Optical axis adjustment actuator and optical axis adjustment device

Abstract

An optical axis adjusting device and an actuator therefor are provided that can suppress fluttering of the optical axis of an anisotropic optical element even during high-speed rotation. [Solution] In an optical axis adjustment actuator (10) that can be fitted with a wedge prism and is rotationally driven by a voice coil motor, a bearing structure is constructed by sandwiching a rolling element (4) between a groove (212) on the movable part (2) side and a groove (312) on the fixed part (3) side that are radially opposed to each other.

Description

[Technical Field]

[0001] The present invention relates to an optical axis adjustment actuator and an optical axis adjustment device. [Background technology]

[0002] Optical axis adjustment devices that rotate an anisotropic optical element, such as a wedge prism, around the optical axis of the optical element using electromagnetic force are known, and one known configuration for achieving this is an actuator that rotates the wedge prism using electromagnetic force. The actuator has a fixed part and a movable part for holding the wedge prism. The fixed part and the movable part have grooves on their opposing main surfaces that extend along the rotational direction of the movable part. The grooves in the fixed part and the movable part face each other in the axial direction of the rotational motion of the movable part and sandwich a rolling element therebetween. In the actuator, this configuration restricts the driving direction of the rotation of the movable part (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-137734 Summary of the Invention [Problem to be solved by the invention]

[0004] On the other hand, depending on the application of the optical axis adjustment device, such as optical wireless communication, the actuator is required to be able to rotate the wedge prism at high speed. In conventional actuators with a structure in which rolling elements are sandwiched between grooves in the axial direction, in the high-speed range where a large thrust is generated, the posture of the moving part during rotation can deviate from the intended posture due to assembly or part precision, or play that occurs between the rolling elements and the grooves, resulting in the optical axis of the wedge prism flapping.

[0005] An object of one aspect of the present invention is to provide an optical axis adjusting device and an actuator therefor that can suppress fluttering of the optical axis of an anisotropic optical element even during high-speed rotation. [Means for solving the problem]

[0006] In order to solve the above problems, an optical axis adjustment actuator according to one aspect of the present invention has a fixed part, a movable part that holds an anisotropic optical element and is rotatably attached to the fixed part, a driving magnetic field generator that is arranged on one of the movable part and the fixed part along a rotation direction of the movable part, a coil that is arranged on the other of the movable part and the fixed part along the rotation direction at a position that overlaps with the driving magnetic field generator, a first groove that is formed in the movable part along a circumferential direction in the rotation direction, a second groove that is formed in the fixed part along the circumferential direction in the rotation direction, and three or more rolling elements that are sandwiched between the first groove and the second groove, and the first groove and the second groove are radially opposed to each other in the rotation direction.

[0007] In order to solve the above problem, an optical axis adjustment device according to one aspect of the present invention includes the above optical axis adjustment actuator and an anisotropic optical element held by the movable part. [Effects of the Invention]

[0008] According to one aspect of the present invention, it is possible to realize an optical axis adjusting device and an actuator therefor that can suppress fluttering of the optical axis of an anisotropic optical element even during high-speed rotation. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a plan view schematically showing an optical axis adjustment actuator according to a first embodiment of the present invention. [Figure 2] 1 is a cross-sectional view schematically showing a vertical cross section of an optical axis adjustment actuator according to a first embodiment of the present invention. [Figure 3]1 is a cross-sectional view that schematically shows a cross section of an optical axis adjustment actuator according to a first embodiment of the present invention. [Figure 4] 1 is an exploded perspective view schematically showing the configuration of an optical axis adjustment actuator according to a first embodiment of the present invention. [Figure 5] 3 is a diagram schematically showing a first example of the arrangement of a drive magnet and a coil in the optical axis adjustment actuator according to the first embodiment of the present invention. FIG. [Figure 6] 4 is a diagram schematically showing a second example of the arrangement of the drive magnets and coils in the optical axis adjustment actuator according to the first embodiment of the present invention. FIG. [Figure 7] FIG. 10 is a diagram schematically showing an example of the arrangement of drive magnets in an optical axis adjustment actuator according to a second embodiment of the present invention. [Figure 8] FIG. 10 is a diagram schematically showing an example of the arrangement of coils in an optical axis adjustment actuator according to a second embodiment of the present invention. [Figure 9] FIG. 10 is a diagram showing an example of the arrangement of drive magnets and coils, as viewed from the front, in an optical axis adjustment actuator according to a third embodiment of the present invention. [Figure 10] FIG. 10 is a diagram schematically showing an example of the arrangement of drive magnets and coils, as viewed from the side, in an optical axis adjustment actuator according to a third embodiment of the present invention. [Figure 11] FIG. 10 is a diagram schematically illustrating the configuration of an optical axis adjusting device according to a fourth embodiment of the present invention. [Figure 12] FIG. 10 is a diagram for explaining an example of control of the optical axis adjusting device by the control device according to the fourth embodiment of the present invention. [Figure 13] FIG. 10 is a diagram showing an example of a scanning locus of a beam in the fourth embodiment of the present invention. [Figure 14] FIG. 10 is a diagram showing another example of the scanning locus of the beam in the fourth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Embodiment 1] An embodiment of an optical axis adjustment actuator according to the present invention will now be described. Fig. 1 is a plan view schematically showing the optical axis adjustment actuator of this embodiment. Fig. 2 is a cross-sectional view schematically showing a longitudinal section of the optical axis adjustment actuator of this embodiment, and Fig. 3 is a cross-sectional view schematically showing a transverse section of the optical axis adjustment actuator of this embodiment. Fig. 4 is an exploded perspective view schematically showing the configuration of the optical axis adjustment actuator of this embodiment. Fig. 5 schematically shows a first example of the arrangement of drive magnets and coils in this embodiment, and Fig. 6 schematically shows a second example of the arrangement of drive magnets and coils in this embodiment.

[0011] 1 to 4, the optical axis adjustment actuator 10 is configured by combining a movable part 2 with a fixed part 3 via rolling elements 4. The optical axis adjustment actuator 10 is configured from an appropriate material, examples of which include a resin composition containing a filler such as a resin or glass fiber that may be surface-treated, a metal such as aluminum, stainless steel, galvanized steel sheet or non-oriented electromagnetic steel sheet, a magnet such as NdFeB, and a magnet wire.

[0012] Movable unit 2 is a member that can hold a wedge prism (not shown), which is an example of an anisotropic optical element, and that can rotate around the optical axis of the optical element that it holds. Movable unit 2 includes rotating rotor 21, drive magnet yokes 22a and 22b, sensor magnet yoke 23, drive magnets 24a and 24b, and sensor magnet 25. Rotating rotor 21 is a substantially annular plate-like member, and a circular opening in the center serves as wedge prism fixing portion 211, and is configured so that a wedge prism, which is a type of anisotropic optical element, can be fitted into the opening.

[0013] The fixed part 3 is a member that rotatably holds the movable part and includes an outer ring stator 31, a rotor spacer 32, coils 33a and 33b, a flexible printed circuit (FPC) 34, a Hall element 35, drive magnet back yokes 36a and 36b, a sensor magnet back yoke 37, a sensor height adjustment base 38, and a main plate 39.

[0014] The drive magnet back yokes 36a and 36b are disposed opposite the drive magnets 24a and 24b in the axial direction.

[0015] The sensor magnet yoke 23, the sensor magnet 25, the sensor magnet back yoke 37, and the Hall element 35 constitute a sensor unit that detects the position of the movable part 2 in the rotation direction.

[0016] The sensor magnet 25 corresponds to a detection magnetic field generating unit arranged along the rotation direction in the movable part 2, and the Hall element 35 is arranged along the rotation direction in the fixed part 3 at a position that overlaps with the sensor magnet 25 in the axial direction.

[0017] In the movable part 2, the drive magnets 24a and 24b are fitted into holes provided in the rotor 21, and the drive magnet yokes 22a and 22b are fixed to these holes. The polarization direction of the drive magnets 24a and 24b is the optical axis direction, and the drive magnet yokes 22a and 22b are arranged to face these magnets.

[0018] Furthermore, in the fixed portion 3, the coils 33a and 33b are fixed on the FPC 34. The coils 33a and 33b are each arranged so that three coils are adjacent to each other. Each of the coils is a coreless coil. The wiring of the FPC 34 is connected to each coil, and the amount and direction of current in each coil can be adjusted appropriately. In the optical axis adjustment actuator 10, the drive magnets 24a and 24b and the coils 33a and 33b form a voice coil motor.

[0019] One drive magnet 24a is disposed for coil 33a, and one drive magnet 24b is disposed for coil 33b. Drive magnets 24a and 24b each have two regions with different polarization directions. As shown in FIG. 5, drive magnets 24a and 24b each generate a magnetic field such that the polarization directions are opposite at a specific position (the circumferential center of the middle coil of the three coils in this embodiment). Thus, in this embodiment, the portion where the polarization direction is reversed may be the boundary between the north and south poles of a single magnet as shown in FIG. 5, or may be the abutment between the north and south poles of different drive magnets 24a1 and 24a2 or drive magnets 24b1 and 24b2 as shown in FIG. 6.

[0020] The drive magnets 24a, 24b and the coils 33a, 33b each have an arc shape in plan view that matches the shape of the approximately annular portion of the optical axis adjustment actuator 10. The direction of current flowing through the coils in the region where the magnetic flux intersects is indicated by arrow B in Fig. 5, and the direction of thrust generated thereby is indicated by arrow A that follows the approximately circumferential direction of the movable part 2. In this way, the drive magnets 24a, 24b constitute a drive magnetic field generator that is arranged in the movable part 2 along the rotation direction of the movable part 2, and the coils 33a, 33b constitute coils that are arranged in the fixed part 3 at positions that overlap with the drive magnetic field generator and along the rotation direction.

[0021] Furthermore, a movable part groove 212 is formed around the entire outer circumferential edge of the rotating rotor 21, and a fixed part groove 312 is formed around the entire inner circumferential edge of the outer ring stator. The cross-sectional shape of each movable part groove 212 is an arc. In this way, the movable part groove 212 corresponds to a first groove formed in the movable part 2 along the circumferential direction in the rotation direction of the movable part 2, and the fixed part groove 312 corresponds to a second groove formed along the circumferential direction in the rotation direction and facing the first groove in the radial direction.

[0022] The movable part groove 212 and the fixed part groove 312 face each other in the radial direction and sandwich each of the rolling elements 4, which are multiple spheres. In this way, the movable part groove 212 and the fixed part groove 312 face each other in the radial direction in the rotational direction and sandwich each of the rolling elements 4, and the movable part groove 212, the fixed part groove 312, and the rolling elements 4 form a bearing structure. The inner circumferential wall surfaces of the cross sections of the movable part groove 212 and the fixed part groove 312 are both approximately arc-shaped, and the shape of the inner circumferential wall surfaces has a radius of curvature slightly larger than the radius of curvature of the rolling elements 4.

[0023] Furthermore, the outer ring stator 31 is fastened to the rotor spacer 32 by screws 51, the FPC 34 and drive magnet back yokes 36a and 36b are fastened to the main plate 39 by screws 52, and the main plate 39 is fastened to the rotor spacer 32 by screws 53.

[0024] Furthermore, the distance between the Hall element 35, the sensor magnet back yoke 37 and the sensor magnet 25 is adjusted appropriately by the sensor height adjustment base 38.

[0025] [Major effects] The polarization direction of the drive magnets 24a, 24b is the optical axis direction (not shown), and drive magnet back yokes 36a, 36b are arranged to face them. This generates an attractive force in the optical axis direction, which attracts the movable part 2 to the fixed part 3. This axial biasing force suppresses fluttering of the movable part in the axial direction.

[0026] As described above, the radii of curvature in the cross-sectional shapes of the movable part groove 212 and the fixed part groove 312 are both slightly larger than the radii of curvature of the rolling elements 4. Therefore, even if the movable part 2 and the fixed part 3 contain errors (tolerances) due to the groove shapes, the size of the rolling elements 4, or the assembly of the movable part 2 and the fixed part 3, causing a positional deviation of the movable part 2 relative to the fixed part 3, the positional relationship between the movable part 2 and the fixed part 3 is maintained so that one of the movable part groove 212 and the fixed part groove 312 is slightly offset from the other while sandwiching the rolling elements 4. In this way, in the optical axis adjustment actuator 10, even if a tolerance is included, the entire movable part 2 moves in the axial direction relative to the fixed part 3, and the tolerance is absorbed without tilting the movable part 2 relative to the fixed part 3. Therefore, it is possible to eliminate backlash between the movable part groove 212, the fixed part groove 312, and the rolling elements 4. This prevents the movable part 2 from flapping in the optical axis direction due to the force in the optical axis direction generated by changes in posture caused by assembly or part accuracy or play between the rolling element and the groove exceeding the force holding the movable part 2.

[0027] In this way, the optical axis adjustment actuator 10 can suppress fluttering in the optical axis direction when rotated because it can eliminate backlash between the rolling elements 4 and the grooves 212, 312 provided in the movable part 2 and the fixed part 3 and hold them in place, thereby suppressing fluttering in the optical axis direction when rotated. As a result, in the optical axis adjustment actuator 10 that rotates the wedge prism, fluttering in the optical axis direction is suppressed even when rotating at high speeds, and the movable part 2 can be rotated at high speed.

[0028] Furthermore, because the voice coil motor constructed in this embodiment is single-phase and coreless, thrust ripple due to commutation or cogging is small, allowing for delicate and smooth control. This suppresses the generation of micro-vibrations during rotation. This is therefore advantageous from the perspective of stabilizing laser directionality when used in optical wireless communication.

[0029] In addition, the coil inductance is small and the movable part 2 is lightweight, which results in excellent operational response and allows for high frequency operation.

[0030] Furthermore, since the movable part 2 is supported by the fixed part 3 by the bearing structure, the movable part 2 tends to be lightweight. This reduces the current consumption required for driving, making it easier to make the controller smaller.

[0031] Voice coil motors also generate thrust proportional to the current due to the influence of magnetic fields, etc., making it possible to precisely control the load. Furthermore, the thrust generated by passing current through the coil directly controls the moving part, making it advantageous for precise rotation.

[0032] Furthermore, in a voice coil motor, the coil is arranged so as to surround the outer periphery of the anisotropic optical element, so the voice coil motor can have a thin structure.

[0033] Furthermore, in the optical axis adjustment actuator 10, the distance between the Hall element 35, the sensor magnet back yoke 37, and the sensor magnet 25 is adjusted by the sensor height adjustment base 38. Since the detected magnetic flux density distribution changes depending on the distance, the above configuration is suitable from the viewpoint of adjusting the distance to a value at which the desired magnetic flux density distribution can be detected.

[0034] Other embodiments of the present invention will be described below. In the following description of the other embodiments, for the sake of convenience, the same reference numerals will be used to designate components having the same functions as those described in the previous embodiment, and the description thereof will not be repeated.

[0035] [Embodiment 2] The features of the optical axis adjustment actuator of this embodiment are shown schematically in Figures 7 and 8. The optical axis adjustment actuator of this embodiment has a driving magnet and coil arranged all around, and has the same configuration as the optical axis adjustment actuator 10 of the above-described first embodiment, except that it does not have a position detection magnet, hall element, yoke, or back yoke.

[0036] As shown in Figures 7 and 8, the optical axis adjustment actuator 20 has a movable part and a fixed part. The movable part includes a rotating rotor, a drive magnet yoke, and a drive magnet 241. The drive magnet 241 is arranged around the entire circumference on the outer periphery of the central opening of the rotating rotor. The drive magnet 241 has twelve sections, and the dashed lines in the figures indicate the boundaries of the magnetic poles, forming a magnetic field in which adjacent two sections have different magnetic poles (for example, a repetition of N, S, ...). Although not shown, the drive magnet yoke is arranged around the entire circumference on the main surface of the rotating rotor 21 opposite the drive magnet 241, corresponding to the drive magnet 241.

[0037] The fixed part includes an outer ring stator, a rotor spacer, coils 331, an FPC, a drive magnet back yoke, and a main plate. The coils 331 are coreless coils that are approximately fan-shaped trapezoids when viewed from above, as in the first embodiment, and nine coreless coils are arranged in a line in the circumferential direction. The drive magnet back yoke is arranged around the entire circumference in correspondence with the drive magnets 241.

[0038] In the optical axis adjustment actuator 20, the movable part is driven to rotate in the desired direction by supplying current to each of the coils 331 from the FPC in an appropriate direction according to the magnetic pole of the drive magnet 241. By appropriately switching the direction of the supplied current, the movable part can be driven to rotate continuously in one direction, and the rotation speed of the movable part can be controlled by the amount of current supplied. In addition, the position of the movable part relative to the fixed part in the rotation direction can be controlled by, for example, combining an encoder with the optical axis adjustment actuator 20 to obtain information on the amount of rotation, rotation speed, or rotation direction of the movable part.

[0039] In the second embodiment, as in the first embodiment, the fluttering of the wedge prism during rotation can be prevented.

[0040] [Embodiment 3] 9 and 10 are schematic diagrams showing the features of the optical axis adjustment actuator of this embodiment. The optical axis adjustment actuator of this embodiment is configured in the same way as the optical axis adjustment actuator 20 of the above-described second embodiment, except that a driving magnet and a coil are arranged so as to face each other in the radial direction, and the actuator further has a configuration for biasing the movable part.

[0041] The optical axis adjustment actuator 30 has a movable part and a fixed part. In this embodiment, both the movable part and the fixed part are made of cylindrical bodies, and the optical axis adjustment actuator 30 can be made of these double-tube structure, for example, an inner cylindrical part which is the movable part and an outer cylindrical part which is the fixed part.

[0042] 9 and 10, in the optical axis adjustment actuator 30, twelve-segment drive magnets 242 are arranged around the entire outer circumferential surface of the inner cylinder, and nine coils 332 are arranged around the entire inner circumferential surface of the outer cylinder. The correspondence between the drive magnets 242 and the coils 332 in the circumferential direction is the same as in the second embodiment. The configuration of the inner cylinder is the same as that of the movable part in the second embodiment, and the configuration of the outer cylinder is the same as that of the fixed part in the second embodiment.

[0043] An anisotropic optical element such as a wedge prism is disposed in the inner cylinder closer to the center than the drive magnet 242. The central axis (rotation axis) of the inner cylinder and the optical axis of the optical element are common to each other. Furthermore, for example, a roughly semicircular movable groove is formed radially outward at the end of the inner cylinder, and a roughly semicircular fixed groove is formed radially inward at the end of the outer cylinder, facing the groove on the inner cylinder side. Three or more spherical rolling elements are sandwiched between the movable groove and fixed groove, which face each other in the radial direction.

[0044] The optical axis adjustment actuator 30 further includes a biasing member that biases the inner cylinder portion in the axial direction. The biasing member is, for example, an elastic member such as a spring. The biasing member biases the inner cylinder portion in the axial direction relative to the fixed portion with a strength equivalent to the magnetic force (such as the magnetic force between a magnet and a back yoke) that attracts the movable portion and the fixed portion in the first and second embodiments. The biasing member biases only the inner cylinder portion in the axial direction relative to the outer cylinder portion that is fixed in the axial direction. However, if the inner cylinder portion is fixed in the axial direction, the biasing member may bias the outer cylinder portion in the axial direction relative to the inner cylinder portion. Alternatively, the biasing member may bias both the inner cylinder portion and the outer cylinder portion that are movable in the axial direction so that the force acting between them has a strength equivalent to the magnetic force.

[0045] The optical axis adjustment actuator 30 also provides the same effects as the optical axis adjustment actuator 20. Furthermore, the optical axis adjustment actuator 30 has a smaller moment of inertia than the optical axis adjustment actuator 20, which is advantageous from the viewpoint of rotating the movable part at a higher speed.

[0046] [Embodiment 4] In this embodiment, the optical axis adjustment actuator described above is applied to an optical wireless communication device.

[0047] As shown in FIG. 11, the optical wireless communication device 100 includes an optical beam output unit 110, a communication optical system 120, a beacon optical system 130, and a central processing unit (CPU) 140.

[0048] The optical beam output unit 110 is a part that outputs an optical beam emitted from the optical wireless communication device 100. The optical beam may be, for example, a signal light in optical wireless communication or a beacon light for identifying a communication partner. The optical beam output unit 110 may be, for example, a connector that forms the end of the optical path of the optical beam, or may be a group of various devices for generating the signal light or beacon light.

[0049] The communication optical system 120 includes two first optical axis adjustment devices 121. Each of the first optical axis adjustment devices 121 has a configuration in which a wedge prism is attached to the optical axis adjustment actuator 10 in the first embodiment.

[0050] The beacon optical system 130 includes two second optical axis adjustment devices 131. Each of the second optical axis adjustment devices 131 has a configuration in which a wedge prism is attached to the optical axis adjustment actuator 20 in embodiment 2. Each of the second optical axis adjustment devices 131 further has an encoder for detecting the rotational drive of the wedge prism. The encoder is connected to the CPU 140, and the second optical axis adjustment device 131 is configured so that a signal output from the encoder is also sent to the CPU 140.

[0051] The CPU 140 is a device that controls the operation of the light beam output unit 110, the communication optical system 120, and the beacon optical system .

[0052] In addition to the above configuration, the optical wireless communication device 100 also includes an optical system for configuring the optical path of the optical beam output from the optical beam output unit 110. Such an optical system can be constructed appropriately using known optical elements based on known techniques in optical wireless communication.

[0053] During optical wireless communication, the optical wireless communication device 100 drives the beacon optical system 130 to capture a communication partner, and then drives the communication optical system 120 to perform optical wireless communication. To capture a communication partner, the optical beam output unit 110 outputs a beacon light, and the beacon light is converted into a divergent beam by, for example, a beam divergence angle control element (not shown) in the beacon optical system 130. The CPU 140 outputs a divergent beam based on information about the estimated position of the communication partner on the trajectory. Then, the movable parts of the two second optical axis adjustment devices 131, 131 are rotationally driven to cause the divergent beam to scan.

[0054] The optical wireless communication device 100 narrows the beam diameter of the divergent beam so that the communication partner found during the scanning process is included in the scanning area in front of it, then reduces the scanning area while capturing the communication partner, and finally reduces the beam diameter of the beacon light to a collimated light with a constant beam diameter.

[0055] Next, we will explain one aspect of control of the optical axis adjustment devices by the CPU 140. As shown in Fig. 12, the CPU 140 acquires the rotational frequency of the wedge prism of each optical axis adjustment device as a command value from an input device such as an external device or internal memory. Then, the CPU 140 converts, for example, the command value for frequency setting into each frequency.

[0056] Next, the CPU 140 acquires output signals of the rotational position and rotational movement of the wedge prism from each optical axis adjustment device as current values.

[0057] Next, the CPU 140 performs feedback control to fill the gap between the command value and the current value. For example, the CPU 140 acquires data from the encoders of the optical axis adjustment actuators for the two wedge prisms in each optical axis adjustment device and divides the amount of change by a specified interval Δt. The CPU 140 then performs feedback control using the fed-back current value of angular velocity and the angular velocity of the target frequency.

[0058] Next, the CPU 140 outputs a signal (motor rotation output) of information on the current to be supplied to the coil of the optical axis adjustment actuator in each optical axis adjustment device as a control value to the power supply for the coil. In this way, the CPU 140 manages the rotation frequency and operation time of the wedge prism in each optical axis adjustment device.

[0059] Regarding the command values, for example, the command values ​​for scanning the beacon light when capturing a communication partner are determined as follows. First, the relationship between the projection coordinates on the front XY plane of the transmitted light through each wedge prism of the two second optical axis adjustment devices 131, the rotation frequency of each wedge prism, and the rotation time of each wedge prism is established. Next, using geometric optics, the projection coordinates on the XY plane of the transmitted light at the rotation position of each wedge prism, the angle on the XZ plane, and the angle on the YZ plane are calculated. Next, the trajectory of the beacon light is analyzed based on the calculation results.

[0060] As an example of this analysis, FIG. 13 shows an example of the conditions under which the beacon light traces a spiral trajectory in the XY plane (front). In the figure, rotational frequency f1 represents the rotational frequency of the wedge prism on the light source side (light beam output unit 110) in the beacon optical system 130, and rotational frequency f2 represents the rotational frequency of the wedge prism on the communication partner side in the beacon optical system 130. The dotted line in the figure indicates the relationship between the rotation angle of the wedge prism on the light source side and time, and the solid line in the figure indicates the relationship between the rotation angle of the wedge prism on the communication partner side and time. As shown in FIG. 13, by increasing the rotational frequency of each wedge prism in the beacon optical system 130, it is possible to trace a tighter spiral trajectory.

[0061] As an example of this analysis, an example of the conditions under which the beacon light traces a trajectory of a different shape on the XY plane (front) is shown in Fig. 14. In this way, by appropriately controlling the rotational motion of each of the two wedge prisms in the beacon optical system 130, the optical axis of the beacon light is adjusted so that it traces a dense trajectory of various shapes on the front.

[0062] When a communication partner is captured, the CPU 140 performs optical wireless communication with the captured communication partner. In optical wireless communication, the optical beam output unit 110 outputs a communication signal light, and the CPU 140 acquires position information of the received signal light using a beam splitter and a photodetector (not shown), and based on that information, rotates the optical axis adjustment actuators of each first optical axis adjustment device 121 in the communication optical system 120 at an appropriate speed and angle to fine-tune the optical axis of the output signal light. This suppresses the influence of external disturbances such as meteorological disturbances or space propagation disturbances on optical wireless communication, thereby achieving stable optical wireless communication.

[0063] In this embodiment, all of the optical axis adjustment devices are so-called transmission-type optical axis adjustment devices that have a configuration in which the optical axis is adjusted by rotating an anisotropic optical element, and therefore, optical connections between the light beam output unit and the optical axis adjustment device, or between the optical axis adjustment devices, can be adequately realized by general-purpose optical members such as connectors.

[0064] Furthermore, in a transmissive optical axis adjustment device, the aperture of the anisotropic optical element only needs to be equal to or larger than the beam diameter of the light beam, so a highly versatile device can be constructed that is not dependent on the diameter of the light beam.

[0065] In addition, in this embodiment, both the communication optical system 120 and the beacon optical system 130 have a pair of wedge prisms, and each wedge prism has the above-mentioned optical axis adjustment actuator, but it can easily be realized to add further sets of wedge prisms and optical axis adjustment actuators in the optical axis direction in each optical system.

[0066] Furthermore, in any of the optical axis adjustment devices of the present embodiment, the wedge prism (movable part) can be directly rotated by the voice coil motor, and can be rotated with higher precision than the high resolution of the encoder that detects 360° rotation. Therefore, in the beacon optical system 130, it is possible to achieve rotational driving of the wedge prism without impairing the precision of detecting the rotational position of the wedge prism.

[0067] Other Embodiments In the embodiments of the present invention, optical elements other than wedge prisms can be applied as long as they have anisotropy. Examples of anisotropic optical elements include metalenses and polarizing elements in addition to wedge prisms.

[0068] In an embodiment of the present invention, the movable part groove may be located on the radially outer side and the fixed part groove may be located on the radially inner side. Furthermore, the movable part groove and the fixed part groove do not have to be formed around the entire circumference of the movable part, and multiple grooves of each type may be formed, as long as the effect of the present invention (i.e., the effect of preventing fluttering by displacing the entire movable part in the axial direction due to rotational driving) can be obtained.

[0069] 〔summary〕 A first aspect of the present invention is an optical axis adjustment actuator (10) including a fixed part (3), a movable part (2) that holds an anisotropic optical element (wedge prism) and is rotatably attached to the fixed part, a driving magnetic field generator disposed on one of the movable part and the fixed part along the rotational direction of the movable part, coils (33 a, 33 b) disposed on the other of the movable part and the fixed part along the rotational direction at a position overlapping with the driving magnetic field generator, a first groove (movable part groove 212) formed in the movable part along the circumferential direction in the rotational direction, a second groove (fixed part groove 312) formed in the fixed part along the circumferential direction in the rotational direction, and three or more rolling elements (4) sandwiched between the first groove and the second groove, wherein the first groove and the second groove are radially opposed to each other in the rotational direction. According to the first aspect, an actuator for an optical axis adjustment device can be realized that suppresses fluttering of the optical axis of the anisotropic optical element even during high-speed rotation.

[0070] A second aspect of the present invention is the first aspect, wherein the first groove is formed around the entire outer periphery of the movable part, and the second groove is formed around the entire outer edge of the fixed part opposite the outer periphery. This second aspect is even more effective from the viewpoint of easily realizing the bearing structure.

[0071] A third aspect of the present invention is the first or second aspect, in which the coil is a coreless coil. The third aspect is even more effective from the viewpoint of suppressing the occurrence of cogging during rotation of the movable part.

[0072] A fourth aspect of the present invention is any of the first to third aspects, in which the drive magnetic field generator is composed of multiple magnets (24a1, 24a2) arranged with their polarization directions in opposite directions. In the fourth aspect, the number of magnets can be freely set, and the number of coils is determined according to the number of magnets, thereby adjusting the rotation speed of the movable part. For example, as the number of magnets increases, the number of coils also increases accordingly, increasing the thrust for rotating the movable part and enabling the movable part to rotate at a higher speed. The fourth aspect is even more effective from the perspective of controlling the rotation speed of the movable part, and even more effective from the perspective of generating thrust for the movable part so as to enable precise control of the rotation of the movable part, for example.

[0073] A fifth aspect of the present invention is any one of the first to fourth aspects, further comprising a drive back yoke (drive magnet back yokes 36a, 36b) arranged along the rotation direction at a position where the other of the movable part and the fixed part overlaps with the drive magnetic field generator. The fifth aspect is even more effective from the viewpoint of preventing fluttering during rotation of the movable part.

[0074] A sixth aspect of the present invention is any of the first to fifth aspects, further comprising a sensor unit for detecting the position of the movable part in the rotation direction. The sixth aspect is even more effective from the viewpoint of detecting the rotation position of the movable part (an anisotropic optical element).

[0075] A seventh aspect of the present invention is the sixth aspect, wherein the sensor unit has a detection magnetic field generator disposed in the rotation direction on one of the movable part and the fixed part, and a Hall element (35) disposed in the rotation direction on the other of the movable part and the fixed part at a position overlapping with the detection magnetic field generator. The seventh aspect is even more effective from the viewpoint of easily and accurately detecting the rotational position of the movable part (an anisotropic optical element).

[0076] An eighth aspect of the present invention is an optical axis adjustment device including the optical axis adjustment actuator according to any one of the first to seventh aspects and an anisotropic optical element held by a movable part. According to the eighth aspect, it is possible to realize an optical axis adjustment device in which fluttering of the optical axis of the anisotropic optical element is suppressed even during high-speed rotation.

[0077] A ninth aspect of the present invention is the eighth aspect, wherein the optical element is a wedge prism. The ninth aspect is even more effective from the viewpoint of high versatility, enabling vibration isolation of a light beam, scanning of a light beam, and the like.

[0078] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

[0079] According to the above-described embodiment, the present invention suppresses fluttering of the rotating anisotropic optical element even when the anisotropic optical element is rotated at high speed, and when applied to optical wireless communication that requires high-speed rotation of the anisotropic optical element, for example, the stability and reliability of the optical wireless communication are improved. The present invention, which has such effects, is expected to bring about groundbreaking progress and development in optical wireless communication technology, and will also contribute to the achievement of, for example, Goal 9 of the Sustainable Development Goals (SDGs) proposed by the United Nations, "Build resilient infrastructure, promote inclusive and sustainable industrialization, and promote innovation and building resilience." [Explanation of symbols]

[0080] 2 Moving parts 3 Fixed part 4 rolling elements 10, 20, 30 Optical axis adjustment actuator 21 Rotating rotor 22a, 22b Drive magnet yoke 23 Sensor magnet yoke 24a, 24b, 24a1, 24a2, 241, 242 Drive magnet 25 Sensor Magnet 31 Outer ring stator 32 rotor spacer 33a, 33b, 331, 332 coils 34 FPC 35 Hall element 36a, 36b Drive magnet back yoke 37 Sensor magnet back yoke 38 Sensor height adjustment stand 39 Main Plate 51, 52, 53 Screws 100 Optical wireless communication device 110 Light beam output unit 120 Communication Optical Systems 121 First optical axis adjustment device 130 Beacon Optics 131 Second optical axis adjustment device 140 Central Processing Unit (CPU) 211 Wedge prism fixing part 212 Movable part groove (first groove) 312 Fixed part groove (second groove) A Arrow indicating the thrust direction of the moving part B Current direction for rotation

Claims

1. A fixed portion; a movable part for holding an anisotropic optical element, the movable part being rotatably attached to the fixed part; a driving magnetic field generator disposed in one of the movable part and the fixed part along the rotation direction of the movable part; a coil arranged along the rotation direction at a position overlapping with the driving magnetic field generation unit in the other of the movable unit and the fixed unit; a first groove formed in the movable portion along a circumferential direction in the rotation direction; a second groove formed in the fixed portion along a circumferential direction in the rotational direction; three or more rolling elements sandwiched between the first groove and the second groove, the first groove and the second groove are opposed to each other in a radial direction in the rotation direction.

2. the first groove is formed around the entire outer periphery of the movable portion, 2. The optical axis adjustment actuator according to claim 1, wherein the second groove is formed around the entire periphery of the outer edge of the fixed portion facing the outer periphery.

3. 2. The optical axis adjustment actuator according to claim 1, wherein the coil is a coreless coil.

4. 2. The optical axis adjustment actuator according to claim 1, wherein the driving magnetic field generating section is made up of a plurality of magnets arranged so that their polarization directions are opposite to each other.

5. 2. The optical axis adjustment actuator according to claim 1, further comprising a drive back yoke arranged along the rotation direction at a position where the other of the movable portion and the fixed portion overlaps with the drive magnetic field generating portion.

6. 2. The optical axis adjustment actuator according to claim 1, further comprising a sensor unit that detects the position of the movable unit in the rotation direction.

7. The sensor unit a detection magnetic field generating unit disposed along the rotation direction on one of the movable unit and the fixed unit; a Hall element disposed in the other of the movable portion and the fixed portion in a position overlapping with the detection magnetic field generation portion along the rotation direction; The optical axis adjustment actuator according to claim 6 , further comprising:

8. an optical axis adjustment actuator according to any one of claims 1 to 7; an anisotropic optical element held by the movable portion.

9. 9. The optical axis adjusting device according to claim 8, wherein the optical element is a wedge prism.

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