Multi-fold torsion beam and non-linearly attenuated MEMS torsion mirror including the same

Abstract

The present invention belongs to the field of micro-optoelectromechanics, and particularly relates to a MEMS torsion mirror, especially a multi-fold torsion beam and a MEMS torsion mirror with reduced non-linearity including the multi-fold torsion beam. It solves problems such as the frequency range and angle limitation caused by non-linearity and the difficulty in angle control. The multi-fold torsion beam includes three groups of torsion beams, six groups of cross beams and two groups of transition beams. By arranging multiple groups of cross beams, the torsion centers of each section of the torsion beam coincide with their respective geometric centers, weakening the motion non-linearity of the MEMS torsion mirror caused by the large difference in torsional deformation at each position of the multi-fold torsion beam. Combined with a driver that can provide linear torque, a MEMS torsion mirror with reduced non-linearity is realized. When using the multi-fold torsion beam, it does not show obvious non-linear characteristics, that is, the resonant motion does not show the phenomenon of unstable regions and large differences in bidirectional frequency sweeping, and the static rotation does not show a non-linear relationship between the driving force and the rotation angle, improving the performance of the MEMS torsion mirror.

Description

Technical Field

[0001] The present invention belongs to the field of micro-optoelectromechanics, and particularly relates to a MEMS torsion mirror, and more particularly to a multi-fold torsion beam and a MEMS torsion mirror with reduced non-linearity including the multi-fold torsion beam. Background Art

[0002] Compared with traditional mechanical optical scanning devices, MEMS torsion mirrors have the advantages of small size, light weight, easy integration, fast response, and long service life, and are increasingly used in fields such as laser projection, lidar, and 3D imaging. In most cases, the MEMS torsion mirror directly determines the performance of the entire scanning device. Therefore, improving the performance of the MEMS torsion mirror has become the focus of attention of technicians.

[0003] In the structural design of a MEMS torsion mirror, a torsion beam is often selected as an elastic element to provide a restoring force. During operation, an external driving force (which can be generated by common driving methods such as piezoelectric driving, electrostatic driving, electromagnetic driving, thermoelectric driving, and magnetostrictive driving) applies a torque to the torsion beam, causing it to undergo elastic torsional deformation to generate a restoring force, and the combined action of the driving force, damping force, and restoring force determines the motion state of the torsion mirror. The non-linear relationship between the restoring force and the rotation angle greatly affects the performance of the torsion mirror, resulting in phenomena such as the appearance of an unstable region in the resonant motion and a large difference in the bidirectional swept-frequency resonance frequencies, which limits the frequency range and rotation angle of the motion. At the same time, the non-linear relationship between the driving force and the rotation angle that appears in the static rotation increases the difficulty of rotation angle control.

[0004] The patent document (CN102540459B) discloses a method of providing slits on the torsion beam, which solves the problem of displacement non-linearity caused by different deformation states of the torsion beam due to different distances from the torsion center axis, and achieves the purpose of reducing the occurrence of non-linear resonance under high-frequency driving. However, the torsion beam adopted in this document is a straight beam, and the structure is relatively simple. However, in different designs, considering factors such as chip size and vibration modes, it is often necessary to design the torsion beam as a multi-fold torsion beam or a serpentine beam (such as the patent document (CN101655602A)). The multi-fold torsion beam has a complex shape. During the torsion process, the outer beam is farther from the torsion center axis, and the torsional deformation differences at different positions of the torsion beam are greater. Therefore, the non-linearity presented is stronger.

[0005] Therefore, it is expected to realize a MEMS torsion mirror with reduced non-linearity by designing a multi-fold torsion beam with a special shape. Summary of the Invention

[0006] The object of the present invention is to provide a multi-fold torsion beam and a non-linearity-reduced MEMS torsion mirror including the multi-fold torsion beam. By designing a multi-fold torsion beam with a special shape, the non-linearity of the MEMS torsion mirror is reduced, the resonant motion and static motion performance of the torsion mirror are improved, and problems such as the frequency range and rotation angle limitation caused by non-linearity and the difficulty in angle control are solved.

[0007] The inventive concept of the present invention is as follows:

[0008] In the present invention, by arranging multi-fold cross beams, the torsion centers of each section of the torsion beam coincide with their respective geometric centers, weakening the motion non-linearity of the MEMS torsion mirror caused by the large difference in torsional deformation at each position of the multi-fold torsion beam. Combined with a driver that can provide linear torque, a non-linearity-reduced MEMS torsion mirror is realized. When using a multi-fold torsion beam, it does not exhibit obvious non-linear characteristics, that is, there are no unstable regions and large differences in bidirectional sweep frequencies in the resonant motion, and there is no non-linear relationship between the driving force and the rotation angle in the static rotation, improving the performance of the MEMS torsion mirror.

[0009] It should be emphasized that although the multi-fold torsion beam disclosed in the present invention has some similarities in shape with the torsion beam disclosed in the Chinese patent with the publication number CN109633893A, the special shape of the multi-fold torsion beam in the present invention (the second cross beam and the fifth cross beam are slender beams, ensuring a certain deformation during torsion, and the deformation can adjust the torsional deformation centers of the first torsion beam and the third torsion beam from the geometric center of the second torsion beam to their respective geometric centers) can achieve the reduction of non-linearity, which is not described in the patent CN109633893A, and this is also not possessed by the previously disclosed multi-fold torsion beams. Ordinary multi-fold torsion beams can only achieve the purpose of reducing the overall size of the torsion beam, increasing the torsional resonance frequency without increasing stress, and have strong non-linear characteristics.

[0010] The technical solution of the present invention is to provide a multi-fold torsion beam, which is special in that it includes three groups of torsion beams, six groups of cross beams and two groups of transition beams;

[0011] The above three groups of torsion beams are parallel to each other, extend in the y direction, and are arranged in the x direction, and are respectively the first torsion beam, the second torsion beam and the third torsion beam. The first torsion beam and the third torsion beam are arranged on both sides of the second torsion beam and are symmetric about the second torsion beam;

[0012] The six groups of cross beams all extend in the x direction and are respectively the first cross beam, the second cross beam, the third cross beam, the fourth cross beam, the fifth cross beam and the sixth cross beam; the first cross beam and the fourth cross beam are arranged on both sides of the second torsion beam and are symmetric about the second torsion beam; the second cross beam and the fifth cross beam are arranged on both sides of the second torsion beam and are symmetric about the second torsion beam; the third cross beam and the sixth cross beam are arranged on both sides of the second torsion beam and are symmetric about the second torsion beam;

[0013] The two groups of transition beams are the first transition beam and the second transition beam respectively, extending along the y direction, arranged on both sides of the second torsion beam, and symmetric about the second torsion beam;

[0014] The first cross beam, the first torsion beam, the second cross beam, the first transition beam and the third cross beam are connected end to end in sequence;

[0015] The fourth cross beam, the third torsion beam, the fifth cross beam, the second transition beam and the sixth cross beam are connected end to end in sequence;

[0016] After the third cross beam and the sixth cross beam are connected, they are connected to one end of the second torsion beam, and the other end of the second torsion beam is used to connect to the MEMS torsion mirror; the free ends of the first cross beam and the fourth cross beam are far away from the second torsion beam and are used to connect to the fixed frame of the MEMS torsion mirror;

[0017] Arc chamfers are provided at the connection parts of each beam;

[0018] The second cross beam and the fifth cross beam are slender beams, ensuring a certain deformation during the torsion process, and the deformation can adjust the torsion deformation centers of the first torsion beam and the third torsion beam from the geometric center of the second torsion beam to their respective geometric centers.

[0019] Further, W 2.6 > W 2.21 > W 2.6 / 2 ≈ W 2.51 > W 2.11 ≈ W 2.31 ; L 2.11 ≈ L 2.41 < L 2.31 / 2.5; where, W 2.6 is the width of the second torsion beam, W 2.21 is the width of the first torsion beam, W 2.51 is the width of the third cross beam, W 2.11 is the width of the first cross beam, W 2.31 is the width of the second cross beam, L 2.11 is the length of the first cross beam, L 2.41 is the length of the first transition beam, L 2.31 is the length of the second cross beam.

[0020] Further, W 2.6 ≈ 1.4W 2.11 ≈ 2W 2.51 ≈ 4W 2.11 ≈ 4W 2.31 ; L 2.41 ≈ L 2.31 / 3.

[0021] The present invention also provides a MEMS torsion mirror with non-linear weakening, which includes a driving structure, a movable structure and a fixed frame. The movable structure includes a mirror and a torsion beam. The special feature lies in:

[0022] The above-mentioned torsion beam is two of the above multi-fold torsion beams;

[0023] The two above-mentioned multi-fold torsion beams are symmetrically arranged on both sides of the mirror;

[0024] For the two multi-fold torsion beams, the free ends of the first cross beam and the fourth cross beam are both connected to the fixed frame, and the driving structure is used to drive the two multi-fold torsion beams to drive the mirror to move linearly.

[0025] Further, the above-mentioned driving structure includes a permanent magnet base, a permanent magnet and an external driving magnetic circuit; the permanent magnet base is arranged at the center position on the back of the mirror, and a groove adapted to the shape of the permanent magnet is opened in the center of the permanent magnet base; the permanent magnet is embedded in the groove of the permanent magnet base;

[0026] For the two multi-fold torsion beams, the other ends of the second torsion beams are respectively connected to the opposite sides of the permanent magnet base;

[0027] The external driving magnetic circuit applies an electromagnetic force to the permanent magnet, and through the permanent magnet, a rotational torque acts on the two multi-fold torsion beams to drive the mirror to move linearly to achieve optical scanning.

[0028] Further, the above-mentioned mirror is a rectangular mirror; it also includes a reinforcing rib arranged on the back of the mirror, the reinforcing rib extends outward along the length direction of the mirror surface, and the permanent magnet base is integrally formed.

[0029] Further, for the two multi-fold torsion beams, the other ends of the second torsion beams are respectively connected to the opposite sides of the mirror; the above-mentioned driving structure includes moving comb teeth symmetrically arranged on the other two sides of the mirror, and stationary comb teeth corresponding to the moving comb teeth, and the moving comb teeth and the stationary comb teeth form a vertical interleaved comb tooth driver;

[0030] Apply different voltages to the moving and stationary comb teeth on one side of the target torsion direction. The moving comb teeth are affected by the electrostatic force and rotate towards the stationary comb teeth, driving the mirror to move linearly to achieve optical scanning.

[0031] Further, the MEMS torsion mirror also includes a mirror anchor point and a mirror support pillar; the mirror support pillar is arranged at the center of the mirror anchor point, and the mirror is fixed on the mirror support pillar; for the two multi-fold torsion beams, the other ends of the second torsion beams are respectively connected to the opposite sides of the mirror anchor point; the above-mentioned driving structure includes moving comb teeth symmetrically arranged on the other two sides of the mirror anchor point, and stationary comb teeth corresponding to the moving comb teeth, and the moving comb teeth and the stationary comb teeth form a vertical interleaved comb tooth driver.

[0032] Furthermore, the other ends of the second torsion beams in the two multi-fold torsion beams are respectively connected to the opposite sides of the mirror; the driving structure includes four groups of piezoelectric actuators symmetrically arranged on the other two sides of the mirror; the four groups of piezoelectric actuators are connected to the fixed frame of the MEMS torsion mirror.

[0033] The beneficial effects of the present invention are as follows:

[0034] 1. The present invention designs a multi-fold torsion beam with a special shape, which weakens the non-linearity of the movement of the MEMS torsion mirror and realizes the linear movement of the torsion mirror;

[0035] Compared with the ordinary multi-fold torsion beam, the present invention adds a second cross beam, a first transition beam, a fifth cross beam and a second transition beam, and the shapes of the third cross beam and the sixth cross beam change significantly, and the length becomes longer; the added second cross beam and fifth cross beam are slender beams, which can undergo a certain deformation during the torsion process. The deformation can adjust the torsion deformation centers of the outer torsion beams, the first torsion beam and the third torsion beam, from the geometric center of the second torsion beam to their respective geometric centers, reduce the torsion deformation difference between the three torsion beams, and further weaken the non-linear movement of the MEMS torsion mirror, realize the linear movement of the torsion mirror, and improve the performance of the MEMS torsion mirror.

[0036] 2. The present invention designs a multi-fold torsion beam with a special shape, which realizes the linear movement of the torsion mirror, thus eliminating the unstable region of the resonant movement caused by non-linearity and increasing the frequency range and rotation angle.

[0037] 3. The present invention designs a multi-fold torsion beam with a special shape, which realizes the linear movement of the torsion mirror, thus eliminating the non-linear relationship between the driving force of static rotation and the rotation angle and reducing the difficulty of angle control.

[0038] 4. The space occupied by the multi-fold torsion beam of the present invention is smaller than that of the straight beam, which reduces the overall size of the chip. More chips can be fabricated on a single silicon wafer, reducing the manufacturing cost of the torsion mirror. Description of the Drawings

[0039] Fig. 1(A) is a front view schematic diagram of the electromagnetic drive non-linearity weakened torsion mirror in Embodiment 1;

[0040] Fig. 1(B) is a back view schematic diagram of the electromagnetic drive non-linearity weakened torsion mirror in Embodiment 1;

[0041] In the figure: 1 - mirror, 2 - first multi-fold torsion beam, 3 - second multi-fold torsion beam, 4 - reinforcing rib, 5 - permanent magnet base, 6 - permanent magnet;

[0042] 2.11 - First cross beam, 2.21 - First torsion beam, 2.31 - Second cross beam, 2.41 - First transition beam, 2.51 - Third cross beam, 2.6 - Second torsion beam, 2.12 - Fourth cross beam, 2.22 - Third torsion beam, 2.32 - Fifth cross beam, 2.42 - Second transition beam, 2.52 - Sixth cross beam;

[0043] Figure 2 It is a partial schematic diagram of the electromagnetic - driven non - linear - attenuation torsion mirror with multi - fold torsion beam in Embodiment 1;

[0044] Figure 3 It is a schematic diagram of an electromagnetic - driven torsion mirror using a common multi - fold torsion beam;

[0045] In the figure: 1 - Mirror, 2 - First multi - fold torsion beam, 3 - Second multi - fold torsion beam;

[0046] 2.11 - First cross beam, 2.21 - First torsion beam, 2.51 - Third cross beam, 2.6 - Second torsion beam, 2.12 - Fourth cross beam, 2.22 - Third torsion beam, 2.52 - Sixth cross beam;

[0047] Figure 4(A) is a schematic diagram of the torsion center of a common multi - fold torsion beam;

[0048] Figure 4(B) is a schematic diagram of the torsion center of the multi - fold torsion beam in Embodiment 1;

[0049] Figure 5 It is the amplitude - frequency curve graph of an electromagnetic - driven torsion mirror using a common multi - fold torsion beam;

[0050] Figure 6 It is the amplitude - frequency curve graph of the electromagnetic - driven non - linear - attenuation torsion mirror in Embodiment 1;

[0051] Figure 7 It is the torque - rotation angle relationship graph of linear and non - linear torsion mirrors;

[0052] Figure 8 It is a schematic diagram of an electrostatic - driven non - linear - attenuation torsion mirror in Embodiment 2;

[0053] In the figure: 8 - Mirror, 7A - First multi - fold torsion beam, 7B - Second multi - fold torsion beam, 9A - First moving comb tooth, 9B - Second moving comb tooth, 10A - First static comb tooth, 10B - Second static comb tooth;

[0054] Figure 9 It is a schematic diagram of an electrostatic - driven non - linear - attenuation torsion mirror in Embodiment 3;

[0055] In the figure: 11A - the first multi-fold torsion beam, 11B - the second multi-fold torsion beam, 12 - mirror anchor point, 12A - the first moving comb tooth, 12B - the second moving comb tooth, 13A - the first stationary comb tooth, 13B - the second stationary comb tooth, 14 - mirror, 15 - mirror support pillar;

[0056] Figure 10 is a schematic diagram of a piezoelectric-driven non-linear attenuation torsion mirror in Embodiment 4.

[0057] In the figure: 16A - the first multi-fold torsion beam, 16B - the second multi-fold torsion beam, 17 - mirror, 18A - the first piezoelectric actuator, 18B - the second piezoelectric actuator, 18C - the third piezoelectric actuator, 18D - the fourth piezoelectric actuator, 18A.1 - support beam, 18A.21 - the first piezoelectric layer, 18A.22 - the second piezoelectric layer, 18A.23 - the third piezoelectric layer. Detailed implementation manners

[0058] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0059] Embodiment 1

[0060] Figures 1(A) and 1(B) show the structure of the non-linear attenuation torsion mirror of Embodiment 1. In this embodiment, an electromagnetic drive method is used to generate a torsional moment. Figure 1(A) is a front schematic diagram of the electromagnetic-driven non-linear attenuation torsion mirror, and Figure 1(B) is a back schematic diagram of the electromagnetic-driven non-linear attenuation torsion mirror.

[0061] As shown in Figures 1(A) and (B), the electromagnetic-driven non-linear attenuation MEMS torsion mirror includes a mirror 1, a first multi-fold torsion beam 2, a second multi-fold torsion beam 3, a reinforcing rib 4, a permanent magnet base 5 and a permanent magnet 6. In addition, it also includes a light-reflecting material coated on the surface of the mirror 1, a torsion mirror fixing frame and an external drive magnetic circuit (not shown in the figure). In this embodiment, the mirror 1 is rectangular in shape. The reinforcing rib 4 is arranged on the back of the mirror 1 and extends outward along the length direction of the mirror surface to suppress the deformation of the mirror 1 during movement. The permanent magnet base 5 is integrally formed with the reinforcing rib 4 and is arranged at the center position on the back of the mirror. A groove is opened in the center for positioning and installing the permanent magnet 6, which is matched with the outer side of the permanent magnet 6. The permanent magnet 6 is embedded in the groove of the permanent magnet base 5.

[0062] The first multi-fold torsion beam 2 and the second multi-fold torsion beam 3 have the same structure and are symmetrically arranged on both sides of the mirror.

[0063] The first multi-fold torsion beam 2 includes three sets of torsion beams, six sets of cross beams and two sets of transition beams; the three sets of torsion beams are parallel to each other, extend in the y direction, and are arranged in the x direction, and are respectively the first torsion beam 2.21, the second torsion beam 2.6 and the third torsion beam 2.22. The first torsion beam 2.21 and the third torsion beam 2.22 are arranged on both sides of the second torsion beam 2.6 and are symmetric about the second torsion beam 2.6; the six sets of cross beams all extend in the x direction and are respectively the first cross beam 2.11, the second cross beam 2.31, the third cross beam 2.51, the fourth cross beam 2.12, the fifth cross beam 2.32 and the sixth cross beam 2.52; the first cross beam 2.11 and the fourth cross beam 2.12 are arranged on both sides of the second torsion beam 2.6 and are symmetric about the second torsion beam 2.6; the second cross beam 2.31 and the fifth cross beam 2.32 are arranged on both sides of the second torsion beam 2.6 and are symmetric about the second torsion beam 2.6; the third cross beam 2.51 and the sixth cross beam 2.52 are arranged on both sides of the second torsion beam 2.6 and are symmetric about the second torsion beam 2.6; the two sets of transition beams are respectively the first transition beam 2.41 and the second transition beam 2.42, extend in the y direction, are arranged on both sides of the second torsion beam 2.6 and are symmetric about the second torsion beam 2.6; the first cross beam 2.11, the first torsion beam 2.21, the second cross beam 2.31, the first transition beam 2.41 and the third cross beam 2.51 are connected end to end in sequence; the fourth cross beam 2.12, the third torsion beam 2.22, the fifth cross beam 2.32, the second transition beam 2.42 and the sixth cross beam 2.52 are connected end to end in sequence; after the third cross beam 2.51 and the sixth cross beam 2.52 are connected, they are connected to one end of the second torsion beam 2.6, and the other end of the second torsion beam 2.6 is connected to the permanent magnet base; the free ends of the first cross beam 2.11 and the fourth cross beam 2.12 are far away from the second torsion beam 2.6 and are connected to the fixed frame of the MEMS torsion mirror. The fixed frame is used to support the movable part of the torsion mirror (including the mirror 1, the first multi-fold torsion beam 2, the second multi-fold torsion beam 3, the reinforcing rib 4, the permanent magnet base 5 and the permanent magnet 6). The connection of multiple beams is provided with arc chamfers to eliminate stress concentration, reduce the risk of damage to the multi-fold torsion beam, and extend the service life of the torsion mirror. The positions and dimensions between the second torsion beam 2.6, the first torsion beam 2.21 and the third torsion beam 2.22 in the multi-fold torsion beam are reasonably set so that the stress distribution in the three torsion beams is uniform during the torsion process, reducing the possibility of damage.

[0064] The working principle of the non-linear weakening torsion mirror in Embodiment 1 is as follows: The external driving magnetic circuit applies electromagnetic force to the permanent magnet 6, and through the permanent magnet 6, the rotational torque acts on the first multi-fold torsion beam 2 and the second multi-fold torsion beam 3. The first multi-fold torsion beam 2 and the second multi-fold torsion beam 3 undergo torsional deformation, driving the mirror 1 to rotate to achieve optical scanning. The generation of a linear rotational torque by the electromagnetic driving force is the basis for realizing the linear motion of the torsion mirror.

[0065] Figure 2Schematic diagram of a partial electromagnetic-driven non-linear attenuation torsion mirror with a multi-fold torsion beam in Embodiment 1. The dimensions of each component beam have the following relationships: W 2.6 >W 2.21 >W 2.6 / 2≈W 2.51 >W 2.11 ≈W 2.31 , L 2.11 ≈L 2.41 <L 2.31 / 2.5. Wherein, W 2.6 is the width of the second torsion beam 2.6, W 2.21 is the width of the first torsion beam 2.21, W 2.51 is the width of the third cross beam 2.51, W 2.11 is the width of the first cross beam 2.11, W 2.31 is the width of the second cross beam 2.31, L 2.11 is the length of the first cross beam 2.11, L 2.41 is the length of the first transition beam 2.41, L 2.31 is the length of the second cross beam 2.31. More preferably, W 2.6 ≈1.4W 2.11 ≈2W 2.51 ≈4W 2.11 ≈4W 2.31 ; L 2.41 ≈L 2.31 / 3.

[0066] Figure 3 represents an electromagnetic-driven torsion mirror with a common multi-fold torsion beam. The first multi-fold torsion beam 2 of this torsion mirror includes a first cross beam 2.11, a first torsion beam 2.21, a third cross beam 2.51, a second torsion beam 2.6, and a fourth cross beam 2.12, a third torsion beam 2.22, and a sixth cross beam 2.52 symmetrically arranged with respect to the second torsion beam 2.6. When this torsion mirror twists, the torsion center positions of the three torsion beams are shown in Fig. 4(A). The torsion centers of the second torsion beam 2.6 on the inner side and the first torsion beam 2.21 and the third torsion beam 2.22 on the outer side are both the geometric center 2.6C of the second torsion beam 2.6. The first torsion beam 2.21 and the third torsion beam 2.22 rotate around 2.6C, resulting in relatively large differences in their torsional deformations compared to the second torsion beam 2.6. Therefore, it has strong non-linearity.

[0067] Compared with Figure 3In the ordinary multi-fold torsion beam, the multi-fold torsion beam in Embodiment 1 adds a second cross beam 2.31, a first transition beam 2.41, a fifth cross beam 2.32 and a second transition beam 2.42, and the shapes of the third cross beam 2.51 and the sixth cross beam 2.52 change significantly, with their lengths becoming longer. The added second cross beam 2.31 and fifth cross beam 2.32 are slender beams that can undergo certain deformation during torsion. The deformation can adjust the torsion centers of the first torsion beam 2.21 and the third torsion beam 2.22 of the outer torsion beam from the geometric center of the second torsion beam to their respective geometric centers 2.21C, 2.22C and 2.6C (as shown in Figure 4(B)), reducing the torsion deformation difference between the three torsion beams and weakening the torsional mirror nonlinearity.

[0068] Figure 5 It represents the amplitude-frequency curve of the electromagnetic-driven torsion mirror with an ordinary multi-fold torsion beam. Due to the strong nonlinearity, there is an unstable region where the ascending-frequency scanning amplitude-frequency curve does not coincide with the descending-frequency scanning. The torsion mirror cannot operate at the resonance point, and the unstable region limits the working frequency range and rotation angle of the torsion mirror.

[0069] Figure 6 It represents the amplitude-frequency curve of the torsion mirror with weakened nonlinearity in Embodiment 1. After using the multi-fold torsion beam with a special shape, the nonlinearity is significantly weakened. The ascending-frequency scanning amplitude-frequency curve coincides with the descending-frequency scanning, and there is no unstable region. The torsion mirror can resonate at the resonance point to achieve the maximum rotation angle, and the working frequency and rotation angle are not restricted.

[0070] Figure 7 It is the torque-rotation angle relationship diagram of the linear and nonlinear torsion mirrors. The linear torsion mirror is the torsion mirror with weakened nonlinearity in Embodiment 1, and the nonlinear torsion mirror is the torsion mirror with an ordinary multi-fold torsion beam. The relationship between the torque and the rotation angle of the linear torsion mirror is linear, while the relationship between the torque and the rotation angle of the nonlinear torsion mirror shows obvious nonlinearity. Based on the simple linear relationship between the torque and the rotation angle of the linear torsion mirror, the corresponding rotation angle can be easily obtained according to the torque, and it is easier to achieve high-precision control of the rotation angle.

[0071] Embodiment 2

[0072] Figure 8 It represents the structure of the torsion mirror with weakened nonlinearity in Embodiment 2. In this embodiment, an electrostatic drive method is used to provide the torsion torque.

[0073] Such as Figure 8As shown in the figure, in this embodiment, the electrostatically actuated non-linear attenuation torsion mirror includes a mirror 8, a first multi-fold torsion beam 7A and a second multi-fold torsion beam 7B connected to the two opposite sides of the mirror 8 (the two opposite sides of the mirror 8 are respectively connected to the other ends of the second torsion beams in the first multi-fold torsion beam 7A and the second multi-fold torsion beam 7B), a first moving comb tooth 9A and a second moving comb tooth 9B symmetrically arranged on the other two sides of the mirror 8, and a first stationary comb tooth 10A and a second stationary comb tooth 10B corresponding to the moving comb teeth. The moving comb teeth and the stationary comb teeth form a vertically staggered comb tooth driver. In addition, it also includes a light reflection material coated on the surface of the mirror 8 and a torsion mirror fixing frame (not shown in the figure). The fixing frame fixes the movable part of the entire torsion mirror (including the mirror 8, the first multi-fold torsion beam 7A, the second multi-fold torsion beam 7B, the first moving comb tooth 9A and the second moving comb tooth 9B). The free ends of the first cross beam and the fourth cross beam in the first multi-fold torsion beam 7A and the second multi-fold torsion beam 7B are both connected to the fixing frame of the torsion mirror.

[0074] The working principle of the electrostatically actuated non-linear attenuation torsion mirror in Embodiment 2 is as follows: Different voltages V0 and V1 are applied to the stationary and moving comb teeth on one side in the target torsion direction. The moving comb teeth are affected by the electrostatic force and rotate towards the stationary comb teeth direction, driving the mirror to rotate. The linear torsion moment provided by the vertically staggered comb tooth driver cooperates with the multi-fold torsion beam with a special shape to achieve the linear motion of the torsion mirror.

[0075] Embodiment 3

[0076] Figure 9 It shows the structure of the non-linear attenuation torsion mirror in Embodiment 3. In this embodiment, the electrostatic drive method is adopted to provide the torsion moment.

[0077] As Figure 9 shown in the figure, the electrostatically actuated non-linear torsion mirror in this embodiment includes a mirror anchor point 12, a first multi-fold torsion beam 11A and a second multi-fold torsion beam 11B connected to the mirror anchor point 12 and symmetrically arranged with respect to the mirror anchor point 12, a first moving comb tooth 12A and a second moving comb tooth 12B symmetrically arranged on the other two sides of the mirror anchor point 12, a first stationary comb tooth 13A and a second stationary comb tooth 13B corresponding to the moving comb teeth, a mirror support column 15 arranged at the center of the mirror anchor point 12, and a mirror 14 supported by the mirror support column 15. In addition, it also includes a light reflection material coated on the surface of the mirror 14 and a torsion mirror fixing frame (not shown in the figure). The torsion mirror fixing frame is connected to the free ends of the first cross beam and the fourth cross beam in the first multi-fold torsion beam 11A and the second multi-fold torsion beam 11B. The fixing frame fixes the movable part of the entire torsion mirror (including the mirror anchor point 12, the mirror support column 15, the mirror 14, the first multi-fold torsion beam 11A, the second multi-fold torsion beam 11B, the first moving comb tooth 12A and the second moving comb tooth 12B). Compared with Embodiment 2, in the torsion mirror of this embodiment, the comb tooth driver is placed under the mirror, improving the fill factor of the mirror surface.

[0078] The working principle of the electrostatically actuated non-linear torsion mirror in Embodiment 3 is the same as that in Embodiment 2.

[0079] Embodiment 4

[0080] Figure 10 shows the structure of the non-linear attenuation torsion mirror in Embodiment 4. In this embodiment, a piezoelectric drive mode is adopted to provide the torsion moment. Figure 10(A) is a schematic diagram of the piezoelectrically actuated non-linear attenuation torsion mirror, and Figure 10(B) is a partial schematic diagram of the piezoelectric actuator.

[0081] As shown in Figure 10(A), the piezoelectrically actuated non-linear torsion mirror in this embodiment includes a mirror 17, a first multi-fold torsion beam 16A and a second multi-fold torsion beam 16B that are connected to the mirror 17 and symmetrically arranged with respect to the mirror 17, and a first piezoelectric actuator 18A, a second piezoelectric actuator 18B, a third piezoelectric actuator 18C, and a fourth piezoelectric actuator 18D that are symmetrically arranged on the other two sides of the mirror 17. In addition, it also includes a light-reflecting material coated on the surface of the mirror 17 and a torsion mirror fixing frame (not shown in the figure). The torsion mirror fixing frame is connected to the free ends of the first cross beam and the fourth cross beam in the first multi-fold torsion beam 16A and the second multi-fold torsion beam 16B, and is also connected to the first piezoelectric actuator 18A, the second piezoelectric actuator 18B, the third piezoelectric actuator 18C, and the fourth piezoelectric actuator 18D to fix the movable part of the entire torsion mirror (including the mirror 17, the first multi-fold torsion beam 16A, the second multi-fold torsion beam 16B, the first piezoelectric actuator 18A, the second piezoelectric actuator 18B, the third piezoelectric actuator 18C, and the fourth piezoelectric actuator 18D). As shown in Figure 10(B), the piezoelectric actuator 18A includes a support beam 18A.1 and a first piezoelectric layer 18A.21, a second piezoelectric layer 18A.22, and a third piezoelectric layer 18A.23.

[0082] The working principle of the piezoelectrically actuated non-linear torsion mirror in Embodiment 4: Apply the same voltage signal that makes the ends of the piezoelectric actuators move downward to the two piezoelectric actuators on the side of the torsion target direction, and apply the opposite voltage signal that makes the ends of the piezoelectric actuators move upward to the two piezoelectric actuators on the other side. The torsion moment generated by the piezoelectric actuators drives the mirror to rotate. The linear torsion moment provided by the piezoelectric actuators cooperates with the multi-fold torsion beam with a special shape to achieve the linear motion of the torsion mirror.

Claims

1. A non-linearly attenuated MEMS torsion mirror, comprising a driving structure, a movable structure and a fixed frame, wherein the movable structure includes a mirror and a multi-fold torsion beam; Characterized in that: Two multi-fold torsion beams are symmetrically arranged on both sides of the mirror; The multi-fold torsion beam includes three groups of torsion beams, six groups of cross beams and two groups of transition beams; The three groups of torsion beams are parallel to each other, extend in the y direction and are arranged in the x direction, and are respectively the first torsion beam, the second torsion beam and the third torsion beam. The first torsion beam and the third torsion beam are arranged on both sides of the second torsion beam and are symmetric about the second torsion beam; The six groups of cross beams all extend in the x direction and are respectively the first cross beam, the second cross beam, the third cross beam, the fourth cross beam, the fifth cross beam and the sixth cross beam; the first cross beam and the fourth cross beam are arranged on both sides of the second torsion beam and are symmetric about the second torsion beam; the second cross beam and the fifth cross beam are arranged on both sides of the second torsion beam and are symmetric about the second torsion beam; the third cross beam and the sixth cross beam are arranged on both sides of the second torsion beam and are symmetric about the second torsion beam; The two groups of transition beams are respectively the first transition beam and the second transition beam, extend in the y direction, are arranged on both sides of the second torsion beam and are symmetric about the second torsion beam; The first cross beam, the first torsion beam, the second cross beam, the first transition beam and the third cross beam are connected end to end in sequence; The fourth cross beam, the third torsion beam, the fifth cross beam, the second transition beam and the sixth cross beam are connected end to end in sequence; After the third cross beam and the sixth cross beam are connected, they are connected to one end of the second torsion beam, and the other end of the second torsion beam is used to connect to the MEMS torsion mirror; the free ends of the first cross beam and the fourth cross beam are far away from the second torsion beam and are used to connect to the fixed frame of the MEMS torsion mirror; arc chamfers are provided at the connection parts of each beam; The second cross beam and the fifth cross beam are slender beams to ensure a certain deformation during torsion. The deformation can adjust the torsion deformation centers of the first torsion beam and the third torsion beam from the geometric center of the second torsion beam to their respective geometric centers; the free ends of the first cross beam and the fourth cross beam in the two multi-fold torsion beams are both connected to the fixed frame, and the driving structure is used to drive the two multi-fold torsion beams to drive the mirror to move linearly; W 2.6 >W 2.21 >W 2.6 / 2 ≈ W 2.51 >W 2.11 ≈ W 2.31 ; L 2.11 ≈ L 2.41 <L 2.31 / 2.5; where, W 2.6 is the width of the second torsion beam, W 2.21 is the width of the first torsion beam, W 2.51 is the width of the third cross beam, W 2.11 is the width of the first cross beam, W 2.31 is the width of the second cross beam, L 2.11 is the length of the first cross beam, L 2.41 is the length of the first transition beam, L 2.31 is the length of the second cross beam.

2. The non-linearly attenuated MEMS torsion mirror according to claim 1, Characterized in that: The driving structure includes a permanent magnet base, a permanent magnet and an external driving magnetic circuit; the permanent magnet base is arranged at the center position on the back of the mirror, and a groove adapted to the shape of the permanent magnet is opened at the center of the permanent magnet base; the permanent magnet is embedded in the groove of the permanent magnet base; The other ends of the second torsion beams in the two multi-fold torsion beams are respectively connected to the opposite sides of the permanent magnet base; The external driving magnetic circuit applies an electromagnetic force to the permanent magnet, and through the permanent magnet, a rotational torque is applied to the two multi-fold torsion beams to drive the mirror to move linearly and realize optical scanning.

3. The non-linearly attenuated MEMS torsion mirror according to claim 2, Characterized in that: The mirror is a rectangular mirror; a reinforcing rib is further provided on the back of the mirror, and the reinforcing rib extends outward along the length direction of the mirror surface and is integrally formed with the permanent magnet base.

4. The non-linearly attenuated MEMS torsion mirror according to claim 3, Characterized in that: The other ends of the second torsion beams in the two multi-fold torsion beams are respectively connected to opposite sides of the mirror; the driving structure includes moving comb teeth symmetrically arranged on the other two sides of the mirror, and stationary comb teeth corresponding to the moving comb teeth, and the moving comb teeth and the stationary comb teeth form a vertical interleaved comb tooth driver; Different voltages are applied to the moving and stationary comb teeth on one side in the target torsion direction. The moving comb teeth are affected by the electrostatic force and rotate towards the stationary comb teeth, driving the mirror to move linearly to achieve optical scanning.

5. The non-linearity-reduced MEMS torsion mirror according to claim 4, characterized in that: It further includes a mirror anchor and a mirror support pillar; the mirror support pillar is arranged at the center of the mirror anchor, and the mirror is fixed on the mirror support pillar; the other ends of the second torsion beams in the two multi-fold torsion beams are respectively connected to opposite sides of the mirror anchor; the driving structure includes moving comb teeth symmetrically arranged on the other two sides of the mirror anchor, and stationary comb teeth corresponding to the moving comb teeth, and the moving comb teeth and the stationary comb teeth form a vertical interleaved comb tooth driver.

6. The non-linearity-reduced MEMS torsion mirror according to claim 5, characterized in that: The other ends of the second torsion beams in the two multi-fold torsion beams are respectively connected to opposite sides of the mirror; the driving structure includes four groups of piezoelectric drivers symmetrically arranged on the other two sides of the mirror; the four groups of piezoelectric drivers are connected to the fixed frame of the MEMS torsion mirror.

7. The non-linearity-reduced MEMS torsion mirror according to claim 1, characterized in that: W 2.6 ≈1.4 W 2.11 ≈2 W 2.51 ≈4 W 2.11 ≈4 W 2.31 ; L 2.41 ≈L 2.31 / 3。

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