Patent Publication Number: US-7711260-B2

Title: Digital camera and camera system

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2006-136668, filed on May 16, 2006, the entire contents of which are incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a digital camera and a camera system having an automatic focusing (AF) control function. 
   2. Description of the Related Art 
   Heretofore, as an AF mechanism disposed in a single-lens reflex camera using a film and a single-lens reflex digital camera, a through-the-lens (TTL) phase-difference AF mechanism has been frequently used. In this case, a defocus detection mechanism which performs the TTL phase-difference AF is disposed in a main body of the single-lens reflex camera. Moreover, a focusing lens disposed in a lens barrel of an interchangeable lens which is detachably attached to the single-lens reflex cameras is driven by a motor disposed in the lens barrel of the interchangeable lens or the main body of the single-lens reflex camera to perform a focusing control operation. It is to be noted that the TTL phase-difference AF is sometimes referred to simply as the phase-difference AF. 
   On the other hand, in a compact digital camera, a camcorder or the like, so-called imager AF is frequently performed which is AF of such a system that contrast is detected with a high frequency component of a signal of an image pickup device. Here, the imager AF is an auto focusing method where an evaluated focal value of a focus lens at each focus lens position is calculated while moving the focus lens at a predetermined driving amount interval, and the focus lens position where the evaluated focal value reaches a peak value is obtained. 
   It is to be noted that the TTL phase-difference AF and the imager AF have the following characteristics, respectively. 
   The TTL phase-difference AF is the AF at a speed higher than that of the imager AF. 
   The imager AF is the AF having a precision higher than that of the TTL phase-difference AF. 
   Based on such characteristics, the TTL phase-difference AF and the imager AF are selectively used in accordance with an application. Here, as a technology in selectively using the TTL phase-difference AF and the imager AF, for example, the following technology is known. 
   In Japanese Patent Application Laid-Open No. 7-43605, an automatic focusing device is disclosed in which the TTL phase-difference AF is combined with the imager AF to perform focusing control. Specifically, in this automatic focusing device, after coarse control is performed by the TTL phase-difference AF, fine control is performed by the imager AF. 
   Moreover, in Japanese Patent Application Laid-Open No. 2003-302571, an automatic focusing control device is also disclosed in which after the coarse control is performed by the TTL phase-difference AF, the fine control is performed by the imager AF in the same manner as in the automatic focusing device disclosed in Japanese Patent Application Laid-Open No. 7-43605. However, in this automatic focusing control device disclosed in Japanese Patent Application Laid-Open No. 2003-302571, to speed us the focusing, the TTL phase-difference AF is selected in preference to the imager AF, when it is decided that the focusing is possible with the TTL phase-difference AF alone. 
   In addition, for a lens-interchangeable single-lens reflex camera using a film, many interchangeable lenses are on sale and already spread widely. Here, many of the interchangeable lenses which have already spread are designed to perform the TTL phase-difference AF. That is, focusing control mechanisms and the like of the focus lenses disposed in the lens barrels of many interchangeable lenses are designed as a system which drives the lens by a driving amount corresponding to a detected defocus amount. Specifically, as a driving source for the focusing control in the interchangeable lens barrel, a direct-current motor (a DC motor) is employed in many cases. On the other hand, as the driving source of the focus lens in the imager AF, a stepping motor is optimum. In actual, stepping motors are employed in many cases of the imager AF. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention relates to detecting a focus of a lens unit by a method selected from a plurality of focus detection methods based on information on the lens unit taken into a digital camera from the lens unit, which is attached to the digital camera. 
   Next, one example of a structure of the present invention will be described. A digital camera to which a lens unit having a focus lens as a shooting optical system is detachably attached, comprising: an imaging section having an image pickup device to convert an optical image of a subject which has struck via the lens unit into an electrical signal; a first focus detecting section which detects focal information of the focus lens by a first focus detection method; a second focus detecting section which detects focal information of the focus lens by a second focus detection method; a control section which selects the focal information detected by at least one of the first focus detecting section and the second focus detecting section and which generates a focusing control signal to control a focal position of the focus lens based on the selected focal information; and a transmitting and receiving section which transmits the focusing control signal to the lens unit and which receives information on the lens unit transmitted from the lens unit, wherein the control section selects the focal information based on the information on the lens unit acquired via the transmitting and receiving section. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     These and other features, aspects, and advantages of the apparatus and methods of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings where: 
       FIG. 1  is a diagram showing a system structure of a digital camera according to a first embodiment of the present invention; 
       FIG. 2  is a diagram showing an internal structure of a second focus detecting section; 
       FIG. 3  is a graph of an evaluated AF value to a focus lens position; 
       FIG. 4  is a diagram showing a structure of a phase-difference AF sensor unit; 
       FIG. 5  is a diagram showing a concept to calculate a phase difference which is a relative positional relation between two subject images; 
       FIG. 6  is a diagram mainly showing a component concerning TTL phase-difference AF in the digital camera according to a first embodiment of the present invention; 
       FIG. 7  is a graph showing one example of a relation between i and F(i); 
       FIG. 8  is a flow chart showing operation control performed by a control section of the digital camera according to the first embodiment of the present invention; 
       FIG. 9  is a diagram showing a lens type correspondence table; 
       FIG. 10  is a flow chart showing operation control of imager AF performed by the control section of the digital camera according to the first embodiment of the present invention; 
       FIG. 11  is a flow chart showing operation control performed by a lens control section of the digital camera according to the first embodiment of the present invention; 
       FIG. 12  is a timing chart showing a timing of the operation control performed by the imager AF; 
       FIG. 13  is a flow chart showing the operation control performed by the control section of the digital camera according to a second embodiment of the present invention; 
       FIG. 14  is a flow chart showing the operation control performed by the control section of the digital camera according to a third embodiment of the present invention; 
       FIG. 15  is a diagram showing driving source data for judgment of a driving source; and 
       FIG. 16  is a flow chart showing the operation control performed by the control section of the digital camera according to a fourth embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Preferred embodiments of the invention are described below with reference to the accompanying drawings. 
   First Embodiment 
   A digital camera and a camera system according to a first embodiment of the present invention will hereinafter be described with reference to the drawings.  FIG. 1  is a diagram showing a system structure of the digital camera according to the first embodiment of the present invention. It is to be noted that in the first embodiment, a single-lens reflex digital camera is assumed as the digital camera and described. 
   First, in  FIG. 1 , reference numeral  1  is a camera body. Reference numeral  2  is an interchangeable lens as a lens unit. 
   Here, the interchangeable lens  2  has a photographing lens system  3 , a lens driving section  4 , a lens control section  5 , an encoder  15  and a storage section  5 A. 
   The photographing lens system  3  includes a focus lens  3 A. Moreover, during focusing control, the focus lens  3 A is moved to control a focus. The lens driving section  4  is a section which moves the focus lens  3 A in an optical axis direction. The lens control section  5  is a communicating section which communicates with the camera body  1  as well as a control section which controls the lens driving section  4 . The encoder  15  is an encoder which generates a pulse signal in response to movement of the focus lens  3 A and which outputs the pulse signal to the lens control section  5 . Information including a lens type and a characteristic of the lens. 
   It is to be noted that the lens control section  5  counts output pulses of the encoder  15  to recognize a position of the focus lens  3 A. 
   On the other hand, the camera body  1  has a half mirror  6 , an image pickup device (imaging section)  7 , a phase-difference AF sensor unit  9 , an LCD panel  10 , a finder optical system  11 , a first focus detecting section  12 , an image processing section  13 , a second focus detecting section  14 , a control section  16  and a release switch  18 . 
   The half mirror  6  is a member which divides a shot luminous flux into a luminous flux to the image pickup device  7  and a luminous flux to the phase-difference AF sensor unit  9 . According to such a structure, an image pickup operation and an operation for phase-difference AF can simultaneously be performed. The LCD panel  10  is an LCD panel for an electronic view finder in which a backlight is incorporated. The finder optical system  11  is a member for a user to observe the LCD panel  10 . The first focus detecting section  12  is a member which calculates a defocus amount or the like from an output of the phase-difference AF sensor unit  9 . 
   The image processing section  13  subjects a picture signal output from the image pickup device  7  to white balance adjustment, luminance processing, color matrix processing and the like, and forms image data as a shot image and image data for a finder. in addition to the formation of the image data, the image processing section  13  acquires processes a signal output from the image pickup device  7  to acquire image information. 
   The image data for the finder formed by the image processing section  13  is sent to the LCD panel  10 , and displayed in the LCD panel  10 . Moreover, the image data for the finder is observed by the user via the finder optical system  11 . The image data as the shot image is stored in a nonvolatile memory (not shown) or the like. 
   Furthermore, the image processing section  13  generates a driving control signal of the image pickup device  7  based on a reference clock (not shown) sent from the control section  16  described later. Specifically, the image processing section  13  generates a timing signal of start/end (start/end of exposure) of integration of the image pickup device  7  and a clock signal such as a readout control signal (a horizontal sync signal, a vertical sync signal VD, a transfer signal or the like) of a light receiving signal of each pixel and the like, and outputs the signals to the image pickup device  7 . 
   Here, the image processing section  13  outputs the vertical sync signal VD to the second focus detecting section  14 , the control section  16  and the lens control section  5 . It is to be noted that a signal VDP which agrees with the vertical sync signal VD is output to the lens control section  5  via a lens contact section (a transmitting and receiving section)  8 . The lens contact section  8  is a lens contact to which the control section  16  disposed in the camera body  1 , a communication line with the lens control section  5  disposed in the interchangeable lens  2  and the like are connected. It is to be noted that the lens contact section  8  has a plurality of contacts required for connection of a plurality of power sources including a lens power source to be supplied from the camera body  1  to the interchangeable lens  2  and transmission of a plurality of signals including the vertical sync signal. 
   The second focus detecting section  14  is a member which judges a magnitude of change of a luminance signal obtained from the image processing section  13  to calculate an evaluated AF value indicating a degree of focusing. It is to be noted that a focus detection area which is an area to calculate the evaluated AF value is predetermined as a region which agrees with the focus detection area during the phase difference detection. The control section  16  is a member which controls the whole camera body  1  and interchangeable lens  2 . 
   It is to be noted that in the camera according to the first embodiment, a release button (not shown) is a two-stage type button to be pressed. When the button is pressed halfway, a first release switch (hereinafter referred to as 1RSW) is turned on, and a focus detecting operation is performed described later. When the release button (not shown) is fully pressed, a second release switch (hereinafter referred to as 2RSW) is turned on, and a shooting operation is performed as described later. Here, the 1RSW corresponds to the release switch  18 . 
   First, imager AF (AF using a focus detection method performed by a contrast system) will be described with reference to  FIGS. 2 and 3 . 
   First, as shown in  FIG. 2 , in the second focus detecting section  14 , a high pass filter (HPF)  131 , an A/D converter  132 , a focus detection area selection gate  133  and an adder  134  are connected in this order. Here, each section component member disposed in the second focus detecting section  14  is a circuit block to obtain the evaluated AF value. 
   The image processing section  13  inputs the luminance signal generated from an output signal of the image pickup device  7  into the HPF  131  of the second focus detecting section  14 . Moreover, this luminance signal is processed as follows in the image processing section  13 . 
   First, high frequency components included in the luminance signal are extracted from the luminance signal by the HPF  131 . When sharpness of an image is high, a larger amount of the extracted high frequency components are extracted. Therefore, the high frequency components of a predetermined image range can be integrated to obtain a numeric value of an average degree of the image sharpness in the image range. 
   Next, the high frequency component passed through the HPF  131  is converted into a digital signal by the A/D converter  132 , and input into the focus detection area selection gate  133 . This focus detection area selection gate  133  is a circuit which extracts only signals corresponding to a plurality of focus detection areas of an imaging screen. Therefore, the focus detection area selection gate  133  extracts only information on a subject, reflected in the focus detection area corresponds to the predetermined image range for the integration. 
   Here, as the focus detection area, a focus detection area selected based on a predetermined selection algorithm (e.g., a closest selection algorithm) may be employed. Needless to say, a focus detection area selected from the plurality of focus detection areas by the user may be employed. 
   Moreover, the digital signal extracted by the focus detection area selection gate  133  is input into the adder  134 . Furthermore, the digital signals of a portion of the focus detection area of one frame are integrated. It is to be noted that a value integrated by this adder  134  is input as the evaluated AF value indicating the sharpness of the image into the control section  16 . The control section  16  can perform the imager AF which is auto focusing of a known mountain climbing system by use of the evaluated AF value calculated as described above. 
   It is to be noted that the image processing section  13  outputs the luminance signal to the second focus detecting section  14 , and outputs the sync signal to the focus detection area selection gate  133 , the adder  134  and the control section  16  in response to the picture signal. 
   Here, to perform the imager AF, the control section  16  moves the focus lens  3 A by the lens driving section  4  via the lens control section  5 . Moreover, position information of the focus lens  3 A from an output of the encoder  15 . Furthermore, the evaluated AF value is input from the adder  134 . As shown in  FIG. 3 , the evaluated AF value of the position of the focus lens  3 A is obtained as evaluated AF coordinate values ((P 1 , H 1 ), (P 2 , H 2 ) and (P 3 , H 3 ). 
   Moreover, the control section  16  calculates a lens position of the focus lens  3 A at a time when the evaluated AF value reaches a maximum value, that is, a peak value by interpolation using the above evaluated AF coordinate value. Subsequently, the focus lens  3 A is moved to a focus target position PM which is the lens position at the time when the evaluated AF value reaches the peak value. 
   Next, TTL phase-difference AF will be described. 
   First, as shown by a broken line of  FIG. 4 , the phase-difference AF sensor unit  9  has a view field mask  101 , a condenser lens  102 , aperture masks  103 A and  103 B, secondary optical systems  104 A and  104 B and photoelectric conversion element rows  105 A and  105 B. 
   As shown in  FIG. 4 , the view field mask  101  is disposed in the vicinity of a scheduled imaging surface on which a subject image is formed by the photographing lens system  3 . Furthermore, the condenser lens  102  is disposed in the vicinity of the view field mask  101 . In addition, the aperture masks  103 A and  103 B are aperture masks with openings, and arranged behind the condenser lens  102  along an optical path of the condenser lens. Moreover, the secondary optical systems  104 A and  104 B include secondary imaging lenses, and arranged behind the aperture masks  103 A and  103 B along the optical path. The photoelectric conversion element rows  105 A and  105 B are arranged behind the secondary imaging lenses along the optical path. It is to be noted that, as shown in  FIG. 4 , the photographing lens system  3  can define two different pupil areas  106 A and  106 B. 
   According to such a structure, two subject images formed by the luminous fluxes passed through the pupil areas  106 A and  106 B of the photographing lens system  3  are formed on the photoelectric conversion element rows  105 A and  105 B, respectively. The focus is detected using a fact that a relative positional relation between two subject images formed again in this manner changes with a focused state of the photographing lens system  3 . It is to be noted that a phase difference which is this relative positional relation between the two subject images can be calculated by obtaining correlation between the positions. A concept of this calculation will hereinafter be described with reference to  FIG. 5 . 
   That is, an area S (a sum of absolute values of differences of outputs between the corresponding pixels of images A and B) of a region where two subject images (the images A and B) are not superimposed on each other is assumed as hatched in  FIG. 5 . Moreover, one image (the image A of the present example) is shifted every pixel (one bit) of the photoelectric conversion element to obtain a minimum value of the area S. 
   Here, when the image A agrees with the image B, the area S naturally has the minimum value. Moreover, a defocus amount of one image (the image A of the present example) required for bringing about this minimum value is the phase difference which is a relative defocus amount. As described above, assuming that an interval between gravity centers of the two pupil areas  106 A and  106 B is a base line length during triangle measurement, a defocus amount of the photographing lens system  3  can be obtained based on the phase difference which is the relative defocus amount along the photoelectric conversion element rows  105 A and  105 B. 
     FIG. 6  is a drawing mainly showing an extracted component concerning the TTL phase-difference AF in the digital camera according to the first embodiment. Here, the photoelectric conversion element rows  105 A and  105 B are included in the phase-difference AF sensor unit  9 . An A/D converter  111  is included in the first focus detecting section  12 . Analog outputs from the pixels of the photoelectric conversion element rows  105 A and  105 B are converted into digital signals by the A/D converter  111 . Furthermore, a calculation processing section  112  such as a microcomputer is incorporated in the first focus detecting section  12 . According to the above structure, the phase difference between the two images (the images A and B) is obtained, and the focus lens  3 A is controlled based on this phase difference. This will hereinafter be described specifically. 
   First, it is assumed that output values of the photoelectric conversion element row  105 A which have been A/D converted by the A/D converter  111  are L( 1 ), L( 2 ), . . . , L(n) and that output values of the photoelectric conversion element row  105 B which have been A/D converted by the A/D converter  111  are R( 1 ), R( 2 ), . . . , R(n). Here, 1 to n correspond to the photoelectric conversion elements, and are represented by variables i. 
   Here, a correlation function F(i) indicating an agreement degree of the image with respect to the relative defocus amount (the phase difference) of two images represented by the phase difference=i·p (p is a pixel pitch) is given by, for example, Equation (1). 
   
     
       
         
           
             
               
                 
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   If two images of the photoelectric conversion element rows  105 A and  105 B relatively defocus at a pitch of k pixels, F(k)=0 results from Equation (1). However, owing to an influence of a pixel noise or the like, a form of an image signal of the photoelectric conversion element row  105 A is not completely the same as that of an image signal of the photoelectric conversion element row  105 B. Therefore, F(k)&gt;0 usually results. 
     FIG. 7  shows one example of the above relation between i and F(i). As described above, (i, F(i)) is actually discrete data, but  FIG. 7  shows a continuous graph for the sake of convenience. It is to be noted that after obtaining the minimum value of F(i) in a predetermined range of i, the interpolation is performed using correlation function values before and after the minimum value in order to perform highly precise detection. 
   The operation control performed by the control section  16  of the digital camera according to the first embodiment will hereinafter be described with reference to a flow chart of  FIG. 8 . 
   First, when the user turns on the power source (not shown) disposed in the camera body  1 , the control section  16  of the camera body  1  communicates with the lens control section  5  of the interchangeable lens  2  (step S 100 ). Specifically, in this step S 100 , the control section  16  reads out various data concerning this lens stored in the storage section  5 A of the interchangeable lens  2 , and stores the data in a storage section (not shown) of the control section  16 . 
   It is to be noted that communication between the control section  16  of the camera body  1  and the lens control section  5  of the interchangeable lens  2  will hereinafter be referred to as body and lens communication. Examples of the data concerning the interchangeable lens  2  to be communicated during this body and lens communication include information such as the lens type of the interchangeable lens  2 , a focal length, a shootable distance, a movable range of the focus lens, the total number of focus pulses corresponding to the whole region of a shooting distance, a motor type and various corrected values concerning the AF. 
   Subsequently, the user half presses the release button to wait until the release switch  18  (the  1 RSW) is turned on (step S 101 ). Moreover, when the  1 RSW is turned on, the step S 101  is branched to YES to start a focusing operation by the auto focusing. 
   First, the lens type of the interchangeable lens  2  is judged (step S 102 ). Specifically, during the judgment of the lens type in this step S 102 , with reference to the lens type data acquired by the body and lens communication in the step S 100 , the lens type of the interchangeable lens  2  is judged based on a lens type correspondence table shown in  FIG. 9 . Here, the lens type correspondence table is a table in which three lens type data ( 0 ,  1  and  2 ) are associated with AF aptitudes of the lens type data. 
   It is to be noted that the lens type  0  indicates that the interchangeable lens deals with the only phase-difference AF. The lens type  1  indicates that the interchangeable lens deals with the only imager AF. Furthermore, the lens type  2  indicates that the interchangeable lens deals with both of the phase-difference AF and the imager AF. 
   After ending the processing of the step S 102 , it is judged whether or not the lens type of the interchangeable lens  2  is the lens type  1  (step S 103 ). In a case where it is judged in the step S 103  that the interchangeable lens  2  is the lens type  1 , the processing shifts to the step S 110  described later. On the other hand, in a case where it is judged in the step S 103  that the interchangeable lens  2  is not the lens type  1 , it is judged whether or not the interchangeable lens  2  is the lens type  0  (step S 104 ). In a case where it is judged in this step S 104  that the interchangeable lens  2  is the lens type  0 , the processing shifts to step S 115  described later. 
   In a case where it is judged in the step S 104  that the interchangeable lens  2  is not the lens type  0  (in a case where the interchangeable lens  2  is the lens type  2 ), the phase difference is detected (step S 105 ). During the detection of the phase difference in this step S 105 , the first focus detecting section  12  acquires a signal from the phase-difference AF sensor unit  9 , and calculates the defocus amount. In the step S 105 , it is evaluated whether or not the phase difference can be detected, and reliability of the phase difference detection is also calculated. 
   Subsequently, it is judged whether or not a highly reliable defocus amount has been obtained during the phase difference detection in the step S 105 . In other words, it is judged whether or not the phase difference can be detected (step S 106 ). In a case where it is judged in this step S 106  that the phase difference can be detected, it is judged whether or not the defocus amount detected in the step S 105  is in a predetermined range described later (step S 107 ). It is to be noted that this predetermined range is a range predetermined by assuming that the focusing operation can be performed sufficiently highly precisely at a high speed by the imager AF in a case where the defocus amount is in the above range. 
   In a case where it is judged in the step S 107  that the defocus amount is in the predetermined range, an in-range flag indicating this effect is set (step S 130 ). Furthermore, the processing shifts to step S 110  described later. 
   In addition, in a case where it is judged in the step S 107  that the defocus amount is not in the above predetermined range, a lens driving amount and a driving direction of the focus lens  3 A required for obtaining the focused state are calculated from the obtained defocus amount (step S 108 ). Moreover, the focus lens  3 A is driven based on the lens driving amount and the driving direction calculated in the step S 108  (step S 109 ). 
   Specifically, in the step S 109 , the lens driving amount and the driving direction calculated in the step S 108  are transmitted as a phase-difference AF lens driving command to the lens control section  5  of the interchangeable lens  2  via the lens contact section  8 . Moreover, the lens control section  5  controls the lens driving section  4  to drive the focus lens  3 A. After ending the processing of the step S 109 , the processing returns to the step S 105 . In a case where conditions of the steps S 106  and S 107  are not satisfied in this manner, the focus of the focus lens  3 A is firstly coarsely adjusted by the phase-difference AF. Subsequently, the above conditions are checked again. 
   In addition, in a case where it is judged in the step S 106  that the phase difference cannot be detected, and after it is judged in the step S 107  that the defocus amount is in the predetermined range to end the processing of the step S 130 , the imager AF is executed (step S 110 ). Specific processing contents of this imager AF will be described later in detail with reference to a flow chart of  FIG. 10 . After ending the processing of the imager AF in the step S 119 , it is judged from the result of the imager AF whether or not the focused state has been obtained (step S 111 ). 
   In a case where it is judged in the step S 111  that the focused state can be obtained, focusing display indicating that the focused state has been obtained is displayed in the LCD panel  10  by the image processing section  13  (step S 112 ). On the other hand, in a case where it is judged in the step S 111  that the focused state is not obtained, the image processing section  13  displays, in the LCD panel  10 , that the focused state is not obtained (step S 113 ). 
   Moreover, after ending the processing of the step S 112  or the S 113 , the user fully presses the release button to instruct the shooting, and the shooting is performed based on a usual shooting sequence (step S 114 ). 
   After ending the processing of the step S 114 , the in-range flag is reset in a case where the in-range flag is set in the step S 139  (step S 131 ). Moreover, the step waits until the release switch  18 , that is, the  1 RSW turns off (step S 132 ). In a case where it is judged in this step S 132  that the  1 RSW turns off, the processing returns to the step S 101 . 
   In addition, in a case where it is judged in the step S 104  that the interchangeable lens  2  is the lens type  0 , the phase difference is detected (step S 115 ). Specifically, in this step S 115 , the defocus amount is calculated by the first focus detecting section  12  based on the signal output from the phase-difference AF sensor unit  9 . It is evaluated whether or not the phase difference can be detected, and the reliability of the detection is calculated. 
   Subsequently, it is judged whether or not the highly reliable defocus amount has been obtained during the phase difference detection of the step S 115  (step S 116 ). In a case where it is judged in this step S 116  that the phase difference can be detected, it is judged whether or not the detected current defocus amount is in a focused range (step S 117 ). Here, the focused range indicates a numeric value predetermined by assuming that the focused state is obtained in a case where the defocus amount is in this range. In a case where it is judged in this step S 117  that the current defocus amount is not in the focused range, the driving amount and the driving direction of the focus lens  3 A required for obtaining the focused state are calculated based on the defocus amount (step S 118 ). 
   Moreover, the focus lens  3 A is driven based on the driving amount and the driving direction of the focus lens  3 A calculated in the step S 118  (step S 119 ). Specifically, the lens driving amount and the driving direction calculated in the step S 118  are transmitted as the phase-difference AF lens driving command to the lens control section  5  of the interchangeable lens  2 . Moreover, the lens control section  5  controls the lens driving section  4  to drive the focus lens  3 A. Subsequently, the processing returns to the step S 115 . 
   In addition, in a case where it is judged in the step S 116  that the phase difference cannot be detected, the image processing section  13  displays, in the LCD panel  10 , that the focused state is not obtained (step S 121 ). In a case where it is judged in the step S 117  that the current defocus amount is in the focused range, the focused display indicating that the focused state is obtained is displayed in the LCD panel  10  by the image processing section  13  (step S 120 ). Moreover, after ending the processing of this step S 120  or S 121 , the processing shifts to the shooting sequence of the step S 114 . 
   As described above, in the digital camera according to the first embodiment, when the interchangeable lens  2  is the lens type  0 , the only phase-difference AF is executed. When the interchangeable lens  2  is the lens type  1 , the only imager AF is executed. Moreover, in a case where the interchangeable lens  2  is the lens type  2 , after coarsely adjusting the focusing control by the phase-difference AF, the focusing control is finely adjusted by the imager AF. 
   Here, a relation between the lens type of the interchangeable lens  2  and time required for the focusing control will be described. First, when the user performs the imager AF without feeling any incompatibility, the time required for the focusing control needs to be shortened to a certain degree (set to, e.g., one second or less). This is because, in a case where the time required for the focusing control is excessively long, a problem occurs that the opportunity to get the best shot is missed or that a camera user judges that the camera gets out of order. 
   Therefore, when the driving time of the focus lens  3 A is longer than a predetermined time, it is considered that the lens is not suitable for the imager AF in which the focus lens  3 A is scanned to search for the peak evaluated AF value while the evaluated AF value is acquired. The lens types are determined based on such consideration. 
   Specifically, it is assumed that the interchangeable lens having the focus lens driving time not less than the predetermined time at the whole shooting distance range of an infinitely far point to the closest point is the lens type  1  or  2  which is the lens suitable for the imager AF. Moreover, it is assumed that the interchangeable lens having the focus lens driving time not less than the predetermined time at the whole shooting distance range of the infinitely far point to the closest point is the lens type  0  as the lens which is not suitable for the imager AF. 
   Here, examples of the interchangeable lens which is the lens type  0  include a micro lens having a high shooting magnification of 1:1 macro or the like and a telephoto lens having a long focal length. Examples of the lens of the lens type  1  include a wide-angle lens having a short focal length. Examples of the lens of the lens type  2  include a standard lens having a medium focal length. 
   According to such classification of the lens type, in a case where, for example, the telephoto lens of the lens type  0  having the long focal length is used as the interchangeable lens  2 , since the interchangeable lens is not suitable for the imager AF as described above, the focusing control is performed by the only phase-difference AF. In a case where, for example, the wide-angle lens of the lens type  1  having the short focal length is used as the interchangeable lens  2 , when the focus lens is scanned over the whole shooting distance range by the imager AF, the driving can be completed in a sufficiently short time. Therefore, the focusing control is performed by the only highly precise imager AF. Furthermore, in a case where, for example, the standard lens of the lens type  2  having the intermediate focal length is used as the interchangeable lens  2 , since a long time is required for the focusing control by the only imager AF as compared with the lens type  1 , the coarse adjustment is performed by the phase-difference AF, and the fine adjustment is performed by the imager AF. In consequence, the time of the focusing control is compatible with the precision. 
   The focus detecting operation performed by the imager AF in the step S 110  will hereinafter be described with reference to a flow chart of  FIG. 10 . 
   First, it is judged whether or not the in-range flag has been set in the step S 130  (step S 200 ). Here, in a case where it is judged that the in-range flag has been set, a scan region of the imager AF is set (step S 201 ). Here, the scan region is set to ΔX before or after a current position of the focus lens  3 A which is regarded as the center position. This ΔX is the scan region predetermined so as to perform a sufficiently highly precise focusing operation at a high speed. The range is stored in the storage section  5 A of the interchangeable lens  2  and read out for use by the control section  16 . It is to be noted that the above ΔX is appropriately changed with a parameter such as the focal length of the interchangeable lens  2 , the position (a distance) of the focus lens  3 A or high reliability of the phase difference detection. 
   In a case where it is judged in the step S 200  that the in-range flag is not set, the scan region of the focus lens  3 A is set to the whole focus lens movable region, that is, a region from the closest point to the infinitely far point (step S 202 ). In the processing of this step S 202 , it is considered that there is a high possibility that the focus lens  3 A is not positioned in the vicinity of the focus because the phase difference cannot reliably be detected or the phase-difference AF is not executed in advance. 
   After transmitting the scan region set in the step S 201  or S 202  in this manner to the lens control section  5  by the body and lens communication, a predetermined command is transmitted to the lens control section  5  to control the lens driving section  4  via the lens control section  5 . In consequence, the focus lens  3 A is moved to an end of the scan region on a side close to the camera body  1  (step S 203 ). 
   Moreover, the lens driving command of the imager AF is transmitted to the lens control section  5  to start a scan operation of the focus lens  3 A (step S 204 ). Furthermore, the image processing section  13  exposes (EXP) the image pickup device  7  and reads out (READ) the image data at a predetermined timing after generation of the vertical sync signal VD. In addition, the evaluated AF value of the imager AF is calculated based on this read image data (step S 205 ). 
   Subsequently, the processing waits until the vertical sync signal VD from the image processing section  13  rises (step S 206 ). When the rising of the vertical sync signal VD is detected, the lens position of the focus lens  3 A transmitted from the lens control section  5  is received (step S 207 ). Moreover, the evaluated AF value acquired in the step S 205  and the lens position of the focus lens  3 A acquired in the step S 207  are stored as the evaluated AF coordinate values in a storage section (not shown) (step S 208 ). It is to be noted that such a relation between the lens position of the focus lens  3 A and the evaluated AF value has been described above with reference to  FIG. 3 . 
   Subsequently, it is judged with reference to the evaluated AF coordinate value whether or not a focused point (the peak value of the evaluated AF value) has been passed (step S 209 ). In a case where it is judged in this step S 209  that the focused point (the peak value of the evaluated AF value) is not passed, it is judged whether or not the scan region set in the step S 201  or S 202  has all been scanned (step S 210 ). In a case where it is judged in this step S 210  that all the scan region has been scanned, a region to be scanned remains. Therefore, the processing returns to the step S 205 . 
   It is to be noted that in a loop of the steps S 205  to S 210 , the focus lens  3 A continues to be driven. When the processing of the steps S 205  to S 210  is repeated, the peak value of the imager AF can be searched. 
   In addition, in a case where it is judged in the step S 209  that the focused point (the peak value of the evaluated AF value) is passed, a command to stop the driving of the focus lens  3 A is transmitted to the lens control section  5  by the body and lens communication, and the driving of the focus lens  3 A is stopped (step S 211 ). 
   Subsequently, the lens position of the focus lens  3 A at the time when the evaluated AF value reaches the peak value is obtained in detail by the interpolation with reference to the evaluated AF coordinate value. Moreover, the lens driving section  4  moves the focus lens  3 A to a position where the evaluated AF value reaches the peak value via the lens control section  5  by the body and lens communication (step S 212 ). 
   Subsequently, the peak value of the evaluated AF value is stored as a result of the imager AF in the storage section (not shown) (step S 213 ) to end the processing of the imager AF. The processing returns to a main routine of the flow chart shown in  FIG. 8 . In addition, in a case where it is judged in the step S 210  that all the scan region has been scanned, the focused point (the peak value of the evaluated AF value) is not obtained (branched from the step S 209  to NO), and the processing in the scan region ends (branched from the step S 210  to NO). Therefore, the focus lens  3 A is moved to an initial position of the scan region (step S 214 ). Moreover, the storage section (not shown) stores that the imager AF cannot be detected to end the processing. The processing returns to the main routine of the flow chart shown in  FIG. 8 . 
   The operation control of the interchangeable lens  2  by the lens control section  5  will hereinafter be described with reference to a flow chart shown in  FIG. 11 . 
   First, when the power source (not shown) of the camera body  1  is turned on, the lens power source is supplied to the interchangeable lens  2  via the lens contact section  8  from a camera body side. The lens power source is supplied to the interchangeable lens  2  to initialize each section of the interchangeable lens  2 , and the lens control section  5  can be operated. Moreover, the processing waits until there is a request for the body and lens communication from the control section  16  (step S 300 ). Here, when the demand for the body and lens communication is generated from the control section  16 , the body and lens communication is performed, and a command transmitted from the control section  16  is received (step S 301 ). 
   Next, it is judged whether or not the imager AF lens driving command (represented by an IAF lens driving command in  FIG. 11 ) which is the lens driving command of the imager AF has been received (step S 302 ). In a case where it is judged in this step S 302  that the imager AF lens driving command has been received, the lens driving of the focus lens  3 A is executed by the lens driving section  4  based on the imager AF lens driving command (step S 309 ). It is to be noted that this step S 309  corresponds to the step S 204  (lens movement start) shown in  FIG. 10 . 
   After the lens driving is started in the step S 309 , the processing waits until the signal VDP output from the control section  16  to the lens control section  5  via the lens contact section  8  and synchronized with the vertical sync signal VD falls (step S 310 ). Here, when it is detected that the signal VDP falls, output data of the encoder  15  indicating the lens position of the focus lens  3 A is acquired (step S 311 ). Moreover, the processing waits until the signal VDP rises (step S 312 ). Here, when it is detected that the signal VDP rises, the lens position of the focus lens  3 A acquired in the step S 311  is transmitted to the control section  16  (step S 313 ). 
   Subsequently, it is judged whether or not a lens stop command which is a command to stop the driving of the focus lens  3 A has been received (step S 314 ). In a case where it is judged in this step S 314  that the lens stop command has been received, the lens driving section  4  stops the driving of the focus lens  3 A (step S 315 ). Moreover, the processing returns to the step S 300 . On the other hand, in a case where it is judged in the step S 314  that the lens stop command is not received, the processing returns to the step S 310 . Subsequently, the processing of the steps S 310  to S 314  is repeated until it is judged in the step S 314  that the lens stop command has been received. 
   In addition, in a case where it is judged in the step S 302  that the imager AF lens driving command has not been received, it is judged whether or not the lens driving command of the TTL phase-difference AF has been received (step S 303 ). In a case where it is judged in this step S 303  that the lens driving command of the TTL phase-difference AF has been received, the lens driving section  4  drives the focus lens  3 A based on the lens driving amount and the driving direction included in the lens driving command of the TTL phase-difference AF (step S 306 ). When the lens driving of this step S 306  ends, a lens driving end notice is transmitted to the control section  16  (step S 307 ). Subsequently, the processing returns to the step S 300 . 
   On the other hand, in a case where it is judged in the step  303  that the lens driving command of the TTL phase-difference AF is not received, it is judged whether or not an initial communication command has been received (step S 304 ). In a case where it is judged in this step S 304  that the initial communication command has been received, initial body and lens communication is performed (step S 308 ). 
   It is to be noted that during the body and lens communication performed in the step S 308 , the processing communicates with the control section  16  of the camera body  1  to perform initial setting of the interchangeable lens  2 . Moreover, various data stored in the interchangeable lens  2  are transmitted to the control section  16 . 
   It is to be noted that examples of the data stored in the interchangeable lens  2  include information such as the lens type, the focal length, the shootable distance, the total number of the focus pulses and the motor type and various corrected values concerning the AF. After ending the processing of the step S 308 , the processing returns to the step S 300 . 
   Moreover, in a case where it is judged in the step S 304  that the initial communication command is not received, it is judged whether or not a command other than the above command has been received, and an operation is executed in response to the command (step S 305 ). 
   Timings of operation control during the imager AF will hereinafter be described with reference to a timing chart shown in  FIG. 12 . It is to be noted that the processing of the step S 110  (the imager AF) of the flow chart shown in  FIG. 8  indicates a series of processing of the flow chart shown in  FIG. 10 . 
   First, in the step S 204  of the flow chart shown in  FIG. 10 , the control section  16  transmits the imager AF lens driving command to the lens control section  5 . Moreover, the lens control section  5  receives the imager AF lens driving command. In the step S 309  of the flow chart shown in  FIG. 11 , the lens driving section  4  starts the lens driving of the focus lens  3 A. 
   On the other hand, the encoder  15  generates a signal pulse which is an encoder signal with the movement of the focus lens  3 A. Moreover, the lens control section  5  counts the signal pulses to acquire the lens position of the focus lens  3 A. 
   It is to be noted that, as seen from the timing chart shown in  FIG. 12 , the control section  16  continuously drives the focus lens  3 A. In the camera body  1 , the imaging operation of the image pickup device  7  is performed at a predetermined timing of the vertical sync signal VD generated by the image processing section  13 . 
   Moreover, when the exposure (EXP of the image pickup device  7  operation timing chart shown in  FIG. 12 ) of the image pickup device  7  ends, the image data of the image pickup device  7  is read out by the image processing section  13  (READ of the image pickup device  7  timing chart shown in  FIG. 12 ). In parallel with this readout operation, the image processing section  13  calculates the evaluated AF value (IAF) (the step S 205  of the flow chart shown in FIG.  10 ). It is to be noted that the end timing of the calculation of the evaluated AF value is set beforehand so that the calculation ends before the vertical sync signal VD rises. 
   Moreover, when the lens control section  5  waits until the signal VDP falls (the step S 310  of the flow chart shown in  FIG. 11 ) and detects the falling of the signal VDP, the section acquires the data of the lens position of the focus lens  3 A from the pulse count output of the encoder  15  ( FIG. 11 : step S 311 ). 
   Subsequently, when the lens control section  5  waits until the signal VDP (the vertical sync signal VD) rises ( FIG. 11 : step S 312 ) and detects the rising of the signal VDP, the section transmits the data of the lens position of the focus lens  3 A acquired as described above to the control section  16  ( FIG. 11 : step S 313 ). 
   In other words, when the control section  16  waits until the vertical sync signal VD rises ( FIG. 10 : step S 206 ) and detects the rising of the vertical sync signal VD, the section receives the lens position transmitted from the lens control section  5  ( FIG. 10 : step S 207 ). 
   As described above, the control section  16  performs the body and lens communication with the lens control section  5  in synchronization with the rising of the vertical sync signal VD. In consequence, the data of the lens position of the focus lens  3 A during the falling of the vertical sync signal VD can be acquired. 
   It is to be noted that a series of operations including the exposure operation of the image pickup device  7  to the transmission operation of the data of the lens position of the focus lens  3 A to the control section  16  by the lens control section  5  are repeatedly executed during the driving of the photographing lens system  3  while the imager AF operation is performed. 
   Moreover, when the control section  16  transmits the lens stop command to the lens control section  5  by the body and lens communication, the lens control section  5  allows the lens driving section  4  to stop the driving of the focus lens  3 A ( FIG. 11 : step S 315 ). 
   As described above, according to the first embodiment, there can be provided the digital camera and the camera system capable of performing the highly precisely focusing control at the high speed regardless of optical characteristics of the interchangeable lens for use and a focus lens driving mechanism. 
   Specifically, lens type data such as whether or not the interchangeable lens  2  is suitable for the TTL phase-difference AF and/or the imager AF is stored beforehand in the interchangeable lens  2 . Moreover, it is judged on a camera body  1  side based on the lens type data whether or not the interchangeable lens  2  for actual use is suitable for the TTL phase-difference AF and/or the imager AF. Here, in a case where it is judged that the interchangeable lens  2  for actual use is suitable for the TTL phase-difference AF, the focusing control is performed by the TTL phase-difference AF. In a case where it is judged that the interchangeable lens  2  for actual use is suitable for the imager AF, the focusing control is performed by the imager AF. Moreover, in a case where it is judged that the interchangeable lens  2  for actual use is suitable for both of the TTL phase-difference AF and the imager AF, the focusing control is coarsely adjusted by the TTL phase-difference AF system. Subsequently, the focusing control is finely adjusted by the imager AF. As described above, the optimum automatic focusing method is automatically selected in accordance with the optical characteristics of the interchangeable lens  2  for actual use and the focusing control mechanism to perform the focusing control. In consequence, the highly precisely focusing control can be performed at the high speed. 
   Second Embodiment 
   Next, a digital camera and a camera system according to a second embodiment of the present invention will be described. It is to be noted that only contents different from those of the digital camera and the camera system according to the first embodiment will be described. 
   Operation control performed by a control section  16  of the digital camera according to the second embodiment will hereinafter be described with reference to a flow chart shown in  FIG. 13 . 
   First, when a user turns on a power source (not shown) disposed in a camera body  1 , the control section  16  of the camera body  1  performs body and lens communication (step S 400 ). That is, in this step S 400 , the control section  16  reads out various data stored in a storage section  5 A of an interchangeable lens  2 , and stores the data in a storage section (not shown) of the control section  16 . 
   Moreover, examples of the data concerning the interchangeable lens  2  to be communicated during this body and lens communication include information such as the total number of focus pulses (hereinafter referred to as the total number of the lens pulses) corresponding to the whole shooting distance range of the interchangeable lens  2 , a focus lens driving speed (hereinafter referred to as the lens speed), a focal length, a shootable distance and a driving motor type and various corrected values concerning AF. It is to be noted that in the second embodiment, the focus lens driving speed is grasped as the number of driving pulses per unit time. 
   After ending the body and lens communication in the step S 400 , the user half presses a release button to wait until a release switch  18  (1RSW) is turned on (step S 401 ). Moreover, when the 1RSW is turned on, the step S 401  is branched to YES to judge lens data of the interchangeable lens  2  based on the data acquired during the initial body and lens communication of the step S 400  (step S 402 ). Specifically, during the judgment of the lens data in this step S 402 , the lens data is judged based on data of the total number of the lens pulses and the lens speed, and the judgment result is stored in the storage section (not shown) disposed in the control section  16 . 
   Subsequently, it is judged whether or not the total number of the lens pulses is smaller than a predetermined value A (step S 403 ). In a case where it is judged in this step S 403  that the total number of the lens pulses is smaller than the predetermined value A, it is judged whether or not the lens speed is larger than a predetermined value V (step S 404 ). In a case where it is judged in this step S 404  that the lens speed is not larger than the predetermined value V, processing of steps S 405  to S 414  and steps S 430 , S 431  and S 432  is performed. Here, the steps S 405  to S 414  are steps which perform processing similar to that of the steps S 105  to S 114  of the first embodiment. Moreover, the steps S 430 , S 431  and S 432  are steps which perform processing similar to that of the steps S 130 , S 131  and S 132  of the first embodiment. Furthermore, after ending the processing of the step S 432 , the processing returns to the step S 401 . In a case where it is judged in the step S 404  that the lens speed is larger than the predetermined value V, the processing advances to the step S 410 . In addition, in a case where it is judged in the step S 403  that the total number of the lens pulses is not smaller than the predetermined value A, processing of steps S 415  to S 421  is performed. Here, the steps S 415  to S 421  are steps which perform processing similar to that of the steps S 115  to S 121  of the first embodiment. Moreover, after ending the processing of the step S 420  or S 421 , the processing shifts to a shooting sequence of the step S 414 . 
   As described above, in the digital camera and the camera system according to the second embodiment, in a case where the total number of the lens pulses is larger than the predetermined value A, only TTL phase-difference AF is executed. In a case where the total number of the lens pulses is smaller than the predetermined value A and the lens speed is larger than the predetermined value V, only imager AF is executed. Moreover, in a case where the total number of the lens pulses is smaller than the predetermined value A and the lens speed is smaller than the predetermined value V, focusing control is coarsely adjusted by the TTL phase-difference AF, and the focusing control is finely adjusted by imager AF. 
   As described above, according to the second embodiment, there can be provided a digital camera and a camera system which produce effects equivalent to those of the first embodiment. 
   That is, in the second embodiment, whether or not the interchangeable lens  2  is an interchangeable lens suitable for the TTL phase-difference AF or the imager AF is judged by use of parameters such as the total number of the lens pulses which is the total number of the focus pulses corresponding to the whole shooting distance range of the interchangeable lens  2  and the lens speed which is the focus lens driving speed. Here, in a case where it is judged that the interchangeable lens  2  is suitable for the TTL phase-difference AF, the focusing control is performed by the TTL phase-difference AF. In a case where it is judged that the interchangeable lens  2  is suitable for the imager AF, the focusing control is performed by the imager AF. Moreover, in a case where it is judged that the interchangeable lens  2  is suitable for both of the TTL phase-difference AF and the imager AF, the focusing control is coarsely adjusted by the TTL phase-difference AF system. Subsequently, the focusing control is finely adjusted by the imager AF. As described above, the optimum automatic focusing method is automatically selected in accordance with optical characteristics of the interchangeable lens  2  and a focusing control mechanism to perform the focusing control. In consequence, the highly precisely focusing control can be performed at the high speed. 
   Alternative Example 
   It is to be noted that instead of setting parameters such as the total number of lens pulses which is the total number of focus pulses corresponding the whole shooting distance range of a interchangeable lens  2  and a lens speed which is a movement speed of a focus lens  3 A, needless to say, a numeric value (the total number of the lens pulses/the lens speed) obtained by dividing the total number of the lens pulses by the lens speed may be set as the parameter. 
   Here, the numeric value obtained by dividing the total number of the lens pulses by the lens speed is a parameter which is proportional to a lens driving time, that is, time required for focusing control. Therefore, even if the numeric value obtained by dividing this total number of the lens pulses by the lens speed is used, length of a focusing control time can be judged. 
   Third Embodiment 
   Next, a digital camera and a camera system according to a third embodiment of the present invention will be described. It is to be noted that only contents different from those of the first embodiment will be described. 
   Operation control performed by a control section  16  of the digital camera according to the third embodiment will hereinafter be described with reference to a flow chart shown in  FIG. 14 . 
   First, when a user turns on a power source (not shown) disposed in a camera body  1 , the control section  16  of the camera body  1  performs body and lens communication (step S 500 ). That is, in this step S 500 , the control section  16  reads out various data stored in a storage section  5 A of an interchangeable lens  2 , and stores the data in a storage section (not shown) of the control section  16 . Moreover, examples of the data concerning the interchangeable lens  2  to be communicated during this body and lens communication include information such as a shootable focal length corresponding to the whole shooting region of the interchangeable lens  2  and a driving motor type and various corrected values concerning AF. 
   After ending the body and lens communication in the step S 500 , the user half presses a release button to wait until a release switch  18  (1RSW) is turned on (step S 501 ). Moreover, when the 1RSW is not turned on, the body and lens communication is performed to acquire a state of the interchangeable lens  2  (step S 523 ), and the processing returns to the step S 501 . It is to be noted that, when the interchangeable lens  2  is, for example, an interchangeable lens of a zooming type, examples of the information of the interchangeable lens  2  acquired in the step S 523  include a focal length value in a case zooming is performed to change a focal length. In a case where the interchangeable lens  2  is an interchangeable lens having a function capable of limiting a shootable distance range, the examples of the information include the smallest distance value in a case where the smallest distance is changed. 
   In addition, in a case where it is judged in the step S 501  that the 1RSW has been turned on, the lens data of the interchangeable lens  2  is judged based on data acquired during the initial body and lens communication of the step S 500  (step S 502 ). 
   Specifically, during the lens data judgment of the step S 502 , the judgment is performed based on data of the smallest shootable distance of the interchangeable lens  2 , the focal length and the type of the motor which drives a focus lens  3 A. The judgment result is stored in the storage section (not shown) disposed in the control section  16 . 
   After ending the data judgment processing of the step S 502 , it is judged whether or not the smallest shootable distance of the interchangeable lens  2  is smaller than a predetermined value L (step S 503 ). In a case where it is judged in this step S 503  that the smallest shootable distance of the interchangeable lens  2  is smaller than the predetermined value L, it is judged whether or not the focal length of the interchangeable lens  2  is smaller than a predetermined value f (step S 504 ). In a case where it is judged in this step S 504  that the focal length of the interchangeable lens  2  is smaller than the predetermined value f, the processing advances to step S 511  described later. 
   On the other hand, in a case where it is judged in the step S 504  that the focal length of the interchangeable lens  2  is not smaller than the predetermined value f, it is judged whether or not a driving source included in a lens driving section  4  is a stepping motor (step S 505 ). 
   It is to be noted that driving source data for judgment of a driving source in the step S 505  is set as shown in, for example,  FIG. 15 . That is, lens driving source data ( 0 ,  1  or  2 ) is data indicating that the driving source is a DC motor, a stepping motor or an ultrasonic motor. 
   In a case where it is judged in the step S 505  that the driving source included in the lens driving section  4  is the stepping motor, the processing advances to the step S 511  described later. On the other hand, in a case where it is judged in the step S 505  that the driving source included in the lens driving section  4  is not the stepping motor, processing of steps S 506  to S 515  and steps S 530 , S 531  and S 532  is performed. 
   Here, the steps S 506  to S 515  are steps which perform processing similar to that of the steps S 405  to S 414  of the second embodiment. Moreover, the steps S 530  to S 532  are steps which perform processing similar to that of the steps S 430  to S 432  of the second embodiment. 
   In addition, in a case where it is judged in the step S 503  that the smallest shootable distance of the interchangeable lens  2  is not smaller than the predetermined value L, processing of steps S 516  to S 522  is performed. Here, the steps S 516  to S 522  are steps which perform processing similar to that of the steps S 115  to S 121  of the first embodiment. 
   It is to be noted that in the step S 521 , focusing display indicating that a focused state is obtained is displayed in an LCD panel  10  by an image processing section  13 . Subsequently, in the step S 522 , display indicating that the lens has a non-focused state is displayed in the LCD panel  10  by the image processing section  13 . Subsequently, the processing shifts to a shooting sequence of the step S 515 . 
   As described above, in the digital camera and the camera system according to the third embodiment, in a case where the smallest shootable distance of the interchangeable lens  2  is larger than the predetermined value L, only TTL phase-difference AF is executed. In a case where the smallest shootable distance of the interchangeable lens  2  is smaller than the predetermined value L and the focal length is smaller than the predetermined value f, and in a case where the smallest shootable distance of the interchangeable lens  2  is smaller than the predetermined value L, the focal length is larger than the predetermined value f and the stepping motor is used as the driving source of the focus lens  3 A, only imager AF is executed. Moreover, in a case where the smallest shootable distance of the interchangeable lens  2  is smaller than the predetermined value L, the focal length is larger than the predetermined value f and a motor other than the stepping motor is used as the driving source of the focus lens  3 A, focusing control is coarsely adjusted by the TTL phase-difference AF, and the focusing control is finely adjusted by imager AF. 
   It is to be noted that even in a case where an interchangeable lens of such a zooming type that the focal length is variable as described above, an interchangeable lens of such a type that the smallest distance changes with the zooming or an interchangeable lens having a function capable of changing the shootable distance range is used as the interchangeable lens  2 , the latest state of the interchangeable lens  2  is acquired in the step S 523 . Therefore, the focal length and the smallest distance during the AF are necessarily reflected in the judgment of the steps S 503  and S 504 . 
   As described above, according to the third embodiment, there can be provided a digital camera and a camera system which produce effects equivalent to those of the first embodiment. 
   That is, in the third embodiment, whether or not the interchangeable lens  2  is an interchangeable lens suitable for the TTL phase-difference AF or the imager AF is judged by use of parameters such as the smallest shootable distance of the interchangeable lens  2 , the focal length and the type of the driving motor of the focus lens  3 A. 
   Here, in a case where it is judged that the interchangeable lens  2  is suitable for the TTL phase-difference AF, the focusing control is performed by the TTL phase-difference AF. In a case where it is judged that the interchangeable lens  2  is suitable for the imager AF, the focusing control is performed by the imager AF. Moreover, in a case where it is judged that the interchangeable lens  2  is suitable for both of the TTL phase-difference AF and the imager AF, the focusing control is coarsely adjusted by the TTL phase-difference AF system. Subsequently, the focusing control is finely adjusted by the imager AF. As described above, the optimum automatic focusing method is automatically selected in accordance with optical characteristics of the interchangeable lens  2  and a focusing control mechanism to perform the focusing control. In consequence, the highly precisely focusing control can be performed at the high speed. 
   It is to be noted that even if a shooting magnification is used as the judgment parameter instead of the smallest shootable distance of the interchangeable lens  2 , needless to say, a similar effect is obtained. 
   Fourth Embodiment 
   Next, a digital camera and a camera system according to a fourth embodiment of the present invention will be described. It is to be noted that only contents different from those of the first embodiment will be described. 
   Operation control performed by a control section  16  of the digital camera according to the fourth embodiment will hereinafter be described with reference to a flow chart shown in  FIG. 16 . 
   First, when a user turns on a power source (not shown) disposed in a camera body  1 , the control section  16  of the camera body  1  performs body and lens communication (step S 600 ). That is, in this step S 600 , the control section  16  reads out various data stored in a storage section  5 A of an interchangeable lens  2 , and stores the data in a storage section (not shown) of the control section  16 . 
   It is to be noted that examples of the data concerning the interchangeable lens  2  to be communicated during this body and lens communication include information indicating whether or not an accessory such as a telephoto converter, a wide converter or a extension tube (a close-up ring) is attached to the interchangeable lens  2 . The attachment of this accessory can be detected with an electric contact disposed at, for example, the interchangeable lens  2 . This attachment information can be stored in the storage section  5 A of the interchangeable lens  2 . Based on this attachment information, the control section  16  as a judgment section of the camera body  1  judges the accessory which is attached to the interchangeable lens. 
   After ending the body and lens communication in the step S 600 , the user half presses a release button to wait until a release switch  18  ( 1 RSW) is turned on (step S 601 ). Here, when the  1 RSW is not turned on, the body and lens communication is performed to acquire information of the interchangeable lens  2  (step S 623 ), and the processing returns to the step S 601 . 
   It is to be noted that, when the interchangeable lens  2  is, for example, an interchangeable lens of a zooming type, examples of the information of the interchangeable lens  2  acquired in the step S 623  include a focal length value in a case zooming is performed to change a focal length. In a case where the interchangeable lens  2  is an interchangeable lens having a function capable of limiting a shootable distance range, the examples of the information include the smallest distance value in a case where the smallest distance is changed. 
   Moreover, in a case where it is judged in the step S 601  that the  1 RSW has been turned on, lens data of the interchangeable lens  2  is judged based on data acquired during the initial body and lens communication of the step S 600  (step S 602 ). 
   Specifically, during the lens data judgment of the step S 602 , it is judged whether or not an accessory such as the telephoto converter, the wide converter or the extension tube (the close-up ring) is attached to the interchangeable lens  2 . The judgment result is stored in a storage section disposed in the control section  16 . 
   After ending the lens data judgment processing of the step S 602 , it is judged whether or not the wide converter is attached to the interchangeable lens  2  (step S 603 ). In a case where it is judged in this step S 603  that the wide converter is attached to the interchangeable lens  2 , the processing advances to step S 611  described later. 
   In a case where it is judged in the step S 603  that the wide converter is not attached to the interchangeable lens  2 , it is judged whether or not the extension tube is attached to the interchangeable lens  2  (step S 604 ). In a case where it is judged in this step S 604  that the extension tube is attached to the interchangeable lens  2 , the processing advances to step S 606  described later. 
   In a case where it is judged in the step S 604  that the extension tube is not attached to the interchangeable lens  2 , it is judged whether or not the telephoto converter is attached to the interchangeable lens  2  (step S 605 ). In a case where it is judged in this step S 605  that the telephoto converter is not attached to the interchangeable lens  2 , the processing advances to the step S 606  described later. 
   In a case where it is judged in the step S 605  that the telephoto converter is attached to the interchangeable lens  2 , processing of steps S 616  to S 622  is performed. Here, the steps S 616  to S 622  are steps which perform processing similar to that of the steps S 115  to S 121  of the first embodiment. 
   It is to be noted that in the step S 621 , focusing display indicating that a focused state is obtained is displayed in an LCD panel  10  by an image processing section  13 . Subsequently, in the step S 622 , display indicating that the lens has a non-focused state is displayed in the LCD panel  10  by the image processing section  13 . Subsequently, the processing shifts to a shooting sequence of step S 615  which performs processing similar to that of the step S 515 . 
   In addition, in a case where it is judged in the step S 604  that the extension tube is attached to the interchangeable lens  2  and it is judged in the step S 605  that the telephoto converter is not attached to the interchangeable lens  2 , processing of steps S 606  to S 615  and steps S 630  to S 632  is performed. Here, the steps S 606  to S 615  are steps which perform processing similar to that of the steps S 105  to S 114  of the first embodiment. The steps S 630  to S 632  are steps which perform processing similar to that of the steps S 130  to S 132 , respectively. After ending the processing of the step S 632 , the processing returns to the step S 601 . 
   It is to be noted that in a case where it is judged in the step S 603  that the wide converter is attached to the interchangeable lens  2 , the processing advances to the step S 611  which performs processing similar to that of the step S 110  of the first embodiment to execute imager AF. Specific processing contents during this imager AF have been described in detail with reference to the flow chart shown in  FIG. 10 . 
   As described above, in the digital camera and the camera system according to the fourth embodiment, when the wide converter is attached to the interchangeable lens  2 , the only imager AF is executed. When the wide converter is attached to the interchangeable lens  2 , the focal length of the interchangeable lens  2  is converted into a shorter focal length. Therefore, a focusing control time does not change, a subject depth increases, and focusing control precision changes to be high. Therefore, it is more appropriate to use the imager AF which is more highly precise than TTL phase-difference AF. When the telephoto converter is attached to the interchangeable lens  2 , the only TTL phase-difference AF is executed. Since the focal length of the interchangeable lens  2  is converted into a longer focal length, an evaluated AF value (contrast) less changes with respect to a change of a predetermined defocus amount. This is disadvantageous for the imager AF. Moreover, in a case where the extension tube is attached to the interchangeable lens  2 , after coarsely adjusting focusing control by the TTL phase-difference AF, the focusing control is finely adjusted by the imager AF. This is because, when the extension tube is attached to the interchangeable lens  2 , a relation between the defocus amount and a lens movement amount changes, the precision of the focusing control by the TTL phase-difference AF drops, and time required for focusing lengthens. Therefore, in such a case, the TTL phase-difference AF is used during the only coarse adjustment. Subsequently, the fine adjustment is performed by the imager AF in which any precision drop is not generated. 
   As described above, according to the fourth embodiment, there can be provided a digital camera and a camera system which produce effects equivalent to those of the first embodiment. 
   That is, in the fourth embodiment, whether or not the interchangeable lens  2  has a state suitable for the TTL phase-difference AF or the imager AF is judged by use of parameters such as whether or not an accessory such as the wide converter, the extension tube or the telephoto converter is attached to the interchangeable lens  2 . Here, in a case where it is judged that the interchangeable lens  2  is suitable for the TTL phase-difference AF, the focusing control is performed by the TTL phase-difference AF. In a case where it is judged that the interchangeable lens  2  is suitable for the imager AF, the focusing control is performed by the imager AF. Moreover, in a case where it is judged that the interchangeable lens  2  is suitable for both of the TTL phase-difference AF and the imager AF, the focusing control is coarsely adjusted by the TTL phase-difference AF system. Subsequently, the focusing control is finely adjusted by the imager AF. As described above, the optimum automatic focusing method is automatically selected in accordance with optical characteristics of the interchangeable lens  2  and a focusing control mechanism to perform the focusing control. In consequence, the highly precisely focusing control can be performed at the high speed. 
   While there has been shown and described what are considered to be preferred embodiments of the invention, it will, of course, be understood that various modifications and changes in form or detail could readily be made without departing from the spirit of the invention. It is therefore intended that the invention not be limited to the exact forms described and illustrated, but constructed to cover all modifications that may fall within the scope of the appended claims.