Lens drive

Abstract

To provide a compact lens drive capable of suppressing deterioration of an optical performance and an animation performance.SOLUTION: A lens drive has at least one lens, a lens barrel for holding the lens, and N (N is an integer of 2 or larger) linear motors each composed of a first coil and a second coil for generating drive force in a direction parallel with a light axis of the lens in the lens barrel and a magnet assembly in a Halbach array, at least one of the first coil and the second coil has a bend, and the linear motor is disposed at an interval of 360 / N degrees along a circumferential direction with the light axis of the lens as a center.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a lens driving device that drives a lens with a linear motor.

Background Art

[0002] Patent Document 1 discloses a linear motor that is composed of a plurality of magnets and a plurality of coils and drives a lens barrel that holds an optical system for changing the focal length and performing focus adjustment of an interchangeable lens for a camera.

[0003] Further, Patent Document 2 discloses a linear motor that drives a magnet assembly of a Halbach array disposed on both sides of a plurality of coils.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In order to drive a lens barrel with a large mass using the linear motor of Patent Document 1, it is necessary to increase the size of the magnet and the yoke, and there is a risk that the interchangeable lens will become larger.

[0006] In addition, when driving a lens barrel using the linear motor of Patent Document 2, a method can be considered in which the lens barrel holds a coil and magnet assemblies are arranged on both sides. However, in this case, the interchangeable lens becomes large in the radial direction. Here, as shown in FIG. 14(a), a case will be described in which two-phase coils 1010 and 1011 are fixed to a lens barrel 1003 and a magnet assembly 1012 having a Halbach array is arranged on one side. In this case, as shown in FIG. 14(b), a Lorentz force is generated in the direction orthogonal to the optical axis O (arrow direction) by the magnetic flux in the driving direction created by the sub-magnet 1012s of the magnet assembly 1012 and the current flowing through the coils 1010 and 1011 (in the paper surface direction). As a result, a moment acts on the lens barrel 1003, and there is a risk that the optical performance deteriorates due to the inclination of the lens barrel 1003. Further, when using such a linear motor, since the current amplitude flowing through the coils 1010 and 1011 periodically increases and decreases, the magnitude of the Lorentz force also changes periodically. As a result, the lens barrel 1003 vibrates and noise is generated, and there is a risk that the video performance deteriorates.

[0007] An object of the present invention is to provide a lens driving device that is small-sized and can suppress deterioration of optical performance and video performance.

Means for Solving the Problems

[0008] A lens driving device according to one aspect of the present invention includes at least one lens, a lens barrel that holds the lens, and N (N is an integer of 2 or more) linear motors each including a first coil, a second coil, and a magnet assembly that form a Halbach array and generate a driving force in a direction parallel to the optical axis of the lens in the lens barrel. At least one of the first coil and the second coil has a bent portion, and the linear motors are arranged at intervals of 360 / N degrees along the circumferential direction centered on the optical axis of the lens.

Effects of the Invention

[0009] According to the present invention, it is possible to provide a lens driving device that is small-sized and can suppress deterioration of optical performance and video performance.

Brief Description of the Drawings

[0010]

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Figure 14

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each figure, the same members are denoted by the same reference numerals, and overlapping descriptions are omitted. [Schematic Configuration of Interchangeable Lens] FIG. 1 is a schematic diagram of an imaging apparatus including an interchangeable lens 100 according to an embodiment of the present invention. The interchangeable lens 100 is mechanically and electrically connected to a camera body 200 by a mount (not shown). The interchangeable lens 100 includes a focus unit 1 for focus adjustment, a drive circuit 300 for driving a linear motor 500 described later, and a lens control unit 400 for controlling the driving of the linear motor 500 and other components within the interchangeable lens 100. Note that the interchangeable lens 100 also includes a zoom optical system, a diaphragm device for adjusting the light amount, an operation member, and the like, which are omitted for simplicity of explanation. In the present embodiment, the focus unit 1 for focus adjustment will be described as an example of a lens driving device, but a unit for driving a lens that changes the focal length may also be used.

Example

[0012] [Configuration of Focus Unit] FIG. 2 is an exploded perspective view of the focus unit 1. In the present example, as shown in FIG. 2, the optical axis O is defined as the X axis, the axis orthogonal to the X axis is defined as the Y axis, and the Z axis is defined. FIG. 3 is a view of a cross section of the focus unit 1 cut along the X-Z plane as seen from the negative Y-axis direction. FIG. 4 is a view of a cross section of the focus unit 1 cut along the X-Y plane as seen from the positive Z-axis direction.

[0013] The focus lens 2 is made of a single piece of glass and is an optical system for focus adjustment. Note that the focus lens 2 may be composed of a plurality of pieces of glass. Also, the focus lens 2 may be composed of a resin plastic lens.

[0014] The lens barrel 3 is formed of a resin material or a metal material. The focus lens 2 is adhesively fixed to the lens barrel 3. The lens barrel 3 is formed with round hole portions 3a and 3b through which the main guide shaft 8 is inserted, and a long hole portion 3c through which the sub-guide shaft 9 is inserted.

[0015] The position detection scale 4 is a strip-shaped reflective scale with a reflection pattern formed on its surface, and together with the sensor head 5, it constitutes an optical position detection encoder. The position detection scale 4 is adhesively fixed to the lens barrel 3.

[0016] The sensor head 5 constitutes an optical position detection encoder together with the position detection scale 4, and detects the position of the lens barrel 3 in the X-axis direction (the direction parallel to the optical axis O). The sensor head 5 is fixed to the fixed cylinder 6 via a sensor holder (not shown). The sensor head 5 is electrically connected to the lens control unit 400 via a flexible printed circuit board (not shown). The lens control unit 400 controls the linear motor 500 using the position information detected by the sensor head 5. Note that the position of the lens barrel 3 may be detected using other means such as a magnetic position detection encoder composed of a magnetic sensor (MR sensor) and a magnetic scale.

[0017] The fixed cylinder 6 is formed of a resin material or a metal material and has a substantially cylindrical shape. The fixed cylinder 6 is fixed to a fixing portion (not shown) of the interchangeable lens 100. The fixed cylinder 6 includes bearing portions 6m and 6s for press-fitting the main guide shaft 8 and the sub-guide shaft 9. Note that the bearing portions 6m and 6s may be configured separately from the fixed cylinder 6.

[0018] The cover member 7 is formed of a resin material or a metal material and has a substantially annular shape. The cover member 7 is screwed and fixed to the fixed cylinder 6 by screws (not shown). The cover member 7 has bearing portions 7m and 7s for press-fitting the main guide shaft 8 and the sub-guide shaft 9. Note that the bearing portions 7m and 7s may be configured separately from the cover member 7.

[0019] The main guide shaft 8 and the sub-guide shaft 9 are formed of a metal material and have a cylindrical shape. The main guide shaft 8 is press-fitted and fixed to the bearing portion 6m of the fixing cylinder 6 and the bearing portion 7m of the cover member 7 so as to be parallel to the optical axis O. The sub-guide shaft 9 is press-fitted and fixed to the bearing portion 6s of the fixing cylinder 6 and the bearing portion 7s of the cover member 7 so as to be parallel to the optical axis O. The main guide shaft 8 is inserted through the round holes 3a and 3b of the lens barrel 3. The sub-guide shaft 9 is inserted through the long hole 3c of the lens barrel 3. With the above configuration, the lens barrel 3 is configured to linearly move along the optical axis O.

[0020] The linear motor 500 is composed of a phase A coil 10, a phase B coil 11, and a magnet assembly 12. The linear motor 500 generates a driving force for linearly moving the lens barrel 3 along the optical axis O by passing an electric current through the phase A coil 10 and the phase B coil 11. Two linear motors 500 are arranged at positions facing each other across the optical axis O by 180 degrees. Note that the number of linear motors is not limited to two. When arranging N (N is an integer of 2 or more) linear motors 500, they may be evenly arranged at intervals of 360 / N degrees along the circumferential direction centered on the optical axis O. However, in order to achieve stable driving and a simple configuration, the number of linear motors is preferably two or three.

[0021] The phase A coil 10 and the phase B coil 11 are formed by further bending a substantially rectangular hollow coil formed by winding a copper wire with an insulated surface a predetermined number of times. The phase A coil 10 and the phase B coil 11 are adhesively fixed to the lens barrel 3 and are electrically connected to the drive circuit 300 via a flexible printed circuit board (not shown). The phase A coil 10 and the phase B coil 11 are arranged at opposing positions while ensuring an appropriate air gap with respect to the magnet assembly 12. The phase A coil 10 and the phase B coil 11 have a plane parallel to the optical axis O, and the plane parallel to the optical axis O is arranged closer to the optical axis O than the plane on the side where the magnetic flux of the magnet assembly 12 is concentrated.

[0022] The magnet assembly 12 is an assembly of a plurality of magnets having a Halbach array structure. The magnet assembly 12 is adhesively fixed to the magnet holding plate 13 on the side opposite to the side where the magnetic field is concentrated by the Halbach array structure (the opposite side).

[0023] The magnet holding plate 13 is formed of a resin material or a metal material and has a substantially U-shape. The magnet holding plate 13 is screwed and fixed to the fixing cylinder 6 by screws (not shown). Note that the shape of the magnet holding plate 13 may also be a simple flat plate, a box shape with one side of a rectangular parallelepiped open, etc. Also, by forming the magnet holding plate 13 of a magnetic material, the driving force of the linear motor 500 can be improved. Further, the magnet assembly 12 may be directly adhesively fixed to the fixing cylinder 6 without providing the magnet holding plate 13. [Shape and Arrangement of Coils] The shape of the A-phase coil 10 and the arrangement of the A-phase coil 10 and the B-phase coil 11 will be described. FIG. 5(a) is a perspective view of the A-phase coil 10. FIG. 5(b) is a front view of the A-phase coil 10 viewed from the X-axis direction. FIG. 6 is a perspective view of the lens barrel 3 and the peripheral components held by the lens barrel 3.

[0024] The A-phase coil 10 includes driving force generating sides 10a, 10b that generate a driving force parallel to the Z-axis. The A-phase coil 10 also includes connecting sides 10c, 10d that are parallel to the X-axis and hardly generate a driving force. The A-phase coil 10 is a coil having a bent portion. Specifically, as shown in FIG. 5(b), the angle θ formed by the plane in contact with the driving force generating sides 10a, 10b and the plane in contact with the connecting side 10c or 10d is greater than 0 degrees and less than 90 degrees. In other words, the plane in contact with the driving force generating sides 10a, 10b and the plane in contact with the connecting side 10c or 10d intersect. That is, the A-phase coil 10 includes a plane parallel to the optical axis O and a plane inclined with respect to the parallel plane. Since the B-phase coil 11 has the same shape as the A-phase coil 10, the description thereof is omitted.

[0025] The driving force generating side 10b of the phase A coil 10 is inserted into the hollow portion of the phase B coil 11. The driving force generating side 11b of the phase B coil 11 is inserted into the hollow portion of the phase A coil 10. In this way, the driving force generating sides 10a, 10b of the phase A coil 10 and the driving force generating sides 11a, 11b of the phase B coil 11 are alternately arranged along the X-axis direction. By the above arrangement, the switching lens 100 can be miniaturized in the X-axis direction. Also, by bending the phase A coil 10 and the phase B coil 11, the connecting side 10c of the phase A coil 10 and the connecting side 11d of the phase B coil, and the connecting side 10d of the phase A coil 10 and the connecting side 11c of the phase B coil can be arranged so that they do not interfere with each other. [Configuration of Magnet Assembly] FIG. 7 is a side view of the magnet assembly 12 and the magnet holding plate 13. "N" and "S" represent the poles of the magnet.

[0026] The magnet assembly 12 is formed by adhesively bonding a plurality of main magnets 12m and sub-magnets 12s. The main magnets 12m and the sub-magnets 12s are alternately arranged along the driving direction. The main magnets 12m and the sub-magnets 12s are the same magnet, and are arranged with their magnetization directions changed to form a Halbach array structure. Note that it is not essential for the main magnets 12m and the sub-magnets 12s to have the same shape. Also, the number of the main magnets 12m and the sub-magnets 12s is not limited as long as they form a Halbach array structure.

[0027] The main magnets 12m and the sub-magnets 12s are formed by sintering from a magnetic material containing rare earth elements and have a substantially rectangular parallelepiped shape. [Driving Method and Operation of Linear Motor] The basic driving method and operation of the linear motor 500 will be described. FIGS. 8(a) to 8(c) are X-Y cross-sectional views of the linear motor 500 when the time T is t0, t1, and t2, respectively. FIG. 9 is a diagram showing the time change of the current flowing through the phase A coil 10 and the phase B coil 11.

[0028] When the time T is t0, the A-phase coil 10 is in the phase of the auxiliary magnet 12s, and the B-phase coil 11 is in the phase of the main magnet 12m. At this time, the current in the A-phase coil 10 is 0, and the current in the B-phase coil 11 is set to a predetermined value Q. As a result, a driving force in the negative X-axis direction (arrow in the figure) is generated in the B-phase coil 11, and the lens barrel 3 moves in the negative X-axis direction.

[0029] When the time T is t1, the A-phase coil 10 and the B-phase coil 11 are in the intermediate phase between the main magnet 12m and the auxiliary magnet 12s. At this time, the current in the A-phase coil 10 is set to about 0.7Q, and the current in the B-phase coil 11 is set to about 0.7Q. As a result, a driving force in the negative X-axis direction is generated in the A-phase coil 10 and the B-phase coil 11, and the lens barrel 3 moves in the negative X-axis direction.

[0030] When the time T is t2, the A-phase coil 10 is in the phase of the main magnet 12m, and the B-phase coil 11 is in the phase of the auxiliary magnet 12s. At this time, the current in the A-phase coil 10 is Q, and the current in the B-phase coil 11 is set to 0. As a result, a driving force in the negative X-axis direction is generated in the A-phase coil 10, and the lens barrel 3 moves in the negative X-axis direction.

[0031] Regarding the direction of the current flowing through each coil, it may be set so that each coil receives a Lorentz force from the magnet in the negative X-axis direction. When driving in the positive X-axis direction, it may be set so that each coil receives a Lorentz force from the magnet in the positive X-axis direction.

[0032] By flowing currents through the A-phase coil 10 and the B-phase coil 11 as described above, the driving force for moving the lens barrel 3 can be made constant.

[0033] In the control of the actual interchangeable lens 100, more complex position feedback control and speed feedback control are performed using the above basic driving method, but since it is different from the essence of the present invention, the description is omitted. [Operation] Referring to FIG. 10, the operation of the present invention will be described. FIG. 10 is an X-Y cross-sectional view showing the main components of the focus unit 1 when the time T in FIG. 9 is t1.

[0034] In the linear motor 500, a Lorentz force is generated in the direction orthogonal to the optical axis O (arrow direction) by the magnetic flux in the driving direction created by the sub-magnet 12s and the current flowing in the A-phase coil 10 and the B-phase coil 11 (in the paper surface direction).

[0035] In this embodiment, two linear motors 500 are arranged at positions facing each other across the optical axis O at 180 degrees. Therefore, the Lorentz force in the direction orthogonal to the optical axis O generated by the magnetic flux created by the sub-magnet 12s is generated symmetrically with respect to the optical axis O in the linear motor 500 above the paper surface and the linear motor 500 below the paper surface. As a result, the Lorentz forces in the direction orthogonal to the optical axis O cancel each other out.

[0036] Therefore, since no moment acts on the lens barrel 3, it is possible to suppress the tilting of the lens barrel 3. As a result, it is possible to suppress the deterioration of the optical performance of the interchangeable lens 100. In addition, since the periodically generated Lorentz forces can also cancel each other out, it is possible to suppress the vibration noise of the lens barrel 3. As a result, it is possible to suppress the deterioration of the video performance.

Embodiment

[0037] In this embodiment, the A-phase coil 110 and the B-phase coil 11 have different shapes from each other. In this embodiment, the shape of the A-phase coil 110 is different from that in the first embodiment. Specifically, the B-phase coil 11 has a shape (second shape) with a bent portion as in the first embodiment, and the A-phase coil 110 has a shape (first shape) without a bent portion. Since the other components and arrangements are the same as those in the first embodiment, the description thereof is omitted. [Configuration of Focus Unit] FIG. 11 is a perspective view showing only some of the components of the focus unit 1 of this embodiment. FIG. 12 is a front view of the focus unit 1 of this embodiment as viewed from the negative X-axis direction. FIG. 13 is a perspective view of the A-phase coil 110 of this embodiment.

[0038] The A-phase coil 110 is a flat coil without a bent portion, unlike the A-phase coil 10 of the first embodiment. That is, in the A-phase coil 110, the angle θ formed between the plane in contact with the driving force generating sides 110a and 110b and the plane in contact with the connecting side 110c or 110d is 0 degrees. In other words, the plane in contact with the driving force generating sides 110a and 110b does not intersect the plane in contact with the connecting side 110c or 110d. As a result, the A-phase coil 110 is arranged so as not to intersect the plane including the surface 12a on the side where the magnetic flux of the magnet assembly 12 is concentrated (on the side of the optical axis O from the surface 12a on the side where the magnetic flux of the magnet assembly 12 is concentrated). Since the B-phase coil 11 is a coil having a bent portion, the A-phase coil 110 and the B-phase coil 11 can be arranged without interference. The B-phase coil 11 is arranged so as not to intersect the plane including the surface 12a on the side where the magnetic flux of the magnet assembly 12 is concentrated (on the side of the optical axis O from the surface 12a on the side where the magnetic flux of the magnet assembly 12 is concentrated), similarly to the A-phase coil 110. [Operation] The reason for forming the A-phase coil 110 into the above shape will be described. A magnetic field is generated in the side surfaces 12r and 12l (the surfaces orthogonal to the Z-axis) of the magnet assembly 12 forming the Halbach array. Therefore, when a current flows through the connecting sides 10c and 10d of the A-phase coil 10 as in the A-phase coil 10 of the first embodiment, a Lorentz force is generated by the magnetic field of the side surfaces 12r and 12l. On the other hand, since the B-phase coil 11 is far from the side surfaces 12r and 12l, almost no Lorentz force is generated by the magnetic field of the side surfaces 12r and 12l of the magnet assembly 12. As a result, a difference occurs between the driving force generated by the A-phase coil 10 and the driving force generated by the B-phase coil 11.

[0039] In this embodiment, by arranging the A-phase coil 110 away from the side surfaces 12r and 12l, the A-phase coil 110 is hardly affected by the magnetic field of the side surfaces 12r and 12l. That is, the Lorentz force generated by the magnetic field of the side surfaces 12r and 12l in the A-phase coil 110 can be reduced. Therefore, the driving forces of the A-phase coil 110 and the B-phase coil 11 can be made substantially the same magnitude, and the exchange lens 100 can be stably controlled.

[0040] The disclosure of this embodiment includes the following configurations. (Configuration 1) At least one lens, a lens barrel that holds the lens, and N (N is an integer of 2 or more) linear motors each including a first coil, a second coil, and a magnet assembly forming a Halbach array that generates a driving force in a direction parallel to the optical axis of the lens in the lens barrel, wherein at least one of the first coil and the second coil has a bent portion, and the linear motors are arranged at intervals of 360 / N degrees along the circumferential direction centered on the optical axis of the lens. A lens driving device characterized by this. (Configuration 2) The lens driving device according to Configuration 1, wherein the first coil and the second coil have different shapes from each other. (Configuration 3) The first coil has a first shape without a bent portion, and the second coil has a second shape with a bent portion. The lens driving device according to Configuration 1 or 2, characterized by this. (Configuration 4) The lens driving device according to Configuration 3, wherein the first coil and the second coil are arranged on the side of the optical axis rather than on the side of the surface where the magnetic flux of the magnet assembly is concentrated. (Configuration 5) The lens driving device according to Configuration 1 or 2, wherein at least one of the first coil and the second coil includes a surface parallel to the optical axis and a surface inclined with respect to the parallel surface. (Configuration 6) The first coil and the second coil include a surface parallel to the optical axis, and the parallel surface is located on the side of the optical axis rather than on the side of the surface where the magnetic flux of the magnet assembly is concentrated. The lens driving device according to any one of Configurations 1 to 5, characterized by this. (Configuration 7) The lens driving device according to any one of Configurations 1 to 6, characterized in that the number of the linear motors is two. (Configuration 8) The lens driving device according to any one of Configurations 1 to 6, characterized in that the number of the linear motors is three.

[0041] As described above, the preferred embodiments of the present invention have been described. However, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist thereof.

Description of Reference Numerals

[0042] 1 Focus unit (lens driving device) 2 Focus lens (lens) 3 Lens barrel 10, 110 A-phase coil (first coil) 11 B-phase coil (second coil) 12 Magnet assembly

Claims

1. At least one lens; a lens barrel for holding the lens; Each of the linear motors includes N linear motors (N is an integer of 2 or more) each including a first coil and a second coil that generate a driving force in the lens barrel in a direction parallel to the optical axis of the lens, and a magnet assembly that forms a Halbach array; At least one of the first coil and the second coil includes a bent portion, The lens driving device, wherein the linear motors are arranged at intervals of 360 / N degrees along a circumferential direction centered on the optical axis of the lens.

2. The lens driving device according to claim 1 , wherein the first coil and the second coil have different shapes.

3. the first coil has a first shape without a bend; 3. The lens driving device according to claim 1, wherein the second coil has a second shape including a bent portion.

4. 4. The lens driving device according to claim 3, wherein the first coil and the second coil are disposed closer to the optical axis than a surface of the magnet assembly on which magnetic flux is concentrated.

5. 3. The lens driving device according to claim 1, wherein at least one of the first coil and the second coil has a surface parallel to the optical axis and a surface inclined with respect to the parallel surface.

6. the first coil and the second coil have a surface parallel to the optical axis; 3. The lens driving device according to claim 1, wherein the parallel surface is located closer to the optical axis than a surface of the magnet assembly on which magnetic flux is concentrated.

7. 3. The lens driving device according to claim 1, wherein the number of the linear motors is two.

8. 3. The lens driving device according to claim 1, wherein the number of the linear motors is three.

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