minimized. 
     The present invention is not limited to the above-mentioned embodiment and various forms may be conceived within the technical concept of the present invention so far as the features of the present invention are not damaged. Such forms are also included within the scope of the present invention.