Patent Publication Number: US-2010123782-A1

Title: Autofocus system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2008-294513 filed on Nov. 18, 2008; the entire of which are incorporated herein by reference. 
     BACKGROUND 
     1. Technical Field 
     The present invention relates to an autofocus system, and particularly, to an autofocus system having an AF frame auto-tracking function for allowing an AF frame (an AF area), which represents an area of a subject brought into focus by autofocus (AF), to automatically track a predetermined subject. 
     2. Related Art 
     Generally, in autofocus (AF) systems for automatically adjusting the focus of a camera, the camera requires instruction on where to focus. In the general cameras, a focusing position is fixed on the center of a photographing area, for example a person and the like at the center of the photographing area are made to come into focus. 
     However, when a moving subject is photographed, it is not preferable that the focusing position is fixed as described above. Accordingly, there is proposed an AF area auto-tracking system which changes autofocus (AF) area in accordance with movement of a subject in order to bring the subject into focus when a quickly moving subject in sporting scenes is photographed by, for example, a TV camera and the like (for example, see Patent Document 1 (JP-A-2006-267221 corresponding to US-A-2006/0140612)). In the present specification, the AF frame indicating the outline of the AF area mostly refers to the area of the subject brought into focus similarly to the AF area. 
     In addition, there is proposed a digital camera which detects an image representing a face of a person in the taken images, and automatically brings into focus the face as the subject or automatically changes a zoom ratio so as to magnify the area in which the face is displayed (for example, see Patent Document 2 (JP-A-2004-320286 corresponding to US-A-2004/0207793)). 
     However, the tracking target subject subjected to the auto-tracking of the AF frame is not limited to the face of the person, and may be various things. Accordingly, it is difficult to appropriately perform the auto-tracking of the AF frame in the same processing algorithm regardless of the type of the tracking target subject. 
     SUMMARY 
     Illustrative aspects of the present invention provide an autofocus system capable of performing the auto-tracking of the AF frame suitable for the subject set as the tracking target. 
     [1] According to an aspect of the invention, an autofocus system includes: an image pickup unit that takes a subject image formed by an optical system; an autofocus unit that performs focus adjustment of the optical system so as to bring into focus a subject within a predetermined AF frame area in a photographing image taken by the image pickup unit; and an AF frame control unit that changes the AF frame area The AF frame control unit includes: an AF frame auto-tracking unit that allows the AF frame to automatically track a tracking target subject by detecting the tracking target subject in the photographing image taken by the image pickup unit and automatically changing the AF frame so as to correspond to an area of the detected tracking target subject, the AF frame auto-tracking unit having a plurality of tracking modes capable of setting different subjects as the tracking target subject; and a selection unit that selects auto-tracking of the AF frame based on a desired tracking mode among the plurality of tracking modes. 
     [2] The autofocus system of [1], the plurality of tracking mode may include at least two tracking modes among a first tracking mode of setting an arbitrary object as the tracking target subject, a second tracking mode of setting a face of an arbitrary person as the tracking target subject, and a third tracking mode of setting a face of a predetermined specific person as the tracking target subject. 
     [3] The autofocus system of [2], the AF frame control unit, in the first tracking mode, may store the tracking target subject as a reference pattern and detect the area of the tracking target subject in the photographing image through a pattern matching process of detecting an image area matching with the reference pattern in the photographing image. 
     [4] The autofocus system of [2] or [3], the AF frame control unit, in the second tracking mode, may detect an image area of the face of the arbitrary person in the photographing image through a face detection process and detect an area of the tracking target subject in the photographing image on the basis of the detected image area. 
     [5] The autofocus system of any one of [2] to [4], 
     in the third tracking mode, information on the face of the predetermined specific person may be set as identification data. And the AF control unit, in the third tracking mode, may detect the area of the tracking target subject in the photographing image by detecting the image area of the face of the specific person in the photographing image through a face recognition process using the identification data. 
     [6] The autofocus system of any one of [1] to [5], the AF frame control unit may further comprise: a manual change unit that changes the area of the AF frame on the basis of manual operation of an operator. 
     With the configuration of [1] to [6], it is possible to perform the auto-tracking of the AF frame suitable for the type of the subject by selecting the tracking mode suitable for the subject set as the tracking target of the AF frame. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exterior view illustrating a TV camera system according to an exemplary embodiment of the invention. 
         FIG. 2  is a block diagram illustrating an entire configuration of an AF frame auto-tracking system applied to the TV camera system of  FIG. 1 . 
         FIGS. 2-I  and  2 -II are partial block diagrams of  FIG. 2 . 
         FIG. 3  is an explanatory diagram of an AF frame (an AF area). 
         FIG. 4  is an exterior diagram of a focus demand. 
         FIG. 5  is a diagram illustrating an example of a screen displayed on a liquid crystal display equipped with a touch panel. 
         FIG. 6  is a diagram illustrating the case where display of a menu screen displayed on the liquid crystal display equipped with the touch panel is turned off. 
         FIG. 7  is a flowchart illustrating a processing procedure of an object tracking mode. 
         FIG. 8  is a diagram illustrating an example of a screen displayed on the liquid crystal display equipped with the touch panel in a face detection tracking mode. 
         FIG. 9  is a flowchart illustrating a processing procedure of the face detection tracking mode. 
         FIG. 10  is a diagram illustrating an example of the screen displayed on the liquid crystal display equipped with the touch panel in a face recognition mode. 
         FIG. 11  is a flowchart illustrating a processing procedure of the face recognition mode. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, an autofocus system according to an exemplary embodiment of the invention will be described with reference to the accompanying drawings. 
       FIG. 1  is an exterior view illustrating a TV camera system according to an embodiment of the invention. As shown in the drawing, the TV camera  10  is generally used in broadcasting or business, includes a lens unit  12  and a camera main body  14 , and is supported on a camera platform  18  installed on a pedestal dolly  16 . 
     Two left and right pan rods  22  and  24  are provided to extend from the camera platform  18 , a focus demand (a focus controller)  26  is set by a mounting clamp  38  on a grip part  22 A of the right pan rod  22 , and a zoom demand (a zoom controller)  28  is set on a grip part of the left pan rod  24 . 
     The focus demand  26  is provided with focus knobs  30  that can be turned. When the focus knobs  30  are turned at the time of focus control performed by a manual focus (an MF), a focus control signal, which instructs a focus (a focus lens) to move to the focus position corresponding to the turned position as a target position, is transmitted from the focus demand  26  to the lens unit  12 . In response to the signal, the focus lens of the lens unit  12  moves to the target position based on the instruction of the focus control signal. 
     The zoom demand  28  is provided with a thumb ring  34  that can be turned. When the thumb ring  34  is turned in the left and right directions, a zoom control signal, which instructs a zoom (a zoom lens) to move at the zoom speed corresponding to the turned position as a target speed, is transmitted from the zoom demand  28  to the lens unit  12 . In response to the signal, the zoom lens of the lens unit  12  moves in the target speed based on the instruction of the zoom control signal. 
     Although omitted in the drawings, the focus demand  26  is provided with various operation members relating to the autofocus (the AF), and is equipped with an AF frame control device (an AF frame auto-tracking device) for performing the control (change in position and the like) of the AF frame representing the target subject area (the target area of the AF) brought into focus by the AF. In addition, various operation members of the AF frame control device are also provided on the focus demand  26 . 
     Additionally, as shown in the drawing, a liquid crystal display (an LCD) equipped with touch panel  40  as a component of the AF frame control device is provided on the upper part of the main body of the focus demand  26  by the installation opening, and is connected to the focus demand  26  via a cable which is not shown. 
     The LCD  40  to be described later means the liquid crystal display  40  equipped with the touch panel. In addition, the LCD  40  can be provided on an arbitrary position other than the upper part of the main body of the focus demand  26 . For example, the LCD  40  may be provided on the side of viewfinder  36 . 
     On the camera main body  14 , a viewfinder  36 , which is a display device, is provided. In order to display an image of a subject being taken by the TV camera  10  on the viewfinder  36 , the cameraman can photograph the subject with a desired composition by operating the focus demand  26  and the zoom demand  28  while viewing the image. Furthermore, the photographing video or the photographing image to be described later means a video or an image being photographed by the TV camera  10  at the present time. 
     On the photographing video displayed on the viewfinder  36 , an image of the AF frame indicating a position, a size, and a shape (an aspect ratio) of the AF frame set currently is superimposed. With such a configuration, when the focus control based on the AF is preformed, it is possible to know which area&#39;s subject in the photographing video is brought into focus. Further, MF and AF focus controls can be changed by a mode switch provided on the focus demand  26 . 
       FIGS. 2 ,  2 -I and  2 -II are block diagrams for illustrating an entire configuration of an AF frame auto-tracking system applied to the TV camera system. The AF frame auto-tracking system  1  shown in  FIGS. 2 ,  2 -I and  2 -II includes the lens unit  12  and a camera main body  14  of the TV camera shown in  FIG. 1 , a viewfinder  36 , and an AF area operating unit  54  integrated in the focus demand  26 . In addition, the drawing shows components of the focus demand  26 , which is shown in  FIG. 1 , including a focusing operation section  50 , and an image processing unit  58  and an AF frame operation section  60  which constitute the AF frame control device (the AF frame auto-tracking device) mounted on the focus demand  26 . 
     TV camera  10  includes the camera main body  14  of an HD camera corresponding to the Hi-Vision TV [HD (High Definition) TV] system, and the lens unit  12  having a photographing lens (an optical system) set on the lens mount of the camera main body  14 . 
     In the camera main body  14 , an image pickup device (for example, a CCD), necessary signal processing circuits, and the like are mounted. After an image formed by the photographing lens of the lens unit  12  is photoelectrically converted by the image pickup device, a signal process necessary for each of the signal processing circuits is performed thereon, and the image is output as a video signal (an HD TV signal) of the HD TV system from a video signal output terminal and the like of the camera main body  14  to the outside. 
     As shown in  FIG. 1 , the viewfinder  36  provided on the upper part of the camera main body  14  displays the photographing video of the TV camera  10 . The viewfinder  36  displays not only the photographing video but also various information. For example, an image indicating the area (the position, the size, and the shape) of the currently set AF frame is superimposed on the photographing video. 
     The lens unit  12  includes a photographing lens (a zoom lens)  64  set on the lens mount of the camera main body  14 . The photographing lens  64  forms an image of a subject  56  on the image pickup surface of the image pickup device of the camera main body  14 . Although omitted in the drawings, movable sections for adjusting photographing conditions of a focus lens group, a zoom lens group, and an aperture diaphragm as components are provided in the photographing lens  64 . These movable sections are electrically driven by a motor (a servomechanism). For example, the focus lens group and the zoom lens group are moved in an optical axis direction, focus (subject distance) adjustment is performed by the movement of the focus lens group, and focal length (zoom ratio) adjustment is performed by the movement of the zoom lens group. 
     In the system relating to the AF, if only at least the focus lens group is electrically driven, the other movable sections may be manually driven. 
     The lens unit  12  is also equipped with an AF unit  66  and a lens CPU which is not shown. The lens CPU controls the entire system of the lens unit  12  overall. The AF unit  66  is a processing section for acquiring information required to perform the focus control (autofocus adjustment) based on the AF, and includes an AF processing section and an AF image pickup circuit which are not shown. 
     The AF image pickup circuit is disposed on the lens unit  12  in order to acquire a video signal for AF processing, and includes a processing circuit for outputting output signals of the image pickup devices such as CCD and the AF image pickup devices as video signals of a predetermined format. Furthermore, the video signal output from the AF image pickup circuit is a brightness signal. 
     On the image pickup surface of the AF image pickup device, light of the subject is imaged which is diverged from light of the subject incident on the image pickup device of the camera main body  14  by a half mirror disposed in the optical path of the photographing lens  64 . The photographing area and the subject distance (a distance at which the subject is brought into focus) relative to the image pickup area of the AF image pickup device is set to coincide with the photographing area and the subject distance relative to the image pickup area of the image pickup device of the camera main body  14 . In addition, the subject image acquired by the AF image pickup device is set to coincide with the subject image acquired by the image pickup device of the camera main body  14 . It is not necessary to make the both photographing areas perfectly coincide with each other. For example, the photographing area of the AF image pickup device may be a large area including the photographing area of the image pickup device of the camera main body  14 . 
     The AF processing section acquires a video signal from the AF image pickup circuit, and calculates a focus evaluation value representing a level of contrast of the subject image within the AF area (the AF frame) as the AF target area on the basis of the video signal. For example, a high frequency signal is extracted by a high pass filter from the video signals acquired from the AF image pickup device, and then a signal of the area corresponding to the AF area, which is set as described later, is integrated for each one of screens (each one of frames). The integrated value acquired for each one of the screens mean the level of contrast of the subject image within the AF area, and the integrated value is sent as the focus evaluation value to the lens CPU. 
     The lens CPU acquires the information of AF frame (the AF frame information) representing the AF area (the outline) from the image processing unit  58  as described later, and allows the AF processing section to specify an area within the AF frame, which is specified by the AF frame information, as the AF area. Then, the focus evaluation value demanded for the image within the AF area (the video signal) is acquired from the AF processing section. 
     As described above, whenever the video signal per one screen is acquired from the AF image pickup circuit (whenever the AF processing section demands the focus evaluation value), the focus evaluation value is acquired from the AF processing section, and the focus lens group is controlled so that the acquired focus evaluation value becomes the maximum (the largest value), that is, the contrast of the subject image within the AF frame becomes the maximum. For example, the mountain climbing method is generally known as a control method of the focus lens group based on the focus evaluation value. In this method, when the first lens group is moved in a direction increasing the focus evaluation value and a point, at which the focus evaluation value begins to decrease, is detected, the focus lens group is set at this position. In such a manner, the subject within the AF frame is automatically brought into focus. 
     The above-mentioned AF processing section acquires the video signal from the AF image pickup device mounted in the lens unit  12  in order to calculate the focus evaluation value. However, it may be possible to adopt a configuration in which the video signal of the video photographed by the image pickup device of the camera main body  14  is acquired from the camera main body  14 . In addition, anything may be used as the AF unit for automatically bringing into focus the subject within the AF frame. 
     Here, the AF area  200 , as shown in  FIG. 3 , is set as the tetragonal area relative to the image pickup area  202  of the image pickup device in the camera main body  14 . The frame  204  representing the outline is defined as the AF frame. The subject, which is photographed in the AF area  200  (in the AF frame  204 ) of the image pickup device, is set as a target brought into focus by the AF. 
     In the specification, the area of the AF frame  204  (the AF area  200 ) relative to the image pickup area  202  is determined by three factors of a position, a size, and a shape (an aspect ratio) of the AF frame  204 . In addition, in the description to the effect that “the area of the AF frame is changed” means change in at least one factor among the three factors of the position, the size, and the shape of the AF frame. 
     The lens unit  12  is connected directly or through a cable to the camera main body  14 , and is able to exchange various information through the serial communication interfaces (SCI)  12   a  and  14   a  respectively provided in the lens unit  12  and the camera main body  14 . With such a configuration, the AF frame information, which is currently set in the AF unit  66 , is also transmitted to the camera main body  14 , and the AF frame image corresponding to the position, the size, and the shape of the AF frame, which is currently set in the photographing video displayed on the viewfinder  36 , is superimposed by the process in the camera main body  14 . 
     The focusing operation section  50  is a component of the focus demand  26 , and is a component included in a general focus demand. The components of the focusing operation section  50  includes the focus knobs  30  shown in  FIG. 1 , operation members for AF control and MF control such as a mode switch (not shown in the drawings) for switching the AF mode and the MF mode or switching the AF mode type (a continuous mode or a momentary mode) and a AF start switch (not shown in the drawings) for commanding the start of the AF, and a processing circuit for detecting a setting state of the operation members and transmitting a control signal on the basis of the detected setting state. 
     The focus demand  26  is provided with an interface (I/F)  52  for connecting with the lens unit  12  through the cable. The focusing operation section  50  is connected to the lens unit  12  through the I/F  52  and the cable, and is configured to exchange various signals with the lens CPU through the SCI  12   a  by using a serial communication. 
     With such a configuration, the various control signals transmitted from the focusing operation section  50  are sent to the lens CPU, and processes based on the control signal are executed by the lens CPU. For example, when the instruction of the focus control (the AF mode) based on the AF is issued, the focus control based on the AF is performed on the basis of the focus evaluation value which can be obtained from the AF unit  66  as described above. When the instruction of the focus control (the MF mode) based on the MF is issued, the focus control based on the MF is performed in response to a focus position command signal which is transmitted from the focusing operation section  50  on the basis of the operation of the focus knobs  30 . 
     The image processing unit  58  is a processing section mounted on the focus demand  26  as a component of the AF frame control device, and is a processing section for specifying the area (the position, the size, the shape (the aspect ratio)) of the AF frame, which is set in the AF unit  66  of the lens unit  12 , by the AF frame auto-tracking process or manual operation to be described later. 
     The image processing unit  58  includes a SCI  70 . The SCI  70  is connected to the lens unit  12  through the I/F  52 , and is configured to exchange various signals with the lens CPU through the SCI  12   a . With such a configuration, the AF frame information specifying the area of the AF frame is transmitted from the image processing unit  58  to the lens CPU of the lens unit  12 , and the area of the AF frame in the AF unit  66  is set on the basis of the AF frame information. 
     Further, in the focus demand  26 , the image processing unit  58  is provided with a video input connector for receiving the video signal, and to the video input connector, a video output connector of the camera main body  14  is connected through the down converter  68  by using a cable. With such a configuration, an HD TV signal output from the video output connector of the camera main body  14  is converted (down conversion) by a down converter  68  into a video signal (an SDTV signal) of the standard TV [NTSC (Television system committee)] system, and is input to the image processing unit  58 . 
     Detailed description of the above will be given later. However, when the AF frame auto-tracking process is executed, the image processing unit  58  sequentially loads the photographing images for each one screen from the video signal input from the camera main body  14 , and performs a process for detecting a predetermined tracking target subject from the inner part of the photographing image. Then, the image processing unit  58  determines the area of the AF frame so as to bring the subject into focus by the AF, and transmits the area of the determined area of the AF frame to the lens CPU of the lens unit  12 . 
     Furthermore, the configuration and the processing contents of the image processing unit  58  will be described later. 
     The AF frame operation section  60 , as the AF frame control device, is provided integrally with the image processing unit  58  in the focus demand  26 , and a part or all thereof is provided in a device separated from the focus demand  26 , that is, a device separated from the image processing unit  58 , and is connected thereto through a cable and the like. In the embodiment, as shown in  FIG. 1 , the LCD equipped with touch panel  40  is provided separately from the focus demand  26  (the image processing unit  58 ), and the other components are provided together with the image processing unit  58  in the focus demand  26 . 
     The AF frame operation section  60  is an operation section for mainly performing operations for the AF frame control, and includes an operation member for allowing an operator to manually input instruction information on the area of the AF frame and an operation member for performing the operation for the AF frame auto-tracking for allowing the AF frame to automatically track a desired subject. 
     As shown in the exterior view of the focus demand  26  of  FIG. 4 , operation members of the AF frame operation section  60  are formed thereon. The operation members include: a position operation member  100  (for example, a joy stick or a track ball) for vertically moving the position of the AF frame by manual operation of a user; a size operation member  102  (for example, a handle) for changing the size of the AF frame by manual operation; an operation member  104  (for example, a handle) for changing the shape of the AF frame by manual operation; a tracking start switch  108  for instructing start of the AF frame auto-tracking; and a tracking stop switch  110  for instructing stop of the AF frame auto-tracking. Setting states of these operation members  100 ,  102 ,  104 ,  108 , and  110  can be read by the image processing unit  58  (the CPU  78  of main board  70  to be described later) 
     Further, the LCD  40  of the AF frame operation section  60  is operable to input settings such as the AF frame auto-tracking modes by touch operation (tap operation). The image displayed on the LCD  40  is properly changed in accordance with the setting contents by the CPU  78  of the image processing unit  58 . The display and operation of the LCD  40  will be described later. 
     Furthermore, the embodiment shows the aspect in which the AF frame control device having the image processing unit  58  and the AF frame operation section  60  is provided in the focus demand  26 . However, the AF frame control device can be formed separately from the focus demand  26 . Further, in this case, a part or all of the AF frame operation section  60  may be provided integrally with the image processing unit  58  and may be provided separately. 
     Next, the configuration and the processing contents of the image processing unit  58  will be described. 
     The image processing unit  58  mainly includes a main board  70 , a pattern matching process calculation board  72 , and a face recognition process calculation board  74 . The main board  70 , the pattern matching process calculation board  72 , and the face recognition process calculation board  74  are respectively equipped with CPUs  78 ,  90 , and  92 . On each of the boards, each calculation process is performed. The CPUs  78 ,  90 , and  92  are connected via a BUS line or a control line so as to exchange data with each other and perform synchronization among the calculation processes. 
     The overall processes in the image processing unit  58  are performed in the main board  70 . The main board  70  is provided with not only the CPU  78  for performing the calculation process but also a SCI  70   a , a decoder (the A/D converter)  76 , a superimpose  82 , a RAM  80 , and the like. 
     The SCI  70   a  is, as described above, an interface circuit for performing the serial communication with the SCI  12   a  of the lens unit  12 , and transmits the AF frame information and the like to the lens unit  12 . 
     The decoder  76  is a circuit for converting the video signal (the SDTV signal) of the photographing video of the TV camera  10  input from the down converter  68  to the image processing unit  58  into data which can be digitally processed by the image processing unit  58 . The decoder  76  performs an A/D conversion process and the like for converting the analog SDTV signal into a video signal of digital data. 
     The superimpose  82  is a circuit for synthesizing the video signal of the photographing video obtained by the decoder  76  and the image signal generated by the CPU  78  and outputting and displaying the synthesized video signal to and on the LCD  40 . With such a configuration, the photographing video of the TV camera  10  is displayed on the LCD  40  similarly to the viewfinder  36  provided on the camera main body  14 . In addition, the AF frame image indicating the area of the currently set AF frame, a menu screen (a menu image) configured to be able to perform the input operation in the touch panel, and the like are displayed on the LCD  40  so as to be superimposed on the photographing video. Furthermore, it is also apparent that only the image generated by the CPU  78  can be displayed without being superimposed on the photographing video. 
     The RAM  80  is a memory for temporarily storing the data used in the calculation process of the CPU  78 . 
     On the other hand, the pattern matching process calculation board  72  and the face recognition process calculation board  74  are calculation boards for individually performing the pattern matching and face detection/recognition processes. These boards respectively include not only the CPUs  90  and  92  for performing the calculation process but also VRAMs  94  and  96  for temporarily storing the image data. 
     Further, the image processing unit  58  is provided with a slot  115  for receiving a data card  114  as an external memory such as an SD (Secure Digital) card or a USB. In the image processing unit  58 , when the face of the specific person is detected by the face recognition, the identification data representing the face of the specific person in the data card  114  is previously stored, and the data card  114  is inserted into the slot  75 , thereby enabling the CPU  78  to read the identification data required for the face recognition from the data card  114 . 
     Subsequently, the control of the AF frame performed by the image processing unit  58  configured as described above will be described together with the process relating to the display and operation of the LCD  40 . 
     First, the display and operation of the LCD  40  will be described. As shown in  FIG. 5 , a screen  40   a  of the LCD  40  displays a menu screen (a menu image), which is formed of various buttons  300  to  314 , and an AF frame image  204  (it is simply referred to as an AF frame  204 ), which represents the area of the currently set AF frame, by superimposing those on the photographing video of the TV camera  10 . The images, which are superimposed on the photographing video, such as the various buttons  300  to  314  of the menu screen and the AF frame  204  are generated by the CPU  78  of the main board  70  in the image processing unit  58  shown in  FIGS. 2 ,  2 -I and  2 -II. These images are displayed on the LCD  40  so as to be superimposed on the photographing video of the TV camera  10  obtained from the decoder  76  in the superimpose  82 . Furthermore, the control relating to the display (display contents) of the LCD  40  is performed by the CPU  78 . 
     On the other hand, since the LCD  40  has the touch panel, when the touch operation is performed, that is, when a tip of a finger and the like comes into contact with the screen  40   a  of the LCD  40 , position information representing the touched position (coordinates) is transmitted to the CPU  78 . With such a configuration, a type (the tap operation, the double tap operation, and the like) of the operation and the position of the touch operation performed on the screen  40   a  of the LCD  40  is detected by the CPU  78 . Then, the process based on the operation is executed by the CPU  78 . 
     Basic operations in the screen  40   a  of the LCD  40  include an operation for inputting instructions previously assigned to the respective buttons  300  to  314  and an operation for specifying the area of the AF frame  204 . The former operation is the tap operation performed on the positions of the buttons  300  to  314  with the tip of the finger and the like. The later operation for specifying the area of the AF frame  204  is able to, for example, move the AF frame  204  so as to make a desired position be the center of the AF frame  204  by performing the tap operation on the position, on the screen  40   a  of the LCD  40  displayed on the photographing video. Further, the later operation is able to change the shape and the size of the AF frame  204  by a drag operation that moves a side position or a touched vertex to a dragged position by touching the vertex or the side of the AF frame  204  with the tip of the finger and directly sliding it. 
     The menu screen (the menu image) displayed on the screen  40   a  of the LCD  40  will be described. In  FIG. 5 , the fixation mode selection button  300  displayed as “fixation”, the object tracking mode selection button  302  displayed as “object tracking”, the face detection tracking mode selection button  304  displayed as “face detection”, and the face recognition tracking mode selection button  306  displayed as “face recognition” are buttons for selecting the control modes of the AF frame. By performing the tap operation on any one of the buttons  300  to  306 , it is possible to select a desired mode among the fixation mode, the object tracking mode, the face detection tracking mode, and the face recognition tracking mode. Furthermore, the contents of the modes will be described later. 
     The set button  308  displayed as “set” and the reset button  310  displayed as “reset” are buttons for instructing the start and the stop of the AF frame auto-tracking. These buttons  308  and  310  are displayed only when the control modes (the object tracking mode, the face detection mode), by which an operator instructs the start and the stop of the AF frame auto-tracking, are selected. Furthermore, the set button  308  and the reset button  310  are buttons having the same function as the tracking start switch  108  and the tracking stop switch  110  (see  FIGS. 1 and 4 ) of the AF frame operation section  60 . 
     Further, the start of the AF frame auto-tracking is performed in the following way. When a double tap operation (an operation of tapping the same position twice continuously) is performed on the desired position on the screen  40   a , the AF frame is set on a position centered on the double-tapped position, and the AF frame auto-tracking is started. Specifically, the first tap operation of the double tap operation functions as an operation of instructing the movement of the AF frame to the tapped position, and the subsequent second tap operation functions as an operation of instructing the start of the AF auto-tracking. With such a configuration, it is possible to omit the operation of instructing the start of the AF frame auto-tracking by performing the tap operation on the set button  308 . Thus, it is possible to instruct promptly the start of the AF frame auto-tracking and the setting of the AF frame position. Furthermore, since the start of the AF frame auto-tracking is performed by just the double tap operation, the display of the set button  308  may be not performed. 
     The AF frame size selection buttons  312  (the small button  312   a , the medium button  312   b , and the large button  312   c ) displayed as “small”, “medium”, and “large” is buttons for selecting the size of the AF frame  204 , of which a rectangular shape (an aspect ratio) is invariant, among different three sizes previously determined. By performing the tap operation on any one of the small button  312   a , the medium button  312   b , and the large button  312   c , it is possible to instantaneously change the size of the AF frame  204 . When the small button  312   a  is tapped, the AF frame is set to have the smallest size, and when the large button  312   c  is tapped, the AF frame is set to have the largest size. 
     Here, the embodiment is configured so that the size of the AF frame  204  can be selected from three categories. However, two or four or more categories in size are previously determined, the AF frame size selection buttons corresponding to the respective sizes are displayed, and the respective sizes of the AF frame  204  may be selected therefrom by performing the tap operation on the respective AF frame size selection buttons. Further, not only the size but also the shape of the AF frame may be selected. 
     The aspect of the selection unit for selecting a desired type of the AF frame from plural types of the AF frame different in size and shape is not limited to the embodiment in which the selection buttons are provided to correspond to the various types. For example, in a state where sequence numbers (Nos. 1 to N) are assigned to the respective plural types of the AF frame previously determined, buttons for sequentially switching the types of the AF frame in accordance with the sequence numbers may be provided. Specifically, it may be allowed that one switch button for switching the types of the AF frame is displayed on the screen  40   a  of the LCD  40 , the current AF frame is changed into the AF frame with the sequence number (which is obtained by adding 1 to the currently set sequence number of the AF frame) which is increased by 1 whenever the switch button is tapped, and when the sequence number of the AF frame becomes the maximum (No. N), then the subsequent sequence number of the AF frame is changed (changed by a toggle type) into No. 1. Further, it may be also allowed that two up and down buttons are displayed, and the current AF frame is changed into the AF frame with the sequence number which is increased by 1 whenever the up button is tapped, and is changed into the AF frame with the sequence number which is decreased by 1 whenever the down button is tapped. 
     Additionally, it may be possible to adopt a determination method in which selectable types of the AF frame includes AF frames having different sizes (diagonal distances) with a given difference and the AF frames having different shapes (aspect ratios) with a given difference. In addition, it may be allowed that the size or the shape of the AF frame is changed by a given amount whenever the above-mentioned switch button, the up button, or the down button is tapped. At this time, when the button for changing the size of the AF frame and the button for changing the shape of the AF frame are separately provided, it is possible to change both of the size and the shape of the AF frame. 
     Furthermore, the selection unit for selecting the types of the AF frame is not limited to the aspect in which the above-mentioned button for selecting the types of the AF frame is displayed on the screen  40   a  of the LCD  40  as described above. Alternatively, it may be allowed that, with the aspect, by providing a mechanical button (a switch) in the main body  26   a  of the focus demand  26  or the like, which is shown in  FIG. 4 , as a component of the AF frame operation section  60  of  FIGS. 2 ,  2 -I and  2 -II, the types of the AF frame can be changed by the button. 
     Further, it may be allowed that the operation, which changes the AF frame  204  to have arbitrary size and shape by dragging the vertex or the side of the AF frame  204  as described above, can be activated with the operation which changes those into the previously determined size and shape in the same manner as the operation of the AF frame size selection button  312 . In addition, it may be allowed that, only any one of the operations is activated, and which operation to be activated can be selected by the tap operation and the like performed on the predetermined button displayed on the screen  40   a  of the LCD  40 . 
     In  FIG. 5 , the menu display ON/OFF button  314  displayed as “display OFF” is a button for turning off the display of the menu screen (menu image) other than the button  314 . When the menu display ON/OFF button  314  is tapped, as shown in  FIG. 6 , the display of the buttons  300  to  312  on the menu screen is turned off. At this time, the menu display ON/OFF button  314  is displayed as “display ON”, and when the menu display ON/OFF button  314  is tapped again, the menu screen is displayed to be superposed on the photographing video as shown in  FIG. 5 . With such a configuration, the operator can turn the display of the menu screen off in a situation in which the display of the menu screen superposed on the photographing video is unnecessary. As a result, it is possible to prevent the menu screen from disturbing the photographing work. 
     Further, the display of the menu screen is not limited to the case where the operator determines that it is not necessary as described above, and it may be automatically determined that it is not necessary. For example, when a given time has elapsed from the time when the last touch operation on the screen  40   a  (or the touch operation for the buttons  300  to  314  of the menu screen) was performed, that is, when the touch operation on the screen  40   a  was not performed during the given time, it is possible to determine that the display of the menu screen is not necessary. 
     In the CPU  78  of the main board  70 , there may be provided a timing function of automatically turning off the display of the menu screen if the given time elapses when it is determined whether or not the given time elapses from the time when the last touch operation on the screen  40   a  (or the touch operation for the buttons  300  to  314  of the menu screen) is performed (whether or not the touch operation on the screen  40   a  is performed during the given time). In this case, it may be allowed that the time of turning off the display of the menu screen can be set to an arbitrary value by a user. 
     Further, when the operator performs a zooming operation (the operation of the zoom demand  28  shown in  FIG. 1 ) of the lens unit  12 , and after the action of the AF frame auto-tracking to be described later is started, it is possible to determine that the display of the menu screen is not necessary. 
     In the CPU  78  of the main board  70 , there may be provided a function of turning off the display of the menu screen when it is detected that the zooming operation is being performed by acquiring the information as to whether or not the zooming operation is performed from the lens unit  12  or when the processing of the AF frame auto-tracking is started. Since the CPU  78  performs the overall processing of the AF frame auto-tracking, it is possible to detect the start of the processing of the AF frame auto-tracking on the basis of the self-processing information. 
     Further, when the display of the menu screen is turned off by the automatic display OFF function, the menu screen is displayed, for example, by touching an arbitrary position on the screen  40   a . When the function of turning on/off the display of the menu screen by means of the menu display ON/OFF button  314  is employed together with the automatic display OFF function, the display of the menu screen is performed by performing the tap operation on the menu display ON/OFF button  314 . 
     On the other hand, when the display of the menu screen is turned on/off, it may be automatically detected from the functions mentioned above that the display of the menu screen is necessary. For example, when the AF frame auto-tracking is performed, it may be difficult to perform the tracking because of some reason. In this case, the operation on the menu screen is needed, and thus it is necessary to display the menu screen again. At this time, effort and time are needed in order for the operator to perform the operation for displaying the menu screen as described above. 
     Accordingly, in the CPU  78  of the main board  70 , there may be provided an automatic display ON function of automatically displaying the menu screen when it is difficult to perform the AF frame auto-tracking in a state where the display of the menu screen is deleted on the screen  40   a  of the LCD  40 . As described above, since the CPU  78  performs the overall processing of the AF frame auto-tracking, it can be detected that it is difficult to perform the AF frame auto-tracking on the basis of the self-processing information. 
     Subsequently, the control modes of the AF frame, which can be selected by the fixation mode selection button  300 , the object tracking mode selection button  302 , the face detection tracking mode selection button  304 , and the face recognition tracking mode selection button  306  displayed on the screen  40   a  of  FIG. 5 , will be described. In the embodiment, the control modes of the AF frame include four modes of a fixation mode, an object tracking mode, a face detection tracking mode, and a face recognition tracking mode. The mode selection can be performed by performing the tap operation on any one of the selection buttons  300 ,  302 ,  304 , and  306 . 
     The fixation mode is a mode (manual mode) of allowing an operator to specify the frame (the position, the size, and the shape) of the AF area by means of manual operation and fixing the AF frame at the specified position. The fixation mode is a useful mode for the photographing in the news program in which a camera is scarcely moved. 
     When the fixation mode selection button  300  on the screen  40   a  of the LCD  40  of  FIG. 5  is tapped, then the fixation mode is selected, and the CPU  78  mounted on the main board  70  of the image processing unit  58  performs the processing of the fixation mode. 
     Specifically, the CPU  78  determines the area of the AF frame on the basis of, as described above, the operation of changing the area of the AF frame on the screen  40   a  of the LCD  40  and operations of operation members (a position operation member  100 , a size operation member  102 , and a shape operation member  104 ) for changing the AF frame  204  provided on the AF frame operation section  60  by means of manual operation. When determining the area of the AF frame, the CPU  78  transmits the AF frame information representing the area of the AF frame through the SCI  70   a  to the lens CPU of the lens unit  12 . 
     The object tracking mode which is one mode of the AF frame auto-tracking and is a mode of allowing the AF frame to track arbitrary kinds of objects. The object tracking mode is a useful mode for the photographing in the horse race relay broadcasting and the car race relay broadcasting in which an object other than a face of a person should be tracked. 
     When the object tracking mode selection button  302  on the screen  40   a  of the LCD  40  of  FIG. 5  is tapped, the object tracking mode is selected, and the CPU  78  mounted on the main board  70  of the image processing unit  58  starts the processing of the object tracking mode. 
       FIG. 7  is a flowchart illustrating a processing procedure of the object tracking mode. Hereinafter, the processing of the object tacking mode will be described with reference to the flowchart. Furthermore, when the object tracking mode is selected, the screen  40   a  of the LCD  40  displays the menu screen shown in  FIG. 5 . 
     The CPU  78  of the main board  70  performs a process (an initial setting processing of the AF frame) for changing the AF frame in accordance with the manual operation similarly to the fixation mode until the operation of instructing the start of the AF frame auto-tracking is given from the AF frame operation section  60  and setting the tracking target. That is, an operator specifies the area of the AF frame so that the area includes a subject image as a tracking target (an AF target), and in accordance therewith, the CPU  78  sets the area of the AF frame (step S 10 ). Furthermore, in  FIG. 5 , the AF frame  204  is set on the face of the person. However, in the object tracking mode, an object other than the face of the person is determined as the tracking target. 
     Subsequently, when the operator performs operation to instruct the start of the AF frame auto-tracking, the CPU  78  (and the CPU  90  of the pattern matching process calculation board  72 ) starts the processing of the AF frame auto-tracking (step S 14  to S 26 ) based on the pattern matching, and starts the processing (transmission of the AF frame information) of allowing the lens CPU of the lens unit  12  to specify the area of the AF frame determined by the processing of the AF frame auto-tracking (step S 12 ). 
     Furthermore, the instruction to start the AF frame auto-tracking is performed by performing the tap operation on the set button  308  or the double tap operation on an arbitrary position (a position at which the AF frame is set) on the screen  40   a  of the LCD  40  shown in  FIG. 5 . Further, when the tracking start switch  108  provided as a mechanical switch in the AF frame operation section  60  is pressed, the instruction to start the AF frame auto-tracking is performed. On the screen  40   a  of the LCD  40 , when the start of the AF frame auto-tracking is instructed by the double tap operation, the position setting of the AF frame in step S 10  also can be performed. However, it may also be possible to adopt an aspect in which the double tap operation at the arbitrary position is set as only the operation of instructing the start of the AF frame auto-tracking. In this case, the double tap operation is irrespective of the position setting of the AF frame. 
     Further, when the focus control based on the AF is not performed at the start of the AF frame auto-tracking (the AF mode is not activated), the start of the AF is also instructed in conjunction with the start of the AF frame auto-tracking. 
     When the processing of the AF frame auto-tracking is started, the CPU  90  of the pattern matching process calculation board  72  loads the image data of the photographing image corresponding to one screen from the decoder  76  in response to the instruction issued from the CPU  78  (step S 14 ). Subsequently, the CPU  90  acquires the area of the currently set AF frame from the CPU  78 , and sets (stores) the image within the area of the AF frame in the loaded photographing image as a reference pattern image (step S 16 ). Then, the processing of the following steps S 18  to S 26  is repeated. 
     First, the CPU  90  loads the image data of the photographing image corresponding to one screen from the decoder  76  (step S 18 ), and detects the image area coinciding with the reference pattern image in the photographing image by performing the pattern matching process (step S 20 ). Then, the detected image area is notified to the CPU  78  of the main board. 
     The CPU  78  determines whether or not the reference pattern image moves, that is, whether or not the image area in which the reference pattern is detected precedes the area of the currently set AF frame (step S 22 ). Furthermore, YES is also determined in this determination process when the size of the reference pattern image is changed in the photographing image. 
     If YES is determined in step S 22 , the image area detected in step S 20  is set (updated) as a new area of the AF frame, and the AF frame information representing the area of the AF frame is transmitted to the lens CPU of the lens unit  12  (step S 24 ). 
     Further, the CPU  90  of the pattern matching process calculation board  72  updates the image within the image area detected in step S 22  as a new reference pattern image (step S 26 ). 
     If No is determined in step S 22 , the update of the AF frame in step S 24  is not performed, and only the update of the reference pattern in step S 26  is performed. 
     When the processing of step S 26  is terminated, the flow returns to the processing of step S 18 . 
     Furthermore, when an operator performs the operation of instructing the stop of the AF frame auto-tracking, for example, the tap operation of the reset button  310  displayed on the screen  40   a  of the LCD  40 , the processing of the AF frame auto-tracking is stopped, and the flow returns to step S 10 . Further, the focus control based on the AF may be stopped. 
     The face detection tracking mode is one mode of performing the auto-tracking of the AF frame, and a mode of allowing the AF frame to track a face of an arbitrary person. The face detection tracking mode is a useful mode for the photographing in the music program and the like in which a face of a person should be detected and tracked. 
     When the face detection tracking made selection button  304  on the screen  40   a  of the LCD  40  of  FIG. 5  is tapped, the face detection tracking mode is selected, and the CPU  78  mounted on the main board  70  of the image process unit  58  starts the processing of the face detection tracking mode. Further, when the face detection tracking mode is selected, the area of the AF frame is automatically set in accordance with the face of the person. Hence, on the screen  40   a  of the LCD  40 , the AF frame size selection button  312  of  FIG. 5  is not displayed as shown in  FIG. 8 . 
       FIG. 9  is a flowchart illustrating the processing procedure of the face detection tracking mode. Hereinafter, the processing of the face detection tracking mode will be described with reference to the flowchart. 
     When the face detection tracking mode is selected, first the CPU  78  of the main board  70  performs the process (the initial setting processing of the AF frame) for setting a face of a tracking target. Then, the CPU  78  instructs the CPU  92  of the face identification process calculation board  74  to start the face detection process. Thereby, first, the CPU  92  of the face recognition process calculation board  74  loads the image data of the photographing image corresponding to one frame from the decoder  76  (step S 30 ). Subsequently, the CPU  92  performs the known face detection process of detecting a face (a face image) of an arbitrary person included in the photographing image (step S 32 ). Then, the area of the face image is notified to the CPU  78  of the main board  70 . Furthermore, when the face images of the plurality of persons are included in the photographing image, the areas of the plurality of face images are detected, and are notified to the CPU  78 . 
     The CPU  78 , as shown in  FIG. 8 , displays the areas of the detected face images as the face frames  204   a ,  204   b , and  204   c  on the screen  40   a  of the LCD  40 . Then, when the operator performs the tap operation to select (specifies) a face as a tracking target (an AF target) among the faces of the persons shown by the face frames  204   a ,  204   b , and  204   c , the CPU  78  sets the selected face as the tracking target, and sets the face frame of the face, which is set as the tracking target, as the AF frame (step S 34 ). 
     Furthermore, the face frame before the AF frame setting is displayed by a color different from that of the AF frame. For example, the face frame may be displayed by green, and the AF frame may be displayed by red. Further, when the operator sets the selected face frame as the AF frame, the CPU  78  turns off the display of the face frame on the screen  40   a  of the LCD  40 . Additionally, when the face frame is one, the face frame may be automatically set as the AF frame even if the operator does not perform the operation of selecting the tracking target. 
     As described above, the AF frame is set by the process (the initial setting processing of the AF frame) of setting the face of the tracking target. After that, when the operator performs the operation of instructing the start of the AF frame auto-tracking, the CPU  78  (and the CPU  92  of the face recognition process calculation board  74 ) starts the processing of the AF frame auto-tracking (steps S 38  to S 46 ) based on the face detection process, and starts the process (transmission of the AF frame information) of allowing the lens CPU of the lens unit  12  to specify the area of the AF frame determined by the processing of the AF frame auto-tracking (step S 36 ). 
     Here, the instruction to start the AF frame auto-tracking can be performed by performing the tap operation on the set button  308  or the double tap operation on the position of the AF frame similarly to the case of the object tracking mode. Further, in step S 34 , when the face frame as the face of the tracking target is selected (the AF frame is selected), instead of the tap operation, the double tap operation is performed on the selected face frame, and thereby it is possible to instruct the start of the AF frame auto-tracking while setting the face frame as the AF frame. However, it may also be possible to adopt an aspect in which the double tap operation at the arbitrary position is set as only the operation of instructing the start of the AF frame auto-tracking. In this case, the start of the AF frame auto-tracking is instructed by performing the double tap operation on the arbitrary position, irrespective of the position setting of the AF frame. Further, when the AF frame is set in step S 34 , the processing of the AF frame auto-tracking may be automatically started. Furthermore, when the focus control based on the AF is riot performed at the start of the AF frame auto-tracking similarly to the object tracking mode (the AF mode is not activated), the start of the AF is also instructed in conjunction with the start of the AF frame auto-tracking. 
     When the processing of the AF frame auto-tracking is started, the CPU  92  of the face recognition process calculation board  74  loads the image data of the photographing image corresponding to one frame from the decoder  76  in response to the instruction to execute the face detection process issued from the CPU  78  similarly to the processing of steps S 30  and S 32  (step S 38 ). In addition, the CPU  92  performs the face detection processing of detecting the face of the arbitrary person included in the photographing image (step S 40 ). Then, the detected image area is notified to the CPU  78  of the main board  70 . 
     The CPU  78  detects an area, which is most approximate to the area of the currently set AF frame, among the areas of the detected face images as the area of the face image of the tracking target (step S 42 ). Furthermore, in step S 40 , the area to detect the face may not be the area of the whole photographing image, and may be restricted within the vicinity of the position of the currently set AF frame. 
     Subsequently, the CPU  78  determines whether or not the face of the tracking target moves, that is, whether or not the area of the detected face image precedes the area of the currently set AF frame (step S 44 ). Furthermore, YES is also determined in this determination process when the size of the face image is changed. 
     If YES is determined in step S 44 , the area of the face image detected in step S 42  is set (updated) as a new area of the AF frame, and the AF frame information representing the area of the AF frame is transmitted to the lens CPU of the lens unit  12  (step S 46 ). Then, the flow returns to the processing of step S 38 . If No is determined in step S 44 , the update of the AF frame in step  546  is not performed, and the flow returns to the processing of step S 38 . 
     Furthermore, when an operator performs the operation of instructing the stop of the AF frame auto-tracking, for example, the tap operation of the reset button  310  displayed on the screen  40   a  of the LCD  40 , the processing of the AF frame auto-tracking is stopped, and the flow returns to step S 30 . Further, the focus control based on the AF may be stopped. The processing of the flowchart terminates the processing of the AF frame auto-tracking. 
     Further, in the face detection process of step S 40 , the face image may be not completely detected in the photographing image, and in the detecting of the face image of the tracking target of step S 42 , apparently the area of the face image most approximate to the area of the currently set AF frame may have no continuity with the area of the current AF frame (those may be too different). In this case, since the tracking is not possible, similarly to the above, the processing of the AF frame auto-tracking is stopped, and the flow returns to step S 30 . 
     The face recognition tracking mode is one mode of performing the auto-tracking of the AF frame, and a mode of allowing the AF frame to track the face of the person previously registered as identification data. The face recognition tracking mode is a useful mode for the photographing in the music program and the sports relay broadcast in which the person to be photographed is previously determined. 
     When the face detection tracking mode selection button  306  on the screen  40   a  of the LCD  40  of  FIG. 5  is tapped, the face recognition tracking mode is selected, and the CPU  78  mounted on the main board  70  of the image processing unit  58  starts the processing of the face recognition tracking mode. Further, when the face recognition tracking mode is selected, the area of the AF frame is automatically set in accordance with the face of the person. Hence, on the screen  40   a  of the LCD  40 , the AF frame size selection button  312  of  FIG. 5  is not displayed as shown in  FIG. 10 . Instead of this, as described later, registered face image display sections  316  ( 316   a  to  316   c ) relating to the face recognition, selection buttons  318   a  and  318   b , and an edit button  320  are displayed. Further, the set button  308  of  FIG. 5  for automatically performing the start of the AF frame auto-tracking when the registered face is detected from the identification data as described later is also not displayed. 
       FIG. 11  is a flowchart illustrating a processing procedure of the face recognition tracking mode. Hereinafter, the processing of the face recognition tracking mode will be described with reference to the flowchart. 
     When the face recognition tracking mode is selected, first the CPU  78  of the main board  70  performs the process (the initial setting processing of the AF frame) for setting a face of a tracking target. Specifically, in the data card  114  inserted into the slot  115  shown in FIGS.  2  and  2 -II, the identification data on one person&#39;s face or a plurality of faces of the persons as candidates of the tracking target is registered, and the CPU  78  reads the identification data from the data card  114 . Then, the CPU  78  instructs the CPU  92  of the face identification process calculation board  74  to start the face recognition process. Here, the identification data includes a plurality of data on one person&#39;s characteristics such as different face images on the invisible side, the front side, the left or right side, and the like from the eyes, a distance between the two eyes, a distance between the eyes and the nose, and proportions of those. 
     When the start of the face recognition process is instructed, the CPU  92  of the face recognition process calculation board  74  loads the image data of the photographing image corresponding to one frame from the decoder  76  (step S 50 ). In addition, the CFU  92  detects the face (the face image) of the arbitrary person included in the photographing image by using the face detection process the same as the face detection tracking mode. Subsequently, the CPU  92  acquires the identification data from the CPU  78  of the main board  70 , and performs the face recognition process of determining whether or not the face image detected by the face detection process is the face image of the specific person previously registered as the identification data, on the basis of the identification data (step S 52 ). Furthermore, the face detection process performed in the face recognition tracking mode is set as a part of the face recognition process, and the arbitrary face image is detected by the face detection process also in the face recognition process of step S 62  to be described later. Then, an association with the face of the identification data is performed. 
     When the face recognition process is terminated, the CPU  92  notifies the result to the CPU  78  of the main board  70 . In such a manner, the CPU  78  acquires the area of the face image obtained when the face of the specific person registered as the identification data is detected, and the area of the face image obtained when the face of the person unregistered as the identification data is detected. 
     Next, the CPU  78 , as shown in  FIG. 10 , displays the frames  204   a ,  204   b , and  204   c  in the areas of the face images of the detected faces of persons on the screen  40   a  of the LCD  40 . When the faces of the persons registered as the identification data is detected by the face recognition process of step S 52 , names of the persons are also displayed in the face frame. Additionally, as described above, the face images of the persons registered as the identification data are displayed on the registered face image display sections  316  ( 316   a  to  316   c ). 
     Here, the number of the face images displayed on the registered face image display sections  316  is changed in response to the number of the faces registered as the identification data. 
     The operator selects the face image as a tracking target among the face images displayed on the registered face image display sections  316  by performing the tap operation on the selection buttons  318   a  or  318   b . Whenever the upper selection button  318   a  is tapped, the selected face image is changed with the face image just above the currently selected face image. Whenever the lower selection button  318   b  is tapped, the selected face image is changed with the face image just below the currently selected face image. Furthermore, the face image currently selected in the registered face image display sections  316  is enlarged more than the other face images (see  316   b ). 
     In such a manner, when the operator selects the face as the tracking target among the faces registered as the identification data, the CPU  78  sets the selected face as the face of the tracking target (step S 54 ). 
     Furthermore, by performing the tap operation on the edit button  320 , it is possible to edit an order of the face images displayed on the registered face image display sections  316 . With such a configuration, for example, the faces of the plurality of persons registered as the identification data may be set as tracking targets in a predetermined order. In accordance with the order, when an order of the face images displayed on the registered face image display sections  316  is set, the faces of the tracking targets can be changed in the predetermined order whenever a single tap operation is performed on the selection button  318   a  or  318   b.    
     In such a manner, when the face of the tracking target is set, then the CPU  78  determines whether or not the face of the tracking target is detected in step S 52  (step S 56 ). If NO is determined, the flow returns to the processing of step S 50 , and the above-mentioned process is repeated. Specifically, until the face of the tracking target is detected in the photographing image by the face recognition process of step S 52 , the processing of steps S 50  to S 56  is repeated. 
     In contrast, if YES is determined in step S 56 , that is, if the face of the tracking target is detected in the photographing image, the area of the face image is set as the area of the AF frame (the initial setting processing of the AF frame). Then, the CPU  78  (and the CPU  92  of the face recognition process calculation board  74 ) starts the processing of the AF frame auto-tracking (steps S 60  to S 66 ) based on the face recognition process, and starts the process (transmission of the AF frame information) of allowing the lens CPU of the lens unit  12  to specify the area of the AF frame determined by the processing of the AF frame auto-tracking (step S 58 ). 
     Furthermore, when the focus control based on the AF is not performed at the start of the AF frame auto-tracking similarly to the object tracking mode or the face detection tracking mode (the AF mode is not activated), the start of the AF is also instructed in conjunction with the start of the AF frame auto-tracking. 
     When the processing of the AF frame auto-tracking is started, the CPU  92  of the face recognition process calculation board  74  loads the image data of the photographing image corresponding to one screen from the decoder  76  in response to the instruction to execute the face recognition process issued from the CPU  78  (step S 60 ). Further, the CPU  92  acquires the identification data on the face of the tracking target selected in step S 54  from the CPU  78 . In addition, the CPU  92  detects the face of the tracking target among the photographing image on the basis of the identification data on the face of the tracking target by using the face recognition process the same as that of step S 52 , and notifies the area of the face image to the CPU  78  (step S 62 ). 
     Subsequently, the CPU  78  determines whether or not the face of the tracking target moves, that is, whether or not the area of the detected face image precedes the area of the currently set AF frame (step S 64 ). Furthermore, YES is also determined in this determination process when the size of the face image is changed. 
     If YES is determined in step S 64 , the area of the face image detected in step S 62  is set (updated) as a new area of the AF frame, and the AF frame information representing the area of the AF frame is transmitted to the lens CPU of the lens unit  12  (step S 66 ). Then, the flow returns to the processing of step S 60 . If No is determined in step S 64 , the update of the AF frame in step S 66  is not performed, and the flow returns to the processing of step S 60 . 
     Furthermore, when an operator performs the operation of instructing the stop of the AF frame auto-tracking, for example, the tap operation of the reset button  310  displayed on the screen  40   a  of the LCD  40 , the processing of the AF frame auto-tracking is stopped, and the flow returns to step S 50 . At this time, the face of the tracking target is not set in anywhere. Further, in conjunction with the stop of the AF frame auto-tracking, the focus control based on the AF may be also stopped. 
     Further, the operator may change the face of the tracking target into a face different from the current face by using the selection button  318   a  or  318   b  during the processing of the AF frame auto-tracking. In this case, the changed new face is set as the face of the tracking target, the processing of the AF frame auto-tracking is stopped, and the flow returns to step S 50 . 
     Additionally, for example, the person set as the face of the tracking target may move out of the photographing area. That is, the face of the tracking target may be not detected in the photographing image in the face recognition process of step S 62 . In this case, since it is determined that the tracking is not possible, the processing of the AF frame auto-tracking is automatically stopped, and the flow returns to step S 50 . 
     In the embodiment as described above, it is possible to select a desired mode among the three modes such as the object tracking mode, the face tracking mode, and the face recognition tracking mode as the control mode of the AF frame auto-tracking. However, it may be possible to select only any two modes.