Blade driving device and optical instrument

Abstract

To provide a blade driving device that suitably minimizes a deviation amount of an aperture position shifting from a reference plane in an optical axis direction due to upward deflection of a blade group that occurs when an opening diameter is decreased by an opening / closing operation.SOLUTION: A blade driving device for adjusting the size of an aperture through which light passes by a plurality of diaphragm blades 2 includes: a base member 1 in which a fixed aperture is formed; and a drive plate 3 for driving a plurality of diaphragm blades 2, each of which has a rotary shaft pin 21c formed thereon. The drive plate 3 has rotary shaft holes 3a-3i engaged with the rotary shaft pins 21c. The rotary shaft holes 3a-3i are inclined with respect to an optical axis.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a blade drive device, such as an aperture device, and an optical device, such as a camera, that is equipped with this blade drive device. [Background technology]

[0002] Generally, a blade drive device for driving the blades includes a base member having a fixed opening corresponding to the photographic optical path, a plurality of aperture blades supported by this base member that open and close so as to enter and exit the fixed opening, and a drive plate that rotates relative to the base member; the drive plate opens and closes the plurality of aperture blades, thereby performing a series of aperture operations from maximum aperture to minimum aperture.

[0003] In such a blade drive device, when the aperture opening is reduced from a fully opened state, each blade is caused to enter the exposure opening, and the tip thereof is caused to approach the center of the optical axis.

[0004] The blade drive device described in Patent Document 1 is known as a method of assembling aperture blades called the interwoven method. In this assembly method, all aperture blades are located between two adjacent aperture blades, and are assembled so that their leading edges are visible from either the base member side or the cover member side during exposure, but not from the other side. When this method is adopted, the leading edges are intertwined and support each other, making it possible to consistently and stably maintain the specified orientation of the aperture blades compared to when multiple aperture blades are simply assembled in a stacked order. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-57715 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when the above-described interwoven method is adopted, as the aperture opening becomes smaller, each aperture blade is subjected to an external force (warping force) from the adjacent aperture blade, causing the tip of the blade to warp in a direction perpendicular to the reference plane Y0 that defines the aperture, i.e., in the direction of the central axis of the aperture (the optical axis Y1-Y2) (for example, the Y1 → Y2 direction in Figure 6). As a result, the aperture formed by the aperture blades shifts in the optical axis direction from the reference plane Y0 at full aperture and at small aperture settings. Furthermore, if the warped portion of the blade group protrudes from the blade drive device at small aperture settings, it is visually unsightly. Furthermore, it may interfere with and damage the blade drive device and adjacent lens components.

[0007] The present invention provides a blade drive device that uses a braided system to rotate multiple aperture blades to change the size of the aperture opening, and can effectively reduce the warping of the blade group that occurs as the aperture opening becomes smaller, in other words, it provides a blade drive device and an optical device equipped with the blade drive device that reduces the amount of deviation of the aperture blade tip from the aperture reference plane in the optical axis direction. [Means for solving the problem]

[0008] In order to solve the above problem, the blade drive device of the present invention is a blade drive device that adjusts the size of an aperture through which light passes by using a plurality of diaphragm blades, and is characterized in that it comprises a base member in which a fixed aperture is formed, and a drive plate that drives the plurality of diaphragm blades, each of which has a rotation shaft pin formed thereon, and the drive plate has a rotation shaft hole with which the rotation shaft pin engages, and the rotation shaft hole is inclined with respect to the optical axis. [Effects of the Invention]

[0009] The present invention provides a blade drive device that changes the size of an aperture opening by rotating a plurality of aperture blades that employ a braiding method, and an optical device equipped with the blade drive device that can effectively reduce the warping of the blade group that occurs as the aperture opening becomes smaller. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is an exploded perspective view of a blade drive device according to an embodiment of the present invention; [Figure 2] FIG. 1 is an exploded perspective view showing the rear side of a main part of a blade drive device according to an embodiment of the present invention; [Figure 3] 1A and 1B are diagrams showing the blade drive device of the first embodiment at full throttle, at intermediate throttle, and at small throttle. [Figure 4] FIG. 1 is an enlarged cross-sectional view showing a main part of the blade drive device of the first embodiment when opened. [Figure 5] FIG. 1 is an enlarged cross-sectional view showing a main part of the blade drive device of the first embodiment when the blade drive device is in an intermediate throttle position. [Figure 6] FIG. 1 is an enlarged cross-sectional view showing a main part of the blade drive device of the first embodiment when the aperture is small. [Figure 7] 1 is a perspective view of a blade drive device according to an embodiment of the present invention; [Figure 8] Schematic diagram of an optical device equipped with the blade drive device of Example 1 DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0012] Example 1 Fig. 1 is an exploded perspective view showing the configuration of a blade drive device 10 according to a first embodiment of the present invention, and Fig. 2 is an exploded perspective view showing the rear side of the main part. This blade drive device 10 comprises a base member 1 having a fixed opening 11 centered on the optical axis of light passing through and opening / closing guide cams 1a-1i, a plurality of diaphragm blades 2, a drive plate 3 that drives the diaphragm blades 2 to open and close, and a cover member 4 against which the drive plate 3 slidably abuts.

[0013] The base member 1 is generally made by resin molding. The base member 1 is a ring-shaped member that forms a fixed opening 11, and has protrusions 12a to 12g that serve as multiple support parts that support the drive plate 3 and form a sliding space A for the diaphragm blades 2, and multiple opening / closing guide cams 1a to 1i that correspond to the number of the diaphragm blades 2.

[0014] The opening / closing guide cams 1a to 1i are engaged with cam pins 21b provided on one side of the base portion 21a of the diaphragm blade 2. The cam pins 21b move along the opening / closing guide cams 1a to 1i, respectively, to open and close the diaphragm blades.

[0015] The drive plate 3 is generally made in a ring shape by resin molding. A gear 3j is formed on part of the outer periphery of the drive plate 3, which engages with a rotary gear 6 of a drive motor 5 attached to a cover member 4 to rotate it. The drive motor 5 can rotate clockwise and counterclockwise, and the rotation of the drive motor 5 causes the drive plate 3 to turn within a set rotation range. Cam pins 21b of the multiple diaphragm blades 2 and rotary shaft pins 21c provided on the opposite side engage with the multiple provided rotary shaft holes 3a to 3i, respectively, thereby opening and closing the diaphragm blades and changing the diaphragm aperture to adjust the amount of light.

[0016] The aperture blades in this embodiment are made up of nine aperture blades 2, each provided with a cam pin 21b and a rotation axis pin 21c. The bases 21a of the aperture blades are arranged at equal angular intervals around the optical axis, and portions of the blades overlap to form an aperture on the inner periphery of the aperture blade 2. Rotation of the drive plate 3 changes the overlap between the blades, thereby continuously changing the size of the aperture.

[0017] A rotation shaft pin 21c and a cam pin 21b are attached to a blade base 21a of the diaphragm blade 2. The blade base 21a, the rotation shaft pin 21c, and the cam pin 21b of the diaphragm blade 2 are integrally formed by resin molding.

[0018] Furthermore, the blade base 21a of the diaphragm blade 2 may be made from a light-shielding sheet material, and the rotation shaft pin 21c and the cam pin 21b may be made by resin molding and integrated with the blade base 21a by bonding, welding, outsert molding, etc. Alternatively, the rotation shaft pin 21c and the cam pin 21b may be formed from a metal pin and integrated with the blade base 21a by bonding, welding, caulking, etc.

[0019] The cover member 4 has a fitting hole 4j for attaching the drive motor 5, and may be provided with a mounting shape when the blade drive device 10 is incorporated into an optical device such as an interchangeable lens for a single-lens reflex camera. Like the base member 1, it is formed into a ring shape using a resin mold, and protrusions 4a to 4h provided in the circumferential direction on the inner diameter side slide against the outer periphery 31 of the drive plate 3, thereby rotatably supporting the drive plate 3.

[0020] In practice, the drive motor 5 is rotated in one direction and then rotated in the opposite direction, causing the drive plate 3 to rotate back and forth. This causes each diaphragm blade 2 to rotate in the direction of narrowing and widening the diaphragm aperture, respectively, thereby changing the diaphragm aperture.

[0021] In this embodiment, when the aperture of the diaphragm blades 2 is formed by the reciprocating rotation of the drive plate 3, the engagement structure between the rotation shaft pins 21c of each diaphragm blade 2 and the rotation shaft holes 3a to 3i of the drive plate 3 is devised.

[0022] Specifically, the drive plate 3 has a plurality of rotation shaft holes 3a-3i, which engage with the rotation shaft pins 21c of the plurality of diaphragm blades 2, and these are inclined by α degrees so that the diaphragm blade sliding space A side of the drive plate 3 approaches the optical axis Y1-Y2 (see FIG. 6). Here, α is set to 3 degrees. Preferably, an angle of 1 to 5 degrees prevents excessive curvature of the blades, and the curvature tends to remain within an appropriate range. A particularly preferred angle is between 2 and 4 degrees.

[0023] FIG. 3 shows, from the left, the blade drive device 10 at full aperture (a), at intermediate aperture (b), and at small aperture (c). FIG. 4 is a cross-sectional view taken at the center of the rotation shaft hole of the drive plate 3 at the open aperture position. FIG. 5 is the same cross-sectional view at the intermediate aperture position, and FIG. 6 is the same cross-sectional view at the small aperture position. In order to show the main parts, the rotation shaft hole of the drive plate 3 and the warped state of the blades are shown schematically.

[0024] As a result, when the aperture opening is changed by the rotation of drive plate 3, diaphragm blade 2 forms the aperture opening inside aperture 11 while being tilted by the amount of tilt of the rotation shaft hole. Regarding the tilt of the rotation shaft hole at this time, in this embodiment, as shown in Fig. 6, the rotation shaft hole is tilted by α degrees so that the side of the rotation shaft hole that faces aperture blade sliding space A approaches the optical axis Y1-Y2, but the tilt direction of the rotation shaft hole may also be tilted so that the rotation shaft hole on the blade tip side approaches the optical axis when the blade is curled up depending on the direction in which the blade curls up, or the rotation shaft hole may be tilted in the direction of a line connecting the center of the optical axis and the center of the rotation shaft hole (radial direction) so that the side of the drive plate that faces aperture blade sliding space A approaches the optical axis.

[0025] As mentioned above, the drive plate 3 is generally made into a ring shape by resin molding, but since the rotation axis hole needs to be molded at an angle, the injection molding mold needs to have a slide structure. 3D printers and other parts molding technologies are expected to be used in the future when they can achieve the same level of precision as current injection molding.

[0026] In the blade drive device of the present invention, as shown in Figures 4, 5, and 6, each diaphragm blade 2 is supported by rotation shaft holes 3a-3i inclined by α degrees in the drive plate 3, and is therefore assembled with a predetermined inclination. Therefore, even at the widest aperture to intermediate aperture positions, the diaphragm aperture formed on the inner periphery of the diaphragm blade protrudes slightly in the Y1 direction. When the aperture is set to a small aperture, the warping force generated in each diaphragm blade 2 pushes the tip portion downward in the Y2 direction, causing the diaphragm blade to warp upward. However, because the diaphragm blade 2 already protrudes in the Y1 direction at the widest aperture position, the protrusion of the tip portion of the diaphragm blade 2 in the Y2 direction can be reduced even at the small aperture position. This minimizes the overall deviation of the diaphragm aperture formed by the diaphragm blade from the reference plane Y0 in the optical axis direction when the diaphragm aperture is set to the widest aperture and the smallest aperture. In addition, as shown in Figure 6, the tip of the diaphragm blade 2 can be reduced from protruding from the blade drive device at the small aperture position, which improves the appearance and prevents the blade drive device from interfering with and damaging adjacent lens components.

[0027] Furthermore, as described above, the blade drive device of the present invention can reduce the amount of deviation of the diaphragm aperture position in the optical axis direction, making it possible to provide an optical device that is more advantageous and offers greater freedom in optical design, such as lens spacing.

[0028] <Example 2> FIG. 8 shows an interchangeable lens 221 for a single-lens reflex camera, which is an optical device equipped with the blade drive device described in the first embodiment, and the internal configuration of the camera body to which the interchangeable lens is attached.

[0029] The lens barrel of the interchangeable lens 221 houses a photographing optical system including a variable magnification lens 232, the blade drive device 10 of the first embodiment that narrows the optical path, and a focus lens 229.

[0030] An image sensor 225, which is configured with a photoelectric conversion element such as a CCD sensor or a CMOS sensor, is disposed inside the camera body and photoelectrically converts the subject image formed by the interchangeable lens 221 to output an electrical signal. 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 by changing the aperture of the blade drive device 10 or by moving an ND filter (not shown) forward or backward.

[0031] 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, thereby generating an image signal.

[0032] A user can change the magnification (zoom) by moving a variable magnification lens 232 by rotating a zoom ring 231. The controller 222 detects the contrast of an image signal, controls a focus motor 228 in accordance with the contrast, and moves a focus lens 229 to perform autofocus. Alternatively, the controller 222 may control the focus motor 228 and move a focus lens 229 to perform autofocus based on a detection signal from a focus detection means that uses a phase difference detection method (not shown).

[0033] Furthermore, the controller 222 controls the drive unit 5 of the blade drive device 10 based on the photometric value of a photometric means (not shown) or an image signal, and adjusts the amount of light. This makes it possible to make blur and ghosting during shooting natural, and to record high-quality images.

[0034] The present invention is not limited to the single-lens reflex camera described above, but can also be widely applied to optical devices such as digital cameras with an integrated lens, video cameras, and the like. [Explanation of symbols]

[0035] 1 Base material 2 aperture blades 3 Drive Plate 4 Cover member 5 Drive unit 6 Pinion

Claims

1. A blade drive device that adjusts the size of an aperture through which light passes by a plurality of diaphragm blades, a base member having a fixed opening formed therein; a drive plate for driving the plurality of diaphragm blades, each of which has a rotation shaft pin formed thereon; The driving plate has a rotation shaft hole with which the rotation shaft pin is engaged, and the rotation shaft hole is inclined with respect to the optical axis. A blade drive device characterized by:

2. The blade drive device of claim 1, The blade drive device is characterized in that the rotation shaft hole is inclined so that the side of the drive plate where the diaphragm blade slides approaches the optical axis.

3. The blade drive device of claim 1, The blade drive device is characterized in that the rotation shaft hole is inclined so that the curved up side of the blade of the drive plate approaches the optical axis.

4. The blade drive device of claim 1, The rotation shaft hole is inclined in the direction of a line connecting the center of the optical axis and the center of the rotation shaft hole so that the diaphragm blade sliding space side of the drive plate approaches the optical axis. A blade drive device characterized by:

5. An optical device comprising: the blade drive device according to claim 1; and an imaging element that captures an image of light that has passed through the blade drive device.

Images