Abstract:
This image capture device includes: an imager which receives an optical image of a subject and outputs image data; a focal plane shuttering apparatus which restricts incidence of the optical image onto the imager and which is able to select either a normally opened driving method or a normally closed driving method; and a driving method switching section which switches a method for driving the focal plane shuttering apparatus into one of the normally opened and normally closed driving methods. The driving method switching section switches the method for driving the focal plane shuttering apparatus into the normally opened driving method after an image capturing operation has been performed.

Description:
[0001]    This is a continuation of International Application No. PCT/JP2012/005340, with an international filing date of Aug. 24, 2012, which claims priority of Japanese Patent Applications No. 2011-182396, filed on Aug. 24, 2011 and No. 2011-225591, filed on Oct. 13, 2011, the contents of which are hereby incorporated by reference. 
     
    
     BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The present application relates to a focal plane shuttering apparatus for use in an image capture device which can capture either still pictures or movies. 
         [0004]    2. Description of the Related Art 
         [0005]    Japanese Laid-Open Patent Publication No. 2004-061865 discloses a focal plane shutter which can change from a normally closed state into a normally opened state, and vice versa. To make a digital single lens reflex camera realize a live view function, according to Japanese Laid-Open Patent Publication No. 2004-061865, the front and rear curtains of the focal plane shutter are charged with a curtain charging actuator, and then the front curtain is kept in a running finished state by getting it mechanically locked in its camera body. 
         [0006]    This focal plane shuttering apparatus separates a front curtain charging setting lever from a driving member which is coupled to the front curtain and keeps the driving member in the running finished state when the setting lever is in the charged state, thereby realizing a normally opened state. 
         [0007]    On the other hand, Japanese Laid-Open Patent Publication No. 2007-316503 discloses a shuttering apparatus which makes only the rear curtain run by using an electronic front curtain shuttering function after an image sensor has reset electric charges. In this shuttering apparatus, a rear curtain charging setting member and a driving member coupled to the rear curtain are separated from each other and a locking member is provided to lock the driving member and keep it in the running finished position, thereby realizing a normally opened state. Also, according to Japanese Laid-Open Patent Publication No. 2007-316503, the locking member is unlocked by driving the setting member, thereby carrying out electronic front curtain shutter shooting. 
       SUMMARY 
       [0008]    The present disclosure provides an image capture device that increases the utility of a focal plane shuttering apparatus which can make a slit exposure using front and rear curtains and which can change its states between normally closed and normally opened states. 
         [0009]    An image capture device according to the present disclosure includes: an imager which receives an optical image of a subject and outputs image data; a focal plane shuttering apparatus which restricts incidence of the optical image onto the imager and which is able to select either a normally opened driving method or a normally closed driving method; and a driving method switching section which switches a method for driving the focal plane shuttering apparatus into one of the normally opened and normally closed driving methods. The driving method switching section switches the method for driving the focal plane shuttering apparatus into the normally opened driving method after an image capturing operation has been performed. 
         [0010]    An exemplary embodiment of the present disclosure provides an image capture device that increases the utility of a focal plane shuttering apparatus which can make a slit exposure using front and rear curtains and which can change its states between normally closed and normally opened states. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a perspective view illustrating a digital camera  1 . 
           [0012]      FIG. 2  is a perspective view illustrating its camera body  100 . 
           [0013]      FIG. 3  is a block diagram of the digital camera  1 . 
           [0014]      FIG. 4  is a general cross-sectional view of the digital camera  1 . 
           [0015]      FIG. 5  is a rear view of the camera body  100 . 
           [0016]      FIG. 6  illustrates how a focal plane shuttering apparatus  190  in a normally opened state looks when its rear curtain finishes running. 
           [0017]      FIG. 7  illustrates in further detail a principal portion of the apparatus shown in  FIG. 6 . 
           [0018]      FIG. 8  illustrates how the focal plane shuttering apparatus  190  in the normally opened state looks when a charging operation is done. 
           [0019]      FIG. 9  illustrates how the focal plane shuttering apparatus  190  in the normally opened state looks in a live view mode. 
           [0020]      FIG. 10  illustrates how the focal plane shuttering apparatus  190  in the normally opened state looks in a slit exposure shooting standby mode. 
           [0021]      FIG. 11  illustrates how the focal plane shuttering apparatus  190  in a normally closed state looks when its rear curtain finishes running. 
           [0022]      FIG. 12  illustrates how the focal plane shuttering apparatus  190  in the normally closed state looks during a charging operation. 
           [0023]      FIG. 13  illustrates how the focal plane shuttering apparatus  190  in the normally closed state looks in a slit exposure shooting standby mode. 
           [0024]      FIG. 14  is a flowchart showing the procedure of a normally opened single shooting session. 
           [0025]      FIG. 15  is a flowchart showing the procedure of a normally closed single shooting session. 
           [0026]      FIG. 16  is a timing diagram showing the timings of operation of a slit exposure shooting in the normally opened state. 
           [0027]      FIG. 17  is a timing diagram showing the timings of operation of a slit exposure shooting in the normally closed state. 
           [0028]      FIG. 18  is a flowchart showing the procedure of a normally closed continuous shooting session in the normally opened state. 
           [0029]      FIG. 19  is a timing diagram showing the timings of operation of the normally closed continuous shooting session in the normally opened state. 
           [0030]    Portion (a) of  FIG. 20  is a partial cross-sectional view of the focal plane shuttering apparatus  190  in the normally opened state, and portion (b) of  FIG. 20  is a partial cross-sectional view of the focal plane shuttering apparatus  190  in the normally closed state. 
       
    
    
     DETAILED DESCRIPTION 
       [0031]    Hereinafter, embodiments will be described in detail with reference to the accompanying drawings as needed. It should be noted that the description thereof will be sometimes omitted unless it is absolutely necessary to go into details. For example, description of a matter that is already well known in the related art will be sometimes omitted, so will be a redundant description of substantially the same configuration. This is done solely for the purpose of avoiding redundancies and making the following description of embodiments as easily understandable for those skilled in the art as possible. 
         [0032]    It should be noted that the present inventor provides the accompanying drawings and the following description to help those skilled in the art understand the present disclosure fully. And it is not intended that the subject matter defined by the appended claims is limited by those drawings or the description. 
         [0033]    First of all, terms will be defined. In this description, the shutter of a shuttering apparatus provided for a camera body is supposed to be in either a “normally closed state” or a “normally opened state”. For example, in a single-lens reflex camera including a mirror and an optical viewfinder (which will be sometimes abbreviated herein as “OVF”), when the user is monitoring the subject through the OVF, the aperture of its shutter is closed. Such a state of the shutter will be referred to herein as the “normally closed state”. In the single-lens reflex camera described above, the state of its shutter immediately after the camera has been turned ON is also the normally closed state. On the other hand, in a mirrorless camera without a mirror, when the user is monitoring the subject through an electronic viewfinder (which will be sometimes abbreviated herein as “EVF”) or on an LCD monitor, the shutter is opened. Such a state of the shutter will be referred to herein as the “normally opened state”. In the mirrorless camera described above, the state of its shutter immediately after the camera has been turned ON is also the normally opened state. 
         [0034]    According to conventional technologies, to change the states from the normally opened state into the normally closed state, for example, a shutter which has been locked by a front curtain locking member needs to be unlocked and closed. This “front curtain locking member” is a member for keeping the front curtain in the running finished state once the normally opened mechanism shutter has been charged. To use the shutter in the normally closed state, the front curtain locking member that has been locked needs to be unlocked by driving the front curtain locking member with a dedicated actuator (such as a plunger), for example. In this description, “to charge” means locking a target member (such as a front curtain or a rear curtain) at a predetermined position by rotating or moving the target member in such a direction as to increase the biasing force applied from a spring, for example. 
         [0035]    The present inventor invented a focal plane shuttering apparatus which can change the states between the normally closed state and the normally opened state just by changing the driving direction of a charging actuator (charging motor) instead of adopting such a configuration. 
         [0036]    Hereinafter, embodiments of a focal plane shuttering apparatus and image capture device according to the present disclosure will be described with reference to the accompanying drawings. It should be noted that the embodiments to be described below are just examples of the present disclosure and the present disclosure is in no way limited to those embodiments. 
         [0037]    (1: Digital Camera) 
         [0038]    A digital camera  1  in which a focal plane shuttering apparatus  190  according to the present disclosure is built will be outlined with reference to the accompanying drawings. It should be noted that the focal plane shuttering apparatus does not have to be built in the digital camera of this embodiment but may also be used in any other camera as well. 
         [0039]    First of all, look at  FIGS. 1 to 5 .  FIG. 1  is a perspective view of a digital camera  1  as a first embodiment.  FIG. 2  is a perspective view illustrating its camera body  100 .  FIG. 3  is a functional block diagram of the digital camera  1 .  FIG. 4  is a cross-sectional view generally illustrating the hardware of the digital camera  1 . And  FIG. 5  is a rear view of the camera body. 
         [0040]    As shown in  FIG. 1 , the digital camera  1  is of an interchangeable lens type, and includes a camera body  100  and a lens unit  200  which is readily attachable and removable to/from the camera body  100 . Also, as shown in  FIGS. 2 to 4 , the digital camera  1  includes a focal plane shuttering apparatus  190 . 
         [0041]    The camera body  100  can shoot a subject continuously. More specifically, the camera body  100  can change its modes of operation from an AF continuous shooting mode with a contrast AF (autofocus) enabled using an internal CMOS (complementary metal oxide semiconductor) image sensor  110  (to be described later) into a continuous shooting mode to be performed at higher speeds than in the AF continuous shooting mode (which will be referred to herein as a “high-speed continuous shooting mode”), and vice versa. 
         [0042]    In the AF continuous shooting mode, the focal plane shuttering apparatus  190  performs a normally opened control. On the other hand, in the high-speed continuous shooting mode, the focal plane shuttering apparatus  190  performs a normally closed control. 
         [0043]    In performing the normally opened control, it takes a longer time for the focal plane shutter to get a shooting-related preparation done than in performing the normally closed control. The reason is that the normally opened control should always go through a so-called “opened state” in which the front and rear curtains are kept in a running state and in a charged state, respectively. For that reason, in this embodiment, the normally opened control is supposed to be performed in the AF continuous shooting mode and the normally closed state is supposed to be performed in the high-speed continuous shooting mode as described above. 
         [0044]    As shown in  FIGS. 3  and/or  4 , the camera body  100  has a CMOS image sensor  110 , a CMOS circuit board  113 , a camera monitor  120 , an operating section  130 , a main circuit board  142  including a camera controller  140 , a body mount  150 , a power supply  160 , a card slot  170 , and a focal plane shuttering apparatus  190 . 
         [0045]    The CMOS image sensor  110  is an exemplary image sensor to transform an optical image of the subject into an electrical image signal. The image sensor does not have to be the CMOS image sensor  110  but may also be any other photoelectric transducer such as a COD image sensor. 
         [0046]    The CMOS image sensor  110  transforms an optical image of the subject (which will be sometimes referred to herein as a “subject image”) that has come through the lens unit  200  into an image signal. The image signal thus generated is converted into a digital signal by the A/D converter  111  (see  FIG. 3 ) of the CMOS circuit board  113  to be described later and output as image data. The camera controller  140  subjects the image data that has been digitized by the A/D converter  111  to various kinds of image processing, examples of which include gamma correction, white balance correction, flaw correction, YC conversion, electronic zooming, and JPEG compression. 
         [0047]    The CMOS image sensor  110  operates in response to a timing signal that has been generated by a timing generator  112 . Under the control of the CMOS circuit board  113 , the CMOS image sensor  110  can obtain still picture data and movie data. The movie data thus obtained may also be used to display a through-the-lens image. It should be noted that the still picture data and the movie data are examples of image data. 
         [0048]    In this description, the “through-the-lens image” is an image that forms part of the movie data and that is not written on the memory card  171 . The through-the-lens image is usually a movie and is displayed on the camera monitor  120  to help the user determine the composition of a movie or a still picture. 
         [0049]    The CMOS image sensor  110  can generate a low-resolution movie signal to be used as a through-the-lens image and a high-resolution movie signal to be written. The high-resolution movie may be a movie with an HD resolution (each frame of which may have a resolution of 1920×1080 pixels, for example). 
         [0050]    The CMOS image sensor  110  has an electronic front curtain function for sequentially resetting pixels in the running direction of a group of front curtains  21  to be described later. 
         [0051]    The CMOS circuit board  113  includes a circuit for controlling the CMOS image sensor  110 . Specifically, the CMOS circuit board  113  includes an A/D converter  111  and the timing generator  112 . 
         [0052]    As described above, the A/D converter  111  of the CMOS circuit board  113  digitizes the image signal supplied from the CMOS image sensor  110 , thereby generating image data. The CMOS circuit board  113  is an exemplary image sensor circuit board which drives and controls the image sensor and which subjects the image data supplied from the image sensor to A/D conversion and other kinds of predetermined processing. 
         [0053]    The camera monitor  120  displays an image represented by image data to be displayed and other images. The camera monitor  120  may be a liquid crystal display, for example. The image data to be displayed is generated by the camera controller  140 , and is data to display, as an image, various kinds of information including image data that has been subjected to image processing, a shooting condition on the digital camera  1 , and an operating menu. The camera monitor  120  can display both movies and still pictures selectively. 
         [0054]    The camera monitor  120  is provided for the camera body  100 . Although the camera monitor  120  is arranged in this embodiment on the back of the camera body  100 , the camera monitor  120  may be arranged anywhere else on the camera body  100 . For example, the camera monitor  120  may also be arranged on a side surface or on the upper surface of the camera body  100 . 
         [0055]    It should be noted that the camera monitor  120  is an exemplary display section provided for the camera body  100 . Any other device may be used as the display section as long as the device can display an image. For example, not just a liquid crystal display but also an organic EL panel, an inorganic EL panel and a plasma display panel may be used as well. 
         [0056]    The operating section  130  is an interface which accepts user&#39;s instructions. Specifically, the operating section  130  includes a release button  131  and a power switch  132  as shown in  FIG. 5 . The release button  131  accepts a focal plane shuttering instruction by the user. The power switch  132  is a rotary dial switch arranged on the upper surface of the camera body  100 , and is used to turn ON or OFF the camera body  100 . Anything may be used as the operating section  130  as long as it can accept the user&#39;s instructions. Examples of the operating section  130  include a button, a lever, a dial and a touchscreen panel. 
         [0057]    Now look at  FIG. 3  again. 
         [0058]    The camera controller  140  controls the overall operation of this digital camera  1 , i.e., the operations of the respective components of the digital camera  1 . For example, the camera controller  140  accepts an instruction that has been entered through the operating section  130 . Also, the camera controller  140  transmits a signal to control the lens unit  200  to the lens controller  240  via the body mount  150  and a lens mount  250 , thereby controlling the respective sections of the lens unit  200  indirectly. 
         [0059]    Furthermore, the camera controller  140  also controls the CMOS circuit board  113 . Specifically, the camera controller  140  sends a control signal to the CMOS circuit board  113 , which in turn controls the CMOS image sensor  110  in accordance with the control signal received. That is to say, it can be said that the camera controller  140  controls the operation of the CMOS image sensor  110  by controlling the CMOS circuit board  113 . Also, the camera controller  140  obtains image data that has been subjected to A/D conversion and other predetermined kinds of processing by the CMOS circuit board  113  and subjects the image data to further processing. For example, based on the image data that has been processed by the CMOS circuit board  113 , the camera controller  140  generates the image data to be displayed and movie data to be written. 
         [0060]    The memory card  171  is readily attachable to, and removable from, the card slot  170 . The card slot  170  controls the memory card  171  in accordance with a control signal supplied from the camera controller  140 . Specifically, the card slot  170  stores image data on the memory card  171  and retrieves the image data from the memory card  171 . 
         [0061]    The memory card  171  can store the image data that has been generated by the camera controller  140  through image processing. For example, the memory card  171  can store non-compressed RAW image files and compressed JPEG image files. Furthermore, the memory card  171  can further output an image file that has been stored inside itself in advance through the card slot  170 . The camera controller  140  subjects images which are included in the image file that has been provided by the memory card  171  to predetermined processing. For instance, the camera controller  140  subjects the image file that has been gotten from the memory card  171  to expansion processing, thereby generating image data to be displayed. 
         [0062]    The memory card  171  can further store movie data that has been generated by the camera controller  140  through image processing. For example, the memory card  171  can store a movie file which has been compressed in compliance with the H.264/AVC, which is a moving picture compression standard. Also, the memory card  171  can output a movie file which has been stored inside itself in advance through the card slot  170 . The camera controller  140  subjects the image included in a movie file that has been supplied from the memory card  171  to a predetermined kind of processing. For example, the camera controller  140  subjects the movie file that has been retrieved from the memory card  171  to expansion processing, thereby generating movie data to be displayed. 
         [0063]    It should be noted that the memory card  171  forms part of a storage section, which may be attachable to, and removable from, the camera body  100  such as the memory card  171  or may be fixed to (or built in) the digital camera  1 . 
         [0064]    The power supply  160  supplies power to be used by the digital camera  1  to respective parts. The power supply  160  may dry battery or a rechargeable battery. Alternatively, the power supply  160  may also be a unit which is supplied with power from an external power supply through a power code and which relays the power to the digital camera  1 . 
         [0065]    When the lens unit  200  is attached to the camera body  100 , the body mount  150  gets engaged with the lens mount  250  and supports the lens unit  200 . Also, the body mount  150  and the lens mount  250  are electrically connected together. The camera body  100  can transmit and receive data and/or control signals to/from the lens unit  200  via the body mount  150  and the lens mount  250 . 
         [0066]    The focal plane shuttering apparatus  190  is arranged in front of the CMOS image sensor  110  (i.e., closer to the lens unit  200  than the CMOS image sensor  110  is). The focal plane shuttering apparatus  190  can change its states from a state in which light traveling from the optical system L to the CMOS image sensor  110  is cut into a state in which the light traveling from the optical system L to the CMOS image sensor  110  is passed, and vice versa. By adjusting the period of time for which the shutter is opened, the focal plane shuttering apparatus  190  controls the exposure time of the CMOS image sensor  110 . 
         [0067]    The lens unit  200  is attachable to, and removable from, the camera body  100  and produces an optical image of the subject. More specifically, the lens unit  200  includes the optical system L, a driver  215 , the lens mount  250 , the lens controller  240  and a lens barrel  290 . 
         [0068]    The optical system L produces an optical image of the subject on the photosensitive plane of the CMOS image sensor  110 . 
         [0069]    The lens controller  240  controls the entire lens unit  200  in accordance with a control signal supplied from the camera controller  140 . 
         [0070]    (2: Configuration for Focal Plane Shuttering Apparatus  190 ) 
         [0071]    Hereinafter, a focal plane shuttering apparatus  190  according to this first embodiment of the present disclosure will be described with reference to  FIGS. 6 through 11 . 
         [0072]    —Aperture Opening and Closing Mechanism— 
         [0073]      FIG. 6  illustrates a shooting finished state of the focal plane shuttering apparatus (i.e., a state in which the rear curtain has finished running).  FIG. 7  illustrates a principal part of  FIG. 6  on a larger scale. 
         [0074]    The shutter base plate  11  has a structure in which two plates are laid one upon the other. Those two plates are arranged so that a gap that is wide enough to allow a group of front curtains  21  and a group of rear curtains  31  to run through the gap is left between them. The shutter base plate has a window (which will be referred to herein as an “aperture”)  11   a  to lead the light that has come from the subject via the shooting lens L to the CMOS image sensor  110 . 
         [0075]    In this embodiment, the group of front curtains  21  consists of three blades. Those three blades which form the group of front curtains  21  are illustrated in  FIG. 10  as first, second and third front curtains  21   a ,  21   b  and  21   c . In  FIG. 6 , those three blades that form the group of front curtains  21  are indicated by the dotted rectangles. 
         [0076]    The group of front curtains  21  is driven as a front curtain driving arm  22  and a front curtain following arm  23  rotate. The front curtain driving arm  22  has shafts  22   b ,  22   c  and  22   d . The first, second and third front curtains  21   a ,  21   b  and  21   c  are loaded rotatably on the shafts  22   d ,  22   c  and  22   b , respectively. On the other hand, the front curtain following arm  23  has shafts  23   b ,  23   c  and  23   d . The first, second and third front curtains  21   a ,  21   b  and  21   c  are loaded rotatably on the shafts  23   d ,  23   c  and  23   b , respectively. 
         [0077]    The front curtain driving arm  22  is supported rotatably on a front curtain driving arm shaft  22   a  with respect to the shutter base plate  11 . Meanwhile, the front curtain following arm  23  is supported rotatably on a front curtain following arm shaft  23   a  with respect to the shutter base plate  11 . In this manner, the group of front curtains  21  forms a so-called “parallel link mechanism”. As the front curtain driving and following arms  22  and  23  rotate, the first, second and third front curtains  21   a ,  21   b  and  21   c  sequentially move along the shorter sides of the aperture  11   a  while being kept parallel to the longer sides of the aperture  11   a . And the group of front curtains  21  may be sometimes retracted from the aperture  11   a  as shown in  FIG. 6  (such a state will be referred to herein as a “front curtain running finished state”) and may sometimes cover the aperture  11   a  as shown in  FIG. 10  (such a state will be referred to herein as a “front curtain shooting standby state”). The group of front curtains  21  can make a transition from one of these two states into the other by getting the first, second and third blades  21   a ,  21   b  and  21   c  driven. 
         [0078]    The group of rear curtains  31  also consists of three blades. Those three blades which form the group of rear curtains  31  are illustrated in  FIG. 6  as first, second and third rear curtains  31   a ,  31   b  and  31   c.    
         [0079]    The group of rear curtains  31  is driven as a rear curtain driving arm  32  and a rear curtain following arm  33  rotate. The rear curtain driving arm  32  has shafts  32   b ,  32   c  and  32   d . The first, second and third rear curtains  31   a ,  31   b  and  31   c  are loaded rotatably on the shafts  32   b ,  32   c  and  32   d , respectively. On the other hand, the rear curtain following arm  33  has shafts  33   b ,  33   c  and  33   d . The first, second and third rear curtains  31   a ,  31   b  and  31   c  are loaded rotatably on the shafts  33   b ,  33   c  and  33   d , respectively. 
         [0080]    The rear curtain driving arm  32  is supported rotatably on a rear curtain driving arm shaft  32   a  with respect to the shutter base plate  11 . Meanwhile, the rear curtain following arm  33  is supported rotatably on a rear curtain following arm shaft  33   a  with respect to the shutter base plate  11 . In this manner, the group of rear curtains  31  forms a so-called “parallel link mechanism”. As the rear curtain driving and following arms  32  and  33  rotate, the first, second and third rear curtains  31   a ,  31   b  and  31   c  sequentially move along the shorter sides of the aperture  11   a  while being kept parallel to the longer sides of the aperture  11   a . And the group of rear curtains  31  may sometimes cover the aperture  11   a  as shown in  FIG. 6  (such a state will be referred to herein as a “rear curtain running finished state”) and may sometimes be retracted from the aperture  11   a  as shown in  FIG. 10  (such a state will be referred to herein as a “rear curtain shooting standby state”). The group of rear curtains  31  can make a transition from one of these two states into the other by getting the first, second and third blades  31   a ,  31   b  and  31   c  driven. 
         [0081]    —Front Curtain Driving Mechanism— 
         [0082]    Next, a front curtain driving mechanism for driving the group of front curtains  21  will be described with reference to  FIGS. 6 and 7 . 
         [0083]    The front curtain driving arm  22  (see  FIG. 6 ) has a front curtain driving arm coupling hole  22   e , to which a front curtain driving lever coupling pin  28   a  (see  FIG. 7 ) has been inserted. The front curtain driving lever coupling pin  28   a  is provided for a front curtain driving lever  28  (see  FIG. 7 ). Just like the front curtain driving arm  22 , the front curtain driving lever  28  is also supported rotatably on the shaft  22   a  (see  FIG. 7 ). The front curtain driving arm and driving lever and  28  both rotate on the shaft  22   a  while being linked together. 
         [0084]    A front curtain setting spring  27  applies biasing force to the front curtain driving arm  22 . The biasing force applied from the front curtain setting spring  27  is also transferred to the front curtain following arm  23  (see  FIG. 6 ) and the front curtain driving lever  28 . And the front curtain setting spring  27  applies the clockwise biasing force to the front curtain driving lever  28 . Since the front curtain driving lever coupling pin  28   a  of the front curtain driving lever  28  has been inserted into the front curtain driving arm coupling hole  22   e  of the front curtain driving arm  22  (see  FIG. 6 ), the clockwise biasing force is applied to the front curtain driving arm  22  (see  FIG. 6 ), too. That is to say, the biasing force from the front curtain setting spring  27  is applied in the direction in which the group of front curtains  21  covers the aperture  11   a.    
         [0085]    The front curtain driving lever  28  has a front curtain driving lever locking portion  28   c . As shown in  FIG. 10 , the front curtain driving lever locking portion  28   c  contacts with a locking claw  37   b  provided for a front curtain locking lever  37 . The front curtain locking lever  37  is supported rotatably on a shaft  37   a . The shaft  37   a  is fixed on the shutter base plate  11 . Furthermore, biasing force is applied counterclockwise from a front curtain locking lever spring  54  to the front curtain locking lever  37 . 
         [0086]    The front curtain driving lever  28  has a front curtain driving lever contacting portion  28   b , which contacts with a front curtain setting lever contacting portion  24   a  that is provided for a front curtain setting lever  24 . Just like the front curtain driving lever  28 , the front curtain setting lever  24  is supported rotatably on the shaft  22   a . As the front curtain setting lever  24  rotates counterclockwise, the front curtain setting lever contacting portion  24   a  pushes the front curtain driving lever contacting portion  28   b  to turn the front curtain driving lever  28  counterclockwise. As biasing force is applied counterclockwise from the front curtain setting spring  27  to the front curtain driving lever  28 , the front curtain setting lever contacting portion  24   a  contacts with the front curtain driving lever contacting portion  28   b.    
         [0087]    It is a front curtain running spring  25  (see  FIG. 6 ) that applies the counterclockwise biasing force to the front curtain setting lever  24 . That is to say, the front curtain running spring  25  applies strong counterclockwise biasing force to the front curtain setting lever  24 . The biasing force applied from the front curtain running spring  25  is transferred to the front curtain driving lever  28  via the contact between the front curtain setting lever contacting portion  24   a  and the front curtain driving lever contacting portion  28   b . In this manner, the front curtain running spring  25  applies such strong counterclockwise biasing force to the front curtain driving lever  28 . And the biasing force applied from the front curtain running spring  25  is also transferred to the front curtain driving arm  22  and the group of front curtains  21 . That is to say, the biasing force is applied from the front curtain running spring  25  in the direction in which the group of front curtains  21  retracts from the aperture  11   a . In this case, the counterclockwise biasing force applied from the front curtain running spring  25  to the front curtain driving lever  28  is stronger than the clockwise biasing force applied from the front curtain setting spring  27  to the front curtain driving lever  28 . Consequently, since the biasing force applied from the front curtain running spring  25  is stronger than the biasing force applied from the front curtain setting spring  27 , the resultant force of the respective biasing forces applied from the front curtain running spring  25  and the front curtain setting spring  27  can make the group of front curtains  21  run in such a direction as to get the group of front curtains  21  retracted from the aperture  11   a.    
         [0088]    In addition, a front curtain guiding piece  24   b  is provided for the front curtain setting lever  24 . The front curtain guiding piece  24   b  may be attracted to a front curtain electromagnet  26 , which can attract the front curtain guiding piece  24   b  by generating magnetic attractive force that is strong enough to overcome the biasing force applied from the front curtain running spring  25 . As a result, the running direction of the group of front curtains  21 , i.e., the opening and closing operations by the group of front curtains  21 , can be controlled. 
         [0089]    —Rear Curtain Driving Mechanism— 
         [0090]    Next, a rear curtain driving mechanism for driving the group of rear curtains  31  will be described with reference to  FIGS. 6 and 7 . 
         [0091]    The rear curtain driving arm  32  (see  FIG. 6 ) has a rear curtain driving arm coupling hole  32   e  (see  FIG. 6 ), to which a rear curtain driving lever coupling pin  39   a  (see  FIG. 7 ) has been inserted. The rear curtain driving lever coupling pin  39   a  is provided for a rear curtain driving lever  39  (see  FIG. 7 ). Just like the rear curtain driving arm  32 , the rear curtain driving lever  39  is also supported rotatably on the shaft  32   a  (see  FIG. 7 ). The rear curtain driving arm and driving lever  32  and  39  both rotate on the shaft  32   a  while being linked together. 
         [0092]    A rear curtain setting spring  55  applies biasing force to the rear curtain driving arm  32 . The biasing force applied from the rear curtain setting spring  55  is also transferred to the rear curtain following arm  33  (see  FIG. 6 ) and the rear curtain driving lever  39 . And the rear curtain setting spring  55  applies a clockwise biasing force to the rear curtain driving lever  39 . Since the rear curtain driving lever coupling pin  39   a  of the rear curtain driving lever  39  has been inserted into the rear curtain driving arm coupling hole  32   e  of the rear curtain driving arm  32  (see  FIG. 6 ), a clockwise biasing force is applied to the rear curtain driving arm  32  (see  FIG. 6 ), too. That is to say, the biasing force from the rear curtain setting spring  55  is applied in the direction in which the group of rear curtains  31  covers the aperture  11   a.    
         [0093]    The rear curtain driving lever  39  has a rear curtain driving lever locking portion  39   c . The rear curtain driving lever locking portion  39   c  can get engaged with a locking portion  52   b  of the rear curtain locking lever  52  with the group of rear curtains  31  covering the aperture  11   a . The rear curtain locking lever  52  is supported rotatably on a shaft  52   a . The shaft  52   a  is fixed on the shutter base plate  11 . Furthermore, a counterclockwise biasing force is applied from a rear curtain locking lever spring  53  to the rear curtain locking lever  52 . 
         [0094]    The rear curtain driving lever  39  has a rear curtain driving lever contacting portion  39   b , which contacts with a rear curtain setting lever contacting portion  34   a  that is provided for a rear curtain setting lever  34 . Just like the rear curtain driving lever  39 , the rear curtain setting lever  34  is supported rotatably on the shaft  32   a . As the rear curtain setting lever  34  rotates counterclockwise, the rear curtain setting lever contacting portion  34   a  pushes the rear curtain driving lever contacting portion  39   b  to turn the rear curtain driving lever  39  counterclockwise. As biasing force is applied counterclockwise from the rear curtain setting spring  55  to the rear curtain driving lever  39 , the rear curtain setting lever contacting portion  34   a  contacts with the rear curtain driving lever contacting portion  39   b.    
         [0095]    It is a rear curtain running spring  35  (see  FIG. 6 ) that applies the counterclockwise biasing force to the rear curtain setting lever  34 . That is to say, the rear curtain running spring  35  applies strong counterclockwise biasing force to the rear curtain setting lever  34 . The biasing force applied from the rear curtain running spring  35  is transferred to the rear curtain driving lever  39  via the contact between the rear curtain setting lever contacting portion  34   a  and the rear curtain driving lever contacting portion  39   b . In this manner, the rear curtain running spring  35  applies such strong counterclockwise biasing force to the rear curtain driving lever  39 . And the biasing force applied from the rear curtain running spring  35  is also transferred to the rear curtain driving arm  32  and the group of rear curtains  31 . That is to say, the biasing force is applied from the rear curtain running spring  35  in the direction in which the group of rear curtains  31  covers the aperture  11   a . In this case, the counterclockwise biasing force applied from the rear curtain running spring  35  to the rear curtain driving lever  39  is stronger than the clockwise biasing force applied from the rear curtain setting spring  55  to the rear curtain driving lever  39 . Consequently, since the biasing force applied from the rear curtain running spring  35  is stronger than the biasing force applied from the rear curtain setting spring  55 , the resultant force of the respective biasing forces applied from the rear curtain running spring and setting spring  35  and can make the group of rear curtains  31  run in such a direction in which the rear curtains  31  cover the aperture  11   a.    
         [0096]    In addition, a rear curtain guiding piece  34   b  is provided for the rear curtain setting lever  34 . The rear curtain guiding piece  34   b  may be attracted to a rear curtain electromagnet  36 , which can attract the rear curtain guiding piece  34   b  by generating magnetic attractive force that is strong enough to overcome the biasing force applied from the rear curtain running spring  35 . As a result, the running direction of the group of rear curtains  31 , i.e., the opening and closing operations by the group of rear curtains  31 , can be controlled. 
         [0097]    —Normally Opened Charging Mechanism— 
         [0098]    Next, a normally opened charging mechanism will be described. 
         [0099]    The focal plane shuttering apparatus  190  includes a front curtain setting lever  24 , a front curtain driving lever  28 , a charging lever  29 , a rear curtain setting lever  34 , a front curtain locking lever  37 , a rear curtain driving lever  39 , a normally opened charging missing tooth gear  40 , a planetary gear  41 , a planetary carrier  42 , a sun gear  43 , a worm gear  44 , a charging motor  46 , a coupled gear  48 , a normally closed charging missing tooth gear  50 , a rear curtain locking lever  52  and a unlocking lever  60 . A front curtain charging input portion  24   c  is arranged at one end of the front curtain setting lever  24 . And a rear curtain charging input portion  34   c  is arranged at one end of the rear curtain setting lever  34 . 
         [0100]    The charging lever  29  includes a front curtain setting cam  29   b  and a rear curtain setting cam  29   c . The front curtain setting cam  29   b  turns the front curtain setting lever  24  clockwise, thereby bringing the front curtain guiding piece  24   b  into contact with the front curtain electromagnet  26 . Likewise, the rear curtain setting cam  29   c  turns the rear curtain setting lever  34  clockwise, thereby bringing the rear curtain guiding piece  34   b  into contact with the rear curtain electromagnet  36 . That is to say, the charging lever  29  performs a charging operation by using the respective biasing forces applied from the front curtain setting and running springs  27  and  25  and the rear curtain setting and running springs  55  and  35 . In this description, a state in which the front curtain electromagnet  26  is ready to attract the front curtain guiding piece  24   b  will be referred to herein as a “front curtain charging finished state”, and a state in which the rear curtain electromagnet  36  is ready to attract the rear curtain guiding piece  34   b  will be referred to herein as a “rear curtain charging finished state”. Also, to turn the front curtain into the charging finished state will be referred to herein as “charging the front curtain”, and to turn the rear curtain into the charging finished state will be referred to herein as “charging the rear curtain”. 
         [0101]    A charging lever missing tooth gear  29   e  is supported along with the charging lever  29 . Specifically, the charging lever  29  and the charging lever missing tooth gear  29   e  are supported rotatably on a charging lever shaft  29   a . A charging lever returning spring  30  applies clockwise biasing force to the charging lever  29 . The charging lever returning spring  30  may be a helical torsion coil spring, for example, and is arranged on the shaft of the charging lever  29 . 
         [0102]    A stopper (not shown) is provided for the shutter base plate  11 . When contacting with the stopper of the charging lever  29 , the stopper prevents the charging lever  29  from rotating under the biasing force applied from the charging lever returning spring  30 . In a situation where no force other than the biasing force applied from the charging lever returning spring  30  is acting on the charging lever  29 , the charging lever  29  is held at a position where the charging lever  29  contacts with the stopper (not shown) of the shutter base plate  11 . 
         [0103]    The charging lever missing tooth gear portion  29   e  is engageable with a missing tooth gear  40 , which is supported rotatably on the shutter base plate  11 . The missing tooth gear  40  is comprised of stacked gears and has a gear portion, which has teeth over the entire periphery thereof and which is engageable with the planetary gear  41 . 
         [0104]    The planetary gear  41  is supported rotatably on the planetary carrier  42 , which has the same shaft as the sun gear  43  and which is supported rotatably on the shutter base plate  11 . The sun gear  43  and the planetary gear  41  are engaged with each other. In this case, if a moderate rotational load is imposed on any of the planetary carrier  42 , the planetary gear  41  and the sun gear  43 , the planetary carrier  42  and the planetary gear  41  rotate according to the rotation direction of the sun gear  43 . 
         [0105]    The planetary carrier  42  includes first and second rotation preventing portions  42   a  and  42   b , which contact with first and second stoppers (not shown), respectively, on the shutter base plate  11 . As a result, the planetary carrier  42  is prevented from rotating. 
         [0106]    The sun gear  43  is comprised of stacked gears and has a worm wheel that engages with the worm gear  44 , which is arranged on the shaft of the motor  46 . 
         [0107]    A front curtain unlocking sensing switch  47  is fixed on the shutter base plate  11  and detects the position of the front curtain locking lever  37  rotating. 
         [0108]    A rear curtain unlocking sensing switch  57  is fixed on the shutter base plate  11  and detects the position of the rear curtain locking lever  52  rotating. 
         [0109]    —Running Finished State— 
         [0110]    As shown in  FIG. 6 , the group of front curtains  21  has gotten retracted to over the aperture  11   a  under the biasing force applied from the front curtain running spring  25 . On the other hand, as shown in  FIG. 7 , the front curtain setting and driving levers  24  and  28  have their contacting portions  24   a  and  28   b  kept in contact with each other under the biasing forces applied from the front curtain setting spring and running spring  27  and  25 , and both keep having rotated counterclockwise. Meanwhile, the group of rear curtains  31  covers the aperture  11   a  under the biasing force applied from the rear curtain running spring  35 . On the other hand, the rear curtain setting and driving levers  34  and  39  have their contacting portions  34   a  and  39   b  kept in contact with each other under the biasing force applied from the rear curtain running spring  35 , and both keep having rotated counterclockwise. 
         [0111]    —Charging Operation— 
         [0112]      FIG. 8  illustrates a state where the charging operation has gotten done on the front and rear curtains.  FIG. 14  is a flowchart showing the procedure of a slit exposure shooting session in the normally opened state. And  FIG. 16  is a timing diagram showing the timings of operation of the slit exposure shooting session in the normally opened state. 
         [0113]    Hereinafter, the charging operation will be described mainly with reference to  FIG. 14 . In  FIG. 14  and  FIGS. 15 ,  18  and so on to be referred to later, the reference sign CW stands for clockwise, the reference sign CCW stands for counterclockwise, and Mg_ON and Mg_OFF respectively mean starting and stopping supplying power to an electromagnet. 
         [0114]    In the running finished state shown in  FIGS. 6 and 7 , power is supplied to the motor  46  (in STEP  1  and at the time t 1  shown in  FIG. 16 ), which rotates the worm gear  44  in the normal direction. Then the sun gear  43  with a worm wheel that engages with the worm gear  44  is turned clockwise. As a result, the planetary carrier  42  also rotates clockwise under the rotational load and the second rotation preventing portion  42   b  contacts with the second stopper (not shown) on the shutter base plate  11 . In the meantime, the planetary gear  41  shown in  FIG. 7  moves (i.e., revolves) along with its planetary carrier rotating. When the planetary gear  41  stops revolving due to contact of the second rotation preventing portion  42   b  with the second stopper, the planetary gear  41  is still engaged with the missing tooth gear  50 . Thereafter, the planetary gear  41  itself rotates counterclockwise, thereby turning the missing tooth gear  40  clockwise. At this time, the missing tooth gear  50  tries to rotate clockwise due to slight friction between the missing tooth gear  40  and itself. However, the second rotation preventing portion  42   b  contacts with the missing teeth of the missing tooth gear  50 , thus preventing the missing tooth gear  50  from rotating. On the other hand, the missing tooth portion of the missing tooth gear  40  gets engaged with the missing tooth gear portion  29   e  of the charging lever  29 , thereby turning the missing tooth gear portion  29   e  on the charging lever shaft  29   a . The charging lever  29  which forms part of the missing tooth gear portion  29   e  rotates counterclockwise against the biasing force applied from the charging lever returning spring  30 . 
         [0115]    As the charging lever  29  rotates, the rear curtain setting cam  29   c  presses the rear curtain charging input portion  34   c . As a result, the rear curtain setting lever  34  rotates clockwise. When the rear curtain charging input portion  34   c  reaches the outermost portion of the rear curtain setting cam  29   c , the rear curtain guiding piece  34   b  gets pressed against the rear curtain electromagnet  36 . In the same way, the front curtain setting cam  29   b  presses the front curtain charging input portion  24   c , and the front curtain setting lever  24  rotates clockwise. The front curtain charging input portion  24   c  is driven in the outer peripheral direction of the front curtain setting cam  29   b , and the front curtain guiding piece  24   b  gets pressed against the front curtain electromagnet  26 . 
         [0116]    When the rear curtain setting lever  34  rotates clockwise, the rear curtain driving lever  39  also tries to rotate clockwise under the biasing force applied from the rear curtain setting spring  55 . However, since the locking portion  52   b  of the rear curtain locking lever  52  is locked to the rear curtain driving lever locking portion  39   c , the locking portion  52   b  prevents the rear curtain driving lever  39  from rotating. That is why only the rear curtain setting lever  34  rotates clockwise. As the rear curtain driving lever  39  does not rotate, the group of rear curtains  31  keeps the aperture  11   b  covered throughout the charging operation. As a result, while image data is being read from the CMOS image sensor  110 , the charging operation can be carried out on the rear curtain in parallel. In this embodiment, until the charging operation gets done on the rear curtain, the group of rear curtains  31  keeps the aperture  11   a  covered. 
         [0117]    Now take a look at  FIG. 14  again. When reading from the CMOS image sensor  110  is finished (i.e., if the answer to the query of STEP  2  is YES), the motor  46  shown in  FIG. 7  further rotates and the charging lever  29  further rotates counterclockwise. Then, the focal plane shuttering apparatus  190  enters the state shown in  FIG. 9 , which illustrates a situation where the charging operation has been performed on the front and rear curtains by getting the groups of front and rear curtains  21  and  31  retracted from the aperture  11   a . In other words,  FIG. 9  illustrates a state where a live view function is turned ON. The live view function may be used at the time t 2  shown in  FIG. 16 , for example. 
         [0118]    When an unlocking projection  29   g  of the charging lever  29  kicks an unlocking claw  52   c  of the rear curtain locking lever  52 , the rear curtain locking lever  52  rotates clockwise against the biasing force applied from the rear curtain locking lever spring  53 , thus unlocking the locking portion  52   b  from the rear curtain driving lever locking portion  39   c . Then, the rear curtain driving lever  39  rotates clockwise under the biasing force applied from the rear curtain setting spring  55  until the rear curtain setting lever contacting portion  34   a  contacts with the rear curtain driving lever contacting portion  39   b , and the group of rear curtains  31  gets retracted from the aperture  11   a . In the meantime, the rear curtain unlocking sensing switch  57  is turned by a rear curtain locking lever switch turning portion  52   d  (in STEP  3 ). Then, a state where the rear curtain setting cam  29   c  is in contact with the rear curtain charging input portion  34   c  and the group of rear curtains  31  has retracted from the aperture  11   a  is maintained. 
         [0119]    On the other hand, when the unlocking projection  29   g  of the charging lever  29  kicks the unlocking claw  52   c  of the rear curtain locking lever  52 , the rear curtain locking lever  52  rotates clockwise against the biasing force applied from the rear curtain locking lever spring  53 . In this state, the locking portion  37   b  of the front curtain locking lever  37  is engaged with the front curtain driving lever locking portion  28   c  as shown in  FIG. 7 , and therefore, the state where the locking portion  37   b  prevents the front curtain driving lever  28  from rotating is maintained. As a result, the front curtain driving lever  28  does not rotate, and the group of front curtains  21  is kept retracted from the aperture  11   a  throughout the charging operation. 
         [0120]    In the state shown in  FIG. 9 , the light that has come from the subject is guided to the CMOS image sensor  110 . Such a state is particularly effective when the CMOS image sensor  110  should be kept exposed to light for a while. For example, this state is effective particularly when the camera body  100  is used to observe or frame the subject with the live view function turned ON, shoot a movie, or perform a continuous shooting session with the AF function turned ON (in STEP  4 ). 
         [0121]    As can be seen from the state shown in  FIG. 9 , the focal plane shuttering apparatus  190  can maintain mechanically a sate where the aperture  11   a  is opened. That is to say, the focal plane shuttering apparatus  190  has the so-called “normally opened” function. 
         [0122]    It should be noted that the position of the charging lever  29  rotating is detected by the camera controller  140  (see  FIG. 3 ) based on the number of revolutions of the motor  46 . More specifically, the absolute position of the charging lever  29  rotating is detected by the camera controller  140  using the rear curtain unlocking sensing switch  57 . 
         [0123]    —Slit Exposure Standby State— 
         [0124]    When the user presses the release button  131  (in STEP  5  shown in  FIG. 14 ), the CMOS image sensor  110  gets necessary shooting information about photometry, for example. When every piece of necessary shooting information is gotten, the camera controller  140  permits the release. At this point in time, the focal plane shuttering apparatus  190  is in the state shown in  FIG. 9 . When the release is permitted, the focal plane shuttering apparatus  190  enters the state shown in  FIG. 10 , which illustrates the slit exposure standby state of the focal plane shuttering apparatus  190 . 
         [0125]    Specifically, the charging lever  29  has a fan-shaped charging lever projection  29   d  (see  FIG. 9 ) and the unlocking lever  60  also has a fan-shaped unlocking lever projection  60   c . The charging lever projection  29   d  and unlocking lever projection  60   c  are arranged on substantially the same radius. The unlocking lever  60  is supported rotatably on the charging lever shaft  29   a . The unlocking lever  60  is biased clockwise by the charging lever returning spring  30 . 
         [0126]    A stopper (not shown) provided for the shutter base plate  11  contacts with a stopper (not shown) provided for the unlocking lever  60 , thereby keeping the unlocking lever  60  from being turned by the charging lever returning spring  30 . If no force other than the biasing force applied from the charging lever returning spring  30  is acting on the unlocking lever  60 , the unlocking lever  60  is kept in contact with the stopper (not shown) on the shutter base plate  11  as shown in  FIG. 6 . At this point in time, the missing tooth gear portions  29   e  and  60   d  of the charging and unlocking levers  29  and  60  are held in the same phase. 
         [0127]    In this embodiment, the charging lever projection  29   d  and unlocking lever projection  60   c  are arranged so as to leave a gap between them in the rotating direction. Specifically, even if the charging lever  29  is rotated counterclockwise from its position shown in  FIG. 6  to its position shown in  FIG. 9 , the charging lever projection  29   d  does not contact with the unlocking lever projection  60   c  and only the charging lever  29  rotates. On the other hand, if the unlocking lever  60  is rotated counterclockwise, then the charging lever  29  will rotate, too, along with the unlocking lever  60 . That is to say, the charging lever  29  with the charging lever projection  29   d  and the unlocking lever  60  with the unlocking lever projection  60   c  are configured to rotate on the same shaft (i.e., on the charging lever shaft  29   a ), and either only the charging lever  29  or both of the charging and unlocking levers  29  and  60  are selectively rotated according to the rotating direction of the motor  46 . 
         [0128]    Specifically, if the unlocking lever  60  is turned counterclockwise by the missing tooth gear  50 , the charging lever  29  also rotates counterclockwise along with the unlocking lever  60 , because the unlocking lever projection  60   c  is in contact with the charging lever projection  29   d . As a result, the charging lever returning spring  30  is rotated in a direction in which biasing force is applied to the spring  30 . Consequently, the charging lever returning spring  30  is charged. 
         [0129]    In this description, the charging lever projection  29   d  and unlocking lever projection  60   c  will be sometimes collectively referred to herein as a “driving portion”. The driving portion charges the groups of front and rear curtains and  31  by using the driving force of the motor. Specifically, the driving portion charges the groups of front and rear curtains  21  and  31  at mutually different timings according to the rotating direction of the motor in the following manner. 
         [0130]    If the motor  46  is further run in the state shown in  FIG. 9 , the charging lever  29  further rotates counterclockwise, and the charging lever projection  29   d  presses the unlocking lever projection  60   c , thereby turning the unlocking lever  60  counterclockwise against the biasing force applied from the charging lever returning spring  30 . 
         [0131]    As the unlocking lever  60  rotates counterclockwise, the front curtain unlocking projection  60   a  soon kicks the unlocking claw  37   c  of the front curtain locking lever  37 , when the front curtain locking lever  37  rotates clockwise against the biasing force applied from the front curtain locking lever spring  54 , thus unlocking the locking portion  37   b  from the front curtain driving lever locking portion  28   c . Then, the front curtain driving lever  28  rotates clockwise under the biasing force applied from the front curtain setting spring  27  until the front curtain setting lever contacting portion  24   a  contacts with the front curtain driving lever contacting portion  28   b , and the group of front curtains  21  covers the aperture  11   a . Then, a state where the front curtain setting cam  29   b  is in contact with the front curtain charging input portion  24   c  and the group of front curtains  21  covers the aperture  11   a  is maintained. At the same time, the front curtain locking lever switch turning portion  37   d  turns ON the front curtain unlocking sensing switch  47  (in STEP  6  shown in  FIG. 14  and at the time t 3  shown in  FIG. 16 ). 
         [0132]    As the motor  46  is further run and as the charging lever  29  further rotates counterclockwise, the missing tooth gear  40  soon disengages itself from the charging lever missing tooth gear portion  29   e . As a result, the charging lever  29  and the unlocking lever  60  both rotate clockwise under the biasing force applied from the charging lever returning spring  30 . In the meantime, the front curtain charging input portion  24   c  breaks off contact with the front curtain setting cam  29   b  and the rear curtain charging input portion  34   c  breaks off contact with the rear curtain setting cam  29   c.    
         [0133]    Before the missing tooth gear  40  disengages itself from the charging lever missing tooth gear portion  29   e  of the charging lever  29 , power starts to be supplied to the front and rear curtain electromagnets  26  and  36 . As a result, the front and rear curtain guiding pieces  24   b  and  34   b  get attracted to the front and rear curtain electromagnets  26  and  36 , respectively. In this manner, the front and rear curtain setting levers  24  and  34  can maintain the charged state. 
         [0134]    At a point in time when the group of front curtains  21  covers the aperture  11   a , the CMOS image sensor  110  gets a reference image (i.e., a so-called “dummy image”) to reduce a variation in image between respective objects (in STEP  7  and at the time t 4  shown in  FIG. 16 ). 
         [0135]    —Slit Exposure— 
         [0136]    In response to a release instruction issued by the camera controller  140 , the supply of power to the front curtain electromagnet  26  is cut off (in STEP  8 ). Then, the front curtain setting lever  24  rotates counterclockwise under the biasing force applied from the front curtain running spring  25 . At this time, the front curtain driving lever  28  also rotates along with the front curtain setting lever  24  to run the group of front curtains  21 . And the CMOS image sensor  110  starts to be exposed to light from under the aperture  11   a . Subsequently, when a preset exposure time passes since the supply of power to the front curtain electromagnet  26  was cut off, the supply of power to the rear curtain electromagnet  36  is cut off this time (in STEP  9  and at the time t 5  shown in  FIG. 16 ). The exposure time is set by the camera controller  140  by reference to exposure information and other pieces of information. Then, the rear curtain setting lever  34  rotates counterclockwise under the biasing force applied from the rear curtain running spring  35 . At this time, the rear curtain driving lever  39  also rotates along with the rear curtain setting lever  34  to run the group of rear curtains  31  and cover the aperture  11   a  from under the aperture  11   a . And the CMOS image sensor  110  starts to be exposed to light that has come through a slit formed by the groups of front and rear curtains  21  and  31 . An exposing operation using light that has come through such a slit will be referred to herein as “slit exposure shooting”. When the groups of front and rear curtains  21  and  31  have run, the focal plane shuttering apparatus  190  will be back to the state shown in  FIG. 6  again. After that, the charging operation will be performed to make the focal plane shuttering apparatus  190  enter the state shown in  FIG. 8 . In parallel with the rear curtain charging operation shown in  FIG. 8 , the camera controller  140  performs a control operation so as to read the image data that has been gotten by the CMOS image sensor  110 . After the image data has been read, the focal plane shuttering apparatus  190  will enter the state shown in  FIG. 9  to prepare for the next shooting session (at the time t 6  shown in  FIG. 16 ). By performing the charging operation and the read operation in parallel in this manner, the time it takes to prepare for the next shooting session can be shortened. For example, the interval between continuous shooting sessions can be shortened and continuous shooting can be carried out at high speeds even in the AF mode. 
         [0137]    It should be noted that when the group of rear curtains  31  has run, the locking portion  52   b  of the rear curtain locking lever  52  will be locked to the rear curtain driving lever locking portion  39   c  as shown in  FIG. 6 . 
         [0138]    —Normally Closed Charging Mechanism— 
         [0139]    Next, a normally closed charging mechanism will be described. 
         [0140]    The components of the focal plane shuttering apparatus  190  that form the normally closed charging mechanism are quite the same as the components of the focal plane shuttering apparatus  190  that form the normally opened charging mechanism. Thus, those components will not be described in detail all over again to avoid redundancies. 
         [0141]    As shown in  FIG. 7 , the unlocking lever missing tooth gear portion  60   d  is supported along with the unlocking lever  60 . The unlocking lever missing tooth gear portion  60   d  is engageable with the missing tooth gear  50 , which is supported rotatably on the shutter base plate  11 . The missing tooth gear  50  is comprised of stacked gears and has a gear portion, which has teeth over the entire periphery thereof and which is engageable with a group of coupled gears  48 . The group of coupled gears  48  is made up of three gears that are engaged in series with each other. One of the three gears that form the group of coupled gears  48  is engageable at one end with the planetary gear  41 . Another one of the three gears at the other end has the same shaft as the sun gear  43  and is rotatable on that shaft and engageable with the missing tooth gear  50 . 
         [0142]    —Running Finished State— 
         [0143]      FIG. 11  illustrates a state where the focal plane shuttering apparatus has gotten a shooting session done (i.e., a state where the rear curtain has run). 
         [0144]    The group of front curtains  21  has gotten retracted to over the aperture  11   a  under the biasing force applied from the front curtain running spring  25 . On the other hand, as shown in  FIG. 11 , the front curtain setting and driving levers  24  and  28  have their contacting portions  24   a  and  28   b  kept in contact with each other under the biasing forces applied from the front curtain setting and running springs  27  and  25 , and both stay in their counterclockwise rotated positions. Meanwhile, the group of rear curtains  31  covers the aperture  11   a  under the biasing force applied from the rear curtain running spring  35 . On the other hand, the rear curtain setting and driving levers  34  and  39  have their contacting portions  34   a  and  39   b  kept in contact with each other under the biasing force applied from the rear curtain running spring  35 , and both stay in their counterclockwise rotated positions. 
         [0145]    —Charging Operation— 
         [0146]      FIG. 11  illustrates a state where the rear curtain has run in the normally closed state.  FIG. 12  illustrates a state during a charging operation.  FIG. 13  illustrates a shooting standby state where the charging operation has gotten done on the front and rear curtains.  FIG. 15  is a flowchart showing the procedure of a slit exposure shooting session in the normally closed state. And  FIG. 17  is a timing diagram showing the timings of operation of the slit exposure shooting session in the normally closed state. 
         [0147]    Hereinafter, the charging operation will be described mainly with reference to  FIG. 15 . 
         [0148]    In the running finished state shown in  FIG. 11 , power is supplied to the motor  46  so that the motor  46  turns in the opposite direction from in the normally opened state (in STEP  11  and at the time t 11  shown in  FIG. 17 ). When the motor  46  rotates the worm gear  44 , the sun gear  43  with a worm wheel that engages with the worm gear  44  is turned counterclockwise. As a result, the planetary carrier  42  also rotates counterclockwise under the rotational load and the first rotation preventing portion  42   a  contacts with the first stopper (not shown) on the shutter base plate  11 . In the meantime, the planetary gear  41  shown in  FIG. 7  moves (i.e., revolves) along with its planetary carrier rotating. When the planetary gear  41  stops revolving due to contact of the first rotation preventing portion  42   a  with the first stopper, the planetary gear  41  is still engaged with the coupled gear  48 . Thereafter, the planetary gear  41  itself rotates clockwise, thereby turning the coupled gear  48  and the missing tooth gear  50  clockwise. At this time, the missing tooth gear  40  tries to rotate clockwise due to slight friction between the missing tooth gear  50  and itself. However, the first rotation preventing portion  42   a  contacts with the missing teeth of the missing tooth gear  40 , thus preventing the missing tooth gear from rotating. On the other hand, the missing tooth portion of the missing tooth gear  50  gets engaged with the unlocking lever missing tooth gear portion  60   d  of the unlocking lever  60 , thereby turning the unlocking lever missing tooth gear portion  60   d  counterclockwise on the charging lever shaft  29   a . The unlocking lever  60  which forms part of the missing tooth gear portion  60   d  rotates counterclockwise against the biasing force applied from the charging lever returning spring  30 . 
         [0149]    As the unlocking lever  60  rotates, the charging lever  29  rotates counterclockwise and the rear curtain setting cam  29   c  presses the rear curtain charging input portion  34   c . As a result, the rear curtain setting lever  34  rotates clockwise. 
         [0150]    When the front and rear curtain unlocking portions  60   a  and  60   b  of the unlocking lever  60  kick the unlocking claws  37   e  and  52   e , respectively, substantially at the same time, the front and rear curtain locking levers  37  and  52  rotate clockwise against the biasing forces applied from the front and rear curtain locking lever springs  54  and  53 , respectively. 
         [0151]    The front curtain driving lever  28  has its locking portion  28   c  disengaged from the locking portion  37   b  of the front curtain locking lever  37 . Meanwhile, the rear curtain driving lever  39  has its locking portion  39   c  disengaged from the locking portion  52   b  of the rear curtain locking lever  52 . And under the biasing force applied from the front curtain setting spring  27 , the contacting portion  24   a  of the front curtain setting lever  24  contacts with the contacting portion  28   b  of the front curtain driving lever  28 . As a result, the front curtain setting lever  24  rotates along with the front curtain driving lever  28 . On the other hand, under the biasing force applied from the rear curtain setting spring  55 , the contacting portion  34   a  of the rear curtain setting lever  34  contacts with the coupling pin  39   a  of the rear curtain driving lever  39 . As a result, the rear curtain setting lever  34  rotates along with the rear curtain driving lever  39 . Consequently, the front and rear curtain locking lever switch turning portions  37   d  and  52   d  turn ON the front and rear curtain unlocking sensing switches  47  and  57 , respectively, substantially at the same time (in STEP  13 ). 
         [0152]      FIG. 12  illustrates a state during the charging operation. As shown in  FIG. 12 , the aperture  11   a  is always covered with the groups of front and rear curtains  21  and  31  throughout the charging operation. As a result, reading image data from the CMOS image sensor  110  and getting a dummy image (in STEP  12  and at the time t 12  shown in  FIG. 17 ) can be performed in parallel with the charging operation. 
         [0153]    When the rear curtain charging input portion  34   c  reaches the outermost portion of the rear curtain setting cam  29   c , the rear curtain guiding piece  34   b  gets pressed against the rear curtain electromagnet  36 . In the same way, the front curtain setting cam  29   b  presses the front curtain charging input portion  24   c , and the front curtain setting lever  24  rotates clockwise. The front curtain charging input portion  24   c  is driven in the outer peripheral direction of the front curtain setting cam  29   b  and reaches the outermost portion, when the front curtain guiding piece  24   b  gets pressed against the front curtain electromagnet  26 . 
         [0154]    Consequently, this focal plane shuttering apparatus has a so-called “normally closed” function to keep the aperture  11   a  always closed except during exposure. 
         [0155]    —Slit Exposure Standby State— 
         [0156]      FIG. 13  illustrates a slit exposure standby state of the focal plane shuttering apparatus  190 . 
         [0157]    Specifically, as the motor  46  is further run in the state shown in  FIG. 12  and as the unlocking lever  60  further rotates counterclockwise, the missing tooth gear  50  soon disengages itself from the unlocking lever missing tooth gear portion  60   d . As a result, the unlocking lever  60  and the charging lever  29  both rotate clockwise under the biasing force applied from the charging lever returning spring  30 . In the meantime, the front curtain charging input portion  24   c  breaks off contact with the front curtain setting cam  29   b  and the rear curtain charging input portion  34   c  breaks off contact with the rear curtain setting cam  29   c.    
         [0158]    Before the missing tooth gear  50  disengages itself from the missing tooth gear portion  60   d  of the unlocking lever  60 , power starts to be supplied to the front and rear curtain electromagnets  26  and  36 . As a result, the front and rear curtain guiding pieces  24   b  and  34   b  get attracted to the front and rear curtain electromagnets  26  and  36 , respectively. In this manner, the front and rear curtain setting levers  24  and  34  can maintain the charged state (in the period between the times t 11  and t 12  shown in  FIG. 17 ). 
         [0159]    —Slit Exposure— 
         [0160]    When the user presses the release button  131 , the CMOS image sensor  110  gets necessary shooting information about photometry, for example. When every piece of necessary shooting information is gotten, the camera controller  140  permits the release. In response to a release instruction issued by the camera controller  140  (in STEP  14 ), the supply of power to the front curtain electromagnet  26  is cut off (in STEP  15 ). Then, the front curtain setting lever  24  rotates counterclockwise under the biasing force applied from the front curtain running spring  25 . At this time, the front curtain driving lever  28  also rotates along with the front curtain setting lever  24  to run the group of front curtains  21 . And the CMOS image sensor  110  starts to be exposed to light from under the aperture  11   a . Subsequently, when a preset exposure time passes since the supply of power to the front curtain electromagnet  26  was cut off, the supply of power to the rear curtain electromagnet  36  is cut off this time (in STEP  16 ). The exposure time is set by the camera controller  140  by reference to exposure information and other pieces of information. Then, the rear curtain setting lever  34  rotates counterclockwise under the biasing force applied from the rear curtain running spring  35 . At this time, the rear curtain driving lever  39  also rotates along with the rear curtain setting lever  34  to run the group of rear curtains  31  and cover the aperture  11   a  from under the aperture  11   a . And the CMOS image sensor  110  starts to be exposed to light that has come through a slit formed by the groups of front and rear curtains  21  and  31  (at the time t 13  shown in  FIG. 17 ). An exposing operation using light that has come through such a slit will be referred to herein as “slit exposure shooting”. When the groups of front and rear curtains  21  and  31  have run, the focal plane shuttering apparatus  190  will be back to the state shown in  FIG. 11  again. 
         [0161]    (3: Normally Closed Continuous Shooting Session in Normally Opened State) 
         [0162]    Next, it will be described how to carry out a normally closed continuous shooting session in the normally opened state. Since a sequence in the normally closed state can get done more quickly than a sequence in the normally opened state, continuous shooting can be carried out at very high speeds when AF is not needed during that continuous shooting, for example. 
         [0163]      FIG. 18  is a flowchart showing the procedure of a normally closed continuous shooting session to be carried out in the normally opened state.  FIG. 19  is a timing diagram showing the timings of operation of the normally closed continuous shooting session to be carried out in the normally opened state. 
         [0164]    Hereinafter, it will be described with reference to  FIG. 18  how this focal plane shuttering apparatus operates in a situation where the user has selected a high-speed continuous shooting mode that uses the normally closed technique in a live view mode in the normally opened state and has pressed the release button. 
         [0165]    When the release button  131  is pressed (in STEP  21 ), power starts to be supplied to the front and rear curtain electromagnets  26  and  36  in accordance with a release instruction issued by the camera controller  140 . The motor  46  runs in the rotating direction for the normally opened state, thus getting the front and rear curtain guiding pieces  24   b  and  34   b  attracted to the front and rear curtain electromagnets  26  and  36 , respectively. At substantially the same time, the motor  46  runs in the rotating direction for the normally opened state (in STEP  21  and at the time t 21  shown in  FIG. 19 ). As the charging lever  29  rotates counterclockwise, the front curtain unlocking projection  60   a  kicks the unlocking claw A  37   c  of the front curtain locking lever  37 , thus turning the front curtain locking lever  37  against the biasing force applied from the front curtain locking lever spring  54  to unlock the locking portion  37   b  from the front curtain driving lever locking portion  28   c . Then, under the biasing force applied from the front curtain setting spring  27 , the front curtain driving lever  28  rotates clockwise until the front curtain setting lever contacting portion  24   a  contacts with the front curtain driving lever contacting portion  28   b , and the group of front curtains  21  covers the aperture  11   a . And the front curtain setting cam  29   b  is in contact with the front curtain charging input portion  24   c , and the group of front curtains  21  keeps covering the aperture  11   a . At the same time, the front curtain locking lever switch turning portion  37   d  turns ON the front curtain unlocking sensing switch  47  (in STEP  23 ) and stops running the motor  46  (at the time t 22  shown in  FIG. 19 ). 
         [0166]    The power that has been supplied to the front curtain electromagnet  26  is cut off (in STEP  24 ), when the front curtain setting lever  24  rotates counterclockwise under the biasing force applied from the front curtain running spring  25 . At this time, the front curtain driving lever  28  also rotates along with the front curtain setting lever  24  to run the group of front curtains  21 . And the CMOS image sensor  110  starts to be exposed to light from under the aperture  11   a . Subsequently, when a preset exposure time passes since the supply of power to the front curtain electromagnet  26  was cut off, the supply of power to the rear curtain electromagnet  36  is cut off this time (in STEP  25 ). The exposure time is set by the camera controller  140  by reference to exposure information and other pieces of information. Then, the rear curtain setting lever  34  rotates counterclockwise under the biasing force applied from the rear curtain running spring  35 . At this time, the rear curtain driving lever  39  also rotates along with the rear curtain setting lever  34  to run the group of rear curtains  31  and cover the aperture  11   a  from under the aperture  11   a . And the CMOS image sensor  110  starts to be exposed to light that has come through a slit formed by the groups of front and rear curtains  21  and  31 . When the groups of front and rear curtains  21  and  31  have run, the focal plane shuttering apparatus  190  will be back to the state shown in  FIG. 6  again (at the time t 23  shown in  FIG. 19 ). 
         [0167]    In this case, if the release button  131  is still ON (in STEP  26 ), the motor  46  is run in the rotating direction for the normally closed state. As described above, the aperture  11   a  is always covered during charging as in the charging operation to be performed in the normally closed state. That is why reading image data from the CMOS image sensor  110  and getting the dummy image (in STEP  27 ) are carried out in parallel with the charging operation (at the time t 24  shown in  FIG. 19 ). 
         [0168]    When reading from the image sensor is done (at the time t 25  shown in  FIG. 19 ), the motor  46  further runs, and the front or rear curtain locking lever switch turning portion  37   d  or  52   d  senses the turn ON of the front or rear curtain unlocking sensing switch  47  or  57  (in STEP  28 ). Then, the motor  46  is stopped and the process advances to STEP  24 , in which an exposure process is carried out all over again (at the time t 26  shown in  FIG. 19 ). 
         [0169]    If it turns out in STEP  26  that the release button  131  has been turned OFF, the continuous shooting session needs to be stopped to recover the live view state. 
         [0170]    In that case, the motor  46  is run in the rotating direction for the normally opened state (in STEP  29  and at the time t 27  shown in  FIG. 19 ). Even though the groups of front and rear curtains  21  and  31  are charged, it is the same as the charging operation in the normally opened state and the group of rear curtains  31  covers the aperture  11   a . That is why image data can be read from the CMOS image sensor  110 . When reading from the CMOS image sensor  110  and getting the dummy image are done (in STEP  30 ), the motor  46  further runs and the charging lever  29  further rotates counterclockwise. Then, the focal plane shuttering apparatus  190  enters the state shown in  FIG. 9 , in which the charging operation has been done on the front and rear curtains to realize the live view function (at the time t 28  shown in  FIG. 19 ). 
         [0171]    Portion (a) of  FIG. 20  is a partial cross-sectional view of the focal plane shuttering apparatus  190  in the normally opened state, while portion (b) of  FIG. 20  is a partial cross-sectional view of the focal plane shuttering apparatus  190  in the normally closed state. 
         [0172]    As can be seen from the foregoing description, the focal plane shuttering apparatus  190  of this embodiment may be implemented as either a normally opened focal plane shuttering apparatus which can make a slit exposure using front and rear curtains and which can keep the aperture covered with the front curtain retracted while charging the front and rear curtains or a normally closed focal plane shuttering apparatus which can always keep the aperture closed except during a slit exposure that uses the front and rear curtains. Thus, the normally opened mode can be used in performing continuous shooting sessions with AF kept ON, and the normally closed mode can be used in performing continuous shooting sessions at higher speeds. Furthermore, the focal plane shuttering apparatus  190  of this embodiment can be used even in a so-called “single-lens reflex camera” that realizes an optical viewfinder by arranging a quick turn mirror in the optical path for shooting and in a so-called “mirrorless single lens camera” that can get a live viewfinder shooting done by an image sensor without arranging any quick turn mirror. 
         [0173]    Although various embodiments have been described herein as just examples of the technique of the present disclosure, various modifications, replacements, additions or omissions can be readily made on those embodiments as needed and the present disclosure is intended to cover all of those variations. Also, a new embodiment can also be created by combining respective elements that have been described for those embodiments disclosed herein. 
         [0174]    Thus, some other embodiments will be described. 
         [0175]    The embodiment described above is an interchangeable lens type digital camera, of which the camera body  100  and lens unit  200  are separable from each other. However, the same effects can also be achieved by a digital camera of which the lens unit is fixed on its camera body and in which exposure is controlled by the focal plane shuttering apparatus. 
         [0176]    Although a slit exposure has been described in the foregoing description of embodiments, an electronic front curtain exposure can be carried out just by turning ON only the rear curtain Mg at the front curtain/rear curtain Mg_ON timing in each flowchart. 
         [0177]    In  FIGS. 1 to 5 , the camera body  100  is illustrated as an image capture device. After the camera body  100  has finished a shooting session, the camera controller  140  of the camera body  100  can change the methods to drive the focal plane shuttering apparatus  190  into any of various methods. 
         [0178]    For example, after the camera body  100  has finished the shooting session, the camera controller  140  may control the focal plane shuttering apparatus  190  so that the apparatus  190  is driven by a normally opened driving method. 
         [0179]    If the modes of operation of the camera body  100  are changed by the user from a single shooting mode into a continuous shooting mode, or vice versa, the camera controller  140  may detect the change of the modes of operation and may change the methods to drive the focal plane shuttering apparatus  190 . Specifically, if the modes of operation are changed into the single shooting mode, the camera controller  140  may change the methods to drive the focal plane shuttering apparatus  190  into a normally opened driving method. On the other hand, if the modes of operation are changed into the continuous shooting mode, the camera controller  140  may change the methods to drive the focal plane shuttering apparatus  190  into a normally closed driving method. 
         [0180]    In a situation where the continuous shooting mode described above is subdivided into multiple modes with mutually different shooting intervals, when a continuous shooting mode with the longest shooting interval is selected, the camera controller  140  may change the methods to drive the focal plane shuttering apparatus  190  into the normally closed driving method. But when a different continuous shooting mode is selected, the camera controller  140  may change the methods to drive the focal plane shuttering apparatus  190  into the normally opened driving method. 
         [0181]    Furthermore, if the power supply unit is disconnected from the power supplying section during a shooting session and then restarts supplying power to the power supplying section, the camera controller  140  may change the methods to drive the focal plane shuttering apparatus  190  into the normally closed driving method. Or if the power supplying ability of the power supply unit turns out to be less than a predetermined power value while a continuous shooting session is carried out by the normally closed driving method, the camera controller  140  may change the methods to drive the focal plane shuttering apparatus  190  into the normally opened driving method and then stop performing the continuous shooting session. Optionally, the ratio of remaining power to the maximum permissible power may be defined instead of the predetermined power value. 
         [0182]    Alternatively, when the power supply unit starts supplying power, the camera controller  140  may change the methods to drive the focal plane shuttering apparatus  190  into the normally opened driving method. 
         [0183]    Various embodiments have been described as examples of the technique of the present disclosure by providing the accompanying drawings and a detailed description for that purpose. 
         [0184]    That is why the elements illustrated on those drawings and/or mentioned in the foregoing description include not only essential elements that need to be used to overcome the problems described above but also other inessential elements that do not have to be used to overcome those problems but are just mentioned or illustrated to give an example of the technique of the present disclosure. Therefore, please do not make a superficial decision that those inessential additional elements are indispensable ones simply because they are illustrated or mentioned on the drawings or the description. 
         [0185]    Also, the embodiments disclosed herein are just an example of the technique of the present disclosure, and therefore, can be subjected to various modifications, replacements, additions or omissions as long as those variations fall within the scope of the present disclosure as defined by the appended claims and can be called equivalents. 
         [0186]    The present disclosure is applicable to a focal plane shuttering apparatus. 
         [0187]    While the present disclosure has been described with respect to preferred embodiments thereof, it will be apparent to those skilled in the art that the disclosed disclosure may be modified in numerous ways and may assume many embodiments other than those specifically described above. Accordingly, it is intended by the appended claims to cover all modifications of the disclosure that fall within the true spirit and scope of the disclosure.