Patent Publication Number: US-2020278590-A1

Title: Light shielding unit and lens barrell provided with same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to Japanese Patent Application No. 2019-035198 filed on Feb. 28, 2019. The entire disclosure of Japanese Patent Application No. 2019-035198 is hereby incorporated herein by reference. 
     BACKGROUND 
     Technical Field 
     The present disclosure relates to a light shielding unit and to a lens barrel comprising the same. 
     Description of the Related Art 
     An imaging device such as a camera is provided with a plurality of lens groups, an aperture for adjusting the surface area of an opening through which light passes, a shutter unit, and so forth. 
     For example, Patent Literature 1 discloses a blade drive device comprising a plurality of blades disposed in a ring around a light passage path, and a drive ring for rotating these blades, in order to reduce upward warpage of the blade group. Each of the blades has an engaging portion that engages with a cam groove provided to the drive ring, and at least part of the cam groove is provided so as to be inclined outward in the radial direction of the drive ring. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: JP-A 2016-102830 
     Patent Literature 2: Japanese Patent No. 6,068,903 
     SUMMARY 
     It is an object of the present disclosure to provide a light shielding unit capable of suppressing the warping of movable blades while affording smooth operation of the movable blades, as well as a lens barrel comprising this light shielding unit. 
     The light shielding unit according to the present disclosure comprises a first frame, a second frame, a plurality of movable blades, a drive ring, and a support. The first frame has a first frame having a first opening through which light passes. The second frame has a second opening through which light passes. The movable blades are disposed between the first frame and the second frame, a third opening through which the light that has passed through the first opening passes is formed in the movable blades, and these movable blades adjust the amount of light passing through by varying the size of the third opening. The drive ring is disposed between the first frame and the second frame and is rotatably driven when the movable blades are opened and closed. The support is provided to the first frame and/or the second frame and supports the movable blades in the direction of suppressing upward warpage of the movable blades in a state in which the movable blades have moved in the direction of reducing the size of the third opening. 
     Technical Effects 
     The light shielding unit according to the present disclosure allows upward warpage of the movable blades to be suppressed, while affording smooth operation of the movable blades. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a cross section of the configuration of a lens barrel that includes the aperture unit according to an embodiment of the present disclosure; 
         FIG. 2  is an exploded oblique view of the components constituting the aperture unit included in the lens barrel in  FIG. 1 ; 
         FIG. 3  is an oblique view of the aperture unit in  FIG. 2 ; 
         FIG. 4A  is a diagram illustrating a state in which the aperture blades of the aperture unit in  FIG. 3  have been constricted (a state in which the opening diameter is reduced), as viewed from the opposite side from subject side (cover side); 
         FIG. 4B  is a diagram illustrating a state in which the aperture blades of the aperture unit in  FIG. 3  have been constricted (a state in which the opening diameter is reduced), as viewed from the subject side (base plate side); 
         FIG. 5A  is a diagram illustrating a state in which the aperture blades of the aperture unit in  FIG. 4A  are transitioning to a fully open state, as viewed from the opposite side from the subject side (cover side); 
         FIG. 5B  is a diagram illustrating a state in which the aperture blades of the aperture unit in  FIG. 4B  are transitioning to a fully open state, as viewed from the subject side (base plate side); 
         FIG. 6A  is a diagram illustrating a state in which the aperture blades of the aperture unit in  FIG. 4A  have transitioned to a fully open state, as viewed from the opposite side from the subject side (cover side); 
         FIG. 6B  is a diagram illustrating a state in which the aperture blades of the aperture unit in  FIG. 4B  have transitioned to a fully open state, as viewed from the opposite side from the subject side (base plate side); 
         FIG. 7  is an exploded oblique view of a state in which the aperture blades of the aperture unit in  FIG. 3  have transitioned to a fully open state; 
         FIG. 8  is an oblique view of the configuration of a drive ring constituting the aperture unit in  FIG. 3 ; 
         FIG. 9  is an oblique view of the configuration of an aperture blade constituting the aperture unit in  FIG. 3 ; 
         FIG. 10  is an oblique view showing the configuration of a cover constituting the aperture unit in  FIG. 3 ; 
         FIG. 11  is an oblique view showing a state in which one aperture blade is disposed on the cover in  FIG. 10 ; 
         FIG. 12  is an oblique view as seen from the AA direction in  FIG. 11 ; 
         FIG. 13  is a detail view of the B portion in  FIG. 12 ; 
         FIG. 14  is an oblique view showing a state in which one aperture blade, a drive ring, a photo interrupter, a gear, and a motor are assembled on the cover in  FIG. 9 ; 
         FIG. 15A  is a diagram illustrating a state in which the aperture blades of the aperture unit in  FIG. 3  are constricted (a state in which the opening diameter is reduced); 
         FIG. 15B  is a cross section of the aperture unit in  FIG. 15A ; 
         FIG. 16A  is a detail cross section of the upper half in  FIG. 15B ; 
         FIG. 16B  is a cross section comparing the upward warpage of the aperture blades of the aperture unit in this embodiment (solid line) with the upward warpage of the aperture blades of a conventional aperture unit (broken line); 
         FIG. 17A  is a cross section illustrating the positional relation between the aperture blades and a fixed opening sheet in the optical axis direction in a state in which the aperture blades of the aperture unit in  FIG. 3  have been constricted (a state in which the opening diameter is reduced); 
         FIG. 17B  is a cross section illustrating a state in which the aperture blades of the aperture unit in  FIG. 17A  have transitioned to an open state; 
         FIG. 18  is an oblique view of the configuration of a wall provided to the cover in order to prevent oil from entering in the aperture unit in  FIG. 3 ; 
         FIG. 19  is an oblique view of the configuration of a wall provided to the base plate constituting the aperture unit in  FIG. 3 ; 
         FIG. 20  is a cross section schematically showing a staggered structure of a wall for preventing oil from entering the aperture unit in  FIG. 3 , and the configuration of a fixed opening sheet, the aperture blades, and the cover; 
         FIG. 21A  shows the configuration of an aperture blade (first blade) constituting the aperture unit in another embodiment of this disclosure; 
         FIG. 21B  shows the configuration of an aperture blade (second blade) constituting the aperture unit in another embodiment of this disclosure; 
         FIG. 22A  is a diagram of the configuration of an aperture unit in which the one aperture blade (first blade) shown in  FIG. 21A  is disposed, as viewed from the subject side; 
         FIG. 22B  is a diagram of the configuration of an aperture unit in which the one aperture blade (first blade) shown in  FIG. 21A  is disposed, as viewed from the opposite side from the subject side; 
         FIG. 23A  is a diagram of the configuration of an aperture unit in which the one aperture blade (second blade) shown in  FIG. 21B  is disposed, as viewed from the subject side; 
         FIG. 23B  is a diagram of the configuration of an aperture unit in which the one aperture blade (second blade) shown in  FIG. 21B  is disposed, as viewed from the opposite side from the subject side; 
         FIG. 24A  is a see-through view of the configuration of the aperture unit in which the one aperture blade (first blade) shown in  FIG. 21A  is disposed, as viewed from the opposite side from the subject side; 
         FIG. 24B  is a see-through view of the configuration of the aperture unit in which the one aperture blade (second blade) illustrated in  FIG. 21B  is disposed, as viewed from the opposite side from the subject side; 
         FIG. 25  is a diagram of a state in which the aperture blades (first blades) shown in  FIG. 21A  and the aperture blades (second blades) shown in  FIG. 21B  are alternately disposed in the circumferential direction and constricted (a state in which the opening diameter is reduced), as viewed from the opposite side from the subject side; 
         FIG. 26  is an oblique view of the configuration of an aperture blade included in the aperture unit in yet another embodiment of the present disclosure; and 
         FIG. 27  is a cross section comparing the effect of suppressing the upward warpage of the aperture blades, between the configuration in  FIG. 26  in which the aperture blades are constricted (a state in which the opening diameter is reduced) and the configuration in Embodiment 1. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Knowledge on which this Disclosure is Based, etc. 
     The above-mentioned conventional blade drive device has the following problems. 
     With the device disclosed in the above-mentioned publication, part of the cam groove is inclined outward in the radial direction of the drive ring. Therefore, when the blades are driven, the bosses that move through the cam grooves are more likely to snag, which may cause the blades to malfunction. 
     Embodiments will now be described in detail with reference to the drawings as needed. However, some unnecessarily detailed description may be omitted. For example, detailed description of already known facts or redundant description of components that are substantially the same may be omitted. This is to avoid unnecessary repetition in the following description, and facilitate an understanding on the part of a person skilled in the art. 
     The applicant has provided the appended drawings and the following description so that a person skilled in the art might fully understand this disclosure, but does not intend for these to limit what is discussed in the patent claims. 
     The “subject side,” “image plane side,” and “light incident direction” referred to herein are shown in  FIGS. 1 and 2 . The “image plane side” and the “opposite side from the subject side” are the same side. 
     Embodiment 1 
     A lens barrel  10  including an aperture unit (light shielding unit)  20  according to an embodiment of the present disclosure will now be described with reference to  FIGS. 1 to 20 . 
     Here, the lens barrel  10  in this embodiment a configuration for suppressing the upward warpage of aperture blades  23  that occurs in a state in which the aperture blades (movable blades)  23  constituting the aperture unit (light shielding unit)  20  are constricted (a state in which the opening diameter is reduced). Specific configurations of these will be described below. 
     The “direction of the upward warpage of the aperture blades  23 ” is the direction in which the distal ends of the aperture blades  23  overlap with each other (are woven together) and expand when the aperture blades  23  are rotated in the direction of constricting the opening diameter, and in this embodiment, it means the direction on the image plane side, as shown in  FIG. 17A , etc. 
     (1) Configuration of Lens Barrel  10   
     The lens barrel  10  according to this embodiment is an interchangeable lens barrel mounted on a camera body (not shown), and as shown in  FIG. 1 , it comprises an outer frame  11 , an inner frame  12 , an actuator  13 , a guide pole  14 , a fourth lens frame  15 , a mount  16 , first to fifth lenses L 1  to L 5 , and an aperture unit  20 . X is the optical axis defined by the first lens L 1  to the fifth lens L 5 . 
     The outer frame  11  is a substantially cylindrical member, constitutes the outer contour of the lens barrel  10 , and encompasses various components such as the first lens L 1  to the fifth lens L 5 . 
     The inner frame  12  is disposed on the inner peripheral surface side of the outer frame  11 , and holds the first lens L 1  on the furthest upstream side in the light incident direction, the second lens L 2  downstream of that, and the third lens L 3  downstream of that. The inner frame  12  also holds the actuator  13  and the guide pole  14  substantially to the side of the third lens L 3 ; the fourth lens frame  15  downstream from the third lens L 3 , holding it so that it can move on the guide pole  14  in the optical axis X direction; the aperture unit  20  downstream of that; and the fifth lens L 5  downstream of that. 
     The actuator  13  is a focus motor that is driven for focusing, and is held by the inner frame  12 . When power is supplied from an electric circuit (not shown), the actuator  13  moves the fourth lens frame  15 , which holds the fourth lens (focus lens) L 4 , back and forth along the guide pole  14  in the optical axis X direction. 
     The guide pole  14  is a rod-shaped member that guides the fourth lens frame  15 , which is driven by the actuator  13 , back and forth in the optical axis X direction. The guide pole  14  is held by the inner frame  12  and is disposed parallel to the optical axis X direction. 
     The fourth lens frame  15  is included in the lens group constituting the optical system of the lens barrel  10 , holds the fourth lens L 4 , which moves in the optical axis X direction to adjust the focus of a light beam incident on the lens, that is, for focusing, and is driven by the actuator  13 . 
     Alternatively, the fourth lens frame  15  holds the fourth lens L 4 , which moves in the optical axis X direction to adjust the focal length of the light beam incident on the lens, that is, for zooming, and is driven in conjunction with the zoom operation. That is, the fourth lens frame  15  is movable in the optical axis direction for focusing and zooming. 
     The mount  16  is the portion that is mounted on the camera body (not shown), is held by the outer frame  11 , and is disposed the furthest downstream in the light incident direction inside the lens barrel  10 . 
     As shown in  FIG. 1 , the first lens L 1  to the fifth lens L 5  are optical systems for guiding light in the optical axis X direction, and are disposed in order starting from the subject side to the image plane side in the light incident direction. 
     Of all the lens groups included in the lens barrel  10 , the first lens L 1  is disposed closest to the subject. 
     The second lens L 2  is disposed at a position close to the image plane side (opposite side from the subject side) of the first lens L 1  inside the inner frame  12 . 
     The third lens L 3  is disposed inside the inner frame  12  at a position that is a specific distance away from the second lens L 2  to the image plane side. 
     The fourth lens L 4  is a focus lens provided inside the inner frame  12 , can be moved back and forth in the optical axis X direction by the actuator  13 , and is held by the fourth lens frame  15 . 
     The fifth lens L 5  is disposed downstream from the aperture unit  20  in the optical axis X direction, and is the closest to the image plane of all the lens groups included in the lens barrel  10 . 
     The aperture unit  20  is disposed between the fourth lens L 4  and the fifth lens L 5  inside the inner frame  12 , and adjusts the amount of light incident on an imaging element provided on the camera body side by adjusting the surface area or the opening diameter through which light transmitted from the first lens L 1  through the fourth lens L 4  passes. The configuration of the aperture unit  20  will be described in detail below. 
     (2) Configuration of Aperture Unit  20   
     With the lens barrel  10  in this embodiment, as shown in  FIG. 1 , the first lens L 1  to the fourth lens are disposed closer to the subject than the aperture unit  20  in the optical axis X direction. 
     As shown in  FIG. 1 , the aperture unit  20  is disposed downstream of the fourth lens L 4  that functions as a focus lens. As shown in  FIG. 2 , the aperture unit  20  has a base plate (first frame)  21 , a drive ring  22 , a plurality of aperture blades (movable blades)  23 , a sheet member  24 , a cover (second frame)  25 , attachment screws  26 , a fixed opening sheet (fixed opening member)  27 , a drive motor  28 , a photo interrupter  29   a , and an FPC  29   b . As shown in  FIG. 3 , the aperture unit  20  adjusts the amount of light passing through openings  21   b ,  22   b ,  23   e ,  24   b ,  25   b , and  27   b  formed at the center of each of the substantially annular members by opening and closing the plurality of aperture blades  23  driven by the drive motor  28 . The configuration is such that the centers of the openings  21   b ,  22   b ,  23   e ,  24   b ,  25   b , and  27   b  and the opening in the aperture unit  20  substantially pass through the optical axis X. 
     As shown in  FIGS. 4A and 3B , in a state in which the aperture blades  23  are most constricted, the aperture unit  20  is in a state in which the opening diameter (surface area) of the opening  23   e  formed by the aperture blades  23  is at its smallest. 
     At this point, as shown in  FIG. 4A , the aperture blades  23  are disposed such that the parts on the distal end side, as viewed on the opposite side from the subject side, that is, on the image plane side, overlap and are woven together in the circumferential direction around the optical axis X, that is, in a state of being warped upward. 
     When the aperture blades  23  are rotated from the state shown in  FIGS. 4A and 4B , the opening diameter (surface area) of the opening  23   e  formed by the aperture blades  23  gradually increases as shown in  FIGS. 5A and 5B . 
     When the aperture blades  23  are further rotated from the state shown in  FIGS. 5A and 5B , as shown in  FIGS. 6A and 6B , the aperture blades  23  go all the way into the gap between the base plate  21 , the cover  25 , etc., so that the opening diameter (surface area) of the opening  23   e  formed by the aperture blades  23  is at its largest. 
     In the state shown in  FIGS. 6A and 6B  in which the diameter or the surface area of the opening  23   e  is at its largest, the size of the open portion of the aperture unit  20  is defined by a fixed opening sheet  27  (discussed below). That is, the opening  27   b  of the fixed opening sheet  27  is constant and is smaller than the opening  23   e  of the aperture blades  23  having the largest opening diameter or surface area. 
     As described above, the aperture unit  20  in this embodiment can adjust the amount of light passing through the open portion by rotating the aperture blades  23  between the closed state shown in  FIGS. 4A and 4B  and the open state shown in  FIGS. 6A and 6B . 
     As shown in  FIG. 2 , the base plate (first frame)  21  is a substantially annular member that is disposed closest to the subject in the light incident direction, and has a substantially annular main body  21   a ; an opening (first opening)  21   b  formed in the center portion of the main body  21   a  for transmitting light that is incident from the subject side; a wall (first wall)  21   c  (see  FIG. 19 ); a radial restrictor  21   d  (see  FIGS. 16A, 17A, and 19 ); a first optical axis direction restrictor  21   e  (see  FIG. 19 ); and a second optical axis direction restrictor  21   f  (see  FIGS. 16A, 17A, and 19 ). As shown in  FIG. 2 , the drive ring  22 , the aperture blades  23 , the sheet member  24 , and the cover  25  are disposed in that order, starting from the subject side, between the base plate  21  and the fixed opening sheet  27  that is disposed the furthest downstream in the light incident direction. 
     As shown in  FIGS. 3 and 7 , a drive motor  28  or the like (discussed below) that is fixed to the base plate  21  is disposed on the surface on the subject side of the base plate  21  in order to impart a driving force for opening and closing the aperture blades  23 . 
     As shown in  FIGS. 2 and 7 , the drive ring  22  is a substantially annular member disposed between the base plate  21  and the aperture blades  23  in the light incident direction. 
     More precisely, as shown in  FIG. 8 , the drive ring  22  has a substantially annular main body  22   a , an opening  22   b  formed in the center thereof, a plurality of protrusions (supports, first supports)  22   c , a gear  22   d , a light blocker  22   e , radial restrictors  22   f  (see  FIGS. 8, 16A, and 17A ), first optical axis direction restrictors  22   g  (see  FIG. 8 ), and a second optical axis direction restrictor  22   h  (see  FIGS. 14, 16A, and 17A ). The drive ring  22  is rotated by the drive motor  28  (discussed below), causing the aperture blades  23  to rotate. More specifically, when the drive ring  22  transmits the drive force from the drive motor  28  (discussed below) via a gear  28   a , the radial restrictors  22   f  of the drive ring  22  are restricted in their radial positions by the radial restrictor  21   d  of the base plate  21 . Furthermore, the first optical axis direction restrictors  22   g  of the drive ring  22  hit the first optical axis direction restrictor  21   e  of the base plate  21 , and the second optical axis direction restrictor  22   h  of the drive ring  22  hits the second optical axis direction restrictor  21   f  of the base plate  21 . 
     Consequently, the drive ring  22  is sandwiched between the two optical axis direction restrictors  21   e  and  21   f  of the base plate  21 , and therefore rotates around the optical axis X while its position in the optical axis direction is restricted. As a result, the drive ring  22  rotates the aperture blades  23  and adjusts the amount of light passing through the opening between the constricted and open states of the aperture blades  23 , that is, between the minimum diameter and the maximum diameter. 
     As shown in  FIG. 8 , the main body  22   a  is a substantially annular plate-like member, and has an opening  22   b  formed at its center. 
     The opening  22   b  is an opening through which the light of the aperture unit  20  passes, and has a diameter or surface area substantially equal to or slightly larger than that of the opening  23   e  formed when the aperture blades  23  are fully opened. The opening  22   b  has a diameter or surface area substantially equal to or larger than the opening  27   b  in the fixed opening sheet  27  (discussed below). 
     As shown in  FIGS. 8, 16   a ,  16   b ,  17   a , and  17   b , the protrusions  22   c  are provided on the surface of the main body  22   a  that is in contact with the surface on the opposite side from the direction of upward warpage of the aperture blades, and in this embodiment, eleven of these protrusions  22   c  are disposed at substantially equal angular intervals in the circumferential direction so as to protrude in an annular shape on the opposite side from the subject side (the cover  25  side), that is, from the surface on the image plane side. The protrusions  22   c  hit a part of the aperture blades  23  in the annular portion, and support the aperture blades  23  from the subject side. Also, through holes are formed in the approximate center of the annularly protruding portions of the protrusions  22   c , and bosses  23   b  (first main shafts) of the aperture blades  23  (discussed below) are inserted into these holes. 
     The protrusions  22   c  (first supports) have a convex shape protruding from the surface of the drive ring  22  in the direction of the upward warpage of the aperture blades  23 , and support the vicinity of the bosses  23   b  (first main shafts) of the aperture blades  23 . 
     The protrusions  22   c  preferably have a substantially arced shape, a substantially elliptical shape, a substantially parabolic shape, a substantially multidimensional curve shape, or a gentle curved shape in a cross section that includes the center axis of the through holes or the bosses  23   c  (first main shafts). 
     With these configurations, the aperture blades  23  can be smoothly moved without an increase in the drive load due to abrasion or catching, and at the same time, upward warpage due to the weaving together of the aperture blades can be efficiently suppressed. 
     The gear  22   d  is formed on part of the outer peripheral surface of the main body  22   a  so as to mesh with the gear  28   a  (see  FIGS. 2 and 14 ) attached to the rotation shaft of the drive motor  28 . When the rotational drive force of the drive motor  28  is transmitted via the gear  28   a , the gear  22   d  drives the drive ring  22  to rotate around the optical axis X. 
     The light blocker  22   e  is formed so as to protrude outward in the radial direction from a part of the outer peripheral surface of the main body  22   a . When the drive ring  22  is rotationally driven to a certain position during the opening or closing of the aperture blades  23  (discussed below), the light blocker  22   e  is inserted between the light emitter and the light receiver of the photo interrupter  29   a , and blocks the light emitted from the light emitter toward the light receiver (see  FIG. 14 ). Consequently, information about the rotational position of the drive ring  22  is sensed by the photo interrupter  29   a.    
     The aperture blades (movable blades)  23  are disposed downstream of the drive ring  22  in the light incident direction, as shown in  FIG. 2 . The aperture blades  23  rotate about the bosses  23   b  (first main shafts) (see  FIG. 10 ) between the drive ring  22  and the sheet member  24 , thereby varying the size (surface area) of the opening  23   e  (see  FIG. 4A , etc.) and adjusting the amount of light that passes through the opening of the aperture unit  20 . 
     More precisely, as shown in  FIG. 9 , the aperture blades  23  each have a main body  23   a , a boss  23   b  (first main shaft), a boss  23   c  (first auxiliary shaft), and a distal end (free end)  23   d.    
     As shown in  FIG. 9 , the main body  23   a  is a plate-like member formed in a blade shape, and is molded, for example, from LCP (liquid crystal polymer), PPS (polyphenylene sulfide), PA to (polyamide), or another such high-rigidity resin. 
     Because the aperture blades  23  are thus molded using a material having relatively high rigidity, the amount of upward warpage (discussed below) can be suppressed. 
     The bosses  23   b  (first main shafts) are provided so as to protrude from the upper surfaces (the surfaces facing the drive ring  22 ) at one end (the first end) of each main body  23   a , and serve as rotation shafts when the aperture blades  23  rotate. The bosses  23   b  (first main shafts) are inserted into through-holes formed in the center of the protrusions  22   c  of the drive ring  22 , as described above. Accordingly, the bosses  23   b  (first main shafts) move in the circumferential direction when the drive ring  22  is rotationally driven in the opening or closing of the aperture blades  23  (discussed below). 
     The bosses  23   c  (first auxiliary shafts) are provided so as to protrude from the surfaces of the main body  23   a  on the opposite side from the bosses  23   b  (first main shafts) (the surfaces facing the cover  25 ). The bosses  23   c  (first auxiliary shafts) are inserted into cam grooves  25   c  (see  FIG. 10 ) formed in the cover  25  (discussed below). Accordingly, the bosses  23   c  (first auxiliary shafts) move while being guided by the cam grooves  25   c  when the drive ring  22  is rotationally driven and the aperture blades  23  move in the circumferential direction in the opening or closing operation of the aperture blades  23  (discussed below). Consequently, the amount of light that passes through the opening of the aperture unit  20  can be adjusted by varying the amount of rotation of the aperture blades  23  according to the amount of rotation of the drive ring  22 , and thereby changing the surface area of the opening  23   e  formed by the aperture blades  23 . When the drive ring  22  is rotationally driven, the relative positions of the bosses  23   b  (first main shafts) and the bosses  23   c  (first auxiliary shafts) with respect to the base plate  21  or the cover  25  change, the aperture blades  23  rotated around the bosses  23   b  (first main shafts), and the size of the opening of the aperture unit  20  changes. 
     The distal ends  23   d  are free ends provided on the other end (second end) side of the main body  23   a , and when the aperture blades  23  rotate around the bosses  23   b  (first main shafts), these distal ends  23   d  either move out into the opening so as to cover the opening, or retract from the opening. 
     The configuration of the aperture blades  23  and the opening/closing mechanism for rotating these blades will be described in detail below. In this embodiment, eleven aperture blades  23  are provided, for example. 
     As shown in  FIG. 2 , the sheet member  24  is a substantially annular member disposed downstream of the aperture blades  23  in the light incident direction, and has a substantially annular main body  24   a  and an opening  24   b  formed in the center thereof. The sheet member  24  has through-grooves  24   c  of the same shape in the portion overlapping the cam grooves  25   c  (see  FIG. 10 ) formed in the cover  25  disposed on the downstream side in the light incident direction. 
     As shown in  FIG. 2 , the cover (second frame)  25  is a substantially annular member disposed downstream of the sheet member  24  in the light incident direction, and as shown in  FIG. 10 , has a substantially annular main body  25   a , an opening  25   b , cam grooves  25   c , a wall (second wall)  25   d , and a protrusion (support, second support)  25   e.    
     As shown in  FIG. 10 , the main body  25   a  is a substantially annular plate-shaped member, and has the opening  25   b  formed in its center. 
     The opening  25   b  is an opening through which the light of the aperture unit  20  passes, and has a surface area equal to or slightly larger than that of the opening  23   e  formed when the aperture blades  23  are fully opened. 
     The cam grooves  25   c  are guide grooves formed in the main body  25   a , and the above-mentioned bosses  23   c  (first auxiliary shafts) of the aperture blade  23  are inserted therein. Therefore, the cam grooves  25   c  are formed in the same number as the aperture blades  23  (eleven in this embodiment). When the drive ring  22  is rotationally driven and the aperture blades  23  move in the circumferential direction, the bosses  23   c  (first auxiliary shafts) move along the cam grooves  25   c , whereby each of the plurality of aperture blades  23  is rotated. 
       FIG. 11  shows a state in which only one aperture blade  23  has been disposed with its boss  23   c  (first auxiliary shaft) inserted into the cam groove  25   c , and  FIG. 12  shows the state when FIG.  11  is viewed from the AA direction in the drawing. For the sake of simplicity, the sheet member  24  is not shown in  FIG. 11 . 
     In this state, the boss  23   c  (first auxiliary shaft) is inserted into the cam groove  25   c  as shown in  FIG. 13 , which is a detail view of the B portion in  FIG. 12 , and moves along the cam groove  25   c  along with the rotation of the drive ring  22 . 
     The wall  25   d  is a wall-shaped member disposed so as to cover a part of the outer peripheral portion of the main body  25   a , and constitutes an oil intrusion prevention structure (discussed below) (see  FIG. 20 , etc.). 
     The protrusion  25   e  is an annular portion disposed on the inner peripheral side of the upper surface of the main body  25   a  (the surface facing the aperture blades  23  and the sheet member  24 ), and is formed to protrude from the upper surface of the main body  25   a . The protrusion  25   e  formed in an annular shape is disposed substantially concentrically with the opening  25   b . The protrusion  25   e  comes into contact with a part of the aperture blades  23 , and supports the aperture blades  23  from the opposite side from the subject side. 
     More specifically, as shown in  FIG. 11 , the protrusion  25   e  is disposed at a position closer to the bosses  23   b  (first main shafts) serving as the rotation shafts of the aperture blades  23  disposed on the cover  25 . The protrusion  25   e  supports the aperture blades  23  at a position closer to the bosses  23   b  (first main shafts) of the aperture blades  23 . 
     In an open state in which the aperture blades  23  are accommodated in the gap between the base plate  21  and the cover  25 , the protrusion  25   e  is disposed at a position where three aperture blades  23  overlap. 
     On the other hand, since the protrusions  22   c  on the drive ring  22  side are provided near the rotation shafts (the bosses  23   b  (first main shafts)) of the aperture blades  23 , they are disposed at a position overlapping one aperture blade  23  regardless of the rotation position of the aperture blades  23 . 
     Accordingly, the protrusion  25   e  is formed to have a lower protruding height than the protrusions  22   c  so that the three aperture blades  23  can move easily. 
     The protrusion  25   e  (second support) is formed on the cover (second frame)  25 , and is located near the opening of the aperture unit  20  or the opening  25   b  (second opening) of the cover (second frame)  25 . Furthermore, the protrusion  25   e  (second support) is located outside the opening  27   b  of the fixed opening sheet  27  that determines the opening diameter or opening surface area of the aperture unit  20  when the aperture blades  23  are fully open, that is, on the side away from the center of the opening. 
     Furthermore, the protrusion  25   e  (the second support) is provided so as to be located more to the center axis side of the opening of the aperture unit  20  or the opening  25   b  (the second opening) of the cover (second frame)  25 , than the protrusions  22   c  (first supports) of the drive ring  22 , and to be in contact with the surface on the same side as the direction of upward warpage of the aperture blades  23 . 
     Furthermore, the protrusion  25   e  (second support) is provided in an annular shape with respect to the center axis of the opening of the aperture unit  20  or the opening  25   b  (second opening) of the cover (second frame)  25 . 
     Furthermore, the protrusion  25   e  (second support) preferably has a substantially arced shape, a substantially elliptical shape, a substantially parabolic shape, a substantially multidimensional curve shape, or a gentle curved shape in a cross section that includes the center axis of the opening of the aperture unit  20  or the opening  25   b  (second opening) of the cover (second frame)  25 . 
     With these configurations, the aperture blades  23  can be smoothly moved without an increase in the drive load due to abrasion or catching, and at the same time, upward warpage due to the weaving together of the aperture blades can be efficiently suppressed. 
     As shown in  FIG. 4A , etc., three attachment screws  26  are provided in order to fix the cover  25  to the base plate  21  from the downstream side of the cover  25  in the light incident direction as shown in  FIG. 2 . 
     As shown in  FIG. 2 , the fixed opening sheet (fixed opening member)  27  is disposed on the downstream side of the cover  25 , that is, the furthest downstream from the aperture unit  20 , in the light incident direction. The fixed opening sheet  27  has a substantially annular main body  27   a  and an opening  27   b  formed in the center portion of the main body  27   a , and is provided in order to define the diameter or surface area of the opening when the aperture unit  20  is in its fully open state. The fixed opening sheet  27  is fixed to the surface of the cover  25  on the opposite side from the subject side. 
     The drive motor  28  is fixed to the base plate  21  by an attachment screw  28   b  (see  FIGS. 2 and 4A ) in order to impart a drive force to the aperture blades  23  when performing the opening and closing of the aperture blades  23 . The drive motor  28  is electrically connected to an FPC  29   b  (discussed below), and its rotation shaft is rotated by power supplied from an electrical circuit (not shown). 
     More specifically, the drive motor  28  rotates the gear  28   a  press-fitted to the rotation shaft, and thereby rotates the drive ring  22  around the optical axis X via the gear  22   d  disposed so as to mesh with the gear  28   a.    
     The photo interrupter  29   a  has a light emitter and a light receiver, and is provided in order to sense the rotational position of the drive ring  22 . The photo interrupter  29   a  is attached to the upper surface of the cover  25  (the surface on the subject side) as shown in  FIG. 14 . 
     The FPC  29   b  is a flexible printed circuit board, and as shown in  FIGS. 2 and 3 , electrically connects the photo interrupter  29   a  and the drive motor  28 , and is connected to an electric circuit (not shown) via a connector. The FPC  29   b  is attached to the upper surface of the base plate  21  (the surface on the subject side), as shown in  FIGS. 3 and 4 . 
     Opening/Closing Mechanism of Aperture Blades  23   
     The mechanism for opening and closing the eleven aperture blades  23  in the aperture unit  20  of this embodiment will now be described. 
     As described above, the aperture unit  20  in this embodiment rotates the eleven aperture blades  23  around their respective bosses  23   b  (first main shafts), thereby changing the surface area of the opening  23   e  formed in the center portion of the eleven aperture blades  23 . 
     More specifically, the bosses  23   b  (first main shafts) of the eleven aperture blades  23  are inserted into the through-holes in the centers of the protrusions  22   c  formed on the drive ring  22 . Meanwhile, the bosses  23   c  (first auxiliary shafts) of the aperture blades  23  are inserted into the cam grooves  25   c  formed in the cover  25 , as shown in  FIGS. 12 and 13 . 
     Here, when the bosses  23   c  (first auxiliary shafts) are in the position shown in  FIG. 13 , the aperture blades  23  are in their open state in which the opening  23   e  is the largest, as shown in  FIGS. 6A and 6B . Then, as the bosses  23   c  (first auxiliary shafts) move to the right along the cam grooves  25   c  shown in  FIG. 13 , the distal ends  23   d  of the aperture blades  23  rotates inward in the radial direction, and the surface area or the diameter of the opening  23   e  steadily decreases as shown in  FIGS. 5A and 5B . When the bosses  23   c  (first auxiliary shafts) move to the vicinity of the right ends of the cam grooves  25   c , the aperture blades  23  transition to a constricted state (closed state) in which the opening  23   e  is the smallest, as shown in  FIGS. 4A and 4B . 
     The drive ring  22  is rotated around the optical axis X when the rotational drive force of the drive motor  28  is transmitted to the gear portion  22   d  via the gear  28   a . Rotational position information about the drive ring  22  is sensed when the light blocker  22   e  provided integrally to the outer peripheral portion of the drive ring  22  passes through the photo interrupter  29   a . This allows for adjustment of the opening diameter or opening surface area of the opening  23   e  of the aperture blades  23 . 
     As shown in  FIG. 14 , the drive ring  22  is rotationally driven by the drive motor  28  in a state in which the bosses  23   c  (first auxiliary shafts) of the aperture blades  23  are inserted into the cam grooves  25   c  of the cover  25 , and the bosses  23   b  (first main shafts) into the through-holes of the drive ring  22 , there is movement in the circumferential direction along with the drive ring  22 , and the rotation matches the movement of the bosses  23   c  (first auxiliary shafts) along the cam grooves  25   c , with the bosses  23   b  (first main shafts) serving as the rotation shafts. 
     This allows the surface area or the diameter of the opening  23   e  formed by the aperture blades  23  to be adjusted smaller or larger. 
     Structure for Suppressing Upward Warpage of Aperture Blades  23   
     The aperture unit  20  in this embodiment comprises an upward warpage suppression structure in order to suppress upward warpage to the side on which the distal ends  23   d  of the aperture blades  23  are woven together when the aperture blades  23  are closing, as shown in  FIG. 15A . This upward warpage suppression structure will now be described with reference to  FIGS. 15A to 16B . 
     As shown in  FIGS. 15A and 15B , the aperture blades  23  undergo upward warpage to the image plane side such that the woven-together portions of the distal ends  23   d  of the aperture blades  23  rise up as the opening diameter constricts. 
     At this point, if the aperture blades  23  are in such a warped state, there is the risk, for example, that they may come into contact with the lens L 5  or the like disposed opposite from them, and that this will leave a contact mark on the lens L 5  or the like. Furthermore, there is the risk that this upward warpage will cause the center position of the opening  23   e  formed by the aperture blades  23  to shift, and that the position on the optical axis X will be shifted, the result being that the designed optical performance cannot be exhibited. 
     In view of this, the aperture unit  20  in this embodiment comprises a structure for suppressing the upward warpage of the aperture blades  23  with a simple configuration, without increasing the number of parts. 
     More specifically, as shown in  FIGS. 16A and 16B , in the upward warpage suppression structure of this embodiment, the two protrusions  22   c  and  25   e  are disposed on the surface of the ring  22  and the cover  25  facing the aperture blades  23 , in order to suppress upward warpage when the aperture blades  23  are woven together. 
     The protrusions  22   c  and  25   e  are disposed on the drive ring  22  and the cover  25 , respectively, so as to hit part of the aperture blades  23 . The protrusions  22   c  and  25   e  respectively support the aperture blades  23  in the direction of suppressing upward warpage when the aperture blades  23  are woven together. 
     As mentioned above, eleven protrusions  22   c , the same number as that of the aperture blades  23 , are provided on the surface of the drive ring  22  facing the aperture blades  23 . The protrusions  22   c  are disposed around all the holes into which the bosses  23   b  (first main shafts) of the eleven aperture blades  23  are inserted. As shown in  FIG. 16A , the protrusions  22   c  support the vicinity of the bases of the aperture blades  23  (the vicinity of the bosses  23   b ) from the subject side. 
     As described above, the protrusion  25   e  is provided in an annular shape on the surface of the cover  25  facing the aperture blades  23 . As shown in  FIG. 16A , the protrusion  25   e  supports the portions near the center of the aperture blades  23 , on the opposite side from the subject side. 
     Consequently, in a state in which the aperture blades  23  have constricted (a state in which the opening diameter is reduced), the aperture blades  23  can hit the protrusions  22   c  and  25   e  to restrict deformation of the aperture blades  23 . 
     Thus, with the configuration of the aperture unit  20  (solid line) in this embodiment, the amount of upward warpage of the aperture blades  23  toward the downstream side can be suppressed more effectively as compared to the aperture blade position in a configuration in which the protrusions  22   c  and  25   e  are not provided, as shown by the broken line in  FIG. 16B . 
     As a result, it is possible to prevent problems attributable to the fact that the distal ends  23   d  of the aperture blades  23  hit the lens L 5  or the like disposed downstream of the aperture unit  20  in the light incident direction. 
     Furthermore, with the aperture unit  20  in this embodiment, as shown in  FIG. 17A , a spacer  25   f  (part of the cover  25 ) is provided between the aperture blades  23  and the fixed opening diameter of the aperture unit  20  defined by the fixed opening sheet  27  (see  FIG. 20 ). That is, the fixed opening sheet  27  that defines the fixed opening diameter of the aperture unit  20  is disposed so that a part of the cover  25  and the spacer  25   f  are sandwiched between the aperture blades  23  and the fixed opening sheet  27 . 
     Here, as shown in  FIG. 17A , the amount of upward warpage of the aperture blades  23  increases as the aperture blades  23  are rotated in the direction of constriction, toward the downstream side in the light incident direction, that is, toward the weaving side. 
     Thus, as the warped portions of the aperture blades  23  are rotated from the substantially open state shown in  FIG. 17B  in the direction in which the aperture blades  23  are constricted, as shown in  FIG. 17A , there is movement to a position beyond the extension line Y 2  to the inside in the radial direction of the protrusion  25   e  (second support) of the cover  25 , and beyond the extension line Y 1  to the inside in the radial direction of the fixed opening sheet  27  (fixed opening diameter). At this point, the aperture blades  23  come into contact with the protrusion  25   e , and the position in the optical axis X direction is restricted. 
     As described above, with the aperture unit  20  in this embodiment, when the aperture blades  23  are in a substantially open state as shown in  FIG. 17B , they are disposed upstream in the light incident direction from the position of the fixed opening diameter defined by the fixed opening sheet  27 . As the aperture blades  23  then rotate in the direction of constricting, as shown in  FIG. 17A , the distal end portions  23   d  of the aperture blades  23  warp upward toward the downstream side in the light incident direction, and go beyond the position of the fixed opening diameter (extension line Y 1 ). 
     Consequently, from the state in which the opening  23   e  formed by the aperture blades  23  is at its largest to the state in which the opening  23   e  is at its smallest ( FIG. 17A ), the opening  23   e  of the aperture blades  23  can be disposed near the position of the extension line Y 1  of the fixed opening diameter defined by the fixed opening sheet  27  in the light incident direction. 
     When the aperture blades  23  move in the direction of reducing the size of the opening  23   e  (third opening), the aperture blades  23  are moved in the same direction as the upward warpage so as to go beyond the imaginary plane constituting the opening  27   b  formed by the movable opening sheet  27  (fixed opening member) as the amount of upward warpage increases. 
     When the aperture blades  23  are in the fully opened state of the opening  23   e  (third opening), the fixed opening sheet  27  and the aperture blades  23  are in a state in which gaps are provided between them and they are not in contact with each other, and when the aperture blades  23  move in the direction of reducing the size of the third opening  23   e , the aperture blades  23  approach the fixed opening sheet  27  as the amount of upward warpage increases. 
     When the aperture blades  23  move such that the size of the opening  23   e  (third opening) goes from its largest to its smallest, that is, from fully open to tightly constricted, the distal ends  23   d  of the aperture blades  23  pass through three regions as the amount of upward warpage increases in the optical axis X direction. 
     The first region is a region on the opposite side from the direction of upward warpage from the extension line Y 2 , the second region is a region between the extension line Y 2  and the extension line Y 1 , and the third region is a region on the upward warpage direction side of the extension line Y 1 . The spacer  25   f  of the cover  25  is configured between the extension line Y 2  and the extension line Y 1 , and forms the second region. 
     By providing the second region, even if the amount of upward warpage of the aperture blades  23  is large, some of the upward warpage to the inside of the aperture unit  20  in the optical axis X direction, that is, to the inside of the fixed opening sheet  27  in the optical axis X direction, can be absorbed and accommodated, so the aperture blades  23  are less likely to protrude outside of the aperture unit  20  in the optical axis X direction. 
     The second region is preferably thick in the optical axis X direction in order to minimize the amount of upward warpage, but if the second region is too thick, the aperture unit  20  ends up being too large. Therefore, the second region is preferably approximately equal to the size in the optical axis X direction of the blade chamber in which the aperture blades  23  are accommodated, or between approximately equal and approximately twice the size, or between approximately equal and approximately three times the size. Furthermore, when the aperture unit size is prioritized, the second region may be approximately half of the size in the optical axis X direction of the blade chamber in which the aperture blades  23  are accommodated, or between approximately half and approximately the same size, or between approximately half and approximately twice the size. 
     Thus, it is possible to prevent the position of the fixed opening diameter and the position of the aperture opening of the aperture blades  23  from being disposed at positions that are apart in the light incident direction. 
     Foreign Matter Intrusion Prevention Structure 
     The aperture unit  20  of this embodiment comprises a foreign matter intrusion prevention structure for preventing grease, foreign matter, and the like from entering the gap between the base plate  21  and the cover  25 . This foreign matter intrusion prevention structure will be described below with reference to  FIGS. 18 to 20 . 
     The foreign matter intrusion prevention structure is constituted by a wall (second wall)  25   d  disposed on the outer peripheral side of the cover  25  shown in  FIG. 18 , and a wall (first wall)  21   c  disposed on the outer peripheral side of the base plate  21  shown in  FIG. 19 . 
     As shown in  FIG. 19 , the wall  21   c  is disposed so as to cover part of the outer peripheral portion of the annular main body  21   a  of the base plate  21 . 
     As shown in  FIGS. 10 and 18 , the wall  25   d  is a wall-shaped member erected on a part of the main body  25   a  along the outer periphery thereof, and is disposed at a position that overlaps the wall  21   c  on the base plate  21  side. 
     With the aperture unit  20  in this embodiment, the foreign matter intrusion prevention structure is disposed on the outer peripheral side where grease infiltration is a concern, in order to prevent grease, foreign matter, or the like from coming into contact with the aperture blades  23  that move in the gap between the base plate  21  and the cover  25 . 
     Here, the aperture unit  20  has a configuration in which the aperture blades  23  are sandwiched between the cover  25  and the base plate  21  in order to accommodate the aperture blades  23  and hold them in the optical axis X direction. 
     With this configuration, since a gap is formed between the base plate  21  and the cover  25 , when a part to which grease or a foreign substance has adhered is disposed near the aperture unit  20 , there is the risk that this grease or the like will stick to the aperture unit  20  and find its way into the interior of the aperture unit  20  through the gap. For instance, if grease that has come in through the gap sticks to the aperture blades  23 , the drive load of the aperture blades  23  may increase so much that the blades will not rotate smoothly. 
     With the aperture unit  20  in this embodiment, the wall  21   c  and the wall  25   d  are provided to the portions where grease or the like is likely to adhere. More specifically, the wall  25   d  is provided to the cover  25 , and the wall  21   c  is provided to the base plate  21 . 
     The wall  21   c  and the wall  25   d  have a staggered overlapping structure in which they are provided on the upstream side and the downstream side in the light incident direction, respectively. This eliminates a gap that can be seen from the outer peripheral side of the aperture unit  20 , and has the walls  21   c  and  25   d  disposed in a staggered layout, so it effectively prevents foreign substances such as grease from sticking to the aperture blades  23 . 
     Also, the effect of preventing foreign matter such as grease from entering can be further improved by applying an oil-repellent component such as an oil barrier to a portion of the staggered structure constituted by the wall  25   d  and the wall  21   c.    
     Embodiment 2 
     The aperture unit (light shielding unit)  120  according to Embodiment 2 of the present disclosure will now be described with reference to  FIGS. 21A to 25 . 
     The aperture unit  120  in this embodiment differs from the configuration of Embodiment 1 above in that it comprises aperture blades (movable blades, second blades)  123  having a different shape in addition to the aperture blades  23  described in Embodiment 1 above. 
     Components having the same functions and shapes as those Embodiment 1 above will be numbered the same and will not be described again. 
     That is, with the aperture unit  120  in this embodiment, the six aperture blades (movable blades, first blades)  23  shown in  FIG. 21A  and the five aperture blades  123  shown in  FIG. 21B  combine to form an aperture opening (third opening)  123   e.    
     As shown in  FIG. 21A , the aperture blades  23  each have a main body  23   a , a boss  23   b  (first main shaft), a boss  23   c  (first auxiliary shaft), and a distal end  23   d . Since these components are the same as those in Embodiment 1 above, they will not be described again here. 
     As shown in  FIG. 21B , the aperture blades  123  have a greater overall length than the aperture blades  23 , and each has a main body  123   a , a boss  123   b  (second main shaft), a boss  123   c  (second auxiliary shaft), and a rotating portion  123   d.    
     As shown in  FIG. 21B , the main body  123   a  is a plate-shaped member, and is molded from a high-rigidity resin such as LCP (liquid crystal polymer), PPS (polyphenylene sulfide), or PA (polyamide). 
     Since the aperture blades  123  are thus formed using a material having relatively high rigidity, the amount of upward warpage of the alternately disposed aperture blades  23  can be suppressed. 
     The boss  123   b  (second main shaft) is provided protruding from the upper surface (the surface facing the drive ring  22 ) at one end (first end) of the main body  123   a , serving as the rotation shaft when the aperture blade  123  rotates. The boss  123   b  (second main shaft) is inserted into a through-hole formed at the center portion of the protrusion  22   c  on the drive ring  22  described above. Accordingly, the bosses  123   b  (second main shafts) move in the circumferential direction along with the rotational drive of the drive ring  22  during the opening or closing of the aperture blades  123  (discussed below). 
     The bosses  123   c  (second auxiliary shafts) are provided so as to protrude from the surface (the surface facing the cover  25 ) of the main body  123   a  on the opposite side form the bosses  123   b  (second main shafts). The bosses  123   c  (second auxiliary shafts) are inserted into the cam grooves  25   c  (see  FIG. 10 ) formed in the cover  25  (discussed below). Accordingly, when the drive ring  22  is rotationally driven and the aperture blades  123  move in the circumferential direction during the opening or closing of the aperture blades  123  (discussed below), the bosses  123   c  (second auxiliary shafts) move while being guided by the cam grooves  25   c . Consequently, the amount of light passing through the open portion of the aperture unit  120  can be adjusted by varying the amount of rotation of the aperture blades  123  according to the amount of rotation of the drive ring  22 , and thereby varying the surface area or diameter of the opening  123   e  formed by the aperture blades  123 . When the drive ring  22  is rotationally driven, the relative positions of the bosses  123   b  (second main shafts) and the bosses  123   c  (second auxiliary shafts) with respect to the base plate  21  or the cover  25  change, and the aperture blades  123  move rotate around the bosses  123   b  (second main shafts), changing the size of the opening of the aperture unit  20 . 
     The rotating portion  123   d  is provided on the other end (second end) side of the main body  123   a , and when the aperture blade  123  rotates around the boss  123   b  (second main shaft), the rotating portion  123   d  moves in the gap between the base plate  21  and the cover  25 . 
     With the aperture unit  120  in this embodiment, the aperture blades  23  and  123  having different shapes are alternately disposed in the circumferential direction. 
     Here, when the aperture blades  23  rotate to a state in which the opening diameter of the opening  123   e  is at its smallest (closed state), the distal ends  23   d  move from between the base plate  21  and the cover  25  to near the optical axis X, as shown in  FIGS. 22A and 22B . 
     At this point, as shown in  FIG. 24A , the aperture blades  23  are driven open or closed when the bosses  23   c  (first auxiliary shafts) move in the cam grooves  25   c  provided to the cover  25 , with the bosses  23   b  (first main shafts) inserted into the through-hole formed in the center of the protrusions  22   c  provided to the drive ring  22  serving rotation shafts. 
     Meanwhile, when the aperture blades  123  rotate to a state in which the opening diameter of the opening  123   e  is at its smallest (closed state), the rotating portions  123   d  rotate within the gap between the base plate  21  and the cover  25 , without coming out from the gap between the base plate  21  and the cover  25 , as shown in  FIGS. 23A and 23B . Accordingly, in any state in which the aperture blades  123  have rotated to reduce the opening diameter of the opening  123   e , the two ends thereof do not come out of the gap between the base plate  21  and the cover  25 . That is, the aperture blades  123  are in a state in which their two ends are always held between the base plate  21  and the cover  25 , so the position in the light incident direction is stabilized. 
     Therefore, unlike the aperture blades  23 , even in a state in which the aperture blades  123  have constricted to reduce the opening diameter of the opening  123   e , there is no upward warpage to the downstream side in the light incident direction in the aperture blades  123  by themselves. 
     At this point, just as with the aperture blades  23 , the aperture blades  123  are driven open and closed when the bosses  123   c  (second auxiliary shafts) move along the cam grooves  25   c  provided to the cover  25 , with the bosses  123   b  (second main shafts) inserted into the through-holes formed in the center of the protrusions  22   c  provided to the drive ring  22  serving as rotation shafts. 
     As described above, the aperture unit  120  in this embodiment is configured such that the aperture blades  23  shown in  FIG. 21A  and the aperture blades  123  shown in  FIG. 21B  are combined so as to be disposed alternately in the circumferential direction. 
     Consequently, as shown in  FIG. 25 , even when the six aperture blades  23  and the five aperture blades  123  have been rotated so that the opening diameter of the opening  123   e  of the aperture unit  120  is at its smallest, the amount of upward warpage toward the downstream side in the light incident direction can be suppressed. 
     Furthermore, using a combination of the aperture blades  23  and the aperture blades  123  as in this embodiment allows the drives load exerted on the drive motor  28 , which is necessary for moving the rotating portion  123   d  in the gap between the base plate  21  and the cover  25 , can be reduced as compared to a configuration in which the opening  123   e  is formed using just the aperture blades  123 , for example. 
     With the configuration of the aperture unit  120  in this embodiment, as described above, the aperture blades  23  and the aperture blades  123  are used in combination, so that the amount of upward warpage of the aperture blades  23  to the downstream side in the light incident direction can be suppressed, and the load on the drive motor  28  can be reduced. 
     With the aperture unit  120  in this embodiment, as in Embodiment 1 above, the two protrusions  22   c  and  25   e  provided to the base plate  21  and the cover  25 , respectively, hit a part of the aperture blades  23  and  123 , allowing the amount of upward warpage of the aperture blades  23  and  123  to be suppressed. 
     However, as in this embodiment, when using a combination of the aperture blades  23  and  123  having different shapes, the aperture blades  123  have the function of suppressing the upward warpage of the aperture blades  23 , and therefore the aperture unit  120  in this embodiment may have a configuration that does not include the two protrusions  22   c  and  25   e  described in Embodiment 1 above. 
     Other Embodiments 
     Embodiments of the present disclosure were described above, but the present disclosure is not limited to or by the above embodiments, and various modifications are possible without departing from the gist of the disclosure. 
     (A) 
     In Embodiments 1 and 2 above, an example was described in which a plurality of the flat aperture blades  23  and  123  were combined to adjust the surface area or the diameter of the openings  23   e  and  123   e . However, the present disclosure is not limited to this. 
     For instance, as shown in  FIG. 26 , an aperture unit (light shielding unit)  220  may be configured using aperture blades  223  having a shape that bends toward (upward in the drawing) the surface on which the boss  223   b  is provided (the surface facing the drive ring  22 ), starting from a bent portion  223   f  formed at a position near the base (boss  223   b ) of the main body  223   a.    
     That is, with this configuration, as shown in  FIG. 26 , the aperture blade  223  has a shape that is bent ahead of time in the opposite direction from that of upward warpage due to blade weaving. Therefore, even in a state in which the aperture blades  223  are closed, that is, when the blades have transitioned to a state in which the opening diameter or the surface area of the opening  223   e  is reduced, the amount of upward warpage can be more effectively suppressed than when using the aperture blades  23  in Embodiment 1 above (solid line), as indicated by the broken line in  FIG. 27 . 
     The direction in which the individual aperture blades are bent is not limited to the direction shown in  FIG. 26 , and with a configuration in which the side where the distal ends of the aperture blades are woven together is disposed on the opposite side (the subject side), the blades may be bent in the opposite direction from that in  FIG. 26 , that is, to the subject side. 
     With the aperture unit  220  in this embodiment, just as in Embodiment 1 above, the two protrusions  22   c  (first support) and  25   e  (second support) provided to the base plate  21  and the cover  25 , respectively, will hit a part of the aperture blades  223 , thereby suppressing the amount of upward warpage of the aperture blades  223 . 
     However, using the aperture blades  223  having a pre-bent shape as in this embodiment gives the aperture blades  223  themselves an upward warpage suppressing effect, so the aperture unit  220  in this embodiment may be configured not to include the two protrusions  22   c  and  25   e  described in Embodiment 1 above. 
     (B) 
     In Embodiments 1 and 2 above, an example of an aperture unit (light shielding unit) was described in which, in a state in which the aperture blades  23  and  123  are constricted (a state in which the opening diameter or the surface area is reduced), the aperture blades  23  and  123  warp upward toward the downstream side (image plane side) in the light incident direction. However, the present disclosure is not limited to this. 
     For instance, the aperture unit may be configured such that in their constricted state the aperture blades warp upward toward the upstream (subject side) in the light incident direction. The side where the distal ends of the aperture blades are woven together may be the subject side. 
     (C) 
     In Embodiments 1 and 2 above, an example was given of a configuration in which the protrusions  22   c  (first support) and  25   e  (second support) are provided to hit part of the aperture blades  23  and  123  and to suppress the upward warpage of the aperture blades  23  and  123  when the open portions of the aperture units  20  and  120  are closed. However, the present disclosure is not limited to this. 
     For instance, the support for suppressing the upward warpage of the aperture blades in the closed state of the open portions of the aperture units may be a flat member instead of a protruding shape. That is, the shape of the support does not need to be one that protrudes, and the support may be any member that supports the support in the direction of suppresses upward warpage. 
     (D) 
     In Embodiments 1 and 2 above, an example was given of a configuration in which the drive ring  22  and the cover  25  are respectively provided with the protrusions  22   c  (first support) and  25   e  (second support) as supports for suppressing upward warpage of the aperture blades  23  and  123  in the closed state of the opening portions of the aperture units  20  and  120 . However, the present disclosure is not limited to this. 
     For instance, the configuration may be such that just one of the protrusions  22   c  (first support) and  25   e  (second support) is provided as a support for suppressing upward warpage of the aperture blades when the opening portion of the aperture units are closed. 
     (E) 
     In Embodiments 1 and 2 above, an example was given in which the plurality of annular protrusions  22   c  provided along the circumferential direction on the substantially annular drive ring  22  are used as supports (first supports). However, the present disclosure is not limited to this. For instance, the shape of the support (first support) is not limited to an annular protrusion, and may be some other shape such as a columnar shape or a polygonal shape. 
     (F) 
     In Embodiments 1 and 2 above, an example was given in which the plurality of annular protrusions  22   c  provided along the circumferential direction on the substantially annular drive ring  22  are used as supports (first supports). However, the present disclosure is not limited to this. 
     For instance, rather than going through, the holes in the drive ring  22  (drive ring) may have a bottom portion (first support) constituting the surface facing the aperture blades  23  side, that is, the surface that is across from the distal ends of the rotation shafts (first main shafts), and the bottom portion (first support) supports by hitting the distal ends of the rotation shafts (first main shafts). 
     In this case, the bottom (first support) is configured in a concave shape from the surface of the drive ring  22  (drive ring). The shape of the distal ends of the rotation shafts (first main shafts), or of the bottom portions (first supports), may be a flat shape, a spherical surface, a conical surface, some other rotationally symmetric surface, a polygonal pyramid shape, or the like. 
     (G) 
     In Embodiments 1 and 2 above, an example was given in which a single annular protrusion  25   e  provided on the inner diameter side of the substantially annular cover  25  is used as a support (second support). However, the present disclosure is not limited to this. 
     For instance, a plurality of arc-shaped or linear protrusions formed along the rotation path of the aperture blades may be used as the support (second support). 
     (H) 
     In Embodiments 1 and 2 above, as an example of a blade drive mechanism, an example was described in which the bosses  23   b  (first main shafts) and  123   b  (second main shafts) functioning as rotation shafts are provided on the aperture blades  23  and  123  side, and through-holes into which the bosses  23   b  (first main shafts) and  123   b  (second main shafts) are inserted are provided on the drive ring side. However, the present disclosure is not limited to this. 
     For instance, the configuration may be such that the rotation shafts are provided on the drive ring side, and holes  23  (first main holes) and holes  123  (second main holes) into which the rotary shafts are inserted are provided on the aperture blades  23  and  123  side. 
     In this case, protrusions (first supports) are disposed at substantially equal angular intervals in the circumferential direction so as to protrude in an annular shape from the surface of the main body that is in contact with the opposite surface from the direction of upward warpage of the aperture blades, the opposite side from the subject side (the cover  25  side), that is, from the surface on the image plane side. The protrusions hit a part of the aperture blades at the annular portion, and support the aperture blades from the subject side. 
     Also, rotation shafts are formed in the approximate center of the annularly protruding portions of the protrusions (first support), and are inserted into holes (first main holes) in the aperture blade. The protrusions (first support) are configured in a convex shape from the surface of the drive ring, and support the vicinity of the rotation shafts. 
     Therefore, the blade driving mechanism is not limited to the bosses  23   b  (first main shafts) and  123   b  (second main shafts) on the side of the aperture blades  23  and  123 , and the through-holes into which the bosses  23   b  (first main shafts) and  123   b  (second main shafts) on the side of the drive ring  22  are inserted. Any drive mechanism may be used as long as the movable blades and the drive ring are engaged, and drive force is transmitted to the movable blades as the drive ring is rotationally driven. 
     (I) 
     In Embodiments 1 and 2 above, as an example of the cam mechanism, an example was described in which the bosses  23   c  (first auxiliary shafts) and  123   c  (second auxiliary shafts) that move along the cam grooves  25   c  are provided on the aperture blades  23  side, and the cam grooves  25   c  into which the bosses  23   c  (first auxiliary shafts) and  123   c  (second auxiliary shafts) are inserted are provided on the cover  25  side. However, the present disclosure is not limited to this. 
     For instance, the configuration may be such that cam grooves  23  (first auxiliary holes) and cam grooves  123  (second auxiliary holes) are provided on the aperture blades  23  and  123  side, and bosses that move along the cam grooves are provided on the cover side. 
     In the opening or closing operation of the aperture blades, when the drive ring is rotationally driven and the aperture blades move in the circumferential direction, this is accompanied by movement of the cam grooves (first auxiliary holes and second auxiliary holes) on the aperture blade side while being guided by the bosses on the cover side. 
     Consequently, the amount of light passing through the opening portion of the aperture unit  20  can be adjusted by varying the amount of rotation of the aperture blades according to the amount of rotation of the drive ring, and thereby varying the surface area or the diameter of the opening  23   e  formed by the aperture blades. 
     When the drive ring is rotationally driven, the relative positions of the bosses  23   b  (first main shafts) and  123   b  (second main shafts) and the cam grooves  23  (first auxiliary holes) and the cam grooves  123  (second auxiliary holes) with respect to the base plate  21  or the cover  25  are changed, the aperture blades rotate around the bosses  23   b  (first main shafts), and the size of the opening of the aperture unit  20  changes. 
     (J) 
     In Embodiments 1 and 2 above, as an example of the cam mechanism, an example was described in which through-holes into which the bosses  23   b  (first main shafts) and  123   b  (second main shafts) of the aperture blades  23  and  123  are inserted are provided on the drive ring  22  side, and the cam grooves  25   c  into which the bosses  23   c  (first auxiliary shafts) the bosses  123   c  (second auxiliary shafts) are inserted are provided on the cover  25  side. However, the present disclosure is not limited to this. 
     For instance, the configuration may be such that the cam grooves are provided on the drive ring side and the through-holes are provided on the cover side. 
     In the opening or closing operation of the aperture blades, when the drive ring is rotationally driven and the aperture blades move in the circumferential direction, the aperture blades rotate around the main bosses (first main shafts and second main shafts) inserted into the through-holes of the drive ring, and the auxiliary bosses (first auxiliary shafts and second auxiliary shafts) of the aperture blades move while being guided by the cam grooves on the drive ring side. Consequently, the amount of light passing through the opening portion of the aperture unit  20  can be adjusted by varying the amount of rotation of the aperture blades according to the amount of rotation of the drive ring, and thereby varying the surface area or the diameter of the opening  23   e  formed by the aperture blades. 
     When the drive ring is rotationally driven, the relative positions of the main bosses (first main shafts and second main shafts) and the auxiliary bosses (first auxiliary shafts and second auxiliary shafts) with respect to the base plate  21  or the cover  25  change, the aperture blades rotate around the main bosses  23   b  (first main shafts and second main shafts), and the size of the opening of the aperture unit  20  changes. 
     In this case, a plurality of protrusions, which are supports (first supports), are formed along the circumferential direction on the cover and protrude in an annular shape, and through-holes are disposed in the approximate centers of these annular protrusions. The protrusions, which are supports (first supports), protrude from the cover so as to be in contact with the surface on the opposite side from the direction of upward warpage of the aperture blades. 
     The protrusions, which are supports (second supports), are formed on the base plate (first frame) or the drive ring, and are located near the opening of the aperture unit, the opening of the base plate (first frame), or the opening of the drive ring. The protrusions, which are supports (second supports), are configured as parts disposed near the opening of the aperture unit. Furthermore, the supports (second supports) are located closer to the center axis side of the opening of the aperture unit than the supports (first supports), and are provided so as to be in contact with the surface on the same side as the direction of upward warpage of the aperture blades. Furthermore, the supports (second supports) are provided in an annular shape with respect to the center axis of the opening of the aperture unit. Furthermore, the supports (second supports) have a substantially arced shape, a substantially elliptical shape, a substantially parabolic shape, a substantially multidimensional curve shape, or a gentle curved shape in a cross sectional view that includes the center axis of the opening of the aperture unit. 
     (K) 
     The cam mechanism was described in Embodiments 1 and 2 and in (I) and (J) above. However, the cam mechanism is not limited to the above. 
     For instance, any cam mechanism may be used in which either a fixed frame (the base plate  21  or the cover  25 ) or a drive ring engages with the movable blades, and the movable blades move along with the rotation of the drive ring. 
     (L) 
     In Embodiment 1 above, an example was described in which the aperture unit  20  includes eleven movable aperture blades  23 . However, the present disclosure is not limited to this. 
     For instance, the number of movable blades included in the aperture unit is not limited to eleven, and may instead be ten or fewer, or twelve or more. 
     (M) 
     In Embodiment 2 above, an example was described in which the aperture unit  120  includes six of the aperture blades  23  and five of the aperture blades  123 . However, the present disclosure is not limited to this. 
     For instance, the aperture blades of different shapes included in the aperture unit are not limited to the above number, but may instead be a combination of five and six blades, or may be the same number of each, such as five and five, or six and six. 
     Also, the aperture blades of different shapes are not limited to two types, and may instead be made up of a combination of three or more types. 
     (N) 
     In the above embodiments, an example was described in which the content of the present disclosure is applied to the aperture unit  20  (light shielding unit) mounted on an interchangeable lens type of lens barrel  10 . However, the present disclosure is not limited to this. 
     For instance, the light shielding unit is not limited to an interchangeable lens barrel, and can also be applied to a lens barrel that integrated with a camera body. 
     (O) 
     In the above embodiments, an example was described in which the content of the present disclosure is applied to the aperture unit (light shielding unit)  20  mounted on the lens barrel  10  disposed on the downstream side in the light incident direction of the fourth lens L 4  functioning as a focus lens. However, the present disclosure is not limited to this. 
     The aperture unit  20  may be disposed on the upstream side in the light incident direction of the fourth lens L 4  functioning as a focus lens. 
     In this case, the focus lens is disposed in the direction of the upward warpage of the aperture blades, and there is the risk of interference between the aperture blades and the focus lens during focusing, but if the content of the present disclosure is applied, the amount of upward warpage of the aperture blades is suppressed, so there is less risk of interference. 
     INDUSTRIAL APPLICABILITY 
     The light shielding unit disclosed herein has the effect of suppressing upward warpage of the movable blades while operating the movable blades smoothly, and can therefore be widely applied to a variety of devices such as optical devices.