Abstract:
Disclosed herein is an image pickup apparatus including: an image sensor; and a shutter device, wherein said shutter device includes a trailing curtain, a first driving member, a second driving member, first urging force applying means, and a charging member.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a shutter device and an image pickup apparatus (image sensing apparatus) using the shutter device. 
         [0003]    2. Description of the Related Art 
         [0004]    As a shutter device for use in image pickup apparatuses, there is a shutter device in which a group of leading blades and a group of trailing blades are sequentially moved in the same direction, and an exposure operation is performed by use of a slit formed between the two blade groups. In this shutter device, the leading blades, an arm member rotationally connected to the leading blades, and a leading blade driving member for driving the arm member are provided, and the leading blades are driven. Besides, similarly, the trailing blades, an arm member rotationally connected to the trailing blades, and a trailing blade driving member for driving the arm member are provided, and the trailing blades are driven. Incidentally, in the following, operations of the trailing blades will be described mainly. 
         [0005]    For example, in a shutter device described in Japanese Patent Laid-open No. 2001-215555 (this shutter device will be referred to also as “the first related art”), when a predetermined setting (cocking) member (referred to also as charging member) is driven by a predetermined driving section, a trailing blade driving member is rotated according to this driving operation. The trailing blade driving member is connected with a spring in the state of being urged in a predetermined direction (a spring charged with elastic energy). The spring is such a spring that the urging force in the predetermined direction can be increased (referred to also as “overcharged”) by deforming it in a certain direction. Specifically, the spring is overcharged when the predetermined setting member is rotationally moved in a predetermined direction. 
         [0006]    In addition, with the trailing blade driving member attracted by an electromagnet, after the overcharging, the rotational movement of the trailing blade driving member is restrained. Further, when restraint on the urging force is released by stopping the energization of the electromagnet after the setting member is returned into its original position (after retraction), the trailing blade driving member is driven at high speed by the urging force of the spring. Since the trailing blade driving member is connected with the trailing blades (trailing curtain of shutter) through the arm member, the trailing blades are each moved at high speed from an opening position for a shutter aperture to a closing position for the shutter aperture, according to the driving of the trailing blade driving member. Thus, the trailing blade driving member is turned by the urging force of the spring having been overcharged, and a closing operation of the trailing blades (trailing shutter curtain) is performed according to the turning motion of the trailing blade driving member. 
         [0007]    In the shutter device according to the first related art, the spring is overcharged when the trailing blade driving member is turned in a certain direction by the movement of the setting member from a position to another position. In addition, when the trailing blade driving member is turned in the just-mentioned direction (the same direction), the trailing blades are each moved to the opening position for the shutter aperture. In other words, attendant on the turning motion of the trailing blade driving member, an overcharging operation and an opening operation of the trailing blades are carried out simultaneously. Therefore, when the spring is in the overcharged state, the trailing blades are each necessarily present in the opening position, and the trailing blades cannot each be present in the closing position for the shutter aperture when the spring is in the overcharged state. 
         [0008]    On the other hand, there is a shutter device different in configuration from the first related art. For example, in a shutter device described in Japanese Patent Laid-open No. Hei 11-95282 (this shutter device will be referred to also as “the second related art”), a driving system for a group of trailing blades includes a trailing blade operating member in addition to a trailing blade driving member. 
         [0009]    The trailing blade driving member is connected to an overcharging spring, while the trailing blade operating member is connected to each of the trailing blades through an arm member. In addition, after a setting member rotates the trailing blade driving member to a predetermined position so as to overcharge the spring, the setting member mechanically supports the trailing blade driving member. 
         [0010]    Besides, the trailing blade operating member, which is turned coaxially with the trailing blade driving member, can be turned independently of the trailing blade driving member. Specifically, when the trailing blade driving member is turned for an overcharging operation, the trailing blade operating member makes contact with a part of the setting member, whereby the trailing blade operating member is inhibited from rotating. As a result, only the trailing blade driving member is rotated, and the trailing blade operating member is not rotated. Therefore, trailing blades connected to the trailing blade operating member can each continue to be present at the closing position for the shutter aperture. Thus, according to the second related art, the spring can be overcharged while keeping each of the trailing blades in the closing position for the shutter aperture. Besides, in the overcharged state of the spring, mechanical support of the trailing blade driving member by the setting member can also be realized. 
         [0011]    Thereafter, energization of an electromagnet is started and attractive holding of the trailing blade driving member by the electromagnet is started, after which the setting member is moved so as to release the contact between the setting member and the trailing blade operating member. In response to this releasing operation, the trailing blade operating member is rotated, whereby the trailing blades are each moved into the opening position for the shutter aperture. In this manner, the trailing blades can each be moved to the opening position for the shutter aperture while maintaining the overcharged state of the spring. It is to be noted here, however, that in this condition, the setting member does not mechanically support the trailing blade driving member. 
       SUMMARY OF THE INVENTION 
       [0012]    Meanwhile, image pickup apparatuses capable of live-view shooting (live-view photographing) include those which can be switched between a live view mode using an electronic viewfinder (EVF) and an OVF mode using an optical finder (OVF) based on an observation optical system. 
         [0013]    In such an image pickup apparatus, for example, a shutter curtain is opened in the live view mode on one hand, and the shutter curtain is closed in the OVF mode on the other hand. 
         [0014]    In addition, in recent years, there have been image pickup apparatuses in which the function of the leading curtain, of a leading curtain and a trailing curtain in a shutter device, is replaced by an electronic operation (for example, line-by-line sequential resetting operations at an image sensor). 
         [0015]    Now, a case is supposed in which only the trailing curtain in the shutter device according to the first related art is used for the just-mentioned image pickup apparatus. In this case, the trailing blade driving member and the trailing blades are operated integrally. Therefore, if it is attempted to overcharge the spring by turning the trailing blade driving member in a certain direction, the trailing blades are each also moved to the opening position for the shutter aperture according to the turning motion of the spring. Accordingly, the shutter curtain (the trailing curtain) cannot be kept closed in the overcharged state of the spring. 
         [0016]    Therefore, it is impossible, for example, to perform the overcharging operation while keeping the shutter curtain closed at the time of framing by use of an optical finder. Or, it is impossible, as will be described later, to perform an overcharging operation concurrently with reading of pixel information from an image sensor  5  while keeping the shutter curtain closed immediately after completion of exposure at the image sensor  5 . 
         [0017]    On the other hand, when only the trailing curtain in the shutter device according to the second related art is used for such an image pickup apparatus, it is possible to realize both closure of the shutter curtain (trailing curtain) in the overcharged state of the spring and opening of the shutter curtain (trailing curtain) in the overcharged state of the spring. 
         [0018]    It is to be noted here, however, that when the second related art is utilized, the setting member does not mechanically support the trailing blade driving member in the condition where the trailing blades are each present in the opening position for the shutter aperture. In other words, it is impossible to maintain each of the trailing blade in the opening position for the shutter aperture by a mechanical supporting force. Therefore, for maintaining the just-mentioned condition, it is necessary to continue energization of the electromagnet. That is, the trailing blades can each be maintained in the opening position for the shutter aperture, only by energizing the electromagnet to attractingly hold the trailing blade driving member by a magnetic force. 
         [0019]    Therefore, for example when the second related art is utilized for an image pickup apparatus having a live view mode, it is necessary to keep the trailing curtain in the open state by energizing the electromagnet after the spring is put into the overcharged state and the trailing curtain is opened, in the live view mode. However, to continue the energization of the electromagnet in the period for which the shutter curtain (trailing curtain) is open in the live view mode is not desirable from the viewpoint of electric power saving. 
         [0020]    Thus, there is a need for a shutter device which promises power saving in realizing both a condition where a spring is overcharged and a trailing curtain is present in an opening position for a shutter aperture and a condition where the spring is overcharged and the trailing curtain is present in a closing position for the shutter aperture, and a technology pertaining to the shutter device. 
         [0021]    According to an embodiment of the present invention, there are provided a shutter device and an image pickup apparatus using the shutter device, the shutter device including: a trailing curtain operative to run from an exposure start position to an exposure end position to cover an exposure aperture; a first driving member operative to cause the trailing curtain to run from the exposure start position to the exposure end position; a second driving member operative to cause the trailing curtain to run from the exposure end position to the exposure start position; first urging force applying means by which a first urging force for moving the trailing curtain in a first direction from the exposure start position toward the exposure end position is applied to the first driving member; and a charging member which moves the first driving member in a predetermined direction so as to overcharge the first urging force applying means and thereby to increase the first urging force. In the shutter device, the charging member moves the first driving member in the predetermined direction while restraining movement of the second driving member, so as to overcharge the first urging force applying means while maintaining a closed state of the aperture formed by the trailing curtain and thereby to transfer the shutter device into a first set condition, and, in the first set condition, makes contact with the first driving member to restrain movement of the first driving member; and the charging member, in the closed state of the aperture formed by the trailing curtain, releases the restraint-on movement of the second driving member to permit the second driving member to move, while moving the first driving member in the predetermined direction, so as to form an open state of the aperture by the trailing curtain while overcharging the first urging force applying means and thereby to transfer the shutter device into a second set condition, and, in the second set condition, makes contact with the first driving member to restrain movement of the first driving member. 
         [0022]    According to another embodiment of the present invention, there are provided a shutter device and an image pickup apparatus using the shutter device, the shutter device including: a trailing curtain operative to run from an exposure start position to an exposure end position to cover an exposure aperture; a first driving member to which a first urging force is applied by first urging force applying means and which causes the trailing curtain to run from the exposure start position to the exposure end position by the first urging force; a second driving member which, on one hand, moves together with the first driving member so as to cause the trailing curtain to run from the exposure start position to the exposure end position and, on the other hand, moves independently of the first driving member so as to cause the trailing curtain to run from the exposure end position to the exposure start position; and a charging member which moves the first driving member in a predetermined direction so as to overcharge the first urging force applying means and thereby to increase the first urging force. In the shutter device, the charging member moves the first driving member in the predetermined direction while restraining movement of the second driving member, so as to overcharge the first urging force applying means while maintaining a closed state of the aperture formed by the trailing curtain and thereby to transfer the shutter device into a first set condition, and, in the first set condition, makes contact with the first driving member to restrain movement of the first driving member; and the charging member, after transfer to the first set condition, releases the restraint on movement of the second driving member to permit the second driving member to move, maintains an overcharged state of the first urging force applying means, while forming an open state of the aperture by the trailing curtain, so as to transfer the shutter device into a second set condition, and, in the second set condition, makes contact with the first driving member to restrain movement of the first driving member. 
         [0023]    According to a further embodiment of the present invention, there are provided a shutter device and an image pickup apparatus using the shutter device, the shutter device including: a trailing curtain operative to run from an exposure start position to an exposure end position to cover an exposure aperture; a first driving member to which a first urging force is applied by first urging force applying means and which causes the trailing curtain to run from the exposure start position to the exposure end position by the first urging force; a second driving member which, on one hand, moves together with the first driving member so as to cause the trailing curtain to run from the exposure start position to the exposure end position and, on the other hand, moves independently of the first driving member so as to cause the trailing curtain to run from the exposure end position to the exposure start position; and a charging member which moves the first driving member in a predetermined direction so as to overcharge the first urging force applying means and thereby to increase the first urging force. In the shutter device, the charging member moves the first driving member in the predetermined direction while restraining movement of the second driving member, so as to overcharge the first urging force applying means while maintaining a closed state of the aperture formed by the trailing curtain and thereby to transfer the shutter device into a first set condition; and the charging member, after transfer to the first set condition, releases the restraint on movement of the second driving member to permit the second driving member to move, maintains an overcharged state of the first urging force applying means, while forming an open state of the aperture by the trailing curtain, so as to transfer the shutter device into a second set condition, and, in the second set condition, makes contact with the first driving member to restrain movement of the first driving member. 
         [0024]    According to the just-mentioned embodiments of the present invention, both a condition where the spring is overcharged and the trailing curtain is present in the opening position for the exposure aperture and a condition where the spring is overcharged and the trailing curtain is present in the closing position for the exposure aperture can be realized without energization of an electromagnet. This promises savings of electric power. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]      FIG. 1  is a front appearance view of an image pickup apparatus; 
           [0026]      FIG. 2  is a rear appearance view of the image pickup apparatus; 
           [0027]      FIG. 3  is a block diagram showing the functional configuration of the image pickup apparatus; 
           [0028]      FIG. 4  is a sectional view of the image pickup apparatus (mirror-down condition); 
           [0029]      FIG. 5  is a sectional view of the image pickup apparatus (mirror-up condition); 
           [0030]      FIG. 6  is a schematic view showing the configuration of a shutter device; 
           [0031]      FIG. 7  is an enlarged view showing a part of the shutter device (aperture closed state); 
           [0032]      FIG. 8  is an enlarged view showing a part of the shutter device (aperture open state); 
           [0033]      FIG. 9  is a view showing a component part of a driving mechanism; 
           [0034]      FIG. 10  is a view showing another component part of the driving mechanism; 
           [0035]      FIG. 11  is a view showing a further component part of the driving mechanism; 
           [0036]      FIG. 12  is a sectional view of the driving mechanism; 
           [0037]      FIG. 13  is a view showing a driving section for driving a charging member; 
           [0038]      FIG. 14  is a view showing the driving section for driving the charging member; 
           [0039]      FIG. 15  is a view showing a series of operations of the driving mechanism (a condition immediately upon end of exposure); 
           [0040]      FIG. 16  is a view showing a series of operations of the driving mechanism (a first set condition); 
           [0041]      FIG. 17  is a view showing a series of operations of the driving mechanism; 
           [0042]      FIG. 18  is a view showing a series of operations of the driving mechanism (a second set condition); 
           [0043]      FIG. 19  is a view showing a series of operations of the driving mechanism (a condition immediately before start of exposure); 
           [0044]      FIG. 20  is a time chart pertaining to a shooting operation at the time of a live view mode; and 
           [0045]      FIG. 21  is a time chart showing an operation pertaining to Comparative Example. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0046]    Now, embodiments of the present invention will be described below, based on the attached drawings. 
         [0047]    &lt;1. Outline of Configuration&gt; 
         [0048]      FIGS. 1 and 2  are views showing appearance configurations of an image pickup apparatus  1  according to an embodiment of the present invention. Here,  FIG. 1  is a front appearance view of the image pickup apparatus  1 , and  FIG. 2  is a rear appearance view of the image pickup apparatus  1 . The image pickup apparatus  1  is configured as a lens-interchangeable single reflex type digital camera. 
         [0049]    As shown in  FIG. 1 , the image pickup apparatus  1  has a camera body  2 . An interchangeable photographing lens unit (interchangeable lens)  3  can be mounted to and dismounted from the camera body  2 . 
         [0050]    The photographing lens unit  3  is composed mainly of a lens barrel  3   c,  a lens group  3   e  (see  FIG. 3 ) provided inside the lens barrel  3   c,  and a diaphragm and the like. The lens group  3   e  (photographing optical system) includes a focus lens which is moved in an optical axis direction to vary the focal point position and the like. 
         [0051]    The camera body  2  is provided, in a substantially central area of a front surface thereof, with an annular mount part Mt to which the photographing lens unit  3  is mounted. 
         [0052]    In addition, the camera body  2  is provided with a mode setting dial  15  in a right upper area of the front surface thereof. By operating the mode setting dial  15 , it is possible to set (switch) various modes of camera (inclusive of “shooting mode” for obtaining a real shot image(s), “reproduction mode” for reproducing the shot image(s), and “communication mode” for data communication with external apparatuses). 
         [0053]    Besides, the camera body  2  is provided, in a left end area of the front surface thereof, with a grip part  14  to be gripped by the user. A release button  11  for instructing the start of exposure is provided at an upper surface of the grip part  14 . A battery compartment and a card compartment are provided inside the grip part  14 . A battery such as a lithium ion battery is contained in the battery compartment as a power source for the camera, and a memory card  90  (see  FIG. 3 ) for recording image data of shot images is removably contained in the card compartment. 
         [0054]    The release button  11  is-a two-stage detection button capable of detection of two states, i.e., a half-depressed state (S 1  state) and a full-depressed state (S 2  state). When the release button  11  is half pressed into the S 1  state, a preparatory operation (e.g., an AF (auto focus) control operation, etc.) for obtaining a recording still image (real shot image) relevant to a subject is carried out. In addition, when the release button  11  is further pressed into the S 2  state, a shooting (photographing) operation for obtaining the real shot image is carried out Specifically, an exposure operation relating to a subject image (a light image of the subject) is performed using an image sensor  5  (described later), and a series of operations for subjecting an image signal obtained by the exposure operation to predetermined image processings are carried out. Thus, the image pickup apparatus  1  determines that a shooting preparation command is inputted when the release button  11  is put into the half-depressed state S 1 , and determines that a shooting command is inputted when the release button  11  is put into the full-depressed state S 2 . 
         [0055]    In  FIG. 2 , a finder window (ocular window)  10  is provided in a substantially upper central area of the back surface of the camera body  2 . By peeping into the finder window  10 , the user can visually check the light image of the subject led through the photographing lens unit  3 , thereby framing (deciding a composition). Thus, framing can be performed using an optical finder. 
         [0056]    In  FIG. 2 , a back monitor  12  is provided in a substantially central area of the back surface of the camera body  2 . The back monitor  12  is configured as a color liquid crystal display (LCD), for example. 
         [0057]    On the back monitor  12 , a menu screen for setting shooting conditions and the like can be displayed, and a shot image or images recorded in a memory card  90  can be reproducedly displayed in the reproduction mode. 
         [0058]    In addition, on the back monitor  12 , a plurality of time-series images (i.e., motion picture images) obtained by the image sensor  5  (described later) can be sequentially displayed as live-view images. In the image pickup apparatus  1  according to this embodiment, framing can be conducted using the live-view images displayed on the back monitor  12 . 
         [0059]    A power switch (main switch)  16  is provided on the left upper side of the back monitor  12 . The power switch  16  is a two-contact-position slide switch; when the contact is set to an “OFF” position on the left side, a power source is turned OFF, and when the contact is set to an “ON” position on the-right side, the power source is turned ON. 
         [0060]    A direction selector key  18  is provided on the right side of the back monitor  12 . The direction selector key  18  has a circular operating button. In the operating button, a pressing operation in any of four directions composed of upward, downward, leftward and rightward directions or a pressing operation in any of four directions composed of upwardly rightward, upwardly leftward, downwardly rightward and downwardly leftward directions is detected individually. Incidentally, in the direction selector key  18 , a pressing operation on a central pushbutton is detected, separately from the pressing operation in any of the just-mentioned eight directions. 
         [0061]    &lt;2. Functional Blocks of Image Pickup Apparatus&gt; 
         [0062]    Now, referring to  FIG. 3 , an outline of functions of the image pickup apparatus  1  will be described below.  FIG. 3  is a block diagram showing the functional configuration of the image pickup apparatus  1 . 
         [0063]    As shown in  FIG. 3 , the image pickup apparatus  1  has an AF module  20 , a general control section  101 , a focus control section  121 , a mirror control section  122 , a shutter control section  123 , a digital signal processing circuit  53 , etc. 
         [0064]    The general control section  101 , in cooperation with the AF module  20  and the focus control section  121  and the like, performs a focus control operation for controlling the position of the focus lens. 
         [0065]    The general control section  101  is configured as a microcomputer, and mainly has a CPU (central processing unit), a memory, and ROM (read only memory) (for example, EEPROM (electrically erasable and programmable read only memory)), etc. The general control section  101  reads programs stored in the ROM, and executes the programs, thereby realizing various functions. 
         [0066]    The AF module  20  is capable of detecting a focused state of a subject by a focused state detecting technique based on a phase difference system, using the light coming in thereto through a mirror mechanism  6 . According to the focused state of the subject detected by the AF module  20 , the general control section  101  realizes an AF operation by use of the focus control section  121 . Particularly, by use of the AF module  20  of the phase difference system, a focusing lens position can be obtained at a very high speed. 
         [0067]    The focus control section  121  realizes a focus control operation by cooperation with the general control section  101 . Specifically, the focus control section  121  produces a control signal on the basis of a signal inputted thereto from the general control section  101 , and moves the focus lens included in the lens group  3   e  disposed in the photographing lens unit  3 . In addition, the position of the focus lens is detected by a lens position detecting section  3   d  in the photographing lens unit  3 , and data indicative of the position of the focus lens is sent to the general control section  101 . In this manner, the focus control section  121  controls movements of the focus lens in the optical axis direction, etc. 
         [0068]    Besides, the mirror control section  122  controls switching between a condition where the mirror mechanism  6  is retracted from the optical path (mirror-up condition) and a condition where the mirror mechanism  6  is shutting off the optical path (mirror-down condition). The mirror control section  122  produces a control signal on the basis of a signal inputted thereto from the general control section  101 , thereby switching between the mirror-up condition and the mirror-down condition. 
         [0069]    The shutter control section  123  produces a control signal on the basis of a signal inputted thereto from the general control section  101 , thereby controlling the operation of a shutter device  7 . 
         [0070]    The shutter device  7  is disposed at a position on the subject side of, and close to, the image sensor  5 . The shutter device  7  is a so-called focal plane shutter. The shutter device  7  is arranged to be substantially perpendicular to the optical axis of the photographing lens unit  3 . Specifically, the shutter device  7  is so arranged that the center position of its aperture. (opening) OP (described later) lies on the optical axis of the photographing lens unit  3 . 
         [0071]    In addition, on the back side of the shutter device  7 , the image sensor  5  is arranged to be substantially perpendicular to the optical axis of the photographing lens unit  3 . 
         [0072]    The image sensor (here, a CMOS sensor)  5  is a light receiving element by which a light image of subject (subject image) coming from the photographing lens unit  3  is converted into an electrical signal by a photo-electric conversion action, and produces (obtains) an image signal relevant to a real shot image (an image signal for recording). Besides, the image sensor  5  obtains live-view images, too. 
         [0073]    In response to drive control signals (an accumulation start signal and an accumulation end signal) from the general control section  101 , the image sensor  5  performs exposure to a subject image formed on an image forming plane (accumulation of electric charges through photo-electric conversion), so as to produce an image signal relevant to the subject image. In addition, the image sensor  5  outputs the image signal to a signal processing section  51 , in response to a reading control signal supplied from the general control section  101 . 
         [0074]    When the image signal obtained at the image sensor  5  is subjected to a predetermined analog signal processing by the signal processing section  51 , the image signal obtained upon the analog signal processing is converted into digital image data (image data) by an A/D (analog/digital) conversion circuit  52 . The image data is inputted to the digital signal processing circuit  53 . 
         [0075]    In the digital signal processing circuit  53 , the image data inputted from the A/D conversion circuit  52  is subjected to digital signal processing, to produce image data relevant to a shot image. The digital signal processing circuit  53  includes a black level correction circuit, a white balance (WB) circuit, a γ correction circuit, etc., and performs various digital image processing. Incidentally, an image signal (image data) obtained upon processings by the digital signal processing circuit  53  is stored into an image memory  55 . The image memory  55  is a high-speed accessible image memory for temporarily storing the image data thus produced, and has a capacity sufficient to store the image data in an amount corresponding to a plurality of frames. 
         [0076]    At the time of real shooting, the image data temporarily stored in the image memory  55  is subjected to appropriate image processings (compression, etc.) in the general control section  101 , before being stored into the memory card  90 . 
         [0077]    In addition, at the time of live view, time-series images (live-view images) obtained by the image sensor  5  and temporarily stored in the image memory  55  are sequentially displayed on the back monitor  12 . 
         [0078]    &lt;3. Outline of Shooting Operation&gt; 
         [0079]    As has been mentioned above, in the image pickup apparatus  1 , framing (deciding a composition) can be performed using the optical finder (referred to also as optical viewfinder (OVF)) composed of a finder optical system or the like. 
         [0080]    Besides, in the image pickup apparatus  1 , framing can also be performed using live-view images displayed on the back monitor  12 . Incidentally, the finder function realized by utilizing the back monitor  12  includes a process in which the light image of a subject is converted into electronic data and thereafter the electronic data is visualized, and, therefore, this finder function is referred to also as electronic viewfinder (EVF). 
         [0081]    The OVF-based framing mode (OVF mode) and the EVF-based framing mode (EVF mode) are changed over by an appropriate changeover switch (not shown). 
         [0082]      FIGS. 4 and 5  are sectional views of the image pickup apparatus  1 .  FIG. 4  shows a mirror-down condition, while  FIG. 5  shows a mirror-up condition. 
         [0083]    As shown in  FIGS. 4 and 5 , the mirror mechanism  6  is provided on the optical path (photographing optical path) extending from the photographing lens unit  3  to the image sensor  5 . The mirror mechanism  6  has a main mirror  6   a  (main reflecting surface) by which the light coming from the photographing optical system is reflected to the upper side. The main mirror  6   a  is partly or entirely composed as a half mirror, through which part of the light coming from the photographing optical system is transmitted. In addition, the mirror mechanism  6  has also a sub mirror  6   b  (sub reflecting surface) by which the light transmitted through the main mirror  6   a  is reflected to the lower side. The light reflected to the lower side by the sub mirror  6   b  is guided to and incident on the AF module  20 , to be utilized for the AF operation based on the phase difference system. 
         [0084]    In the OVF mode, the mirror mechanism  6  is arranged to be in the mirror-down condition until the release button  11  is put into the full-depressed state S 2  (namely, during framing) ( FIG. 4 ). In this case, the subject image coming from the photographing lens unit  3  is reflected to the upper side by the main mirror  6   a,  to be incident on a penta prism  65  as an observation luminous flux, which is further reflected by the penta prism  65  and passes through an eyepiece  67  and the finder window  10 , to reach the user&#39;s eye. In this manner, framing by use of the optical viewfinder (OVF) is carried out. 
         [0085]    Thereafter, when the release button  11  is put into the full-depressed state S 2 , the mirror mechanism  6  is driven to come into the mirror-up condition, and an exposure operation is started (see  FIG. 5 ). Specifically, as shown in  FIG. 5 , at the time of exposure, the mirror mechanism  6  is retracted (evacuated) from the photographing optical path. To be more specific, the main mirror  6   a  and the sub mirror  6   b  are retracted to the upper side so as not to intercept the light (subject image) coming from the photographing optical system, so that the light coming from the photographing lens unit  3  travels without being reflected by the main mirror  6   a,  and reaches the image sensor  5  in conformity with an open period of the shutter device  7 . The image sensor  5  performs photo-electric conversion to thereby produce an image signal relevant to the subject, based on the luminous flux received. In this manner, the luminous flux from the subject (subject image) is transmitted through the photographing lens unit  3  and guided to the image sensor  5 , whereby a shot image relevant to the subject (shot image data) is obtained. 
         [0086]    On the other hand, in the EVF mode (referred to also as live view mode), the following operations are performed. 
         [0087]    Specifically, the mirror mechanism  6  is arranged to be in the mirror-up condition until the release button  11  is put into the full-depressed state S 2  (namely, at the time of framing) ( FIG. 5 ). In this case, the subject image coming from the photographing lens unit  3  advances straight, without being reflected by the main mirror  6   a,  to be incident on the image sensor  5 . 
         [0088]    Then, based on the subject image incident on the image sensor  5 , the image sensor  5  sequentially obtains time-series images (live-view images) concerning the subject. Specifically, the image sensor  5  sequentially produces a plurality of images at a very short time interval (for example, 1/60 second). The time-series images thus obtained are sequentially displayed on the back monitor  12 . This enables the user to visually check the motion picture (live-view images) displayed on the back monitor  12 , and to conduct framing by use of the motion picture. In this manner, framing by use of the live-view images can be performed. 
         [0089]    Thereafter, when the release button  11  is put into the full-depressed state S 2 , an electronic leading curtain and a mechanical trailing curtain (described later) are made to run, whereby an exposure operation is carried out. Then, based on the subject images reaching the image sensor  5  during the open period of the shutter device  7 , an image signal relevant to the subject is produced by the photo-electric conversion action of the image sensor  5 . In this manner, the luminous flux coming from the subject (subject image) is passed through the photographing lens unit  3  and guided to the image sensor  5 , whereby a real shot image concerning the subject (shot image data) is obtained. Further, thereafter, the live-view display is restarted. 
         [0090]    &lt;4. Configuration of Shutter Device&gt; 
         [0091]      FIG. 6  is a schematic view showing the configuration of the shutter device  7 .  FIGS. 7 and 8  are enlarged views showing a part of the shutter device  7  (the left side of  FIG. 6 ). Incidentally, in  FIGS. 6 to 8 , the configuration of a trailing curtain (described below) and the like are mainly shown, and the configuration of a driving mechanism  80  (described below) and the like are omitted. 
         [0092]    In this image pickup apparatus  1 , a so-called “electronic leading curtain” is utilized as a leading curtain in the shutter device  7 . For example, an operation in which resetting actions on the basis of a predetermined unit (e.g., line) in the image sensor  5  are sequentially carried out in a predetermined direction corresponds to a “running operation” of the electronic leading curtain. Then, as if chasing after the leading end position of the “electronic leading curtain which is running,” the mechanical trailing curtain runs, whereby the exposure operation in the very short period is realized. In this instance, paying attention to a certain pixel in the image sensor (e.g., CMOS)  5 , the exposure operation relevant to the pixel is carried out over a period TM(=T 2 −T 1 ) from the time T 1  immediately after the setting (cocking) operation at the image sensor  5  to the time T 2  when the “trailing curtain” covers the pixel to intercept the light. The length of this period TM (for example, 1/100 second) corresponds to the shutter speed. 
         [0093]    Besides, of a leading curtain and a trailing curtain, only the trailing curtain is mechanically provided in the shutter device  7 , and the leading curtain is not provided mechanically. 
         [0094]    As shown in  FIG. 6 , the shutter device  7  has a shutter base plate  71 , a group of trailing blades  73   a,    73   b,    73   c,  and arms  75   a,    75   b.  In addition, the shutter device  7  has an auxiliary base plate  72  (see  FIG. 12 ) substantially the same in shape as the shutter base plate  71 , on the back side of the shutter base plate  71 . Both the base plates  71  and  72  are provided to face each other, with a predetermined gap therebetween. The gap between the base plates  71  and  72  is a space for accommodating the trailing blades  73   a,    73   b,    73   c  and, therefore, referred to also as “blade chamber.” 
         [0095]    The shutter base plate  71  has the aperture OP (see also  FIG. 8 , etc.) for exposure in a substantially central area thereof. Similarly, the auxiliary base plate  72  also has an aperture (opening) OP for exposure in a substantially central area thereof. The aperture OP in the shutter base plate  71  and the aperture OP in the auxiliary base plate  72  have substantially the same shape (substantially rectangular shape) and are provided at mutually corresponding positions. These apertures are integrated with each other in an assembled state of the shutter device  7 , to form an exposure aperture (opening) OP of the shutter device  7 . 
         [0096]    In addition, the shutter base plate  71  is provided with two circular arc-shaped slots  71   g,    71   h  (see  FIG. 7 ). The slot  71   g  is provided along an arc of a circle having a center on an axis AX 3  (described later) (see  FIG. 15 ) and a predetermined radius r 1 , and the slot  71   h  is provided along an arc of a circle having a center on an axis AX 1  (described later) and a predetermined radius r 2 . 
         [0097]    The trailing blades  73   a,    73   b,    73   c  are provided between the shutter base plate  71  and the auxiliary base plate  72 . In other words, the trailing blades  73   a,    73   b,    73   c  are provided on the rear side of the shutter base plate  71 . Each of the trailing blades  73   a,    73   b,    73   c  is a sheet-like member having a light-shielding property. The trailing blades  73   a,    73   b,    73   c  constitute the “trailing curtain.” Incidentally, while the case where the “trailing curtain” is composed of three trailing blades  73   a,    73   b,    73   c  is described as an example here, this configuration is not limitative; for example, the trailing curtain may be composed of up to two blades or composed of four or more blades. 
         [0098]    Each of the trailing blades  73   a,    73   b,    73   c  is rotatably connected to an arm  75   a,  and is rotatably connected also to an arm  75   b.  The arm  75   a  can be turned about an axis AX 5 , and the arm  75   b  can be turned about an axis AX 4 . Incidentally, here, the axis AX 4  is the same as the axis AX 1  (described later). 
         [0099]    As shown in  FIGS. 6 and 7 , when the arm  75   a  and the arm  75   b  are present at predetermined positions, the trailing curtain composed of the trailing blades  73   a,    73   b,    73   c  is closing the aperture OP, so that a “closed state of the aperture OP” formed by the trailing curtain is realized. On the other hand, when the arm  75   b  is rotated counterclockwise about the axis AX 4  starting from the just-mentioned condition, the arm  75   a  is also rotated counterclockwise about the axis AX 5 , whereby the trailing curtain composed of the trailing blades  73   a,    73   b,    73   c  is retracted from the aperture OP, as shown in  FIG. 8 . In other words, an “open state of the aperture OP” formed by the trailing curtain is realized. On the contrary, when the arm  75   b  is rotated clockwise about the axis AX 4  starting from the condition shown in  FIG. 8 , the arm  75   a  is also rotated clockwise about the axis AX 5 , whereby transition to the “closed state of the aperture OP” shown in  FIG. 7  is effected. 
         [0100]    Incidentally, the position of each of the trailing blades  73   a,    73   b,    73   c  in  FIG. 7  is also called “exposure end position,” and the position of each of the trailing blades  73   a,    73   b,    73   c  in  FIG. 8  is also called “exposure start position.” The “trailing curtain” covers the aperture OP ( FIG. 7 ) upon running from the exposure start position to the exposure end position, and opens the aperture OP ( FIG. 8 ) upon running from the exposure end position to the exposure start position. In other words, at the exposure start position, the aperture OP is not covered by the trailing curtain but is open, whereas at the exposure end position, the aperture OP is covered by the trailing curtain. 
         [0101]    In addition, the arms  75   a,    75   b  and the trailing curtain are driven by the driving mechanism  80  which will be described below.  FIGS. 9 to 11  are views showing some component parts  81 ,  82 ,  83  of the driving mechanism  80 .  FIG. 12  is a sectional view taken along line I-I of the plan view in  FIG. 15 .  FIGS. 13 and 14  are schematic views showing a mechanism  85  for driving the component part (charging member)  83 . Besides,  FIGS. 15 to 19  are plan views showing a series of operations of the driving mechanism  80 . Incidentally, in  FIGS. 15 to 19 , the driving mechanism  80  is mainly shown, and the trailing curtain (trailing blades  73   a,    73   b,    73   c ) and the like are omitted. 
         [0102]    As shown in  FIG. 15 , the driving mechanism  80  has a driving member  81  ( FIG. 9 ), a driving member  82  ( FIG. 10 ), and the charging member  83  ( FIG. 11 ). 
         [0103]    The driving members  81 ,  82  and the charging member (referred to also as setting (cocking) member)  83  are provided on the front side (on the viewer&#39;s side of the paper surface of  FIGS. 6 and 15 , etc.) of the shutter base plate  71 . 
         [0104]    The driving member  81  is a substantially plate-like rotary body which can be turned about the axis AX 1 , and the driving member (referred to also as operating member)  82  is a substantially plate-like rotary body which can be turned about an axis AX 2 . Here, both the driving members  81  and  82  are provided to be turnable about the same axis AX 1  (in other words, AX 2 =AX 1 ). Incidentally, the driving member  81  is provided on the viewer&#39;s side of the paper surface, in relation to the driving member  82 . 
         [0105]    A body-side member (a predetermined member erectly provided on the shutter base plate  71 ) and the driving member  81  in the shutter device  7  are connected to each other through a spring  88  (see  FIG. 12 ), and a clockwise urging force is applied to the driving member  81  by the spring  88 . 
         [0106]    In addition, a body-side member (a predetermined member erectly provided on the shutter base plate  71 ) and the driving member  82  in the shutter device  7  are connected to each other through a spring  89  (see  FIG. 15 ), and a counterclockwise urging force is applied to the driving member  82  by the spring  89 . 
         [0107]    Here, the urging force applied by the spring  88  is greater than the urging force applied by the spring  89 . In other words, the counterclockwise driving force exerted by the driving member  82  is smaller than the clockwise driving force exerted by the driving member  81 . Therefore, when the driving force by the driving member  81  is exerted in an “unlocked condition” ( FIG. 19 ) described later, the driving member  82  is rotated clockwise about the axis AX 1  together with the driving member  81  by the urging force applied by the spring  88 . Thus, the driving member  81  can cause the “trailing curtain” to run from the exposure start position to the exposure end position, by use of the urging force applied by the spring  88 . Besides, particularly, the driving member  81  is rotated counterclockwise before the start of running of the “trailing curtain,” whereby the clockwise urging force of the spring  88  is increased further. This condition is expressed also as the condition where the spring  88  is overcharged (described later). With the spring  88  thus overcharged, it is possible to rotationally move the driving member  81  and the driving member  82  at a very high speed, and to move the trailing curtain at a very high speed. 
         [0108]    On the other hand, as will be described later, the driving member  82  can also be rotated independently of the driving member  81 . For example, during rotation (specifically, during counterclockwise rotation) of the driving member  81 , the counterclockwise rotation of the driving member  81  is completed in the condition where rotational movement of the driving member  82  is restrained ( FIG. 16 ). Then, after completion of the rotation of the driving member  81 , the driving member  82  is rotated counterclockwise independently of the driving member  81  ( FIG. 18 ). In this instance, the driving member  82  can cause the “trailing curtain” to run from the exposure end position to the exposure start position, by use of the urging force applied by the spring  89 . In this manner, the driving member  82  can cause the trailing curtain to run in the direction opposite to the direction of driving by the driving member  81 . 
         [0109]    As shown in  FIG. 12 , the driving member  81  is provided in the manner of being stacked over the driving member  82 . Specifically, the shutter base plate  71  is erectly provided with a shaft member  86  extending substantially vertically toward the upper side in  FIG. 12 , and a hole  81   h  formed in the driving member  81  is in fit (free fit) over the shaft member  86 . This configuration enables the driving member  81  to be turned about the shaft member  86  (more specifically, about the center axis AX 1  of the shaft member  86 ). 
         [0110]    Specifically, the driving member  81  has a plate part  81   p  and a shaft part  81   u.  The shaft part  81   u  is provided in the periphery of the hole  81   h  so as to fit over the shaft member  86 . The shaft part  81   u  has a flange part  81   v,  a large diameter part  81   x,  an intermediate diameter part  81   y,  and a small diameter part  81   z,  in this order from the side of the shutter base plate  71  (the lower side in  FIG. 12 ) toward the upper side. 
         [0111]    The above-mentioned spring (specifically, torsion spring)  88  is provided in the state of being wound around the small diameter part  81   z.    
         [0112]    The intermediate diameter part  81   y  is in “interference fit” in a hole  81   f  formed in the plate part  81   p  of the driving member  81 , whereby the plate part  81   p  and the shaft part  81   u  are united. 
         [0113]    The large diameter part  81   x  is in “clearance fit” (free fit) in a hole  82   h  formed in the driving member  82 , so that the driving member  82  can be turned about the same axis as the rotational axis AX 1  for the large diameter part  81   x.  In other words, the driving member  82  can be turned about the above-mentioned shaft member  86  (more specifically, about the center axis AX 1  of the shaft member  86 ). 
         [0114]    In addition, as shown in  FIG. 9 , the plate part  81   p  of the driving member  81  has a substantially sector-like shape in plan view. 
         [0115]    The plate part  81   p  has a projected part  81   b  at a radius part on one side (the upper side in  FIG. 9 ), of two radius parts of the substantially sector-like shape. The projected part  81   b  is projected from a back surface of the plate part  81   p  further to the depth side (back side). As will be described later, the projected part  81   b  comes into contact with a contact surface  82   f  of the driving member  82  to which a counterclockwise urging force is applied, so that counterclockwise rotation of the driving member  82  is restricted by the projected part  81   b.    
         [0116]    Besides, the plate part  81   p  has a contact surface  81   e  at a radius part on the other side (the lower side in  FIG. 9 ), of the two radius parts of the substantially sector-like shape. As will be described later, the contact surface  81   e  makes contact with an arm part  83   b  of the charging member  83  at the time of an overcharging operation (described later) concerning the spring  88 . A rotational driving force supplied from the charging member  83  is transmitted through the arm part  83   b  and the contact surface  81   e,  whereby the overcharging operation relating to the spring  88  is performed. 
         [0117]    Further, the plate part  81   p  has a projected part  81   c  in the vicinity of an outer peripheral part of the substantially sector-like shape. The projected part  81   c  is projected from the front surface of the plate part  81   p  further to the front side (the viewer&#39;s side of the paper surface of  FIG. 9 ). An iron piece member  81   d  is fixed to the projected part  81   c.  In addition, an electromagnet  95  is provided at the same position (or the same height) as the iron piece member  81   d  in the height direction in  FIG. 12 . When the driving member  81  has a rotational angle shown in  FIG. 19  (described later), the iron piece member  81   d  facing the electromagnet  95  can be attracted onto the electromagnet  95  by the electromagnet  95 . As will be described later, therefore, by the attraction of the iron piece member  81   d  by the electromagnet  95 , also, the rotational movement of the driving member  81  can be restrained (see  FIG. 19 ). 
         [0118]    As shown in  FIG. 10 , the driving member  82  has a substantially sector-like shape, like the driving member  81 . 
         [0119]    The driving member  82  has a contact surface  82   f  at a radius part on one side (the upper side in  FIG. 10 ), of two radius parts of the substantially sector-like shape. 
         [0120]    In addition, the driving member  82  has a link pin  82   a  on the side of an outer peripheral part of the substantially sector-like shape. The link pin  82   a  is provided to project from the back surface of the driving member  82  further to the depth side (back side). Particularly, the link pin  82   a  is provided to penetrate the slot  71   h  in the shutter base plate  71  and a hole  75   h  formed in the arm  75   b  (see  FIGS. 12 and 15 ). Besides, in the circular arc direction (longitudinal direction) of the circular arc-shaped slot  71   h,  the diameter of the hole  75   h  and the diameter of the link pin  82   a  are approximately equal. Therefore, when the link pin  82   a  is moved attendant on a turning motion of the driving member  82  about the axis AX 1 , the arm  75   b  is turned about the axis AX 4  by the link pin  82   a,  whereby moving operations of the trailing blades  73   a,    73   b,    73   c,  or opening and closing operations of the “trailing curtain” are realized. Thus, the “trailing curtain” is operated in conjunction with the link pin  82   a,  whereby a closed condition of  FIG. 7  and an open condition of  FIG. 8  are realized. 
         [0121]    Further, the driving member  82  has a circular arc-shaped projected part  82   b  on the side of a outer peripheral part of the substantially sector-like shape. The circular arc-shaped projected part  82   b  is projected from the front surface of the driving member  82  further to the front side (the viewer&#39;s side of the paper surface of  FIG. 10 ). A contact surface  82   n,  which is a side surface on the axis AX 1  side of the circular arc-shaped projected part  82   b,  is formed so as to constitute a part of an arc of a circle having a center on the rotational center axis AX 3  of the charging member  83  and a radius equal to a predetermined length r 3  (see  FIG. 15 , also). As will be described later, by the contact of a contact surface  83   n  of an engaging part  83   c  of the charging member  83  with the contact surface  82   n  of the circular arc-shaped projected part  82   b  of the driving member  82 , counterclockwise rotation of the driving member  82  is restrained. 
         [0122]    As shown in  FIG. 11 , the charging member  83  is a rotary body which can be turned about the axis AX 3 . Specifically, as shown in  FIG. 15 , the shutter base plate  71  is erectly provided, at a plan-view position different from that of the shaft member  86 , with a shaft member  87  extending substantially perpendicularly toward the viewer&#39;s side of the paper surface of the figure. In addition, a hole  83   h  ( FIG. 11 ) in the charging member  83  is in fit (free fit) over the shaft member  87 . Such a configuration enables the charging member  83  to be turned about the shaft member  87  (more specifically, about the center axis AX 3  of the shaft member  87 ). 
         [0123]    Besides, the charging member  83  is provided with a recessed part  83   v.  A tip part  84   p  (see  FIG. 13 ) of a link member  84  mechanically connected to a predetermined drive source (motor or the like)  85   d  (not shown) is engaged with the recessed part  83   v.    
         [0124]      FIG. 13  is a sectional view taken along line II-II of  FIG. 11 . As shown in  FIG. 13 , a cam  85   c  is provided to be turnable about a shaft  85   b  connected to the drive source  85   d.  In addition, the link member  84  is provided at such a position as to make contact with an outer peripheral surface of the cam  85   c.  The link member  84  is provided in the state of being turnable about an axis AX 6  and being urged counterclockwise. By this urging force, the link member  84  is pressed against the outer peripheral surface of the cam  85   c.  Therefore, as the cam  85   c  is rotated, the outer peripheral surface of the cam  85   c  is moved while sliding on the link member  84 . 
         [0125]    In this instance, the rotating motion of the cam  85   c  is converted into a swinging motion of the link member  84  about the axis AX 6 . Then, for example when the cam  85   c  is rotated from the state of  FIG. 13  to the state of  FIG. 14 , the tip part  84   p  of the link member  84  is moved toward the left side in  FIG. 14  (toward the lower side in  FIG. 11 ). Incidentally, on the contrary, when the cam  85   c  is rotated from the state of  FIG. 14  to the state of  FIG. 13 , the tip part  84   p  of the link member  84  is moved toward the right side in  FIG. 14  (toward the upper side in  FIG. 11 ). 
         [0126]    Then, when the tip part  84   p  of the link member  84  is moved in the vertical direction in  FIG. 11  (in the direction of double arrow in  FIG. 11 ), the charging member  83  is turned about the axis AX 3 , whereby rotational angle of the charging member  83  is varied. 
         [0127]    In addition, the charging member  83  has an arm part  83   b  projecting outward to the substantially opposite side of the axis AX 3  from the recessed part  83   v.  The substantially plate-like charging member  83  is disposed at the same position (same height) as the driving member  81 , in the vertical direction in  FIG. 12 , and the arm part  83   b  is also disposed at the same height as the driving member  81 . Therefore, as will be described later, when the charging member  83  receives a force from the tip part  84   p  of the link member  84  and is rotated clockwise about the axis AX 3 , the arm part  83   b  of the charging member  83  pushes the contact surface  81   e  of the driving member  81 , to rotationally move the driving member  81  counterclockwise. As a result, the clockwise urging force of the spring  88  is further increased, that is, the spring  88  is overcharged. The arm part  83   b  is expressed also as a “pushing part” which pushes the contact surface  81   e  to move, and the contact surface  81   e  is expressed also as a “pushed part (pushed surface)” which is pushed to move by the arm part  83   b.    
         [0128]    Besides, the charging member  83  has an engaging part  83   c  (see  FIG. 11 ). The engaging part  83   c  is provided at a tip part of the arm part  83   b  so as to project from the back surface of the arm part  83   b  further to the depth side (back side). When the charging member  83  is rotated clockwise about the axis AX 3  with its arm part  83   b  pushing the contact surface  81   e,  the engaging part  83   c  passes through a space between the plate part  81   p  of the driving member  81  and the plate part  82   p  of the driving member  82  (see  FIGS. 12 and 16 ). Specifically, the contact surface  83   n  on the axis AX 3  side of the engaging part  83   c  is moved while making contact with the contact surface  82   n  of the circular arc-shaped projected part  82   b  of the driving member  82 . By this contact, counterclockwise rotation of the driving member  82  is restrained. 
         [0129]    Further, the charging member  83  has a pin  83   e.  The pin  83   e  is provided at a position spaced by about a distance r 2  from the axis AX 3  of the charging member  83  so as to project from the back surface of the charging member  83  further to the depth side (back side). The pin  83   e  is inserted in the slot  71   g  in the shutter base plate  71 . 
         [0130]    To the charging member  83 , a urging force for counterclockwise rotation is applied by a spring  93  (not shown). As shown in  FIG. 15 , by the contact of the pin  83   e  with the lower end of the slot  71   g,  counterclockwise rotation of the charging member  83  is restrained, and the charging member  83  is stopped in a predetermined position. 
         [0131]    &lt;5. Operation of Shutter Device&gt; 
         [0132]    Now, operations of the shutter device  7  will be described below referring to  FIGS. 15 to 19 , etc. 
         [0133]      FIG. 15  shows the condition STa immediately after completion of an exposure operation concerning a certain real shot image, and  FIG. 16  shows a first set (cocked) condition ST 11  (described later). In  FIGS. 15 and 16 , the trailing curtain is present at an exposure end position, and is covering the aperture OP (closed condition (see  FIG. 7 )). On the other hand, in  FIGS. 18 and 19 , the trailing curtain is present at an exposure start position, and is retracted from the aperture OP (open condition (see  FIG. 8 )).  FIG. 18  shows a second set (cocked) condition ST 12  (described later), and  FIG. 19  shows the condition STb immediately before start of an exposure operation concerning the next real shot image. Incidentally,  FIG. 17  shows an intermediate condition between the condition ST 11  shown in  FIG. 16  and the condition ST 12  shown in  FIG. 18 . 
         [0134]    As shown in  FIG. 15 , in the condition STa immediately upon completion of a certain exposure operation, the driving member  81  is being urged clockwise about the axis AX 1  by the urging force of the spring  88 , and its projected part  81   b  is in contact with the contact surface  82   f.  Since the urging force of the spring  88  is greater than the urging force of the spring  89 , a force for rotating the driving member  82  clockwise about the axis AX 1  is applied to the driving member  82  by the driving member  81  through the projected part  81   b  and the contact surface  82   f.  In this instance, the link pin  82   a  of the driving member  82  comes into contact with the lower end of the slot  71   h,  and stops in situ. Therefore, the component parts  81 ,  82 ,  83  are stopped in the states as shown in  FIG. 15 . Incidentally, for absorbing the shock upon collision of the link pin  82   a  on the lower end of the slot  71   h,  a shock absorber is preferably provided at the lower end of the slot  71   h.    
         [0135]    In addition, in  FIG. 15 , the pin  83   e  makes contact with the lower end of the slot  71   g,  counterclockwise rotation of the charging member  83  is thereby restrained, and the charging member  83  is being stopped in a predetermined position. Incidentally, for absorbing the shock upon collision of the pin  83   e  on the lower end of the slot  71   g,  a shock absorber is preferably provided at the lower end of the slot  71   g.    
         [0136]    Now, an operation for transition from the condition STa shown in  FIG. 15  to the condition ST 11  shown in  FIG. 16  will be described below. 
         [0137]    First, the tip part  84   p  of the link member  84  is moved downwards in  FIG. 15  by the drive source  85   d,  and the charging member  83  is rotated clockwise about the axis AX 3 . In this case, the arm part  83   b  pushes the contact surface  81   e,  and a pushing force is transmitted to the driving member  81 . Therefore, by the pushing force transmitted to the contact surface  81   e,  the driving member  81  is rotated counterclockwise about the axis AX 1 . 
         [0138]    It is to be noted here, however, that since the engaging part  83   c  is projecting to the tip side along the clockwise direction as compared with the arm part  83   b,  the contact surface  83   n  of the engaging part  83   c  starts making contact with the contact surface  82   n  of the circular arc-shaped projected part  82   b,  before the arm part  83   b  starts pushing the contact surface  81   e.  Then, as the charging member  83  is further rotated clockwise about the axis AX 3 , the contact surface  83   n  of the engaging part  83   c  is moved along the contact surface  82   n  of the circular arc-shaped projected part  82   b.  In other words, during transition to the first set condition ST 11 , the engaging part  83   c  of the charging member  83  locks the circular arc-shaped projected part  82   b  of the second driving member  82  while moving along the circular arc-shaped projected part  82   b.  Therefore, the driving member  82  is inhibited from rotating counterclockwise about the axis AX 1  in the manner of following up to the driving member  81  under the urging force of the spring  89 . Thus, the engagement of the engaging part  83   c  with the circular arc-shaped projected part  82   b  restrains movement of the driving member  82 . 
         [0139]    Then, when the charging member  83  is rotated clockwise about the axis AX 3  by an angle α 1  (e.g., about 70 degrees) until the condition ST 11  shown in  FIG. 16  is reached, the driving member  81  is rotated counterclockwise about the axis AX 1  by a predetermined angle, to stop in the condition where its contact surface  81   e  is supported by the arm part  83   b.  This makes it possible to further increase the clockwise urging force of the spring  88 , in other words, to further increase the accumulated energy of the spring  88 . That is, spring energy can be charged. In the condition ST 11  shown in  FIG. 16 , the urging force of the spring  88  is further increased as compared with that in the condition STa shown in  FIG. 15 ; therefore, the condition shown in  FIG. 16  is expressed also as the condition where the spring  88  is overcharged. In this manner, an overcharging operation for the spring  88  is carried out. 
         [0140]    During such an overcharging operation, the engaging part  83   c  continues being engaged with the circular arc-shaped projected part  82   b,  so that movement of the driving member  82  is kept restrained. Therefore, the link pin  82   a  of the driving member  82  also is not moved, and the trailing curtain is maintained in the exposure end position. In other words, the closed state of the aperture OP formed by the trailing curtain is maintained. 
         [0141]    As above-mentioned, during the operation for transition from the condition STa to the condition ST 11 , the charging member  83  rotates the first driving member  81  counterclockwise about the axis AX 1  while restraining movement of the second driving member  82 . This makes it possible to overcharge the spring  88  while maintaining the closed state of the aperture OP formed by the trailing curtain, and thereby to transfer the shutter device  7  into the first set condition ST 11 . 
         [0142]    Thus, the condition (the “first set condition”) ST 11  shown in  FIG. 16  is a condition where the spring  88  is overcharged while the closed state of the aperture OP formed by the trailing curtain is maintained. In the first set condition ST 11 , the arm part  83   b  of the charging member  83  is in contact with the driving member  81  and is supporting the driving member  81 , whereby rotational movement of the driving member  81  is restrained. Therefore, the trailing curtain can be maintained in the aperture-closing state, without energizing the electromagnet  95 . When the first set condition ST 11  is utilized particularly in the OVF mode, as will be described later, power saving in a framing operation can be promised. 
         [0143]    Now, an operation for transition from the condition (first set condition) ST 11  shown in  FIG. 16  to the condition (second set condition) ST 12  shown in  FIG. 18  will be described below. 
         [0144]    When the charging member  83 , starting from the condition ST 11  shown in  FIG. 16 , is further rotated clockwise about the axis AX 3  by a predetermined angle α 2  (e.g., about 10 degrees) by a driving operation performed by the drive source  85   d  and the link member  84 , temporary transition to the condition (intermediate condition) shown in  FIG. 17  is brought about. 
         [0145]    In the condition ST 11  shown in  FIG. 16 , the circular arc-shaped projected part  82   b  is in engagement with the engaging part  83   c.  However, when a further rotational movement of the circular arc-shaped projected part  82   b  by the angle α 2  is thereafter effected to establish the condition shown in  FIG. 17 , the circular arc-shaped projected part  82   b  and the engaging part  83   c  are disengaged from each other. Therefore, the locking of the second driving member  82  by the charging member  83  is released, and the driving member  82  starts being rotated counterclockwise about the axis AX 1  by the urging force of the spring  89 . The rotating motion of the driving member  82  is stopped by abutment of the contact surface  82   f  on the projected part  81   b  (see  FIG. 18 ). When the link pin  82   a  is moved along the circular arc-shaped slot  71   h  according to the rotating motion of the driving member  82 , the arm  75   b  is turned counterclockwise about the axis AX 4 (=AX 1 ). This results in that the trailing blades  73   a,    73   b,    73   c  are each moved to an exposure start position (in other words, an opening position for the aperture OP). Thus, an aperture-opening operation of the “trailing curtain” is realized (see  FIGS. 8 and 18 ). 
         [0146]    Besides, in this case, the arm part  83   b  of the charging member  83  continues making contact with the contact surface  81   e  of the driving member  81 , so that the driving member  81  is being supported by the arm part  83   b.  In this manner, rotational movement of the driving member  81  is restrained. 
         [0147]    As above-mentioned, during the operation for transition from the first set condition ST 11  to the second set condition ST 12 , the charging member  83  releases the restraint on movement of the second driving member  82 , while supporting the first driving member  81 . Then, the charging member  83  permits the second driving member  82  to be rotated counterclockwise about the axis AX 1  by the urging force of the spring  89 . By this, the trailing curtain is moved to the exposure start position. As a result, the shutter device  7  can be transferred into the second set condition ST 12  while maintaining the overcharged state of the spring  88  while forming the open state of the aperture OP by the trailing curtain. 
         [0148]    In addition, the condition ST 12  shown in  FIG. 18 , or the “second set condition,” is a condition where the trailing curtain has been brought into the aperture-opening state while keeping the spring  88  overcharged. In the second set condition ST 12 , the arm part  83   b  of the charging member  83  is in contact with the driving member  81  and is supporting the driving member  81 , whereby rotational movement of the driving member  81  is being restrained. Therefore, the trailing curtain can be maintained in the aperture-opening state, without energizing the electromagnet  95 . When the second set condition ST 12  is utilized particularly in the live view mode, power saving in a framing operation can be promised. 
         [0149]    In addition, with only the charging member  83  rotated further by a predetermined angle from the first set condition ST 11 , the engagement between the engaging part  83   c  and the circular arc-shaped projected part  82   b  can be released and the aperture-opening state of the trailing curtain can be realized, while maintaining the support of the driving member  81  by the charging member  83 . In other words, the second set condition ST 12  can be formed by use of a simple configuration. Especially, there is no need to provide a lock member for locking the driving member  81 , separately from the charging member  83 , so that simplification of configuration can be achieved. 
         [0150]    Now, an operation for transition from the condition (second set condition) ST 12  shown in  FIG. 18  to the condition (condition immediately before start of exposure) STb shown in  FIG. 19  will be described below. 
         [0151]    When the release button  11  is depressed into the S 2  state in the condition ST 12  shown in  FIG. 18 , energization of the electromagnet  95  (see  FIG. 19 ) is started. Specifically, energization of the electromagnet  95  is started in response to input of a shooting command. The electromagnet  95  is provided at such a position as to face the iron piece member  81   d  of the driving member  81 . By the energization of the electromagnet  95 , the iron piece member  81   d  is attracted onto the electromagnet  95 , and clockwise rotating motion of the driving member  81  is restrained. In addition, even though the urging force of the spring  89  tends to turn the driving member  82  counterclockwise, the abutment of the contact surface  82   f  of the driving member  82  on the projected part  81   b  of the driving member  81  ensures that turning motion of the driving member  82  is kept restrained. Accordingly, turning motion of the driving member  81  and turning motion of the driving member  82  are both kept restrained. 
         [0152]    Thereafter, the charging member  83  is driven by the link member  84  and the like, to be turned counterclockwise about the axis AX 3 . In response to this turning motion, the arm part  83   b  of the charging member  83  is released from contact with the contact surface  81   e  of the driving member  81 , and the support of the driving member  81  by the charging member  83  is released. In other words, the locking of the driving member  81  by the charging member  83  is released. Then, the charging member  83  is moved to an avoiding position (referred to also as retracted position or reference position) for avoiding contact with the driving member  81  (see  FIG. 19 ). Incidentally, this condition is a condition where the locking of the driving member  81  by the charging member  83  is released; therefore, this condition is referred to also as “unlocked condition.” 
         [0153]    In this manner, transition to the condition STb shown in  FIG. 19  is finished. The condition shown in  FIG. 19  is the condition immediately before start of exposure. 
         [0154]    Thereafter, the electronic leading curtain is made to run, and then energization of the electromagnet  95  is stopped at a predetermined timing. In response to the stop of energization, the driving member  81 , on which the attracting force of the electromagnet  95  is not acting now, is rotated clockwise about the axis AX 1  by the urging force of the spring  88 . In addition, the urging force of the spring  88  is transmitted from the projected part  81   b  of the driving member  81  to the contact surface  82   f  of the driving member  82 , whereby the driving member  82  is also rotated clockwise about the axis AX 1 . In this case, since the spring  88  has been overcharged, the driving member  81  and the driving member  82  can be moved at a very high speed. Besides, attendant on the moving of the driving member  82 , the link pin  82   a  is moved along the slot  71   h.  The link pin  82   a  is stopped upon reaching a lower end part of the slot  71   h  (see  FIG. 15 ). Attendant on the movement of the link pin  82   a,  the arm  75   b  is turned clockwise about the axis AX 4 , and the trailing blades  73   a,    73   b,    73   c  are each moved to an exposure end position (in other words, a closing position for the aperture OP). As a result, return to the condition STa shown in  FIG. 15  is effected, and an aperture-closing operation of the “trailing curtain” is realized. 
         [0155]    In this manner, after the electronic leading curtain is made to run, energization of the electromagnet  95  is stopped at a predetermined timing, whereby the trailing curtain (specifically, a curtain called “mechanical trailing curtain”) is made to run. In this manner, a shutter operation by means of the so-called “electronic leading curtain” and “mechanical trailing curtain” is carried out, whereby an exposure operation for exposing each pixel to light for a predetermined period TM can be performed. 
         [0156]    In the manner as above-described, the operation for transition from the condition STb immediately before start of exposure shown in  FIG. 19  to the condition STa immediately after end of exposure shown in  FIG. 15  is realized. 
         [0157]    &lt;6. Shutter Operation at the Time of Shooting Based on Live View&gt; 
         [0158]      FIG. 20  is a time chart relating a shooting (photographing) operation in the live view mode. In the following, the shooting operation in the live view mode will be described more in detail, referring to  FIG. 20 . 
         [0159]    First, it is assumed that exposure is completed at time T 10 , and transition to the condition STa shown in  FIG. 15  (from the condition STb shown in  FIG. 19 ) is effected. 
         [0160]    Then, as above-mentioned, at time T 11  immediately after time T 10 , an operation for transition from the condition STa ( FIG. 15 ) immediately after end of exposure to the first set condition ST 11  ( FIG. 16 ) is started. In addition, at time T 11 , a process of reading pixels from the image sensor  5  is started. Concurrently with the pixel reading process, the overcharging operation for the spring  88  is carried out. In this case, the aperture-closing state of the trailing curtain is maintained. Therefore, the process of reading a plurality of pixels in the image sensor  5  can be appropriately carried out, while keeping the trailing curtain in the aperture-closing state and thereby avoiding multiple exposure. 
         [0161]    Thereafter, at time T 12 , the overcharging of the spring  88  is completed, and the process of reading pixels from the image sensor  5  is completed. Then, the pixel signal read from the image sensor  5  is subjected to processings by the digital signal processing circuit  53  (see  FIG. 3 ) and the like, whereby image data concerning a real shot image is produced. Incidentally, at time T 12 , the operation for transfer to the first set condition ST 11  ( FIG. 16 ) has been completed. 
         [0162]    Besides, at time T 12 , an operation for transition to the second set condition ST 12  ( FIG. 18 ) is now started. Specifically, in response to a further clockwise rotating motion of the charging member  83 , engagement between the engaging part  83   c  and the circular arc-shaped projected part  82   b  is released (time T 13  ( FIG. 17 )). Then, the driving member  82  is rotated, and, according to the rotating motion of the driving member  82 , the link pin  82   a  is moved along the slot  71   h.  As a result, the trailing blades  73   a,    73   b,    73   c  are each moved to the exposure start position (time T 14 ). At time T 14 , transfer to the second set condition ST 12  ( FIG. 18 ) has been completed. 
         [0163]    After time T 14  when the “trailing curtain” has been retracted from the aperture OP, a live view displaying operation by use of images obtained by the image sensor  5  can be performed. Specifically, in the image pickup apparatus  1 , time-series images relating to a subject image reaching the image sensor  5  through the aperture OP of the shutter device  7  can be displayed on the back monitor  12  at a very short time interval. The user can perform a framing operation by use of the live-view images displayed on the back monitor  12 . 
         [0164]    When the release button  11  is depressed into the S 2  state at time T 20  after the framing operation conducted using the live view in the second set condition ST 12  as above-mentioned, transfer to the condition (the condition shown in  FIG. 19 ) STb immediately before start of exposure is effected at time T 21 . Specifically, energization of the electromagnet  95  is started, and the charging member  83  is rotated counterclockwise about the axis AX 3 , returning to the reference position. 
         [0165]    Then, the electronic leading curtain is started to run at time T 21 , and, after the lapse of a predetermined period (e.g., 1/100 second), specifically at time T 22 , the mechanical trailing curtain is started to run in the manner of chasing after the electromagnetic leading curtain. As a result, an exposure operation for an exposure period according to the time difference between the start of running of the electronic leading curtain and the start of running of the mechanical trailing curtain is carried out, and the exposure operation is completed at time T 30 . At time T 30 , the shutter device  7  has the same condition STa ( FIG. 15 ) as that at time T 10 . Thereafter, the above-mentioned pixel reading process and the like are carried out, whereby image data relevant to a real shot image is obtained. 
         [0166]    According to the above-described embodiment, during the framing operation by use of the live view (from time T 14  to time T 20 ), the overcharged state of the spring  88  can be maintained, without energizing the electromagnet  95 . Therefore, power saving can be realized. 
         [0167]    In addition, according to the above embodiment, during the period from time T 11  to time T 12 , it is possible to carry out the process of reading pixels from the image sensor  5 , while keeping the trailing curtain in the aperture-closing state and thereby avoiding multiple exposure, and to carry out the overcharging operation for the spring  88 . Specifically, during the period from the exposure end condition STa to completion of transfer to the first set condition ST 11 , the process of reading from the image sensor  5  is carried out concurrently with the overcharging operation for the spring  88  in the condition where the closed state of the aperture OP is maintained. Incidentally, such a reading process is controlled by the general control section  101 . 
         [0168]    Here, a shutter device in which a trailing curtain is moved to an aperture-opening position concurrently with an overcharging operation for a spring as, for example, in the first related art, is assumed as a comparative example.  FIG. 21  is a timing chart showing operations of the shutter device according to the comparative example. 
         [0169]    In the shutter device according to the comparative example, the trailing curtain is moved without fail to the aperture-opening position concurrently with the overcharging operation for the spring, so that the spring overcharging operation cannot be carried out while keeping the trailing curtain in the aperture-closing state. Therefore, in the shutter device according to the comparative example, as shown in  FIG. 21 , various operations are sequentially carried out in the order of first completing the pixel reading operation while keeping the trailing curtain in the aperture-closing state, and thereafter starting the spring overcharging operation. 
         [0170]    Therefore, time T 15  when the overcharging of the spring is completed in the comparative example is delayed as compared with time T 12  when the overcharging is completed in the above-described embodiment. For instance, assuming that the time required for reading pixels from the image sensor  5  has a value t 1  (e.g., 100 milliseconds) and the overcharging time has a value t 2  (e.g., 100 milliseconds), the sum ((t 1 +t 2 ) second, for example, 200 milliseconds) of both the times is taken until completing the overcharging in the shutter device according to the comparative example. 
         [0171]    According to the operations in the above-described embodiment, on the other hand, the period taken until completion of overcharging is not the sum of both the value t 1  and the value t 12  but is one (e.g., t 1 =100 milliseconds) of both the values t 1 , t 2 . 
         [0172]    Thus, according to the operations in the above-described embodiment, the period from the time of end of exposure to completion of the overcharging of the spring  88  (plainly, until the next shooting is enabled) can be shortened. 
         [0173]    Besides, even in the case of opening the shutter curtain thereafter, it suffices to add the time required for opening the shutter (the time for transfer from the condition shown in  FIG. 16  to the condition shown in  FIG. 18 ) t 3  (e.g., 30 milliseconds) (t 3 &lt;t 2 ). Therefore, it is also possible to shorten the period of time until the preparation for the next shooting is completed in the live view mode. 
         [0174]    Particularly, in the live view mode, it is also possible to contrive power saving by maintaining the overcharged state of the spring  88  without energization of the electromagnet  95 , and to shorten the period of time from the time of end of exposure until the overcharging of the spring  88  is again completed. 
         [0175]    In addition, particularly when the above-mentioned operation is repeatedly carried out at the time of taking rapid succession shots, the period of time from the time when exposure relevant to a certain shot image is completed to the time when photographing of the next shot image is enabled can be shortened, thereby enhancing the rapid-succession-shots performance. 
         [0176]    &lt;7. Shutter Operation at the Time of Shooting Based on Optical Finder&gt; 
         [0177]    While the above description has been centered on the shutter operation concerning a shooting operation in a live view mode, this is not limitative of the shutter device  7 . For example, the shutter device  7  as above can also be used for a shooting operation based on the optical finder. 
         [0178]    Specifically, in the OVF mode, the condition upon transition from the condition STa ( FIG. 15 ) immediately after end of exposure to the first set condition ST 11  ( FIG. 16 ) may be held, and a framing operation in the OVF mode may then be carried out. Besides, thereafter, sequential transition to each of the conditions shown respectively in  FIGS. 17 ,  18  and  19  may be carried out at high speed, according to the depression of the release button  11 . 
         [0179]    Or, alternatively, a process may be adopted in which in the condition ST 11  shown in  FIG. 16 , in response to depression of the release button  11 , the electromagnet  95  is energized and the charging member  83  is immediately rotated counterclockwise, whereby direct transition to the condition STb shown in  FIG. 19  is effected, without taking the course through the conditions shown in  FIGS. 17 and 18 . 
         [0180]    Thereafter, the same operations as above may be carried out, whereby transition from the condition STb ( FIG. 19 ) immediately before start of exposure to the condition STa ( FIG. 15 ) immediately after end of exposure is effected, and, further, return to the first set condition ST 11  ( FIG. 16 ) is performed. 
         [0181]    Particularly, in the image pickup apparatus  1  using the above-described shutter device  7 , both a framing operation based on the live view and a framing operation based on the OVF can be realized. In the live-view-based framing operation, the condition where the spring  88  is overcharged and the trailing curtain is present in the aperture-opening position (the second set condition ST 12 ) is used in the shutter device  7 . This condition ST 12  is maintained without energization of the electromagnet  95 . In the OVF-based framing operation, on the other hand, the condition ST 11  where the spring  88  is overcharged and the trailing curtain is present in the aperture-closing position is used in the shutter device  7 . This condition ST 11 , also, is maintained without energization of the electromagnet  95 . Thus, the conditions ST 11  and ST 12  are both realized without energization of the electromagnet  95 . Therefore, power saving can be promised. 
         [0182]    &lt;8. Others&gt; 
         [0183]    While embodiments of the present invention have been described above, the invention is not to be limited to or by the contents of the above description. 
         [0184]    For example, while the case where the driving member  81  and the driving member  82  are turned coaxially about the same axis AX 1  has been shown as an example in the above embodiment, this is not limitative of the present invention. A configuration may be adopted in which the driving member  81  and the driving member  82  are turned about different axes, respectively. 
         [0185]    The present application contains subject matter related to that disclosed in Japanese Priority Patent Application JP 2008-194454 filed in the Japan Patent Office on Jul. 29, 2008, the entire content of which is hereby incorporated by reference. 
         [0186]    It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alternations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalent thereof.