Variable Throttle Device

Abstract

To provide a small variable aperture device capable of changing the size of an aperture opening with little power. [Solution] The variable aperture device includes a number of fins arranged circumferentially to form an opening that restricts the light beam, a cam that rotates to displace the multiple fins in unison to change the size of the opening, and a smooth impact drive mechanism that rotates the cam.

Description

Technical Field

[0001] The present invention relates to a variable aperture device.

Background Art

[0002] There is known a variable aperture device that restricts a subject light beam that forms an image on a light-receiving surface of an image sensor by rotating a plurality of fins arranged along a circumferential direction. For example, as a variable aperture device applied to a camera unit incorporated in a smartphone, a gear ring that meshes with each of the plurality of fins via gears is rotated by a motor to change the size of an aperture opening formed by the plurality of fins (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] For example, when obtaining an output torque capable of rotating a plurality of fins simultaneously in a stepping motor or a voice coil motor, it is inevitably necessary to select a relatively large one to some extent. Driving such a large motor also requires a lot of power. Employing such a large motor in a small terminal device such as a smartphone poses a major design constraint.

[0005] The present invention has been made to solve such problems, and provides a small variable aperture device capable of changing the size of an aperture opening with less power.

Means for Solving the Problems

[0006] In one aspect of the present invention, a variable aperture device includes a plurality of fins arranged circumferentially to form an aperture that restricts the light beam, a cam that rotates to displace the plurality of fins in unison to change the size of the aperture, and a smooth impact drive mechanism that rotates the cam. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a small variable diaphragm device that can change the size of the diaphragm opening with little power. [Brief explanation of the drawings]

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

[0009]

[0023] Embodiments of the present invention will be described with reference to the accompanying drawings. In each drawing, components with the same reference numerals have the same or similar configurations. Furthermore, when multiple structures with the same or similar configurations exist in each drawing, some components may be designated with the same reference numerals, and others may not be designated with the same reference numerals, in order to avoid complication.

[0010] FIG. 1 is a perspective view of a partially assembled variable diaphragm device 100 according to this embodiment. The variable aperture device 100 is disposed in the middle of a lens group that forms a subject image on the light receiving surface of an imaging device, and is a device that restricts the light beam reaching the light receiving surface by changing the size of its aperture opening.

[0011] As shown in the figure, the variable aperture device 100 includes a plurality of fins 110, a base member 120, a cam 130, and a Smooth Impact Drive Mechanism (hereinafter referred to as "SIDM") 150. Each fin 110 is a resin-made planar plate having a shape in which the tip portion forming the aperture opening IH together with other fins 110 is curved on an arc. In the present embodiment, six fins 110 are arranged along the circumferential direction on the annular portion of the base member 120. Note that the number of fins 110 can achieve a more circular aperture opening if it is larger, but it is appropriately determined according to the performance, cost, etc. required for the variable aperture device 100.

[0012] Specifically, as will be described later, each fin 110 is linked to the annular cam 130 and is displaced in conjunction with the operation of the cam 130 rotated by the SIDM 150. The SIDM 150 is a linear actuator that utilizes the steep expansion and contraction of a piezoelectric element, and the inertia and frictional force of the object to be driven. The SIDM 150 rotates the cam 130 clockwise and counterclockwise. When the SIDM 150 is driven by an external control circuit, the variable aperture device 100 changes the size of the aperture opening IH.

[0013] As shown in the figure, the x-axis, y-axis, and z-axis are defined. That is, the direction orthogonal to the aperture plane of the aperture opening IH formed by the plurality of fins 110 is the z-axis direction, the direction parallel to the aperture plane and in which the drive shaft of the SIDM 150 described later extends is the x-axis direction, and the direction orthogonal to the z-axis and x-axis is the y-axis direction. In several subsequent drawings, similar coordinate axes are also noted based on the assembled state as shown in FIG. 1, thereby indicating the orientation of the components represented by each drawing.

[0014] FIG. 2 is an exploded perspective view of the main components of the variable aperture device 100 and also shows the lens barrel 200. The lens barrel 200 holds a lens 210 which is at least a part of a lens group that forms a subject image on the light receiving surface of the imaging element. The variable aperture device 100 is assembled to the lens barrel 200 along the z-axis direction which is also the optical axis direction of the lens group.

[0015] The base member 120 is a resin member having an approximately annular shape. On the end face of the base member 120, cylindrical support shafts 121 protruding short in the z-axis direction are provided at equal intervals along the circumferential direction of the annular shape, corresponding to the number of fins 110 (six in this embodiment). Also, a part of the annular shape is cut out to provide a cutout portion 123, and the SIDM 150 is fixed to the base member 120 so as to be accommodated in the cutout portion 123.

[0016] The cam 130 is also a resin member having an approximately annular shape. On the end face of the cam 130, cylindrical traction shafts 132 protruding short in the z-axis direction are provided at equal intervals along the circumferential direction of the annular shape, corresponding to the number of fins 110 (six in this embodiment). Also, a part of the annular shape is cut in a D shape, and an insertion hole 133 for inserting and fixing the pressing spring 140 is provided in the portion. The pressing spring 140 is a member for contacting the SIDM 150 and transmitting its driving force, which will be specifically described later. By being inserted into the insertion hole 133, it is fixed to the cam 130 and rotates integrally with the cam 130.

[0017] The cam 130 has an annular outer peripheral wall 135 at the outermost periphery in the radial direction. The cam 130 is accommodated inside the base member 120 such that the annular outer peripheral wall 135 loosely fits with a guide inner peripheral wall 125 formed along the inside of the annular shape of the base member 120. By guiding the annular outer peripheral wall 135 of the cam 130 along the guide inner peripheral wall 125 of the base member 120, the cam 130 can rotate around the z-axis inside the base member 120.

[0018] When the cam 130 is housed in the base member 120, the respective end faces substantially coincide on the same plane. Each fin 110 has a support shaft hole 111 through which the support shaft 121 is loosely inserted and a traction shaft hole 112 through which the traction shaft 132 is loosely inserted. Each fin 110 is arranged in contact with the end faces of the base member 120 and the cam 130 by inserting the support shaft hole 111 into the support shaft 121 and the traction shaft hole 112 into the traction shaft 132 respectively.

[0019] The cover 160 is a resin member in the shape of a circular flat plate having substantially the same diameter as the outer diameter of the base member 120, with a circular cover opening 163 provided at the center. The cover opening 163 has a size that does not obstruct the light beam incident on the aperture opening IH at the maximum opening. The cover 160 is provided with fitting holes 161 that fit with the support shafts 121 at equal intervals along the circumferential direction, corresponding to the number of support shafts 121 (six in this embodiment). Also, guide holes 162 for guiding the displacement of the traction shafts 132 are provided at equal intervals along the circumferential direction, corresponding to the number of traction shafts 132 (six in this embodiment). Since the traction shaft 132 rotates along the circumferential direction when the cam 130 is rotated, the guide holes 162 are formed as arc-shaped slits corresponding to the rotation range of the traction shaft 132.

[0020] When the cover 160 is attached to the base member 120 through the fitting holes 161, each fin 110 will be interposed between the respective end faces of the base member 120 and the cam 130 and one surface on the attachment side of the cover 160. Then, when the cam 130 is rotated around the z-axis, each fin 110 is pulled by the traction shaft 132 provided on the cam 130 and rotates around the support shaft 121. In this way, as each fin 110 rotates around its respective support shaft 121, the size of the aperture opening IH increases or decreases.

[0021] The displacement sensor 170 is, for example, a magnetic sensor composed of a magnet and a Hall element, and the magnet and the Hall element are provided so as to straddle the respective side walls of the base member 120 and the cam 130 so as to face each other. The displacement sensor 170 may be not limited to a magnetic sensor but may be a laser reflection type sensor or the like.

[0022] FIG. 3 is a diagram showing how the aperture opening IH formed by the fins 110 changes. In particular, FIG. 3(A) shows the state where the size of the aperture opening IH is maximum, FIG. 3(C) shows the state where it is minimum, and FIG. 3(B) shows the state where it is of an intermediate size between FIG. 3(A) and (C). The size of the aperture opening IH defines the F value of the optical system. For example, in the present embodiment, FIG. 3(A) shows the aperture state of F1.5, FIG. 3(B) shows the aperture state of F2.5, and FIG. 3(C) shows the aperture state of F5.8.

[0023] Each fin 110 rotates around the support shaft 121 by being pulled by the traction shaft 132. The aperture opening IH becomes larger when each fin 110 rotates clockwise (CW) with respect to the support shaft 121, and becomes smaller when it rotates counterclockwise (CCW). Thus, if the size of the aperture opening IH can be changed according to the state of the subject or the light source, not only can the amount of light incident on the imaging element be adjusted, but also the blur of the subject image can be controlled. In FIG. 3, three aperture states of F1.5, F2.5, and F5.8 are shown, but the variable aperture device 100 in the present embodiment is not limited to the aperture states corresponding to these F values, and can realize an aperture state corresponding to substantially continuous F values between the maximum aperture state and the minimum aperture state. However, the variable aperture device 100 may be controlled so as to realize aperture states corresponding to a plurality of discrete F values set according to the specifications of the camera unit. For example, the variable aperture device 100 may be controlled so as to realize aperture states corresponding to five F values such as F1.4, F2, F2.8, F4, and F5.6.

[0024] 4 is a perspective view showing the connection structure between SIDM 150 and cam 130. SIDM 150 is mainly composed of drive shaft 151, main body 152, and weight 153. Main body 152 includes a piezoelectric element that expands and contracts sharply when a high-frequency voltage is applied. Drive shaft 151 is a cylindrical member extending in one direction from main body 152 and is made of, for example, CFRP (Carbon Fiber Reinforced Plastics). Weight 153 is a high-mass member fixed to the side of main body 152 opposite the side to which drive shaft 151 extends and is made of, for example, a tungsten alloy.

[0025] The pressure spring 140 fixed to the cam 130 presses and holds the drive shaft 151. In other words, the cam 130 integrated with the pressure spring 140 is the object to be driven by the SIDM 150.

[0026] 5 is a perspective view of the pressure spring 140. The sandwiched drive shaft 151 is indicated by a dotted line. In this embodiment, the pressure spring 140 is formed by bending a single metal plate. The material of the metal plate is, for example, SUS304.

[0027] The pressure spring 140 has a first flat plate portion 142 and a second flat plate portion 143 that face each other. The first flat plate portion 142 and the second flat plate portion 143 press the drive shaft 151, which extends along the x-axis direction, from both the positive side and the negative side of the z-axis, to sandwich the drive shaft 151. Therefore, the first flat plate portion 142 and the second flat plate portion 143 each make line contact with the drive shaft 151 in a single straight line.

[0028] The pressing spring 140 has an insertion fixing portion 141 inserted into the insertion hole 133 of the cam 130. Further, it has a first protruding portion 144 that is continuous from the insertion fixing portion 141 and protrudes toward the drive shaft 151 side, and a first bending portion 146 that connects the first protruding portion 144 and the first flat plate portion 142. Further, it has a second protruding portion 145 that protrudes from the insertion fixing portion 141 side toward the drive shaft 151 side in the same manner as the first protruding portion 144, and a third bending portion 148 that connects the second protruding portion 145 and the second flat plate portion 143. Further, it has a second bending portion 147 that connects the end side of the first flat plate portion 142 that is not connected to the first bending portion 146 and the end side of the second flat plate portion 143 that is not connected to the third bending portion 148. By adopting such a bending structure, the pressing force by the first flat plate portion 142 and the second flat plate portion 143 that sandwich the drive shaft 151 can be kept more constant even when the contact position with the drive shaft 151 changes.

[0029] FIG. 6 is a schematic diagram for explaining the rotation operation of the cam 130 by the SIDM 150. Specifically, it is a diagram schematically showing the positional relationship between the SIDM 150 and the cam 130 corresponding to the three open states shown in FIG. 3. The hatched area is mainly the area shielded by the fins 110.

[0030] The central diagram of FIG. 6 represents the state corresponding to FIG. 3(B), and the pressing spring 140 extends from the cam 130 along the y-axis direction orthogonal to the x-axis, which is the extending direction of the drive shaft 151, and sandwiches the drive shaft 151. When the SIDM 150 is driven so as to push out the pressing spring 140 in the tip direction of the drive shaft 151 (x-axis plus direction) from this state, it transitions to the state of the left diagram of FIG. 6 corresponding to FIG. 3(A). That is, since the cam 130 is housed in the base member 120 and is guided to rotate around the z-axis, when the pressing spring 140 is pushed out in the x-axis plus direction, the cam 130 is rotated counterclockwise (CCW) with respect to the z-axis. At this time, as shown in FIG. 5, since the pressing spring 140 sandwiches the drive shaft 151 with two flat plate portions, the contact lines between each flat plate portion and the drive shaft 151 can rotate relatively around the z-axis within each plane. As a result, the extending direction of the pressing spring 140 rotates counterclockwise and intersects the extending direction (x-axis direction) of the drive shaft 151.

[0031] When the SIDM150 is driven so as to pull back the pressing spring 140 from the state of the central figure in FIG. 6 in the proximal direction (x-axis minus direction) of the drive shaft 151, the state changes to the state of the right figure in FIG. 6 corresponding to FIG. 3(C). That is, when the pressing spring 140 is pulled back in the x-axis minus direction, the cam 130 is rotated clockwise (CW) with respect to the z-axis. At this time, the contact lines between each of the two flat plate portions of the pressing spring 140 and the drive shaft 151 can rotate relative to each other around the z-axis within their respective planes. As a result, the extending direction of the pressing spring 140 rotates clockwise and intersects the extending direction (x-axis direction) of the drive shaft 151 obliquely.

[0032] Note that if the SIDM150 is driven so as to pull back the pressing spring 140 from the state of the left figure in FIG. 6 in the proximal direction of the drive shaft 151, the state changes to the state of the central figure in FIG. 6. Also, if the SIDM150 is driven so as to push out the pressing spring 140 from the state of the right figure in FIG. 6 in the distal direction of the drive shaft 151, the state changes to the state of the central figure in FIG. 6. In the present embodiment, by providing the two flat plate portions that sandwich the drive shaft 151 in the pressing spring 140, the rotation of the cam 130 is realized using a SIDM that generally linearly displaces a driven object in the drive shaft direction. The SIDM has the characteristics of being small in size, exerting a large driving force with relatively small power consumption, and having a small driving noise, so it is suitable for the variable aperture device 100 incorporated in the imaging unit.

[0033] Note that since the contact lines between each of the flat plate portions and the drive shaft 151 rotate relative to each other around the z-axis within their respective planes, depending on conditions such as the frictional force at the contact portion, the rotation amount of the cam 130 with respect to the command signal to the SIDM150 may not be stable. In such a case, the output of the displacement sensor 170 may be monitored to detect the rotation amount of the cam 130, and feedback control may be performed to gradually reduce the deviation of the rotation amount with respect to the command.

[0034] In the present embodiment described above, a pressing spring 140 formed by bending a single metal plate is employed. However, as long as it includes two opposing flat plates that press and sandwich the drive shaft 151, the pressing spring may be in any form. Further, the pressing spring may not be a separate member that is inserted and fixed as in the present embodiment, but may be integrally formed with the cam 130 by, for example, two-color molding.

Explanation of Reference Numerals

[0035] 100... Variable aperture device, 110... Fin, 111... Support shaft hole, 112... Traction shaft hole, 120... Base member, 121... Support shaft, 123... Notch, 125... Guide inner peripheral wall, 130... Cam, 132... Traction shaft, 133... Insertion hole, 135... Annular outer peripheral wall, 140... Pressing spring, 141... Insertion and fixing portion, 142... First flat plate portion, 143... Second flat plate portion, 144... First overhanging portion, 145... Second overhanging portion, 146... First bending portion, 147... Second bending portion, 148... Third bending portion, 150... Smooth Impact Drive Mechanism (SIDM), 151... Drive shaft, 152... Main body portion, 153... Weight, 160... Cover, 161... Fitting hole, 162... Guide hole, 163... Cover opening, 170... Displacement sensor, 200... Lens barrel, 210... Lens

Claims

1. A plurality of fins arranged along the circumferential direction so as to form an aperture for restricting a light beam, a cam that rotates to displace the plurality of fins in conjunction with each other to change the size of the aperture, and a smooth impact drive mechanism for rotating the cam. The variable aperture device is provided with: the cam includes two opposing planar plates that press and sandwich the drive shaft of the smooth impact drive mechanism, and the smooth impact drive mechanism is a variable aperture device that rotates the cam by displacing the two planar plates.

2. The variable aperture device according to Claim 1, wherein the two planar plates are formed by bending a single metal plate.

3. The variable aperture device according to Claim 1, further comprising a displacement sensor that straddles a side portion of the cam and a base member that supports the smooth impact drive mechanism, and detects the amount of rotation of the cam.

4. Each of the two planar plates is in line contact with the drive shaft in a straight line, and the contact lines of each of the two planar plates with the drive shaft can rotate relative to each other about the z-axis perpendicular to the aperture plane of the aperture formed by the plurality of fins within their respective planes. The variable aperture device according to Claim 1.

5. A barrel, wherein at least one lens is installed in the barrel, and a variable aperture device control device according to any one of Claims 1 to 4 installed in the barrel. An imaging module.

Images