Patent Publication Number: US-2007104480-A1

Title: Single-lens reflex camera

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
      This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2005-320512, filed on Nov. 4, 2005, the entire contents of which are incorporated herein by reference.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a single-lens reflex camera with a built-in focal-plane shutter.  
      2. Description of the Related Art  
      The single-lens reflex camera typically incorporates a so-called focal-plane shutter. In the focal-plane shutter, a driving force generated by a motor or human power is transmitted to a mechanism having a pair of shutter blades, which form front and rear curtains respectively, to charge springs, and magnets (electromagnet) keep the shutter blades in charged condition. Then, when a shutter button is pressed, a release signal is generated to de-energize each magnet at predetermined timing so that each of the pair of shutter blades is released from its charged state to travel individually under the force of each spring, thereby obtaining a predetermined exposure.  
      Referring to FIGS.  5  to  7 , the structure of a conventional single-lens reflex camera is schematically described below.  FIG. 5  is a transversal-sectional view showing the layout of each of mechanisms as viewed from the upper side of the single-lens reflex camera.  FIG. 6  is an exploded perspective view of the single-lens reflex camera.  FIG. 7  is a schematic exploded perspective view of a charge device.  
      As shown in  FIG. 5 , an imaging medium  14  such as a CCD, a low-pass filter  16 , a shutter device (focal-plane shutter)  18 , a mirror box device  20 , and a camera front plate  22  are arranged in this order in front of an electric substrate  12  along the optical axis O of a light beam from a subject inside a camera body  11  of a single-lens reflex camera  10 . A lens unit (not shown) is removably mounted on the camera body  11  through a body mount  22   a  of the front plate  22 . Further, a charge device  19  is arranged at the side of the mirror box device  20 .  
      As shown in  FIGS. 6 and 7  together with  FIG. 5 , the shutter device  18  has a box-shaped shutter control part  18   a  and a support plate (shutter base plate)  18   b  supporting the shutter control part  18   a . The shutter control part  18   a  includes a pair of shutter blades  18   a   1  fitted in and held by the support plate  18   b  to function as front and rear curtains respectively, magnets (not shown) typically electromagnets, and charge springs (not shown). The shutter blade pair  18   a   1  is fitted in and held by the support plate  18   b.    
      The charge device  19  has a motor  19   a  and a driving-force transmission mechanism  19   b  including a reduction gear train. The driving force of the motor  19   a  is slowed down through the driving-force transmission mechanism  19   b  and transmitted to the shutter control part  18   a  of the shutter device  18  to charge the charge springs.  
      The shutter control part  18   a  of the shutter device  18  is disposed on one lateral side (left-hand side in  FIG. 5 ) of the support plate  18   b  and located in front of the support plate  18   b  in the direction of the optical axis O. On the other hand, the charge device  19  is arranged at the side of the mirror box device  20  to occupy part of the space in front and side of the shutter device  18  (specifically the shutter control part  18   a ). A portion of the charge device  19  also occupies the space below the bottom of the shutter device  18  (specifically the shutter control part  18   a ).  
      Thus, the shutter control part  18   a  of the shutter device  18  and the charge device  19  are both located in front of the support plate  18   b  in the direction of the optical axis O.  
      In general, the shutter control part  18   a  is arranged transversely not to interfere with the front plate  22 . The charge device  19  is arranged in a manner to occupy the space around the front, one side, and bottom of the shutter control part  18   a , and its motor  19   a  is placed near the side of the shutter control part  18   a . This arrangement means that the charge device  19  extends out farther laterally than the shutter control part  18   a.    
      In other words, when the length of the shutter control part  18   a  from the optical axis O to its outer edge (equal to the length of the front plate  22  from the optical axis O to its outer edge) is set to A, the length A′ of the charge device  19  from the optical axis O to its outer edge becomes A+ΔA. This means that the charge device  19  extends laterally out by ΔA from the shutter control part  18   a.    
      The structure of the charge device  19  is known. Briefly, as shown in  FIG. 7 , the driving force of the motor  19   a  is transmitted from a pinion gear a of the motor  19   a  to a charge gear c through the reduction gear train b that slows the rotation speed down. A contact roller e 1  of a charge lever e is in contact with a cam surface d 1  of a charge cam d on the upper surface of the charge gear c. The charge lever e is swingable about an axis Oe as a pivot point. When the charge gear c rotates in one direction (X direction in  FIG. 7 ) by the driving force of the motor  19   a , the charge lever e swings about the axis Oe in the Y direction in  FIG. 7  so that a pressure roller e 2  provided at the tip of the charge lever e will push a charged lever f of the shutter control part  18   a . When the charged lever f is pushed, the charge springs (not shown) of the shutter control part  18   a  are charged with the driving force of the motor  19   a.    
      Thus, the driving-force transmission mechanism  19   b  includes the pinion gear a of the motor  19   a , the reduction gear train b, the charge gear c, the charge cam d, the charge lever e, and the charged lever f.  
      When the shutter button is pressed, each of the magnets is de-energized at predetermined timing to release each of the pair of shutter blades  18   a   1  from being retained in a closed position so that they will travel individually and sequentially under the force of each of the charge springs to obtain a predetermined exposure.  
      Thus, in the conventional single-lens reflex camera, the shutter control part  18   a  is arranged on one lateral side of the support plate  18   b . On the other hand, the charge device  19  is arranged at the side of the mirror box device  20  in a manner to occupy the space around the front, one side, and bottom of the shutter control part  18   a . In other words, the shutter control part  18   a  of the shutter device  18  and the charge device  19  are both located in front of the support plate  18   b  in the direction of the optical axis O. Further, a portion of the charge device  19  extends laterally out over the shutter control part  18   a . As discussed above, in the conventional single-lens reflex camera, the shutter control part  18   a  of the shutter device  18  and the charge device  19  are both located in front of the support plate  18   b  in the direction of the optical axis O. Further, a portion of the charge device  19  extends laterally out over the shutter control part  18   a.    
     BRIEF SUMMARY OF THE INVENTION  
      The single-lens reflex camera of the present invention features its shutter device. The shutter device includes a support plate having an opening through which an imaging medium is exposed to a light beam from a subject, a shutter blade for opening and closing the shutter (opening), and a shutter control part for driving open and close movements of the shutter blade, in which the shutter control part is located behind the support plate in the direction of the optical axis of the subject light beam.  
      As an exemplary structure of the present invention, a single-lens reflex camera comprises an imaging medium and a shutter device arranged in front of the imaging medium along the optical axis of the imaging medium, wherein the shutter device comprises a support plate having an opening through which the imaging medium is exposed to a light beam from a subject, a pair of shutter blades which travel vertically with respect to the optical axis of the subject light beam to control the amount of exposure to the imaging medium, and a shutter control part as a drive part for driving the pair of shutter blades, which is located at the side of the opening and behind the support plate in the direction of the optical axis.  
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
      These and other features, aspects, and advantages of the apparatus and methods of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings where:  
       FIG. 1  is a transversal-sectional view showing the layout of each of mechanisms as viewed from the upper side of a single-lens reflex camera according to a first embodiment of the present invention;  
       FIG. 2  is an exploded perspective view of the single-lens reflex camera of the present invention;  
       FIG. 3  is a schematic exploded perspective view of a charge device for a shutter for a shutter according to the present invention;  
       FIG. 4  is a transversal-sectional view showing the layout of each of mechanisms as viewed from the upper side of a single-lens reflex camera according to a second embodiment of the present invention;  
       FIG. 5  is a transversal-sectional view showing the layout of each of mechanisms as viewed from the upper side of a conventional single-lens reflex camera;  
       FIG. 6  is an exploded perspective view of the conventional single-lens reflex camera; and  
       FIG. 7  is a schematic exploded perspective view of a charge device for a conventional shutter.  
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Preferred embodiments of the invention are described below with reference to the accompanying drawings.  
       FIG. 1  is a transversal-sectional view showing the layout of each of mechanisms as viewed from the upper side of a single-lens reflex camera according to a first embodiment of the present invention.  FIG. 2  is an exploded perspective view of the single-lens reflex camera.  FIG. 3  is a schematic exploded perspective view of a charge device.  
      In the embodiment, a shutter control part is disposed on one lateral side of a support plate and located behind the support plate in the direction of an optical axis. Since the shutter control part is located behind the support plate in the direction of the optical axis, there is no need to provide space for the shutter control part in front of the support plate in the direction of the optical axis. Therefore, the front space can be used effectively for other purposes.  
      For example, part or entire of the charge device for charging the shutter control part can be arranged in the space. In this case, the charge device can be arranged without extending farther out from the side of the shutter control part. This can improve flexibility in designing the camera. In particular, if the charge device has a motor, the motor can be placed closer to the optical axis. This can shorten the length of the charge device from the optical axis to its outer edge, and hence is effective in downsizing the single-lens reflex camera.  
      The single-lens reflex camera of the present embodiment is basically the same in terms of components as the conventional single-lens reflex camera shown in FIGS.  4  to  6 , except merely for a small portion of the layout. Therefore, in the following description, the same reference numerals are used to designate the same components as those in the conventional single-lens reflex camera.  
      As shown in  FIG. 1 , an imaging medium  14  such as a CCD, a low-pass filter  16 , a shutter device (focal-plane shutter)  18 , a mirror box device  20 , and a front plate  22  are arranged in this order in front of an electric substrate  12  along the optical axis O of a light beam from a subject inside a camera body  11  of a single-lens reflex camera  1 . A charge device  19  is arranged at the side of the mirror box device  20 . Further, a lens unit (not shown) is removably mounted on the camera body  11  through a body mount  22   a  of the front plate  22 .  
      The shutter device  18  has a box-shaped shutter control part  18   a  and a support plate (shutter base plate)  18   b  supporting the shutter control part  18   a . The shutter control part  18   a  includes a pair of shutter blades  18   a   1  fitted in and held by the support plate  18   b  to function as front and rear curtains respectively, magnets (not shown) typically electromagnets, and charge springs (not shown). The shutter blade pair  18   a   1  is fitted in and held by the support plate  18   b.    
      On the other hand, the charge device  19  has a motor  19   a  and a driving-force transmission mechanism  19   b  including a reduction gear train. The driving force of the motor  19   a  is slowed down through the driving-force transmission mechanism  19   b  and transmitted to the shutter control part  18   a  of the shutter device  18  to charge the charge springs.  
      The shutter control part  18   a  is disposed on one lateral side of the support plate  18   b  and located behind the support plate  18   b  in the direction of the optical axis O. This location corresponds to one lateral side (left-hand side in  FIG. 1 ) of the shutter device  18 . On the other hand, one portion  19 - 1  of the charge device  19  is arranged at the side of the mirror box device  20  and in front of the shutter control part  18   a , while the other portion  19 - 2  extends below the bottom of the shutter control part  18   a  across the support plate  18   b . In other words, the charge device  19  extends from a position forward of the support plate  18   b  in the direction of the optical axis to a position below the bottom the shutter control part  18   a.    
      Thus, the shutter control part  18   a  is mounted on one lateral side of the support plate  18   b  of the shutter device  18  and located behind the support plate  18   b  in the direction of the optical axis, while the charge device  19  is arranged to extend from a position forward of the support plate  18   b  in the direction of the optical axis to a position below the bottom of the shutter control part  18   a . It means that the shutter control part  18   a  and the charge device  19  are arranged in front of and behind the support plate  18   b  in the direction of the optical axis in a divided manner.  
      Since the space at the side of and behind the support plate  18   b  in the direction of the optical axis, on which the shutter control part  18   a  is arranged in the embodiment, is unused in the conventional structure as shown in  FIG. 5 , the shutter control part  18   a  can be arranged in this space without the need for additional space. On the other hand, the charge device  19  is arranged such that one portion  19 - 1  of the charge device  19  is positioned instead of the shutter control part  18   a  in  FIG. 5  in front of the shutter control part  18   a  and at the side of the mirror box device  20 , where the shutter control part  18   a  is arranged in the conventional structure, while the other portion  19 - 2  extends below the bottom of the shutter control part  18   a  across the support plate  18   b.    
      In the embodiment, when the length of the charge device  19  from the optical axis O to its outer edge is set to B, the motor  19   a  of the charge device  19  is positioned within the length B, not at the side of the shutter control part  18   a.    
      In this layout, the length B of the charge device  19  from the optical axis O to its outer edge is obviously shorter than the length A′ in the conventional structure in  FIG. 5 . In  FIG. 1 , the outline shape of the conventional camera body is indicated by an alternate long and short dashed line. It is apparent from  FIG. 1  that the horizontal dimension of the camera body  11  in the embodiment is shorter by ΔB than that in the conventional structure in  FIG. 5  (note that the area of the charge device  19  is the same between  FIGS. 1 and 5 ).  
      Thus, according to the present invention, the charge device  19  can be arranged without extending farther out from the side of the shutter control part  18   a . This can improve flexibility in designing the camera. In addition, the horizontal dimension of the camera body  11  is smaller than that in the conventional structure, allowing downsizing of the single-lens reflex camera  1 .  
      Note that, although the location of the motor  19   a  is different from that in the conventional structure, the basic structure of the charge device  19  is the same as that in the conventional structure. As shown in  FIG. 3 , the driving-force transmission mechanism  19   b  of the charge device  19  includes a pinion gear a of the motor  19   a , a reduction gear train b, a charge gear c, a charge cam d, a charge lever e, and a charged lever f. The driving force of the motor  19   a  is transmitted from the pinion gear a of the motor  19   a  to the charge gear c while being slowed down through the reduction gear train b. A contact roller e 1  of the charge lever e is in contact with a cam surface d 1  of the charge cam d on the upper surface of the charge gear c. The charge lever e is swingable about an axis Oe as a pivot point. The charge lever e is arranged such that its pressure roller e 2  is located behind the shutter support plate  18   b  in the direction of the optical axis, and the axis Oe of the pivot point is located in front of the shutter support plate  18   b  in the direction of the optical axis. Then, when the charge gear c is rotates in one direction (X direction in  FIG. 3 ) by the driving force of the motor  19   a , the charge lever e swings about the axis Oe in the horizontal direction of the camera (Y direction in  FIG. 3 ) so that the pressure roller e 2  formed at the tip of the charge lever e will push the charged lever f of the shutter control part  18   a . When the charged lever f is pushed, the charge springs of the shutter control part  18   a  are charged with the driving force of the motor  19   a . Then, when a shutter button is pressed, each magnet is de-energized at predetermined timing to release each of the pair of shutter blades  18   a   1  from being retained in a closed position so that they will travel individually and sequentially under the force of each of the charge springs to obtain a predetermined exposure.  
      The mirror box device  20  has a reflecting mirror  20   a  positioned in front of the shutter device  18  in the direction of the optical axis. The reflecting mirror  20   a  can provide both an optical path (viewing optical path) reflecting a light beam from a subject to guide it into an observation optical system including a prism and the like provided above the reflecting mirror  20   a , and an optical path (imaging optical path) transmitting the subject light beam to guide it into an image pickup device  14  located behind the reflecting mirror  20   a  in the direction of the optical axis.  
      A half mirror or rotatable reflecting mirror can be used as the reflecting mirror  20   a . When a rotatable reflecting mirror is used, the reflecting mirror  20   a  is arranged inside the mirror box device  20  in such a manner to be rotatable between a viewing position at which it guides the subject light beam into the observation optical system to form the viewing optical path and a retracted position at which it flips up from the viewing position and guides the subject light beam into the image pickup device  14  to provide the imaging optical path.  
       FIG. 4  is a transversal-sectional view showing a second embodiment which is different in layout from the first embodiment. In this embodiment, the different point is that a shutter control part  18 ′ a  is arranged laterally opposite to that in the aforementioned embodiment, that is, when a photographer holds the camera to take a picture, the shutter control part  18 ′ a  is positioned on his or her left-hand side. The shutter control part  18 ′ a  is arranged behind a support plate  18 ′ b  in the direction of the optical axis and opposite to a camera grip  11 ′ a  of the camera body  11 . Therefore, a charge device  19 ′ for charging the springs to drive the shutter blades included in the shutter control part  18 ′ a  and a motor  19 ′ a  for charging the shutter are also arranged opposite to the camera grip  11 ′ a  of the camera body  11 .  
      As described above, according to the layouts in the aforementioned embodiments of the present invention, the charge device can be arranged without extending farther out from the side of shutter control part. This can reduce the horizontal dimension of the camera body, and hence downsize the single-lens reflex camera.  
      The present invention has a wide applicability to single-lens reflex cameras such as digital cameras and video cameras or camcorders.  
      While there has been shown and described what are considered to be preferred embodiments of the invention, it will, of course, be understood that various modifications and changes in form or detail could readily be made without departing from the spirit of the invention. It is therefore intended that the invention not be limited to the exact forms described and illustrated, but constructed to cover all modifications that may fall within the scope of the appended claims.