Light intensity control devices and optical instruments

Abstract

To provide a light quantity adjustment device that can reduce the warp of a plurality of light quantity adjustment blades when the light quantity adjustment blades are closed.SOLUTION: In a light quantity adjustment device according to the present invention, each of a plurality of light quantity adjustment blades overlaps another light quantity adjustment blade to form a light passage opening, and the plurality of light quantity adjustment blades rotate to change the size of the light passage opening. Each of the plurality of light quantity adjustment blades has a first portion that has a constant thickness, and a second portion that is formed to be reduced in thickness from the first portion toward an end edge part that forms the edge of the light passage opening. With the plurality of light quantity adjustment blades overlapping each other in a light passage direction in a minimum aperture state of the light quantity adjustment device, the area of overlapping of the second portions of the adjacent blades is larger than the area of overlapping of the first portions.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a light quantity adjustment device mounted on an optical device such as an imaging device or an interchangeable lens.

Background Art

[0002] In a light quantity adjustment device (aperture device) mounted on an optical device such as an imaging device or an interchangeable lens, the shape of the aperture opening as a light passage opening formed is preferably as close to a circle as possible. In order to form an aperture opening close to a circle, a large number of three or more aperture blades (light quantity adjustment blades) are often used.

[0003] Patent Document 1 discloses an iris aperture device that forms a polygonal aperture opening close to a circle by rotating a large number of aperture blades with a drive ring that is rotatable around a fixed opening formed in a base member.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, conventional iris aperture devices have the following problems. FIG. 7 shows the configuration of an imaging device equipped with a conventional iris aperture device. In FIG. 7, 101 is a base member of the aperture device, and 103 is a drive ring that is rotatable around a fixed opening of the base member 101. 106 is an actuator that rotates the drive ring 103, and 105 is a plurality of aperture blades that are rotated around a shaft portion (not shown) provided on the base member 101 by the drive ring 103. Further, 114 is a lens disposed adjacent to the aperture device, and 113 is an imaging element that photoelectrically converts a subject image formed by a photographic optical system including the lens 114 and the aperture device.

[0006] Figure 8 shows the state in which multiple aperture blades 105 are stopped down to form a small aperture (small aperture state). Figure 8 also shows a magnified view of the multiple aperture blades 105 in this small aperture state. As the aperture opening is stopped down, the tips of the multiple aperture blades 105 overlap each other, causing them to curve towards the lens 114, as indicated by the symbol H'. Therefore, in order to avoid interference between these curved aperture blades 105 and the lens 114, it is necessary to secure a retraction space h' for the lens 114 relative to the aperture mechanism in advance. As a result, the imaging device becomes larger.

[0007] Furthermore, the stress generated by the overlapping of these blades can cause scratches on the aperture blades, and the reflection of light from these scratches may degrade the optical properties.

[0008] Furthermore, because aperture blades have a certain thickness, the thickness of the aperture blades creates a large step difference with respect to the aperture opening surface, which can easily cause small-aperture diffraction and degrade optical performance.

[0009] The present invention has been made in view of the above-mentioned problems, and its objective is to provide a light intensity adjustment device that can reduce the curvature of light intensity adjustment blades when multiple light intensity adjustment blades are narrowed. [Means for solving the problem]

[0010] The light intensity adjustment device according to the present invention is a light intensity adjustment device in which each of a plurality of light intensity adjustment vanes overlaps with other light intensity adjustment vanes to form a light-passing aperture, and the size of the light-passing aperture is changed by the rotation of the plurality of light intensity adjustment vanes, wherein each of the plurality of light intensity adjustment vanes has a first portion with a constant thickness and a second portion that is formed such that its thickness decreases from the first portion toward the edge portion that forms the edge of the light-passing aperture, and in the minimum aperture state of the light intensity adjustment device, the plurality of light intensity adjustment vanes overlap in the direction of light passage, The first portions of adjacent wings overlap, andThe present invention is characterized in that the overlapping area of ​​the second portions of adjacent feathers is greater than the overlapping area of ​​the first portions. [Effects of the Invention]

[0011] According to the present invention, it is possible to reduce the curvature of the light intensity adjustment blades when multiple light intensity adjustment blades are narrowed down. [Brief explanation of the drawing]

[0012] [Figure 1] An exploded perspective view of an aperture device according to Embodiment 1 of the present invention. [Figure 2] Plan view and cross-sectional view of the aperture blades used in the aperture device of Embodiment 1. [Figure 3] A view of the aperture blades of the aperture device of Embodiment 1 in the small aperture state, as seen from the optical axis direction. [Figure 4] A perspective view showing the curvature of the aperture blades in the small aperture state of the aperture device of Embodiment 1. [Figure 5] A cross-sectional view of an imaging device equipped with the aperture device of Embodiment 1. [Figure 6] A schematic diagram of an imaging device equipped with the aperture device of Embodiment 1. [Figure 7] Cross-sectional view of an imaging device equipped with a conventional aperture mechanism. [Figure 8] A perspective view showing the curvature of the aperture blades in a conventional aperture device at a small aperture setting. [Modes for carrying out the invention]

[0013] Embodiments of the present invention will be described in detail below with reference to the drawings.

[0014] <Embodiment 1> Figure 1 is a disassembled view of the aperture device 100, which is an embodiment 1 of the light intensity control device of the present invention. Figure 2 is a view of one of the aperture blades, which are used as light intensity control blades in the aperture device, showing its front view and cross-sectional shape along line AA.

[0015] In FIG. 1, 1, 2, 3, 4, 5, 6, 7, 8, and 9 are aperture blades. In this embodiment, the case of using nine aperture blades will be described. However, the present invention can be applied to an aperture device that uses a plurality of three or more aperture blades (light amount adjustment blades). In the following description, the aperture blades 1, 2, 3, 4, 5, 6, 7, 8, and 9 are abbreviated as aperture blades 1 to 9, and each part of the aperture blades 1 to 9 is also abbreviated as 1x to 9x.

[0016] The aperture blades 1 to 9 are integrally formed parts formed in a thin plate shape from a synthetic resin. As shown in FIG. 2, each of the aperture blades 1 to 9 has a base portion in which a first shaft portion 1c to 9c serving as a rotation center axis and a second shaft portion 1d to 9d which is a driven shaft for receiving a driving force for rotation are formed on opposite surfaces, and a blade portion 1b to 9b formed in a tapered shape from the base portion toward the tip. And, on the blade portions 1b to 9b, opening side portions 1a to 9a which are inclined portions to be described in detail later are formed.

[0017] Also, in FIG. 1, 10 is a rotating member formed in a ring shape, and an opening 10a is formed at the center thereof. In the following description, the direction orthogonal to the opening surfaces of this opening 10a and the openings (11a, 12a) formed in the members (11, 12) to be described later is referred to as the optical axis direction. The rotating member 10 has shaft hole portions 10b to 10j formed at nine locations in its circumferential direction, a ridge portion 10k divided into nine in the circumferential direction, and a gear portion 10l formed at a part of the circumferential direction.

[0018] 11 is a cam member formed in a ring shape and also serves as a cover member of the aperture device of this embodiment. An opening 11a is formed at the center of the cam member​​​12 is a base member formed in a ring shape, which is a floor plate, and an opening 12a is formed in the center thereof. Further, a motor mounting portion 12c having a hole portion 12b is provided at one location in the circumferential direction of the floor plate 12.

[0020] 13 is a stepping motor that drives the rotating member 10. A pinion gear 14 is attached to the output shaft of the stepping motor 13 so as to rotate integrally with the output shaft. The stepping motor 13 is fixed to the motor mounting portion 12c of the floor plate 12, and the pinion gear 14 passes through the hole portion 12b of the floor plate 12 and meshes with the gear portion 10l of the rotating member 10. Incidentally, the stepping motor 13 may be fixed to the cam member 11. The rotating member 10, the cam member 11, the stepping motor 13, and the pinion gear 14 constitute a drive mechanism of the aperture device of the present embodiment.

[0021] The cam member 11 forms a space for arranging the aperture blades 1 to 9 and the rotating member 10 in this order between itself and the floor plate 12, and is fixed to the floor plate 12 by the claw portion 11l, thereby preventing the rotating member 10 and the aperture blades 1 to 9 from falling off with respect to the floor plate 12. The protruding strip portion 10k formed on the rotating member 10 is rotatably inserted into the opening 10a of the floor plate 12. The rotating member 10 is rotatably supported in the circumferential direction (direction around the optical axis) by sliding the outer peripheral surface of the protruding strip portion 10k against the protruding portions 12d formed at equal intervals on the inner circumference of the opening 12a of the floor plate 12.

[0022] Further, the first shaft portions 1c to 9c of the aperture blades 1 to 9 are respectively rotatably inserted into the shaft hole portions 10b to 10j formed in the rotating member 10. On the other hand, the second shaft portions 1d to 9d are respectively inserted into the cam groove portions 11b to 11j formed in the cam member 11.

[0023] <0000When the stepping motor 13 fixed to the base plate 12 is driven and the pinion gear 14 rotates, the rotating member 10, whose gear portion 10l meshes with the pinion gear 14, also rotates. As a result, the aperture blades 1 to 9 rotate around the first shaft portion 1c to 9c, with the second shaft portions 1d to 9d moving along the cam groove portions 11b to 11j of the cam member 11 (i.e., the second shaft portions 1d to 9d receive driving force from the cam groove portions 11b to 11j).

[0024] The aperture blades 1-9 are arranged at equal intervals in the circumferential direction, and each blade portion 1b-9b overlaps with the blade portions of the other aperture blades, forming an aperture opening, which is the light-passing aperture, inside them. As the aperture blades 1-9 rotate, the amount of overlap between the blade portions 1b-9b changes, and the aperture diameter is continuously changed. The greater the overlap between the aperture blades 1-9 (blade portions 1b-9b), the smaller the aperture diameter. In the following explanation, the direction in which each aperture blade rotates is called the blade rotation direction. Overlapping here means overlapping in the direction of light passage, that is, being positioned at the same distance from the optical axis, and the parts where the blades contact each other change according to the shape of the aperture opening and the curvature of the blades.

[0025] Figure 5 shows the configuration of an imaging device equipped with the aperture device configured as described above. 16 is a lens positioned adjacent to the image side of the aperture device, and 15 is an image sensor that converts the subject image formed by the imaging optical system including lens 16 and the aperture device into photoelectric form.

[0026] As explained using Figures 7 and 8, in conventional aperture devices, when multiple aperture blades 105 are stopped down to form a small aperture, the multiple aperture blades 105 bend significantly in the optical axis direction (towards the lens 114) due to the overlap of their tips.

[0027] To resolve the problem of blade warping in this small aperture state, in this embodiment, the blade portions 1b to 9b of each aperture blade 1 to 9 are formed as follows. As shown in Figures 2 and 3, the portion of each aperture blade that overlaps with the blade portions of other aperture blades and includes the edge portions 1e to 9e that form the edge of the aperture opening is called the opening side portion 1a to 9a. In this embodiment, the opening side portion 1a to 9a is formed such that its thickness decreases toward the edge portions 1e to 9e in the direction of blade rotation in order to reduce warping due to blade overlap. In Figure 2, the direction of blade rotation is shown as the direction along line AA. Figure 3(a) shows the aperture blades 1 to 9 forming the small aperture opening as seen from the cam member 11 side. Figure 3(b) is a central cross-sectional view of Figure 3(a).

[0028] Figure 2 shows an example of a shape where the thickness decreases towards the edge, where the surface on the cam member 11 side (the first surface) of the thickness direction surfaces of the opening-side portions 1a to 9a is inclined at a constant angle θ with respect to the surface on the rotating member 10 side (the second surface). In this embodiment, θ is 2 degrees. This example also shows a case where the thickness decreases continuously and at a constant rate towards the edge. However, the shape where the thickness decreases towards the edge is not limited to this, and both the first surface and the second surface may be inclined surfaces that are inclined with respect to the parallel flat plate-like portions of the wing portions 1b to 9b other than the opening-side portions 1a to 9a. Furthermore, the thickness may decrease in stages or continuously towards the edge, and a continuous decrease improves moldability.

[0029] In this case, the angle (tilt angle) θ between the first surface and the second surface is preferably between 1 degree and 4 degrees. By setting θ to 4 degrees or less, the curvature caused by the overlapping of the multiple light-adjusting vanes when they are narrowed down is gradually reduced. This prevents damage and deformation of the vanes due to sudden upward curvature. Furthermore, if the opening portion is made by gradually increasing the thickness based on the thickness of the edge portion until it reaches a predetermined thickness of the vane portion, then as θ decreases, the load fluctuations caused by the overlapping of multiple vanes are also reduced, preventing malfunctions. In this embodiment, the thickness of the vane portion is set to be 2 to 4 times the thickness of the edge portion, with the edge portion thickness being 50 μm and the vane portion thickness being 150 μm.

[0030] Furthermore, if at least one of the first and second surfaces is formed as a curved surface rather than a planar surface such as an inclined surface, the thickness decreases continuously towards the edge, although the rate of decrease does not have to be constant. In this case, it is desirable that the angle between the tangents of the first and second surfaces (the range of angles corresponding to the inclination angle mentioned above) is between 1 degree and 4 degrees.

[0031] Furthermore, it is desirable that the width W of the opening portion 1a to 9a in the direction of blade rotation be as wide as possible while maintaining the strength of blades 1 to 9. Specifically, it is desirable that it be 10 to 30 times the maximum thickness T of the opening portion. Here again, if the opening portion is made up of a blade portion with a predetermined thickness, gradually increasing in thickness based on the thickness of the edge, the smaller the angle θ, the larger the ratio of the width W to the maximum thickness T. Also, in this embodiment (Figure 2), the case in which the opening portion 1a to 9a is formed in a part of the direction of blade rotation of blade portions 1b to 9b is described, but it may also be formed over the entire direction of blade rotation of blade portions 1b to 9b.

[0032] In addition, the edge may have a portion of a certain thickness, and the thickness continuously decreases towards the edge. In other words, the thickness continuously increases from the portion of a certain thickness at the edge toward the opposite side from the opening portion 1a to 9a. That is, when comparing the case where the thickness continuously decreases towards the edge with the case where the thickness of the edge and the blade portion 1b to 9b are the same, the blade strength is improved when the thickness continuously decreases towards the edge. Therefore, to achieve the same strength as a blade where the thickness of the edge and the blade portion 1b to 9b are the same, a configuration in which the thickness continuously decreases towards the edge can be used to create a diaphragm with a thin edge.

[0033] Next, with reference to Figure 3, the width W of the opening portions 1a to 9a of each blade will be explained in more detail. Figure 3(a) shows the overlap of adjacent blades 7 and 8 in the minimum aperture state. In this embodiment, by making the width W of the opening portions 1a to 9a of each blade 1 to 9 as wide as possible, the curvature of the blades in the minimum aperture state can be reduced, and the sliding resistance during the opening and closing operation of each blade can be reduced. However, on the other hand, if the width W of the opening portions 1a to 9a is made too large, the constant thickness portions 1f to 9f will decrease, and the strength of the blades will decrease.

[0034] Therefore, in this embodiment, the overlapping area of ​​each blade is set as shown in Figure 3(a). In Figure 3(a), blades 7 and 8 are shown as examples of two adjacent blades, but the relationship between other adjacent blades is similar.

[0035] Here, in the minimum aperture state of the iris diaphragm device 100, the overlapping portion of blades 7 and 8 where the thinner opening-side portions 7a and 8a (opening-side portions) overlap is defined as region A. Similarly, the overlapping portion of blades 7 and 8 where the thinner opening-side portion 7a (8a) of one blade overlaps with the constant-thickness portion 8f (7f) of the other blade (the overlapping portion of constant-thickness portions) is defined as region B. Furthermore, the overlapping portion of blades 7 and 8 where the constant-thickness portions 7f and 8f overlap is defined as region C. In this case, if the area of ​​region A is larger than the area of ​​region C, it is easier to reduce warping.

[0036] In this embodiment, if the areas of regions A, B, and C in the minimum aperture state are denoted as area EA, area EB, and area EC, then EC <EA<EB The settings are configured to achieve this. This reduces the curvature of the blades at the minimum aperture while maintaining the strength of each blade. In this embodiment, the area of ​​region B closer to the first shaft portion 1c is larger than the area of ​​region A.

[0037] As described above, in this embodiment, by forming opening-side portions 1a to 9a on the blade portions 1b to 9b of each aperture blade 1 to 9, where the thickness decreases toward the edge portions 1e to 9e in the direction of blade rotation, the curvature of the blades can be reduced as shown in Figures 4 and 5. Figure 4 shows a magnified view of aperture blades 1 to 9 in the small aperture state. In Figure 5, H indicates the amount of blade curvature in the small aperture state in this embodiment, which is less than the amount of blade curvature H' of the conventional aperture device shown in Figure 7. Furthermore, because the amount of blade curvature is small, the retraction space h for lenses and other optical components adjacent to the aperture device in the direction of blade curvature can be made smaller than the conventional retraction space h', and the imaging device can be made smaller as a result.

[0038] In this embodiment, the minimum aperture diameter in the small aperture state is assumed to be an extremely small aperture diameter of 1 mm or less. The fact that such an extremely small aperture state can be achieved with a small amount of blade curvature is a distinguishing feature of this embodiment compared to conventional designs.

[0039] The width W of the opening-side portions 1a to 9a in the direction of blade rotation is preferably wider than the diameter of the minimum aperture. A wider width W of the opening-side portions 1a to 9a in the direction of blade rotation than the diameter of the minimum aperture results in better sliding performance when narrowing to the minimum aperture.

[0040] Furthermore, in this embodiment, by forming the opening portions 1a to 9a, the load generated when the aperture blades 1 to 9 overlap and rotate can be reduced. As a result, good operating characteristics of the aperture device can be obtained, and scratches on each aperture blade can be prevented.

[0041] Furthermore, in this embodiment, since the edge portions 1e to 9e of the aperture-side portions 1a to 9a are thin, the thickness of the aperture blades 1 to 9 does not create a large step difference with respect to the aperture surface of the aperture opening, thereby preventing deterioration of optical performance due to a large step difference.

[0042] <Embodiment 2> Figure 6 shows the internal configuration of an interchangeable lens 221 for a single-lens reflex camera, which is an imaging device equipped with the aperture device described in Embodiment 1, and the camera body to which the interchangeable lens is attached.

[0043] The barrel of the interchangeable lens 221 houses a photographic optical system including a variable magnification lens 232, an aperture device 100 of Embodiment 1 for narrowing the optical path, and a focusing lens 229.

[0044] The image sensor 225, composed of photoelectric conversion elements such as a CCD sensor or CMOS sensor, is located inside the camera body and outputs an electrical signal by photoelectric conversion of the subject image formed by the interchangeable lens 221. By changing the aperture opening of the aperture device 100 or moving an ND filter (not shown) forward or backward, the brightness of the subject image formed on the image sensor 225 (i.e., the amount of light reaching the image sensor 225) can be appropriately set.

[0045] The electrical signal output from the image sensor 225 is converted into a digital signal in the image processing circuit 226 and subjected to various image processing steps. This generates an image signal.

[0046] The user can perform zooming by rotating the zoom ring 231 to move the variable magnification lens 232. The controller 222 detects the contrast of the image signal and controls the focus motor 228 according to the contrast to move the focus lens 229 and perform autofocus. Alternatively, the controller 222 may control the focus motor 228 and move the focus lens 229 to perform autofocus based on the detection signal of a focus detection means using a phase difference detection method (not shown).

[0047] Furthermore, the controller 222 controls the stepping motor 13 of the aperture device 100 to adjust the amount of light based on the photometric value of a photometric means (not shown) or the image signal. This makes it possible to create natural-looking bokeh and ghosting during shooting and record high-quality images.

[0048] Furthermore, the present invention is not limited to the single-lens reflex cameras described above, but can be broadly applied to optical equipment such as digital cameras with integrated lenses and video cameras.

[0049] The embodiments described above are merely representative examples, and various modifications and changes can be made to each embodiment when implementing the present invention. [Explanation of symbols]

[0050] 1-9 aperture blades 10 Rotating member 11 Cam member 12 Main plate 13 Stepping motor

Claims

1. A light intensity adjustment device in which each of a plurality of light intensity adjustment vanes overlaps with other light intensity adjustment vanes to form a light-passing aperture, and the size of the light-passing aperture is changed by the rotation of the plurality of light intensity adjustment vanes, Each of the plurality of light intensity adjustment vanes has a first portion with a constant thickness and a second portion that is formed such that its thickness decreases from the first portion toward the edge portion that forms the edge of the light-passing aperture. A light intensity adjustment device characterized in that, in the minimum aperture state of the light intensity adjustment device, when the plurality of light intensity adjustment vanes overlap in the direction of light passage, the first portions of adjacent vanes overlap, and the overlapping area of ​​the second portions of adjacent vanes is larger than the overlapping area of ​​the first portions.

2. The first area EC is the overlapping area of ​​the first parts, the second area EB is the overlapping area of ​​the first part and the second part, and the third area EA is the overlapping area of ​​the second parts. EC < EA < EB The light intensity adjustment device according to claim 1, characterized in that it satisfies the relationship.

3. The light intensity adjustment device according to claim 1 or 2, characterized in that the angle formed by both surfaces in the thickness direction of the second portion or the angle formed by the tangents of both surfaces is 1 degree or more and 4 degrees or less.

4. A light intensity control device according to any one of claims 1 to 3, An optical device characterized by having an image sensor that captures light that has passed through the light intensity adjustment device.

Images