CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2010-000958, filed on Jan. 6, 2010, and Japanese Patent Application No. 2010-279842, filed on Dec. 15, 2010. The entire disclosure of Japanese Patent Applications No. 2010-000958 and Japanese Patent Application No. 2010-279842 are hereby incorporated herein by reference. 
       BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The technology disclosed herein generally relates to a focal plane shutter device. More specifically, the technology disclosed herein relates to a focal plane shutter device used in an imaging device. 
         [0004]    2. Background Information 
         [0005]    Japanese Patent Laid-Open Publication JP2004-061865 discloses a focal plane shutter device having a so-called normally open function. 
         [0006]    Japanese Patent Laid-Open Publication JP2007-316503 discloses a focal plane shutter device corresponding to electronic front curtain photography. This focal plane shutter device utilizes an electronic shutter function of an imaging element to realize a function of the front curtain, and thus, it is possible to take pictures by merely running the rear curtain without using the front curtain. 
         [0007]    In the focal plane shutter device disclosed in JP2004-061865, if taking pictures is made to correspond to electronic front curtain photography, it is necessary that the front curtain runs once at a charge position (i.e., in a state where an aperture is closed), but this raises a problem in that the live view, for example, needs to be stopped. 
         [0008]    Further, in the focal plane shutter device disclosed in JP2004-061865, the front curtain and the rear curtain are simultaneously charged, and as a result, a load of a motor becomes to large at the time of charging. 
         [0009]    Moreover, the focal plane shutter device disclosed in JP2007-316503 does not include the front curtain, and it is therefore not possible to perform a slit exposure using the front curtain and the rear curtain. 
       SUMMARY 
       [0010]    One object of the technology discussed herein is to provide a focal plane shutter device capable of performing slit exposure photography using a front curtain and a rear curtain, and also capable of reducing a load of a drive source at the time of charging the front curtain and the rear curtain. 
         [0011]    Another object of the technology disclosed herein is to provide a focal plane shutter device capable of performing slit exposure photography using a front curtain and a rear curtain, and also capable of maintaining an aperture in an open state at the time of charging the front curtain and the rear curtain. 
         [0012]    To achieve these objectives, a focal plane shutter device is provided with a shutter base plate, a front curtain, a first urging member, a rear curtain, a second urging member, and a charge mechanism. The shutter base plate defines an opening. The front curtain is configured to move between a first front curtain position to cover the opening and a second front curtain position to uncover the opening. The first urging member is configured to apply an urging force to the front curtain to move the front curtain from the first front curtain position to the second front curtain position. The rear curtain is configured to move between a first rear curtain position to cover the opening and a second rear curtain position to uncover the opening. The second urging member is configured to apply an urging force to the rear curtain to move the rear curtain from the second rear curtain position to the first rear curtain position. The charge mechanism is configured to apply a first biasing force to resist the urging force of the first urging member and a second biasing force to resist the urging force of the second urging member. The first biasing force applied by charge mechanism terminates at a different time than the second biasing force applied by charge mechanism. 
         [0013]    These and other objects, features, aspects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses embodiments of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0014]    Referring now to the attached drawings which form a part of this original disclosure: 
           [0015]      FIG. 1  is a perspective view of a digital camera  1 ; 
           [0016]      FIG. 2  is a perspective view of a camera body  100 ; 
           [0017]      FIG. 3  is a block diagram of the digital camera  1 ; 
           [0018]      FIG. 4  is a simplified cross section of the digital camera  1 ; 
           [0019]      FIG. 5  is a rear view of the camera body  100 ; 
           [0020]      FIG. 6  is a state diagram of a focal plane shutter device  190  in a state where a rear curtain completes running; 
           [0021]      FIG. 7  is a detailed view of main parts in  FIG. 6 ; 
           [0022]      FIG. 8  is a state diagram of the focal plane shutter device  190  in a charge completion state; 
           [0023]      FIG. 9  is a detailed view of main parts in  FIG. 8 ; 
           [0024]      FIG. 10  is a state diagram of the focal plane shutter device  190  in a slit exposure standby state; 
           [0025]      FIG. 11  is a detailed view of main parts in  FIG. 10 ; 
           [0026]      FIG. 12  is a state diagram of the focal plane shutter device  190  in a rear-curtain charge completion state; 
           [0027]      FIG. 13  is a detailed view of main parts in  FIG. 12 ; 
           [0028]      FIG. 14  is a state diagram of the focal plane shutter device  190  in an electronic front curtain photography standby state; 
           [0029]      FIG. 15  is a detailed view of main parts in  FIG. 14 ; 
           [0030]      FIG. 16A  is a plan view of a front-curtain drive lever  28  and  FIG. 16B  is a plan view of a front-curtain set lever  24 ; 
           [0031]      FIG. 17  is a plan view of a rear-curtain set lever  34 ; 
           [0032]      FIG. 18A  is a plan view of a charge lever  29  and  FIG. 18B  is an enlarged partial view of the charge lever  29 ; 
           [0033]      FIGS. 19A and 19B  are operation diagrams of the front-curtain drive lever  28  and the charge lever  29 ; 
           [0034]      FIG. 20  is a flowchart of slit exposure photography; 
           [0035]      FIG. 21  is a flowchart of electronic front curtain photography; 
           [0036]      FIG. 22A  shows a relation between a rotation angle of a charge gear and a bias force (reference example) and  FIG. 22B  shows a relation between the rotation angle of the charge gear and the bias force (first embodiment); 
           [0037]      FIG. 23  is a state diagram of a focal plane shutter device  290  in a state where a rear curtain completes running; 
           [0038]      FIG. 24  is a detailed view of main parts in  FIG. 23 ; 
           [0039]      FIG. 25  is a state diagram of the focal plane shutter device  290  in a charge completion state; 
           [0040]      FIG. 26  is a detailed view of main parts in  FIG. 25 ; 
           [0041]      FIG. 27  is a state diagram of the focal plane shutter device  290  in a slit exposure photography standby state; 
           [0042]      FIG. 28  is a detailed view of main parts in  FIG. 27 ; 
           [0043]      FIG. 29  is a state diagram of the focal plane shutter device  290  in a rear-curtain charge completion state; 
           [0044]      FIG. 30  is a detailed view of main parts in  FIG. 29 ; 
           [0045]      FIG. 31  is a state diagram of the focal plane shutter device  290  in an electronic front curtain photography standby state; and 
           [0046]      FIG. 32  is a detailed view of main parts in  FIG. 31 . 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0047]    Selected embodiments will now be explained with reference to the drawings. It will be apparent to those skilled in the art from this disclosure that the following descriptions of the embodiments are provided for illustration only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents. 
       First Embodiment 
       [0048]    1: Digital Camera 
         [0049]    By using drawings, an overview of a digital camera  1  on which a focal plane shutter device  190  is mounted will be explained. It is noted that the focal plane shutter device  190  can be mounted on cameras other than the digital camera  1  of the embodiments. 
         [0050]      FIG. 1  is a perspective view of the digital camera  1  according to the first embodiment.  FIG. 2  is a perspective view of a camera body  100 .  FIG. 3  is a functional block diagram of the digital camera  1 . 
         [0051]    The digital camera  1  is an interchangeable-lens-type digital camera that includes the camera body  100  and a lens unit  200  attachable to the camera body  100 . 
         [0052]      FIG. 4  is a simplified cross section of the digital camera  1 .  FIG. 5  is a rear view of the camera body  100 . The camera body  100  mainly includes: a Complementary Metal Oxide Semiconductor (CMOS) image sensor  110 , a CMOS circuit board  113 , a camera monitor  120 , an operation part  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 shutter device  190 . 
         [0053]    The CMOS image sensor  110  (an example of an imaging element) converts an optical image of a subject (hereinafter, may also be referred to as a subject image) incident via the lens unit  200 , into image data. The produced image data is digitalized by an AD converter  111  of the CMOS circuit board  113 . The image data digitalized by the AD converter  111  is subjected to various imaging processing in the camera controller  140 . The various imaging processing referred to here include, for example, gamma correction processing, white balance correction processing, scratch correction processing, YC conversion processing, electronic zoom processing, and JPEG compression processing. 
         [0054]    The CMOS image sensor  110  operates based on a timing signal generated by a timing generator  112 . The CMOS image sensor  110  can obtain still picture data and moving picture data under control by the CMOS circuit board  113 . The obtained moving picture data is also used for displaying through-images. It is noted that the still picture data and the moving picture data are examples of the image data. 
         [0055]    A “through-image” here is an image out of the moving picture data that is not recorded on a memory card  171 . Primarily, the through-image is a moving picture, and is displayed on the camera monitor  120  to decide the composition of a moving or a still picture. 
         [0056]    The CMOS image sensor  110  can obtain a low-resolution moving picture used as the through-image and can obtain a high-resolution moving picture used for recording. The high-resolution moving picture may include a moving picture of an HD size (High-Definition size: 1920×1080 pixels), for example. It is noted that the CMOS image sensor  110  is an example of the imaging element for converting the optical image of the subject into an electric image signal. The imaging element is a concept encompassing not only the CMOS image sensor  110  but also an opto-electrical conversion element such as a CCD image sensor. 
         [0057]    The CMOS image sensor  110  has an electronic front curtain function for sequentially resetting a pixel in a running direction R (see  FIG. 6 ) of a front curtain  21  described later. 
         [0058]    The CMOS circuit board  113  is a circuit board for controlling the CMOS image sensor  110 . The CMOS circuit board  113  is a circuit board for performing predetermined processing on the image data outputted from the CMOS image sensor  110 , and includes the timing generator  112  and the AD converter  111 . The CMOS circuit board  113  is an example of an imaging element circuit board for controlling the drive of the imaging element and performing predetermined processing such as AD conversion on the image data outputted from the imaging element. 
         [0059]    The camera monitor  120  is, for example, a liquid crystal display and displays, for example, an image represented by display-use image data. The display-use image data is produced by the camera controller  140 . The display-use image data is data for displaying image data which undergoes imaging processing, a photography condition of the digital camera  1 , and an operation menu, as an image, for example. The camera monitor  120  is capable of selectively displaying the moving picture and the still picture. 
         [0060]    The camera monitor  120  is provided to the camera body  100 . In the first embodiment, the camera monitor  120  is disposed on the rear face of the camera body  100 , however, the camera monitor  120  may also be disposed on anywhere of the camera body  100 . 
         [0061]    It is noted that the camera monitor  120  is an example of a display part provided to the camera body  100 . Other examples of the display part include means capable of displaying an image such as an organic electroluminescence, an inorganic electroluminescence, and a plasma display panel. Moreover, the display part need not be provided on the rear face of the camera body  100 , and may be provided on a side face, a top face, or another such place. 
         [0062]    The operation part  130  receives operations by a user. Specifically, as shown in  FIGS. 6 and 7 , the operation part  130  includes a release button  131  for receiving a focal plane shutter operation by the user, and a power switch  132  that is a rotary dial switch provided on the top face of the camera body  100 . The operation part  130  may suffice if it is possible to receive the operations by the user, and includes a button, a lever, a dial, a touch panel, etc. 
         [0063]    The camera controller  140  (an example of a controller) controls each part of the camera body  100 . The camera controller  140  receives commands from the operation part  130 . The camera controller  140  transmits a signal used for controlling the lens unit  200  to a lens controller  240  via the body mount  150  and a lens mount  250 , and indirectly controls each part of the lens unit  200 . That is, the camera controller  140  controls the entire digital camera  1 . 
         [0064]    The camera controller  140  controls the CMOS circuit board  113 . Specifically, the camera controller  140  transmits a control signal to the CMOS circuit board  113 , and the CMOS circuit board  113  controls the CMOS image sensor  110  based on the received control signal. That is, the camera controller  140  controls the CMOS image sensor  110 . Moreover, the camera controller  140  obtains the image data which is produced by the CMOS image sensor  110  and on which the predetermined processing such as AD conversion has been performed by the CMOS circuit board  113 , and further performs processing on the obtained image data. For example, the camera controller  140  produces display-use image data, recording-use moving picture data, etc., from the image data processed by the CMOS circuit board  113 . 
         [0065]    Further, the camera controller  140  controls the focal plane shutter device  190  described later. Specifically, when photographing by using an electronic front curtain photography function, the camera controller  140  controls the motor  46  so that a charge lever  29  stops at a second charge completion position. The camera controller  140  establishes an electronic front curtain photography standby state of the focal plane shutter device  190  when a charge mechanism  194  completes imparting a rear-curtain running spring  35  with a second bias force F 23  (see  FIG. 7 ) and the charge mechanism  194  does not complete the imparting a front-curtain running spring  25  with a first biasing force F 13  (see  FIG. 13 ). 
         [0066]    The memory card  171  is attachable to a card slot  170 . The card slot  170  controls the memory card  171  based on the control signal transmitted from the camera controller  140 . Specifically, the card slot  170  stores the image data on the memory card  171 . The card slot  170  outputs the image data from the memory card  171 . Moreover, the card slot  170  stores the moving picture data on the memory card  171 . The card slot  170  outputs the moving picture data from the memory card  171 . 
         [0067]    The memory card  171  is capable of storing the image data that is produced through imaging processing by the camera controller  140 . For example, the memory card  171  is capable of storing a non-compressed RAW image file, a compressed JPEG image file, etc. Moreover, the memory card  171  is also capable of outputting via the card slot  170  image data or image file that has been previously stored inside the memory card  171 . The image data or the image file outputted from the memory card  171  is subjected to imaging processing by the camera controller  140 . For example, the camera controller  140  decompresses the image data or the image file obtained from the memory card  171  so as to produce the display-use image data. 
         [0068]    The memory card  171  is further capable of storing the moving picture data that is produced through imaging processing by the camera controller  140 . For example, the memory card  171  is capable of storing the moving picture file compressed according to H.264/AVC that is a moving picture compression standard. Moreover, the memory card  171  is capable of outputting via the card slot  170  the moving picture data or moving picture file that has been previously stored inside the memory card  171 . The moving picture data or the moving picture file outputted from the memory card  171  is subjected to imaging processing in the camera controller  140 . For example, the camera controller  140  decompresses the moving picture data or the moving picture file obtained from the memory card  171  so as to produce the display-use image data. 
         [0069]    It is noted that the memory card  171  is an example of a storage part. The storage part may be attachable to the camera body  100 , as in the case of the memory card  171 , and may also be fixed to the digital camera  1 . 
         [0070]    The power supply  160  supplies each part with power used in the digital camera  1 . The power supply  160  may be a dry battery and a rechargeable battery, for example. Moreover, the power supply  160  may also be a unit that receives power from an external power supply via a power supply cord, etc., so as to supply the digital camera  1  with the power. 
         [0071]    The body mount  150  engages with the lens mount  250 . The body mount  150  supports the lens unit  200 . Moreover, the body mount  150  and the lens mount  250  can be electrically connected. The camera body  100  can transmit and receive at least one of the data and the control signal to and from the lens unit  200  via the body mount  150  and the lens mount  250 . 
         [0072]    The focal plane shutter device  190  (an example of a focal plane shutter device) is disposed in front of the CMOS image sensor  110  (on a subject side), and controls an exposure time of the CMOS image sensor  110 . In the focal plane shutter device  190 , there are a state in which light toward the CMOS image sensor  110  from an optical system L is shielded (close state), and a state in which the light toward the CMOS image sensor  110  from the optical system L is transmitted (open state). The focal plane shutter device  190  will be explained in detail later. 
         [0073]    The lens unit  200  may be attached to the camera body  100 , and forms an optical image of the subject. Specifically, the lens unit  200  includes: the optical system L; a drive part  215 ; the lens mount  250 ; the lens controller  240 ; and a lens barrel  260 . 
         [0074]    The optical system L forms the optical image of the subject, on a light-receiving face of the CMOS image sensor  110 . 
         [0075]    The lens controller  240  controls the entire lens unit  200  based on the control signal transmitted from the camera controller  140 . 
         [0076]    2: Configuration of the Focal Plane Shutter Device 
         [0077]    By using  FIGS. 6 to 11 , the focal plane shutter device  190  according to the first embodiment will be explained. 
         [0078]    The focal plane shutter device  190  includes: an opening-part opening/closing mechanism  191 ; a front-curtain drive mechanism  192 ; a rear-curtain drive mechanism  193 ; and the charge mechanism  194 . 
         [0079]    2.1: Opening-Part Opening/Closing Mechanism  191   
         [0080]    As shown in  FIG. 6 , the opening-part opening/closing mechanism  191  includes: a shutter base plate  11 ; a front curtain  21 ; a front-curtain drive arm  22 ; a front-curtain driven arm  23 ; a rear curtain  31 ; a rear-curtain drive arm  32 ; and a rear-curtain driven arm  33 . The shutter base plate  11  has two plates. Between the two plates, there is formed a gap that is sufficient for the front curtain  21  and the rear curtain  31  to run. The shutter base plate  11  has an opening part (also referred to as an aperture)  11   a  for guiding the subject light from the optical system L to the CMOS image sensor  110 . 
         [0081]    As shown in  FIGS. 6 and 10 , the front curtain  21  (an example of a front curtain) is disposed to be movable between a first front curtain position P 11  (an example of a first front curtain position) and a second front curtain position P 12  (an example of a second front curtain position). At the first front curtain position P 11 , the front curtain  21  covers the opening part  11   a . As shown in  FIG. 6 , at the second front curtain position P 12 , the front curtain  21  is retracted from the opening part  11   a . A state where the front curtain  21  covers the opening part  11   a  is also referred to as a photography standby state of the front curtain  21 . As shown in  FIG. 6 , a state where the front curtain  21  is retracted from the opening part  11   a  is also referred to as a running completion state of the front curtain  21 . By the front-curtain drive arm  22  and the front-curtain driven arm  23 , the front curtain  21  is supported to be movable between the first front curtain position P 11  and the second front curtain position P 12 . 
         [0082]    The front-curtain drive arm  22  is rotatably disposed relative to the shutter base plate  11 . As shown in  FIG. 10 , the front-curtain drive arm  22  includes a rotating shaft  22   a , a shaft  22   b , a shaft  22   c , and a shaft  22   d . The front curtain  21  includes a first front curtain blade  21   a , a second front curtain blade  21   b , and a third front curtain blade  21   c . The front-curtain drive arm  22  is rotatably supported around the rotating shaft  22   a  by the shutter base plate  11 . By the front-curtain drive arm  22 , the first front curtain blade  21   a  is rotatably supported around the shaft  22   b , the second front curtain blade  21   b  is rotatably supported around the shaft  22   c , and the third front curtain blade  21   c  is rotatably supported around the shaft  22   d , respectively. 
         [0083]    Moreover, the front-curtain driven arm  23  is rotatably disposed relative to the shutter base plate  11 . Specifically, the front-curtain driven arm  23  includes a rotating shaft  23   a , a shaft  23   b , a shaft  23   c , and a shaft  23   d . The front-curtain driven arm  23  is rotatably supported around the rotating shaft  23   a  by the shutter base plate  11 . By the front-curtain driven arm  23 , the first front curtain blade  21   a  is rotatably supported around the shaft  23   b , the second front curtain blade  21   b  is rotatably supported around the shaft  23   c , and the third front curtain blade  21   c  is rotatably supported around the shaft  23   d , respectively. 
         [0084]    In this way, the front curtain  21 , the front-curtain drive arm  22 , and the front-curtain driven arm  23  configure a so-called parallel link mechanism. Along with the rotation of the front-curtain drive arm  22  and the front-curtain driven arm  23 , the first front curtain blade  21   a , the second front curtain blade  21   b , and the third front curtain blade  21   c  sequentially move in a shorter side direction of the opening part  11   a  while keeping a parallel state with respect to a longer side of the opening part  11   a.    
         [0085]    As shown in  FIGS. 6 ,  8  and  10 , the rear curtain  31  (an example of a rear curtain) is disposed to be movable between a first rear curtain position P 21  (an example of a first rear curtain position) and a second rear curtain position P 22  (an example of a second rear curtain position). At the first rear curtain position P 21 , the rear curtain  31  covers the opening part  11   a . As shown in  FIG. 8 , at the second rear curtain position P 22 , the rear curtain  31  is retracted from the opening part  11   a . A state where the rear curtain  31  covers the opening part  11   a  is also referred to as a running completion state of the rear curtain  31 . As shown in  FIG. 10 , a state where the rear curtain  31  is retracted from the opening part  11   a  is also referred to as a photography standby state of the rear curtain  31 . The rear curtain  31  is supported to be movable between the first rear curtain position P 21  and the second rear curtain position P 22  by the rear-curtain drive arm  32  and the rear-curtain driven arm  33 . 
         [0086]    The rear-curtain drive arm  32  is rotatably disposed relative to the shutter base plate  11 . As shown in  FIG. 6 , the rear-curtain drive arm  32  includes a rotating shaft  32   a , a shaft  32   b , a shaft  32   c , and a shaft  32   d . The rear curtain  31  includes a first rear curtain blade  31   a , a second rear curtain blade  31   b , and a third rear curtain blade  31   c . The rear-curtain drive arm  32  is rotatably supported around the rotating shaft  32   a  by the shutter base plate  11 . By the rear-curtain drive arm  32 , the first rear curtain blade  31   a  is rotatably supported around the shaft  32   b , the second rear curtain blade  31   b  is rotatably supported around the shaft  32   c , and the third rear curtain blade  31   c  is rotatably supported around the shaft  32   d , respectively. 
         [0087]    Moreover, the rear-curtain driven arm  33  is rotatably disposed relative to the shutter base plate  11 . Specifically, the rear-curtain driven arm  33  includes a rotating shaft  33   a , a shaft  33   b , a shaft  33   c , and a shaft  33   d . The rear-curtain driven arm  33  is rotatably supported around the rotating shaft  33   a  by the shutter base plate  11 . By the rear-curtain driven arm  33 , the first rear curtain blade  31   a  is rotatably supported around the shaft  33   b , the second rear curtain blade  31   b  is rotatably supported around the shaft  33   c , and the third rear curtain blade  31   c  is rotatably supported around the shaft  33   d , respectively. 
         [0088]    In this way, the rear curtain  31 , the rear-curtain drive arm  32 , and the rear-curtain driven arm  33  configure a so-called parallel link mechanism. Along with the rotation of the rear-curtain drive arm  32  and the rear-curtain driven arm  33 , the first rear curtain blade  31   a , the second rear curtain blade  31   b , and the third rear curtain blade  31   c  sequentially move in the shorter side direction of the opening part  11   a  while keeping a parallel state with respect to the longer side of the opening part  11   a.    
         [0089]    2.2: Front-Curtain Drive Mechanism  192   
         [0090]    Subsequently, the front-curtain drive mechanism  192  for driving the front curtain  21  will be explained. 
         [0091]    As shown in  FIGS. 6 and 7 , the front-curtain drive mechanism  192  includes: a front-curtain drive lever  28 ; a front-curtain set spring  27 ; a charge lever  29 ; a front-curtain set lever  24 ; a front-curtain running spring  25 ; and a front-curtain electromagnet  26 . 
         [0092]    The front-curtain drive lever  28  (an example of a front curtain drive member) couples the front curtain  21  to the shutter base plate  11  to be movable between the first front curtain position P 11  and the second front curtain position P 12 . As shown in  FIG. 16A , the front-curtain drive lever  28  includes a drive coupling pin  28   a  and a claw  28   c . As shown in  FIG. 6 , the front-curtain drive arm  22  includes a coupling hole  22   e . The drive coupling pin  28   a  is inserted into the coupling hole  22   e . Similarly to the front-curtain drive arm  22 , the front-curtain drive lever  28  is rotatably supported by the rotating shaft  22   a  around the rotating shaft  22   a . The front-curtain drive arm  22  and the front-curtain drive lever  28  can rotate integrally around the rotating shaft  22   a.    
         [0093]    The front-curtain set spring  27  (one example of a third urging member) biases the front-curtain drive lever  28  in a direction where the front curtain  21  covers the opening part  11   a . Specifically, as shown in  FIG. 7 , the front-curtain set spring  27  imparts an elastic force F 12  to the front curtain  21  so that the front curtain  21  moves from the first front curtain position P 11  to the second front curtain position P 12  in the running direction R (see  FIG. 6 ). The elastic force F 12  of the front-curtain set spring  27  is smaller than the elastic force F 11  of the front-curtain running spring  25 . The front-curtain set spring  27  is hooked onto the front-curtain driven arm  23 , and thus, the elastic force F 12  of the front-curtain set spring  27  acts upon the front-curtain drive arm  22 . In the first embodiment, the front-curtain set spring  27  applies a clockwise rotation force to the front-curtain drive lever  28 . 
         [0094]    As shown in  FIG. 16A , the front-curtain drive lever  28  includes a front-curtain-drive-lever contacting portion  28   b . As shown in  FIG. 16B , the front-curtain set lever  24  includes a front-curtain-set-lever contacting portion  24   a . As shown in  FIG. 7 , the front-curtain-drive-lever contacting portion  28   b  abuts the front-curtain-set-lever contacting portion  24   a . Similarly to the front-curtain drive lever  28 , the front-curtain set lever  24  is rotatably supported by the rotating shaft  22   a  around the rotating shaft  22   a . When the front-curtain set lever  24  rotates counterclockwise, the front-curtain-drive-lever contacting portion  28   b  is pushed by the front-curtain-set-lever contacting portion  24   a , which in turn rotates the front-curtain drive lever  28  counterclockwise. When the front curtain  21  moves from the first front curtain position P 11  to the second front curtain position P 12 , the front-curtain set lever  24  transmits the elastic force F 11  of the front-curtain running spring  25  to the front curtain  21  via the front-curtain drive lever  28 . That is, at the time of imparting the front-curtain running spring  25  with the first biasing force F 13 , the charge mechanism  194  imparts the front-curtain running spring  25  with the first biasing force F 13  via the front-curtain set lever  24 . 
         [0095]    Moreover, by the elastic force F 12  of the front-curtain set spring  27 , the front-curtain drive lever  28  is imparted with clockwise rotation force. This brings the front-curtain-set-lever contacting portion  24   a  and the front-curtain-drive-lever contacting portion  28   b  to contact each other. The counterclockwise rotation of the front-curtain set lever  24  is restricted by a stopper (not shown) at a position shown in  FIG. 6 . Thus, when the front-curtain set lever  24  and the front-curtain drive lever  28  integrally rotate counterclockwise, the front-curtain set lever  24  and the front-curtain drive lever  28  stop at the position shown in  FIG. 6 . By the elastic force F 11  of the front-curtain running spring  25 , the front-curtain set lever  24  and the front-curtain drive lever  28  are kept at a position shown in  FIG. 6 . That is, the elastic force F 11  of the front-curtain running spring  25  can be transmitted to the front curtain  21  by the front-curtain drive lever  28  via the front-curtain set lever  24 . 
         [0096]    On the other hand, even when the front-curtain set lever  24  rotates clockwise, the front-curtain-set-lever contacting portion  24   a  does not contact the front-curtain-drive-lever contacting portion  28   b , and thus, when the front-curtain set lever  24  rotates clockwise, the front-curtain set lever  24  rotates independently of the front-curtain drive lever  28 . Therefore, when the charge mechanism  194  imparts the front-curtain running spring  25  with the first biasing force F 13 , the front-curtain set lever  24  imparts the front-curtain running spring  25  with the first biasing force F 13  without intervention of the front-curtain drive lever  28 . 
         [0097]    As shown in  FIG. 7 , the front-curtain running spring  25  (one example of a first urging member) always imparts the front-curtain set lever  24  with the strong counterclockwise elastic force F 11 . Specifically, the front-curtain running spring  25  imparts the front curtain  21  with the elastic force F 11  so that the front curtain  21  moves from the first front curtain position P 11  to the second front curtain position P 12 . By the elastic force F 11  of the front-curtain running spring  25 , the counterclockwise rotation force is acted upon the front-curtain set lever  24 . The front-curtain set lever  24  is arranged to transmit the elastic force F 11  of the front-curtain running spring  25  to the front-curtain drive lever  28 . Therefore, in a state where the front-curtain-set-lever contacting portion  24   a  contacts the front-curtain-drive-lever contacting portion  28   b , as shown in  FIG. 7 , for example, the elastic force F 11  of the front-curtain running spring  25  is transmitted to the front-curtain drive lever  28 . That is, when the front curtain  21  is disposed at the first front curtain position P 11 , the front-curtain running spring  25  imparts the front-curtain drive lever  28  with the strong counterclockwise elastic force F 11 . The elastic force F 11  of the front-curtain running spring  25  also is transmitted to the front-curtain drive arm  22  and the front curtain  21  via the front-curtain drive lever  28 . Therefore, the front-curtain running spring  25  biases the front curtain  21  in a direction where the front curtain  21  is retracted from the opening part  11   a.    
         [0098]    The counterclockwise elastic force F 11  applied by the front-curtain running spring  25  to the front-curtain drive lever  28  is larger than the clockwise elastic force F 12  applied by the front-curtain set spring  27  to the front-curtain drive lever  28 . Therefore, even when the elastic force F 12  of the front-curtain set spring  27  is acted upon the front curtain  21 , the front curtain  21  can be run toward the direction where the front curtain  21  is retracted from the opening part  11   a  by the elastic force F 11  of the front-curtain running spring  25 . The force achieved when the front curtain  21  runs is equivalent to a total force of the elastic force F 11  of the front-curtain running spring  25  and the elastic force F 12  of the front-curtain set spring  27 . 
         [0099]    Further, as shown in  FIG. 7 , to the end of the front-curtain set lever  24 , a front-curtain attracting piece  24   b  is fixed. The front-curtain attracting piece  24   b  is arranged to be attracted to the front-curtain electromagnet  26 . When the front-curtain electromagnet  26  is supplied with power, the front-curtain electromagnet  26  generates a magnetic force. Thus, if the front-curtain electromagnet  26  is supplied with power when the front-curtain attracting piece  24   b  is in contact with the front-curtain electromagnet  26 , then the front-curtain attracting piece  24   b  is attracted to the front-curtain electromagnet  26  by the magnetic force of the front-curtain electromagnet  26 . The attracting force between the front-curtain attracting piece  24   b  and the front-curtain electromagnet  26  has a sufficient power to counteract the elastic force F 11  of the front-curtain running spring  25 . Therefore, when the front-curtain attracting piece  24   b  is attracted to the front-curtain electromagnet  26 , the position of the front-curtain set lever  24  is kept at a charge position shown in  FIG. 9  even when the elastic force F 11  of the front-curtain running spring  25  acts upon the front-curtain set lever  24 . 
         [0100]    As shown in  FIGS. 7 and 16B , the front-curtain set lever  24  rotatably supports a front-curtain set lever roller  24   c . As shown in  FIGS. 7 and 18A , the charge lever  29  includes a front-curtain set cam  29   b  (an example of a front-curtain cam part). As shown in  FIG. 7 , the front-curtain set lever roller  24   c  is arranged to be contactable with the front-curtain set cam  29   b.    
         [0101]    2.3: Rear-Curtain Drive Mechanism  193   
         [0102]    Subsequently, the rear-curtain drive mechanism  193  for driving the rear curtain  31  will be explained. 
         [0103]    As shown in  FIGS. 6 and 7 , the rear-curtain drive mechanism  193  includes a rear-curtain drive lever  38 , a rear-curtain set lever  34 , and a rear-curtain running spring  35 . 
         [0104]    The rear-curtain drive lever  38  couples the rear curtain  31  to the shutter base plate  11  to be movable between the first rear curtain position P 21  and the second rear curtain position P 22 . 
         [0105]    As shown in  FIGS. 7 and 17 , the rear-curtain set lever  34  includes a rear-curtain set lever coupling pin  34   a . The rear-curtain drive arm  32  includes a rear-curtain drive arm coupling hole  32   e . The rear-curtain set lever coupling pin  34   a  is inserted into the rear-curtain drive arm coupling hole  32   e.    
         [0106]    Moreover, similarly to the rear-curtain drive arm  32 , the rear-curtain set lever  34  is rotatably supported by the rotating shaft  32   a  around the rotating shaft  32   a . The rear-curtain drive arm  32  and the rear-curtain set lever  34  can integrally rotate around the rotating shaft  32   a.    
         [0107]    The rear-curtain running spring  35  (one example of a second urging member) biases the rear curtain  31  in a direction where the rear curtain  31  covers the opening part  11   a . Specifically, as shown in  FIG. 7 , the rear-curtain running spring  35  imparts the rear curtain  31  with an elastic force F 21  via the rear-curtain drive arm  32  so that the rear curtain  31  moves from the second rear curtain position P 22  to the first rear curtain position P 21 . The rear-curtain running spring  35  imparts the rear-curtain set lever  34  with the strong counterclockwise elastic force F 21 . The rear-curtain set lever  34  is arranged to transmit the elastic force F 21  of the rear-curtain running spring  35  to the rear-curtain drive lever  38 . 
         [0108]    Further, as shown in  FIG. 7 , to the end of the rear-curtain set lever  34 , a rear-curtain attracting piece  34   b  is fixed. The rear-curtain attracting piece  34   b  is arranged to be attracted to the rear-curtain electromagnet  36 . When the rear-curtain electromagnet  36  is supplied with power, the rear-curtain electromagnet  36  generates a magnetic force. Thus, if the rear-curtain electromagnet  36  is supplied with the power when the rear-curtain attracting piece  34   b  is in contact with the rear-curtain electromagnet  36 , then the rear-curtain attracting piece  34   b  is attracted to the rear-curtain electromagnet  36  by the magnetic force of the rear-curtain electromagnet  36 . The attracting force between the rear-curtain attracting piece  34   b  and the rear-curtain electromagnet  36  has a sufficient power to counteract the elastic force F 21  of the rear-curtain running spring  35 . Therefore, when the rear-curtain attracting piece  34   b  is attracted to the rear-curtain electromagnet  36 , the position of the rear-curtain set lever  34  is kept at a charge position shown in  FIGS. 8 and 9  even when the elastic force F 21  of the rear-curtain running spring  35  acts upon the rear-curtain set lever  34 . 
         [0109]    As shown in  FIGS. 7 and 17 , the rear-curtain set lever  34  rotatably supports a rear-curtain set lever roller  34   c . As shown in  FIGS. 7 and 18A , the charge lever  29  includes a rear-curtain set cam  29   c . As shown in  FIG. 7 , the rear-curtain set lever roller  34   c  is arranged to be contactable with the rear-curtain set cam  29   c.    
         [0110]    2.4: Charge Mechanism  194   
         [0111]    Next, the charge mechanism  194  will be explained. 
         [0112]    The charge mechanism  194  (an example of a charge mechanism) is configured to impart the front-curtain running spring  25  and the rear-curtain running spring  35  with a first biasing force F 13  resisting the elastic force F 11  of the front-curtain running spring  25  and a second biasing force F 23  resisting the elastic force F 21  of the rear-curtain running spring  35 . Specifically, as shown in  FIG. 7 , the charge mechanism  194  includes: a charge lever  29 ; a partly tooth-missing gear part  29   e ; a charge-lever return spring  30 ; a partly tooth-missing gear  40 ; a planet gear  41 ; a planet carrier  42 ; a sun gear  43 ; a worm gear  44 ; and a charge-lever detection switch  48 . 
         [0113]    A motor  46  (an example of an actuator) generates the first biasing force F 13  imparted to the front-curtain running spring  25  and the second biasing force F 23  imparted to the rear-curtain running spring  35 . Specifically, the motor  46  is configured to drive the charge lever  29  to a front-curtain charge start position (an example of a first charge start position) at which imparting the front-curtain running spring  25  with the first biasing force F 13  is started and a rear-curtain charge start position (an example of a second charge start position) at which imparting the rear-curtain running spring  35  with the second biasing force F 23  is started. Further, the motor  46  is configured to drive the charge lever  29  to a front-curtain charge completion position (an example of a first charge completion position) at which imparting the front-curtain running spring  25  with the first biasing force F 13  is completed and a rear-curtain charge completion position (an example of a second charge completion position) at which imparting the rear-curtain running spring  35  with the second biasing force F 23  is completed. 
         [0114]    The rear-curtain charge completion position (a position shown in  FIGS. 12 and 13 ) is disposed between the rear-curtain charge start position (a position shown in  FIGS. 6 and 7 ) and the front-curtain charge completion position (a position shown in  FIGS. 8 and 9 ). The motor  46  is configured to drive the charge lever  29  to the front-curtain charge start position (a position disposed between a position shown in  FIG. 7  and a position shown in  FIG. 13 ) and the a front-curtain running standby position (a position disposed between a position shown in  FIG. 10  and a position shown in  FIG. 11 ) relative to the front-curtain charge completion position. Further, the motor  46  is configured to drive the charge lever  29  to a restriction position of the charge lever  29 . In this embodiment, the restriction position of the charge lever  29  is the same position as the front-curtain charge completion position (a position shown in  FIGS. 8 and 9 ). An original position where the charge lever  29  is in contact with the stopper  11   b  is the same position as the rear-curtain charge completion position. 
         [0115]    The charge lever  29  (an example of a charge member) is arranged to transmit the first biasing force F 13  to the front-curtain running spring  25  via the front-curtain set lever  24 , and is arranged to transmit the second biasing force F 23  to the rear-curtain running spring  35  via the rear-curtain set lever  34 . Specifically, as shown in  FIGS. 18A and 18B , the charge lever  29  is arranged to drive the front-curtain drive lever  28 , the front-curtain set lever  24 , and the rear-curtain set lever  34 , and includes: a rotating shaft  29   a ; the front-curtain set cam  29   b ; the rear-curtain set cam  29   c ; a front-curtain holding part  29   d ; and a reverse preventive part  29   da . The charge lever  29  is rotatably disposed relative to the shutter base plate  11  around the rotating shaft  29   a.    
         [0116]    As shown in  FIG. 7 , the front-curtain set cam  29   b  (an example of a front-curtain cam part) and a front-curtain set lever  24  are arranged to be contactable with each other, and drive to rotate the front-curtain set lever  24  clockwise. More particularly, the front-curtain set cam  29   b  is arranged to be contactable with the front-curtain set lever roller  24   c  of the front-curtain set lever  24 . If the charge lever  29  rotates counterclockwise when the front-curtain set cam  29   b  abuts the front-curtain set lever roller  24   c , then the front-curtain set lever  24  rotates clockwise while resisting the elastic force F 11  of the front-curtain running spring  25 , resulting in the front-curtain attracting piece  24   b  contacting the front-curtain electromagnet  26 . In this way, the elastic force required for running the front curtain  21  can be charged to the front-curtain running spring  25  by the charge lever  29 . 
         [0117]    As shown in  FIG. 7 , when the charge lever  29  is at the rear-curtain charge start position, a gap is secured between the front-curtain set cam  29   b  and the front-curtain set lever  24 . As shown in  FIG. 9 , the charge lever  29  is at the front-curtain charge completion position, the front-curtain set lever  24  is in contact with the outer peripheral face  29   f , and is held at the position shown in  FIG. 9  by the front-curtain set cam  29   b.    
         [0118]    Moreover, the rear-curtain set cam  29   c  is arranged to be contactable with the rear-curtain set lever  34 , and drives to rotate the rear-curtain set lever  34  clockwise. The rear-curtain set cam  29   c  is arranged to be contactable with the rear-curtain set lever roller  34   c  of the rear-curtain set lever  34 . If the charge lever  29  rotates counterclockwise in a state where the rear-curtain set cam  29   c  abuts the rear-curtain set lever roller  34   c , then the rear-curtain set lever  34  rotates clockwise while resisting the elastic force F 21  of the rear-curtain running spring  35 , resulting in the rear-curtain attracting piece  34   b  contacting the rear-curtain electromagnet  36 . In this way, the biasing force required for running the rear curtain  31  can be charged to the rear-curtain running spring  35  by the charge lever  29 . As shown in  FIG. 13 , when the charge lever  29  is positioned at the rear-curtain charge completion position, the rear-curtain set lever  34  is in contact with an outer peripheral face  29   g  of the rear-curtain set cam  29   c , and is held at the position shown in  FIG. 13  by the rear-curtain  29   c.    
         [0119]    As shown in  FIG. 9 , a state where the front-curtain attracting piece  24   b  is at the position to be attracted to the front-curtain electromagnet  26  is also referred to as “charge completion state of the front curtain  21 ”. Moreover, a state where the rear-curtain attracting piece  34   b  is at the position to be attracted to the rear-curtain electromagnet  36  is also referred to as “charge completion state of the rear curtain  31 ”. Bringing the front curtain  21  into the charge completion state is also referred to as “charging the front curtain  21 ”. Further, bringing the rear curtain  31  into the charge completion state is also referred to as “charging the rear curtain  31 ”. 
         [0120]    The charge lever  29  is capable of holding the front curtain  21  via the front-curtain drive lever  28  at the second front curtain position P 12 . When the charge lever  29  is at the front-curtain charge completion position, the charge lever  29  holds the front curtain  21  via the front-curtain drive lever  28  at the second front curtain position P 12 . Specifically, the front-curtain holding part  29   d  (an example of a front-curtain holding part) holds the front curtain  21  via the front-curtain drive lever  28  at the second front curtain position P 12 . The front-curtain drive lever  28  includes a claw  28   c  (an example of a claw) arranged to be contactable with the front-curtain holding part  29   d . While the charge lever  29  rotates from the front-curtain charge start position to the front-curtain charge completion position, the front-curtain holding part  29   d  enters in a region  28   d  (an example of a substantially arc-shaped trajectory) where the claw  28   c  moves when the front curtain  21  moves from the second front curtain position P 12  to the first front curtain position P 11  (see  FIGS. 19A and 19B ). Therefore, during a time between the charge start and the charge completion of the front curtain  21 , the front-curtain holding part  29   d  is permitted to be in contact with the claw  28   c , and the clockwise rotation of the front-curtain drive lever  28  is restricted by the charge lever  29  (for example, see  FIGS. 13 and 19A ). As a result, the state where the front curtain  21  is retracted from the opening part  11   a  is maintained by the charge lever  29 . That is, while the first biasing force F 13  is imparted to the front-curtain running spring  25 , the charge mechanism  194  can hold the front curtain  21  at the second front curtain position P 12 . 
         [0121]    On the other hand, when the charge lever  29  is at the release position, the charge lever  29  cancels the holding of the front curtain  21  at the second front curtain position P 12 . Specifically, as shown in  FIGS. 10 and 11 , when the charge lever  29  is at the release position, the front-curtain holding part  29   d  is retracted from the moving region  28   d  of the claw  28   c . In this state, the front-curtain holding part  29   d  does not abut the claw  28   c , and thus, the clockwise rotation of the front-curtain drive lever  28  is not restricted by the front-curtain holding part  29   d.    
         [0122]    Moreover, when the charge lever  29  is at the restriction position (the position shown in  FIGS. 8 and 9 ), the front-curtain drive lever  28  restricts returning of the charge lever  29  to the original position (the position shown in  FIGS. 6 and 7 ). Specifically, the front-curtain holding part  29   d  includes the reverse preventive part  29   da . The reverse preventive part  29   da  has a step. In a state where the distal end of the claw  28   c  is hooked onto the reverse preventive part  29   da , the clockwise rotation of the charge lever  29  is restricted by the claw  28   c . When the charge lever  29  is at the restriction position, the claw  28   c  comes hooked onto the reverse preventive part  29   da.    
         [0123]    The partly tooth-missing gear part  29   e  is rotatably arranged, together with the charge lever  29 . The charge lever  29  and the partly tooth-missing gear part  29   e  are rotatably supported by the rotating shaft  29   a . The charge lever  29  is biased clockwise by the charge-lever return spring  30 . The charge-lever return spring  30  (an example of a return elastic member) imparts the charge lever  29  with the elastic force F 22  so that the charge lever  29  returns to the original position obtained before imparting the first biasing force F 13  and the second biasing force F 23  is started. The stopper  11   b  provided on the shutter base plate  11  abuts the charge lever  29  so as to restrict the rotation of the charge lever  29  by the charge-lever return spring  30 . As shown in  FIGS. 6 and 7 , in a state where no force other than the biasing force of the charge-lever return spring  30  acts upon the charge lever  29 , the charge lever  29  is held at the original position where the charge lever  29  abuts the stopper  11   b.    
         [0124]    The partly tooth-missing gear part  29   e  can be meshed with the partly tooth-missing gear  40 . The partly tooth-missing gear  40  is rotatably supported by the shutter base plate  11 . The partly tooth-missing gear  40  is configured by a stepped gear, and includes a gear part  40   a  including teeth extending over the length. The gear part  40   a  can be meshed with the planet gear  41 . 
         [0125]    The planet gear  41  is rotatably supported by the planet carrier  42 . The planet carrier  42  is rotatably supported by the shutter base plate  11  around the same shaft  43   b  as the sun gear  43 . The sun gear  43  is meshed with the planet gear  41 . At this time, when an appropriate rotation load is applied to the sun gear  43 , the planet carrier  42  and the planet gear  41  rotate around the shaft  43   b  according to a rotation direction of the sun gear  43 . When the planet gear  41  rotates around the shaft  43   b , a gear with which the planet gear  41  is meshed can be switched to the partly tooth-missing gear  40  or a coupling gear  47 . 
         [0126]    The planet carrier  42  includes a first rotation restriction part  42   a  and a second rotation restriction part  42   b . The first rotation restriction part  42   a  and the second rotation restriction part  42   b  abut a first stopper  11   c  and a second stopper  11   d  provided on the shutter base plate  11 , respectively. Thereby, the rotation of the planet carrier  42  relative to the shutter base plate  11  is restricted within a predetermined range. 
         [0127]    The sun gear  43  is configured by a stepped gear, and includes a worm wheel  43   a  meshed with the worm gear  44 . The worm gear  44  is fixed to the rotating shaft  46   a  of the motor  46 . The worm gear  44  includes an encoder vane  44   a . As a result of the encoder vane  44   a  blocking light of a photo interrupter  45 , it becomes possible to measure a rotation amount (drive amount) or a speed of the motor  46 . 
         [0128]    The charge-lever detection switch  48  is fixed to the shutter base plate  11 , and detects a rotation position of the charge lever  29 . More particularly, the charge-lever detection switch  48  detects whether or not the charge lever  29  is in proximity. 
         [0129]    3: Operation of Slit Exposure Photography 
         [0130]    Subsequently, an operation of slit exposure photography will be explained. A flowchart shown in  FIG. 20  is a flowchart of the slit exposure photography. 
         [0131]    3.1: Running Completion State 
         [0132]      FIG. 6  shows a photography end state of the focal plane shutter device  190 , i.e., a state where running of the front curtain  21  and the rear curtain  31  is completed.  FIG. 7  is an enlarged view of main parts of  FIG. 6 . 
         [0133]    In the running completion state shown in  FIG. 6 , the front curtain  21  is retracted the upper side of the opening part  11   a  by the elastic force F 11  of the front-curtain running spring  25 . When the front curtain  21  is disposed at the second front curtain position P 12 , the front-curtain set lever  24  abuts the front-curtain drive lever  28  so that the front-curtain-set-lever contacting portion  24   a  abuts the front-curtain-drive-lever contacting portion  28   b  by the elastic force F 12  of the front-curtain set spring  27  and the elastic force F 11  of the front-curtain running spring  25 . Moreover, the rear curtain  31  keeps covering the opening part  11   a  by the elastic force F 21  of the rear-curtain running spring  35 . The rear-curtain set lever  34  holds the counterclockwise rotation by the biasing force of the rear-curtain running spring  35 . 
         [0134]    3.2: Charge Operation 
         [0135]      FIG. 8  is a view showing a state when charging of the front-curtain set lever  24  and the front-curtain drive lever  28  is completed by the charge lever  29 . In the running completion state shown in  FIG. 6 , the motor  46  is energized, and the sun gear  43  rotates clockwise by the motor  46  (step S 1 ). As a result, the planet carrier  42  rotates clockwise by a rotation load, resulting in the second rotation restriction part  42   b  and the second stopper  11   d  contacting with each other. 
         [0136]    Thereafter, the planet gear  41  rotates counterclockwise, which in turns rotates the partly tooth-missing gear  40 . The partly tooth-missing part  40   b  provided to the partly tooth-missing gear  40  is meshed with the partly tooth-missing gear part  29   e  of the charge lever  29 , and the partly tooth-missing gear part  29   e  is rotated counterclockwise. The charge lever  29  provided integrally with the partly tooth-missing gear part  29   e  rotates counterclockwise resisting the elastic force F 22  of the charge-lever return spring  30 . 
         [0137]    At this time, at the same time that the motor  46  is energized, the charge-lever detection switch  48  starts detecting whether or not the charge lever  29  is in proximity (step S 2 ). When the charge lever  29  is detected by the charge-lever detection switch  48  as a result of advancement of the rotation of the charge lever  29 , detection of the drive amount of the motor  46  is started by using the photo interrupter  45  and the encoder vane  44   a  (step S 3 ). 
         [0138]    If the charge lever  29  rotates counterclockwise in states shown in  FIGS. 6 and 7 , then the rear-curtain set lever roller  34   c  is pressed by the rear-curtain set cam  29   c , and the rear-curtain set lever  34  rotates clockwise. When the rear-curtain set lever  34  rotates clockwise, the rear curtain  31  moves from the first rear curtain position P 21  toward the second rear curtain position P 22 , and the rear curtain  31  is retracted from the opening part  11   a . When the rear-curtain set lever roller  34   c  reaches an outer peripheral face  29   g  of the rear-curtain set cam  29   c , the rear curtain  31  reaches the second rear curtain position P 22 , and the rear-curtain attracting piece  34   b  is pushed against the rear-curtain electromagnet  36  (see  FIGS. 8 and 9 ). The position of the rear-curtain set lever  34  is held by the outer peripheral face  29   g  of the rear-curtain set cam  29   c , and thus, the elastic force F 21  of the rear-curtain running spring  35  does not act, as the rotation force, upon the charge lever  29 . 
         [0139]    Similarly, when the charge lever  29  rotates counterclockwise, the front-curtain set lever roller  24   c  is pressed by the front-curtain set cam  29   b , and the front-curtain set lever  24  rotates clockwise. When the front-curtain set lever roller  24   c  reaches an outer peripheral face  29   f  of the front-curtain set cam  29   b , the front-curtain attracting piece  24   b  is pushed against the front-curtain electromagnet  26 . The position of the front-curtain set lever  24  is held by the outer peripheral face  29   f  of the front-curtain set cam  29   b , and thus, the elastic force F 11  of the front-curtain running spring  25  does not act, as the rotation force, upon the charge lever  29 . 
         [0140]    On the other hand, when the front-curtain set lever  24  rotates clockwise, and also the front-curtain drive lever  28  attempts to rotate clockwise, together with the front-curtain set lever  24 , by the elastic force F 12  of the front-curtain set spring  27 . 
         [0141]    However, when the charge lever  29  rotates counterclockwise, the front-curtain holding part  29   d  enters into a rotation trail (an example of a moving region) of the claw  28   c  so that the claw  28   c  abuts the front-curtain holding part  29   d . As a result, the clockwise rotation of the front-curtain drive lever  28  is restricted by the front-curtain holding part  29   d . Therefore, when the charge lever  29  rotates counterclockwise, only the front-curtain set lever  24  rotates clockwise and the front-curtain drive lever  28  does not rotate clockwise. The front-curtain drive lever  28  does not rotate, and thus, during the above-described charge operation, the front curtain  21  is kept being held at the second front curtain position P 12  and the front curtain  21  is kept being retracted from the opening part  11   a.    
         [0142]    When the drive amount of the motor  46  reaches a predetermined value, the drive of the motor  46  is stopped (step S 4 ). At this time, the charge lever  29  stops at the position shown in  FIGS. 8 and 9 . The charge lever  29  stops at the position shown in  FIGS. 8 and 9 , and thus, even after the charge operation, the claw  28   c  is kept contacting the front-curtain holding part  29   d  and the front curtain  21  is kept being retracted from the opening part  11   a.    
         [0143]    In this way, the focal plane shutter device  190  can automatically maintain the state where the opening part  11   a  is opened even during the charge operation and after the charge operation. That is, the focal plane shutter device  190  has a so-called normally open function. 
         [0144]    At this time, as shown in  FIG. 22B , a timing at which the charge mechanism  194  completes charging the front-curtain running spring  25  is different from a timing at which the charge mechanism  194  completes charging the rear-curtain running spring  35 . More particularly, a timing at which the charge mechanism  194  completes charging the rear-curtain running spring  35  is earlier than a timing at which the charge mechanism  194  completes charging the front-curtain running spring  25 . The charge completion timing is determined by the position and the shape of the front-curtain set cam  29   b  and the rear-curtain set cam  29   c.    
         [0145]    At this time, the timing at which the charge mechanism  194  completes charging the front-curtain running spring  25  means a timing at which the charge mechanism  194  completes imparting the front-curtain set lever  24  with the first biasing force F 13  resisting the elastic force F 11  of the front-curtain running spring  25 . Therefore, a timing at which the front-curtain set lever roller  24   c  is placed over the outer peripheral face  29   f  of the front-curtain set cam  29   b  is equivalent to the timing at which the charge mechanism  194  completes charging the front-curtain running spring  25 . 
         [0146]    Likewise, the timing at which the charge mechanism  194  completes charging the rear-curtain running spring  35  means a timing at which the charge mechanism  194  completes imparting the rear-curtain set lever  34  with the second biasing force F 23  resisting the elastic force F 21  of the rear-curtain running spring  35 . Therefore, a timing at which the rear-curtain set lever roller  34   c  is placed over the outer peripheral face  29   g  of the rear-curtain set cam  29   c  is equivalent to the timing at which the charge mechanism  194  completes charging the rear-curtain running spring  35 . 
         [0147]    Moreover, a timing at which the charge mechanism  194  starts charging the front-curtain running spring  25  is different from a timing at which the charge mechanism  194  starts charging the rear-curtain running spring  35 . Specifically, a timing at which the charge mechanism  194  starts imparting the rear-curtain running spring  35  with the second biasing force F 23  is earlier than a timing at which the charge mechanism  194  starts imparting the front-curtain running spring  25  with the first biasing force F 13 . The charge start timing is determined by the position and the shape of the front-curtain set cam  29   b  and the rear-curtain set cam  29   c.    
         [0148]    At this time, the timing at which the charge mechanism  194  starts charging the front-curtain running spring  25  means a timing at which the charge mechanism  194  starts imparting the front-curtain set lever  24  with the first biasing force F 13  resisting the elastic force F 11  of the front-curtain running spring  25 . Therefore, a timing at which the front-curtain set lever roller  24   c  abuts the front-curtain set cam  29   b  is equivalent to the timing at which the charge mechanism  194  starts charging the front-curtain running spring  25 . 
         [0149]    Likewise, the timing at which the charge mechanism  194  starts charging the rear-curtain running spring  35  means a timing at which the charge mechanism  194  starts imparting the rear-curtain set lever  34  with the second biasing force F 23  resisting the elastic force F 21  of the rear-curtain running spring  35 . Therefore, a timing at which the rear-curtain set lever roller  34   c  abuts the rear-curtain set cam  29   c  is equivalent to the timing at which the charge mechanism  194  completes charging the rear-curtain running spring  35 . 
         [0150]    Further, in a state where the front-curtain set lever roller  24   c  is supported by the outer peripheral face  29   f  of the front-curtain set cam  29   b , the front-curtain attracting piece  24   b  is pushed against the front-curtain electromagnet  26 . Likewise, in a state where the rear-curtain set lever roller  34   c  is supported by the outer peripheral face  29   g  of the rear-curtain set cam  29   c , the rear-curtain attracting piece  34   b  is pushed against the rear-curtain electromagnet  36 . Therefore, contact between the rear-curtain attracting piece  34   b  and the rear-curtain electromagnet  36  is performed before contact between the front-curtain attracting piece  24   b  and the front-curtain electromagnet  26 . In other words, the front-curtain set cam  29   b  and the rear-curtain set cam  29   c  are shaped so that the contact between the rear-curtain attracting piece  34   b  and the rear-curtain electromagnet  36  is performed before the contact between the front-curtain attracting piece  24   b  and the front-curtain electromagnet  26 . 
         [0151]    Thus, in the first embodiment, the timing at which the charge mechanism  194  completes charging the rear-curtain running spring  35  is earlier than the timing at which the charge mechanism  194  completes charging the front-curtain running spring  25  (see  FIG. 22B , for example). Thereby, as compared to a reference example shown in  FIG. 22A , for example, a force required for charging (i.e., the load of the motor  46 ) can be decreased. In the reference example shown in  FIG. 22A , the charge completion timings are the same in the front curtain and the rear curtain. 
         [0152]    A state shown in  FIG. 8  guides light from a subject to a CMOS image sensor  110 . This state is effective particularly when a user wishes to maintain a state where the CMOS image sensor  110  is exposed. For example, this state is particularly effective when by using a live view function by the camera body  100 , the subject is observed, framing is performed, or moving picture photography is performed. 
         [0153]    It is noted that the camera controller  140  comprehends the rotation position of the charge lever  29  based on the rotation amount of the motor  46 . More particularly, the camera controller  140  can comprehend the rotation amount of the motor  46  by the encoder vane  44   a  and the photo interrupter  45 , and further, can comprehend the original position of the charge lever  29  based on the detected result of the charge-lever detection switch  48 . Therefore, the camera controller  140  can comprehend the rotation position (rear curtain charge completion position, restriction position, and release position) of the charge lever  29  where the original position is used as a reference. 
         [0154]    3.3: Reverse of Motor 
         [0155]    When the motor  46  is reversed in a state shown in  FIGS. 8 and 9 , the sun gear  43  rotates counterclockwise, and along therewith, the planet carrier  42  rotates counterclockwise around the shaft  43   b . As a result, the first rotation restriction part  42   a  of the planet carrier  42  abuts the first stopper  11   c . The planet gear  41  is meshed not with the partly tooth-missing gear  40  but with the coupling gear  47  at the position where the first rotation restriction part  42   a  abuts the first stopper  11   c , and thus, the rotation of the sun gear  43  is transmitted to the coupling gear  47  via the planet gear  41 . As a result of the coupling gear  47  being coupled to another member, another drive member can also be driven by taking advantage of the rotation of the coupling gear  47 . Examples of the other drive member include a flash pop-up. 
         [0156]    When the planet gear  41  is meshed with the partly tooth-missing gear  40 , because of a self lock function of the worm gear  44 , the sun gear  43  and the planet gear  41  do not rotate in a state where the worm gear  44  does not rotate, and the partly tooth-missing gear  40  meshed with the planet gear  41  does not rotate, either. Therefore, if the partly tooth-missing gear  40  is meshed with the partly tooth-missing gear part  29   e , then the charge lever  29  does not rotate. 
         [0157]    However, when the planet gear  41  rotates counterclockwise around the shaft  43   b , the meshing between the planet gear  41  and the partly tooth-missing gear  40  is released. Therefore, the self lock function of the worm gear  44  does not act upon the partly tooth-missing gear  40  and the charge lever  29 , resulting in the charge lever  29  being rotated clockwise by the elastic force F 22  of the charge-lever return spring  30 . When the charge lever  29  rotates clockwise, the front-curtain set lever  24  and the rear-curtain set lever  34  also rotate clockwise, and the charging of the front curtain  21  and the rear curtain  31  is also released. 
         [0158]    Therefore, in the states shown in  FIGS. 8 and 9 , the distal end of the claw  28   c  is hooked onto the reverse preventive part  29   da  provided to the front-curtain holding part  29   d  of the charge lever  29 . Thereby, the clockwise rotation of the charge lever  29  can be restricted, and it becomes possible to freely utilize the reverse rotation of the motor  46  to drive another member while maintaining the charge completion state. 
         [0159]    3.4: Slit Exposure Standby State 
         [0160]    When the release button  131  is operated by the user in the state shown in  FIG. 8 , necessary photography information such as photometry is obtained by the camera controller  140 . After completing obtaining the photography information, the release operation is started. 
         [0161]    Specifically, when the release button  131  is depressed, as shown in  FIG. 20 , in order to maintain the charge completion state of the front curtain  21  and the rear curtain  31 , power feeding to the front-curtain electromagnet  26  and the rear-curtain electromagnet  36  is started before the motor  46  is driven (steps S 5  and S 6 ). As a result, the front-curtain attracting piece  24   b  is attracted to the front-curtain electromagnet  26 , and the rear-curtain attracting piece  34   b  is attracted to the rear-curtain electromagnet  36 . Therefore, even when the front-curtain set lever  24  and the rear-curtain set lever  34  are permitted to rotate counterclockwise, the front-curtain set lever  24  and the rear-curtain set lever  34  are held at the charge position. 
         [0162]    After the power feeding to the front-curtain electromagnet  26  and the rear-curtain electromagnet  36  is started, the motor  46  is driven by a predetermined drive amount by the camera controller  140  (steps S 7 , S 8 , and S 9 ). Specifically, when the sun gear  43  is driven to rotate clockwise by the motor  46 , the charge lever  29  rotates counterclockwise. When the charge lever  29  rotates counterclockwise, the front-curtain holding part  29   d  of the charge lever  29  is retracted from the moving region  28   d  of the claw  28   c  of the front-curtain drive lever  28  before the meshing between the partly tooth-missing gear  40  and the partly tooth-missing gear part  29   e  is released, and the contacting between the front-curtain holding part  29   d  and the claw  28   c  is released. Thus, the front-curtain drive lever  28  rotates clockwise by the elastic force F 12  of the front-curtain set spring  27 , and the front curtain  21  runs from the second front curtain position P 12  to the first front curtain position P 11 . When the front-curtain-drive-lever contacting portion  28   b  abuts the front-curtain-set-lever contacting portion  24   a , the rotation of the front-curtain drive lever  28  stops and the front curtain  21  stops at the first front curtain position P 11 . Therefore, as shown in  FIG. 10 , the opening part  11   a  is shielded by the front curtain  21 . 
         [0163]    When the charge lever  29  further rotates counterclockwise, the meshing between the partly tooth-missing gear  40  and the partly tooth-missing gear part  29   e  of the charge lever  29  is released. When the meshing between the partly tooth-missing gear  40  and the partly tooth-missing gear part  29   e  is released, the contacting between the front-curtain set lever roller  24   c  and the front-curtain set cam  29   b  is released. When the contacting between the front-curtain set lever roller  24   c  and the front-curtain set cam  29   b  is released, the front-curtain set lever  24  is permitted to rotate counterclockwise by the elastic force F 11  of the front-curtain running spring  25 . Moreover, when the meshing between the partly tooth-missing gear  40  and the partly tooth-missing gear part  29   e  is released, the contacting between the rear-curtain set lever roller  34   c  and the rear-curtain set cam  29   c  is released. When the contacting between the rear-curtain set lever roller  34   c  and the rear-curtain set cam  29   c  is released, the rear-curtain set lever  34  is permitted to rotate counterclockwise by the elastic force F 21  of the rear-curtain running spring  35 . 
         [0164]    However, as described above, the power feeding to the front-curtain electromagnet  26  and the rear-curtain electromagnet  36  is started before the driving of the motor  46  is started, and thus, even when the front-curtain set lever  24  and the rear-curtain set lever  34  are permitted to rotate counterclockwise, the front-curtain set lever  24  and the rear-curtain set lever  34  are held at the charge position. That is, it is possible to maintain the charge completion state of the front curtain  21  and the rear curtain  31 . 
         [0165]    In this way, the state of the focal plane shutter device  190  proceeds from the state shown in  FIG. 8  to the slit exposure standby state shown in  FIG. 10 . In the state shown in  FIG. 10 , the opening part  11   a  is shielded by the front curtain  21  while the charge completion state of the front curtain  21  and the rear curtain  31  is maintained. 
         [0166]    3.5: Slit Exposure 
         [0167]    Thereafter, based on a release command from the camera controller  140 , the power feeding to the front-curtain electromagnet  26  is stopped (step S 10 ). Then, the front-curtain set lever  24  rotates counterclockwise by the elastic force F 11  of the front-curtain running spring  25 . At this time, the front-curtain-drive-lever contacting portion  28   b  is pushed by the front-curtain-set-lever contacting portion  24   a , and thus, the front-curtain drive lever  28  rotates counterclockwise together with the front-curtain set lever  24 , and the front curtain  21  runs from the first front curtain position P 11  to the second front curtain position P 12 . As a result, light is incident upon the CMOS image sensor  110  through the opening part  11   a , and exposing the CMOS image sensor  110  is started. 
         [0168]    On the other hand, after a previously-set exposure time elapses from the stop of the power feeding to the front-curtain electromagnet  26 , the power feeding to the rear-curtain electromagnet  36  is stopped (steps S 11  and S 12 ). The exposure time is set based on exposure information, etc., by the camera controller  140 . Once the power feeding to the rear-curtain electromagnet  36  is stopped, the rear-curtain set lever  34  rotates counterclockwise by the elastic force F 21  of the rear-curtain running spring  35 , and the rear curtain  31  runs from the second rear curtain position P 22  to the first rear curtain position P 21 . As a result, the opening part  11   a  is shielded by the rear curtain  31  sequentially from a lower portion of the opening part  11   a . At this time, a slit is formed between the front curtain  21  and the rear curtain  31 , and the slit moves from the downstream side to the upper side of the opening part  11   a . Thus, the CMOS image sensor  110  is exposed by light incident through the slit. The exposure operation by such a slit is called slit exposure photography. When the front curtain  21  and the rear curtain  31  complete running, the state of the focal plane shutter device  190  is changed to the state shown in  FIG. 6 . When the charge operation is performed, the state of the focal plane shutter device  190  is changed to the state shown in  FIG. 8 , and then, the process prepares for next photography. 
         [0169]    4: Operation of Electronic Front Curtain Photography 
         [0170]    Next, the operation of electronic front curtain photography will be explained. A flowchart shown in  FIG. 21  is a flowchart of the electronic front curtain photography. 
         [0171]    4.1: Running Completion State 
         [0172]    An end state of the operation of the electronic front curtain photography is the same as the end state of the above-described slit exposure photography. That is,  FIG. 6  shows a state where the running of the rear curtain  31  is completed by the electronic front curtain photography. 
         [0173]    4.2: Charge Operation 
         [0174]      FIGS. 14 and 15  show a state where only the rear curtain  31  completes charging for the electronic front curtain photography. Similarly to the charge operation at the time of the slit exposure photography, the motor  46  is energized in the limning completion state of  FIG. 6 , and the sun gear  43  rotates clockwise (step S 21 ). When the sun gear  43  rotates clockwise, the charge lever  29  rotates counterclockwise. 
         [0175]    However, in the charge operation of the electronic front curtain photography, the rotation of the charge lever  29  is stopped earlier than the charge completion state of the slit exposure photography shown in  FIG. 8 . Specifically, whether or not the drive amount of the motor  46  reaches a predetermined value is detected by the charge-lever detection switch  48  and the encoder vane  44   a , and the drive amount at this time is set smaller than the drive amount at the time of the charge for the slit exposure photography. Therefore, as shown in  FIG. 10 , upon completion of charging in the electronic front curtain photography, the rotation of the charge lever  29  is stopped just short of the rotation position of the charge lever  29  in the slit exposure photography. More particularly, the charge lever  29  stops at the rotation position shown in  FIGS. 12 and 13 . 
         [0176]    The operation of each member along with the counterclockwise rotation of the charge lever  29  is similar to the charge operation at the time of the slit exposure photography. In the charge completion state shown in  FIGS. 12 and 13 , the rear-curtain set lever roller  34   c  reaches the outer peripheral face  29   g  of the rear-curtain set cam  29   c . Therefore, the rear-curtain attracting piece  34   b  is pushed against the rear-curtain electromagnet  36 . 
         [0177]    On the other hand, the rotation of the charge lever  29  stops earlier than the charge operation for the slit exposure photography, and thus, although also the front-curtain set lever  24  slightly rotates clockwise, similarly to the rear-curtain set lever  34 , the front-curtain set lever roller  24   c  does not reach the outer peripheral face  29   f  of the front-curtain set cam  29   b . Therefore, the front-curtain attracting piece  24   b  has not rotated to a position at which the front-curtain electromagnet  26  can attract the front-curtain attracting piece  24   b.    
         [0178]    In a charge completion state shown in  FIG. 10 , the rear-curtain set lever  34  is coupled to the rear curtain  31 , and thus, the rear curtain  31  is disposed at the second rear curtain position P 22  and the rear curtain  31  is retracted downwardly from the opening part  11   a . Even after the charge is completed, the rear-curtain set cam  29   c  abuts the rear-curtain set lever roller  34   c , and thus, the state where the rear curtain  31  is retracted from the opening part  11   a  is maintained. 
         [0179]    On the other hand, the front-curtain set lever  24  slightly rotates clockwise, and also the front-curtain drive lever  28  attempts to rotate clockwise by the elastic force F 12  of the front-curtain set spring  27 . However, when the charge lever  29  rotates counterclockwise, the front-curtain holding part  29   d  already enters into the rotation trail of the claw  28   c  and the front-curtain holding part  29   d  restricts the rotation of the front-curtain drive lever  28 . The front-curtain drive lever  28  does not rotate during the above-described charge operation, and thus, the state where the front curtain  21  is retracted from the opening part  11   a  is maintained. Moreover, even after the charge operation, the claw  28   c  abuts the front-curtain holding part  29   d , and thus, the state where the front curtain  21  is retracted from the opening part  11   a  is maintained. 
         [0180]    In this way, the focal plane shutter device  190  can automatically maintain the state where the opening part  11   a  is opened during the charge operation and after the charge operation. That is, the focal plane shutter device  190  has a so-called normally open function. 
         [0181]    In a state shown in  FIG. 12 , the light from the subject is guided to the CMOS image sensor  110 . This state is effective particularly when the user wishes to maintain a state where the CMOS image sensor  110  is exposed. For example, this state is particularly effective when by using a live view function, the subject is observed, framing is performed, or moving picture photography is performed. At this time, by the self lock function of the worm gear  44 , the clockwise rotation of the charge lever  29  by the elastic force F 22  of the charge-lever return spring  30  is restricted. 
         [0182]    It is noted that unlike the state shown in  FIG. 8 , in the state shown in  FIG. 10 , the distal end of the claw  28   c  is not hooked onto the reverse preventive part  29   da  provided to the front-curtain holding part  29   d . That is, only by the self lock function of the worm gear  44 , the clockwise rotation of the charge lever  29  is restricted. 
         [0183]    4.3: Electronic Front Curtain Photography Standby State 
         [0184]    When the release button  131  is operated by the user, the necessary photography information such as photometry is obtained by the camera controller  140 . After completing obtaining the photography information, the release operation is started. When the release operation is started, the focal plane shutter device  190  proceeds from the state shown in  FIG. 10  to the electronic front curtain photography standby state shown in  FIG. 11 . 
         [0185]    Specifically, when the release button  131  is depressed, as shown in  FIG. 21 , in order to maintain the charge completion state of the rear curtain  31 , power feeding to the rear-curtain electromagnet  36  is started before the motor  46  is driven (steps S 25  and S 26 ). As a result, the rear-curtain attracting piece  34   b  is attracted to the rear-curtain electromagnet  36 . Therefore, even when the rear-curtain set lever  34  is permitted to rotate counterclockwise, the rear-curtain set lever  34  is held at the charge position. At this time, the power is not fed to the front-curtain electromagnet  26 , and thus, when the front-curtain set lever  24  is permitted to rotate counterclockwise, the front-curtain set lever  24  rotates to the position shown in  FIG. 6 . 
         [0186]    After the power feeding to the rear-curtain electromagnet  36  is started, the motor  46  is driven by a predetermined time by the camera controller  140  (steps S 27 , S 28 , and S 29 ). Unlike the above-described slit exposure photography, the motor  46  is reversed. When the motor  46  is reversed, the meshing between the planet gear  41  and the partly tooth-missing gear  40  is released. As a result, the self lock function of the worm gear  44  does not act upon the charge lever  29 . Thus, the charge lever  29  rotates clockwise until the charge lever  29  abuts the stopper  11   b  by the elastic force F 22  of the charge-lever return spring  30 . At this time, the contacting between the front-curtain holding part  29   d  of the charge lever  29  and the claw  28   c  of the front-curtain drive lever  28  is released. At this time, the contacting between the front-curtain set lever roller  24   c  and the front-curtain set cam  29   b  is also released, and thus, the front-curtain set lever  24  rotates counterclockwise by the elastic force F 11  of the front-curtain running spring  25 . The state where the front curtain  21  is retracted from the opening part  11   a  is kept. 
         [0187]    Moreover, when the charge lever  29  rotates clockwise and abuts the stopper  11   b , the contacting between the rear-curtain set lever roller  34   c  and the rear-curtain set cam  29   c  is released. However, the power feeding to the rear-curtain electromagnet  36  has been started before the contacting between the rear-curtain set lever roller  34   c  and the rear-curtain set cam  29   c  is released, and thus, the rear-curtain attracting piece  34   b  is attracted to the rear-curtain electromagnet  36 . Therefore, the charge state of the rear-curtain set lever  34  can be maintained, and the charge completion state of the rear curtain  31  is maintained. On the other hand, in the electronic front curtain photography, the front curtain  21  is not used, and thus, it is not necessary to feed power to the front-curtain electromagnet  26 , and as a result, it is possible to expect a power-saving effect. 
         [0188]    As described above, from the charge operation to the electronic front curtain photography standby state, the front curtain  21  hardly moves while maintaining the state where the front curtain  21  is retracted from the opening part  11   a . This eliminates a need such as the front curtain  21  waits for a drive time and waits for a convergence of bounds at the time of driving the front curtain  21 , and as a result, at the approximately same time as feeding the power to the motor  46  and the rear-curtain electromagnet  36 , the electronic front curtain photography by the CMOS image sensor  110  can be started. Thereby, it becomes possible to significantly shorten a release time lag. 
         [0189]    4.4: Electronic Front Curtain Exposure 
         [0190]    Thereafter, by the release command from the camera controller  140 , resetting electric charges and accumulating the electric charges are started from pixels on lower lines of the CMOS image sensor  110  (step S 30 ). The electric charges are sequentially reset from lower lines to upper lines. Subsequently, after resetting the electric charges and accumulating the electric charges are started, after a set exposure time elapses, the power feeding to the rear-curtain electromagnet  36  is stopped (steps S 31  and S 32 ). The exposure time is set based on the exposure information by the camera controller  140 . 
         [0191]    When the power feeding to the rear-curtain electromagnet  36  is stopped, the rear-curtain set lever  34  is permitted to rotate counterclockwise, and thus, the rear-curtain set lever  34  rotates counterclockwise by the elastic force F 21  of the rear-curtain running spring  35 , and the rear curtain  31  runs from the second rear curtain position P 22  to the first rear curtain position P 21 . As a result, the opening part  11   a  is shielded from the lower portion of the opening part  11   a . During a time when the electric charges are reset and the incident light is shielded by the rear curtain  31 , the CMOS image sensor  110  is exposed. An exposure operation in which the CMOS image sensor  110  is thus driven in tune with the running of the rear curtain  31  so as to scan the exposure region is called the electronic front curtain photography. When the rear curtain  31  completes running, the current state returns to the state of  FIG. 6  again. When the charge operation is performed again, the focal plane shutter device  190  is in a state of  FIG. 12 , and the process prepares for next photography. 
       Second Embodiment 
       [0192]    Subsequently, a second embodiment will be explained. In the second embodiment, points different from those in the first embodiment will be mainly explained, and the explanations for the common configuration in the first and second embodiments are omitted. Moreover, the same reference numerals are assigned to the configurations having the substantially same functions as those in the first embodiment. 
         [0193]    1: Digital Camera 
         [0194]    The digital camera  1  according to the second embodiment employs a focal plane shutter device  290 , instead of the focal plane shutter device  190 , and except for this, the digital camera  1  is basically configured similarly to the first embodiment. 
         [0195]    2: Configuration of the Focal Plane Shutter Device 
         [0196]    By using  FIGS. 23 to 32 , the focal plane shutter device  290  according to the second embodiment will be explained.  FIG. 23  is a state diagram of the focal plane shutter device  290  obtained when the rear curtain  31  completes running.  FIG. 24  is a detailed view of main parts of  FIG. 23 . 
         [0000]      FIGS. 25 and 26  are state diagrams of the focal plane shutter device  290  in a state where the charge is completed.  FIGS. 27 and 28  are state diagrams of the focal plane shutter device  290  in a slit exposure photography standby state.  FIGS. 29 and 30  are state diagrams of the focal plane shutter device  290  in the rear-curtain charge completion state.  FIGS. 31 and 32  are state diagrams of the focal plane shutter device  290  in the electronic front curtain photography standby state. During the slit exposure photography, the photography standby state is established in the order of  FIGS. 23 ,  25  and  27 . During the electronic front curtain photography, the photography standby state is established in the order of  FIGS. 23 ,  29 , and  31 . 
         [0197]    In addition to the configuration of the focal plane shutter device  190 , the focal plane shutter device  290  further includes: a front-curtain link lever  137 ; a front-curtain coupling arm  50 ; a rear-curtain link lever  138 ; and a rear-curtain coupling arm  51 . 
         [0198]    On the other hand, unlike the focal plane shutter device  190 , in the focal plane shutter device  290 , the front-curtain set lever  24  does not include the front-curtain set lever roller  24   c , and a first link mechanism  52  is coupled to the front-curtain set lever  24 . Specifically, the first link mechanism  52  includes the front-curtain coupling arm  50  and the front-curtain link lever  137 . 
         [0199]    A first end  50   a  of the front-curtain coupling arm  50  is rotatably coupled to the front-curtain set lever  24  via a shaft  24   d . The shaft  24   d  is fixed to the first end  50   a  of the front-curtain coupling arm  50  or the front-curtain set lever  24 . A second end  50   b  of the front-curtain coupling arm  50  is rotatably coupled to the first end  137   d  of the front-curtain link lever  137  via a shaft  137   c . The shaft  137   c  is fixed to the second end  50   b  of the front-curtain coupling arm  50  or the first end  137   d  of the front-curtain link lever  137 . The front-curtain link lever  137  is rotatably coupled to the shutter base plate  11  via a shaft  137   a . The shaft  137   a  is fixed to the shutter base plate  11 . To the second end of the front-curtain link lever  137 , a front-curtain charge lever roller  137   b  that abuts the front-curtain set cam  29   b  of the charge lever  29  is rotatably attached. 
         [0200]    Further, in the focal plane shutter device  290 , the rear-curtain set lever  34  does not include the rear-curtain set lever roller  34   c , and a second link mechanism  53  is coupled to the rear-curtain set lever  34 . Specifically, the second link mechanism  53  includes the rear-curtain coupling arm  51  and the rear-curtain link lever  138 . 
         [0201]    A first end  51   a  of the rear-curtain coupling arm  51  is rotatably coupled to the rear-curtain set lever  34  via a shaft  34   d . The shaft  34   d  is fixed to the first end  51   a  of the rear-curtain coupling arm  51  or the rear-curtain set lever  34 . A second end  51   b  of the rear-curtain coupling arm  51  is rotatably coupled to a first end  138   a  of the rear-curtain link lever  138  via a shaft  138   c . The shaft  138   c  is fixed to the second end  51   b  of the rear-curtain coupling arm  51  or the first end  138   a  of the rear-curtain link lever  138 . To a second end of the rear-curtain link lever  138 , a rear-curtain charge lever roller  138   b  that abuts the rear-curtain set cam  29   c  of the charge lever  29  is rotatably attached. 
         [0202]    The front-curtain charge lever roller  137   b  and the rear-curtain charge lever roller  138   b  are disposed in line in a direction vertical to the paper of  FIG. 14 , and thus, in  FIG. 14 , it looks as if the front-curtain charge lever roller  137   b  and the rear-curtain charge lever roller  138   b  were disposed at the substantially same location. 
         [0203]    At this time, the front-curtain set cam  29   b  and the rear-curtain set cam  29   c  of the charge lever  29  are disposed to be deviated in a rotation direction around a rotating shaft  29   a  of the charge lever  29 . Thereby, similarly to the first embodiment, the timing at which the rear curtain  31  completes charging is earlier than the timing at which the front curtain  21  completes charging. When the charge lever  29  rotates counterclockwise, the rear curtain  31  completes charging, and after that, the front curtain  21  completes charging. 
         [0204]    Specifically, when the charge lever  29  rotates counterclockwise, the rear-curtain set cam  29   c  gradually presses the rear-curtain charge lever roller  138   b . As a result, the rear-curtain set lever  34  rotates clockwise. When the rear-curtain charge lever roller  138   b  reaches the outer peripheral face  29   g  of the rear-curtain set cam  29   c , the rear-curtain attracting piece  34   b  is pushed against the rear-curtain electromagnet  36 . 
         [0205]    Likewise, when the charge lever  29  rotates counterclockwise, the front-curtain set cam  29   b  gradually presses the front-curtain charge lever roller  137   b . As a result, the front-curtain set lever  24  rotates clockwise. When the front-curtain charge lever roller  137   b  reaches the outer peripheral face  29   f  of the front-curtain set cam  29   b , the front-curtain attracting piece  24   b  is pushed against the front-curtain electromagnet  26 . 
         [0206]    In this way, shapes of the front-curtain set cam  29   b  and the rear-curtain set cam  29   c  are formed so that the contact between the rear-curtain attracting piece  34   b  and the rear-curtain electromagnet  36  is performed before the contact between the front-curtain attracting piece  24   b  and the front-curtain electromagnet  26 . Therefore, in the second embodiment, similarly to the first embodiment, the timing at which the charge mechanism  194  completes charging the rear-curtain running spring  35  is earlier than the timing at which the charge mechanism  194  completes charging the front-curtain running spring  25 . 
         [0207]    Moreover, the front-curtain set cam  29   b  and the rear-curtain set cam  29   c  of the focal plane shutter device  190  in the first embodiment are cams extending in a radial direction of the charge lever  29  from the rotating shaft  29   a  of the charge lever  29 . 
         [0208]    However, the front-curtain set cam  29   b  and the rear-curtain set cam  29   c  of the focal plane shutter device  290  in the second embodiment are spiral cams of which the diameter becomes larger according to the rotation amount of the charge lever  29 . When the spiral cam is used, a wedge effect occurs in the front-curtain link lever  137  and the rear-curtain link lever  138 , and a strong rotation force can be generated in the front-curtain set lever  24  and the rear-curtain set lever  34 . 
         [0209]    The rotation force generated by the front-curtain set cam  29   b  and the rear-curtain set cam  29   c  can be increased by adjusting a ratio of a distance between the shaft  137   a  and the front-curtain charge lever roller  137   b  to a distance between the shaft  137   a  and the shaft  137   c . Moreover, the rotation force generated by the front-curtain set cam  29   b  and the rear-curtain set cam  29   c  can be increased according to a ratio of a distance between the shaft  137   a  and the rear-curtain charge lever roller  138   b  to a distance between the shaft  137   a  and the shaft  138   c . Therefore, in the focal plane shutter device  290 , the charge operation with lower load and higher-speed can be implemented as compared to the focal plane shutter device  190 . 
         [0210]    Note that a series of operations and the controls for each of the slit exposure photography and the electronic front curtain photography are the same as those in the first embodiment, and thus, the detail explanation is omitted. 
       Other Embodiments 
       [0211]    The present invention is not limited to the above-described embodiments, and can be corrected and modified in various ways without departing from the gist of the present invention.
       (1) The above-described embodiments show the interchangeable-lens-type digital camera in which the camera body  100  and the lens unit  200  can be separated; however, even with a digital camera in which a lens unit is fixed to a camera body and the exposure is controlled by the focal plane shutter device, the similar effect can be demonstrated.       
 
         [0213]    (2) In the above-described embodiments, the timing at which the charge mechanism  194  completes charging the rear-curtain running spring  35  is earlier than the timing at which the charge mechanism  194  completes charging the front-curtain running spring  25 . However, the timing at which the charge mechanism  194  completes charging the rear-curtain running spring  35  may be different from the timing at which the charge mechanism  194  completes charging the front-curtain running spring  25 . For example, the timing at which the charge mechanism  194  completes charging the front-curtain running spring  25  is earlier than the timing at which the charge mechanism  194  completes charging the rear-curtain running spring  35 . 
         [0214]    (3) In the above-described embodiments, the timing at which the charge mechanism  194  starts charging the front-curtain running spring  25  is earlier than the timing at which the charge mechanism  194  starts charging the rear-curtain running spring  35 . However, the timing at which the charge mechanism  194  starts charging the front-curtain running spring  25  can be the same as the timing at which the charge mechanism  194  starts charging the rear-curtain running spring  35 , and the timing at which the charge mechanism  194  starts charging the rear-curtain running spring  35  can be earlier than the timing at which the charge mechanism  194  starts charging the front-curtain running spring  25 . 
         [0215]    (4) Although the charge lever  29  is explained as an example of the charge member in the above-described embodiments, the charge member is not limited to the charge lever  29 . The charge member can have other shapes, if the timing of the charge of the front-curtain is different from the timing of the charge of the rear-curtain. 
         [0216]    (5) Although a rock mechanism for holding the front curtain  21  at the second front curtain position P 12  is made up of the front-curtain holding part  29   d  and the claw  28   c  in the above-described embodiments, the front curtain  21  can be held at the second front curtain position P 12  using members other than the charge lever  29 . 
         [0217]    (6) Although the charge lever  29  is restricted to return to the original position by the reverse preventive part  29   da  and the claw  28   c , the charge lever  29  does not need to have the reverse preventive part  29   da.    
       Features of the Embodiments 
       [0218]    The features in the above-described embodiments are listed below. It is noted that the invention included in the above-described embodiments is not limited to below. Moreover, the components in parentheses after the respective configurations are specific examples of each configuration in order to facilitate the understanding of the characteristics. Each configuration should not be limited to these specific examples. Further, in order to obtain the effects described regarding each characteristic, the configuration other than the listed characteristics may be modified or deleted.
       (1) A focal plane shutter device according to a first aspect comprises:       
 
         [0220]    a shutter base plate ( 11 ) including an opening part ( 11   a ); 
         [0221]    a front curtain ( 21 ) movably disposed between a first front curtain position (P 11 ) at which the front curtain ( 21 ) covers the opening part ( 11   a ) and a second front curtain position (P 12 ) at which the front curtain ( 21 ) is retracted from the opening part ( 11   a ); 
         [0222]    a first elastic member (front-curtain running spring  25 ) for imparting the front curtain ( 21 ) with an elastic force so that the front curtain ( 21 ) moves from the first front curtain position (P 11 ) to the second front curtain position (P 12 ); 
         [0223]    a rear curtain ( 31 ) movably disposed between a first rear curtain position (P 21 ) at which the rear curtain ( 31 ) covers the opening part ( 11   a ) and a second rear curtain position (P 22 ) at which the rear curtain ( 31 ) is retracted from the opening part ( 11   a ); 
         [0224]    a second elastic member (rear-curtain running spring  35 ) for imparting the rear curtain ( 31 ) with an elastic force so that the rear curtain ( 31 ) moves from the second rear curtain position (P 22 ) to the first rear curtain position (P 21 ); and a charge mechanism ( 194 ) arranged to impart the first elastic member (front-curtain running spring  25 ) and the second elastic member (rear-curtain running spring  35 ) with a first biasing force resisting the elastic force of the first elastic member (front-curtain running spring  25 ) and a second biasing force resisting the elastic force of the second elastic member (rear-curtain running spring  35 ), wherein 
         [0225]    a timing at which the charge mechanism ( 194 ) completes imparting the first elastic member (front-curtain running spring  25 ) with the first biasing force is different from a timing at which the charge mechanism ( 194 ) completes imparting the second elastic member (rear-curtain running spring  35 ) with the second biasing force. 
         [0226]    At the time of completion or about the time of completion of imparting the first elastic member (front-curtain running spring  25 ) with the first biasing force, a force required for imparting the first biasing force is at the maximum. Moreover, at the time of completion or about the time of completion of imparting the second elastic member (rear-curtain running spring  35 ) with the second biasing force, a force required for imparting the biasing force is at the maximum. 
         [0227]    However, in the focal plane shutter device, the timing at which the charge mechanism ( 194 ) completes imparting the first elastic member (front-curtain running spring  25 ) with the first biasing force is different from the timing at which the charge mechanism ( 194 ) completes imparting the second elastic member (rear-curtain running spring  35 ) with the second biasing force. Thus, it is possible to reduce maximum values of a total of the first biasing force and the second biasing force. This can decrease a load of the charge mechanism ( 194 ). 
         [0228]    Moreover, in the focal plane shutter device, it is possible to perform a slit exposure photography by the front curtain ( 21 ) and the rear curtain ( 31 ). 
         [0229]    Therefore, with the focal plane shutter device, it is possible to perform the slit exposure photography using the front curtain ( 21 ) and the rear curtain ( 31 ), and moreover, it is possible to decrease a load of a drive source at the time of charging the front curtain ( 21 ) and the rear curtain ( 31 ).
       (2) A focal plane shutter device according to a second aspect is the focal plane shutter device according to the first aspect, wherein       
 
         [0231]    the timing at which the charge mechanism ( 194 ) completes imparting the second elastic member (rear-curtain running spring  35 ) with the second biasing force is earlier than the timing at which the charge mechanism ( 194 ) completes imparting the first elastic member (front-curtain running spring  25 ) with the first biasing force. 
         [0232]    With this focal plane shutter device, since the charge completion of the rear curtain ( 31 ) can be earlier, it is possible to speed up the electric front curtain photography.
       (3) A focal plane shutter device according to a third aspect is the focal plane shutter device according to the first or second aspect, wherein       
 
         [0234]    the charge mechanism ( 194 ) holds the front curtain ( 21 ) at the second front curtain position (P 12 ) while imparting the first elastic member (front-curtain running spring  25 ) with the first biasing force. 
         [0235]    With this focal plane shutter device, the charge of the front curtain ( 21 ) can be performed in a state where the front curtain ( 21 ) is disposed at second front curtain position (P 12 ). Therefore, the charge of the front curtain ( 21 ) can be performed while maintaining the live view state, and this allows a time lag of photography to be shorten.
       (4) A focal plane shutter device according to a fourth aspect is the focal plane shutter device according to any one of the first to third aspects, wherein       
 
         [0237]    the charge mechanism ( 194 ) includes an actuator (motor  46 ) generating the first biasing force and the second biasing force; and a charge member (charge lever  29 ) arranged to transmit the first biasing force to the first elastic member (front-curtain running spring  25 ) and arranged to transmit the second biasing force to the second elastic member (rear-curtain running spring  35 ).
       (5) A focal plane shutter device according to a fifth aspect is the focal plane shutter device according to the fourth aspect, wherein       
 
         [0239]    the actuator (motor  46 ) is capable of driving the charge member (charge lever  29 ) to a first charge completion position at which imparting the first elastic member (front-curtain running spring  25 ) with the first biasing force is completed, and to a second charge completion position which is different from the first charge completion position and at which imparting the second elastic member (rear-curtain running spring  35 ) with the second biasing force is completed.
       (6) A focal plane shutter device according to a sixth aspect is the focal plane shutter device according to the fifth aspect, wherein       
 
         [0241]    the actuator (motor  46 ) is capable of driving the charge member (charge lever  29 ) to a first charge start position at which imparting the first elastic member (front-curtain running spring  25 ) with first biasing force is started, and to a second charge start position which is the same as or different from the first charge start position and at which imparting the second elastic member (rear-curtain running spring  35 ) with the second biasing force is started, and the second charge completion position is disposed between the second charge start position and the first charge completion position.
       (7) A focal plane shutter device according to a seventh aspect is the focal plane shutter device according to the fifth or sixth aspect, further comprising:       
 
         [0243]    a front-curtain drive member (front-curtain drive lever  28 ) for coupling the front curtain ( 21 ) to the shutter base plate ( 11 ) to be movable between the first front curtain position (P 11 ) and the second front curtain position (P 12 ); and a front-curtain set member (front-curtain set lever  24 ) arranged to transmit the elastic force of the first elastic member (front-curtain running spring  25 ) to the front-curtain drive member (front-curtain drive lever  28 ), wherein 
         [0244]    the charge member (charge lever  29 ) transmits the first biasing force to the first elastic member (front-curtain running spring  25 ) via the front-curtain set member (front-curtain set lever  24 ).
       (8) A focal plane shutter device according to an eighth aspect is the focal plane shutter device according to the seventh aspect, wherein       
 
         [0246]    the charge member (charge lever  29 ) includes a front-curtain cam part (front-curtain set cam  29   b ) arranged to be contactable with the front-curtain set member (front-curtain set lever  24 ), and 
         [0247]    when the charge member (charge lever  29 ) is at the first charge completion position, the front-curtain cam part (front-curtain set cam  29   b ) is in contact with the front-curtain set member (front-curtain set lever  24 ).
       (9) A focal plane shutter device according to a ninth aspect is the focal plane shutter device according to the eighth aspect, further comprising:       
 
         [0249]    a rear-curtain drive member coupling the rear curtain ( 31 ) to the shutter base plate ( 11 ) to be movable between the first rear curtain position (P 21 ) and the second rear curtain position (P 22 ), and capable of transmitting the elastic force of the second elastic member (rear-curtain running spring  35 ) to the rear curtain ( 31 ), wherein 
         [0250]    the charge member (charge lever  29 ) transmits the second biasing force to the second elastic member (rear-curtain running spring  35 ) via the rear-curtain set member (rear-curtain set lever  34 ).
       (10) A focal plane shutter device according to a tenth aspect is the focal plane shutter device according to the ninth aspect, wherein       
 
         [0252]    the charge member (charge lever  29 ) includes a rear-curtain cam part (rear-curtain set cam  29   c ) arranged to be contactable with the rear-curtain set member (rear-curtain set lever  34 ), and 
         [0253]    when the charge member (charge lever  29 ) is at the second charge completion position, the rear-curtain cam part (rear-curtain set cam  29   c ) is in contact with the rear-curtain set member (rear-curtain set lever  34 ).
       (11) A focal plane shutter device according to an eleventh aspect is the focal plane shutter device according to the tenth aspect, wherein       
 
         [0255]    when the charge member (charge lever  29 ) is at the second charge start position, a gap is secured between the front-curtain cam part (front-curtain set cam  29   b ) and the front-curtain set member (front-curtain set lever  24 ).
       (12) A focal plane shutter device according to a twelfth aspect is the focal plane shutter device according to any one of the seventh to eleventh aspects, further comprising       
 
         [0257]    a third elastic member (front-curtain set spring  27 ) for imparting the front-curtain drive member (front-curtain drive lever  28 ) with an elastic force smaller than the elastic force of the first elastic member (front-curtain running spring  25 ) so that the front curtain ( 21 ) moves from the second front curtain position (P 12 ) to the first front curtain position (P 11 ), wherein 
         [0258]    the charge member (charge lever  29 ) is capable of holding the front curtain ( 21 ) at the second front curtain position (P 12 ) via the front-curtain drive member (front-curtain drive lever  28 ).
       (13) A focal plane shutter device according to a thirteenth aspect is the focal plane shutter device according to the twelfth aspect, wherein       
 
         [0260]    when the charge member (charge lever  29 ) is at the first charge completion position, the charge member (charge lever  29 ) holds the front curtain ( 21 ) at the second front curtain position (P 12 ) via the front-curtain drive member (front-curtain drive lever  28 ).
       (14) A focal plane shutter device according to a fourteenth aspect is the focal plane shutter device according to the thirteenth aspect, wherein       
 
         [0262]    the actuator (motor  46 ) is capable of driving the charge member (charge lever  29 ) to a release position on the opposite side of the first charge start position relative to the first charge completion position, and when the charge member (charge lever  29 ) is at the release position, the charge member (charge lever  29 ) cancels the holding of the front curtain ( 21 ) at the second front curtain position (P 12 ).
       (15) A focal plane shutter device according to a fifteenth aspect is the focal plane shutter device according to the fourteenth aspect, wherein       
 
         [0264]    the charge member (charge lever  29 ) includes a front-curtain holding part ( 29   d ) for holding the front curtain ( 21 ) at the second front curtain position (P 12 ) via the front-curtain drive member (front-curtain drive lever  28 ), 
         [0265]    the front-curtain drive member (front-curtain drive lever  28 ) includes a contacting portion (claw  28   c ) provided in a manner to abut the front-curtain holding part ( 29   d ), 
         [0266]    when the charge member (charge lever  29 ) is at the first charge completion position, the front-curtain holding part ( 29   d ) enters into a moving region ( 28   d ) where the contacting portion moves when the front curtain ( 21 ) moves from the second front curtain position (P 12 ) to the first front curtain position (P 11 ), and 
         [0267]    when the charge member (charge lever  29 ) is at the release position, the front-curtain holding part ( 29   d ) is retracted from the moving region ( 28   d ) of the contacting portion.
       (16) A focal plane shutter device according to a sixteenth aspect is the focal plane shutter device according to any one of the seventh to fifteenth aspects, further comprising       
 
         [0269]    a return elastic member (charge lever return spring  30 ) for imparting the charge member (charge lever  29 ) with an elastic force so that the charge member (charge lever  29 ) returns to an original position obtained before imparting the first biasing force and the second biasing force is started, wherein 
         [0270]    the actuator (motor  46 ) is capable of driving the charge member (charge lever  29 ) to a restriction position, and 
         [0271]    when the charge member (charge lever  29 ) is at the restriction position, the front-curtain drive member (front-curtain drive lever  28 ) restricts the returning of the charge member (charge lever  29 ) to the original position.
       (17) A focal plane shutter device according to a seventeenth aspect is the focal plane shutter device according to any one of the first to sixth aspects, further comprising:       
 
         [0273]    a front-curtain drive member (front-curtain drive lever  28 ) for coupling the front curtain ( 21 ) to the shutter base plate ( 11 ) to be movable between the first front curtain position (P 11 ) and the second front curtain position (P 12 ); and 
         [0274]    a front-curtain set member (front-curtain set lever  24 ) arrange to transmit the elastic force of the first elastic member (front-curtain running spring  25 ) to the front-curtain drive member (front-curtain drive lever  28 ), wherein 
         [0275]    at the time of imparting the first elastic member (front-curtain running spring  25 ) with the first biasing force, the charge mechanism ( 194 ) imparts the first elastic member (front-curtain running spring  25 ) with the first biasing force via the front-curtain set member (front-curtain set lever  24 ).
       (18) A focal plane shutter device according to an eighteenth aspect is the focal plane shutter device according to the seventeenth aspect, wherein       
 
         [0277]    when the front curtain ( 21 ) moves from the first front curtain position (P 11 ) to the second front curtain position (P 12 ), the front-curtain set member (front-curtain set lever  24 ) transmits the elastic force of the first elastic member (front-curtain running spring  25 ) to the front curtain ( 21 ) via the front-curtain drive member (front-curtain drive lever  28 ), and 
         [0278]    when the charge mechanism ( 194 ) imparts the first elastic member (front-curtain running spring  25 ) with the first biasing force, the front-curtain set member (front-curtain set lever  24 ) imparts the first elastic member (front-curtain running spring  25 ) with the first biasing force without intervention of the front-curtain drive member (front-curtain drive lever  28 ).
       (19) A focal plane shutter device according to a nineteenth aspect is the focal plane shutter device according to any one of the first to eighteenth aspects, wherein       
 
         [0280]    a timing at which the charge mechanism ( 194 ) starts imparting the second elastic member (rear-curtain running spring  35 ) with the second biasing force is earlier than a timing at which the charge mechanism ( 194 ) starts imparting the first elastic member (front-curtain running spring  25 ) with the first biasing force.
       (20) An imaging device according to a twentieth aspect comprises:       
 
         [0282]    the focal plane shutter device according to any one of the fifth to sixteenth aspects; 
         [0283]    an imaging element (CMOS image sensor  110 ) for converting an optical image of a subject into an image signal; and 
         [0284]    a controller (camera controller  140 ) for controlling the imaging element (CMOS image sensor  110 ) and the focal plane shutter device, wherein 
         [0285]    the imaging element (CMOS image sensor  110 ) includes an electronic front curtain photography function for sequentially resetting a pixel in a running direction (R) of the front curtain ( 21 ), and 
         [0286]    the controller (camera controller  140 ) establishes an electronic front curtain photography standby state at a time point when the charge mechanism ( 194 ) for controlling the actuator (motor  46 ) at the time of photographing by using the electronic front curtain photography function so that the charge member (charge lever  29 ) stops at the second charge completion position completes imparting the second elastic member (rear-curtain running spring  35 ) with the second biasing force and when the charge mechanism ( 194 ) does not complete imparting the first elastic member (front-curtain running spring  25 ) with the first biasing force.
       (21) A focal plane shutter device according to a twenty-first aspect comprises:       
 
         [0288]    a shutter base plate ( 11 ) including an opening part ( 11   a ); 
         [0289]    a front curtain ( 21 ) disposed to be movable between a first front curtain position (P 11 ) covering the opening part ( 11   a ) and a second front curtain position (P 12 ) retracted from the opening part ( 11   a ); 
         [0290]    a first elastic member (front-curtain running spring  25 ) for imparting the front curtain ( 21 ) with an elastic force so that the front curtain ( 21 ) moves from the first front curtain position (P 11 ) to the second front curtain position (P 12 ); 
         [0291]    a rear curtain ( 31 ) disposed to be movable between the first rear curtain position (P 21 ) covering the opening part ( 11   a ) and the second rear curtain position (P 22 ) retracted from the opening part ( 11   a ); 
         [0292]    a second elastic member (rear-curtain running spring  35 ) for imparting the rear curtain ( 31 ) with an elastic force so that the rear curtain ( 31 ) moves from the second rear curtain position (P 22 ) to the first rear curtain position (P 21 ); 
         [0293]    an actuator (motor  46 ) for generating a first biasing force resisting the elastic force of the first elastic member (front-curtain running spring  25 ) and a second biasing force resisting the elastic force of the second elastic member (rear-curtain running spring  35 ); and 
         [0294]    a charge member (charge lever  29 ) arranged to transmit the first biasing force to the first elastic member (front-curtain running spring  25 ) and arranged to transmit the second biasing force to the second elastic member (rear-curtain running spring  35 ), wherein 
         [0295]    the charge member (charge lever  29 ) holds the front curtain ( 21 ) at the second front curtain position (P 12 ) while imparting the first elastic member (front-curtain running spring  25 ) with the first biasing force. 
         [0296]    In this focal plane shutter device, the front curtain ( 21 ) is held at the second front curtain position (P 12 ) by the charge member (charge lever  29 ) while imparting the first elastic member (front-curtain running spring  25 ) with the first biasing force, and thus, an open state of the opening part ( 11   a ) is maintained at the time of charging the front curtain ( 21 ) and the rear curtain ( 31 ). 
         [0297]    Moreover, in the focal plane shutter device, it is possible to perform a slit exposure photography by the front curtain ( 21 ) and the rear curtain ( 31 ). 
         [0298]    Therefore, in the focal plane shutter device, it is possible to perform the slit exposure photography using the front curtain ( 21 ) and the rear curtain ( 31 ), and moreover, it is possible to maintain the open state of the opening part ( 11   a ) at the time of charging the front curtain ( 21 ) and the rear curtain ( 31 ).
       (22) A focal plane shutter device according to a twenty-second aspect is the focal plane shutter device according to the twenty-first aspect, wherein       
 
         [0300]    the charge member (charge lever  29 ) holds the front curtain ( 21 ) at the second front curtain position (P 12 ) after imparting the first elastic member (front-curtain running spring  25 ) with the first biasing force is completed.
       (23) A focal plane shutter device according to a twenty-third aspect is the focal plane shutter device according to the twenty-first or twenty-second aspect, comprising:       
 
         [0302]    a front-curtain drive member (front-curtain drive lever  28 ) for coupling the front curtain ( 21 ) to the shutter base plate ( 11 ) to be movable between the first front curtain position (P 11 ) and the second front curtain position (P 12 ); and 
         [0303]    a front-curtain set member (front-curtain set lever  24 ) arranged to transmit the elastic force of the first elastic member (front-curtain running spring  25 ) to the front-curtain drive member (front-curtain drive lever  28 ), wherein 
         [0304]    the charge member (charge lever  29 ) transmits the first biasing force to the first elastic member (front-curtain running spring  25 ) via the front-curtain set member (front-curtain set lever  24 ).
       (24) A focal plane shutter device according to a twenty-fourth aspect is the focal plane shutter device according to the twenty-third aspect, further comprising       
 
         [0306]    a third elastic member (front-curtain set spring  27 ) for imparting the front-curtain drive member (front-curtain drive lever  28 ) with an elastic force smaller than the elastic force of the first elastic member (front-curtain running spring  25 ) so that the front curtain ( 21 ) moves from the second front curtain position (P 12 ) to the first front curtain position (P 11 ), wherein 
         [0307]    the charge member (charge lever  29 ) is capable of holding the front curtain ( 21 ) at the second front curtain position (P 12 ) via the front-curtain drive member (front-curtain drive lever  28 ). 
       General Interpretation of Terms 
       [0308]    In understanding the scope of the present disclosure, the term “comprising” and its derivatives, as used herein, are intended to be open ended terms that specify the presence of the stated features, elements, components, groups, integers, and/or steps, but do not exclude the presence of other unstated features, elements, components, groups, integers and/or steps. The foregoing also applies to words having similar meanings such as the terms, “including”, “having” and their derivatives. Also, the terms “part,” “section,” “portion,” “member” or “element” when used in the singular can have the dual meaning of a single part or a plurality of parts. Also as used herein to describe the above embodiment(s), the following directional terms “forward”, “rearward”, “above”, “downward”, “vertical”, “horizontal”, “below” and “transverse” as well as any other similar directional terms refer to those directions of an imaging device equipped with the focal plane shatter device. Accordingly, these terms, as utilized to describe the present invention should be interpreted relative to an imaging device equipped with the focal plane shatter device. 
         [0309]    The term “configured” as used herein to describe a component, section, or part of a device implies the existence of other unclaimed or unmentioned components, sections, members or parts of the device to carry out a desired function. 
         [0310]    The terms of degree such as “substantially”, “about” and “approximately” as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. 
         [0311]    While only selected embodiments have been chosen to illustrate the present invention, it will be apparent to those skilled in the art from this disclosure that various changes and modifications can be made herein without departing from the scope of the invention as defined in the appended claims. Furthermore, the foregoing descriptions of the embodiments according to the present invention are provided for illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents. Thus, the scope of the invention is not limited to the disclosed embodiments.
A focal plane shutter device is disclosed that includes a shutter base plate, a front curtain, a first urging member, a rear curtain, a second urging member, and a charge mechanism. The shutter base plate defines an opening. The front curtain is moved between different positions by the first urging member to cover and uncover the opening. The rear curtain is moved between different positions by the second urging member to cover and uncover the opening. The charge mechanism applies a first force to resist an urging force by the first urging member and a second force to resist an urging force by the second urging member. The first force applied by the charge mechanism terminates at a different time than the second force applied by the charge mechanism.