Optical device and imaging apparatus

Abstract

To provide an optical device capable of stably driving a moving lens barrel.SOLUTION: A lens device 100 includes: a first moving lens barrel 5; a guide shaft 8 which is movably connected through a compression coil spring 10; and a cam tube 2. A first driving cam follower 5b is provided in the first moving lens barrel 5. An energizing cam follower 5c is provided in the guide shaft 8. A first cam groove 2a is provided in the cam tube 2. The first cam groove 2a includes a cam surface 2d on which the first driving cam follower 5b is abutted and a cam surface 2f on which the energizing cam follower 5c is abutted. When an angle formed by the cam surface 2d and a first axis D1 at a contact point between the first driving cam follower 5b and the cam surface 2d is defined as β1, an angle formed by the cam surface 2f and a second axis at a contact point between the energizing cam follower 5c and the cam surface 2f is defined as β2, an energizing force of the compression coil spring 10 is defined as P, and a rotational force required for rotating the cam tube 2 is defined as F, a conditional expression of |1 / tanβ1-1 / tanβ2|<F / P is satisfied.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to an optical device and an imaging device. [Background technology]

[0002] In a lens in which a movable lens barrel moves linearly in the optical axis direction according to the trajectory of a cam attached to a rotatable cam member, there is a configuration in which the cam follower is biased against the cam by the biasing force of an elastic member, thereby avoiding an engagement gap between the cam and the cam follower.

[0003] Patent Document 1 discloses a configuration in which a cam pin provided on a lens support frame of a variable magnification lens group engages with one side of a cam groove, and a cam pin provided on a lens support frame of an aberration correction lens group engages with the other side of the cam groove, and the cam pins are biased by a coil spring in directions away from each other. Patent Document 2 discloses a configuration in which a biasing member biases a movable barrel driven by a first cam follower engaged with a first cam portion and a support member driven by a second cam follower engaged with a second cam portion in directions away from each other in the optical axis direction. Patent Document 3 discloses a configuration in which a coil spring biases a lens holding barrel driven by a first cam follower engaged with a first cam surface and a support member driven by a second cam follower engaged with a second cam surface in directions away from each other in the optical axis direction. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-326734 [Patent Document 2] Japanese Patent Application Laid-Open No. 2000-304996 [Patent Document 3] Japanese Patent Publication No. 2020-20825 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the configuration disclosed in Patent Document 1, the cam shapes of the opposing cam surfaces are determined based on their respective optical requirements, so there is a risk that an unintended rotational force will be generated in the cam member (zoom cam member) due to the biasing force. Also, in the configuration disclosed in Patent Document 2, there is a risk that extension of the cam member (rotating barrel) due to expansion of the cam in the optical axis direction will be unavoidable. Furthermore, Patent Document 3 is silent about the shape of the engagement surface of the biasing cam follower (second cam follower) in the actual use range of the lens barrel drive cam follower (first cam follower).

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an optical device that can stably drive a moving lens barrel. [Means for solving the problem]

[0007] In order to achieve the above object, an optical device of the present invention comprises a movable lens barrel movable in the optical axis direction, a movable member connected to the movable lens barrel via an elastic member so as to be movable in the optical axis direction, and a cam member that moves the movable lens barrel by rotating, wherein the movable lens barrel is provided with a first cam follower, the movable member is provided with a second cam follower, the cam member is provided with a cam groove with which the first and second cam followers engage, the cam groove includes a first curved surface with which the first cam follower abuts and a second curved surface with which the second cam follower abuts, wherein an angle formed by the first curved surface and a first axis parallel to the optical axis at a point of contact between the first cam follower and the first curved surface is β1, an angle formed by the second curved surface and a second axis parallel to the optical axis at a point of contact between the second cam follower and the second curved surface is β2, an urging force in the optical axis direction by the elastic member is P, and a rotational force required to rotate the cam member is F, |1 / tanβ1-1 / tanβ2| <F / P The present invention is characterized in that the following condition is satisfied: [Effects of the Invention]

[0008] According to the present invention, an optical device capable of stably driving a moving lens barrel can be provided. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view of a lens device 100 according to an embodiment, taken along a plane including an optical axis. [Figure 2] FIG. 2 is a cross-sectional view taken along the line II-II in FIG. [Figure 3] FIG. 3 is a cross-sectional view taken along the line III-III in FIG. 2. [Figure 4] FIG. 3 is an enlarged view of part A in FIG. 2. [Figure 5] FIG. 2 is a development view of a cam groove portion of the cam tube 2. [Figure 6] FIG. 6 is an enlarged view of part B in FIG. 5. [Figure 7] FIG. 1 is a schematic diagram illustrating an example of the configuration of an imaging device. DETAILED DESCRIPTION OF THE INVENTION

[0010] (Example) A lens device 100 (optical device) according to an embodiment of the present invention will be described below with reference to the accompanying drawings. In all the drawings for describing the embodiment, the same components are generally designated by the same reference numerals (unless otherwise specified), and repeated description thereof will be omitted. Fig. 1 is a cross-sectional view of the lens device 100 according to the embodiment of the present invention, taken along a plane including the optical axis OA.

[0011] The lens device 100 includes a lens body 100a, a rectangular lens cover 100b that covers the outer periphery of the lens body 100a, and a mount 100c for connecting to a camera device 200 (see FIG. 7). The lens body 100a includes a focus lens group FL including a focusing optical system, a zoom lens group ZL including a variable magnification optical system, a relay lens group RL including an imaging optical system, and a control board (not shown). The lens body 100a holds a fixed barrel 1.

[0012] Lens device 100 further includes a cylindrical cam tube 2 (cam member), a first movable lens barrel 5 (movable lens barrel) that is movable in the optical axis direction, a second movable lens barrel 6, and a third movable lens barrel 7. One end of cam tube 2 is supported by fixed barrel 1 via bearing 3, and the other end is supported by bearing 4, so that cam tube 2 is rotatable around rotation axis CA that is parallel to optical axis OA. Cam tube 2 is provided with first cam groove 2a (cam groove), second cam groove 2b, and third cam groove 2c, and cam tube 2 is rotated manually or by electric drive means (not shown). The rotation of cam tube 2 can move first movable lens barrel 5. In addition, on the inner circumference of the fixed barrel 1, three first guide grooves 1a are provided to guide the first movable barrel 5 in the optical axis direction, three second guide grooves 1b are provided to guide the second movable barrel 6 in the optical axis direction, and three third guide grooves 1c are provided to guide the third movable barrel 7 in the optical axis direction.

[0013] Figure 2 is a cross-sectional view taken along the line II-II in Figure 1. Three sets of first guide cam followers 5a protrude from the first moving lens barrel 5, and multiple sets of them are arranged in the optical axis direction. Similarly, three sets of second guide cam followers 6a protrude from the second moving lens barrel 6, and three sets of third guide cam followers 7a protrude from the third moving lens barrel 7, and multiple sets of each are arranged in a row. Furthermore, the first moving lens barrel 5 is provided with first drive cam followers 5b (first cam followers), the second moving lens barrel 6 is provided with second drive cam followers 6b (see Figure 1), and the third moving lens barrel 7 is provided with third drive cam followers 7b (see Figure 1).

[0014] 3 is a cross-sectional view taken along the line III-III in FIG. 2. The first moving lens barrel 5 is provided with a fitting hole 5d in the optical axis direction, through which a guide shaft 8 (moving member) is slidably inserted. A rotation restricting pin 9 is fitted into a long groove 8a provided in the guide shaft 8 and extending in the optical axis direction, so that the guide shaft 8 is restricted from rotating but is allowed to slide only in the optical axis direction. A compression coil spring 10 (elastic member) is fitted into the guide shaft 8, and a biasing force P (see FIG. 6) of the compression coil spring 10 acts in the optical axis direction. That is, the guide shaft 8 is connected to the first moving lens barrel 5 via the compression coil spring 10 so as to be movable in the optical axis direction.

[0015] Fig. 4 is an enlarged view of part A in Fig. 2. The first driving cam follower 5b is composed of a shaft 11, a bearing 12, and a screw 13, and the outer periphery of the bearing 12 is journaled so as to be rotatable relative to the shaft 11. The biasing cam follower 5c (second cam follower) is composed of a shaft 14, a bearing 15, and a screw 16, and the outer periphery of the bearing 15 is journaled so as to be rotatable relative to the shaft 14. The biasing cam follower 5c is provided on the guide shaft 8. The outer periphery of the bearing 12 of the first driving cam follower 5b abuts (engages) with the first cam groove 2a, and the first driving cam follower 5b is supported so as to be movable in the optical axis direction. Additionally, biasing cam follower 5c is threadedly engaged with guide shaft 8, and is held (disposed) on first movable barrel 5 so as to be movable in the optical axis direction via compression coil spring 10, with a phase difference of angle α with respect to first driving cam follower 5b about rotation axis CA of cam tube 2. The outer periphery of bearing 15 of biasing cam follower 5c abuts (engages) with first cam groove 2a.

[0016] FIG. 5 is a development view of the cam groove portion of the cam tube 2. FIG. 6 is an enlarged view of portion B in FIG. 5. The first cam groove 2a is composed of a cam surface 2d (first curved surface), a virtual cam surface 2e, and a cam surface 2f (second curved surface). That is, the first cam groove 2a is formed with a path (cam surface 2d) along which the first driving cam follower 5b should pass in accordance with optical requirements, and a path (cam surface 2f) of the same shape, which is shifted in phase by an angle α around the rotation axis CA of the cam tube 2. The first driving cam follower 5b is biased against the cam surface 2d of the first cam groove 2a by the biasing force P of the compression coil spring 10, and the biasing cam follower 5c is biased against the cam surface 2f opposite to the cam surface 2d, respectively. As a result, the first movable lens barrel 5 is restricted from falling by the three first guide grooves 1a, and moves in the optical axis direction along the orbit of the cam surface 2d by the first drive cam follower 5b abutting against the cam surface 2d by a distance corresponding to the amount of rotation of the cam tube 2.

[0017] Additionally, second movable barrel 6 is restricted from tilting by three second guide grooves 1b, and moves in the optical axis direction by second cam groove 2b a distance corresponding to the amount of rotation of cam tube 2. Similarly, third movable barrel 7 is restricted from tilting by three third guide grooves 1c, and moves in the optical axis direction by third cam groove 2c a distance corresponding to the amount of rotation of cam tube 2.

[0018] The phase difference between the first drive cam follower 5b and the biasing cam follower 5c is equal to the phase difference between the cam surface 2f and the virtual cam surface 2e, that is, angle α, so that they abut against the first cam groove 2a while lined up in a plane perpendicular to the optical axis OA.

[0019] 5, the first driving cam follower 5b at the second position C2 of the first moving barrel 5 is designated as 5b2, and the biasing cam follower 5c at the second position C2 of the first moving barrel 5 is designated as 5c2. Also, the first driving cam follower 5b at the third position C3 of the first moving barrel 5 is designated as 5b3, and the biasing cam follower 5c at the third position C3 of the first moving barrel 5 is designated as 5c3.

[0020] The first driving cam follower 5b and the biasing cam follower 5c have the same diameter. The biasing cam follower 5c and the cam surface 2f are formed by moving the first driving cam follower 5b and the virtual cam surface 2e by an angle α in a direction perpendicular to the optical axis OA.

[0021] Here, a straight line extending from the contact point between first drive cam follower 5b and cam surface 2d and perpendicular to cam surface 2d passes through the center of first drive cam follower 5b and also intersects perpendicular to virtual cam surface 2e at the contact point between first drive cam follower 5b and virtual cam surface 2e. In other words, cam surface 2d with which first drive cam follower 5b contacts and virtual cam surface 2e are parallel, and the angles formed by cam surface 2d and optical axis OA at the contact point are approximately equal. Furthermore, the positional shape and contact state of biasing cam follower 5c and cam surface 2f are the same as the relationship between first drive cam follower 5b and virtual cam surface 2e, as described above. Therefore, regardless of the position of the first movable lens barrel 5, the angle (contact angle) between the cam surface 2d and the optical axis OA at the contact point between the first driving cam follower 5b and the cam surface 2d is approximately equal to the angle between the cam surface 2f and the optical axis OA at the contact point between the biasing cam follower 5c and the cam surface 2f.

[0022] For example, consider the second position C2 of the first movable lens barrel 5. In Figure 6, the angle formed by the cam surface 2d at the abutment portion (contact point) between the first drive cam follower 5b2 and the cam surface 2d and the first axis D1 parallel to the optical axis OA is defined as β1. Also, the angle formed by the cam surface 2f at the abutment portion (contact point) between the biasing cam follower 5c2 and the cam surface 2f and the second axis D2 parallel to the optical axis OA is defined as β2. In this case, it is desirable that each angle in this embodiment satisfy the following conditional expression (1): 0°≦|β1-β2|≦10° (1) By satisfying conditional expression (1), it is possible to stably drive the first moving lens barrel 5. On the other hand, exceeding the upper limit of conditional expression (1) is not preferable because it causes unintended rotation of the cam tube 2. It is also preferable to satisfy the following conditional expressions (1a) and (1b) in this order, and it is more preferable to satisfy |β1−β2|=0°. 0°≦|β1-β2|≦5° (1a) 0°≦|β1-β2|≦3° (1b) In this embodiment, β1 and β2 are equal to each other, and |β1−β2|=0° is satisfied.

[0023] Next, consider the third position C3 of the first movable lens barrel 5. In Fig. 6, the angle formed by the cam surface 2d at the contact portion between the first drive cam follower 5b3 and the cam surface 2d and the first axis D3 parallel to the optical axis OA is denoted by γ1, and the angle formed by the cam surface 2f at the contact portion between the biasing cam follower 5c3 and the cam surface 2f and the second axis D4 parallel to the optical axis OA is denoted by γ2. In this case, it is desirable that each angle in this embodiment satisfy the following conditional expression (2). 0°≦|γ1-γ2|≦10° (2) When a plurality of first drive cam followers 5b and a plurality of biasing cam followers 5c are provided, it is desirable to make the contact angles of each set of first drive cam followers 5b and biasing cam followers 5c approximately equal. In other words, by satisfying conditional expression (2) in addition to conditional expression (1), the effect of stably driving the first moving lens barrel 5 becomes more pronounced. It is also preferable to satisfy the following conditional expressions (2a) and (2b) in this order, and it is more preferable to satisfy |γ1−γ2|=0°. 0°≦|γ1-γ2|≦5° (2a) 0°≦|γ1-γ2|≦3° (2b) In this embodiment, γ1 and γ2 are equal to each other, and |γ1-γ2|=0° is satisfied. That is, at all positions within the movement range of the first movable lens barrel 5, the contact angle between the first drive cam follower 5b and the cam surface 2d and the contact angle between the biasing cam follower 5c and the cam surface 2f are always equal.

[0024] Here, with regard to the ratio between the biasing force P in the optical axis direction by the compression coil spring 10 and the rotational force F required to rotate the cam tube 2, the lens device 100 according to this embodiment satisfies the following conditional expressions (3) and (4). |1 / tanβ1-1 / tanβ2| <F / P (3) |1 / tanγ1-1 / tanγ2| <F / P (4) Conditional expressions (3) and (4) indicate conditions for preventing the biasing force P of the compression coil spring 10 from unintentionally rotating the cam tube 2. If conditional expressions (3) and (4) are not satisfied, the biasing force P of the compression coil spring 10 may rotate the cam tube 2, potentially causing the optical element to deviate from its desired position. Note that the effects of the present invention can be obtained as long as at least one of conditional expressions (3) and (4) is satisfied.

[0025] At the second position C2 of the first movable lens barrel 5, the biasing force P of the compression coil spring 10 at the contact portion between the first drive cam follower 5b2 and the cam surface 2d acts secondarily in the circumferential direction of the cam tube 2 as a force F1 = P / tan β1 that tends to rotate the cam tube 2. At the same time, the biasing force P of the compression coil spring 10 at the contact portion between the biasing cam follower 5c2 and the cam surface 2f acts secondarily in the circumferential direction of the cam tube 2 as a force F2 = P / tan β2 that tends to rotate the cam tube 2 in the opposite direction. Therefore, the forces F1 and F2 cancel each other out, and the generation of the rotational force F that rotates the cam tube 2 is avoided.

[0026] Furthermore, at third position C3 of first movable barrel 5, biasing force P of compression coil spring 10 at the contact portion between first drive cam follower 5b2 and cam surface 2d acts secondarily in the circumferential direction of cam tube 2 as force F3=P / tan γ1 tending to rotate cam tube 2. At the same time, biasing force P of compression coil spring 10 at the contact portion between biasing cam follower 5c2 and cam surface 2f acts secondarily in the circumferential direction of cam tube 2 as force F4=P / tan γ2 tending to rotate cam tube 2 in the opposite direction. Therefore, forces F3 and F4 cancel each other out, preventing the generation of rotational force F that rotates cam tube 2. In other words, at all positions within the movement range of first movable barrel 5, the contact angle of first drive cam follower 5b and the contact angle of biasing cam follower 5c are substantially equal, preventing the generation of rotational force F that rotates cam tube 2.

[0027] With the above-described configuration, the biasing force P of the compression coil spring 10 biases the first drive cam follower 5b against the cam surface 2d and the biasing cam follower 5c against the cam surface 2f, so that the first movable lens barrel 5 can move without any play.

[0028] Even when the biasing force P of the compression coil spring 10 is applied, an unintended rotational force F is not applied to the cam tube 2, so the rotational operation of the cam tube 2 is stabilized, and it is possible to provide a lens device 100 with high positional accuracy and reduced power consumption. According to the present invention, by optimizing the shape of the cam surface 2f with which the biasing cam follower 5c abuts, it is possible to minimize the secondary effect of the biasing force P. This suppresses automatic rotation of the cam tube 2, making it possible to stably drive the moving barrel with high positional accuracy, and it is possible to provide a lens device 100 with reduced power consumption.

[0029] Furthermore, as described above, first drive cam follower 5b and biasing cam follower 5c are always aligned in a plane perpendicular to optical axis OA, so there is no expansion or contraction of compression coil spring 10, and biasing force P is maintained constant. Furthermore, since there is no expansion or contraction of compression coil spring 10, it is possible to make the biasing structure compact, which also contributes to reducing the weight and size of lens device 100.

[0030] A preferred embodiment of the present invention has been described above, but in this embodiment, the cam surface 2d with which the first driving cam follower 5b engages is uniquely determined by optical requirements, while the cam surface 2f with which the opposing biasing cam follower 5c engages has an optimal shape. In this embodiment, the cam surface 2f is formed so that the abutment angle of the first driving cam follower 5b and the abutment angle of the biasing cam follower 5c always match over the entire range of use of the cam tube 2, but this is not limitative. In other words, as long as the difference in abutment angle can be reduced to a range that does not interfere with the rotation or control of the cam tube 2, the abutment angles do not necessarily have to always match over the entire range of use.

[0031] In addition, in this embodiment, a cam tube 2 is configured that is parallel to the optical axis OA and is supported so as to be freely rotatable around an axis different from the optical axis OA, but it is also possible to replace elements in the driving mechanism of the optical system using multiple rows of cams formed on the cam tube 2 that rotates around the optical axis OA.

[0032] Furthermore, although this embodiment shows an example of application to a variable magnification lens group, it can be applied to a variety of cam mechanism parts that are required to move a moving group by a desired amount without backlash, such as a focusing lens group, etc. In other words, the present invention is not limited to this embodiment, and various modifications and changes are possible within the scope of its gist.

[0033] (Application example) 7 is a schematic diagram showing an example of the configuration of a camera device 200 (image capture device) that uses a lens device 100 to which the present invention is applied. The image capture device includes the lens device 100 and the camera device 200, which is made up of a camera body 200a having an image sensor 200b that captures an image of an object formed by the lens device 100. The image capture device may also be configured such that the lens device 100 is detachably attached to the camera body 200a of the camera device 200.

[0034] The disclosure of this embodiment includes the following configuration. (Configuration 1) a movable lens barrel that is movable in the optical axis direction; a moving member connected to the moving barrel via an elastic member so as to be movable along the optical axis; a cam member that rotates to move the movable lens barrel, a first cam follower is provided on the moving barrel, and a second cam follower is provided on the moving member; the cam member is provided with a cam groove in which the first and second cam followers engage, the cam groove includes a first curved surface with which the first cam follower abuts and a second curved surface with which the second cam follower abuts, Let β1 be the angle formed by the first curved surface and a first axis parallel to the optical axis at the point of contact between the first cam follower and the first curved surface, β2 be the angle formed by the second curved surface and a second axis parallel to the optical axis at the point of contact between the second cam follower and the second curved surface, P be the biasing force in the optical axis direction by the elastic member, and F be the rotational force required to rotate the cam member, |1 / tanβ1-1 / tanβ2| <F / P An optical device characterized by satisfying the following conditional expression. (Configuration 2) 0°≦|β1-β2|≦10° The optical device according to configuration 1, characterized in that the following condition is satisfied: (Configuration 3) 0°=|β1-β2| 3. The optical device according to configuration 1 or 2, wherein the following condition is satisfied: (Configuration 4) 4. The optical device according to any one of configurations 1 to 3, wherein the second cam follower is disposed with a phase difference from the first cam follower around the rotation axis of the cam member. (Configuration 5) 5. The optical device according to any one of configurations 1 to 4, wherein the cam member is supported so as to be rotatable about an axis that is parallel to the optical axis and different from the optical axis. (Configuration 6) 6. An imaging device comprising: the optical device according to any one of configurations 1 to 5; and an imaging element for capturing an image formed by the optical device. [Explanation of symbols]

[0035] 2: Cam tube (cam component) 2a: First cam groove (cam groove) 2d: Cam surface (first curved surface) 2f: Cam surface (second curved surface) 5: First moving tube (moving tube) 5b: First drive cam follower (first cam follower) 5c: Biasing cam follower (second cam follower) 8: Guide shaft (moving part) 10: Compression coil spring (elastic member) 100: Lens device (optical device) CA: Rotation axis D1: 1st axis D2: 2nd axis OA: optical axis β: Angle

Claims

1. a movable lens barrel that is movable in the optical axis direction; a moving member connected to the moving barrel via an elastic member so as to be movable along the optical axis; a cam member that rotates to move the movable lens barrel, a first cam follower is provided on the moving barrel, and a second cam follower is provided on the moving member; the cam member is provided with a cam groove in which the first and second cam followers engage, the cam groove includes a first curved surface with which the first cam follower abuts and a second curved surface with which the second cam follower abuts, Let β1 be the angle formed by the first curved surface at the contact point between the first cam follower and the first curved surface and a first axis parallel to the optical axis, β2 be the angle formed by the second curved surface at the contact point between the second cam follower and the second curved surface and a second axis parallel to the optical axis, P be the biasing force in the optical axis direction by the elastic member, and F be the rotational force required to rotate the cam member, |1 / tanβ1-1 / tanβ2|<F / P An optical device characterized by satisfying the following conditional expression.

2. ０°≦｜β１－β２｜≦１０° 2. The optical device according to claim 1, wherein the following condition is satisfied:

3. ０°＝｜β１－β２｜ 2. The optical device according to claim 1, wherein the following condition is satisfied:

4. 2. The optical device according to claim 1, wherein the second cam follower is disposed with a phase difference from the first cam follower about the rotation axis of the cam member.

5. 2. The optical device according to claim 1, wherein the cam member is supported so as to be rotatable about an axis that is parallel to the optical axis and different from the optical axis.

6. 6. An imaging device comprising: the optical device according to claim 1; and an imaging element for capturing an image formed by the optical device.

Images