Abstract:
Objects of the present invention are to reduce rebounding of a sub-mirror and to prevent shifting of the mirror-down position. The present invention provides a mirror retention structure comprising, a main mirror retention frame that retains a main mirror, a sub-mirror retention frame that retains a sub-mirror and is axially supported at the main mirror retention frame, and a receiving pin that abuts against the sub-mirror retention frame and sets an angle of the sub-mirror at a mirror-down position, wherein the sub-mirror retention frame is provided with, a first abutting portion that touches against the receiving pin at the mirror-down position; and a second abutting portion, at a different position from the first abutting portion, that touches against the receiving pin at a position prior to the mirror-down position in a transition from a mirror-up position to the mirror-down position.

Description:
[0001]    The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2008-035185 filed on Feb. 15, 2008. The content of the application is incorporated herein by reference in its entirety. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a mirror retention structure and to a camera equipped therewith. 
         [0004]    2. Description of the Related Art 
         [0005]    Heretofore, there has been a mirror retention structure that is provided with: a main mirror retention frame that retains a main mirror; a sub-mirror retention frame that retains a sub-mirror and is axially supported at the main mirror retention frame; and an receiving pin that touches against the sub-mirror retention frame and sets an angle of the sub-mirror at a mirror-down position. In this conventional mirror retention structure, the angle of the sub-mirror is set by a portion of the sub-mirror retention frame abutting against the receiving pin when the sub-mirror comes into the mirror-down position (see, for example, Japanese Unexamined Patent Publication No. H9-203974). 
       SUMMARY OF THE INVENTION 
       [0006]    However, in the conventional mirror retention structure, when the sub-mirror comes to the mirror-down position, the sub-mirror retention frame strikes against the receiving pin and the sub-mirror rebounds. Further, if mirror-down is performed many times, the portion of the receiving pin that abuts against the sub-mirror retention frame is worn down and the mirror-down position of the sub-mirror is shifted. 
         [0007]    Objects of the present invention are to reduce rebounding of a sub-mirror and to prevent shifting of the mirror-down position. 
         [0008]    The present invention solves the above-described problem with the following solution. 
         [0009]    In order to achieve the object mentioned above, according to a first aspect of the present invention, there is provided a mirror retention structure comprising, a main mirror retention frame that retains a main mirror, a sub-mirror retention frame that retains a sub-mirror and is axially supported at the main mirror retention frame, and a receiving pin that abuts against the sub-mirror retention frame and sets an angle of the sub-mirror at a mirror-down position, wherein the sub-mirror retention frame is provided with, a first abutting portion that touches against the receiving pin at the mirror-down position, and a second abutting portion, at a different position from the first abutting portion, that touches against the receiving pin at a position prior to the mirror-down position in a transition from a mirror-up position to the mirror-down position. 
         [0010]    The first abutting portion may be formed at a surface parallel with the sub-mirror, and the second abutting portion is formed at a surface that is inclined to face an axis of rotation of the sub-mirror with respect to the main mirror retention frame. 
         [0011]    A portion of the receiving pin that abuts against the first abutting portion may be different from a portion of the receiving pin that abuts against the second abutting portion. 
         [0012]    At the mirror-down position, the first abutting portion may be disposed at a photography lens side relative to a position at which the sub-mirror is retained. 
         [0013]    The receiving pin may be an eccentric pin. 
         [0014]    In order to achieve the object mentioned above, according to a second aspect of the present invention, there is provided a camera comprising the mirror retention structure according to the first aspect of the present invention. 
         [0015]    The constitutions described hereabove may be suitably modified, and at least portions thereof may be substituted with other constituents. 
         [0016]    According to the present invention, rebounding of a sub-mirror may be reduced and shifting of a mirror-down position prevented. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    In the drawings attached, 
           [0018]      FIG. 1  is a sectional view showing a camera incorporating an embodiment of the mirror retention structure of the present invention; 
           [0019]      FIG. 2  is a side view showing a mirror-down position of a mirror retention mechanism portion; 
           [0020]      FIG. 3  is a side view showing a position prior to the mirror-down position of the mirror retention mechanism portion; and 
           [0021]      FIG. 4A  and  FIG. 4B  are side views showing respective contact points of a sub-mirror retention frame and a receiving pin. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0022]    Herebelow, a preferred embodiment of the present invention will be described with reference to the attached drawings and suchlike.  FIG. 1  is a sectional view of a camera  10  of the present embodiment. In  FIG. 1 , an xyz orthogonal coordinate system is established for ease of description and understanding. In this coordinate system, for a position of the camera when a photographer is keeping the optical axis A horizontal and photographing a landscape orientation image (hereinafter referred to as a usual photography position), a direction to leftward from the photographer&#39;s point of view is the +x direction. The direction to upward in the usual photography position is the +y position, and the direction toward the subject in the usual photography position is the +z position. 
         [0023]    The camera  10  of the present embodiment is a digital single lens reflex camera. The camera  10  includes a frame main body portion  11 , an image display portion  12 , a mount portion  20 , a mirror retention mechanism portion  30 , a viewfinder portion  40 , a range sensor portion  50 , a shutter portion  60  and an imaging portion  70 . 
         [0024]    The frame main body portion  11  is a main frame of the camera  10 , to which the respective portions of the camera  10  are fixed. The image display portion  12  is provided at a rear portion of the camera  10 . The image display portion  12  is a liquid crystal display that shows subjects photographed by the imaging portion  70 , and information relating to operations, photographed subjects and so forth. The mount portion  20  is a portion at which an unillustrated photography lens is removably mounted. The photography lens is a lens unit at which object light is incident. The incident object light is emitted to the mirror retention mechanism portion  30 . The photography lens is interchangeable in accordance with photography requirements. A zoom-type lens unit that magnifies and reduces subject images, a single point focus-type lens unit, or the like may be employed. 
         [0025]    The viewfinder portion  40  includes a viewfinder screen  41 , a Dach pentaprism  42  and an eyepiece portion  43 . The viewfinder screen  41  is disposed above the mirror retention mechanism portion  30 , and is a screen for inputting and focusing object light that is reflected thereat when the mirror retention mechanism portion  30  is in a viewing state. The Dach pentaprism  42  is disposed above the viewfinder screen  41 , and is a polygonal prism that emits the object light focused by the viewfinder screen  41  toward the eyepiece portion  43 . The eyepiece portion  43  is an eyepiece optical system disposed at a position on which the object light emitted from the Dach pentaprism  42  is incident. 
         [0026]    The range sensor portion  50  is a sensor at which object light reflected by the mirror retention mechanism portion  30  is incident. The range sensor portion  50  is provided for adjusting the focusing point to the subject of the camera  10 . The shutter portion  60  is provided with a plural number of unillustrated shutter blade units. The shutter portion  60  opens and closes the shutter blade units in accordance with photography instructions from an unillustrated release switch or the like, and causes object light to be incident on the imaging portion  70 . 
         [0027]    The imaging portion  70  is disposed at a position at which object light that has passed through the shutter portion  60  is incident. The imaging portion  70  is provided with a low pass filter  71  and an imaging device  72 . The imaging device  72  is a CCD (Charge-Coupled Device) which is disposed behind the low pass filter  71 . The imaging device  72  is exposed to the object light that is incident thereon via the low pass filter  71 , converts the object light to electronic image signals, and outputs the image signals to an unillustrated image processing section. The imaging device  72  is not limited to being a CCD. For example, a CMOS (Complementary Metal Oxide Semiconductor) device may be employed. 
         [0028]    The mirror retention mechanism portion  30  is a mechanism that includes a main mirror  1  and a sub-mirror  3 . The mirror retention mechanism portion  30  is disposed at a position at which object light, which is emitted from the rear portion of the photography lens disposed at the mount portion  20 , is incident. The mirror retention mechanism portion  30  causes the object light to be incident on the viewfinder portion  40 , the range sensor portion  50 , the shutter portion  60  and the imaging portion  70  as appropriate. 
         [0029]    The mirror retention mechanism portion  30  is provided with a main mirror retention frame  2  which retains the main mirror  1  and a sub-mirror retention frame  4  which retains the sub-mirror  3 . The sub-mirror retention frame  4  is disposed to the rear side of the main mirror retention frame  2  along the optical axis A. Thus, the sub-mirror  3  is disposed at the rear side of the main mirror  1 . The main mirror  1  is a reflection mirror that reflects object light toward the viewfinder portion  40 . A semi-transmissive mirror (not shown) which transmits light is provided at a portion of the reflection surface of the main mirror  1 . At the semi-transmissive mirror, the object light is party not reflected but transmitted to the rear of the main mirror  1 , and the transmitted object light is incident on the sub-mirror  3  disposed to the rear. The sub-mirror  3  is a reflection mirror that reflects the object light transmitted through the semi-transmissive mirror of the main mirror  1  toward the range sensor portion  50 . 
         [0030]      FIG. 1  shows a case in which the mirror retention mechanism portion  30  is in the mirror-down state. The main mirror  1  reflects the object light to the viewfinder portion  40 , enabling viewing of the subject at the viewfinder portion  40 . At this time, the sub-mirror  3  is disposed at the rear side of the main-mirror  1 , spaced apart from the main mirror  1 , and reflects a portion of the object light toward the range sensor portion  50 . The range sensor portion  50  adjusts the focusing point to the subject in accordance with this object light. When the unillustrated release switch is pressed or suchlike and photography is executed, the main mirror retention frame  2  turns in the clockwise direction of  FIG. 1  and moves toward the viewfinder portion  40 . At the same time, the sub-mirror retention frame  4  turns in the clockwise direction and moves so as to lie flat with the main mirror retention frame  2 . Thus, the mirror retention mechanism portion  30  is withdrawn from the optical axis A and goes into the mirror-up state. The object light is incident on the shutter portion  60  and imaging portion  70  disposed to the rear of the mirror retention mechanism portion  30 . In this condition, photography can be executed. When photography ends, the main mirror retention frame  2  turns in the anticlockwise direction, and the sub-mirror retention frame  4  turns in the anticlockwise direction away from the main mirror retention frame  2 . Thus, the mirror retention mechanism portion  30  returns to the mirror-down state of  FIG. 1 . 
         [0031]    As described above, it is necessary for the main mirror  1  and the sub-mirror  3  to turn between the mirror-up state and the mirror-down state. The main mirror retention frame  2  is turnably mounted at a main support shaft  31 , while the sub-mirror retention frame  4  is turnably mounted at a sub support shaft  32 . The main support shaft  31  is mounted at the frame main body portion  11 , and turnably supports an upper portion of the main mirror retention frame  2 . The sub support shaft  32  is mounted at a central portion of the main mirror retention frame  2 , and turnably supports an upper portion of the sub-mirror retention frame  4 . The turning in the clockwise direction of the main mirror retention frame  2  is implemented by an unillustrated motor, and the turning in the clockwise direction of the sub-mirror retention frame  4  is also implemented by a motor. 
         [0032]      FIG. 2  shows the mirror retention mechanism portion  30  in the mirror-down state, and  FIG. 3  shows a state prior to transition into the mirror-down state. The turning in the anticlockwise direction to return from the mirror-up state to the mirror-down state is implemented by springs. Accordingly, an unillustrated return spring, constituted by a coil spring or the like, is provided at the main support shaft  31  and urges the main mirror retention frame  2  in the anticlockwise direction. An unillustrated return spring, such as a toggle spring or the like, is provided between the main mirror retention frame  2  and the sub-mirror retention frame  4 , and urges the sub-mirror retention frame  4  in the anticlockwise direction. 
         [0033]    At the mirror-down position, it is necessary for the main mirror  1  and the sub-mirror  3  to be stopped at predetermined angles. Accordingly, a stopper pin  7  and a receiving pin  6  are provided at the frame main body portion  11 . The stopper pin  7  sets the angle of the main mirror retention frame  2  at the mirror-down position, and thus sets the angle of the main mirror  1 , by the main mirror retention frame  2  abutting against the stopper pin  7 . The receiving pin  6  sets the angle of the sub-mirror retention frame  4  at the mirror-down position, and thus sets the angle of the sub-mirror  3 , by the sub-mirror retention frame  4  abutting against the receiving pin  6 . 
         [0034]    As shown in  FIG. 2  and  FIG. 3 , a first abutting portion  4   a  and a second abutting portion  4   b  are formed at the sub-mirror retention frame  4 . The first abutting portion  4   a  is a surface that touches against the receiving pin  6  at the mirror-down position. The second abutting portion  4   b  is a surface that touches against the receiving pin  6  prior to transition into the mirror-down position. The abutting portions  4   a  and  4   b  are formed by a recess portion  33  being formed at a rear face of the sub-mirror retention frame  4  and a flat surface being provided at a bottom face of the recess portion  33 . The recess portion  33  is a hollow that opens to the receiving pin  6  side. When the sub-mirror retention frame  4  turns in the clockwise direction, the receiving pin  6  can relatively approach the sub-mirror retention frame  4  through the opening portion of the recess portion  33 . 
         [0035]    The first abutting portion  4   a  is formed on a surface parallel with the sub-mirror  3 . The first abutting portion  4   a  is disposed at the photography lens side (the mount portion  20  side) relative to the position (not shown) at which the sub-mirror  3  is retained by the sub-mirror retention frame  4 . The second abutting portion  4   b  is formed integrally with the first abutting portion  4   a,  on a surface that is inclined, relative to the sub-mirror  3 , to a direction toward the center of rotation of the sub-mirror  3  (i.e., the sub support shaft  32 ). 
         [0036]    Next, operation of the mirror retention mechanism portion  30  of the embodiment of the present invention is described. During the transition to the mirror-down state, the main mirror retention frame  2  is turned in the anticlockwise direction by the return spring thereof, and the sub-mirror retention frame  4  is turned in the anticlockwise direction by the return spring thereof. In accordance with the turning of the sub-mirror retention frame  4 , the receiving pin  6  abuts against the second abutting portion  4   b  as shown in  FIG. 3 . As the main mirror retention frame  2  turns further in the anticlockwise direction, the receiving pin  6  slides along the inclined face of the second abutting portion  4   b.  Then, when the main mirror retention frame  2  abuts against the stopper pin  7 , the receiving pin  6  abuts against the first abutting portion  4   a,  and the turning of the main mirror retention frame  2  and the sub-mirror retention frame  4  stops. The angle of the main mirror  1  retained by the main mirror retention frame  2  and the angle of the sub-mirror  3  retained by the sub-mirror retention frame  4  are set by this abutting. 
         [0037]    Thus, according to the present embodiment, the following effects are provided. 
         [0038]    (1) The first abutting portion  4   a  and second abutting portion  4   b  formed at the sub-mirror retention frame  4  are planar structures rather than three-dimensional structures. Therefore, the structure is simple, fabrication is easy, accurate formation is possible, and formation in a small amount of space is possible. 
         [0039]    (2) The sub-mirror retention frame  4  is stopped by the second abutting portion  4   b  abutting against the receiving pin  6  and then the first abutting portion  4   a  abutting against the receiving pin  6 . With these two stages of abutting, an impact caused by the abutting against the receiving pin  6  can be reduced, and durability is improved. 
         [0040]    (3) Because the second abutting portion  4   b  of the sub-mirror retention frame  4  is an inclined surface, a rebounding force when the second abutting portion  4   b  abuts against the receiving pin  6  is reduced. Therefore, an amount of rebound of the sub-mirror retention frame  4  can be reduced. 
         [0041]    (4)  FIG. 4A  shows positions of points at which the sub-mirror retention frame  4  comes into contact with the receiving pin  6 . The first abutting portion  4   a  touches against the receiving pin  6  at a point  41 , and the second abutting portion  4   b  touches against the receiving pin  6  at a point  42 .  FIG. 4B  shows points at which the receiving pin  6  comes into contact with the sub-mirror retention frame  4 . A point  61  touches against the first abutting portion  4   a,  and a point  62 , at a location separated from the point  61 , touches against the second abutting portion  4   b.  Thus, the receiving pin  6  touches the sub-mirror retention frame  4  at two locations, the points  61  and  62 . Inertial force is almost completely absorbed by the impact when the second abutting portion  4   b  first touches against the receiving pin  6 . Thereafter, at the mirror-down position, the first abutting portion  4   a  touches against the receiving pin  6  and the sub-mirror retention frame  4  is stopped. Therefore, an impact between the point  41  and the point  61  is small, and amounts of wear are small. As a result, even with a large number of photography cycles, variation in the angle of the sub-mirror retention frame  4 , and thus of the sub-mirror  3 , can be kept small. 
         [0042]    (5) Because the first abutting portion  4   a  which sets the mirror-down position of the sub-mirror  3  is a surface that is parallel with the sub-mirror  3 , it is easy to adjust the stopping angle of the sub-mirror  3 . 
         [0043]    (6) Because the first abutting portion  4   a  is disposed at the photography lens side relative to the retention position of the sub-mirror  3 , other members may be disposed with room to spare. That is, because the first abutting portion  4   a  is disposed at the photography lens side, space can be assured even with a constitution in which the gap between the mirror retention mechanism portion  30  and the imaging portion  70  is reduced by provision for dust reduction and the like. 
       [Modified Form] 
       [0044]    The present invention may be modified and altered in various ways as follows without being limited to the above-described embodiments and such modifications and alterations are also within the technical scope of the present invention. 
         [0045]    (1) The receiving pin  6  may be an eccentric pin. If the receiving pin  6  is an eccentric pin, it may be turned and the position thereof finely adjusted. Thus, the position of the sub-mirror  3  may be adjusted for individual cameras. 
         [0046]    (2) The receiving pin  6  may be formed as a pin with some degree of thickness. If the receiving pin  6  is a thick pin, strength with respect to the abutting of the sub-mirror retention frame  4  may be increased. Moreover, the receiving pin  6  may abut with the first abutting portion  4   a  and the second abutting portion  4   b  in states close to surface contact. Consequently, impacts may be more greatly absorbed. 
         [0047]    The embodiment and modified forms may be suitably combined and used, but detailed descriptions are not given herein. The present invention is not to be limited by the embodiments described hereabove.