Abstract:
An interchangeable lens which can communicate with an associated camera body when the interchangeable lens is detachably attached to the camera body to exchange data of the interchangeable lens, the interchangeable lens includes a logic IC via which the interchangeable lens communicates with the camera body; and a memory which is provided independent of the logic IC, connected to the logic IC, and stores the data of the interchangeable lens.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to an interchangeable lens of a camera system. The camera system includes this interchangeable lens and a camera body to which the interchangeable lens is detachably attached. The present invention also relates to a method of performing data communications between the interchangeable lens and the camera body of the camera system. 
         [0003]    2. Description of the Related Art 
         [0004]    A conventional camera system is used by combining a camera body and an interchangeable lens selected from among various interchangeable lenses, and accordingly, each interchangeable lens incorporates a memory into which lens data inherent in the interchangeable lens is written so that the camera body reads out this lens data from the memory to use this lens data for controlling a photographic operation at a time of exposure. For instance, in conventional zoom lenses such as disclosed in U.S. Pat. No. 6,336,754 and Japanese Unexamined Patent Publication H11-231398, lens data is written into memory by a paging method for each focal length step because the lens data needs to be changed according to variations in focal length caused by a zooming operation. Upon the focal length of the zoom lens being changed, a page corresponding to the changed focal length is designated via hardware, and thereupon the camera body reads in all the data in this designated page. 
         [0005]    In conventional SLR camera systems using an interchangeable zoom lens, the camera body can read in lens data quickly because a change in focal length of the zoom lens switches via hardware from the currently-selected page to a page corresponding to the changed focal length. 
         [0006]    In recent years, in camera systems in which the camera body reads in lens data by carrying out communication with the interchangeable lens mounted to the camera body, it has been desired to enable a memory having an optimum memory capacity to be selected as a configuration in which a logic IC (gate array) serves as an interface on the interchangeable lens side and in which the memory is connected to the logic IC to enhance the degree of freedom in cost cutting and expansion of capability. Moreover, in this case also, it has been desired that the camera body can obtain lens data, which varies according to variations in focal length caused by a zooming operation or variations in object distance (photographing distance) caused by a focus adjusting operation, quickly without the need for the camera body to take the focal length and the object distance of the interchangeable lens into consideration. Furthermore, it has been desired that new exchange lenses having a larger amount of memory maintain compatibility with prior-art SLR camera bodies and camera systems. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention has been devised in view of the above described problems which arise in conventional interchangeable lenses, and provides a new interchangeable lens which can incorporate a memory having an appropriate memory capacity as necessary even if the required capacity of lens data varies depending on the type of the new interchangeable lens, and which does not require the memory management on the camera body side. 
         [0008]    According to an aspect of the present invention, an interchangeable lens is provided, which can communicate with an associated camera body when the interchangeable lens is detachably attached to the camera body to exchange data of the interchangeable lens, the interchangeable lens including a logic IC via which the interchangeable lens communicates with the camera body; and a memory which is provided independent of the logic IC, connected to the logic IC, and stores the data of the interchangeable lens. 
         [0009]    It is desirable for the logic IC to include a memory capacity set-pin for identifying a memory capacity of the memory. 
         [0010]    It is desirable for the interchangeable lens to include a zooming function; a zoom code detector which detects a zoom code by encoding each of a plurality of zooming ranges, which have been divided from a variable zooming range, as the zoom code; and a distance code detector which detects a distance code by encoding each of a plurality of object distance ranges, which have been divided from an object distance which varies by a focus adjusting operation, as the distance code, wherein lens data corresponding to the each different the distance code for each different the zoom code are stored in the memory in advance. 
         [0011]    It is desirable for the logic IC to include a first group of set-pins, a second group of set-pins and a third group of set-pins. Fixed data of the interchangeable lens are determined by levels of each of the set-pins of the first, second and third groups of set-pins, and the logic IC decodes the fixed data of the first, second and third groups of set-pins via the levels thereof and transmits the fixed data to the camera body. 
         [0012]    It is desirable for the logic IC to include a plurality of input pins via which the logic IC inputs the zoom code and the distance code which are detected by the zoom code detector and the distance code detector, respectively, wherein the logic IC selects a page of the memory in which lens data associated with the input zoom code and the input distance code is stored, from the zoom code and the distance code that the logic IC inputs via the plurality of input pins, and transmits the lens data written in the page to the camera body. 
         [0013]    It is desirable for the memory to include a page memory area and an extended memory area. 
         [0014]    It is desirable for a level of the memory capacity set-pin to be set to make the memory compliant with one of 1-byte addressing and 2-byte addressing in accordance with the memory capacity of the memory. 
         [0015]    It is desirable for the logic IC to perform communication with the camera body in synchronization with a clock signal output from the camera body, and when the level of the memory capacity set-pin is set to make the memory compliant with the 1-byte addressing in the communication performed by the logic IC, the logic IC does nothing to the memory and sends information of the first group of set-pins to the camera body upon a transition of the clock signal for a first byte; the logic IC sends a read command to the memory and sends information of the second group of set-pins to the camera body upon a transition of the clock signal for a second byte; the logic IC sends to the memory an address of 1 byte which corresponds to the zoom code and sends information of the third group of set-pins to the camera body upon a transition of the clock signal for a third byte; and the logic IC sends lens data sequentially output from the memory from a page thereof, which corresponds to the address to the camera body, upon transitions of the clock signal for a fourth byte and each byte thereafter. 
         [0016]    It is desirable for the logic IC to perform communication with the camera body in synchronization with a clock signal output from the camera body, and when the level of the memory capacity set-pin is set to make the memory compliant with the 2-byte addressing in the communication performed by the logic IC, the logic IC sends a read command to the memory and sends information on the first group of set-pins to the camera body upon a transition of the clock signal for a first byte; the logic IC sends the memory an address of a first byte which corresponds to the zoom code and sends information on the second group of set-pins to the camera body upon a transition of the clock signal for a second byte; the logic IC sends the memory an address of a second byte which corresponds to the zoom code and sends information on the third group of set-pins to the camera body upon a transition of the clock signal for a third byte; and the logic IC sends lens data sequentially output from the memory from pages thereof which correspond to the addresses of the first byte and the second byte to the camera body upon transitions of the clock signal for a fourth byte and each byte thereafter. 
         [0017]    It is desirable for the memory to be an EEPROM. 
         [0018]    In an embodiment, an interchangeable lens is provided, which can communicate with an associated camera body when the interchangeable lens is detachably attached to the camera body to exchange data of the interchangeable lens, the interchangeable lens including an interface circuit via which the interchangeable lens communicates with the camera body; and a memory which is provided independent of the interface circuit, connected to the interface circuit, and stores the data of the interchangeable lens, wherein the interface circuit includes a memory capacity set-pin identifying a memory capacity of the memory. 
         [0019]    In an embodiment, a lens data communication method of performing data communications between the interchangeable lens and the camera body is provided, wherein the logic IC performs communication with the camera body in synchronization with a clock signal output from the camera body, and wherein, when the level of the memory capacity set-pin is set to make the memory compliant with the 1-byte addressing in the communication performed by the logic IC, the logic IC does nothing to the memory and sends information on the first group of set-pins to the camera body upon a transition of the clock signal for a first byte; the logic IC sends a read command to the memory and sends information on the second group of set-pins to the camera body upon a transition of the clock signal for a second byte; the logic IC sends the memory an address of 1 byte which corresponds to the zoom code and sends information of the third group of set-pins to the camera body upon a transition of the clock signal for a third byte; and the logic IC sends lens data sequentially output from the memory from a page thereof which corresponds to the address to the camera body upon transitions of the clock signal for a fourth byte and each byte thereafter. When the level of the memory capacity set-pin is set to make the memory compliant with the 2-byte addressing in the communication performed by the logic IC, the logic IC sends a read command to the memory and sends information of the first group of set-pins to the camera body upon a transition of the clock signal for a first byte; the logic IC sends to the memory an address of a first byte which corresponds to the zoom code and sends information of the second group of set-pins to the camera body upon a transition of the clock signal for a second byte; the logic IC sends to the memory an address of a second byte which corresponds to the zoom code and sends information of the third group of set-pins to the camera body upon a transition of the clock signal for a third byte; and the logic IC sends lens data sequentially output from the memory from pages thereof which correspond to the addresses of the first byte and the second byte to the camera body upon transitions of the clock signal for a fourth byte and each byte thereafter. 
         [0020]    It is desirable for the memory to be an EEPROM. 
         [0021]    According to the present invention, it is possible to incorporate a memory having an optimum memory capacity into the interchangeable lens even if the capacity of the memory incorporated in the interchangeable lens differs from that required by the camera body, to which the interchangeable lens is mounted. Specifically, even if the necessary memory capacity increases so as to be much greater than before, a large-capacity memory can be easily incorporated into the interchangeable lens while maintaining the compatibility with conventional products. 
         [0022]    Since the switching between pages of the memory (addressing thereof) is done by the logic IC of the interchangeable lens, memory address management on the camera body side is not necessary, which makes it possible for the camera body to read lens information from the interchangeable lens by a simple communication algorithm. 
         [0023]    The present disclosure relates to subject matter contained in Japanese Patent Application No. 2006-304711 (filed on Nov. 10, 2006) which is expressly incorporated herein in its entirety. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    The present invention will be discussed below in detail with reference to the accompanying drawings, in which: 
           [0025]      FIG. 1  is a block diagram showing the main components of an SLR camera system having an interchangeable lens according to the present invention; 
           [0026]      FIGS. 2A and 2B  show a first embodiment of memory maps of a memory incorporated in the interchangeable lens according to the present invention, wherein  FIG. 2A  shows a memory map of data in a conventional area of the memory and  FIG. 2B  shows a memory map of data in an extended area of the memory that uses an indexed addressing mode; 
           [0027]      FIGS. 3A and 3B  show a second embodiment of the memory maps of the memory incorporated in the interchangeable lens according to the present invention, wherein  FIG. 3A  shows a memory map of data in a conventional area of the memory and  FIG. 3B  shows a memory map of data in an extended area of the memory that uses a common-data extension mode; 
           [0028]      FIG. 4  is a flow chart showing an embodiment of an AF process performed in an SLR camera system including the interchangeable lens according to the present invention; 
           [0029]      FIG. 5  is a flow chart showing an embodiment of a lens communication process performed in the SLR camera system including the interchangeable lens according to the present invention; 
           [0030]      FIG. 6  is a flow chart showing an embodiment of an extended lens communication process performed in the SLR camera system including the interchangeable lens according to the present invention; 
           [0031]      FIG. 7  is a flow chart showing an embodiment of an LROM communication process performed in the interchangeable lens according to the present invention; 
           [0032]      FIGS. 8A and 8B  are timing charts showing a general overview of communications performed in the SLR camera system including the interchangeable lens according to the present invention; 
           [0033]      FIGS. 9A ,  9 B and  9 C are timing charts for lens CPU communication performed in the SLR camera system including the interchangeable lens according to the present invention, wherein  FIG. 9A  shows communications between the camera body and the interchangeable lens (lens interface IC) and  FIGS. 9B and 9C  each show communications between the lens interface IC and the lens CPU; 
           [0034]      FIGS. 10A and 10B  are timing charts for the LROM communication performed in the SLR camera system including the interchangeable lens according to the present invention, wherein  FIG. 10A  shows communications between the camera body and the interchangeable lens (lens interface IC) and  FIG. 10B  shows communications between the lens interface IC and an EEPROM; 
           [0035]      FIG. 10C  is a data table showing information on set-pins and the contents thereof; 
           [0036]      FIG. 11A  is a timing chart showing a set-pin reading process performed in the SLR camera system including the interchangeable lens of the present invention; 
           [0037]      FIG. 11B  is a data table showing an embodiment of the contents of set-pins; and 
           [0038]      FIGS. 12A ,  12 B and  12 C are timing charts showing a read/write process performed in the SLR camera system including the interchangeable lens of the present invention, wherein  FIG. 12A  shows operations for write enable,  FIG. 12B  shows operations for writing, and  FIG. 12C  shows operations for reading. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0039]    An SLR camera system shown in  FIG. 1  is composed of a camera body  10  and an interchangeable lens  50  which is detachably attached to the camera body  10 . The camera body  10  is provided with a camera CPU  11 , a camera peripheral circuit  13  and a battery  15 . The camera CPU  11  comprehensively controls the overall operations of the SLR camera system, the camera peripheral circuit  13  performs auxiliary operations while carrying out communications with the camera CPU  11 , and the battery  15  supplies power to the camera CPU  11 , the camera peripheral circuit  13  and the interchangeable lens  50  mounted to the camera body  10 . 
         [0040]    On the other hand, the interchangeable lens  50  is provided with a lens CPU  51 , a lens peripheral circuit  53 , an EEPROM (memory)  55  and a lens interface IC (gate array/logic IC)  57 . The lens CPU  51  controls the operation of the interchangeable lens  50 , the lens peripheral circuit  53  drives a built-in AF motor and other components incorporated in the interchangeable lens  50  under control of the lens CPU  51 , the EEPROM  55  serves as a nonvolatile memory in which lens data is stored, and the lens interface IC  57  serves as a logic IC (interface circuit) which relays communications between the camera CPU  11  and the lens CPU  51  and between the camera CPU  11  and the EEPROM  55 . The electronic circuit incorporated in the interchangeable lens  50  operates with power supplied from the camera peripheral circuit  13 . In the present embodiment, SPI (Serial Peripheral Interface) is adopted as a communication mode for the EEPROM  55 . 
         [0041]    Similar to conventional SLR cameras, the camera body  10  is provided with basic components such as a phase-difference AF sensor unit and a built-in AF motor. On the other hand, the interchangeable lens  50  is provided with basic components such as a zoom optical system, a diaphragm mechanism and a focus adjusting mechanism which are similar to those provided in conventional zoom lenses. The interchangeable lens  50  can further be provided therein with a built-in AF motor which drives the focus adjusting mechanism as a substitute for a manual operation or the built-in AF motor (not shown) of the camera body. 
         [0042]    The lens interface IC  57  is provided with a plurality of set-pins and uses one of these set-pins as a capacity set-pin (memory capacity set-pin EEP). The number of bytes required for the lens interface IC  57  to address the EEPROM  55  is changed in accordance with the level of the memory capacity set-pin EEP. Although addressing is possible with only one byte if the memory capacity is small, two bytes are required if the memory capacity is large. Accordingly, the memory capacity set-pin EEP is set to a low (“L”) level when addressing is performed using one byte, and the memory capacity set-pin EEP is set to a high (“H”) level when addressing is performed using two bytes. In this manner, since the number of bytes for addressing can be selected according to the memory capacity, the lens interface IC  57  can be made to comply with the memory capacity of the EEPROM  55 . 
         [0043]    In the present embodiment of the SLR camera system, a memory capacity equal to or smaller than 4 kilobits (addressing 9 bits) is regarded as a small memory capacity, and a memory capacity equal to or greater than 8 kilobits (addressing 10 bits) is regarded as a large memory capacity. SPI is adopted as a communication mode for the EEPROM  55 . The capacity of the EEPROM  55  in the present embodiment is equal to or greater than 8 kilobits. Accordingly, the memory capacity set-pin EEP is set to a high level in the present embodiment. 
         [0044]    Additionally, in the present embodiment, distance codes are allocated to three input pins DC 0  through DC 2  provided on the lens interface IC  57 , and zoom codes are allocated to eight input pins ZC 0  through ZC 7  provided on the lens interface IC  57 . The interchangeable lens  50  is provided therein with a distance code output device  61  which is connected to the input pins DC 0  through DC 2 . The distance code output device  61  makes it possible to detect the current object distance by dividing the range of the variable object distance (photographing distance) into a plurality of ranges and outputting distance codes for identifying the plurality of ranges, respectively, to the input pins DC 0  through DC 2 . The interchangeable lens  50  is provided therein with a zoom code output device  63  which is connected to the input pins ZC 0  through ZC 7 . The zoom code output device  63  makes it possible to detect the current focal length range by dividing the range of the variable focal length (variable zooming range) into a plurality of ranges and outputting zoom codes (focal-length codes) for identifying the plurality of ranges, respectively, to the input pins ZC 0  through ZC 7 . Versatile codes regarding versatile data are allocated to four input pins GP 0  through GP 3 , and each of the input pins GP 0  through GP 3  sets a high/low signal depending on whether it is grounded or not. 
         [0045]    A known distance code output device and a known zoom code output device are used as the distance code output device  61  and the zoom code output device  63 , respectively. For instance, the distance code output device  61  is made up of a code plate fixed to a movable lens barrel, or the like, which moves relative to a focusing lens group, and a brush which moves with the focusing lens group while sliding on the code plate. More specifically, the range of a code pattern formed on the code plate is divided into a number of ranges which makes it possible to identify the distance range from the closest object distance to the infinite object distance with 3 bits, and a distance code consisting of electrical 3-bit high/low signals generated by sliding contacts of resilient conductive strips of the brush with conductive portions of each of the divided ranges of the code pattern is allocated to each of the divided ranges of the code pattern. An electrical high/low signal which corresponds to the range of code pattern with which the brush is in contact is input to the input pins DC 0  through DC 2  as a distance code. Similarly, the zoom code output device  63  is made up of an 8-bit code plate and a brush, and an electrical high/low signal corresponding to the focal length range, which is generated by sliding contacts of resilient conductive strips of the brush with conductive portions of each of the divided ranges of the code pattern on the 8-bit code plate, is input to the input pins ZC 0  through ZC 7  as a distance code. 
         [0046]    The lens interface IC  57  is provided with a logic circuit which decodes the distance code of a combination of high/low settings of the distance-code input pins DC 0  through DC 2 , and the zoom code of a combination of high/low settings of the zoom-code input pins ZC 0  through ZC 7  to address the corresponding page of the EEPROM  55 . 
         [0047]    The camera body  10  can read out lens data stored in the page addressed by the distance-code input pins DC 0  through DC 2  and the zoom-code input pins ZC 0  through ZC 7  from the EEPROM  55 . The camera body  10  carries out communications with the EEPROM  55  by addressing performed by the lens interface IC  57  physically and sequentially in accordance with the levels of the distance-code input pins DC 0  through DC 2  and the zoom-code input pins ZC 0  through ZC 7 . 
         [0048]    Since a circuit incorporated in the interchangeable lens  50  can switch between the corresponding pages of the EEPROM  55  by a zoom code signal and a distance code signal which vary by a zooming operation and a distance adjusting operation, respectively, the camera body  10  does not have to take charge of memory administration and can rapidly obtain lens data which corresponds to the currently-set focal length and the currently-set object distance. 
         [0049]    The EEPROM  55  is provided with a page memory area and an extended memory area for addressing. In each page of the EEPROM  55 , lens data corresponding to a combination of an object distance and a focal length is written. For instance, in the EEPROM  55  of the interchangeable lens  50 , data corresponding to a zoom code is written in each page by a paging method that is adopted by conventional interchangeable lenses (see  FIGS. 2A and 3A ). Additionally, in these embodiments, the EEPROM  55  is provided with a ROM area for data access performed by addressing (see  FIGS. 2B and 3B ). According to a conventional method, pages are switched from one page to another by a zoom code, and data is read out of the page in which the data is written. In the present invention, each page secures a capacity of 16 bytes from PD 0  through PD 15 , and predetermined data are allocated to each page in units of two bytes. 
         [0050]    In  FIGS. 2A through 3B , there are eight pages 00 through 07 in total, so that each page can be addressed by one byte. Although the number of pages can be increased up to 32 pages at maximum even in the case of 1-byte addressing (addressing 9 bits) if one page consists of 16 bytes, the number of pages can further be increased beyond 32 pages in the present embodiment by also making the EEPROM  55  compliant with 2-byte addressing. Namely, since the range of variable focal lengths can further be divided into a large number of ranges, appropriate data according to the focal length can be stored in the EEPROM  55  even in an interchangeable zoom lens having a high zoom power. In this case also, the communication algorithm of the camera body does not have to be changed. 
         [0051]      FIG. 2B  shows a first embodiment of an indexed addressing mode that makes it possible to further add data to zoom data controlled according to a paging method. In the indexed addressing mode, an area of 8 bytes (addresses FFF8h through FFFFh) is secured as an index, and the start address of additional zoom data and the number of bytes of the additional zoom data, and the start address of additional common data and the number of bytes of the additional common data are set as index data. By reading in this index data, the addresses and the data length of the additional zoom data and the additional common data can be determined, and reading of these data becomes possible. 
         [0052]    Although the memory capacity in this example is the maximum capacity of 512 kilobits that 2-byte addressing can deal with, index data of 8 bytes arranged from the end address can be read in at all times by addressing addresses FFF8h through FFFFh if the capacity of the memory is equal to or greater than 8 kilobits: the minimum capacity for 2-byte addressing. Of course, it is possible to adopt the indexed addressing mode in a similar manner in the case of 1-byte addressing simply by changing the addressing of the addresses to 1F8h through 1FFh. 
         [0053]      FIG. 3B  shows a second embodiment in which common data is added to an area different from the area determined by the conventional paging method. Common data can be read in by addressing from the maximum address regardless of the memory capacity due to the common data being sequentially arranged from the end address thereof. For instance, although the total memory capacity is 256 bytes (2 kilobits) in the case shown in  FIG. 3B , the end address FFh of 256 bytes can be addressed by the maximum address 1 FFh in 1-byte addressing (9 bits). If the total memory capacity becomes insufficient due to an increase in number of pages or an increase of common data from the state of memory location shown in  FIG. 3B , the EEPROM  55  can deal with this situation simply by changing the 2 kilobit memory to a 4 kilobit memory and arranging common data in a similar manner from the end address (1 FFh). 
         [0054]    In the second embodiment, the amount of movement of a focal plane per pulse of AF pulses (Δfocal plane/AF pulse) is set as additional zoom data for each range of a plurality of focal length ranges. As common data, the version of ROM data and the date/month/year of manufacture are set. These data are read by computing addresses based on the start address and the number of bytes of data which are read in from the index data and also based on a zoom code (and a distance code if necessary) obtained via a code-plate-information communication. 
         [0055]    According to this paging method, in the interchangeable lens  50 , only the page data of the EEPROM  55  which corresponds to a zoom code can be read out of the EEPROM  55  when the interchangeable lens  50  is mounted to a conventional camera body which is non-compatible with neither the common-data extension mode nor the indexed addressing mode. When the interchangeable lens  50  is mounted to a camera body compliant with the common-data extension mode and the indexed addressing mode, additional data set according to the common-data extension mode or the indexed addressing mode can be read out of the EEPROM  55  in addition to the page data of the EEPROM  55  which corresponds to a zoom code. 
         [0056]    An AF process including a process of reading the above described data in this camera system will be hereinafter discussed with reference to the flow charts shown in  FIGS. 4 through 7  and the timing charts shown in  FIGS. 8A through 12C . The processes shown in  FIGS. 4 through 6  are controlled by the camera CPU  11  in the camera body  10 . The process shown in  FIG. 7  is a sequence of operations of the lens interface IC  57  in the interchangeable lens  50 . 
         [0057]    The AF process shown in  FIG. 4  corresponds to a subroutine included in a main process performed in a conventional camera system, and is called up from the main process immediately after, e.g., a photometering switch is turned ON by a half depression of the release button (not shown) of the camera body  10 . The AF process will be discussed with reference to  FIGS. 8A and 8B  that show an overview of the timing of main communications performed in the camera system shown in  FIG. 1 . 
         [0058]    In the AF process, firstly the camera body  10  carries out communication (lens communication) with the interchangeable lens  50  (step S 101 ). In this lens communication, only LROM (lens ROM) communication, i.e., ‘fixed data communication’ is carried out. Namely, the camera CPU  11  reads page data, from the interchangeable lens  50 , stored in the EEPROM  55  which is addressed by the input pins DC 0  through DC 2  and the input pins ZC 0  through ZC 7 . 
         [0059]    Subsequently, it is determined whether or not the interchangeable lens mounted to the camera body  10  is an interchangeable lens compliant with either the common-data extension mode or the indexed addressing mode, i.e., whether or not the interchangeable lens mounted to the camera body  10  is the interchangeable lens  50  that is compliant with an extended lens communication (step S 103 ). If the interchangeable lens mounted to the camera body  10  is compliant with the extended lens communication (if YES at step S 103 ), the extended lens communication is carried out (step S 105 ). In the extended lens communication, the camera CPU  11  refers to index data to read the data from the EEPROM  55  which is located at the address corresponding to the distance code and the zoom code. If the interchangeable lens mounted to the camera body  10  is not compliant with the extended lens communication (if NO at step S 103 ), control skips step S 105 , i.e., proceeds from step S 103  to step S 107 . 
         [0060]    Subsequently, focus detection data (data on a pair of object images) is received from the aforementioned AF sensor unit (step S 107 ) and a defocus calculation operation by phase difference is carried out to determine a defocus amount (step S 109 ). Thereafter, it is determined whether or not an in-focus state has been obtained based on the defocus amount thus determined (step S 111 ), and the AF process completes if an in-focus state has been obtained (if YES at step S 111 ). If an in-focus state has not been obtained (if NO at step S 111 ), operations from step S 113  onwards are performed. 
         [0061]    At step S 113  the number of AF drive pulses and the driving direction of the focusing lens group (AF motor) which are necessary for bringing a main object into focus are calculated based on the determined defocus amount, and if lens data (A focal plane/AF pulse) according to the object distance has been received via the extended lens communication performed at step S 105 , the number of AF drive pulses is adjusted based on this lens data. Subsequently, it is determined whether or not the interchangeable lens mounted to the camera body  10  incorporates the lens CPU  51  and the AF motor (step S 115 ). If no AF motor is incorporated in the interchangeable lens mounted to the camera body  10  (if NO at step S 115 ), the built-in AF motor of the camera body  10  is driven to rotate in the driving direction determined at step S 113  by a few pulses (step S 121 ) and control returns to step S 107 . The above described loop process from step S 107  to step S 121  via steps S 109 , S 111  (if NO thereat), S 113  and S 115  (if NO thereat) is repeated unless an in-focus state is obtained, and the AF process ends upon an in-focus state being obtained (if YES at step S 111 ). 
         [0062]    If the interchangeable lens mounted to the camera body  10  is the interchangeable lens  50  that incorporates an AF motor (if YES at step S 115 ), the camera body  10  carries out communication (lens communication) with the interchangeable lens  50  to send data on the driving direction and the adjusted number of drive pulses to the interchangeable lens  50  to make the lens CPU  51  drive the built-in AF motor of the interchangeable lens  50  (step S 117 ). Subsequently, the camera CPU  11  waits for a built-in-motor-drive termination signal, that is output from the lens CPU  51 , via a communication with the interchangeable lens  50  (step S 119 ). Upon the camera CPU  11  receiving the built-in-motor-drive termination signal, control returns to step S 107 . The above described loop process from step S 107  to step S 119  via steps S 111  (if NO thereat), S 113 , S 115  (if YES thereat) and S 117  is repeated unless an in-focus state is obtained, and the AF process ends upon an in-focus state being obtained (if YES at step S 111 ). The lens CPU  51  drives the built-in AF motor of the interchangeable lens  50  by an amount corresponding to the AF drive pulses received from the camera body  10 , and outputs the aforementioned built-in-motor-drive termination signal to the camera CPU  11  via the lens interface IC  57  upon completion of the drive of the built-in AF motor of the interchangeable lens  50 . 
         [0063]    Lens communication performed as steps S 101 , S 117  and S 119  will be hereinafter discussed in detail with reference to the flow chart shown in  FIG. 6  and the timing charts shown in  FIGS. 8A through 11 . 
         [0064]    In the lens communication process, firstly the camera body  10  carries out a fixed data communication (lens ROM communication) with the interchangeable lens  50  mounted to the camera body  10  to read the lens data from the EEPROM  55  which corresponds to the distance code and the zoom code (step S 201 ). 
         [0065]    Subsequently, it is determined whether or not new communication can be carried out between the camera body  10  and the interchangeable lens  50  (step S 203 ). If the new communication cannot be carried out, control returns. If the interchangeable lens  50  is of a type which allows the camera body  10  to carry out the new communication with the interchangeable lens  50 , the following additional three communications become available: lens CPU communication that is performed between the camera CPU  11  and the lens CPU  51 , EEPROM communication that is performed between the camera CPU  11  and the EEPROM  55 , and the aforementioned code-plate-information communication via which the camera CPU  11  receives information on the code plate of the distance code output device  61 . If the new communication can be carried out between the camera body  10  and the interchangeable lens  50  (if YES at step S 203 ), it is determined which of the aforementioned three communications (lens CPU communication, EEPROM communication and code-plate-information communication) is to be utilized as a means of communication (step S 205 ). Subsequently, according to the type of communication utilized, the communication processes described below are selectively performed. The lens CPU communication, the EEPROM communication and the code-plate-information communication are performed according to the processes at steps S 117 , S 119  and S 105  (shown in  FIG. 4 ). 
       [Lens CPU Communication] 
       [0066]    Operations performed when it is determined at step S 205  that the type of communication to be utilized is the lens CPU communication will be hereinafter discussed with reference to the timing chart shown in  FIG. 9A .  FIG. 9A  shows a timing chart for communications between the camera body  10  and the lens interface IC  57 . In the lens CPU communication, a reset/set terminal RESL (see  FIG. 1 ) is first set to a low level before being subsequently set to a high level in order to initialize high/low settings of the lens interface IC  57  (step S 211 ). Thereafter, a CPU command is sent to the lens interface IC  57  from a serial I/O terminal SIOL (see  FIG. 1 ) in synchronization with a serial clock signal output from a clock terminal SCKL (see  FIG. 1 ) (step S 213 ), and subsequently, a CPU communication is performed to send and receive data corresponding to the aforementioned CPU command to and from the lens interface IC  57  (step S 215 ), and control returns. 
         [0067]    The CPU command output at step S 213  is composed of two bytes, and the lens CPU  51  interprets the two bytes of information (which is input from the time the level of the reset/set terminal RESL rises to a high level after falling to a low level) as a command, and interprets bytes of information subsequent to the two bytes as data. The number of bytes of the received data is predetermined by this command. The data input/output direction is determined by the least significant bit (LSB) in the second byte of the CPU command. The data input/output direction is the direction from the camera body  10  to the interchangeable lens  50  if the least significant bit (LSB) is “0” and the direction from the interchangeable lens  50  to the camera body  10  if the least significant bit (LSB) is “1”.  FIGS. 9B and 9C  are timing charts for communications between the lens CPU  51  and the lens interface IC  57 , wherein  FIG. 9B  shows the timing when the lens CPU  51  inputs data from the camera CPU  51  via the lens interface IC  57 , and  FIG. 9C  shows the timing when the lens CPU  51  outputs data to the camera CPU  11  via the lens interface IC  57 . 
       [EEPROM Communication] 
       [0068]    Operations performed when it is determined at step S 205  that the type of communication to be utilized is the EEPROM communication will be hereinafter discussed with reference to the timing charts shown in  FIGS. 12A through 12C . In the EEPROM communication, the reset/set terminal RESL is first set to a low level before being subsequently set to a high level to initialize high/low settings of the lens interface IC  57  (step S 221 ). 
         [0069]    Subsequently, an EEPROM command is sent to the lens interface IC  57  to switch connections of terminals thereof for communication to the EEPROM  55  (step S 223 ). This switching brings the camera CPU  11  into a state (EEPROM communication state) where the camera CPU  11  can carry out communications directly with the EEPROM  55 . 
         [0070]    Subsequently, the reset/set terminal RESL is set to a low level (step S 225 ), an EEPROM communication is performed (step S 227 ), and control returns. In the EEPROM communication, the camera CPU  11  directly performs the read/write control of the EEPROM  55  and can read from and write into the EEPROM  55  via addressing by the camera CPU  11 . 
         [0071]    In the EEPROM communication, when writing data into the EEPROM  55 , the camera CPU  11  firstly outputs a write-enable signal (see  FIG. 12A ). Subsequently, the camera CPU  11  outputs a write command, a high-order write address, a low-order write address and write data, and thereafter raises the level of the reset/set terminal RESL to a high level (see  FIG. 12B ). The sequence of these operations makes direct writing of data associated with high and low addresses of the EEPROM  55  into the EEPROM  55  possible. 
         [0072]    In the EEPROM communication, the camera CPU  11  does not need to output the write-enable signal when reading data in from the EEPROM  55 . After entering the state of the EEPROM communication, the camera CPU  11  outputs a read command, a high-order read address and a low-order read address, and thereafter the camera CPU  11  can receive data in synchronization with a serial clock signal. Upon completion of the communication, the camera CPU  11  raises the level of the reset/set terminal RESL to a high level (see  FIG. 12C ). The sequence of these operations allows direct reading of data associated with high and low addresses of the EEPROM  55  from the EEPROM  55 . 
         [0073]    These sequences for read/write control of the EEPROM  55  conform to the SPI communication mode. 
       [Code-Plate-Information Communication] 
       [0074]    Operations performed when it is determined at step S 205  that the type of communication to be utilized is the code-plate-information communication will be hereinafter discussed with reference to the timing chart and the diagram shown in  FIGS. 11A and 11B , respectively.  FIG. 11A  is a timing chart for the code-plate-information communication and  FIG. 11B  is a data mapping table. In the code-plate-information communication, the reset/set terminal RESL is first set to a low level before being subsequently set to a high level to initialize high/low settings of the lens interface IC  57  (step S 231 ), and subsequently, a code-plate-information read command is sent to the lens interface IC  57  to enable the camera CPU  11  to read information on the code plate of the distance code output device  61  (step S 233 ). Subsequently, after the reset/set terminal RESL is set to a low level (step S 235 ), the camera CPU  11  outputs a serial clock signal to receive information on the code plate, and control returns upon receiving information on the code plate (step S 237 ). In the code-plate-information communication, the camera CPU  11  inputs the levels of the memory capacity set-pin EEP, the distance-code input pins DC 0  through DC 2 , the versatile-code input pins GP 0  through GP 3  and the zoom-code input pins ZC 0  through ZC 0  through ZC 7 . The contents of the levels of these pins are as shown in  FIG. 11B ; data on the first byte is received as data on the capacity of the EEPROM  55 , distance-codes and versatile-code signals, and data on the second byte is received as data on zoom information. 
       [Extended Lens Communication] 
       [0075]    The extended lens communication that is performed at step S 105  will be discussed in detail with reference to the flow chart shown in  FIG. 6 . The extended lens communication is a communication process performed by a protocol equivalent to the protocol used for the EEPROM communication. The common-data extension mode in the extended lens communication is carried out by sequentially reading a prescribed number of bytes from the end address of the EEPROM  55 . The number of bytes is controlled on the camera body  10  side according to the ROM version (data on FCh and FDh) (see  FIG. 2B ). The remaining mode in the extended lens communication, i.e., the indexed addressing mode will be discussed hereinafter. 
         [0076]    In the extended communication mode, firstly the camera body  10  carries out the code-plate-information communication (see steps  231  through S 237  in  FIG. 5 ;  FIGS. 11A and 11B ) with the interchangeable lens  50  (the lens interface IC  57 ) to read data on the memory capacity set-pin EEP to determine whether or not the capacity of the EEPROM  55  is equal to or smaller than 4 kilobits or is equal to or greater than 8 kilobits (step S 301 ). 
         [0077]    Subsequently, the EEPROM communication is carried out to read data in the indexed portion of the EEPROM  55  (step S 303 ). In the present embodiment, 4 bytes from the end address in the EEPROM  55  are fixed as index data (see  FIG. 3B ). This index data can be read in by the memory capacity set-pin EEP regardless of the actual capacity of the EEPROM  55  by addressing the end address as FFFFh (if the capacity of the EEPROM  55  is equal to or greater than 8 kilobits) or 1 FFh (if the capacity of the EEPROM  55  is equal to or smaller than 4 kilobits). Communication with the EEPROM  55  is performed by the algorithm at steps S 221  through S 227  and the sequence according to the timing charts shown in  FIGS. 12A ,  12 B and  12 C. 
         [0078]    The camera CPU  11  analyzes the read data in the indexed portion to calculate the address and the capacity of extended data (step S 305 ). Subsequently, the code-plate-information communication is again performed to obtain the distance code detected by the distance code output device  61  and the zoom code detected by the zoom code output device  63  (step S 307 ). The extended data is read from the address corresponding to the distance code and the zoom code which are obtained at step S 307  (step S 309 ), and control returns. 
       [LROM Communication Process in the Interchangeable Lens] 
       [0079]    The LROM communication process that is performed in the interchangeable lens  50  will be hereinafter discussed in detail with reference to the flow chart shown in  FIG. 7  and the timing charts and the table shown in  FIGS. 10A ,  10 B and  10 C.  FIG. 10A  is a timing chart on the camera body  10  side (timing chart for communications between the camera body  10  and the lens interface IC  57 ),  FIG. 10B  is a timing chart on the interchangeable lens  50  side (timing chart for communications between the lens interface IC  57  and the EEPROM  55 ), and  FIG. 10C  is a data mapping table showing the correspondence between data. 
         [0080]    Upon the reset/set terminal RESL falling to a low level, the level of a terminal CSEE is dropped to a low level, and three bytes of set-pin data SP 0  through SP 2  are output in the communication for the first three bytes in synchronization with a clock signal output from the clock terminal SCKL. The set-pin data SP 0  through SP 2  are set by the lens type set-pins (first group of set-pins) LT 1  and LT 2 , lens capability set-pins (second group of set-pins) LD 0  through LD 7  and shortest object distance set-pins (third group of set-pins) ND 0  through ND 4  that show the shortest object distance, and the level of each set-pin is sequentially read and physically decoded by the lens interface IC  57  to be output therefrom. An example of the contents thereof is as shown in a data table of  FIG. 10C . The lens type set-pins LT 1  and LT 2  provide lens type set-pin LT information for setting a lens type; the lens capability set-pins LD 0  through LD 7  provide lens capability set-pin LD information for setting capabilities of the interchangeable lens  50  such as AF, AF direction, macro and light projection; and shortest object distance set-pins ND 0  through ND 4  provide shortest object distance set-pin ND information which shows the shortest object distance. 
         [0081]    Page data of the EEPROM  55  which is addressed by the zoom-code input pins ZC 0  through ZC 7  is read out by a communication of 16 bytes from the fourth byte onwards. The lens interface IC  57  outputs the clock signal input from the clock terminal SCKL to a terminal SCKEE, outputs a read command and address data to a terminal SIEE, and reads data which is output from a terminal SOEE. This read data is sent (transferred) to the camera CPU  11  via the serial I/O terminal SIOL. 
         [0082]    The LROM communication process in the interchangeable lens  50  will be hereinafter discussed with reference to the flow chart shown in  FIG. 7  and the timing charts shown in  FIGS. 10A and 10B .  FIG. 7  is a flowchart showing a sequence of operations in the lens interface IC  57  with respect to the LROM communication. However, the lens interface IC  57  in the present embodiment is a logic IC, and the process shown in  FIG. 7  is physically processed. The lens interface IC  57  performs the LROM communication according to (in synchronization with) a serial clock signal that the camera CPU  11  outputs to the clock terminal SCKL with the reset/set terminal RESL being set at a low level. 
         [0083]    In the LROM communication process, firstly it is determined whether or not the level of the reset/set terminal RESL has fallen to a low level (step S 401 ). Namely, the lens interface IC  57  waits for the level of the reset/set terminal RESL to fall to a low level at step S 401 . Upon the level of the reset/set terminal RESL falling to a low level (if YES at step S 401 ), the lens interface IC  57  reads in zoom code (the levels of the input pins ZC 0  through ZC 7 ) and converts the zoom code into address data for the EEPROM  55  (step S 403 ). 
         [0084]    The lens interface IC  57  reads the level of the memory capacity set-pin EEP to determine the high/low state thereof (step S 405 ). The memory capacity set-pin EEP is set at a low level if the memory capacity is equal to or smaller than 4 kilobits and to a high level if the memory capacity is equal to or greater than 8 kilobits. 
         [0085]    If the level of the memory capacity set-pin EEP is a low level (if Low at step S 405 ), in the communication for the first byte, the lens interface IC  57  does nothing to the EEPROM  55  and sends the lens type set-pin LT information to the camera CPU  11  (step S 411 ). In the communication for the second byte, the lens interface IC  57  sends a read command to the EEPROM  55  and sends the lens capability set-pin LD information to the camera CPU  11  (step S 413 ). In the communication for the third byte, the lens interface IC  57  sends the EEPROM  55  the address of 1 byte that the lens interface IC  57  has converted from the read zoom code, and sends the shortest object distance set-pin ND information to the camera CPU  11  (step S 415 ). Thereafter, in the communication for the fourth byte to the nineteenth byte, the lens interface IC  57  receives data of the EEPROM  55  sequentially from the address thereof which the lens interface IC  57  has sent to the EEPROM  55  at step S 415 , and sends (transfers) the data thus received to the camera CPU  11  (step S 431 ). Thereafter, it is determined whether or not the level of the reset/set terminal RESL has risen to a high level (step S 433 ). Namely, the lens interface IC  57  waits for the level of the reset/set terminal RESL to rise to a high level at step S 433 . Upon the level of the reset/set terminal RESL rising to a high level (if YES at step S 433 ), the lens interface IC  57  ends the LROM communication process. 
         [0086]    If the level of the memory capacity set-pin EEP is a high level (if High at step S 405 ), in the communication for the first byte the lens interface IC  57  sends a read command to the EEPROM  55  and sends the lens type set-pin LT information to the camera CPU  11  (step S 421 ). In the communication for the second byte, the lens interface IC  57  sends the EEPROM  55  a high-order address_H among the address data that the lens interface IC  57  has converted from the read zoom code at step S 403  (step S 423 ). In the communication for the third byte, the lens interface IC  57  sends the EEPROM  55  a low-order address_L among the address data that the lens interface IC  57  has converted from the read zoom code at step S 403  (step S 423 ) and sends the shortest object distance set-pin ND information to the camera CPU  11  (step S 425 ). Thereafter, in the communication for the fourth byte to the nineteenth byte, the lens interface IC  57  receives data of the EEPROM  55  sequentially from the addresses thereof designated by the high-order address_H and the low-order address_L that the lens interface IC  57  has sent to the EEPROM  55  at steps S 423  and  425 , respectively, and sends the data thus received to the camera CPU  11  (step S 431 ). Upon completion of the transmission of this data to the camera CPU  11 , the lens interface IC  57  waits for the level of the reset/set terminal RESL to rise to a high level at step S 433 . Upon the level of the reset/set terminal RESL rising to a high level (if YES at step S 433 ), the lens interface IC  57  ends the LROM communication process. 
         [0087]    According to the above described embodiment of the interchangeable lens, a new interchangeable lens is achieved which can incorporate a memory having an appropriate memory capacity as necessary even if the required capacity of lens data varies depending on the type of new interchangeable lens, and which is compatible with the known memory management in the camera body even if the number of bytes for addressing varies according to the capacity of the incorporated memory. Moreover, a lens data communication method is achieved by which a new interchangeable lens can incorporate a memory having an appropriate memory capacity as necessary even if the required capacity of lens data varies depending on the type of new interchangeable lens, and by which the interchangeable lens is compatible with the known memory management in the camera body even if the number of bytes for addressing varies according to the capacity of the incorporated memory. 
         [0088]    Obvious changes may be made in the specific embodiment of the present invention described herein, such modifications being within the spirit and scope of the invention claimed. It is indicated that all matter contained herein is illustrative and does not limit the scope of the present invention.