Optical device and imaging device having the same

Abstract

To provide an optical device having a small linear motor capable of efficiently generating magnetic flux.SOLUTION: An optical device of the present invention includes: an optical element; and a linear motor for moving the optical element in a predetermined direction, in which a stator of the linear motor includes first and second magnet assemblies, each having a plurality of magnets arranged in a Halbach array along the predetermined direction, and a mover of the linear motor includes a plurality of coils coupled to the optical element so that each winding axis is parallel to the predetermined direction, in which each coil has first and second portions respectively facing a first surface of the first magnet assembly, which has a relatively strong magnetic field strength, and a second surface of the second magnet assembly, which has a relatively strong magnetic field strength.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an optical device including an optical element and a linear motor for moving the optical element. [Background technology]

[0002] 2. Description of the Related Art Conventionally, a linear motor including a mover formed of a plurality of coils and a stator formed of a plurality of magnets has been used as a driving unit for moving a predetermined optical element in a predetermined direction in an optical device. In such a linear motor, it is required that a stator formed of a plurality of magnets efficiently generate magnetic flux for driving a mover.

[0003] Patent Document 1 discloses a linear motor that includes a plurality of magnets in a Halbach array, each having a cylindrical shape to efficiently generate magnetic flux, and a plurality of coils that are arranged so that the winding axis of each coil is parallel to the axis of the cylinder. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-115239 Summary of the Invention [Problem to be solved by the invention]

[0005] In the linear motor disclosed in Patent Document 1, a cavity is formed near the central axis to magnetize each magnet, so when the magnetic force is increased, the radial size increases, resulting in an increase in size. SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an optical device equipped with a small linear motor that can efficiently generate magnetic flux. [Means for solving the problem]

[0006] The optical device according to the present invention comprises an optical element and a linear motor that moves the optical element in a predetermined direction, wherein the stator of the linear motor includes first and second magnet assemblies, each having a plurality of magnets in a Halbach array aligned along the predetermined direction, and the mover of the linear motor includes a plurality of coils that are coupled to the optical element so that their respective winding axes are parallel to the predetermined direction, and the first and second portions of each coil face a first surface of the first magnet assembly that has a relatively strong magnetic field strength and a second surface of the second magnet assembly that has a relatively strong magnetic field strength, respectively. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an optical device equipped with a small linear motor that can efficiently generate magnetic flux. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view of an imaging apparatus including an optical device according to a first embodiment. [Figure 2] FIG. 2 is an exploded perspective view of a focus unit included in the optical device according to the first embodiment. [Figure 3] 3A and 3B are an XZ cross-sectional view and an XY cross-sectional view of a focus unit included in the optical device according to the first embodiment. [Figure 4] 2 is an XY cross-sectional view of a linear motor included in the optical device according to the first embodiment. FIG. [Figure 5] 2A and 2B are a partial front view and a partially exploded perspective view of a linear motor included in the optical device according to the first embodiment; [Figure 6] 2 is an XY cross-sectional view of a linear motor included in the optical device according to the first embodiment. FIG. [Figure 7] 5A and 5B are diagrams showing changes over time in the amplitude of a current and the amplitude of a driving force in a linear motor included in the optical device according to the first embodiment. [Figure 8] FIG. 2 is a partial XY cross-sectional view of a focus unit included in the optical device according to the first embodiment. [Figure 9]FIG. 10 is a partial front view of a focus unit included in an optical device according to a second embodiment. [Figure 10] 10A and 10B are an exploded perspective view and a partial front view of a focus unit included in an optical device according to a third embodiment. [Figure 11] 10A and 10B are an XZ cross-sectional view and a partial front view of a linear motor included in an optical device according to a third embodiment. [Figure 12] FIG. 11 is a partial XZ cross-sectional view of a focus unit included in an optical device according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] The optical device according to the present embodiment will be described in detail below with reference to the accompanying drawings. Note that the drawings may be drawn to a scale different from the actual scale in order to facilitate understanding of the present embodiment. In the following description, the direction parallel to the optical axis O of the focus unit 1 is defined as the X direction, and two directions perpendicular to each other in a plane perpendicular to the optical axis are defined as the Y direction and the Z direction.

[0010] [First embodiment] Conventionally, in optical devices, a linear motor equipped with a mover formed from multiple coils and a stator formed from multiple magnets has been used as a drive unit that moves a specified optical element in a direction parallel to the optical axis in order to change the focal length. In such a linear motor, it is required to efficiently generate magnetic flux in a stator formed from a plurality of magnets.

[0011] Therefore, a linear motor has been proposed that includes a plurality of magnets in a Halbach array, each having a cylindrical shape, to efficiently generate magnetic flux, and a plurality of coils that are arranged so that the winding axis of each coil is parallel to the axis of the cylinder. However, in such linear motors, a cavity is formed near the central axis to magnetize each magnet, so when the magnetic force is increased, the radial size increases, resulting in a large size.

[0012] Furthermore, it is not easy to magnetize each of the multiple cylindrical magnets in the Halbach array in such a linear motor. Therefore, an object of this embodiment is to provide an optical device including a small linear motor that can be easily formed so as to generate magnetic flux efficiently.

[0013] FIG. 1 shows a schematic cross-sectional view of an imaging device 600 equipped with an interchangeable lens 100 as an optical device according to the first embodiment. The imaging device 600 includes an interchangeable lens 100 and a camera body 200 .

[0014] The interchangeable lens 100 is provided with a focus unit 1, a drive circuit 300, and a lens control unit 400. The interchangeable lens 100 is mechanically and electrically connected to the camera body 200 by a mount (not shown). The camera body 200 is also provided with an imaging element (photoelectric conversion element) 250 that captures (images) the subject image formed by the interchangeable lens 100 and includes, for example, a CCD sensor or a CMOS sensor.

[0015] The focus unit 1 is configured to adjust (change) the focus of the interchangeable lens 100 by moving in the X direction parallel to the optical axis O of the interchangeable lens 100. The drive circuit 300 is configured to drive a linear motor 500, which will be described later.

[0016] The lens control unit 400 is configured to control the driving of the linear motor 500 and each of the components provided in the interchangeable lens 100 . In addition to the above, the interchangeable lens 100 is provided with a zoom optical system, an aperture device for adjusting the amount of light, operation members, etc. (not shown), and a description of these will be omitted.

[0017] FIG. 2 shows a schematic exploded perspective view of the focus unit 1. As shown in FIG. 3(a) and 3(b) show a schematic XZ cross-sectional view and a schematic XY cross-sectional view of the focus unit 1, respectively.

[0018] The focus unit 1 is a unit for adjusting the focal length of the interchangeable lens 100, and includes a single focus lens 2 (optical element) made of glass. The focus unit 1 also includes a lens holder 3 , a position detection scale 4 , a position detection sensor 5 , a fixed barrel 6 , a cover 7 , a main guide bar 8 , a sub guide bar 9 , and a linear motor 500 .

[0019] The number of focus lenses 2 provided in the focus unit 1 may be one or more. Furthermore, the focus lens 2 is not limited to a glass lens, but may be a plastic lens made of a resin material.

[0020] The lens holder 3 is made of a resin material or a metal material, and the focus lens 2 is fixed to the lens holder 3 by adhesive. The lens holder 3 is also formed with round holes 3a and 3b through which the main guide bar 8 is inserted, and an elongated hole 3c through which the sub guide bar 9 is inserted. The lens holder 3 is configured to hold a position detection scale 4, an A-phase coil 10, and a B-phase coil 11.

[0021] The position detection scale 4 is a rectangular reflective scale with a reflective pattern formed on its surface, and is fixed to the lens holder 3 with adhesive. The position detection sensor 5 is configured to detect the position of the lens holder 3 in the X direction, and is fixed to the fixed barrel 6 via a sensor holder (not shown). The position detection scale 4 and the position detection sensor 5 form an optical position detection encoder.

[0022] The position detection sensor 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 operation of a linear motor 500 (to be described later) based on the position information of the lens holder 3 detected by the position detection sensor 5.

[0023] As the position detecting encoder, instead of the position detecting scale 4 and the position detecting sensor 5, other known position detecting encoders such as a magnetic position detecting encoder formed of a magnetic sensor (MR sensor) and a magnetic scale may be used. The position detection encoder may be either a relative position encoder that detects a relative position or an absolute position encoder that detects an absolute position.

[0024] The fixed barrel 6 is made of a resin material or a metal material and has a substantially cylindrical shape, and is fixed to a fixed portion (not shown) of the interchangeable lens 100. Furthermore, the fixed cylinder 6 is formed with bearing portions 6m and 6s into which the main guide bar 8 and the sub guide bar 9 are press-fitted, respectively. The bearings 6m and 6s may be provided separately from the fixed cylinder 6.

[0025] The cover 7 is made of a resin material or a metal material, has a substantially annular shape, and is fixed to the fixed barrel 6 by screws (not shown). The cover 7 is also formed with bearing portions 7m and 7s into which the main guide bar 8 and the sub guide bar 9 are press-fitted, respectively. The bearings 7m and 7s may be provided separately from the cover 7.

[0026] The main guide bar 8 and the sub guide bar 9 are each made of a metal material and have a cylindrical shape. The main guide bar 8 is press-fitted and fixed into a bearing portion 6m formed on the fixed cylinder 6 and a bearing portion 7m formed on the cover 7 so as to be parallel to the optical axis O. The main guide bar 8 is inserted into round holes 3 a and 3 b formed in the lens holder 3 .

[0027] The sub guide bar 9 is press-fitted and fixed into a bearing portion 6s formed on the fixed cylinder 6 and a bearing portion 7s formed on the cover 7 so as to be parallel to the optical axis O. The sub guide bar 9 is inserted into an elongated hole 3 c formed in the lens holder 3 . The lens holder 3 is guided in a straight line along the optical axis O by the above-described configuration.

[0028] The linear motor 500 has an A-phase coil 10 and a B-phase coil 11 (first and second coils) that form a mover, two magnet assemblies 12 (first and second magnet assemblies) that form a stator, and a magnet holder 13. The linear motor 500 generates an electromagnetic force for moving the lens holder 3 in a predetermined direction, specifically along the optical axis O, by passing a current through each of the A-phase coil 10 and the B-phase coil 11, as will be described in detail later.

[0029] The number of linear motors 500 provided in the focus unit 1 may be one or more. Furthermore, the number of coils and magnet assemblies provided in the linear motor 500 is not limited to two as described above, and may be any number.

[0030] The A-phase coil 10 and the B-phase coil 11 are each an air-core coil formed by winding a copper wire with an insulated surface a predetermined number of times around a predetermined axis (winding axis), and each having a rectangular cylindrical shape in a plane perpendicular to the winding axis. The A-phase coil 10 and the B-phase coil 11 are adhesively fixed to the lens holder 3 so that the winding axes thereof are parallel to the optical axis O. Furthermore, the A-phase coil 10 and the B-phase coil 11 are each electrically connected to a drive circuit 300 via a flexible printed circuit board (not shown).

[0031] Furthermore, the A-phase coil 10 and the B-phase coil 11 are arranged with an appropriate air gap secured between each of the two magnet assemblies 12 . The A-phase coil 10 and the B-phase coil 11 are arranged to surround the two magnet assemblies 12 .

[0032] FIG. 4 shows a schematic XY cross-sectional view of the linear motor 500. In FIG. 4, N and S respectively indicate the north and south poles of the magnets provided in the two magnet assemblies 12. 5(a) and 5(b) are a partial schematic front view of the focus unit 1 and a partial schematic exploded perspective view of the linear motor 500, respectively.

[0033] The magnet assembly 12 is formed by adhesively bonding together a plurality of main magnets 12m and a plurality of sub-magnets 12s in a Halbach array along the X direction parallel to the optical axis O. That is, the main magnets 12m and the sub-magnets 12s are arranged alternately with their magnetization directions changed in the X direction.

[0034] In other words, the magnets provided in the magnet assembly 12 are arranged in the X direction with their magnetization directions rotated by 90° around the Z axis. Each of the two magnet assemblies 12 forms a single magnetic circuit.

[0035] In the magnet assembly 12, the multiple main magnets 12m and multiple sub-magnets 12s are arranged in a Halbach array as described above, so that a surface (side) with a relatively strong magnetic field strength and a surface (side) with a relatively weak magnetic field strength are formed on opposite sides of each other. The surfaces of the two magnet assemblies 12 that have relatively weak magnetic field strength are adhesively fixed to the magnet holders 13, respectively.

[0036] On the other hand, the normals of the surfaces of the two magnet assemblies 12 with relatively strong magnetic field strengths face outward in the Y direction of the linear motor 500, and the two magnet assemblies 12 pass through the A-phase coil 10 and the B-phase coil 11. In other words, the surfaces (first and second surfaces) of the two magnet assemblies 12 with relatively strong magnetic field strength face the first and second portions of the A-phase coil 10 and face the first and second portions of the B-phase coil 11, respectively. The A-phase coil 10 and the B-phase coil 11 are arranged at the same interval as the interval between the main magnet 12m and the sub-magnet 12s adjacent to each other in the two magnet assemblies 12.

[0037] Also, as shown in FIG. 4, the arrangement of the north and south poles on the faces of the two magnet assemblies 12 where the magnetic field strength is relatively strong is identical to each other along the X direction. In other words, the magnets, particularly the sub-magnets 12s, in the two magnet assemblies 12 are arranged in the same phase with each other.

[0038] Furthermore, the plurality of magnets provided in the two magnet assemblies 12, particularly the plurality of sub-magnets 12s, have the same shape as each other and are made of the same material as each other. The main magnets 12m and the sub-magnets 12s do not have to have the same shape, and the number of main magnets 12m and the number of sub-magnets 12s provided in the magnet assembly 12 are not limited.

[0039] The magnet holder 13 is made of a resin material or a metal material and has an outer shape of a substantially rectangular parallelepiped in which two recesses 13a and 13b are formed. One magnet assembly 12 is inserted into the recess 13a, and the other magnet assembly 12 is inserted into the recess 13b.

[0040] The magnet holder 13 is fixed to the fixed barrel 6 by screws (not shown). Instead of using the magnet holder 13, the magnet assembly 12 may be directly fixed to the fixed barrel 6 by adhesive.

[0041] 6(a), (b), and (c) show schematic XY cross-sectional views of the linear motor 500 at times T0, T1, and T2, respectively. FIG. 7(a) shows the change over time in the amplitude of the current flowing through the A-phase coil 10 and the B-phase coil 11. FIG. 7(b) shows the change over time in the amplitude of the driving force along the X direction generated in each of the A-phase coil 10 and the B-phase coil 11, and the amplitude of the driving force along the X direction applied to the lens holder 3.

[0042] As shown in FIG. 6(a), at time T0, the A-phase coil 10 is in the phase of the sub-magnet 12s, and the B-phase coil 11 is in the phase of the main magnet 12m. That is, at time T0, the first and second portions of the A-phase coil 10 face the surface of a predetermined sub-magnet 121s of one magnet assembly 12 with a relatively strong magnetic field strength, and the surface of a predetermined sub-magnet 121s of the other magnet assembly 12 with a relatively strong magnetic field strength, respectively.

[0043] Furthermore, the first portion of the B-phase coil 11 faces the surface of the main magnet 121m adjacent to the sub-magnet 121s of one magnet assembly 12, where the magnetic field strength is relatively strong. The second portion of the B-phase coil 11 faces the surface of the main magnet 121m adjacent to the sub-magnet 121s of the other magnet assembly 12, where the magnetic field strength is relatively strong.

[0044] Also, at time T0, as shown in Figure 7(a), the amplitude of the current flowing through the A-phase coil 10 is 0, while voltages are applied to the A-phase coil 10 and the B-phase coil 11 so that the amplitude of the current flowing through the B-phase coil 11 is a predetermined value, i.e., +Q. It is assumed that when a current flows in the clockwise direction in FIG. 5(a) in each of the A-phase coil 10 and the B-phase coil 11, the amplitude of the current is positive. As a result, at time T0, as shown in FIG. 7(b), a driving force in the negative X direction (see also the arrow in FIG. 6(a)) is generated in the B-phase coil 11, causing the lens holder 3 to move in the negative X direction.

[0045] Next, at time T1, a predetermined time after time T0, the A-phase coil 10 is in a phase intermediate between the main magnet 12m and the sub-magnet 12s, as shown in Figure 6(b), and the B-phase coil 11 is also in a phase intermediate between the main magnet 12m and the sub-magnet 12s. At time T1, as shown in Figure 7(a), the amplitude of the current flowing through the A-phase coil 10 is +0.7Q, while voltages are applied to the A-phase coil 10 and the B-phase coil 11 so that the amplitude of the current flowing through the B-phase coil 11 is also +0.7Q. As a result, at time T1, as shown in FIG. 7(b), a driving force in the negative X direction (see also the arrows in FIG. 6(b)) is generated in each of the A-phase coil 10 and the B-phase coil 11, causing the lens holder 3 to move in the negative X direction.

[0046] Then, at time T2, a predetermined time after time T1, 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 sub-magnet 12s, as shown in Figure 6(c). That is, at time T2, the first and second portions of the A-phase coil 10 face the surface of the main magnet 121m of one magnet assembly 12 with a relatively strong magnetic field strength, and the surface of the main magnet 121m of the other magnet assembly 12 with a relatively strong magnetic field strength, respectively.

[0047] Furthermore, the first portion of the B-phase coil 11 faces the surface of the sub-magnet 122s adjacent to the main magnet 121m of one magnet assembly 12, where the magnetic field strength is relatively strong. The second portion of the B-phase coil 11 faces the surface of the sub-magnet 122s adjacent to the main magnet 121m of the other magnet assembly 12, where the magnetic field strength is relatively strong.

[0048] Then, at time T2, as shown in Figure 7(a), voltages are applied to the A-phase coil 10 and the B-phase coil 11 so that the amplitude of the current flowing through the A-phase coil 10 is +Q, while the amplitude of the current flowing through the B-phase coil 11 is 0. As a result, at time T2, as shown in FIG. 7(b), a driving force in the negative X direction (see also the arrow in FIG. 6(c)) is generated in the A-phase coil 10, causing the lens holder 3 to move in the negative X direction.

[0049] Although the above describes the operation of the linear motor 500 at times T0, T1, and T2, the lens holder 3 can be moved smoothly by continuously changing the current flowing through the A-phase coil 10 and the B-phase coil 11 as shown in Figure 7(a). That is, by passing appropriate currents through both the A-phase coil 10 and the B-phase coil 11 depending on the relative positions of the main magnet 12m and the sub-magnet 12s, the lens holder 3 can be moved in a direction parallel to the optical axis O by the driving force shown in Figure 7(b). In addition to the basic control described above, more complex position feedback control and velocity feedback control are performed when driving the lens holder 3 in the focus unit 1, but a description of these will be omitted.

[0050] FIG. 8 shows a partial schematic XY cross-sectional view of the focusing unit 1. As described above, in the linear motor 500, a driving force along the X direction can be generated in the A-phase coil 10 and the B-phase coil 11 by the magnetic flux parallel to the Y direction generated by the main magnet 12m and the current parallel to the Z direction flowing through the A-phase coil 10 and the B-phase coil 11.

[0051] On the other hand, as shown by the arrows in Figure 8, in the linear motor 500, a Lorentz force is generated in the Y direction by the magnetic flux parallel to the X direction generated by the sub-magnet 12s and the current parallel to the Z direction flowing through the A-phase coil 10 and the B-phase coil 11. However, as described above, the angle between the normal to the surface of one magnet assembly 12 where the magnetic field strength is relatively strong and the normal to the surface of the other magnet assembly 12 where the magnetic field strength is relatively strong is 180°.

[0052] As a result, Lorentz forces in opposite directions in the Y direction are generated in the A-phase coil 10 by one magnet assembly 12 and the other magnet assembly 12, and Lorentz forces in opposite directions in the Y direction are also generated in the B-phase coil 11. Therefore, two Lorentz forces in opposite directions in the A-phase coil 10 and the B-phase coil 11 cancel each other out, thereby preventing the generation of unnecessary moments in the A-phase coil 10 and the B-phase coil 11, and ultimately in the lens holder 3. Furthermore, if the angle between the normal to the surface of one magnet assembly 12 with a relatively strong magnetic field strength and the normal to the surface of the other magnet assembly 12 with a relatively strong magnetic field strength is 180°±5°, the Lorentz force in the Y direction can be sufficiently reduced.

[0053] That is, in the focus unit 1, two magnet assemblies 12 are used to generate two Lorentz forces in opposite directions, thereby making it possible to prevent the lens holder 3 from tilting. This makes it possible to suppress deterioration in the optical performance of the focus unit 1, and therefore the interchangeable lens 100.

[0054] As a result of suppressing the generation of the periodic Lorentz force as described above, the generation of vibrations and noise in the lens holder 3 can be suppressed. This makes it possible to prevent degradation of the movie performance of the interchangeable lens 100.

[0055] As described above, the interchangeable lens 100 serving as the optical device according to this embodiment uses the linear motor 500 having the A-phase coil 10 and B-phase coil 11 that are movable in the X direction, and the two Halbach array magnet assemblies 12. This makes it possible to easily provide a linear motor 500 that is smaller than conventional linear motors.

[0056] In addition, in the linear motor 500, the A-phase coil 10 and the B-phase coil 11 and the two magnet assemblies 12 are arranged so as to reduce the Lorentz force generated in each of the A-phase coil 10 and the B-phase coil 11 in a direction perpendicular to the driving direction. This suppresses tilting of the lens holder 3, vibration, and noise generation, thereby suppressing degradation of the optical performance and video performance of the interchangeable lens 100 as the optical device according to this embodiment.

[0057] In the optical device according to this embodiment, not only the focus lens 2 but also optical elements such as a variable magnification (zoom) lens for changing the magnification and an aperture may be moved in the X direction parallel to the optical axis O using the linear motor 500. Furthermore, in the optical device according to this embodiment, not only the focus lens 2 but also a predetermined optical element may be moved in a direction having a component perpendicular to the optical axis O using the linear motor 500 to perform image blur correction.

[0058] [Second embodiment] FIG. 9 shows a partial schematic front view of a focus unit 1 provided in an interchangeable lens as an optical device according to the second embodiment. The interchangeable lens as an optical device according to this embodiment has the same configuration as the interchangeable lens 100 according to the first embodiment, except for the relative orientation of the linear motor 500 with respect to the lens holder 3. Therefore, the same components are given the same reference numerals, and descriptions thereof will be omitted.

[0059] Specifically, in the first embodiment, as shown in FIG. 5(a), the magnetic flux generated by the multiple main magnets 12m of the two magnet assemblies 12 is parallel to a straight line that passes through the center of the linear motor 500 in the YZ cross section and is perpendicular to the optical axis O, i.e., parallel to the Y direction. On the other hand, in this embodiment, as shown in Figure 9, the magnetic flux generated by the multiple main magnets 12m of the two magnet assemblies 12 is a straight line that passes through the center of the linear motor 500 in the YZ cross section and is perpendicular to the optical axis O, i.e., perpendicular to the Y direction (parallel to the Z direction).

[0060] Therefore, in this embodiment, it is possible to prevent the magnetic flux generated by the multiple main magnets 12m of the two magnet assemblies 12 from reaching electronic devices and magnetic devices (not shown) outside the fixed cylinder 6 that are close to the linear motor 500 in the Y direction. This makes it possible to suppress unstable operation of the electronic device or magnetic device.

[0061] As described above, the interchangeable lens serving as the optical device according to this embodiment uses the linear motor 500 having the A-phase coil 10 and B-phase coil 11 that are movable in the X direction, and the two Halbach array magnet assemblies 12. This makes it possible to easily provide a linear motor 500 that is smaller than conventional linear motors.

[0062] In addition, in the linear motor 500, the A-phase coil 10 and the B-phase coil 11 and the two magnet assemblies 12 are arranged so as to reduce the Lorentz force generated in each of the A-phase coil 10 and the B-phase coil 11 in a direction perpendicular to the driving direction. This suppresses tilting, vibration, and noise of the lens holder 3, thereby suppressing degradation of the optical performance and video performance of the interchangeable lens serving as the optical device according to this embodiment.

[0063] In addition, in this embodiment, the linear motor 500 is arranged so that the magnetic flux generated by the multiple main magnets 12m possessed by the two magnet assemblies 12 is a straight line that passes through the center of the linear motor 500 in the YZ cross section and is perpendicular to the optical axis O, i.e., perpendicular to the Y direction. This makes it possible to suppress unstable operation of electronic devices and magnetic devices (not shown) outside the fixed barrel 6 that are close to the linear motor 500 in the Y direction.

[0064] In the linear motor disclosed in Patent Document 1, a magnetic flux is generated radially by a cylindrical magnet assembly. Therefore, it is very difficult to adjust the direction of magnetic flux generation so as to suppress unstable operation in electronic devices and magnetic devices (not shown) outside the fixed barrel, as in this embodiment.

[0065] [Third embodiment] FIG. 10(a) shows a schematic exploded perspective view of a focus unit 1 provided in an interchangeable lens as an optical device according to the third embodiment. FIG. 10(b) shows a partial schematic front view of the focus unit 1. The interchangeable lens as an optical device according to this embodiment has the same configuration as the interchangeable lens 100 according to the first embodiment, except for the relative arrangement between the A-phase coil 10 and B-phase coil 11 in the linear motor 500 and the two magnet assemblies 12. Therefore, the same members are given the same reference numerals and descriptions thereof will be omitted.

[0066] Specifically, in this embodiment, the A-phase coil 10 and the B-phase coil 11 in the linear motor 500 are sandwiched between two magnet assemblies 12 while being arranged with an appropriate air gap secured between the two magnet assemblies 12. FIG. 11(a) shows a schematic XZ cross-sectional view of the linear motor 500 shown in FIG. 10(b) taken along line 11A-11A. FIG. 11(b) is a partial schematic front view of the linear motor 500 as seen from the positive side in the X direction.

[0067] As shown in FIGS. 11( a ) and 11 ( b ), in this embodiment, the normals of the surfaces of the two magnet assemblies 12 where the magnetic field strength is relatively strong are each oriented inward in the Z direction of the linear motor 500 . That is, in this embodiment, the surfaces of the two magnet assemblies 12 with relatively strong magnetic field strengths face each other. The surfaces of the two magnet assemblies 12 with relatively strong magnetic field strength face the first and second portions of the A-phase coil 10 and also face the first and second portions of the B-phase coil 11, respectively.

[0068] In this embodiment, two magnet holders 13 are provided, each having a recess 13a into which a magnet assembly 12 is inserted, and each having an outer shape of a substantially rectangular parallelepiped. In this embodiment, the driving of the lens holder 3 can be controlled using the linear motor 500 in the same manner as in the first embodiment.

[0069] FIG. 12 shows a partial schematic XZ cross-sectional view of the focus unit 1. As shown by the arrows in FIG. 12, in the linear motor 500, a Lorentz force is generated in the Z direction by the magnetic flux parallel to the X direction generated by the sub-magnet 12s and the current parallel to the Y direction flowing through the A-phase coil 10 and the B-phase coil 11. However, the Lorentz forces in opposite directions in the Z direction are generated in the A-phase coil 10 by one magnet assembly 12 and the other magnet assembly 12, and the Lorentz forces in opposite directions in the Z direction are also generated in the B-phase coil 11. Therefore, two Lorentz forces in opposite directions in the A-phase coil 10 and the B-phase coil 11 cancel each other out, thereby suppressing the generation of unnecessary moments in the A-phase coil 10 and the B-phase coil 11, and ultimately in the lens holder 3.

[0070] As described above, the interchangeable lens serving as the optical device according to this embodiment uses the linear motor 500 having the A-phase coil 10 and B-phase coil 11 that are movable in the X direction, and the two Halbach array magnet assemblies 12. This makes it possible to easily provide a linear motor 500 that is smaller than conventional linear motors.

[0071] In addition, in the linear motor 500, the A-phase coil 10 and the B-phase coil 11 and the two magnet assemblies 12 are arranged so as to reduce the Lorentz force generated in each of the A-phase coil 10 and the B-phase coil 11 in a direction perpendicular to the driving direction. This suppresses tilting, vibration, and noise of the lens holder 3, thereby suppressing degradation of the optical performance and video performance of the interchangeable lens serving as the optical device according to this embodiment.

[0072] In the optical device according to this embodiment, the A-phase coil 10 and the B-phase coil 11 are arranged in the linear motor 500 so as to be sandwiched between the two magnet assemblies 12. Therefore, by generating magnetic flux by the two magnet assemblies 12 so as to be directed toward the inside of the linear motor 500, it is possible to prevent the magnetic flux from reaching electronic devices and magnetic devices (not shown) located outside the linear motor 500. This makes it possible to suppress unstable operation of the electronic device or magnetic device.

[0073] Although the preferred embodiments have been described above, the present invention is not limited to these embodiments and various modifications and changes are possible within the scope of the gist thereof.

[0074] The disclosure of this embodiment includes the following configuration. (Configuration 1) An optical device comprising an optical element and a linear motor that moves the optical element in a predetermined direction, wherein the stator of the linear motor includes first and second magnet assemblies each having a plurality of magnets in a Halbach array aligned along the predetermined direction, and the mover of the linear motor includes a plurality of coils that are coupled to the optical element so that their respective winding axes are parallel to the predetermined direction, and the first and second portions of each coil face a first surface of the first magnet assembly that has a relatively strong magnetic field strength and a second surface of the second magnet assembly that has a relatively strong magnetic field strength, respectively. (Configuration 2) An optical device described in Configuration 1, characterized in that the linear motor is arranged so that the normals of the first and second surfaces are perpendicular to a line passing through the center of the linear motor in a cross section perpendicular to the optical axis of the optical element and perpendicular to the optical axis. (Configuration 3) The optical device according to configuration 1 or 2, wherein the first and second magnet assemblies are arranged so that the first and second surfaces face each other. (Configuration 4) An optical device described in any one of configurations 1 to 3, characterized in that the multiple sub-magnets of each of the first and second magnet assemblies are arranged in the same phase with each other in a predetermined direction. (Configuration 5) The optical device according to any one of configurations 1 to 4, wherein the angle between the normal to the first surface and the normal to the second surface is 180°. (Configuration 6) An optical device described in any one of configurations 1 to 5, characterized in that the multiple sub-magnets of each of the first and second magnet assemblies have the same shape and are made of the same material. (Configuration 7) The optical device according to any one of configurations 1 to 6, wherein each of the plurality of coils has a rectangular cylindrical shape in a cross section perpendicular to the winding axis. (Configuration 8) The optical device according to any one of configurations 1 to 7, wherein the optical element is a focus lens for changing the focal length of the optical device. (Configuration 9) The optical device according to any one of configurations 1 to 8, wherein the predetermined direction is a direction parallel to the optical axis of the optical element. (Configuration 10) An optical device described in any one of configurations 1 to 9, characterized in that the multiple coils include first and second coils arranged at a distance equal to the distance between adjacent main magnets and sub-magnets in the first and second magnet assemblies. (Configuration 11) An optical device described in any one of configurations 1 to 10, characterized in that the multiple coils and the first and second magnet assemblies are arranged so that the Lorentz force generated in a direction perpendicular to the first and second planes when current flows in each coil is reduced. (Configuration 12) An imaging device comprising the optical device according to any one of configurations 1 to 11 and an imaging element for capturing an image formed by the optical device. [Explanation of symbols]

[0075] 2. Focus lens (optical element) 10 A phase coil 11 B-phase coil 12 Magnet Assembly 100 Interchangeable lenses (optical devices) 500 Linear Motor

Claims

1. an optical element; a linear motor that moves the optical element in a predetermined direction; Equipped with the stator of the linear motor includes first and second magnet assemblies each having a plurality of magnets in a Halbach array along the predetermined direction; An optical device characterized in that the mover of the linear motor includes a plurality of coils coupled to the optical element so that their respective winding axes are parallel to the predetermined direction, and first and second portions of each coil face a first surface of the first magnet assembly having a relatively strong magnetic field strength and a second surface of the second magnet assembly having a relatively strong magnetic field strength, respectively.

2. The optical device according to claim 1, characterized in that the linear motor is arranged so that the normals of the first and second surfaces are perpendicular to a line passing through the center of the linear motor in a cross section perpendicular to the optical axis of the optical element and perpendicular to the optical axis.

3. 2. The optical device of claim 1, wherein the first and second magnet assemblies are arranged so that the first and second surfaces face each other.

4. 2. The optical device according to claim 1, wherein the plurality of sub-magnets of each of the first and second magnet assemblies are arranged in the same phase with each other in the predetermined direction.

5. 2. The optical device according to claim 1, wherein an angle between the normal to the first surface and the normal to the second surface is 180 degrees.

6. 2. The optical device according to claim 1, wherein the plurality of sub-magnets of each of the first and second magnet assemblies have the same shape and are made of the same material.

7. 2. The optical device according to claim 1, wherein each of the plurality of coils has a rectangular cylindrical shape in a cross section perpendicular to the winding axis.

8. 2. The optical device according to claim 1, wherein the optical element is a focus lens for changing the focal length of the optical device.

9. 2. The optical device according to claim 1, wherein the predetermined direction is a direction parallel to the optical axis of the optical element.

10. 2. The optical device according to claim 1, wherein the plurality of coils include first and second coils arranged at the same interval as the interval between adjacent primary and secondary magnets in the first and second magnet assemblies.

11. 2. The optical device of claim 1, wherein the plurality of coils and the first and second magnet assemblies are arranged such that a Lorentz force in a direction perpendicular to the first and second planes generated when a current flows in each coil is reduced.

12. An optical device according to any one of claims 1 to 11; an imaging element that captures an image formed by the optical device; An imaging device comprising:

Images