An electromagnetic drive system and method based on electromagnetic scanning micromirror

Abstract

The present invention relates to the field of micro-electromechanical systems (MEMS) technology, and discloses an electromagnetic drive system and method based on an electromagnetic scanning micromirror. The system includes a scanning micromirror and a permanent magnet. The scanning micromirror is disposed above the permanent magnet. The scanning micromirror comprises a coaxially arranged inner frame and an outer frame. The inner frame has a mirror coaxially disposed therein and a plurality of coils disposed at its bottom. The outer frame and the inner frame, as well as the inner frame and the mirror, are both rotatably connected. The permanent magnet comprises a coaxially arranged outer ring magnet and an inner cylindrical magnet. The polarities of adjacent side surfaces of the outer ring magnet and the inner cylindrical magnet are opposite, so that a magnetic field is formed between the outer ring magnet and the inner cylindrical magnet in a direction from the north pole to the south pole. By adding the inner cylindrical magnet to the outer ring magnet, the present invention reduces the distance between the magnets, thereby increasing the strength of the magnetic field and improving the deflection angle of the scanning micromirror.

Description

Technical Field

[0001] The present invention relates to the field of micro-electromechanical technology, and more particularly to an electromagnetic driving system and method based on an electromagnetic scanning micromirror. Background Art

[0002] Micro-Electro-Mechanical System (MEMS) is an independent intelligent system that integrates micro sensors, actuators, control circuits, and mechanical components. The size of the internal mechanical structure can reach the micron level or even smaller. The miniaturized size makes the device more sensitive and has a higher resonant frequency, while reducing the volume and mass.

[0003] MEMS micromirrors are optical MEMS devices that integrate a low-light reflector with a MEMS actuator, manufactured using optical MEMS technology. They offer a wide scanning range, compact size, and low cost. MEMS micromirrors can be categorized into four types based on their driving principles: electrostatic, piezoelectric, electrothermal, and electromagnetic.

[0004] Electromagnetically driven scanning micromirrors are widely used due to their low drive voltage and large deflection angle. Currently, there are two types of electromagnetic drive: magnetic-magnetic drive and electromagnetic drive. Electromagnetic drive uses the Ampere force generated by a coil carrying an alternating current and a permanent magnet as the driving force. Although electromagnetic drive requires an external magnetic drive component, it can generate a large driving force at low voltage and has good linearity. It has gradually become the preferred drive method for large-scale micromirrors with large drive, large displacement, and large size. However, existing electromagnetic MEMS micromirrors mostly place two permanent magnets on either side of the coil. This method produces a weak magnetic field and a small deflection angle for the mirror. Summary of the Invention

[0005] In view of this, the present invention provides an electromagnetic drive system and method based on an electromagnetic scanning micromirror, which adopts a new permanent magnet structure. By adding an inner magnet on the basis of an outer magnet, the distance between the magnets is reduced, thereby increasing the magnetic field strength and improving the deflection angle of the scanning micromirror.

[0006] To achieve the above-mentioned purpose, the present invention provides an electromagnetic drive system based on an electromagnetic scanning micromirror, including a scanning micromirror and a permanent magnet. The scanning micromirror is arranged above the permanent magnet. The scanning micromirror includes a coaxially arranged inner frame and an outer frame. The inner frame is coaxially provided with a mirror and a plurality of coils are provided at the bottom. The outer frame and the inner frame, as well as the inner frame and the mirror are rotatably connected. The permanent magnet includes a coaxially arranged outer annular magnet and an inner cylindrical magnet. The polarities of the adjacent side surfaces of the outer annular magnet and the inner cylindrical magnet are arranged in opposite directions so that a magnetic field from the N pole to the S pole is formed between the outer annular magnet and the inner cylindrical magnet.

[0007] Preferably, the inner frame is rotatably arranged inside the outer frame via an inner torsion shaft, the mirror is rotatably connected to the inner frame via an outer torsion shaft, and the inner torsion shaft and the outer torsion shaft are arranged vertically.

[0008] Preferably, the connection between the inner torsion shaft and the inner frame, and the connection between the outer torsion shaft and the mirror are both designed with rounded corners to reduce stress.

[0009] Preferably, the permanent magnet is placed horizontally rotated 45 degrees so that the direction of the magnetic field forms a 45-degree angle with the inner torsion axis and the outer torsion axis. When current is passed through the coil, the coil causes the mirror to move around the inner torsion axis and the outer torsion axis under the action of the Ampere force.

[0010] Preferably, the inner frame is in the shape of a circular ring.

[0011] Preferably, the bottom of the mirror is provided with reinforcing ribs, and the inner and outer frames have the same thickness as the mirror with the reinforcing ribs.

[0012] Preferably, the inner cylindrical magnet is located directly below the mirror and is lower in height than the outer annular magnet, leaving sufficient space for the deflection of the mirror.

[0013] Preferably, the outer annular magnet comprises a first half outer annular magnet and a second half outer annular magnet, and the polarities of the first outer annular magnet and the second outer annular magnet are opposite.

[0014] Preferably, the inner cylindrical magnet comprises a first half inner cylindrical magnet and a second half inner cylindrical magnet, and the polarities of the first half inner cylindrical magnet and the second half inner cylindrical magnet are opposite.

[0015] The present invention also provides an electromagnetic driving method based on an electromagnetic scanning micromirror, which is applied to the electromagnetic driving system based on the electromagnetic scanning micromirror as described above, including: the mirror is placed on an outer ring magnet, the permanent magnet is rotated 45 degrees and placed, the magnetic lines of force are at a 45-degree angle to the torsion axis of the mirror, and the scanning micromirror can be driven to perform scanning motion along the inner torsion axis and the outer torsion axis. Under the action of the magnetic field, when a sinusoidal alternating current of a specific frequency is passed through the coil, it can be seen from the left-hand rule that if the current frequency at this time is the fast-axis resonant frequency of the scanning micromirror, the force directions of points a and c on the inner frame are opposite, and the scanning micromirror can be driven to resonate around the inner torsion axis and perform fast-axis scanning motion. If the current frequency at this time is the slow-axis resonant frequency of the scanning micromirror, the force directions of points b and d on the inner frame are opposite, and the scanning micromirror can be driven to resonate around the outer torsion axis and perform slow-axis scanning motion.

[0016] Through the above technical solution, it can be seen that compared with the prior art, the permanent magnets of the general electromagnetic-driven micromirror are placed on both sides of the micromirror, the distance between the permanent magnets is relatively far, and the magnetic field strength is relatively weak. However, after the inner cylindrical magnet is added to the outer annular magnet, the distance between the magnets is reduced, the magnetic field strength can be effectively increased, and the deflection angle of the mirror is improved; after simulation comparison, when there is no inner cylindrical magnet, the deflection angle of the scanning micromirror in the fast-axis resonance mode is 4.7 degrees, and the slow-axis deflection angle is 2.6 degrees. After adding the inner cylindrical magnet, the deflection angle of the scanning micromirror in the fast-axis resonance mode is 6.6 degrees, and the slow-axis deflection angle is 3.3 degrees, which effectively improves the deflection angle of the scanning micromirror; when studying the relationship between the deflection angle and the current, the structure designed by the present invention is compared with the structure without the inner magnet. As the current increases, the deflection angle of the present invention is larger, so the current linearity of the present invention is also better. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0018] Figure 1 Schematic diagram of the three-dimensional structure of the electromagnetic drive system based on the electromagnetic scanning micromirror of the present invention.

[0019] Figure 2 Schematic diagram of the front view of the scanning micromirror of the present invention.

[0020] Figure 3 Schematic diagram of the back side of the scanning micromirror of the present invention.

[0021] Figure 4 For the present invention Figure 2 Schematic diagram of the A-A' section.

[0022] Figure 5 Schematic diagram of the permanent magnet of the present invention.

[0023] Figure 6 Schematic top view of the permanent magnet of the present invention.

[0024] Figure 7 For the present invention Figure 7 Schematic diagram of the BB' section.

[0025] Figure 8 Schematic top view of the electromagnetic drive system based on the electromagnetic scanning micromirror of the present invention.

[0026] Figure 9 For the present invention Figure 8Schematic diagram of the C-C' section.

[0027] Explanation of reference numerals: 1. outer frame; 2. inner frame; 3. mirror; 4. coil; 5. inner torsion axis; 6. outer torsion axis; 7. first half outer ring magnet; 8. second half outer ring magnet; 9. first half inner cylindrical magnet; 10. second half inner cylindrical magnet;

[0028] r1 is the mirror radius, r2 is the inner radius of the coil (inner frame), r3 is the outer radius of the coil (inner frame), h1 is the torsion axis thickness, h2 is the frame thickness, and h3 is the rib thickness;

[0029] a, b, c, and d are four points on the coil used for force analysis;

[0030] r4 is the radius of the cylindrical magnet, r5 is the inner radius of the annular magnet, h4 is the height of the inner magnet, and h5 is the height of the outer magnet. DETAILED DESCRIPTION

[0031] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0032] Please see the attached Figure 1-9 , which is an electromagnetic driving system based on an electromagnetic scanning micromirror disclosed by the present invention.

[0033] like Figure 1 As shown, the electromagnetic drive system based on the electromagnetic scanning micromirror provided by the present invention includes a scanning micromirror and a permanent magnet, the scanning micromirror includes an outer frame 1, an inner frame 2, a mirror 3, a coil 4, an inner torsion shaft 5, and an outer torsion shaft 6, the permanent magnet includes an outer annular magnet and an inner cylindrical magnet, wherein the outer annular magnet includes a first half outer annular magnet 7 and a second half outer annular magnet 8, and the polarities of the first outer annular magnet 7 and the second outer annular magnet 8 are oppositely arranged, and the inner cylindrical magnet includes a first half inner cylindrical magnet 9 and a second half inner cylindrical magnet 10, and the polarities of the first half inner cylindrical magnet 9 and the second half inner cylindrical magnet 10 are oppositely arranged.

[0034] The scanning micromirror is arranged above the permanent magnet, a mirror 3 is coaxially arranged inside the inner frame 2, and several coils 4 are arranged at the bottom. The outer frame 1 and the inner frame 2, as well as the inner frame 2 and the mirror 3 are rotationally connected. The outer annular magnet and the inner cylindrical magnet are coaxially arranged, and the polarities of the adjacent side surfaces of the outer annular magnet and the inner cylindrical magnet are opposite, so that a magnetic field from the N pole to the S pole is formed between the outer annular magnet and the inner cylindrical magnet.

[0035] Specifically, the inner frame 2 is rotatably arranged inside the outer frame 1 through the inner torsion shaft 5, the mirror 3 is rotatably connected to the inner frame 2 through the outer torsion shaft 6, and the inner torsion shaft 5 and the outer torsion shaft 6 are arranged vertically; the first outer ring magnet 7 and the first half inner cylindrical magnet 9 are S poles, and the second outer ring magnet 8 and the second half inner cylindrical magnet 10 are N poles. Similarly, the S pole and the N pole can also be set in reverse, which is not specifically limited here.

[0036] It should be noted that the scanning micromirror is based on silicon material, the coil 4 attached to the back of the inner frame 2 is made of metal, and the permanent magnet material is nebulizer iron boron. The actual number of turns of the coil can be 25 or a suitable value can be selected according to the specific situation. No specific limitation is made here.

[0037] In order to further optimize the above solution, the connection between the inner torsion shaft 5 and the inner frame 2, and the connection between the outer torsion shaft 6 and the mirror 3 are both chamfered to reduce stress. The inner frame 2 is in a circular shape, so that the outer frame 2 and the mirror 3 can be rotated more labor-saving and evenly stressed, thereby improving portability and stability.

[0038] In order to further optimize the above solution, a reinforcing rib is provided at the bottom of the mirror 3 to prevent the mirror surface from deforming and further improve the stability of the mirror 3. Figure 3 The four shaded parts represent the reinforcing ribs at the bottom of the mirror, and the inner and outer frames 2 have the same thickness as the mirror with the reinforcing ribs.

[0039] Specifically, such as Figure 2-4 As shown, the radius of the mirror is r1, the thickness of the inner torsion axis 5 and the outer torsion axis 6 is h1, the thickness of the frame is h2, and the thickness of the reinforcing rib is h3 = h2 - h1. The design of the reinforcing rib can prevent the mirror surface of the mirror 3 from being deformed. The inner torsion axis 5 and the outer torsion axis 6 are chamfered to reduce the stress at the connection between the torsion axis, the frame and the mirror. The frame for mounting the mirror 3 (i.e., the inner frame 2) is in the shape of a circular ring with an inner radius of r2 and an outer radius of r3.

[0040] It should be noted that the permanent magnet is placed horizontally rotated 45 degrees so that the direction of the magnetic field forms a 45-degree angle with the inner torsion axis 5 and the outer torsion axis 6. When current is passed through the coil 4, the coil 4 causes the mirror 3 to move around the inner torsion axis 5 and the outer torsion axis 6 under the action of the Ampere force.

[0041] It should be noted that the inner cylindrical magnet is located directly below the mirror 3 and is lower in height than the outer annular magnet, leaving enough space for the deflection of the mirror 3 .

[0042] Specifically, such as Figure 5-7As shown, the permanent magnet consists of an outer ring magnet and an inner cylindrical magnet, wherein the radius r4 of the cylindrical magnet is larger than the radius r1 of the mirror 3 and smaller than the inner radius r2 of the coil 4 (i.e., the inner frame 2), and the inner radius r5 of the outer ring magnet is larger than the outer radius r3 of the coil 4, i.e., the coil 4 is just between the two magnets (the outer ring magnet and the inner cylindrical magnet), and the height h4 of the inner cylindrical magnet is smaller than the height h5 of the outer ring magnet, leaving enough space for the movement of the mirror 3.

[0043] The principle of the electromagnetic drive system based on the electromagnetic scanning micromirror provided by the present invention is as follows:

[0044] like Figure 8-9 As shown, the mirror 3 is placed on the outer ring magnet, and the permanent magnet is rotated 45 degrees and placed. The magnetic flux lines form a 45-degree angle with the torsion axis of the mirror 3, which can drive the scanning micromirror to perform scanning motion along the two torsion axes (inner torsion axis 5 and outer torsion axis 6). Under the action of the magnetic field, when a sinusoidal alternating current of a specific frequency is passed through the coil 4, it can be seen from the left-hand rule that if the current frequency at this time is the resonant frequency of the fast axis (inner torsion axis 5) of the scanning micromirror, the force directions of points a and c are opposite, and the scanning micromirror can be driven to resonate around the inner torsion axis 5 and perform fast-axis scanning motion; if the current frequency at this time is the resonant frequency of the slow axis (outer torsion axis 6) of the scanning micromirror, the force directions of points b and d are opposite, and the scanning micromirror can be driven to resonate around the outer torsion axis 6 and perform slow-axis scanning motion.

[0045] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An electromagnetic drive system based on an electromagnetic scanning micromirror, characterized in that: The invention comprises a scanning micromirror and a permanent magnet, wherein the scanning micromirror is arranged above the permanent magnet, and the scanning micromirror comprises a coaxially arranged outer frame (1) and an inner frame (2), wherein a mirror (3) is coaxially arranged inside the inner frame (2), and a plurality of coils (4) are arranged at the bottom, and the outer frame (1) and the inner frame (2) are rotatably connected, and the inner frame (2) and the mirror (3) are rotatably connected, and the permanent magnet comprises a coaxially arranged outer annular magnet and an inner cylindrical magnet, wherein the polarities of adjacent side surfaces of the outer annular magnet and the inner cylindrical magnet are oppositely arranged, so that a magnetic field in a direction from the N pole to the S pole is formed between the outer annular magnet and the inner cylindrical magnet; The outer annular magnet comprises a first half outer annular magnet (7) and a second half outer annular magnet (8), wherein the polarities of the first half outer annular magnet (7) and the second half outer annular magnet (8) are opposite; The inner cylindrical magnet comprises a first half inner cylindrical magnet (9) and a second half inner cylindrical magnet (10), wherein the first half inner cylindrical magnet (9) and the second half inner cylindrical magnet (10) are arranged with opposite polarities; The inner frame (2) is rotatably arranged inside the outer frame (1) via an inner torsion shaft (5), and the mirror (3) is rotatably connected to the inner frame (2) via an outer torsion shaft (6), wherein the inner torsion shaft (5) and the outer torsion shaft (6) are arranged vertically; The permanent magnet is placed horizontally rotated 45 degrees so that the direction of the magnetic field forms an angle of 45 degrees with the inner torsion axis (5) and the outer torsion axis (6). When current is passed through the coil (4), the coil (4) causes the mirror (3) to move around the inner torsion axis (5) and the outer torsion axis (6) under the action of the Ampere force.

2. The electromagnetic drive system based on electromagnetic scanning micromirror according to claim 1, characterized in that: The connection between the inner torsion shaft (5) and the inner frame (2), and the connection between the outer torsion shaft (6) and the mirror (3) are both designed with rounded corners to reduce stress.

3. The electromagnetic drive system based on electromagnetic scanning micromirror according to claim 1, characterized in that: The inner frame (2) is in the shape of a circular ring.

4. The electromagnetic drive system based on electromagnetic scanning micromirror according to claim 1, characterized in that: The bottom of the mirror (3) is provided with reinforcing ribs, and the thickness of the inner frame (2) is the same as that of the mirror with the reinforcing ribs.

5. The electromagnetic drive system based on electromagnetic scanning micromirror according to claim 1, characterized in that: The inner cylindrical magnet is arranged directly below the mirror (3) and is lower in height than the outer annular magnet, leaving sufficient space for the deflection of the mirror (3).

6. An electromagnetic driving method based on an electromagnetic scanning micromirror, applied to the electromagnetic driving system based on an electromagnetic scanning micromirror according to any one of claims 1 to 5, characterized in that: include: The mirror (3) is placed on the outer annular magnet, and the permanent magnet is rotated 45 degrees and placed. The magnetic flux lines form a 45-degree angle with the torsion axis of the mirror (3), which can drive the scanning micromirror to perform scanning motion along the inner torsion axis (5) and the outer torsion axis (6). Under the action of the magnetic field, when a sinusoidal alternating current of a specific frequency is passed through the coil (4), it can be seen from the left-hand rule that if the current frequency is the fast axis resonant frequency of the scanning micromirror at this time, the force directions of point a and point c on the inner frame (2) are opposite, and the scanning micromirror can be driven to resonate around the inner torsion axis (5) to perform fast axis scanning motion. If the current frequency is the slow axis resonant frequency of the scanning micromirror at this time, the force directions of point b and point d on the inner frame (2) are opposite, and the scanning micromirror can be driven to resonate around the outer torsion axis (6) to perform slow axis scanning motion.

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