A one-dimensional electromagnetically driven micromirror with large rotation angle and high frequency

Abstract

The invention discloses a large-angle high-frequency one-dimensional electromagnetically driven micromirror, comprising a driving outer frame, a driving coil, an outer frame torsion shaft, an internal mirror surface and an internal torsion shaft; the driving coil is fixedly installed inside the driving outer frame; one end of the outer frame torsion shaft extends out of the driving outer frame, and the other end passes through the driving coil and extends inward; the inwardly extending end of the outer frame torsion shaft is connected to the internal torsion shaft; the internal mirror surface is installed in the driving outer frame through the internal torsion shaft; a driving wire is provided on the outer frame torsion shaft; the driving wire introduces a driving signal into the driving coil; the driving coil controls the internal torsion shaft to drive the internal mirror surface to deflect; the invention adopts a design of separating the driving outer frame from the internal mirror surface, the driving outer frame and the internal mirror surface have different operating frequencies, and there is no driving wire on the internal torsion shaft of the internal mirror surface, thereby realizing high-frequency and large-angle scanning and improving the service life of the micromirror.

Description

Technical Field

[0001] The invention relates to a large-angle high-frequency one-dimensional electromagnetically driven micromirror, belonging to the technical field of micro-photoelectric machine systems. Background Art

[0002] In the era of artificial intelligence, optoelectronic technologies such as laser projection, laser radar, 3D scanning, and MEMS optical switches have become hot topics for many scientific research institutions. Among them, MEMS micromirrors, as key components, are of great significance for the development and research of related technologies. MEMS micromirrors are optical devices made based on micro-nano processing technology. The basic principle is that the reflector is twisted or deformed under the force of a tiny driving structure, and the propagation direction of the light beam is changed by deflecting the micromirror at a certain angle. MEMS micromirrors have the advantages of fast scanning speed, compact structure, and good mechanical properties. They play an important role in many fields such as barcode recognition, laser communication, fiber optic switches, laser radar, and laser display.

[0003] The driving modes of MEMS micromirrors are usually divided into four types: electrostatic drive, electrothermal drive, piezoelectric drive and electromagnetic drive. Electrostatic drive generates electrostatic force through the mutual movement of parallel plate electrodes or comb-tooth electrodes. It has a simple structure, small package size and mature process, but it is easy to attract. Electrothermal drive relies on the thermal expansion effect of the material to deform the shaft structure to make the micromirror vibrate. Generally speaking, the force generated by electrostatic drive and electrothermal drive is small, and is mostly used in application fields such as small-sized micromirrors (i.e., small mirror area). The driving force provided by electrostatic drive is about 0.1mN at a high driving voltage. Piezoelectric drive uses metal / piezoelectric material / metal three-layer materials as the driver. Based on the inverse piezoelectric effect of the crystal, the alternating electric field causes the material to undergo mechanical deformation to generate force. Piezoelectric drive and electromagnetic drive can be used to drive MEMS micromirrors with large mirrors due to their large driving force. Piezoelectric-driven MEMS micromirrors are difficult to combine with MEMS processes and are not suitable for mass production. Electromagnetic-driven MEMS micromirrors are widely studied, and usually use the interaction between external magnets and planar coils to generate Lorentz force drive, and the process is mature.

[0004] Current electromagnetically driven micromirrors all have the power-carrying coil mounted on a torsion beam. The power-carrying coil is generally a metal deposited by electroplating. However, the electroplated metal has many defects. Due to these defects in the wire metal on the torsion beam, a high Q value cannot be achieved, and the large-angle application at the high operating frequency of the MEMS micromirror cannot be met. Furthermore, due to the problem of electroplated metal defects, it is not as good as single-crystal silicon in terms of fatigue resistance. If it works in a resonant state at a large angle for a long time, its life will be significantly reduced, and the electroplated metal is prone to breakage at large angles. Summary of the invention

[0005] In view of the above-mentioned technical problems, the purpose of the present invention is to propose a large-angle and high-frequency one-dimensional electromagnetically driven micromirror, which realizes high-frequency and large-angle scanning and improves the service life of the micromirror.

[0006] The technical solution of the present invention is achieved as follows: a large-angle, high-frequency, one-dimensional electromagnetically driven micromirror comprises a driving outer frame, a driving coil, an outer frame torsion shaft, an internal mirror surface and an internal torsion shaft; the driving coil is fixedly installed inside the driving outer frame; one end of the outer frame torsion shaft extends out of the driving outer frame, and the other end extends inward through the driving coil; the inwardly extending end of the outer frame torsion shaft is connected to the internal torsion shaft; the internal mirror surface is installed in the driving outer frame through the internal torsion shaft; a driving wire is provided on the outer frame torsion shaft; the driving wire introduces a driving signal into the driving coil; the driving coil controls the internal torsion shaft to drive the internal mirror surface to deflect.

[0007] Preferably, the driving outer frame and the internal mirror have different operating frequencies.

[0008] Preferably, the driving wire is deposited metal.

[0009] Preferably, the thickness of the deposited metal is 10um-30um.

[0010] Preferably, the driving outer frame and the inner mirror rotate asynchronously.

[0011] Preferably, the driving coil provides a driving force by driving a gradient magnetic field, and the driving force is greater than 1 mN.

[0012] Preferably, the stress to which the drive coil is deformed is less than 200 MPa.

[0013] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0014] The invention discloses a large-angle high-frequency one-dimensional electromagnetically driven micromirror. A driving coil provides a driving force to an internal mirror surface under the action of an external magnetic field to deflect the internal mirror surface. A driving wire on a torsion axis of an outer frame introduces a driving signal to the driving coil. The driving outer frame and the internal mirror surface have different operating frequencies. The internal mirror surface can operate at a higher operating frequency and meet a large rotation angle, while the torsion of the driving outer frame operates in a low-frequency band. Since the driving wire of the driving coil is a deposited metal, the driving outer frame will have a larger damping when torsion occurs under the influence of the metal, and a large rotation angle at a higher frequency cannot be achieved. The driving outer frame and the internal mirror surface have different working states. The mirror surface operates at the resonant frequency of the internal mirror surface but does not operate at the resonant mode of the driving outer frame. The design of separating the driving outer frame from the internal mirror surface is adopted. The driving outer frame and the internal mirror surface have different operating frequencies. There is no driving wire on the internal torsion axis of the internal mirror surface, thereby achieving high-frequency and large-angle scanning and improving the service life of the micromirror. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The technical solution of the present invention is further described below in conjunction with the accompanying drawings:

[0016] Attached Figure 1 A schematic diagram of the structure of a large-angle, high-frequency, one-dimensional electromagnetically driven micromirror according to the present invention;

[0017] Attached Figure 2 This is a diagram showing the working state of the internal mirror surface of a large-angle, high-frequency, one-dimensional electromagnetically driven micromirror of the present invention;

[0018] Attached Figure 3 A current angle curve of a large-angle, high-frequency, one-dimensional electromagnetically driven micromirror of the present invention;

[0019] Among them: 1. driving outer frame; 2. driving coil; 3. outer frame torsion axis; 4. internal mirror; 5. internal torsion axis; 6. driving wire. DETAILED DESCRIPTION

[0020] The present invention will be described below in conjunction with the accompanying drawings.

[0021] As attached Figure 1-3 The figure shows a large-angle, high-frequency, one-dimensional electromagnetically driven micromirror described in the present invention, comprising a driving outer frame 1, a driving coil 2, an outer frame torsion shaft 3, an internal mirror surface 4 and an internal torsion shaft 5; the driving coil 2 is fixedly installed inside the driving outer frame 1; one end of the outer frame torsion shaft 3 extends out of the driving outer frame 1, and the other end extends inward through the driving coil 2; the inwardly extending end of the outer frame torsion shaft 3 is connected to the internal torsion shaft 5; the internal mirror surface 4 is installed in the driving outer frame 1 through the internal torsion shaft 5; a driving wire 6 is provided on the outer frame torsion shaft 3; the driving wire 6 introduces a driving signal into the driving coil 2; the driving coil 2 controls the internal torsion shaft 5 to drive the internal mirror surface 4 to deflect.

[0022] The driving outer frame 1 and the internal mirror 4 have different operating frequencies, so that the micromirror only works on the internal mirror, and the driving outer frame 1 does not vibrate, thereby preventing the driving wire 6 on the driving outer frame 1 from breaking due to excessive deformation.

[0023] In order to better solve the stress problem of the driving wire 6, the driving wire 6 is a deposited metal, and the thickness of the deposited metal is 10um-30um.

[0024] In order to realize the micromirror rotation at a larger angle, the driving outer frame 1 and the inner mirror surface 4 rotate asynchronously.

[0025] In order to provide a higher driving force for the micromirror and enable the micromirror to achieve a larger deflection angle, the driving coil 2 provides a driving force by a gradient magnetic field driving method, and the driving force is greater than 1 mN.

[0026] In order to prevent the driving coil 2 from breaking under a condition of high stress, the stress on the driving coil 2 during deformation is less than 200 MPa.

[0027] Embodiment 1, the present invention adopts the design of separating the internal mirror 4 from the driving outer frame 1, and the driving coil 2 provides driving force to the internal mirror 4 under the action of the external magnetic field to make the internal mirror 4 deflect, and the driving wire 6 on the outer frame torsion shaft 3 introduces the driving signal to the driving coil 2. In actual operation, the driving outer frame 1 and the internal mirror 4 have different operating frequencies. The internal mirror 4 can operate at a higher operating frequency and meet a large turning angle, while the torsion of the driving outer frame 1 operates in a low frequency band. This is mainly because the driving wire 6 of the driving coil 2 is deposited metal. Under the influence of the metal, the driving outer frame 1 will have a greater damping effect when torsion occurs. When the internal mirror 4 is twisted at a large angle, the outer frame torsion shaft 3 does not deform, so the metal on the outer frame torsion shaft 3 will not break and fail, and a large turning angle at a higher frequency cannot be achieved.

[0028] When the driving outer frame 1 and the internal mirror 4 are both working at a mechanical angle of 15°, it can be seen from the stress on the driving wire 6 on the driving outer frame 1 when the micromirror is working that when the driving outer frame 1 is in working state, the stress on the driving wire 6 is 529MPa; when the internal mirror 4 is in working state, the stress on the driving wire 6 is 83MPa. Since the driving coil 2 is generally a deposited metal with a general thickness of 10um-30um, defects are easily generated during the deposition process due to the thicker metal. Therefore, the yield strength of the driving wire 6 is not as good as that of single crystal silicon, and it is easy to break under high stress. From our test results, it is concluded that the driving coil 2 is prone to failure when the stress exceeds 200MPa.

[0029] When working at high frequency, there is a rotation angle of the driving wire 6 on the internal torsion axis 5. It can be seen that the driving wire 6 will obviously affect the Q value of the micromirror. By driving the outer frame 1 and the internal mirror 4 separately, a high Q value can be achieved because there is no metal on the internal torsion axis 5. When there is no driving wire 6 on the internal torsion axis 5, the Q value can reach 1200, while it can only reach 110 when there is a driving wire 6. The optical angle also has obvious differences when the driving current is constant.

[0030] The invention discloses a large-angle high-frequency one-dimensional electromagnetic driven micromirror. Under the action of an external magnetic field, a driving coil 2 provides a driving force to an internal mirror 4 to deflect the internal mirror 4. A driving wire 6 on an outer frame torsion shaft 3 introduces a driving signal to the driving coil 2. The driving outer frame 1 and the internal mirror 4 have different operating frequencies. The internal mirror 4 can operate at a higher operating frequency and meet a large angle, while the torsion of the driving outer frame 1 operates in a low frequency band. Since the driving wire 6 of the driving coil 2 is a deposited metal, the driving outer frame 1 has a larger damping when torsion under the influence of the metal, and a large angle at a higher frequency cannot be achieved. The driving outer frame 1 and the internal mirror 4 have different working states. The mirror 4 operates at a resonant frequency and does not operate at a resonant mode of the driving outer frame 1. The design of separating the driving outer frame 1 from the internal mirror 4 is adopted. The driving outer frame 1 and the internal mirror 4 have different operating frequencies. There is no driving wire 6 on the internal torsion shaft 5 of the internal mirror 4, thereby achieving high-frequency and large-angle scanning and improving the service life of the micromirror.

[0031] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the content of the present invention and implement it. They cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A large-angle, high-frequency, one-dimensional electromagnetically driven micromirror, characterized in that: It includes a driving outer frame, a driving coil, an outer frame torsion shaft, an internal mirror and an internal torsion shaft; the driving coil is fixedly installed inside the driving outer frame; one end of the outer frame torsion shaft extends out of the driving outer frame, and the other end passes through the driving coil and extends inward; the inwardly extending end of the outer frame torsion shaft is connected to the internal torsion shaft; the internal mirror is installed in the driving outer frame through the internal torsion shaft; a driving wire is provided on the outer frame torsion shaft; the driving wire introduces a driving signal into the driving coil; the driving coil controls the internal torsion shaft to drive the internal mirror to deflect; the driving outer frame and the internal mirror have different operating frequencies; the driving wire is deposited metal.

2. A large-angle, high-frequency, one-dimensional electromagnetically driven micromirror as claimed in claim 1, characterized in that: The thickness of the deposited metal is 10um-30um.

3. A large-angle, high-frequency, one-dimensional electromagnetically driven micromirror as claimed in claim 1, characterized in that: The driving outer frame and the inner mirror surface rotate asynchronously.

4. A large-angle, high-frequency, one-dimensional electromagnetically driven micromirror as claimed in claim 1, characterized in that: The driving coil provides a driving force by driving a gradient magnetic field, and the driving force is greater than 1 mN.

5. A large-angle, high-frequency, one-dimensional electromagnetically driven micromirror as claimed in claim 1, characterized in that: The stress of the driving coil is less than 200 MPa.

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