JP6555064B2 - Light amount adjustment mechanism, lens barrel and camera - Google Patents

Description

  The present invention relates to a light amount adjusting mechanism, a lens barrel, and a camera.

There is an aperture mechanism having a main aperture that adjusts the amount of incident light flux to the camera according to a set aperture value, and a sub aperture that adjusts the aperture diameter to an open aperture value according to the focal length. Conventionally, the number of blades constituting the main diaphragm and the sub diaphragm is equal (see Patent Document 1).
The aperture shape of the diaphragm is preferably close to a circle. By increasing the number of blades, the opening can be made nearly circular, but when the number of blades of the main aperture is increased, the overlap of the blades when the apertures are reduced increases and the operability deteriorates.

JP 2000-250093 A

The light quantity adjusting mechanism has a plurality of first blades that form the first opening, and drives the first blade to adjust the size of the first opening according to the aperture value. And a plurality of second blades forming a second opening, and the second blade is driven to adjust the size of the second opening to an open aperture value corresponding to a focal length. And the number of the second blades is larger than the number of the first blades.
Further, the lens barrel is configured to include the light amount adjusting mechanism.
In addition, the camera is configured to include the light amount adjusting mechanism.
In addition, the said structure may be improved suitably, and at least one part may substitute for another structure.

It is the schematic of a camera including the aperture mechanism of embodiment. It is a fragmentary sectional view of an aperture mechanism. It is a disassembled perspective view of an aperture mechanism. It is a front view of a blade holding plate. It is the figure which showed the example of the relationship between a focal distance and the open F value decided by the open aperture diameter of a sub-diaphragm. It is the figure which showed the opening formed by a sub-diaphragm | restriction, (a) is this embodiment, (b) is a comparison form. (A) is the elements on larger scale of Drawing 6 (a), and (b) is the elements on larger scale of Drawing 6 (b).

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic diagram of a camera 1 including an aperture mechanism 30 according to the embodiment.
As illustrated, the camera 1 includes a camera body 10 and a lens barrel 20 that can be attached to and detached from the camera body 10. In the present embodiment, the lens barrel 20 can be attached to and detached from the camera body 10, but the present invention is not limited to this, and the lens barrel 20 and the camera body 10 may be integrated.

The camera body 10 includes an image sensor 11 that converts a subject optical image into an electrical signal.
The lens barrel 20 includes a photographing optical system 21 including a zoom lens, and a diaphragm mechanism 30 according to the present embodiment. The photographing optical system 21 and the diaphragm mechanism 30 move in the direction of the optical axis OA according to the focal length.

FIG. 2 is a partial cross-sectional view of the diaphragm mechanism 30. FIG. 3 is an exploded perspective view of the aperture mechanism 30.
The diaphragm mechanism 30 includes a main diaphragm 31 that mainly controls light quantity, and a sub-diaphragm 32 that is provided separately from the main diaphragm 31 and that is provided to correct the aperture diameter in accordance with zooming and focusing.
The aperture mechanism 30 further includes a base member 33, a main aperture cam plate 34, a pressing plate 35, an aperture actuator 36, a blade holding plate 37, a sub aperture cam plate 38, and a holding plate rotating member 39. The spring member 41 is provided.

The base member 33 is a base on which each member is arranged, and is fixed to a fixing portion (not shown) of the lens barrel 20.
The main diaphragm 31 forms an opening by combining seven blades 31a, and determines a diaphragm diameter other than the opening. Projections 31b and 31c are provided on the subject side and the camera body 10 side of each blade 31a of the main diaphragm 31 in the optical axis OA direction, respectively.
The main diaphragm cam plate 34 is provided with a main diaphragm cam 34a in which the protrusion 31c on the camera body side of each blade 31a is inserted and moved.

The holding plate 35 fixes the main diaphragm cam plate 34 in the optical axis OA direction while being rotatable about the optical axis OA.
The diaphragm actuator 36 is a drive source for driving the blade 31a to open and close the opening of the main diaphragm 31 by rotating the main diaphragm cam plate 34. In the diaphragm actuator 36, a gear 36 a provided at the tip and a gear 34 d provided on the main diaphragm cam plate 34 are engaged with each other. The diaphragm actuator 36 is fixed to the holding plate 35 with screws 40.

The sub-aperture 32 is an aperture provided to correct the open aperture diameter in accordance with zooming and focusing, and has nine blades 32a that are different in number from the blades of the main aperture 31. Protrusions 32b and 32c are provided on the subject side and the camera body 10 side in the optical axis OA direction of each blade 32a of the sub-aperture 32, respectively.
The sub diaphragm cam plate 38 is provided with a sub diaphragm cam 38a.

FIG. 4 is a front view of the blade holding plate 37. As shown in the figure, the blade holding plate 37 is an annular plate member. The blade holding plate 37 is provided with seven holes 37 a for fitting the protrusions 31 b attached to the main diaphragm 31, and nine holes 37 b for fitting the protrusions 32 c attached to the sub diaphragm 32. A total of 16 holes are provided.
The holes 37a for the protrusions 31b of the main diaphragm 31 are provided on the inner diameter side, and the holes 37b for the protrusions 32c of the sub-throttle 32 are provided on the outer diameter side of the holes 37a, and are arranged evenly along the circumference. Yes.

The holding plate rotating member 39 is a bar member having a cam surface 39a, and the subject side is thinner than the camera body 40 side.
The spring member 41 is for applying the blade holding plate 37 to the cam surface 39 a of the holding plate rotating member 39. By biasing the spring member 41, for example, when the diaphragm mechanism 30 moves along the optical axis OA by changing the focal length, the blade holding plate 37 can be rotated by the inclination of the cam surface 39a. The open aperture diameter to be formed can be set to an appropriate diameter according to the focal length.

  Here, the open F value and the focal length will be described. FIG. 5 is a graph showing an example of the relationship between the open F value determined by the open stop diameter of the sub stop 32 and the focal length. As shown in the figure, when the focal length is wider than a certain focal length f1, the sub-aperture 32 is in the maximum open diameter state, and the open F value is maintained in a state of F3.5, for example.

  On the other hand, when the focal length is larger than f1, the aperture diameter gradually decreases as the focal length increases, and the open F value becomes F5.6 when the focal length reaches the maximum (tele end). Become.

  Thus, by changing the aperture diameter of the sub-aperture 32 in conjunction with the movement of the photographic optical system 21, the open F value can be set to an appropriate value according to the focal length.

FIG. 6 is a view showing an opening formed by the sub-aperture 32. (A) is the figure which showed the opening formed by the nine blade | wings by this embodiment, (b) is the figure which showed the opening formed by the seven blades in a comparison form.
Moreover, Fig.7 (a) is the elements on larger scale of Fig.6 (a), FIG.7 (b) is the elements on larger scale of FIG.6 (b). A dotted line in the figure is an inscribed circle L of the opening formed by the blade 31a. In the figure, the distance d is the maximum separation distance between the inscribed circle L and the edge R of the opening formed by the blade 32a.
As shown in the figure, the maximum separation distance d1 when formed with nine blades of the present embodiment as shown in FIG. 7A and the seven blades of the comparative form as shown in FIG. 7B. In comparison with the maximum separation distance d2 in the case of forming with d1, d1 <d2.
That is, when the number of blades 32a is nine as in this embodiment, the opening formed by the blades 32a is closer to a circle than when seven blades are used.

Therefore, according to the present embodiment, compared to, for example, the case where the sub-aperture 32 has a seven-blade configuration, the open aperture diameter can be made nearly circular, and the lens barrel 20 with a more beautiful blur can be provided. it can.
Even if the number of blades of the sub-aperture is increased in this way, the sub-aperture defines the open aperture diameter. Therefore, the aperture does not become smaller like the main diaphragm, and the number of blades can be increased. The main aperture is less likely to affect operability.
As described above, according to the present embodiment, it is possible to provide a light amount adjusting mechanism, a lens barrel, and a camera whose open aperture shape created on the sub-aperture side is close to a circular diameter.

(Deformation)
The present invention is not limited to the above-described embodiment, and various modifications and changes as described below are possible, and these are also within the scope of the present invention.
In the present embodiment, the example in which the blades 32a of the sub-aperture 32 are nine has been described. For example, when the main aperture is five, the sub aperture may be seven.
In the present embodiment, the sub diaphragm blade 32a is driven by the actuator 36, and the main diaphragm blade 31a is driven by the holding plate rotating member 39. However, the main diaphragm blade and the sub diaphragm blade are driven by the actuator or the holding device. It is not limited to either of the plate rotating members.
Further, although the holding plate rotating member 39 rotates the blade holding plate 37, the sub diaphragm blade cam plate 38 may be rotated.
In addition, although embodiment and a deformation | transformation form can also be used in combination as appropriate, detailed description is abbreviate | omitted. Further, the present invention is not limited to the embodiment described above.

  1: camera, 10: camera body, 11: imaging element, 20: lens barrel, 21: photographing optical system, 30: aperture mechanism, 31: main aperture, 31a: blade, 31b: protrusion, 31c: protrusion, 32: Sub-aperture, 32a: blade, 32c: protrusion, 33: base member, 34: main diaphragm cam plate, 34a: main diaphragm cam, 34d: gear, 35: pressing plate, 36: actuator, 36a: gear, 37: Blade holding plate, 37a: hole, 37b: hole, 38: sub-throttle cam plate, 38a: sub-throttle cam, 39: holding plate rotating member, 39a: cam surface, 41: spring member

Claims (5)

A main diaphragm that has a plurality of first blades that form a first opening, and drives the first blade to adjust the size of the first opening according to a diaphragm value;
A sub-aperture having a plurality of second blades forming a second opening, and driving the second blade to adjust the size of the second opening to an open aperture value corresponding to a focal length; ,
With
The number of the second blades is greater than the number of the first blades;
Light quantity adjustment mechanism characterized by The light quantity adjustment mechanism according to claim 1,
Each of the plurality of first blades has a first engagement portion,
Each of the plurality of second blades has a second engagement portion,
An opening through which a light beam passes is provided. A plurality of first engaged portions that engage with the first engaging portion are arranged along a first diameter, and a second engaging portion engages with the second engaging portion. The engaged portion includes a plurality of holding plates arranged along a second diameter different from the first diameter;
Light quantity adjustment mechanism characterized by The light quantity adjustment mechanism according to claim 2,
The second diameter is larger than the first diameter;
Light quantity adjustment mechanism characterized by   A lens barrel provided with the light quantity adjustment mechanism according to claim 1.   A camera provided with the light quantity adjustment mechanism of any one of Claim 1 to 3.

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