Abstract:
A diaphragm device of the present invention includes: a base plate having an aperture portion; a blade being supported by the base plate to be able to open and close the aperture portion; a drive ring being formed so as to surround the perimeter of the aperture portion, the drive ring being configured to drive the blade to open and close; a supporting pin pivotably supporting the blade being provided on the drive ring; and an engaging pin engaging with the blade and causing the blade to open or close in conjunction with the drive ring and the supporting pin, the engaging pin being provided on the base plate on an inner side of the supporting pin in the radial direction of the drive ring.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2014-233687 filed on Nov. 18, 2014, the entire content of which is hereby incorporated by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a diaphragm device and an optical instrument. 
         [0004]    2. Description of the Related Art 
         [0005]    For example, in optical instruments such as digital cameras and still cameras there is provided a diaphragm device that adjusts the amount of light that passes through the lens. A diaphragm device is provided with a base plate having an aperture portion, a plurality of diaphragm blades that are supported such that they are able to open and close the aperture portion, and a drive ring that is formed so as to surround the periphery of the aperture portion and that causes the plurality of aperture blades to open or close. 
         [0006]    The plurality of blades are supported by supporting pins, and are configured such that they are able to pivot freely around the supporting pins. A cam groove is formed in either one of the plurality of blades and the drive ring, and an engaging pin that is inserted into the cam groove is provided in the other one of the plurality of blades and the drive ring. When the drive ring is operated, this drive ring, the supporting pins, and the engaging pin work together so as to operate the plurality of blades. As a result, the aperture amount of the aperture portion in the base plate is adjusted. 
         [0007]    Here, the supporting pins are placed in positions that correspond to the outer side in the radial direction of the drive ring, and in the axial direction of the drive ring (i.e., the thickness direction of the drive ring) (see, for example, Japanese Published Examined Application No. H7-92580), and are placed on the outer side in the radial direction of the drive ring (see, for example, PCT International Publication No. WO 2009/113363). 
         [0008]    If the supporting pins are placed in positions that overlap with the drive ring in the axial direction, then the thickness of the entire diaphragm device is increased by the corresponding amount. Because of this, placing the supporting pins on the outer side in the radial direction of the drive ring makes it possible for the thickness of the overall diaphragm device to be reduced. 
         [0009]    However, if the supporting pins are placed on the outer side in the radial direction of the drive ring, then although the thickness of the overall diaphragm device can be reduced, the problem arises that the size in the radial direction of the overall diaphragm device increases (i.e., when seen in plan view). Moreover, if there are restrictions on the positions of the actuator and deceleration mechanism which are used to drive the drive ring, the problem arises that the size in the radial direction of the overall diaphragm device increases even more. 
       SUMMARY OF THE INVENTION 
       [0010]    The present invention was therefore conceived in view of the above-described circumstances, and it is an object thereof to provide a diaphragm device and an optical instrument in which the overall device size is reduced. 
         [0011]    In order to solve the above-described problems, a diaphragm device according to the present invention includes: a base plate having an aperture portion; a blade being supported by the base plate to be able to open and close the aperture portion; a drive ring being formed so as to surround the perimeter of the aperture portion, the drive ring being configured to drive the blade to open and close; a supporting pin pivotably supporting the blade being provided on the drive ring; and an engaging pin engaging with the blade and causing the blade to open or close in conjunction with the drive ring and the supporting pin, the engaging pin being provided on the base plate on an inner side of the supporting pin in the radial direction of the drive ring. 
         [0012]    By employing the above-described structure, it is possible to achieve a reduction in the thickness of the diaphragm device, and at the same time achieve a reduction in the device size in a radial direction. 
         [0013]    In the diaphragm device according to the present invention, the blade has a cam groove, and the engaging pin is inserted into the cam groove. 
         [0014]    By employing the above-described structure, it is possible to precisely control the opening and closing actions of the blades using the cam shafts. 
         [0015]    In the diaphragm device according to the present invention, the drive ring has an elongated hole that extends in the circumferential direction of the drive ring, and the engaging pin is inserted into the elongated hole. 
         [0016]    By employing the above-described structure, it is possible to limit any increase in the overall size of the diaphragm device in the radial direction even if the width in the radial direction of the drive ring has been increased. Because of this, it is possible to increase the rigidity of the drive ring at the same time as a reduction in the size of the diaphragm device is obtained. 
         [0017]    An optical instrument according to the present invention is provided with the above-described diaphragm device. 
         [0018]    By employing the above-described structure, it is possible to provide a small-sized optical instrument. 
         [0019]    According to the present invention, it is possible to achieve a reduction in the thickness of the diaphragm device, and at the same time to achieve a reduction in the device size in a radial direction. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]      FIG. 1  is a block diagram of an optical instrument according to a first embodiment of the present invention. 
           [0021]      FIG. 2  is a perspective view of a diaphragm device according to the first embodiment of the present invention. 
           [0022]      FIG. 3  is an exploded perspective view of the diaphragm device according to the first embodiment of the present invention. 
           [0023]      FIG. 4  is a plan view of a diaphragm blade according to the first embodiment of the present invention. 
           [0024]      FIG. 5  is a plan view showing a state in which only a single diaphragm blade and a drive ring are housed in a blade housing portion according to the first embodiment of the present invention. 
           [0025]      FIG. 6  is a plan view of an auxiliary blade according to the first embodiment of the present invention. 
           [0026]      FIG. 7A  is an operation explanatory view of the diaphragm device according to the first embodiment of the present invention and showing a fully open state. 
           [0027]      FIG. 7B  is an operation explanatory view of the diaphragm device according to the first embodiment of the present invention and showing an intermediate diaphragm state. 
           [0028]      FIG. 7C  is an operation explanatory view of the diaphragm device according to the first embodiment of the present invention and showing a fully closed state. 
           [0029]      FIG. 8  is a plan view showing a state in which only a single diaphragm blade and a drive ring are housed in a blade housing portion according to a second embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0030]    Hereinafter, an optical instrument and a diaphragm device of the embodiments will be described with reference made to the drawings. 
       First Embodiment 
     Optical Instrument 
       [0031]    Firstly, a first embodiment of this invention will be described based on  FIG. 1  through  FIG. 7 . 
         [0032]      FIG. 1  is a block diagram of an optical instrument  100 . 
         [0033]    As is shown in  FIG. 1 , the optical instrument  100  is used, for example, as a digital camera or still camera, and is provided with a diaphragm device  1 , a control unit  102 , and an imaging element  103 . 
         [0034]    The control unit  102  manages the overall operation of the optical instrument  100 , and is provided with a CPU, ROM, RAM, and the like. 
         [0035]    The imaging element  103  is, for example, a CCD or CMOS, and converts object images that are formed by light into electrical signals. 
         [0036]    Note that, although omitted from  FIG. 1 , the optical instrument  100  is also provided with a lens or the like that is used to adjust focal length. 
       Diaphragm Device 
       [0037]      FIG. 2  is a perspective view of the diaphragm device  1 , while  FIG. 3  is an exploded perspective view of the diaphragm device  1 . 
         [0038]    As is shown in  FIG. 2  and  FIG. 3 , the diaphragm device  1  is provided with a base plate  2  that is formed, for example, from resin. The base plate  2  is formed by a substantially circular plate-shaped base plate main body  3 , and an actuator chamber  4  which is substantially fan-shaped when seen in plan view and is integrally molded to one side of the base plate main body  3 . 
         [0039]    Note that in the following description, the radial direction of the base plate main body  3  is referred to simply as the radial direction, while the circumferential direction of the base plate main body  3  is referred to simply as the circumferential direction. 
         [0040]    An aperture portion  3   a  is formed in the center in the radial direction of the base plate main body  3 . Light that has passed through a lens (not shown) passes through this aperture portion  3   a . Three mounting seats  5  are molded integrally with an outer circumferential portion of the base plate main body  3  so as to protrude in the radial direction. The three mounting seats  5  are used to mount the diaphragm device  1 , for example, to a housing or the like of the optical instrument  100 , and a through hole  5   a  through which a bolt (not shown) can be inserted is formed on the majority of a central portion of the mounting seats  5 . The three mounting seats  5  are arranged in the circumferential direction. 
         [0041]    Furthermore, a wall portion  6  that is formed so as to stand upright around the outer circumference of the base plate main body  3  is provided on an outer circumferential portion of the base plate main body  3 . A blade housing portion  7  is formed by the wall portion  6  and a surface  3   b  of the base plate main body  3  in the shape of a casing having an open face. A plurality (for example, five in this embodiment) of diaphragm blades  8 , an auxiliary blade  9 , and a drive ring  10  that causes the diaphragm blades  8  and the auxiliary blade  9  to operate are housed in this blade housing portion  7 , and a blade supporting plate  11  is attached from above the blade housing portion  7 , the diaphragm blades  8 , and the auxiliary blade  9 , onto the base plate main body  3 . 
         [0042]    The blade supporting plate  11  is used to prevent the diaphragm blades  8 , the auxiliary blade  9 , and the drive ring  10 , as well as a rotor pinion  26  and an intermediate gear  27  (described below) from falling off from the base plate  2 . The blade supporting plate  11  is formed by a substantially circular plate-shaped supporting plate main body  12 , and by an actuator support  13  which is substantially fan-shaped when seen in plan view and is integrally molded to one side of the supporting plate main body  12 . The shape of the blade supporting plate  11  matches the shape of the base plate  2 . 
         [0043]    A plurality of engaging pieces  14  that are each able to deform elastically are formed on outer circumferential portions of the supporting plate main body  12  and on side portions of the actuator support  13  so as to protrude towards the base plate  2 . In contrast, notched portions  6   a  that are able to receive the engaging pieces  14  are formed on the wall portion  6  of the base plate main body  3  at positions that correspond to the engaging pieces  14 . In addition, recessed portions  4   a  that are each able to receive an engaging piece  14  are formed on two side portions of the actuator chamber  4  at positions that correspond to the engaging pieces  14 . Engaging pawls  39  that are each able to engage with the engaging piece  14  are formed in the notched portions  6   a  and the recessed portions  4   a . The base plate  2  and the blade supporting plate  11  are snap-fitted together by means of the engaging pieces  14  and the engaging pawls  39 . 
       Diaphragm Blades 
       [0044]      FIG. 4  is a plan view of a diaphragm blade  8 , while  FIG. 5  is a plan view showing a state in which only a single diaphragm blade  8  and the drive ring  10  are housed inside the blade housing portion  7  of the base plate  2 . Note that because the diaphragm blades  8  are all formed having the same shape, only one of the diaphragm blades  8  will be described. The remaining diaphragm blades  8  are allocated the same descriptive symbols and are not described here. 
         [0045]    As is shown in  FIG. 4  and  FIG. 5 , the diaphragm blades  8  are used to adjust the aperture amount of the aperture portion  3   a  that is formed in the base plate  2 . Each diaphragm blade  8  is formed from resin and has a slightly curved shape. More specifically, each blade  8  extends from the outer circumferential portion of the base plate main body  3  towards the aperture portion  3   a , and also extends across approximately half of the circle formed by the aperture portion  3   a  while curving so as to roughly follow the perimeter of the aperture portion  3   a.    
         [0046]    Moreover, the radius of curvature of one side (a first side)  8   c  in the width direction of the diaphragm blade  8  is set smaller than the radius of curvature of the other side (a second side)  8   d  in the width direction. As a result, the diaphragm blade  8  is formed such that the width of an end portion thereof that is located on the end portion side of the base plate main body portion  3  (this end portion is referred to below as a base end  8   a ) is formed wider, while an end portion thereof that is located substantially on the opposite side from the base end  8   a  sandwiching the approximate center in the blade extending direction (this end portion is referred to below as a distal end  8   b ) is formed most narrowly. In addition, the diaphragm blade  8  is provided on the surface  3   b  side of the base plate main body  3  such that the one side  8   c  in the width direction faces towards the aperture portion  3   a  side. 
         [0047]    Moreover, a supporting hole  15  is formed in the diaphragm blade  8  on the base end  8   a  side thereof and on the other side  8   d  in the width direction. Furthermore, a cam groove  16  that extends in the width direction is formed in the diaphragm blade  8  on the base end  8   a  side thereof at a separate position from the supporting hole  15 . 
       Auxiliary Blade 
       [0048]      FIG. 6  is a plan view of the auxiliary blade  9 . 
         [0049]    As is shown in  FIG. 2  and  FIG. 6 , when the aperture portion  3   a  in the base plate is closed by the diaphragm blades  8 , the auxiliary blade  9  is used to completely block off any small aperture that has not already been completely closed. The auxiliary blade  9  is formed from resin and has a slightly curved shape. More specifically, the auxiliary blade  9  extends towards the aperture portion  3   a  from a position slightly on the outer side of the outer circumferential portion of the base plate main body  3 , and also extends towards the aperture portion  3   a  while roughly following the perimeter of the aperture portion  3   a.    
         [0050]    The auxiliary blade  9  extends substantially linearly from an end portion thereof that is located on the base plate main body  3  side (hereinafter, this end portion is referred to as a base end  9   a ). In addition, an end portion of the auxiliary blade  9  that is located on the opposite side from the base end  9   a  (hereinafter, this end portion is referred to as a distal end  9   b ) is formed in a tapered shape that is also slightly curved. The auxiliary blade  9  is formed so that the base end  9   a  side becomes wide. The auxiliary blade  9  that is formed in this manner is placed on top of the diaphragm blades  8  such that the distal end  9   b  faces towards the aperture portion  3   a  side. 
         [0051]    An extending piece  9   c  that extends in the blade extending direction is provided at the base end  9   a  of the auxiliary blade  9  on the same side thereof in the width direction as the direction in which the distal end  9   b  faces. A supporting hole  17  is formed in this extending piece  9   c . Furthermore, a cam groove  18  that extends in the width direction is formed in the auxiliary blade  9  on the base end  9   a  side thereof at a separate position from the supporting hole  17 . 
       Drive Ring 
       [0052]    As is shown in  FIG. 2  and  FIG. 5 , a recessed portion  71  that extends around the inner circumferential surface of the wall portion  6  is formed in the blade housing portion  7  on the surface  3   b  side of the base plate main body  3 , and the drive ring  10  is housed in this recessed portion  71 . The drive ring  10  is made from resin, and an inner circumferential edge thereof is formed in a substantially toroidal shape so as to conform to an inner circumferential surface  71   a  of the recessed portion  71 . The drive ring  10  is provided such that it is able to rotate inside the blade housing portion  7 . Here, the inner circumferential surface  71   a  of the recessed portion  71  also functions as a guide that restricts the operating range of the drive ring  10 . 
         [0053]    A plurality (for example, five in this embodiment) of first supporting pins  19  that correspond to the number of diaphragm blades  8  are provided protruding upwards from the drive ring  10 . The respective first supporting pins  19  are arranged equidistantly in the circumferential direction. In addition, each first supporting pin  19  is inserted into the supporting hole  17  of the corresponding diaphragm blade  8 . As a result, each diaphragm blade  8  is supported such that it is able to rotate around the corresponding first supporting pin  19 . 
         [0054]    Moreover, a tooth portion  20  is formed in an outer circumferential edge of the drive ring  10  in a location thereof that corresponds to the actuator chamber  4 . This tooth portion  20  is formed such that it is able to mesh with an intermediate gear  27  (described below) that is provided in the actuator chamber  4 . 
         [0055]    Furthermore, first engaging pins  21  are provided protruding upwards on the base plate main body  3  on the inner side in the radial direction of the drive ring  10 . In the same way as the first supporting pins  19 , a plurality of these first engaging pins  21  (for example, five in this embodiment) are provided so as to match the number of diaphragm blades  8 , and are arranged equally distantly in the circumferential direction. Each first engaging pin  21  is inserted into the cam groove  16  of the corresponding diaphragm blade  8 . Namely, each of the first engaging pins  21  is shaped so as to enable it to engage with the corresponding diaphragm blade  8  so that, as a result, the operating range of each diaphragm blade  8  is restricted. 
         [0056]    Based on this structure, as is shown in detail in  FIG. 2 , the respective diaphragm blades  8  are arranged such that they are interlaced with each other, namely, such that the distal end  8   b  sides thereof overlap each other sequentially in the circumferential direction. As a result of this, a diaphragm hole  30  is formed whose perimeter is surrounded by the sides  8   c  in the width direction of the respective diaphragm blades  8 . 
         [0057]    On the other hand, a second supporting pin  22  is provided protruding upwards on a surface  4   b  of the actuator chamber  4  which is on the same plane as the surface  3   b  of the base plate main body  3 . More specifically, the second supporting pin  22  is provided protruding upright from the surface  4   b  of the actuator chamber  4  on one end side thereof in the circumferential direction and adjacently to the base plate main body  3 . This second supporting pin  22  is inserted into the supporting hole  17  in the auxiliary blade  9 . As a result, the auxiliary blade  9  is supported such that it is able to pivot around the second supporting pin. 
         [0058]    Moreover, the first supporting pin  19  is also inserted into the cam groove  18  in the auxiliary blade  9 , and thereby restricts the operating range of the auxiliary blade  9 . Namely, the first supporting pin  19  also functions as a second engaging pin  23  that restricts the operating range of the auxiliary blade  9 . 
       Actuator Chamber 
       [0059]    As is shown in  FIG. 2  and  FIG. 3 , an actuator  24  that is used to operate the drive ring  10  is mounted in the actuator chamber  4 . The actuator  24  is provided with a motor  25 , a rotor pinion  26  that is attached to a rotation shaft  29  of the motor  25 , and an intermediate gear  27  that meshes with the rotor pinion  26 . 
         [0060]    The motor  25  is placed on the opposite side of the actuator chamber  4  from the surface  4   b . A through hole  28  having a smaller diameter than the outer diameter of the motor  25  is formed in the actuator chamber  4  at a position that corresponds to the motor  25 . The rotation shaft  29  of the motor  25  faces the surface  4   b  side of the actuator chamber  4  via this through hole  28 . In addition, the rotor pinion  26  and the intermediate gear  27  are located on the surface  4   b  side of the actuator chamber  4 . 
         [0061]    Moreover, the tooth portion  20  of the drive ring  10  meshes with the intermediate gear  27 . The intermediate gear  27  decelerates the rotation of the motor  25  (i.e., the rotor pinion  26 ) and then transmits it to the drive ring  10 . As a result, the drive force from the motor  25  is transmitted to the drive ring  10  via the rotor pinion  26  and the intermediate gear  27 , and this results in the drive ring  10  being rotated. 
       Operation of the Diaphragm Device 
       [0062]    Next, an operation of the diaphragm device  1  will be described based on  FIGS. 7A to 7C . 
         [0063]      FIGS. 7A to 7C  are operation explanatory views of the diaphragm device  1 , with  FIG. 7A  showing a fully open state,  FIG. 7B  showing an intermediate diaphragm state, and  FIG. 7C  showing a fully closed state. 
         [0064]    Note that the fully open state is one in which the area of the aperture of the diaphragm hole  30  (see  FIG. 2 ) formed by the diaphragm blades  8  is at maximum. The fully closed state is one in which the area of the aperture of the diaphragm hole  30  is at minimum, and this minimized diaphragm hole  30  is then completely closed off by the auxiliary blade  9 . The intermediate diaphragm state is one in which the area of the aperture of the diaphragm hole  30  is an intermediate size between the fully open state and the fully closed state. 
         [0065]    As is shown in  FIG. 7A , in the fully open state the first supporting pins  19  (i.e., the second engaging pin  23 ) of the drive ring  10  and the first engaging pins  21  are at their closest positions to each other, while the first supporting pin  19  and the second supporting pin  22  are at their furthest positions from each other. In other words, the first engaging pins  21  are located at their closest positions to the first supporting pins  19  in the cam grooves  16  of the diaphragm blades  8 . Moreover, the first supporting pin  19  (i.e., the second engaging pin  23 ) is located at its furthest position from the second supporting pin  22  in the cam groove  18  of the auxiliary blade  9 . Note also that in this fully open state the size of the diaphragm hole  30  is slightly larger than the size of the aperture portion  3   a  of the base plate  2 . 
         [0066]    As is shown in  FIG. 7B , if the motor  25  is driven when the diaphragm hole  30  is in the fully open state so that the drive ring  10  is rotated in one direction CW (i.e., in a clockwise direction in this embodiment), the first supporting pins  19  (i.e., the second engaging pin  23 ) are moved in a direction in which they move away from the first engaging pins  21 , and the first supporting pin  19  (i.e., the second engaging pin  23 ) is moved in a direction in which it approaches the second supporting pin  22 . 
         [0067]    As a result of this, the diaphragm blades  8  are pivoted in the one direction CW (i.e., in a clockwise direction) around the first supporting pins  19 . In contrast, the auxiliary blade  9  is pivoted in another direction CCW (i.e., in a counterclockwise direction in this embodiment) around the second supporting pin  22 . 
         [0068]    Here, the angle of the extending direction of the cam groove  16  that is formed in each diaphragm blade  8  relative to the rotation direction of the drive ring  10  (i.e., the tangential direction of the drive ring  10 ) is large. In contrast, the angle of extending direction of the cam groove  18  that is formed in the auxiliary blade  9  relative to the rotation direction of the drive ring  10  is small. Consequently, even though the rotation angle of the drive ring  10  is the same for both of the diaphragm blades  8  and the auxiliary blade  9 , the rotation angle (i.e., the displacement amount) of the diaphragm blades  8  is large, while the rotation angle of the auxiliary blade  9  is small. As a result, in the intermediate diaphragm state, the diaphragm hole  30  is not closed off by the auxiliary blade  9 . 
         [0069]    As is shown in  FIG. 7C , if the drive ring  10  is rotated further in the one direction CW, the first supporting pins  19  (i.e., the second engaging pin  23 ) of the drive ring  10  and the first engaging pins  21  are at their furthest positions from each other, while the first supporting pin  19  and the second supporting pin  22  are at their closest positions to each other. In other words, the first engaging pins  21  are located at their furthest positions from the first supporting pins  19  in the cam grooves  16  of the diaphragm blades  8 . Moreover, the first supporting pin  19  (i.e., the second engaging pin  23 ) is located at its closest position to the second supporting pin  22  in the cam groove  18  of the auxiliary blade  9 . As a result, the diaphragm device  1  is in the fully closed state. 
         [0070]    Note that when the diaphragm device  1  is changed from the fully closed state to the fully open state, the above-described tasks are performed in reverse sequence. 
         [0071]    In this manner, in the above-described first embodiment, the first supporting pins  19  that are used to support the diaphragm blades  8  such that they are able to pivot freely are provided in the drive ring  10 . Moreover, the first engaging pins  21  that engage with the diaphragm blades  8  and regulate the operations of the diaphragm blades  8  are provided on the inner side in the radial direction of the drive ring  10 . Because of this, it is possible to attain a smaller size in the radial direction compared to a conventional structure, while also achieving a reduced thickness in the diaphragm device  1 . 
         [0072]    Moreover, by forming the cam groove  16  in each diaphragm blade  8  and inserting the first engaging pins  21  in these cam grooves  16 , the diaphragm blades  8  and the first engaging pins  21  can be engaged with each other. Furthermore, by forming the cam groove  18  in the auxiliary blade  9  and inserting the first supporting pin  19  (i.e., the second engaging pin  23 ) in this cam groove  18 , the auxiliary blade  9  and the first supporting pin  19  (i.e., the second engaging pin  23 ) can be engaged with each other. Because of this, by forming the respective cam grooves  16  and  18  with a high level of precision, it is possible to precisely regulate the operations of the respective blades  8  and  9 . 
         [0073]    Furthermore, the first supporting pins  19  (i.e., the second engaging pin  23 ) are provided in the drive ring  10 . Moreover, the first engaging pins  21  are provided on the base plate main body  3  on the inner side in the radial direction of the drive ring  10 . Furthermore, the second supporting pin  22  is provided in the actuator chamber  4 , which is on the outer side in the radial direction from the drive ring  10 . Because of this, the direction in which the diaphragm blades  8  are pivoted around the first supporting pins  19  by a single rotation of the drive ring  10  is the opposite of the direction in which the auxiliary blade  9  is pivoted around the second supporting pin  22  by this same rotation of the drive ring  10 . In other words, the diaphragm blades  8  and the auxiliary blade  9  perform mutually different actions as the result of a single operation performed by the drive ring  10 . Accordingly, the diaphragm blades  8  and the auxiliary blade  9  are prevented from obstructing each other when the diaphragm blades  8  and the auxiliary blade  9  are performing an opening or closing action. Consequently, there is no need for another device to be provided between the diaphragm blades  8  and the auxiliary blade  9  in order to separate these from each other, and the thickness of the diaphragm device  1  can be made thinner. 
         [0074]    Moreover, one of the first supporting pins  19  that are provided on the drive ring  10  in order to support the diaphragm blades  8  also functions as the second engaging pin  23  that regulates the operating range of the auxiliary blade  9 . Because of this, the number of parts forming the diaphragm device  1  can be reduced, and in addition to it becoming possible to achieve a reduction in the size of the diaphragm device  1 , the production costs thereof can also be reduced. 
         [0075]    Furthermore, because the second supporting pin  22  is provided in the actuator chamber  4 , there is no need to provide extra space on the base plate  2  (i.e., on the base plate main body  3 ) in order for this second supporting pin  22  to be provided. This enables the size of the diaphragm device  1  to be further reduced. 
       Second Embodiment 
       [0076]    Next, a second embodiment of this invention will be described based on  FIG. 8 . Note that aspects that are the same as in the first embodiment are allocated the same descriptive symbols and any description thereof is omitted. 
         [0077]      FIG. 8  is a plan view showing a state in which only one diaphragm blade  8  and a drive ring  210  are housed in the blade housing portion  7  of the base plate  2  of a diaphragm device  201  according to the second embodiment, and this view corresponds to the above-described  FIG. 5 . 
         [0078]    As is shown in  FIG. 8 , the second embodiment differs from the above-described first embodiment in that the shape of the drive ring  210  of the second embodiment is different from the shape of the drive ring  10  of the first embodiment. Moreover, the second embodiment also differs from the first embodiment in that, in the first embodiment, drive force from the motor  25  is transmitted to the drive ring  10  via the rotor pinion  26  and the intermediate gear  27 , however, in the second embodiment, drive force from the motor  25  is transmitted to the drive ring  210  solely via the rotor pinion  26 . 
         [0079]    More specifically, the width in the radial direction of the drive ring  210  is set wider than the width of the drive ring  10  of the first embodiment. In addition, elongated holes  41  that extend in an elongated elliptical shape in the circumferential direction are formed in positions that correspond to the first engaging pins  21  that are provided on a base plate  202 . The first engaging pins  21  are inserted into these elongated holes  41 . The width in the radial direction of the elongated holes  41  of the drive ring  210  is set sufficiently greater than the diameter of the first engaging pins  21 . 
         [0080]    In addition to this, a structure is employed in which the intermediate gear  27  of the first embodiment is omitted, and the tooth portion  20  of the drive ring  210  is made to mesh directly with the rotor pinion  26 . Because of this, the outer diameter of the drive ring  210  can be set to a larger size corresponding to the amount obtained by omitting the intermediate gear  27 . 
         [0081]    Moreover, the outer diameter of a base plate main body  203  of the base plate  202  is also set to a larger size to correspond to the increase in the drive ring  210 . In addition, unlike the above-described first embodiment, the actuator chamber  4  is not provided, and the rotor pinion  26  is provided inside the base plate main body  203 . 
         [0082]    Accordingly, according to the above-described second embodiment, by forming the elongated holes  41  in the drive ring  210 , the width in the radial direction of the drive ring  210  can be set wider compared to the above-described first embodiment, without causing the drive ring  210  to interfere with the first engaging pins  21 . Because of this, it is possible to increase the rigidity of the drive ring  210  at the same time as a reduction in the size of the diaphragm device  201  is obtained. 
         [0083]    Moreover, the width in the radial direction of the elongated holes  41  in the drive ring  210  is set sufficiently larger than the diameter of the first engaging pins  21 . Because of this, the rotation of the drive ring  210  is not hindered by the first engaging pins  21 , so that the drive ring  210  is able to rotate smoothly. 
         [0084]    Furthermore, a structure is employed in which the intermediate gear  27  of the first embodiment is omitted, and the tooth portion  20  of the drive ring  210  is made to mesh directly with the rotor pinion  26 . Consequently, the outer diameter of the drive ring  210  is set to a larger size corresponding to the amount obtained by omitting the intermediate gear  27 . Because of this, sufficient torque of the drive ring  210  can be secured even though the intermediate gear  27  has been omitted. 
         [0085]    Moreover, because the actuator chamber  4  is omitted from the base plate  202 , an overall reduction in the size of the base plate  202  can be achieved even though the outer diameter of the base plate main body  203  has been increased in accordance with the size of the drive ring  210 . 
         [0086]    Note that the present invention is not limited to the above-described embodiments, and various modifications may be made to the above-described embodiments in so far as they do not depart from the scope of the present invention. 
         [0087]    For example, in the above-described embodiments, a case is described in which the optical instrument  100  is used, for example, as a digital camera or still camera or the like. However, the present invention is not limited to this and the optical instrument  100  may be used for various applications. 
         [0088]    Moreover, in the above-described embodiments, a case is described in which the cam grooves  16  are formed in the diaphragm blades  8 , and the diaphragm blades  8  are made to engage with the first engaging pins  21  by inserting the first engaging pins  21  into these cam grooves  16 . Furthermore, a case is also described in which the cam groove  18  is formed in the auxiliary blade  9 , and the auxiliary blade  9  is made to engage with the first supporting pin  19  by inserting the first supporting pin  19  (i.e., the second engaging pin  23 ) into this cam groove  18 . However, the present invention is not limited to this and it is also possible to employ a structure in which a plurality of engaging pins  21  and  23  are provided without the respective cam grooves  16  and  18  being formed in the respective blades  8  and  9 , and the operations of the diaphragm blades  8  and the auxiliary blade  9  are regulated by these engaging pins  21  and  23 . 
         [0089]    For example, it is also possible to provide the engaging pins  21  and  23  for the respective blades  8  and  9  in predetermined positions on the forward side in the rotation direction of the drive rings  10  and  210 , and in predetermined positions on the rearward side in this rotation direction. It is also possible to employ a structure in which the respective blades  8  and  9  are operated by being pressed against these engaging pins. 
         [0090]    Furthermore, in the above-described embodiments, a case is described in which the first supporting pins  19  that are provided on the drive rings  10  and  210  also function as the second engaging pins  23  that regulate the operating range of the auxiliary blade  9 . However, the present invention is not limited to this, and it is also possible for the second engaging pins  23  to be provided separately from the first supporting pins  19 . 
         [0091]    Moreover, in the above-described embodiments, a case is described in which five diaphragm blades  8  are provided and the aperture amount of the aperture portion  3   a  (i.e., the diaphragm hole  30 ) in the base plates  2  and  202  are adjusted by these five diaphragm blades  8 . However, the number of diaphragm blades  8  is not limited to five, and can be set to a desired number. 
         [0092]    Furthermore, in the above-described embodiments, a case is described in which the first supporting pins  19  (i.e., the second engaging pins  23 ) are provided on the drive ring  10 , and the first engaging pins  21  are provided on the base plate main body  3  on the inner side in the radial direction of the drive ring  10 , and the second supporting pin  22  is provided in the actuator chamber  4  that is on the outer side in the radial direction of the drive ring  10 . In addition, a case is described in which the direction in which diaphragm blades  8  are pivoted around the first supporting pins  19  by a single rotation of the drive ring  10 , and the direction in which the auxiliary blade  9  is pivoted around the second supporting pin  22  by this same rotation of the drive ring  10  are mutually opposite each other. However, the present invention is not limited to this, and it is sufficient if a structure is employed in which the diaphragm blades  8  and the auxiliary blade  9  are made to perform mutually different actions by a single rotation of the drive ring  10 . 
         [0093]    While preferred embodiments of the invention have been described and illustrated above, it should be understood that these are exemplary of the invention and are not to be considered as limiting. Additions, omissions, substitutions, and other modifications can be made without departing from the spirit or scope of the present invention. Accordingly, the invention is not to be considered as limited by the foregoing description and is only limited by the scope of the appended claims.