Electromagnetic driving system and method based on electromagnetic scanning micromirror

Abstract

The invention relates to the technical field of micro electro mechanical systems, and discloses an electromagnetic driving system and method based on an electromagnetic scanning micromirror, the system comprises the scanning micromirror and a permanent magnet, the scanning micromirror is arranged above the permanent magnet, the scanning micromirror comprises an inner frame and an outer frame which are coaxially arranged, and the outer frame is arranged above the inner frame. A mirror is coaxially arranged in the inner frame, a plurality of coils are arranged at the bottom of the inner frame, the outer frame and the inner frame are rotationally connected, the inner frame and the mirror are rotationally connected, the permanent magnet comprises an outer annular magnet and an inner cylindrical magnet which are coaxially arranged, and the polarities of the adjacent side faces of the outer annular magnet and the inner cylindrical magnet are opposite. And a magnetic field from the N pole to the S pole is formed between the outer annular magnet and the inner cylindrical magnet. According to the invention, the inner cylindrical magnet is added on the basis of the outer annular magnet, so that the distance between the magnets is reduced, the intensity of a magnetic field is increased, and the deflection angle of the scanning micromirror is increased.

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 resonant, and smaller in size and mass.

[0003] MEMS micromirrors are optical MEMS devices that integrate micro-light reflectors and MEMS drivers, and are manufactured using optical MEMS technology. They have the characteristics of large scanning range, small size, and low cost. MEMS micromirrors can be divided into four types according to different driving principles: electrostatic, piezoelectric, electrothermal, and electromagnetic.

[0004] Electromagnetic drive scanning micromirrors are widely used due to their low drive voltage and large deflection angle. At present, there are two types of electromagnetic drive, one is magnetic-magnetic drive and the other is electromagnetic drive. Electromagnetic drive uses the Ampere force generated by a coil with 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 a low voltage and has good linearity. It has gradually become the preferred driving method for large-drive, large-displacement, and large-size micromirrors. However, in existing electromagnetic MEMS micromirrors, the two permanent magnets are mostly placed on both sides of the coil. The magnetic field strength generated by this method is weak and the deflection angle of the mirror is small. 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 electromagnetic drive system based on the electromagnetic scanning micromirror provided by the present invention includes a scanning micromirror and a permanent magnet, wherein the scanning micromirror is arranged above the permanent magnet, and the scanning micromirror includes a coaxially arranged inner frame and an outer frame, a mirror is coaxially arranged inside the inner frame, and a plurality of coils are arranged at the bottom, and the outer frame and the inner frame are rotatably connected, and the permanent magnet includes a coaxially arranged outer annular magnet and an inner cylindrical magnet, and the polarities of the adjacent side surfaces of the outer annular magnet and the inner cylindrical magnet are oppositely arranged 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 axis, the mirror is rotatably connected to the inner frame via an outer torsion axis, and the inner torsion axis and the outer torsion axis are vertically arranged.

[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 an angle of 45 degrees 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 thickness of the inner and outer frames is the same as that of the mirror with the reinforcing ribs.

[0012] Preferably, the inner cylindrical magnet is arranged 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 arranged in opposite directions.

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

[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 mentioned above, including: the mirror is placed on an outer ring magnet, the permanent magnet is rotated 45 degrees and placed, the magnetic flux lines are at an angle of 45 degrees to the torsion axis of the mirror, and the scanning micromirror can be driven to perform scanning movements 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 known from the left-hand rule that if the current frequency is the fast-axis resonance frequency of the scanning micromirror at this time, 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 to perform fast-axis scanning movements. If the current frequency is the slow-axis resonance frequency of the scanning micromirror at this time, 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 to perform slow-axis scanning movements.

[0016] Through the above technical solution, it can be known that compared with the prior art, the permanent magnets of the general electromagnetic driven micromirror are placed on both sides of the micromirror, the permanent magnets are far apart, and the magnetic field strength is 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, compared with the structure without the inner magnet, the structure designed by the present invention has a larger deflection angle as the current increases, 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 drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0018] Figure 1 It is a 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 It is a front schematic diagram of the scanning micromirror of the present invention.

[0020] Figure 3 FIG. 4 is a 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 It is a schematic diagram of the permanent magnet of the present invention.

[0023] Figure 6 It is a top view schematic diagram of the permanent magnet of the present invention.

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

[0025] Figure 8 It is a top view schematic diagram of the electromagnetic drive system based on the electromagnetic scanning micromirror of the present invention.

[0026] Fig. 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 shaft; 6. outer torsion shaft; 7. first half outer annular magnet; 8. second half outer annular 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 be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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 creative work are within the scope of protection of the present invention.

[0032] Please see 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 a plurality of coils 4 are arranged at the bottom, the outer frame 1 and the inner frame 2, and 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 sides of the outer annular magnet and the inner cylindrical magnet are oppositely arranged, 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 vertically arranged; 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, the permanent magnet material is nebium 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, and 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 to make the rotation of the outer frame 2 and the mirror 3 more labor-saving and uniform, 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 thickness of the inner and outer frames 2 is the same as that of the mirror with the reinforcing ribs.

[0039] Specifically, 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, the thickness of the reinforcing rib is h3=h2-h1, and the design of the reinforcing rib can prevent the mirror surface of the mirror 3 from deforming. The inner torsion axis 5 and the outer torsion axis 6 are chamfered to reduce the stress at the connection between the torsion axis and the frame and the mirror. The frame for installing the mirror 3 (i.e., the inner frame 2) is 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 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.

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

[0042] Specifically, Figure 5-7As shown, the permanent magnet is composed 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), 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 method principle of the electromagnetic drive system based on the electromagnetic scanning micromirror provided by the present invention is:

[0044] like Figure 8-9 As shown, the mirror 3 is placed on the outer annular magnet, and the permanent magnet is rotated 45 degrees. The magnetic flux lines form an angle of 45 degrees with the torsion axis of the mirror 3, which can drive the scanning micromirror to perform scanning motion along the two torsion axes (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 known from the left-hand rule that if the current frequency is the resonant frequency of the fast axis (inner torsion axis 5) of the scanning micromirror at this time, 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 to perform fast-axis scanning motion; if the current frequency is the resonant frequency of the slow axis (outer torsion axis 6) of the scanning micromirror at this time, 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 to perform slow-axis scanning motion.

[0045] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be 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 will not be limited to the embodiments shown herein, but rather 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. The scanning micromirror is arranged above the permanent magnet. The scanning micromirror comprises an outer frame (1) and an inner frame (2) which are coaxially arranged. A mirror (3) is coaxially arranged inside the inner frame (2). A plurality of coils (4) are arranged at the bottom. The outer frame (1) and the inner frame (2) are rotatably connected, as are the inner frame (2) and the mirror (3). The permanent magnet comprises an outer annular magnet and an inner cylindrical magnet which are coaxially arranged. The polarities of the adjacent side surfaces of the outer annular magnet and the inner cylindrical magnet are opposite, so that a magnetic field in the direction from the N pole to the S pole is formed between the outer annular magnet and the inner cylindrical magnet.

2. The electromagnetic drive system based on electromagnetic scanning micromirror according to claim 1, characterized in that: The inner frame (2) is rotatably arranged inside the outer frame (1) via an inner torsion shaft (5), the mirror (3) is rotatably connected to the inner frame (2) via an outer torsion shaft (6), and the inner torsion shaft (5) and the outer torsion shaft (6) are arranged vertically.

3. The electromagnetic drive system based on electromagnetic scanning micromirror according to claim 2, 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.

4. The electromagnetic drive system based on electromagnetic scanning micromirror according to claim 2, characterized in that: 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.

5. 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.

6. 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 and outer frames (2) is the same as that of the mirror with the reinforcing ribs.

7. 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).

8. The electromagnetic drive system based on electromagnetic scanning micromirror according to claim 1, characterized in that: The outer ring magnet comprises a first half outer ring magnet (7) and a second half outer ring magnet (8), and the polarities of the first outer ring magnet (7) and the second outer ring magnet (8) are opposite.

9. The electromagnetic drive system based on electromagnetic scanning micromirror according to claim 1, characterized in that: 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.

10. An electromagnetic driving method based on an electromagnetic scanning micromirror, applied to an electromagnetic driving system based on an electromagnetic scanning micromirror as claimed in any one of claims 1 to 9, 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 an angle of 45 degrees with the torsion axis of the mirror (3), and the scanning micromirror can be driven 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 known from the left-hand rule that if the current frequency is the fast axis resonance 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 resonance 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.

Images