Pan / tilt head and imaging device

Abstract

To provide a pan / tilt head or the like that can reduce rattling or vibration during sudden changes in rotation while also reducing unevenness in rotational speed to achieve smooth rotational drive, a pan / tilt head is provided. The head includes: a drive unit that rotates a camera unit in a predetermined direction; a first gear and a second gear that rotate in a predetermined direction about a predetermined rotation axis and are coaxial with the predetermined rotation axis; a third gear that meshes with the first gear and the second gear and transmits driving force from the drive unit; and a biasing unit that biases the second gear in the direction of the rotation axis, wherein the first gear, the second gear, and the third gear include helical gears, and the second gear is arranged to be movable relative to the first gear in the direction of the rotation axis. An imaging device including the pan / tilt head is also provided.

Description

Technical Field

[0001] The present invention relates to a pan or tilt platform for rotating a camera unit in a predetermined direction and an imaging device. Background Art

[0002] Video cameras used for shooting in small studios and live broadcasts are known as imaging devices that pan and tilt a camera unit. These cameras require a large and heavy lens barrel to obtain high-quality images, and they also require a large driving force. Furthermore, to achieve smooth camera operation and image expression, smooth rotational drive is required over a wide speed range, from low to high.

[0003] Japanese Patent Publication No. 2005-323187 describes a configuration that uses a timing belt and pulleys as a rotational drive mechanism for panning and tilting, enabling smooth rotational drive. According to Japanese Patent Publication No. 2005-323187, since the timing belt eliminates backlash in the drive mechanism, rattling noises during panning or tilting of the camera are reduced, enabling smooth rotational drive. However, since the timing belt is an elastic member, there is a problem in that, when a large lens barrel is driven at high acceleration or stopped, the belt's bending and expansion / contraction can cause image jitter.

[0004] On the other hand, Japanese Patent Publication No. 2009-55076 describes a so-called "scissor gear" technology, in which one of a pair of spur gears meshing with each other as a rotational drive mechanism is split into two gears in the thickness direction, and one of the two split gears is biased in the circumferential direction about the rotation axis by a spring or the like. In the scissor gear structure, backlash can be eliminated, and rattling noise during rotational drive can be suppressed.

[0005] Figure 7 Shown is a structural example using conventional scissor gears as a pan and tilt drive mechanism for a camera unit. Figure 7 As shown in , in a scissor gear configuration using conventional spur gears, a first spur gear 51 is fixed to a tilting shaft 52 or a pan shaft (not shown) and meshes with a gear portion of a gear pulley 53 to transmit a driving force of a motor 56 .

[0006] Here, the second spur gear 54 is biased in the circumferential direction around the rotation axis by a biasing member such as a coil spring 55. Therefore, the teeth of the gear portion of the gear pulley 53 are sandwiched between the teeth of the first spur gear 51 and the teeth of the second spur gear 54, thereby eliminating backlash.

[0007] However, in the related art disclosed in Japanese Patent Publication No. 2009-55076, because the gear portion is always in strong contact with the gear on the other side (due to the scissor-type gear biasing structure), there is a concern that unevenness in the transmitted torque may become greater (due to the rotational phase of the gears). In particular, when the camera is panned or tilted at a low speed, speed unevenness may occur, and the image may be shaken.

[0008] To reduce unevenness in the transmitted torque, it is necessary to weaken the biasing force of the scissor gear's spring, etc. However, since a large torque is applied due to inertia when a large lens barrel suddenly stops from high-speed rotation, if the biasing force is weak, the torque causes the lens barrel to vibrate and results in image shake.

[0009] Specifically, the scissor-type gear structure with spur gears has the following problems: When the biasing force is large, the speed becomes uneven, especially in low-speed driving conditions. On the other hand, when the biasing force is small, the torque generated by the inertia of the lens barrel cannot be maintained, causing the lens barrel to vibrate.

[0010] For example, in Figure 7 In the illustrated configuration example, when the biasing force applied to the second spur gear 54 is weak, the torque generated by the inertia of the camera unit 50 when the camera unit 50 is quickly tilted or panned and suddenly stopped exceeds the force of the coil spring 55. Therefore, the camera unit 50 vibrates.

[0011] On the other hand, when the biasing force applied to the second spur gear 54 is strong, it is possible to suppress vibration of the camera unit when the camera unit is tilted or panned at high speed or when it is suddenly stopped. However, the teeth of the first spur gear 51 and the teeth of the second spur gear 54 strongly contact the teeth of the gear portion of the gear pulley 53, causing large unevenness in the transmitted torque due to the rotational phase of the gears.

[0012] For this problem, for example, even in control to rotate the camera unit 50 at a certain constant speed in the tilt or pan direction, the rotation speed becomes uneven due to uneven torque, which causes a captured image to be blurred.

[0013] Figure 8 This is an example of the panning speed of the camera unit 50 when the biasing force applied to the second spur gear 54 is weak. Although the trapezoidal wave speed is input, by looking at the actual panning speed, it can be seen that vibration occurs at the start and stop due to the weak force of the coil spring 55. Figure 9 is an example depicting the translation speed of the camera unit 50 when the biasing force applied to the second spur gear 54 is strong. In this case, it can be seen that vibrations at the time of starting and stopping can be suppressed, but the speed is not kept constant due to unevenness of the transmitted torque.

[0014] An object of the present invention is to provide a pan or tilt head or the like which can reduce rattles and vibrations during sudden changes in rotation while reducing non-uniformity in rotation speed for smooth rotational drive. Summary of the Invention

[0015] In order to achieve the above-mentioned purpose, the pan or tilt head of the claimed invention includes: a driving unit, which causes the camera unit to rotate in a predetermined direction; a first gear and a second gear, which rotate in a predetermined direction around a predetermined rotation axis and are coaxial with the predetermined rotation axis; a third gear, which engages with the first gear and the second gear and transmits the driving force from the driving unit; and a biasing unit, which biases the second gear in the direction of the rotation axis, wherein: the first gear, the second gear and the third gear include helical gears, and the second gear is arranged to be able to move in the direction of the rotation axis relative to the first gear.

[0016] Other features of one or more embodiments of the claimed invention will become apparent from the following description of the embodiments with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a perspective view showing a video camera according to an embodiment of the present invention.

[0018] Figure 2 is a perspective view showing the tilt drive mechanism of the video camera of this embodiment.

[0019] Figure 3 is an exploded perspective view showing the helical gear of this embodiment.

[0020] Figure 4 Schematic diagram showing the meshing of the helical gears of this embodiment.

[0021] Figure 5 is a perspective view showing a panning drive mechanism of the video camera of this embodiment.

[0022] Figure 6 is a graph depicting the panning speed characteristics of the video camera of this embodiment.

[0023] Figure 7 is a perspective view showing an example of a driving mechanism of a conventional video camera.

[0024] Figure 8 is a graph depicting an example of panning speed characteristics of a conventional video camera.

[0025] Figure 9 is a graph depicting another example of the panning speed characteristics of a conventional video camera. DETAILED DESCRIPTION

[0026] Hereinafter, an advantageous mode of the present invention will be described using an embodiment with reference to the accompanying drawings. In each of the drawings, the same reference numerals are applied to the same parts or elements, and repeated descriptions will be omitted or simplified.

[0027] Furthermore, this embodiment will introduce an example in which a web camera used as an imaging device in live streaming, etc. is combined with a pan / tilt head for panning and tilting. However, the imaging device includes electronic devices such as digital still cameras, digital movie cameras, smartphones with cameras, tablet computers with cameras, and car cameras with imaging functions.

[0028] Figure 1 is a perspective view showing a video camera 100 according to an embodiment of the present invention.

[0029] like Figure 1 As shown in FIG, a video camera (web camera) 100 as an imaging device of the present embodiment includes a camera unit 10 , a panning unit 11 , and a base portion 12 .

[0030] Figure 1 The video camera 100 shown in FIG. 1 is mounted on the ceiling of a live broadcast room or a filming studio, for example, as a fixed surface. The camera unit 10 is capable of rotating in pan and tilt directions. By panning and tilting the camera unit 10 toward a subject, video can be captured for video production and live streaming. Furthermore, the video camera 100 can be mounted not only on the ceiling but also on a horizontal surface to capture images.

[0031] When the camera unit 10 pans and tilts, it is possible to capture blur-free images by smoothly driving the camera unit 10 without any unevenness in rotational speed. Furthermore, the camera unit 10 can perform panning and tilting operations over a wide speed range, from high speed to low speed. Therefore, by enabling the camera unit 10 to follow the subject, it is possible to capture images even of subjects moving at uneven speeds.

[0032] In this way, the video camera 100 can rotate the camera unit 10 in both pan and tilt directions. Here, the pan unit 11 and the base portion 12 constitute a pan / tilt head for rotating the camera unit 10 in both pan and tilt directions. Furthermore, in this embodiment, the camera unit 10 is attached to the pan / tilt head and cannot be attached or detached by the user. However, the camera unit 10 can be easily attached to or detached from the pan / tilt head.

[0033] Next, the tilt drive mechanism 200 of the video camera 100 will be described. The tilt drive mechanism 200 is arranged in the pan unit 11.

[0034] Figure 22 is a perspective view showing the tilt drive mechanism 200 of the video camera 100. The tilt drive mechanism (tilt drive unit) serves as a rotation drive unit for rotating the camera unit 10 in a predetermined tilt direction. While this embodiment describes a configuration capable of both panning and tilting, it is also possible to rotate in only one direction.

[0035] like Figure 2 As shown in FIG, the lens barrel 13 in the camera unit 10 is supported by a lens barrel support member 14 including a tilt shaft 15. The lens barrel support member 14 is tiltably supported by a pan base 16 in the pan unit 11.

[0036] Here, the camera unit 10 rotates in the tilt direction by a tilt drive mechanism 200. The tilt drive mechanism 200 includes a tilt motor 20 as a drive source, a rubber 21, a timing belt 22, a gear pulley 23, a first helical gear 24, a second helical gear 25, and the like. Furthermore, the gear pulley 23 includes a pulley portion 23B and a gear portion 23A, which is a helical gear. Here, the first helical gear 24 and the second helical gear 25 serve as the first and second gears, respectively, that rotate in a predetermined direction about a predetermined rotation axis and are coaxial with the predetermined rotation axis. Furthermore, the gear portion 23A serves as a third gear that transmits the driving force from the drive source.

[0037] The tilt motor 20 is attached to the pan unit 11 via rubber 21, and the gear pulley 23 is rotatably supported by the pan unit 11. The tilt motor 20 and the pulley portion 23B of the gear pulley 23 are connected by a timing belt 22. A first bevel gear 24 is fixed so that its center substantially coincides with the tilt shaft 15, and is arranged to mesh with the gear portion 23A of the gear pulley 23.

[0038] Therefore, when the tilt motor 20 is driven, the gear pulley 23 rotates via the timing belt 22 and also transmits the rotation to the first bevel gear 24 meshing with the gear portion 23A of the gear pulley 23 , so that the camera unit 10 can be tilted.

[0039] The following will refer to Figure 3 A structure for eliminating backlash of the first bevel gear 24 of the tilt drive mechanism 200 will be described.

[0040] Figure 3 It is an exploded perspective view showing the helical gears 24 and 25 .

[0041] like Figure 3As shown in FIG, the second helical gear 25 is arranged so as to be non-rotatable relative to the first helical gear 24 and movable in a direction parallel to the rotation axis. Furthermore, the second helical gear 25 is fixed to the first helical gear 24 via a coil spring 28 and a spring retainer 26, and is always biased in the direction of the rotation axis so as to approach the first helical gear 24. Furthermore, the plurality of coil springs 28 may be elastic members and serve as a biasing unit.

[0042] When the first helical gear 24 meshes with the gear portion 23A of the gear pulley 23, backlash is generated. However, the backlash can be eliminated by biasing the second helical gear 25 with the coil spring 28, as shown in FIG. Figure 4 As shown in .

[0043] The structure for eliminating this backlash is such that the teeth of the gear portion 23A of the gear pulley 23 are sandwiched between the teeth of the first helical gear 24 and the teeth of the second helical gear 25, thereby forming a so-called scissor gear structure. With this structure, when the camera unit 10 is rotated in the tilt direction, the rattling sound caused by the backlash is eliminated, and smooth operation is achieved.

[0044] When the camera unit 10 is rapidly tilted and suddenly stopped, a torque is applied to the second bevel gear 25 due to the inertia of the camera unit 10. The force generated in one tooth of the second bevel gear 25 by this torque is given by Figure 4 F1 indicates.

[0045] Figure 4 Schematic diagram showing the meshing of the helical gears 24 and 25 .

[0046] Assuming that the helix angle of the second helical gear 25 is θ, F1 can be decomposed into a force F1 cos θ in a direction perpendicular to the tooth surface and a force F1 sin θ in a direction in contact with the tooth surface.

[0047] When the second helical gear 25 slips and moves in the axial direction due to F1 sin θ, a configuration for eliminating backlash cannot be established. Therefore, by setting the biasing force F2 of the coil spring 28 to a large value and suppressing slippage due to F1 sin θ, a configuration capable of always eliminating backlash is maintained.

[0048] Since F1 sin θ is small when the helical angle θ is set to a small value of 45° or less (in this embodiment, θ = 15°), backlash can be eliminated even when the biasing force F2 of the coil spring 28 is set to a small value. Furthermore, by reducing the biasing force F2, it is possible to prevent the second helical gear 25 and the gear portion 23A of the gear pulley 23 from strongly colliding. Therefore, it is possible to reduce the unevenness of the transmitted torque caused by the rotational phase of the gears, and the camera unit 10 can be tilted smoothly.

[0049] Thus far, the structure for eliminating backlash of the first helical gear 24 has been described. By biasing the second helical gear 25 in the thrust direction, backlash can be eliminated by clamping the teeth of the gear portion 23A of the gear pulley 23. The structure for biasing the second helical gear 25 will be described in detail below.

[0050] like Figure 3 As shown in FIG, the first helical gear 24 includes three arcuate ribs 24A having arcuate portions of the same radius, and the arcuate ribs 24A are arranged circumferentially around the rotation axis so that the center of the arc substantially coincides with the rotation axis. Furthermore, the inner diameter portion of the second helical gear 25 is arranged to fit onto the outer peripheral portion of the arcuate ribs 24A.

[0051] Since there is a slight backlash when the inner diameter portion of the second helical gear 25 is assembled, the second helical gear 25 may be slightly tilted diagonally due to the backlash.

[0052] However, since the outer diameter of the arcuate rib 24A is larger than the outer diameter of the tilt shaft 15, the inclination of the second helical gear 25 can be suppressed to be smaller than when the second helical gear 25 is directly attached to the outer diameter portion of the tilt shaft 15. Moreover, the coil springs 28 are arranged alternately with the arcuate ribs 24A.

[0053] With this configuration, the biasing force can be applied near the outer periphery while maintaining a large fitting diameter of the second helical gear 25. Inclination of the second helical gear 25 due to a change in the biasing force can be suppressed small by applying the biasing force near the outer periphery.

[0054] The following will refer to Figure 2 The following describes the attachment shape of the tilt motor 20 in the tilt drive mechanism 200. The tilt motor 20 is attached to a support metal plate 27 via rubber 21, and the support metal plate 27 is attached to the pan base 16. Furthermore, the driving force of the tilt motor 20 can be transmitted to the gear pulley 23 via the timing belt 22.

[0055] Since the rubber 21 and the timing belt 22 are both components having low rigidity, the vibration of the tilt motor 20 is less likely to be transmitted to the pan base 16 or the gear pulley 23. Therefore, the captured image shaking due to the vibration of the tilt motor 20 can be prevented.

[0056] Next, description will be given of the panning drive mechanism 300 of the video camera 100. The panning drive mechanism (panning drive unit) 300 functions as a rotation drive unit that rotates the camera unit 10 in a predetermined panning direction.

[0057] Figure 5 FIG is a perspective view showing the panning drive mechanism 300 of the video camera 100. Figure 5 As shown in FIG, the pan base 16 includes a pan shaft 17 and is supported by the base portion 12 so as to be pan-rotatable.

[0058] The rotation of the camera unit 10 in the panning direction is performed by the panning drive mechanism 300. Figure 5 As shown in FIG, panning drive mechanism 300 includes panning motor 30, rubber 31, timing belt 32, gear pulley 33, first helical gear 34, second helical gear 35, etc. Also, gear pulley 33 includes pulley portion 33B and gear portion 33A, which is a helical gear.

[0059] Pan motor 30 is attached to base portion 12 via rubber 31, and gear pulley 33 is rotatably supported by base portion 12. Pan motor 30 and pulley portion 33B of gear pulley 33 are connected by a timing belt 32. A first bevel gear 34 is fixed so that its center substantially coincides with pan shaft 17 and is arranged to mesh with gear portion 33A of gear pulley 33.

[0060] Therefore, when the pan motor 30 is driven, the gear pulley 33 is rotated via the timing belt 32, and the rotation is transmitted to the first bevel gear 34 meshing with the gear portion 33A of the gear pulley 33. Then, the pan base 16 can be panned, and thus the camera unit 10 can be panned.

[0061] The second bevel gear 35 is arranged to be non-rotatable relative to the first bevel gear 34 and to be movable parallel to the rotation axis. Figure 3 As shown in FIG, the second bevel gear 35 is fixed to the first bevel gear 34 by a coil spring 38 and a spring retainer 36 and is always biased in a direction approaching the first bevel gear 34.

[0062] The panning motor 30 is attached to a supporting metal plate 37 attached to the base portion 12 through rubber 31 .

[0063] These configurations are the same as those of the tilt drive mechanism 200 and can smoothly perform panning by eliminating backlash.

[0064] Figure 6 is a graph depicting the panning speed characteristics of the video camera 100 .

[0065] Even during sudden acceleration or stop, backlash is reduced so that vibration does not occur, and even during constant speed rotation, smooth rotation with little speed unevenness can be achieved.

[0066] In the present embodiment, the camera unit 10 is rotatable in the tilt direction and the pan direction, but may be rotatable in any one of the tilt direction and the pan direction.

[0067] Furthermore, in this embodiment, the tilt drive mechanism 200 and the pan drive mechanism 300 are two-stage speed reduction mechanisms, but they may also be three-stage or more speed reduction mechanisms.

[0068] While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

[0069] This application claims the benefit of Japanese Patent Application No. 2020-187342, filed November 10, 2020, which is incorporated herein by reference in its entirety.

Claims

1. A pan or tilt head, comprising: a driving unit that causes the camera unit to rotate in a predetermined direction; a first gear and a second gear, the first gear and the second gear rotating about a predetermined rotation axis in the predetermined direction and being coaxial with the predetermined rotation axis; a third gear engaged with the first gear and the second gear and transmitting a driving force from the driving unit; as well as a plurality of biasing units, the plurality of biasing units biasing the second gear in a predetermined rotation axis direction, wherein: The first gear, the second gear, and the third gear include helical gears, The second gear is arranged to be movable relative to the first gear along the predetermined rotation axis direction; The first gear includes a plurality of arcuate ribs, wherein the plurality of arcuate ribs are at the same distance from the predetermined rotation axis; Each of the plurality of arc-shaped ribs is arranged such that a center of an arc substantially coincides with the predetermined rotation axis and is located at a position separated in a radial direction from an outer peripheral portion of the predetermined rotation axis; an inner peripheral portion of the second gear being fitted to outer peripheral portions of the plurality of arc-shaped ribs; and The plurality of biasing units are alternately arranged with the plurality of arc-shaped ribs along a circumference centered on the predetermined rotation axis.

2. The pan or tilt head according to claim 1, wherein: The helix angle of the first gear, the second gear, and the third gear is 45° or less.

3. The pan or tilt head according to claim 1, wherein: The third gear includes a pulley portion that meshes with the timing belt.

4. The pan or tilt head according to claim 3, wherein: The pulley portion is configured to transmit driving force from the drive unit through the timing belt.

5. The pan or tilt head according to claim 1, wherein: The predetermined direction includes at least one of a panning direction and a tilting direction.

6. The pan or tilt head according to claim 1, further comprising: a panning drive unit, configured to rotate the camera unit in a panning direction; as well as a tilt drive unit that rotates the camera unit in a tilt direction, The panning drive unit and the tilting drive unit each include a drive unit, a first gear, a second gear, and a third gear. The first gear, the second gear, and the third gear include helical gears, The second gear is arranged to be movable relative to the first gear in the direction of the predetermined rotation axis; and The plurality of biasing units are provided to bias the second gear in the predetermined rotation axis direction.

7. An imaging device comprising: A pan or tilt head, comprising: a driving unit for rotating a camera unit in a predetermined direction; a first gear and a second gear for rotating about a predetermined rotation axis in the predetermined direction and coaxial with the predetermined rotation axis; a third gear for engaging with the first gear and the second gear and transmitting a driving force from the driving unit; and a plurality of biasing units for biasing the second gear in the direction of the predetermined rotation axis; and A camera unit, the camera unit being attachable to a pan or tilt head; wherein: The first gear, the second gear, and the third gear include helical gears; The second gear is arranged to be movable relative to the first gear along the predetermined rotation axis direction; The first gear includes a plurality of arcuate ribs, wherein the plurality of arcuate ribs are at the same distance from the predetermined rotation axis; Each of the plurality of arc-shaped ribs is arranged such that a center of an arc substantially coincides with the predetermined rotation axis and is located at a position separated in a radial direction from an outer peripheral portion of the predetermined rotation axis; an inner peripheral portion of the second gear being fitted to outer peripheral portions of the plurality of arc-shaped ribs; and The plurality of biasing units are alternately arranged with the plurality of arc-shaped ribs along a circumference centered on the predetermined rotation axis.

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