Abstract:
A method of driving an SLR camera using a single motor includes driving the motor forward to perform a mirror release operation, driving the motor in reverse to switch a motor drive system including the motor to a mirror-shutter charge system and performing a mirror-shutter charge operation, driving the motor to continue rotating in reverse to switch the motor drive system a film wind system, driving the motor to continue rotating in reverse to perform a film wind operation, driving the motor forward for a predetermined period of time to switch the motor drive system from the film wind system to a film rewind system upon detecting that there are no more film frames available, and driving the motor in reverse to perform the film rewind operation.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a method and system for driving an SLR camera.  
           [0003]    2. Description of the Related Art  
           [0004]    SLR cameras using a single motor to perform multiple driving operations, e.g., a film wind operation, a film rewind operation, a mirror-shutter charge operation, and a mirror release operation in which a quick-return mirror rises upon a shutter release, are known in the art.  
         SUMMARY OF THE INVENTION  
         [0005]    The present invention provides a method and system for driving an SLR camera that uses a single motor to perform such multiple driving operations in a control mode different from any control modes of conventional SLR cameras that use a single motor to perform similar multiple driving operations.  
           [0006]    According to an aspect of the present invention, a method of driving an SLR camera, having a film, is provided, using a single motor to perform a film wind operation, a film rewind operation, a mirror-shutter charge operation, and a mirror release operation in which a quick-return mirror rises upon a shutter release, the method including driving the motor forward to perform the mirror release operation upon a detection of the shutter release; driving the motor in reverse to firstly switch a motor drive system including the motor to a mirror-shutter charge system upon detecting a signal indicating that an operation of a shutter is completed, and subsequently performing the mirror-shutter charge operation; driving the motor to continue rotating in reverse to switch the motor drive system from the mirror-shutter charge system to a film wind system even after the quick-return mirror returns to a viewing position by the mirror-shutter charge operation; driving the motor to continue rotating in reverse to perform the film wind operation; driving the motor forward for a predetermined period of time to switch the motor drive system from the film wind system to a film rewind system upon detecting a signal indicating that no more frames of the film are available; and driving the motor in reverse to perform the film rewind operation.  
           [0007]    It is desirable for the method to further include putting the motor drive system into a state where the motor drive system is prevented from switching to the mirror-shutter charge system when the film wind operation and film rewind operation are performed; and putting the motor drive system into a state where the motor drive system is allowed to switch to the mirror-shutter charge system in conjunction with a rising motion of the quick-return mirror upon the mirror release operation.  
           [0008]    In another embodiment, a driving system for an SLR camera, having a film, is provided, using a single motor to perform a film wind operation, a film rewind operation, a mirror-shutter charge operation, and a mirror release operation in which a quick-return mirror rises upon a shutter release, the driving system including a release device which drives the motor forward to perform the mirror release operation upon a detection of the shutter release; a switch/charge device which is actuated upon the motor being driven in reverse to firstly switch a motor drive system including the motor to a mirror-shutter charge system upon detecting a signal indicating that an operation of a shutter is completed, and subsequently perform the mirror-shutter charge operation; a first switch device which drives the motor to continue rotating reverse to switch the motor drive system from the mirror-shutter charge system to a film wind system even after the quick-return mirror returns to a viewing position by the mirror-shutter charge operation; a film wind device which drives the motor to continue rotating reverse to perform the film wind operation; a second switch device which drives the motor forward for a predetermined period of time to switch the motor drive system from the film wind system to a film rewind system upon detecting a signal indicating that no more film frame is available; and a film rewind device which drives the motor reverse to perform the film rewind operation.  
           [0009]    It is desirable for the driving system to further include a locking device which puts the motor drive system into a state where the motor drive system is prevented from switching to the mirror-shutter charge system when the film wind operation and film rewind operation are performed; and an unlocking device which puts the motor drive system into a state where the motor drive system is allowed to switch to the mirror-shutter charge system in conjunction with a rising motion of the quick-return mirror upon the mirror release operation.  
           [0010]    In another embodiment, an SLR camera is provided, using a single motor to perform a film wind operation, a film rewind operation, a mirror-shutter charge operation, and a mirror release operation in which a quick-return mirror rises upon a shutter release, the SLR camera including a film-wind gear mechanism used for the film wind operation; a film-rewind gear mechanism used for the film rewind operation; a mirror-shutter charge gear mechanism used for the mirror release operation; a mirror release gear mechanism used for the mirror release operation; a motor drive gear mechanism which is selectively engaged with the film wind gear mechanism, the film rewind gear mechanism, the mirror-shutter charge gear mechanism and the mirror release gear mechanism; and a motor controller for controlling operation of the motor. The motor controller drives the motor forward to bring the motor drive gear mechanism into engagement with the mirror release gear mechanism to perform the mirror release operation upon a detection of the shutter release, a rising motion of the quick-return mirror making it possible to bring the motor drive gear mechanism into engagement with the mirror-shutter charge gear mechanism. The motor controller drives the motor in reverse to firstly bring the motor drive gear mechanism into engagement with the mirror-shutter charge gear mechanism upon detecting a signal indicating that an operation of a shutter is completed, and subsequently perform the mirror-shutter charge operation. The motor controller drives the motor to continue rotating in reverse to bring the motor drive gear mechanism into engagement with the film wind gear mechanism even after the quick-return mirror returns to a viewing position by the mirror-shutter charge operation. The motor controller drives the motor to continue rotating in reverse to perform the film wind operation. The motor controller drives the motor forward for a predetermined period of time to bring the motor drive gear mechanism into engagement with the film rewind gear mechanism upon detecting a signal indicating that no more film frame is available. The motor controller drives the motor reverse to perform the film rewind operation.  
           [0011]    In another embodiment, a driving system for an SLR camera is provided, including a motor; a release mechanism which performs a mirror-shutter release operation in which a quick-return mirror is removed from a viewing position, on a photographing path, to raised position, out of the photographing path, and a mechanical stopper for a shutter is released; a charge mechanism which performs a mirror-shutter charge operation in which the quick-return mirror is returned to the viewing position and the shutter is charged; a film-wind mechanism which performs a film wind operation; a film rewind mechanism which performs a film rewind operation; and a switching device provided between the motor and the release mechanism, the charge mechanism, the film-wind mechanism, and the film rewind mechanism, wherein the mirror-shutter release operation is performed by the release mechanism when the motor drives forward; and wherein the mirror-shutter charge operation, the film wind operation and the film rewind operation are performed by the charge mechanism, the film wind mechanism and the film rewind mechanism, respectively, when the motor drives in reverse after the release operation is completed.  
           [0012]    The present disclosure relates to subject matter contained in Japanese Patent Application No.2002-189797 (filed on Jun. 28, 2002) which is expressly incorporated herein by reference in its entirety. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    The present invention will be described below in detail with reference to the accompanying drawings in which:  
         [0014]    [0014]FIG. 1 is a system diagram of a fundamental portion of an embodiment of a driving system for driving an SLR camera in an initial state (i.e., in a state before a shutter release signal is issued), according to the present invention;  
         [0015]    [0015]FIG. 2 is a system diagram of the embodiment of a fundamental portion of the SLR camera driving system in a state immediately after a mirror-shutter charge operation commences after a shutter release operation is completed;  
         [0016]    [0016]FIG. 3 is a system diagram of the embodiment of a fundamental portion of the SLR camera driving system in a state where the mirror-shutter charge operation is almost completed;  
         [0017]    [0017]FIG. 4 is a system diagram of the embodiment of a fundamental portion of the SLR camera driving system in a state where a motor drive system of the SLR camera driving system is in the process of being switched from a mirror-shutter charge system to a film wind system after the mirror-shutter charge operation is completed;  
         [0018]    [0018]FIG. 5 is a system diagram of the embodiment of a fundamental portion of the SLR camera driving system in a state where a film wind operation by the film wind system is completed;  
         [0019]    [0019]FIG. 6 is a system diagram of the embodiment of a fundamental portion of the SLR camera driving system in a state where a film rewind operation is performed;  
         [0020]    [0020]FIG. 7A is a side elevational view of a mirror drive mechanism and peripheral components including components of the mirror-shutter charge system in a state where a quick-return mirror is in a viewing position (initial position);  
         [0021]    [0021]FIG. 7B is a view similar to that of FIG. 7A, showing a state where the quick-return mirror is in a raised position (retracted position);  
         [0022]    [0022]FIG. 8 is a first half of a timing chart showing fundamental operations of the SLR camera driving system; and  
         [0023]    [0023]FIG. 9 is a latter half of the timing chart showing fundamental operations of the SLR camera driving system. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0024]    [0024]FIGS. 1 through 6 are system diagrams of an embodiment of a driving system for driving an SLR camera according to the present invention, showing different operating states thereof. In some of these figures, only elements of the SLR camera driving system which are associated with descriptions of the operations performed in the operational state are shown for the purpose of clarity.  
         [0025]    [0025]FIG. 1 shows the SLR camera driving system in an initial state (i.e., in a state before a shutter release signal is issued after a mirror-shutter charge operation is completed). In this state, leading and trailing curtains of a focal plane shutter (not shown) are mechanically latched (held) at respective charge completion positions. The SLR camera driving system is provided with a motor  10  (see FIG. 1), a motor controller  9  which controls operation of the motor  10 , and a drive pinion  11  which is fixed on a rotary shaft of the motor  10 . The SLR camera driving system is provided in the vicinity of the drive pinion  11  with a first double gear  12 , a second double gear  13  and a third double gear  14 . The drive pinion  11  is in mesh with a large gear of the first double gear  12 , a small gear of the first double gear  12  is in mesh with a large gear of the second double gear  13 , and a small gear of the second double gear  13  is in mesh with a large gear of the third double gear  14 . The SLR camera driving system is provided with a first planetary gear mechanism having the third double gear  14  serving as a sun gear, and a first planet gear  16  which is in mesh with a small gear of the third double gear  14 . A first swingable lever  15  is pivoted at one end thereof about a rotational shaft  14   a  of the third double gear  14 . The first planet gear  16  is rotatably fitted on a pin which is fixed at a free end of the first swingable lever  15  to extend parallel to the rotational shaft  14   a . The first swingable lever  15  swings about the rotational shaft  14   a  in forward and reverse directions by rotation of the first planet gear  16  around the small gear of the third double gear  14 . In a state shown in FIG. 1, the drive pinion  11  (motor  10 ) rotates in a forward direction, so that the first swingable lever  15  that bears the first planet gear  16  rotates clockwise as viewed in FIG. 1. The drive pinion  11 , the first, second and third double gears  12 ,  13  and  14 , the first swingable lever  15  and the first planet gear  16  constitute a motor-drive gear mechanism.  
         [0026]    The SLR camera driving system is further provided with mirror-release gear mechanism (release mechanism) having a first idle gear  17 , a second idle gear  18 , a cam-incorporated gear  19 , a release lever  20  and a mirror charge lever  21 . When the first swingable lever  15  rotates clockwise as viewed in FIG. 1, the first planet gear  16  that is rotatably fixed at the free end of the first swingable lever  15  is in mesh with the first idle gear  17  which is in mesh with the second idle gear  18 , and the cam-incorporated gear  19  is in mesh with the second idle gear  18 . Namely, when the first swingable lever  15  rotates clockwise as viewed in FIG. 1, the planet gear  16  is engaged with the cam-incorporated gear  19  via the first and second idle gears  17  and  18 . The cam-incorporated gear  19  is provided on front and rear sides thereof with a release cam  19   a  shown by solid line in FIG. 1 and a lock cam  19   b  shown by dotted lines in FIG. 1. The release cam  19   a  is symmetrical with respect to a rotational axis of the cam-incorporated gear  19 . The release cam  19   a  is composed of a pair of pressure cam edges  19   a   1 , the distances of which gradually increase in a counterclockwise direction from the rotational axis of the cam-incorporated gear  19  as viewed in FIG. 1, and a pair of cam edges  19   a   2 , the distances of which suddenly decrease in a counterclockwise direction from the rotational axis of the cam-incorporated gear  19  as viewed in FIG. 1.  
         [0027]    The release lever  20  is positioned in the vicinity of the cam-incorporated gear  19 . The release lever  20  is pivoted about a rotational shaft  20   a  extending parallel to the rotational axis of the cam-incorporated gear  19 . The release lever  20  is provided with a first arm portion  20   b  and a second arm portion  20   c  which extend substantially orthogonal to each other. The first arm portion  20   b  is provided at a tip thereof with a follower roller  20   d  which is engaged with the release cam  19   a.    
         [0028]    The second arm portion  20   c  of the release lever  20  is provided with a engaging recess  20   f  which is engageable with the mirror charge lever  21  to hold the mirror charge lever  21  in a lever holding position (shown by solid lines in FIG. 1), i.e., in a charge completion position. The mirror charge lever  21  is always interconnected with a quick-return mirror (hinged mirror)  41  (see FIGS. 7A and 7B), and is biased to rotate about a rotational shaft  21   c  in a direction to raise the quick-return mirror  41  to retract the quick-return mirror  41  from a photographing optical path behind a photographing lens, i.e. in a counterclockwise direction as viewed in FIGS. 7A and 7B, by the spring force of an extension spring  21   a . The quick-return mirror  41  rises by the spring force of the extension spring  21   a  to be positioned in a retracted position (raised position) as shown in FIG. 7B when the mirror charge lever  21  is in a position (retracted position) shown by dotted lines in FIG. 1. The quick-return mirror  41  is held in a viewing position shown in FIG. 7A, in which the quick-return mirror  41  is angled relative to a photographing optical axis  0  by an angle of approximately 45 degrees, when the mirror charge lever  21  is in a position (lever holding position) shown by solid lines in FIG. 1 with the extension spring  21   a  being expanded. As shown in FIGS. 7A and 7B, a focusing screen FS serving as an element of a viewfinder optical system of the SLR camera is positioned above the quick-return mirror  41 . When the quick-return mirror  41  is in the viewing position as shown in FIG. 7A, the light from the object which is passed through a photographing lens (not shown) of the SLR camera is reflected upwards by the quick-return mirror  41  to be incident on the focusing screen FS. The mirror charge lever  21  is provided with a stop arm portion  21   b  which is engageable with the engaging recess  20   f  of the release lever  20  to hold the mirror charge lever  21  in the lever holding position thereof.  
         [0029]    As shown in FIGS. 7A and 7B, the SLR camera driving system is provided with a shutter charge lever  42  which is pivoted about a rotational shaft  42   a  extending parallel to the rotational shaft  21   c  of the mirror charge lever  21 . The shutter charge lever  42  is provided with a first arm portion  42   b  and a second arm portion  42   c . The shutter charge lever  42  is provided on the first arm portion  42   b  with a cam slot  42   d  while the mirror charge lever  21  is provided with a follower roller  21   d  which is engaged in the cam slot  42   d  so that the shutter charge lever  42  rotates about the rotational shaft  42   a  by rotation of the mirror charge lever  21  by engagement of the follower roller  21   d  with the cam slot  42   d .  
         [0030]    The release lever  20  is biased to rotate clockwise with respect to FIG. 1 by the spring force of a torsion spring (release lever resetting spring)  20   e  (see FIG. 1) so that the stop arm portion  21   b  is engaged with the engaging recess  20   f  and so that the follower roller  20   d  is engaged with the release cam  19   a . The release lever  20  is provided with a bevel  20   g  which is engageable with the stop arm portion  21   b  of the mirror charge lever  21  when the mirror charge lever  21  rotates from a retracted position (shown by dotted lines in FIG. 1) to the lever holding position (shown by solid lines in FIG. 1). When the mirror charge lever  21  rotates from the retracted position to the lever holding position, a corresponding bevel of the stop arm portion  21   b  of the mirror charge lever  21  comes into contact with the bevel  20   g  and subsequently presses the bevel  20   g  so that the release lever  20  rotates counterclockwise as viewed in FIG. 1 against the spring force of the torsion spring  20   e.    
         [0031]    The SLR camera driving system is provided with a mirror-up switch  22  having a first leaf  22   a  and a second leaf  22   b . The first leaf  22   a  is supported by the release lever  20  to be movable together with the release lever  20 . The first leaf  22   a  comes into contact with the second leaf  22   b  to thereby detect that the quick-return mirror  41  is in the retracted position when the release lever  20  rotates counterclockwise, as viewed in FIG. 1, to disengage the stop arm portion  21   b  of the mirror charge lever  21  from the engaging recess  20   f.    
         [0032]    A mirror release operation in which the quick-return mirror  41  rises upon a shutter release will be hereinafter discussed. Upon the drive pinion  11  being rotated forward with a delay of a predetermined period of time after a shutter release signal (SWR shown in FIG. 8) is issued, the cam-incorporated gear  19  rotates clockwise as viewed in FIG. 1 by the forward rotation of the drive pinion  11  via the first and second idle gears  17  and  18  so that one of the pair of pressure cam edges  19   a   1  of the release cam  19   a  presses the follower roller  20   d  to rotate the release lever  20  counterclockwise as viewed in FIG. 1. The rotation of the release lever  20  in a counterclockwise direction causes the stop arm portion  21   b  to disengage from the engaging recess  20   f  so that the quick-return mirror  41  rises to retract from a photographing optical path by the spring force of the extension spring  21   a . Immediately after a period of time Td 1  elapses from the moment the shutter release signal SWR shown in FIG. 8 is issued, a leading-curtain holding magnet and a trailing-curtain holding magnet ESMg are energized to hold the leading and trailing curtains of the focal plane shutter in the respective charge completion positions. After the leading-curtain and trailing-curtain holding magnets ESMg are energized, the shutter charge lever  42  which mechanically holds the leading and trailing curtains of the focal plane shutter in the respective charge completion positions is retracted to a retracted position as shown in FIG. 7B to release the mechanical holding of the leading and trailing curtains of the focal plane shutter.  
         [0033]    Immediately after the follower roller  20   d  moves from the currently-engaged one of the pair of pressure cam edges  19   a   1  to one of the pair of cam edges  19   a   2  while the motor  10  is rotating forward, the release lever  20  rapidly rotates clockwise as viewed in FIG. 1 by the spring force of the torsion spring  20   e . This causes the first leaf  22   a  to be disengaged from the second leaf  22   b  to turn OFF the mirror-up switch  22 . Immediately after a signal is issued upon this change of the mirror-up switch  22  from ON to OFF, the motor  10  is stopped (a braking operation of the motor  10  is performed). Immediately after a period of time Td 2  elapses from the moment of the change of the mirror-up switch  22  from ON to OFF, the leading-curtain holding magnet (ESMg) is de-energized to cause the leading curtain to start moving to thereby start an exposure. Immediately after an exposure time calculated by an exposure control circuit (not shown) elapses from the commencement of the movement of the leading curtain, the trailing-curtain holding magnet (ESMg) is de-energized to cause the trailing curtain to start moving to complete the exposure.  
         [0034]    As shown in FIG. 2, the drive pinion  11  (motor  10 ) is driven reverse immediately after a lapse of a predetermined period of time (approximately a time Td 3  as indicated in FIG. 8) from the completion of an exposure. This reverse rotation of the drive pinion  11  causes the first swingable lever  15  to rotate in the same direction (counterclockwise as viewed in FIG. 2) as that of the third double gear  14  so that the first planet gear  16 , which is in mesh with the third double gear  14 , is engaged with a fourth gear  23  serving as a sun gear of a second planetary gear mechanism. The second planetary gear mechanism consists of the fourth gear  23  serving as a sun gear, and a second planet gear  25  which is in mesh with the fourth gear  23 . A second swingable lever  24  is pivoted at one end thereof about a rotational shaft  23   a  of the fourth gear  23 . The second planet gear  25  is rotatably fitted on a pin  25   a  which is fixed at a free end of the second swingable lever  24  to extend parallel to the rotational shaft  23   a . When the drive pinion  11  rotates reverse, the second planet gear  25  that is supported by the free end of the second swingable lever  24  is engaged with a cam-incorporated charge gear  26  which is rotatable at a fixed position about a rotational shaft  26   b . A charge cam  26   a  is formed integral with the charge gear  26 . The charge gear  26  rotates only counterclockwise as viewed in FIG. 2. The fourth gear  23 , the second swingable lever  24 , the second planet gear  25  and the cam-incorporated charge gear  26  constitute a mirror-shutter charge gear mechanism (charge mechanism) for the SLR camera driving system.  
         [0035]    The SLR camera driving system is provided in the vicinity of the charge gear  26  with a charge lever  27 . The charge lever  27  is pivoted about a rotational axis  27   a  extending parallel to the rotational shaft  26   b . The charge lever  27  is provided with a first arm portion  27   b  and a second arm portion  27   c . The charge lever  27  is provided at an approximate center of the second arm portion  27   c  with a follower roller  27   d  which is engaged with the charge cam  26   a.    
         [0036]    On the other hand, a free end of the first arm portion  27   b  extends up to a point to be engageable with the mirror charge lever  21 . The charge lever  27  is biased to rotate counterclockwise as viewed in FIG. 2 (i.e., in a direction to make the first arm portion  27   b  move away from the mirror charge lever  21 ) by the spring force of a strong torsion spring (charge lever resetting spring)  27   e  so that the follower roller  27   d  is engaged with the charge cam  26   a.    
         [0037]    The reverse rotation of the drive pinion (motor  10 )  11  performed after the completion of an exposure is transferred to the charge gear  26  via the first double gear  12 , the second double gear  13 , the third double gear  14 , the first planet gear  16 , the fourth gear  23  and the second planet gear  25 , so that the charge gear  26  rotates counterclockwise as viewed in FIG. 2. The counterclockwise rotation of the charge gear  26  causes the charge cam  26   a  to press the follower roller  27   d  against the spring force of the torsion spring  27   e  to rotate the charge lever  27  clockwise as viewed in FIG. 2. This clockwise rotation of the charge lever  27  causes the first arm portion  27   d  thereof to rotate the mirror charge lever  21  in a direction to return the quick-return mirror  41  down to the viewing position, which in turn causes the stop arm portion  21   b  of the mirror charge lever  21  to be engaged with the engaging recess  20   f  so that the mirror charge lever  21  and the quick-return mirror  41  are positioned in their respective charge-completion positions (see FIG. 3). In this state, the extension spring  21   a  is expanded to store force (load) therein for raising the quick-return mirror  41  from the viewing position to the retracted position. In addition, when the mirror charge lever  21  rotates in a direction to return the quick-return mirror  41  down to the viewing position, the follower roller  21   d  of the mirror charge lever  21  presses the inner edge of the cam slot  42   d  of the shutter charge lever  42  to rotate the shutter charge lever  42  clockwise as viewed in FIGS. 7A and 7B. This clockwise rotation of the shutter charge lever  42  causes the second arm portion  42   c  thereof to press a shutter drive lever  43  to charge the shutter.  
         [0038]    The SLR camera driving system is provided in the vicinity of the charge lever  27  with a mirror-down switch  28  having a first leaf  28   a  and a second leaf  28   b . The charge lever  27  is provided in the vicinity of the rotational shaft  27   a  thereof with a pressing tab  27   f  for pressing the first leaf  28   a . The pressing tab  27   f  presses the first leaf  28   a  to bring the first leaf  28   a  into contact with the second leaf  28   b  as shown in FIG. 3 to thereby detect that the quick-return mirror  41  is in the viewing position immediately before the charge lever  27  has been fully rotated clockwise as viewed in FIGS. 2 and 3 by the charge cam  26   a  when the charge lever  27  rotates in the same rotational direction.  
         [0039]    Even after the mirror-shutter charge operation is completed, the charge gear  26  continues to rotate counterclockwise (i.e., the drive pinion  11  (motor  10 ) is driven reversely) as viewed in FIG. 2 so that the charge lever  27  fully rotates clockwise and subsequently rotates counterclockwise as viewed in FIG. 2 and  3  by engagement of the charge cam  26   a  with the follower roller  27   d . This causes the first leaf  28   a  to be disengaged from the second leaf  28   b  as shown in FIG. 4, i.e., causes a state of the mirror-down switch  28  to change from ON to OFF. A signal is issued upon the change of the mirror-up switch  22  from ON to OFF. Upon this signal being issued, the completion of the mirror-shutter charge operation is detected. In the case where no film is loaded in the camera, the motor  10  is stopped upon the detection of the completion of the mirror-shutter charge operation.  
         [0040]    In the present embodiment of the SLR camera driving system, a film wind operation is performed by the aforementioned counterclockwise rotation of the charge gear  26  which continues even after the mirror charge operation is completed. The structure and operations of a film wind system (film advance system) of the SLR camera driving system will be hereinafter discussed with reference to FIGS. 2 through 4.  
         [0041]    The SLR camera driving system is provided with a reset lever  29  which is pivoted about a rotational shaft  29   a  extending parallel to the rotational shaft  26   b  and being independent of the rotational shaft  26   b  of the charge gear  26  so that the reset lever  29  and the charge lever  27  partially overlap each other as viewed in FIGS. 2 through 4. The reset lever  29  is provided with first and second arm portions  29   b  and  29   c  extending in opposite directions away from each other from the rotational shaft  29   a . A free end of the first arm portion  29   b  is positioned to face the mirror charge lever  21 . The reset lever  29  is biased to rotate clockwise as viewed in FIGS. 2 through 4 in a direction to bring the free end of the first arm portion  29   b  into contact with the mirror charge lever  21  by the spring force of a torsion spring (reset lever resetting spring)  29   d  (see FIGS. 2 and 3), and the clockwise rotatable end of the reset lever  29  is restricted by a stop (not shown). Namely, the rotational position of the reset lever  29  depends upon the rotational position of the charge lever  21 .  
         [0042]    The SLR camera driving system is provided with a lock lever  30  which is pivoted about the rotational shaft  26   b  of the charge gear  26 . The lock lever  30  is biased to rotate clockwise as viewed in FIGS. 2 through 4 by the spring force of the torsion spring  29   d.    
         [0043]    The SLR camera driving system is provided with a switch lever  31  pivoted about a rotational shaft  31   a  projecting from a free end of the second arm portion  27   c , the rotational shaft  31   a  extending parallel to the rotational shaft  27   a . In FIG. 3, the switch lever  31  is hatched for the purpose of clarity thereof. The switch lever  31  is biased to rotate clockwise as viewed in FIG. 3. The switch lever  31  abuts against an engaging tab  24   a  of the second swingable lever  24  when fully rotated clockwise. Namely, the clockwise rotatable end of the switch lever  31  is restricted by the engaging tab  24   a  of the second swingable lever  24 .  
         [0044]    To switch a motor drive system of the SLR driving system from a mirror-shutter charge system (mirror-shutter charge gear mechanism) of the SLR driving system to a film wind system (film-wind gear mechanism) of the SLR driving system by the aforementioned counterclockwise rotation of the charge gear  26  which continues rotating even after the mirror charge operation is completed, the charge lever  27 , the reset lever  29 , the lock lever  30  and the switch lever  31  are associated with each other in the following manner. Namely, the motor drive system is switched from the mirror-shutter charge system to the film wind system by moving the second swingable lever  24  from the position thereof shown in FIG. 3 to the position thereof shown in FIG. 4 and holding the second swingable lever  24  in the position shown in FIG. 4. In a state shown in FIG. 4, the second swingable lever  24  is locked with the engaging tab  24   a  of the second swingable lever  24  being engaged with a stop portion  30   a  of the lock lever  30  to prevent the second swingable lever  24  from rotating counterclockwise from the state shown in FIG. 4 to the state shown in FIG. 3. Namely, the motor drive system is prevented from being switched from the film wind system to the mirror-shutter charge system. The engaging tab  24   a  is bent at right angles to the plane of the second swingable lever  24 .  
         [0045]    As has been described above, the charge lever  27  rotates clockwise from the position shown in FIG. 2 to the position shown in FIG. 3 by counterclockwise rotation of the charge gear  26 . Further counterclockwise rotation of the charge gear  26  in a state shown in FIG. 3 causes the charge lever  27  to rotate counterclockwise this time by engagement of the charge cam  26   a  with the follower roller  27   d . This causes a pressing edge  31   d  of the switch lever  31 , which is pivoted about the rotational shaft  31   a  projecting from the second arm portion  27   c , to press the engaging tab  24   a  of the second swingable lever  24  to rotate the second swingable lever  24  clockwise from the state shown in FIG. 3 to the state shown in FIG. 4. When the second swingable lever  24  is rotated clockwise as shown in FIG. 4 by a movement of the lock lever  30 , the stop portion  30   a  of the lock lever  30  is engaged with a stop (not shown) fixed to a camera body to stand by at a position where the stop portion  30   a  is engageable with the engaging tab  24   a  to hold the engaging tab  24   a  of the second swingable lever  24  rotating clockwise. In this state, the second swingable lever  24  is locked in a position (film-wind-system engaging position) to be engaged with the film wind system by both the lock lever  30  and the switch lever  31 .  
         [0046]    Operations of the SLR camera driving system upon a subsequent shutter release will be discussed hereinafter. As described above with reference to FIGS. 1 through 4, upon a shutter release signal (SWR shown in FIG. 8) being issued, the mirror charge lever  21  and the quick-return mirror  41  move to the respective retracted positions by the spring force of the extension spring  21   a  since the release lever  20  rotates counterclockwise as viewed in FIG. 1 to cause the stop arm portion  21   b  to be disengaged from the engaging recess  20   f  after a shutter release signal (SWR shown in FIG. 8) is issued. Such movement of the mirror charge lever  21  to the retracted position by the spring force of the extension spring  21   a  causes the mirror charge lever  21  to contact the first arm portion  29   b  of the reset lever  29 , so that the reset lever  29  rotates counterclockwise as shown in FIG. 2. This causes an engaging tab  29   e  formed at one end (left end as viewed in FIGS. 2 through 4) of the reset lever  29  to contact a protrusion  31   e  of the switch lever  31  so that the switch lever  31  rotates counterclockwise as shown in FIG. 2. This counterclockwise rotation of the switch lever  31  causes the lock lever  30  to rotate in the same rotational direction via an engaging tab  30   b  of the lock lever  30  to unlock the second swingable lever  24 .  
         [0047]    The structure and operations of the film wind system (film-wind gear mechanism) of the SLR camera driving system will be further discussed with reference to FIG. 5. The charge gear  26  is not shown in FIG. 5 for the purpose of clarity.  
         [0048]    The SLR camera driving system is provided with a third planetary gear mechanism having a differential gear  33  serving as a sun gear, and a third planet gear  35  which is in mesh with the differential gear  33 . A third swingable lever  34  is pivoted at one end thereof about a rotational shaft  33   a  of the differential gear  33 . The third planet gear  35  is rotatably fitted on a pin which is fixed at a free end of the third swingable lever  34  to extend parallel to the rotational shaft  33   a . When the second swingable lever  24  is locked in the aforementioned film-wind-system engaging position by both the lock lever  30  and the switch lever  31 , the second planet gear  25  which is rotatably supported at the free end of the second swingable lever  24  is in mesh with an idle gear  32  to be connected with the differential gear  33 . The third planet gear  35  is engaged with a film take-up spool  36 . Accordingly, reverse rotation of the drive pinion  11  causes the film take-up spool  36  to rotate in a direction to wind up film if the film wind system is engaged with the motor drive system as shown in FIG. 5. The fourth gear  23 , the second swingable lever  24 , the second planet gear  25 , the idle gear  32 , the differential gear  33 , the third swingable lever  34 , the third planet gear  35  and the film take-up spool  36  constitute a film-wind gear mechanism of the SLR camera driving system.  
         [0049]    However, the differential gear  33  rotates in a direction to cause the third swingable lever  34  (the third planet gear  35 ) move away from the film take-up spool  36 . Accordingly, the SLR camera driving system is provided with a locking device for locking the third swingable lever  34  in a film wind position thereof. As described above with reference to FIG. 1, the release cam  19   a  and the lock cam  19   b  are formed on front and rear sides of the cam-incorporated gear  19 , respectively. As shown in FIG. 5, the lock cam  19   b  controls the rotational position of a biasing lever  37  for film winding which is pivoted about a rotational shaft  37   a . The biasing lever  37  is provided at a free end thereof with a roller  37   c . The rotational shaft  37   a  is independent of the cam-incorporated gear  19 . The lock cam  19   b  is symmetrical with respect to a rotational axis of the cam-incorporated gear  19 , and is engaged with a follower roller  37   b  of the biasing lever  37 . The lock cam  19   b  is composed of a pair of high cam edges  19   b   1  and a pair of low cam edges  19   b   2 . In a state where the follower roller  37   b  is engaged with one of the pair of high cam edges  19   b   1 , the roller  37   c  of the biasing lever  37  presses an engaging arm portion  34   a  of the third swingable member  34  to lock the third swingable member  34  in the film wind position. The cam-incorporated gear  19  has moved to the position thereof shown in FIG. 5 in a state before the shutter release signal is issued (initial state).  
         [0050]    Accordingly, reverse rotation of the drive pinion  11  causes the film take-up spool  36  to rotate in a direction to wind up a film, and the motor  10  is turned OFF to stop rotating the drive pinion  11  immediately after a predetermined number of pulses corresponding to a single frame of film has been counted (see FIG. 8). This film wind operation is performed each time a release signal is issued, and is repeatedly performed until the final frame has been taken.  
         [0051]    After the final frame has been taken, i.e., after film has been fully wound up around the film take-up spool  36 , no more pulses (signals) indicating the motion of film are generated. If it is detected that no pulses are generated for a predetermined period of time, the drive pinion  11  (motor  10 ) is rotated forward slightly for a very small period of time and subsequently stopped rotating to switch the motor drive system from the film wind system to a film rewind system (film-rewind gear mechanism) (see FIG. 9). This slight forward rotation of the drive pinion  11  causes the roller  37   c  of the biasing lever  37  to be disengaged from the engaging arm portion  34   a  of the third swingable member  34  to unlock the third swingable member  34 . Namely, the slight forward rotation of the drive pinion  11  causes the lock cam  19   b  of the cam-incorporated gear  19  to vary a point of engagement thereof with the follower roller  37   b  from one of the pair of high cam edges  19   b   1  to one of the pair of low cam edges  19   b   2 . This causes the roller  37   c  to be disengaged from the engaging arm portion  34   a , which in turn allows the third swingable lever  34  to be rotatable in a direction to disengage the third planet gear  35  from the film take-up spool  36  (see FIG. 6). As shown in FIG. 6, the SLR camera driving system is provided with a film wind/rewind switch  38  having a first leaf  38   a  and a second leaf  38   b . When the biasing lever  37  rotates counterclockwise from the state shown in FIG. 5 by the forward rotation of the drive pinion  11 , the first leaf  38   a  comes into contact with the second leaf  38   b  as shown in FIG. 6, to thereby detect that the motor drive system has been switched from the film wind system to the film rewind system. Upon this detection, the drive pinion  11  is driven reverse again (see FIG. 9).  
         [0052]    When the drive pinion  11  is driven reverse again, the differential gear  33  is rotated clockwise as viewed in FIG. 6 so that the third swingable lever  34  has fully rotated clockwise in a direction away from the film take-up spool  36 , the third planet gear  35  is engaged with an input gear of a film-rewind gear train  39 . An output gear (final gear) of the film-rewind gear train  39  is engaged with a film rewind rotating fork (not shown) in the film cassette chamber so that film rewind operation is performed by reverse rotation of the drive pinion  11  (motor  10 ). Subsequently, when it is determined that no pulses indicating the motion of film are generated, the drive pinion  11  (motor  10 ) is stopped. The fourth gear  23 , the second swingable lever  24 , the second planet gear  25 , the idle gear  32 , the differential gear  33 , the third swingable lever  34 , the third planet gear  35  and the film-rewind gear train  39  constitute a film-rewind gear mechanism of the SLR camera driving system. Similar to the film-wind operation, the second planet gear  25  is prevented from being engaged with the cam-incorporated charge gear  26 , via the engagement of the engaging tab  24   a  of the second swingable lever  24  and the stop portion  30   a  of the lock lever  30 . Namely, the motor drive system is prevented from being switched from the film rewind system to the mirror-shutter charge system.  
         [0053]    The differential gear  33  is composed of a pair of coaxial gears having the same shape and size which are rotatable relative to each other about the common rotational shaft  33   a  of the differential gear  33  within a predetermined angle of rotation. The pair of coaxial gears are biased to rotate in opposite rotational directions by the spring force of a torsion spring  33   b.    
         [0054]    As described above, the second planet gear  25  is forcefully brought into engagement with the idle gear  32 , which serves as a gear of the film wind system, by a counterclockwise rotation of the charge lever  27  by the spring force of the torsion spring  27   e  immediately after the above described operation of the mirror-shutter charge system by rotation of the second planet gear  25  is completed. During this operation, the film wind system applies a load to the second planet gear  25  to prevent the second plant gear  25  from being engaged with the idle gear  32  of the film wind system at the moment the second planet gear  25  starts to engage with the idle gear  32 . If the restoring force of the charge lever  27  by the spring force of the torsion spring  27   e  is greater than such a load which is applied to the second planet gear  25  by the film wind system, the second planet gear  25  will be securely engaged with idle gear  32  against the action on the second planet gear  25 . However, giving such a large restoring force to the charge lever  27  is impractical. Accordingly, besides the restoring force to the charge lever  27 , the present embodiment of the SLR camera driving system is provided with a special locking device which locks the second planet gear  25  upon completion of engagement of the second planet gear  25  with the idle gear  32  that serves as a gear of the film wind system. The third swingable lever  34 , the lock cam  19   b  and the biasing lever  37  are fundamental elements of the special locking device. In addition, the present embodiment of the SLR camera driving system is provided with the differential gear  33  to prevent load from being directly applied to the charge lever  27  by the film wind system during the time from the moment the second plant gear  25  starts being engaged with the idle gear  32  of the film wind system to the moment the second planet gear  25  is locked completely by the special locking device. The differential gear  33  relieves the aforementioned load by slipping between the pair of coaxial gears of the differential gear  33 .  
         [0055]    As can be understood from the foregoing, according to the present invention, a method and system for driving an SLR camera with a single motor are achieved, wherein a mirror release operation in which a quick-return mirror rises upon a shutter release is performed by a forward rotation of the motor, a film wind operation is performed by a reverse rotation of the motor, a film rewind operation is performed by a reverse rotation of the motor, and a mirror-shutter charge operation is performed by a reverse rotation of the motor.  
         [0056]    Obvious changes may be made in the specific embodiment of the present invention described herein, such modifications being within the spirit and scope of the invention claimed. It is indicated that all matter contained herein is illustrative and does not limit the scope of the present invention.