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CN119002041A - High-bandwidth MEMS scanning mirror device and design method thereof - Google Patents

High-bandwidth MEMS scanning mirror device and design method thereof Download PDF

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Publication number
CN119002041A
CN119002041A CN202411257227.4A CN202411257227A CN119002041A CN 119002041 A CN119002041 A CN 119002041A CN 202411257227 A CN202411257227 A CN 202411257227A CN 119002041 A CN119002041 A CN 119002041A
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mirror
micro
scanning mirror
bandwidth
scanning
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CN119002041B (en
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吴亚明
周碧青
凌必赟
王潇悦
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Shanghai Institute of Microsystem and Information Technology of CAS
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Shanghai Institute of Microsystem and Information Technology of CAS
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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
    • G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
    • G02B26/0816—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light by means of one or more reflecting elements
    • G02B26/0833—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light by means of one or more reflecting elements the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B81—MICROSTRUCTURAL TECHNOLOGY
    • B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
    • B81B7/00—Microstructural systems; Auxiliary parts of microstructural devices or systems
    • B81B7/02—Microstructural systems; Auxiliary parts of microstructural devices or systems containing distinct electrical or optical devices of particular relevance for their function, e.g. microelectro-mechanical systems [MEMS]
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/0012—Optical design, e.g. procedures, algorithms, optimisation routines

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Micromachines (AREA)

Abstract

The invention provides a high-bandwidth MEMS scanning mirror device and a design method thereof, wherein the maximum driving torque tau of the high-bandwidth MEMS scanning mirror device, the maximum scanning angle theta max of a micro-mirror and the torsional rigidity K θ＝τ/(θmaxN2 of a flexible torsion beam are larger than 1; the feedback control chip receives the real-time torsion angle and the target scanning angle sensed by the monolithic integrated angle sensor, and processes the real-time torsion angle and the target scanning angle to obtain an adjustment closed-loop feedback driving signal to control the torsion of the micro-reflector in a closed-loop feedback manner. The torsional rigidity of the flexible torsion beam is 1/N 2 of the conventional torsional rigidity, the scanning working bandwidth of a scanning mirror device is improved by matching with feedback control, and the thinking inertia of the MEMS scanning mirror for improving the bandwidth is broken; meanwhile, the torsional rigidity of torsion beams of the micro-reflectors with different sizes is different, so that the structural strength of the scanning mirror is ensured, and the scanning working bandwidth is optimized; in addition, the PID algorithm feeds back to control the torsion of the micro-mirror, so that the scanning working bandwidth is greatly improved.

Description

High-bandwidth MEMS scanning mirror device and design method thereof
Technical Field
The invention belongs to the technical field of semiconductor integrated circuit manufacture and the technical field of optics, and particularly relates to a high-bandwidth MEMS scanning mirror device and a design method thereof.
Background
The MEMS scanning mirror is an optical MEMS device which integrates an MEMS micro driver and a micro reflecting mirror into a single chip by adopting an MEMS process, has the functions of fast and high-precision beam biaxial pointing and multi-axis scanning due to small size and light weight, and has important application in modern optical technology. With the increasing wide application of optical MEMS technology, higher requirements are put on the scanning speed and the scanning working bandwidth of the MEMS scanning mirror, so as to adapt to various rapid optical scanning applications. The system comprises a precise tracking MEMS quick-reflecting mirror of a space laser communication terminal, an image stabilizer or a laser pointing stabilizer of an on-vehicle or airborne moving platform, and a high-bandwidth (about 0.5-2 kHz) MEMS scanning mirror which needs a large-size mirror surface in high-speed laser processing (cutting, punching, welding and the like), high-speed 3D laser printing and other equipment; and high bandwidth (about 10-100 kHz) MEMS scanning mirrors and arrays thereof with small-size mirrors are also required in MEMS high-speed (100 kHz) optical phase shifter arrays, MEMS high-speed (microsecond) optical switches, MEMS high-speed (microsecond) optical switch arrays, and the like.
The current design concept of the MEMS scanning mirror design technology is to increase the working mode frequency of the MEMS scanning mirror as much as possible under the condition of permission of driving force or torque so as to obtain the rapid scanning characteristic of the MEMS scanning mirror and further obtain the maximum scanning working bandwidth. Since the unidirectional driving force or driving torque of the electrostatic driving "electrostatic attraction force" of the MEMS scanning mirror mainly depends on the elastic resilience of the flexible torsion beam during the scanning in the opposite direction, the industry always holds the design idea of "the higher the rigidity of the flexible torsion beam, the higher the elastic resilience, and the faster the scanning speed of the MEMS scanning mirror".
However, due to the limitations of MEMS process parameters and the driving capability of driving electric signals, the rigidity of the flexible torsion beam cannot continuously and linearly improve the working bandwidth of the MEMS scanning mirror, so that the improvement of the scanning working bandwidth of the conventional MEMS scanning mirror is greatly limited, and the increasing high-bandwidth scanning application requirements cannot be met.
Therefore, there is a need to develop new MEMS scanning mirror device designs and drive control methods to meet the demands for higher bandwidth MEMS scanning mirrors in practical applications.
It should be noted that the foregoing description of the background art is only for the purpose of providing a clear and complete description of the technical solutions of the present application and is thus convenient for a person skilled in the art to understand, and it should not be construed that the above technical solutions are known to the person skilled in the art merely because these solutions are described in the background art section of the present application.
Disclosure of Invention
In view of the above drawbacks of the prior art, an object of the present invention is to provide a high bandwidth MEMS scanning mirror device and a design method thereof, which are used for solving the problem that bandwidth improvement of the MEMS scanning mirror device is limited in the prior art.
To achieve the above object, the present invention provides a high bandwidth MEMS scanning mirror device comprising: the high-bandwidth MEMS scanning mirror chip, the power supply driving chip, the angle sensing detection circuit chip, the feedback control chip and the input/output connector;
The high-bandwidth MEMS scanning mirror chip comprises a flexible torsion beam, a micro-mirror, a substrate, a driving structure and an angle sensing detection structure, wherein torsion connection is formed between the micro-mirror and the substrate through the flexible torsion beam, the driving structure controls the micro-mirror to perform torsion motion relative to the substrate, and the angle sensing detection structure is used for detecting the real-time torsion angle of the micro-mirror; the maximum torque which the driving structure can provide for the micro-mirror is tau, and when the maximum scanning angle of the micro-mirror is theta max, the torsional rigidity K θ＝τ/(θmaxN2 of the flexible torsion beam is provided, and N is a number larger than 1;
The power supply driving chip is electrically connected with the driving structure to control the driving state of the driving structure on the micro-reflecting mirror; the angle sensing detection circuit chip is electrically connected with the angle sensing detection structure to receive and process the real-time torsion angle of the micro-mirror detected by the angle sensing detection structure to obtain a real-time angle signal; the input/output connector is electrically connected with the external control system to receive a target angle signal input by the external control system; the feedback control chip is electrically connected with the angle sensing detection circuit chip, the power supply driving chip and the input/output connector, so as to receive the real-time angle signal calculated by the angle sensing detection circuit chip and the target angle signal received by the input/output connector, obtain an adjustment closed-loop feedback driving signal through processing of a preset high-bandwidth feedback control algorithm, transmit the adjustment closed-loop feedback driving signal to the power supply driving chip, control the driving structure to drive the driving state of the micro-mirror through the power supply driving chip, and control the driving structure to drive the micro-mirror to twist in a bidirectional manner through the power supply driving chip.
Optionally, the high bandwidth MEMS scanning mirror chip includes M micro mirrors arranged in an array, each micro mirror has a corresponding flexible torsion beam, a driving structure, and an angle sensing detection structure, the M micro mirrors are on the same substrate, and M is an integer greater than or equal to 1.
Optionally, the preset high-bandwidth feedback control algorithm adopted by the feedback control chip is a PID algorithm, and the real-time angle signal and the target angle signal are processed through the PID algorithm to generate the adjusting closed-loop feedback driving signal.
Optionally, N is 1.1 or more and 20 or less.
Optionally, the mirror surface diameter of the micro-mirror is 0.2 mm-1 mm, the mirror surface thickness of the micro-mirror is 5 micrometers-50 micrometers, and N is more than or equal to 5 and less than or equal to 20.
Optionally, the high bandwidth MEMS scanning mirror device is one of a MEMS high speed optical phase shifter array, a MEMS microsecond level high speed optical switch, or a MEMS microsecond level high speed optical switch array.
Optionally, the mirror surface diameter of the micro-mirror is 3 mm-20 mm, the mirror surface thickness of the micro-mirror is 50 micrometers-500 micrometers, and N is less than 5.
Optionally, the high bandwidth MEMS scanning mirror device is one of a MEMS fast mirror, an image stabilizer, a laser pointing stabilizer, a high speed laser processing device, or a high speed 3D laser printing device.
Optionally, the mirror surface diameter of the micro-mirror is 1 mm-3 mm, the mirror surface thickness of the micro-mirror is 20 micrometers-200 micrometers, and N is more than or equal to 4 and less than or equal to 15.
The invention also provides a design method of the high-bandwidth MEMS scanning mirror device, which is used for designing any one of the high-bandwidth MEMS scanning mirror devices, and comprises the following steps:
According to the driving structure and the driving voltage of the high-bandwidth MEMS scanning mirror device, calculating the maximum torque which can be provided for the micro-mirror by the high-bandwidth MEMS scanning mirror device as tau through a simulation tool, wherein the design target of the maximum scanning angle of the micro-mirror of the high-bandwidth MEMS scanning mirror device is theta max;
Calculating the torsional rigidity K θ＝τ/(θmaxN2 of the flexible torsion beam of the high-bandwidth MEMS scanning mirror device, wherein N is a number larger than 1; a flexible torsion beam with a torsional stiffness of K θ1 is used as a torsional connection between the micro-mirror and the substrate of the high bandwidth MEMS scanning mirror device.
As described above, the high bandwidth MEMS scanning mirror device and the design method thereof of the present invention have the following beneficial effects:
According to the invention, the torsional rigidity of the flexible torsion beam is 1/N 2 of the conventional torsional rigidity tau/theta max, so that the torsional rigidity of the flexible torsion beam is reduced to improve the acceleration of the micro-mirror during torsional acceleration, the feedback control of the feedback control chip on the torsional motion state is matched, the acceleration of the micro-mirror during torsional deceleration is improved, overshoot generated by overlarge torsional amplitude of the scanning mirror is avoided, and the working bandwidth which can be realized by the scanning mirror device is greatly improved;
according to the invention, the torsional rigidity of the micro-reflectors with different sizes is reduced to different degrees, so that the structural strength of the micro-reflectors is ensured, and the optimization of the working bandwidth is realized;
The invention utilizes PID algorithm to carry out torsion feedback control of the micro-mirror, thereby further improving the achievable working bandwidth;
The invention improves the working bandwidth by reducing the torsional rigidity of the torsion beam instead of the conventional mode of increasing the torsional rigidity and matching with feedback control, thereby breaking through the design thinking inertia of the MEMS scanning mirror device for improving the bandwidth.
Drawings
Fig. 1 is a schematic diagram showing a top view of the basic structure of a high bandwidth MEMS scanning mirror chip in embodiment 1 of the present invention.
Fig. 2 is a schematic diagram showing a side view structure of a high bandwidth MEMS scanning mirror chip in embodiment 1 of the present invention.
Fig. 3 is a schematic diagram showing a side view structure of a high bandwidth MEMS scanning mirror chip in embodiment 1 of the present invention.
Fig. 4 shows a schematic diagram of a side view structure presented within the package of a high bandwidth MEMS scanning mirror device in the example of embodiment 1 of the present invention.
Fig. 5 is a schematic view showing a cross-sectional view of a high bandwidth MEMS scanning mirror chip electrode and leads in embodiment 4 of the present invention.
Description of element reference numerals
100. A high bandwidth MEMS scanning mirror chip; 111. an inner shaft torsion beam; 112. an outer shaft torsion beam; 113. a moving frame; 114. flexible support microstructures/cushioned flexible support beams; 115. a buffer support frame; 120. a micro-mirror; 121. an optical high reflection film; 130. a substrate; 131. a bonding layer; 132. an insulating oxide layer; 133. an electrode pad; 134. a peripheral substrate; 140. a driving structure; 141. a driving electrode; 142. driving the electrode leads; 143. a linear insulation trench; 150. an angle sensing detection structure; 151. a sensing electrode; 152. a sensing electrode lead; 153. a circular insulation trench; 161. a scan inner shaft; 162. a scanning outer shaft; 170. an air gap;
210. a power supply driving chip; 220. an angle sensing detection circuit chip; 230. a feedback control chip;
300. A high bandwidth MEMS scanning mirror device; 310. an input/output connector; 320. a PCB board; 321. a bonding wire; 330. soft flat cable; 340. packaging the shell; 341. a light window; 342. an incident light beam; 343. and emitting a light beam.
Detailed Description
Other advantages and effects of the present invention will become apparent to those skilled in the art from the following disclosure, which describes the embodiments of the present invention with reference to specific examples. The invention may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present invention.
As described in detail in the embodiments of the present invention, the schematic drawings showing the structure of the apparatus are not partially enlarged to general scale, and the schematic drawings are merely examples, which should not limit the scope of the present invention. In addition, the three-dimensional dimensions of length, width and depth should be included in actual fabrication.
For ease of description, spatially relative terms such as "under", "below", "beneath", "above", "upper" and the like may be used herein to describe one element or feature's relationship to another element or feature as illustrated in the figures. It will be understood that these spatially relative terms are intended to encompass other orientations of the device in use or operation in addition to the orientation depicted in the figures.
In the context of the present application, a structure described as a first feature being "on" a second feature may include embodiments where the first and second features are formed in direct contact, as well as embodiments where additional features are formed between the first and second features, such that the first and second features may not be in direct contact.
It should be noted that, the illustrations provided in the present embodiment merely illustrate the basic concept of the present invention by way of illustration, and only the components related to the present invention are shown in the drawings rather than the number, shape and size of the components in actual implementation, and the form, number and proportion of each component in actual implementation may be arbitrarily changed, and the layout of the components may be more complex.
Example 1:
The present embodiment provides a high bandwidth MEMS scanning mirror device 300, as shown in fig. 1-4, the high bandwidth MEMS scanning mirror device 300 comprising: a high bandwidth MEMS scanning mirror chip 100, a power driving chip 210, an angle sensing detection circuit chip 220, a feedback control chip 230, and an input/output connector 310;
As shown in fig. 1 to 3, the high bandwidth MEMS scanning mirror chip 100 includes a flexible torsion beam, a micro-mirror 120, a substrate 130, a driving structure 140 and an angle sensing detection structure 150, wherein the micro-mirror 120 and the substrate 130 are in torsion connection through the flexible torsion beam, the driving structure 140 controls the micro-mirror 120 to perform torsion motion relative to the substrate 130, and the angle sensing detection structure 150 is used for detecting a real-time torsion angle of the micro-mirror 120; the maximum torque that the driving structure 140 can provide to the micro-mirror 120 is τ, and when the maximum scanning angle of the micro-mirror 120 is θ max, the torsional rigidity K θ＝τ/(θmaxN2 of the flexible torsion beam is N, which is a number greater than 1;
The power driving chip 210 is electrically connected to the driving structure 140 to control the driving state of the driving structure 140 on the micro-mirror 120; the angle sensing detection circuit chip 220 is electrically connected with the angle sensing detection structure 150, so as to receive and process the real-time torsion angle of the micro mirror 120 detected by the angle sensing detection structure 150, and obtain a real-time angle signal; the input/output connector 310 is electrically connected to an external control system to receive a target angle signal input by the external control system; the feedback control chip 230 is electrically connected to the angle sensing detection circuit chip 220, the power driving chip 210, and the input/output connector 310, so as to receive the real-time angle signal calculated by the angle sensing detection circuit chip 220 and the target angle signal received by the input/output connector 310, and process the real-time angle signal by a preset high bandwidth feedback control algorithm to obtain an adjusted closed loop feedback driving signal, and transmit the adjusted closed loop feedback driving signal to the power driving chip 210, and the power driving chip 210 controls the driving structure 140 to drive the driving state of the micro mirror 120, and the power driving chip 210 controls the driving structure 140 to drive the micro mirror 120 to twist bidirectionally.
In the prior art, since the MEMS scanning mirror does not include a bearing with small friction as in a common electromechanical driving mechanical structure, the deceleration acceleration is controlled mainly by an electromagnetic driver, but is limited by the resistance of the torsion resilience force of the flexible torsion beam, and the open loop scanning control is adopted, the improvement of the deceleration acceleration is achieved mainly by considering how to improve the torsion resilience force in the MEMS scanning mirror, and the scanning speed is improved by not considering to reduce the torsion resilience force. Therefore, the general design concept of the MEMS scanning mirror design technology (called as "ordinary design technology") is to increase the intrinsic frequency f of the scanning working mode of the MEMS scanning mirror as much as possible under the condition of the permission of the MEMS chip design, so as to obtain the rapid scanning characteristic of the MEMS scanning mirror and further obtain the maximum scanning working bandwidth. This design concept derives from the unidirectional driving force or driving torque of the electrostatic driving "electrostatic attraction force" of the MEMS scanning mirror, and scanning in the opposite direction mainly depends on the resilience force of the flexible torsion beam, so the industry has always considered that the higher the stiffness of the flexible torsion beam, the greater the resilience force of the flexible torsion beam, and the faster the scanning speed of the MEMS scanning mirror. The design concept is to increase the scanning operation mode frequency of the MEMS scanning mirror as much as possible according to the design target theta max of the maximum scanning angle of the MEMS scanning mirror chip under the condition that the driving force or torque is allowed. Under the guidance of the design concept, the specific steps of the ordinary design technology of the MEMS scanning mirror are as follows:
1) According to the chip size of the MEMS scanning mirror, the microstructure technological parameters (limited by the existing MEMS processing technology), the driving mode and the driving signal size, the maximum driving torque tau max of the MEMS driver can be calculated and simulated;
2) According to the index requirement of the angle scanning range (-theta max to +theta max) of the MEMS scanning mirror, under the guidance of the design thought of 'maximally improving the intrinsic frequency of the scanning working mode of the MEMS scanning mirror', the torsional rigidity of the flexible torsion beam of the MEMS scanning mirror is maximally improved in design, and the design torsional rigidity K θ＝τmax/θmax is obtained;
3) According to a formula f Ordinary times ＝(2π)-1(Kθ/I)1/2, the working mode eigenfrequency f Ordinary times of the MEMS scanning mirror is obtained, wherein I is the moment of inertia of the MEMS scanning mirror around a scanning axis;
4) By the microstructure air damping design, the motion damping coefficient of the MEMS scanning mirror is controlled to be close to the near damping, the working bandwidth of open loop control is only about 50-70% of the working mode eigenfrequency f Ordinary times under the drive of a step driving signal, and the maximum working bandwidth of closed loop control is 4 times of the working mode eigenfrequency f Ordinary times in the ordinary design.
The design method cannot continuously improve the scanning working bandwidth of the MEMS scanning mirror by continuously increasing the torsional rigidity of the flexible torsion beam due to the limitation of MEMS process parameters and the magnitude of driving electric signals, and meanwhile, the increase of the torsional rigidity can bring the driving acceleration during initial acceleration to be realized by requiring higher driving voltage, the improvement of the driving voltage is limited, the driving acceleration during initial acceleration is limited, and the improvement of the whole scanning working bandwidth is limited; the rigidity of the flexible torsion beam is reduced, so that the resilience force of the flexible torsion beam is reduced, the acceleration of the MEMS scanning mirror during torsion deceleration is reduced, and the working bandwidth is reduced; although the working bandwidth can be improved by using closed-loop feedback control, the current scanning working bandwidth of the closed-loop feedback control can only reach 4 times of the intrinsic resonance frequency f Ordinary times of the corresponding scanning mode at most, and the application requirement of the current increasing high-bandwidth MEMS scanning mirror can not be met due to the limitation of the driving acceleration in initial acceleration caused by the structure of continuously increasing the torsional rigidity of the flexible torsion beam for increasing the working bandwidth. For example, a fine tracking MEMS fast mirror of a space laser communication terminal, an image stabilizer of an on-vehicle or airborne moving platform, a laser directional stabilizer, a high-bandwidth MEMS scanning mirror with a large-size mirror surface (with the diameter of 3-20 mm) in high-speed laser processing (cutting, punching, welding and the like), high-speed 3D laser printing equipment and the like are applied, and the bandwidth is required to be about 0.5-2 kHz; or a high bandwidth MEMS scanning mirror and an array thereof which need a small-sized mirror surface (diameter of 0.2 mm-1.0 mm) in the applications of MEMS high-speed (100 kHz) optical phase shifter arrays, MEMS high-speed (microsecond) optical switches, MEMS high-speed (microsecond) optical switch arrays and the like, and the bandwidth needs to be about 10-100 kHz; the large-size MEMS scanning mirror with the mirror surface diameter of 10 millimeters is obtained by using the ordinary design technology, the scanning angle range is +/-0.3 degrees, the intrinsic frequency of the scanning mode is about 150Hz, the open loop control scanning working bandwidth is only 100Hz, the closed loop control working bandwidth can reach 600Hz at most, and the requirement of the MEMS quick reflection mirror cannot be met; for a small-size MEMS scanning mirror with the mirror surface diameter of 0.2-1 mm, the scanning working mode frequency is about 1-2kHz, the open-loop control working bandwidth is 500-1000Hz, the closed-loop control working bandwidth is 4-8kHz, and the requirement of high-speed MEMS optical exchange with microsecond switching time on the working bandwidth is difficult to meet.
Therefore, the electromechanical quick-reflecting mirror of the traditional technology imported from abroad is used in a large number of space laser communication systems in China at present, piezoelectric ceramics or voice coil motors are used as scanning drivers, eddy current sensors are used as scanning angle sensors, metal flexible mechanisms or bearings are used as biaxial movement mechanisms, a large number of elements are used for manual assembly, the space laser communication system is large in size, heavy in weight, high in cost and high in driving power consumption, and the space laser communication system becomes one of important reasons for high cost of a commercial space satellite laser communication terminal system, and the MEMS quick-reflecting mirror is manufactured in a low-cost batch mode by adopting MEMS technology, so that the space laser communication system has important significance for developing a new generation of light, small-sized and low-cost satellite laser communication systems required by commercial space in China.
In the invention, the torsional rigidity of the flexible torsion beam is reduced to 1/N 2 of the torsional rigidity K θ( Ordinary times ) in the ordinary design technology, so that the torsional rigidity of the flexible torsion beam is not increased, and in contrast to the ordinary design technology, the torsional rigidity of the flexible torsion beam is reduced, and the working mode frequency f of the high-bandwidth MEMS scanning mirror device 300 is reduced to 1/N times of the ordinary design working mode frequency f Ordinary times ; the torsional rigidity is reduced, the rebound resistance is reduced, the acceleration of the flexible torsion beam in the initial accelerated torsion process is improved, the rapid scanning is realized, meanwhile, the driving state of the flexible torsion beam is continuously fed back and adjusted by matching with the design of the feedback control chip 230, the acceleration of the flexible torsion beam during deceleration is controlled to be kept in a required range, thereby avoiding torsion overshoot of the torsion beam, and simultaneously, the MEMS scanning mirror device with higher bandwidth (faster reaction speed) than the MEMS scanning mirror device in the prior art can be realized under the same driving voltage, so that the high requirement of the MEMS scanning mirror device for scanning working bandwidth, which is rapidly developed, can be adapted. Under the same design constraint, the scanning working bandwidth BW can reach N times (N is larger than 1) of the scanning working bandwidth BW Ordinary times of the traditional MEMS scanning mirror chip design, thereby being beneficial to the technological application breakthrough of the MEMS scanning mirror in various key fields, effectively improving the production efficiency and parameter performance of the traditional high-cost quick-reflection mirror and other equipment, and having wide application prospect.
Specifically, the real-time angle signal and the target angle signal may be angle values or curves of angles changing with time, and are set according to needs.
Specifically, the feedback control bandwidth of the preset high bandwidth feedback control algorithm is at least 2 times of the design working bandwidth BW of the high bandwidth MEMS scanning mirror device 300, and the feedback control bandwidth may be up to 5 to 15 times of the working bandwidth BW of the MEMS scanning mirror chip; the signal output bandwidth of the angle sensing structure 150 is 5 to 15 times the design operating bandwidth BW of the high bandwidth MEMS scanning mirror device 300; the scanning working bandwidth BW of the high bandwidth MEMS scanning mirror chip 100 is greater than or equal to 4N times (20 is greater than or equal to 1.1) the intrinsic resonant frequency f Ordinary times of the working mode of the MEMS scanning mirror chip in the ordinary design, that is, BW is greater than or equal to n×bw Ordinary times , so that the scanning bandwidth BW of the high bandwidth MEMS scanning mirror chip 100 can be up to 4.4 to 80 times of f Ordinary times , which is far greater than the working bandwidth BW Ordinary times which is 4 times of f Ordinary times as much as possible in the ordinary design by adopting closed loop feedback control.
Specifically, taking an MEMS scanning mirror with a scanning operation bandwidth BW of 2300Hz as an example, the driving control method of the high bandwidth MEMS scanning mirror device 300 is as follows:
First, step 1 is performed, and the angle sensing detection circuit chip 220 of the high bandwidth MEMS scanning mirror device 300 detects the torsion angle of the micro mirror 120 of the high bandwidth MEMS scanning mirror device 300.
Specifically, the torsion angle detected by the angle sensing detection circuit chip 220 is transmitted through an angle signal, and the frequency of the angle signal must reach 11500Hz-23000Hz to ensure the feedback speed of the angle signal, so as to achieve the goal of increasing the working bandwidth of the high bandwidth MEMS scanning mirror device 300 to a preset level.
Then, step2 is performed, where the feedback control chip 230 receives the real-time angle signal obtained by the angle sensing detection circuit chip 220 and the target angle signal received by the input/output connector 310, and calculates the driving state of the micro-mirror 120 according to the preset high bandwidth feedback control algorithm through the obtained torsion angle, so as to obtain an adjusted closed loop feedback driving signal.
Finally, step 3 is performed, where the feedback control chip 230 transmits the obtained adjusted closed-loop feedback driving signal to the power driving chip 210 of the high-bandwidth MEMS scanning mirror device 300, and the power driving chip 210 adjusts the driving state of the micro mirror 120 according to the obtained adjusted closed-loop feedback driving signal, and returns to step 1.
In one embodiment, the feedback control chip 230 uses a PID algorithm to perform the calculation feedback of the adjustment closed-loop feedback driving signal, the feedback bandwidth of the feedback control chip 230 using the PID algorithm reaches 11500Hz-23000Hz, the frequency of the driving control signal transmitted to the driving structure 140 by the power driving chip 210 to drive the micro-mirror 120 driving state must reach 11500Hz-23000Hz, so as to ensure the speed of feedback control and driving, and achieve the goal of increasing the working bandwidth of the high bandwidth MEMS scanning mirror device 300 to a preset level.
Specifically, the magnitude of the feedback bandwidth of the PID algorithm is related to the control precision of the scanning angle, the larger the PID feedback bandwidth is, the higher the scanning angle precision is, and the PID feedback bandwidth reaches 5-10 times of the scanning working bandwidth of the high-bandwidth MEMS scanning mirror device 300, so that the sufficient scanning precision can be ensured to be obtained. It should be noted that, the PID feedback bandwidth requires fast response support of the feedback control chip 230, the angle sensing detection circuit chip 220, and the power driving chip 210, and the chips are selected to meet the technical requirements when the chips are selected. This is easily satisfied with existing chip technology.
The driving structure 140 of the high bandwidth MEMS scanning mirror device 300 used in the present embodiment is also a MEMS electrostatic torsion driver, and is required to provide a bidirectional torsion driving with high angular acceleration, i.e., clockwise or counterclockwise scanning driving can be achieved according to the requirements of the control system, in other words, angular scanning with acceleration or deceleration can be achieved according to the requirements of the feedback control chip 230. Because of the inherent characteristics of electrostatic torsion driving, it is difficult to provide electrostatic attractive force only, that is, electrostatic torsion driving can provide driving torque in only a single torsion direction. A differential driving structure is formed by a pair of electrostatic torsion drivers which are symmetrically arranged in a right-hand manner through flexible torsion Liang Chengzuo, the driving torque of one electrostatic torsion driver is larger than the driving torque of the other electrostatic torsion driver at a certain moment, the driving torque of the MEMS scanning mirror is provided by the torque difference, and the bidirectional torsion driving is realized through the electric signal control of the differential driving structure.
Therefore, in the present embodiment, by applying a bias of 100V dc voltage to a pair of differential structure electrostatic torsion drivers at the same time, the electrostatic torque of the dc bias voltage is balanced when the scanning angle is 0 rad. When positive and negative precise program-controlled voltage signals are respectively applied to the left and right symmetrical differential structure electrostatic torsion drivers, a torque which is about 2 times of the driving torque provided by the single electrostatic torsion driver can be obtained, and the torsion direction is the electrode for applying positive voltage in a steering way. When the polarities of the precise program-controlled voltage signals respectively applied to the two differential structure electrostatic torsion drivers which are bilaterally symmetrical are opposite, the torsion directions are opposite. Therefore, by controlling the polarity of the precise program-controlled voltage signal, the electrostatic bidirectional torsion driving can be realized, and the driving torque can be larger. In order to achieve high-speed scanning driving, a high angular acceleration value (including an acceleration or deceleration angular acceleration value) is a precondition, and bidirectional torsion driving can provide a high angular acceleration to achieve acceleration or deceleration. In the high-speed scanning drive, in order to ensure the angular accuracy of scanning, it is important to prevent the overshoot of scanning, and to reduce and accelerate the speed.
Specifically, assuming that the control system requires a MEMS scanning mirror chip to scan rapidly from 0rad to θ, the electrostatic torsion drive torque τ=k θ( Ordinary times ) θ provided in the control scheme in the ordinary design. As the scanning angular position θ of the inner shaft of the MEMS scanning mirror is scanned from the angular position 0rad to a certain intermediate angular position θ 1, the rebound torque of the inner shaft flexible torsion beam is K θ( Ordinary times )θ1, and during the scanning process, the rebound torque is continuously increased, and the scanning angular acceleration is gradually reduced to 0. The fastest scan time, without considering overshoot (achieved by PID algorithm control feedback), is 1/(4 f), where f is the scan mode frequency of the high bandwidth MEMS scanning mirror chip 100, in this embodiment, the fastest scan is from 0rad to 0.87ms for the MEMS scanning mirror of the prior art, with the exception of the torsional stiffness and drive mode of the flexible torsion beam, and the scan bandwidth of the MEMS scanning mirror is 4f.
As a comparison between the optimized design of the present embodiment and the ordinary design, it is also assumed that the control system needs to rapidly scan the inner shaft of the scanning mirror from 0rad to θ, and the optimized design of the present embodiment provides the torsional stiffness K θ＝Kθ( Ordinary times )/N2 of the flexible torsion beam, and under the same driving voltage condition, the electrostatic driving torque is unchanged, i.e., τ=τ Ordinary times , and the optimized design of the present embodiment provides the electrostatic torsional driving torque:
τ＝N2Kθθ； (1)
In this embodiment, n=2 is taken, so:
τ＝4Kθθ； (2)
＝3 Kθθ+Kθθ (3)
The second term K θ theta in the above formula (3) provides both angular acceleration and rebound torque of the inner shaft flexible torsion beam corresponding to the balanced theta angle, and the first term 3K θ theta can be used to provide angular acceleration up to the scan angle, which torque continuously provides angular acceleration up to the scan angle until the scan angle is less than theta.
As the scanning angular position variable of the inner shaft of the scanning mirror scans from the angular position 0rad to the angular position θ, when only the driving torque of the second term in the expression (3) is considered, the resistance moment caused by the rebound torque of the inner shaft flexible torsion beam gradually increases during the scanning, the scanning angular acceleration gradually decreases to 0, and the fastest scanning time is 1/(4 f) without considering the overshoot (with PID feedback control), and in this embodiment, the fastest scanning scans from the angular position 0rad to the angular position θ is 1.74ms, and thus the scanning bandwidth of the MEMS scanning mirror is 4f.
When considering the driving torque of the first term in the formula (3), 3K θ θ is the driving torque generating the scanning angular acceleration, the generated angular acceleration value is 5000rad/s 2, the acceleration value is at least 3 times larger than the angular acceleration value generated by the driving torque K θ θ of the second term in the formula (3) needing to overcome the flexible torsion Liang Huidan torque, so the total angular acceleration value generated by the formula (3) is more than 4 times larger than the angular acceleration value generated by the driving torque K θ θ needing to overcome the flexible torsion Liang Huidan torque, thereby the scanning time < 1/(4×4f) can be obtained, that is, the scanning bandwidth BW of the high bandwidth MEMS scanning mirror is greater than 16f, and when f=f Ordinary times /N, n=2, 16 f=8f Ordinary times , the scanning bandwidth BW Ordinary times of the MEMS scanning mirror device in the prior art is 4f Ordinary times , that is the optimized design scheme is matched with the optimized driving scheme, and the scanning bandwidth BW of the MEMS scanning mirror is at least 2 times higher than the BW Ordinary times in the prior art.
In one embodiment, the high bandwidth MEMS scanning mirror chip 100 includes M micro-mirrors 120 arranged in an array, each micro-mirror 120 has a corresponding flexible torsion beam, a driving structure 140, and an angle sensing structure 150, and M micro-mirrors 120 are on the same substrate 130, where M is an integer greater than or equal to 1.
In one embodiment, the array of M micro mirrors 120 is a linear array or a square array, and may be arranged in other arrangements as required.
In one embodiment, the high bandwidth MEMS scanning mirror device 300 is a dual-axis scanning mirror device, as shown in fig. 4, the package of the high bandwidth MEMS scanning mirror device 300 further includes an input/output connector 310, a PCB 320 (Printed Circuit Board ), a flexible flat cable 330, and a package case 340 with an optical window 341; the high bandwidth MEMS scanning mirror chip 100, the power driving chip 210, the angle sensing detection circuit chip 220, the feedback control chip 230 and the input/output connector 310 are packaged on the PCB 320, the PCB 320 is fixed on the packaging shell 340 with the optical window 341, the mirror surface of the micro-mirror 120 of the MEMS scanning mirror chip faces the optical window 341, the incident light beam 342 enters the micro-mirror 120 through the optical window 341, and the reflected light beam 343 exits from the micro-mirror 120 through the optical window 341; the high bandwidth MEMS scanning mirror chip 100 is fabricated using MEMS bulk silicon process; the high bandwidth MEMS scanning mirror chip 100 includes a flexible torsion beam, a micro mirror 120, a moving frame 113, a driving structure 140, an angle sensing detection structure 150, an electrode pad 133 (pad), and a substrate 130; the driving structure 140 bidirectionally drives the micro-mirror 120 to twist around a torsion axis in the plane of the high bandwidth MEMS scanning mirror chip 100 under the action of the driving electric signal provided by the power driving chip 210; the bidirectional driving means: a computer-controlled clockwise and anticlockwise high angular acceleration torsional drive; the high bandwidth MEMS scanning mirror chip 100 includes two mutually perpendicular horizontal scanning axes (outer axes) and vertical scanning axes (inner axes) on the mirror surface of the micromirror 120 as torsion axes.
In one embodiment, the high bandwidth MEMS scanning mirror chip 100 is fixed on the front surface of the PCB 320 by using a thermally conductive adhesive, and a gold Wire is used as the Bonding Wire 321 through a Wire Bonding process (Wire Bonding), so as to electrically connect the high bandwidth MEMS scanning mirror chip 100 and the PCB 320.
In one embodiment, the power driving chip 210, the angle sensing detection circuit chip 220, the feedback control chip 230, and the input/output connector 310 are packaged on the back surface of the PCB 320 through a flip-chip bonding process, and the flexible flat cable 330 is led out from the input/output connector 310, so as to form a "MEMS scanning mirror PCB package".
In one embodiment, the power driving chip 210, the angle sensing detection circuit chip 220, and the feedback control chip 230 may be further integrated into an Application Specific Integrated Circuit (ASIC), so as to improve the circuit integration level, reduce the volume, and reduce the cost.
In one embodiment, the PCB 320 of the high bandwidth MEMS scanning mirror device 300 is packaged in a package housing 340, the PCB 320 is fixed to the bottom of the package housing 340 by using a heat conductive adhesive, and the flexible flat cable 330 is led out from a side opening of the package housing 340. The packaging shell 340 is made of aluminum alloy, has good thermal conductivity, and a connecting screw hole is reserved on the packaging shell 340 and is used for being mechanically connected with a rear light path platform of the satellite laser communication terminal. The package case 340 is capped with an optical window 341, the optical window 341 is made of a glass material having a high expansion coefficient, and an antireflection film having an operating wavelength is double-coated on both surfaces of the optical window 341.
In one embodiment, the MEMS driving mode of the driving structure 140 is any one or any combination of two of electrostatic driving, electromagnetic driving and piezoelectric driving.
In one embodiment, the driving manner of the driving structure 140 is electrostatic driving, and the driving structure 140 is one or two of an electrostatic flat panel driver or an electrostatic vertical comb tooth driver;
The electrostatic flat panel driver is composed of a micro-mirror 120 (used as an electrode) and a bottom plane electrode positioned on the surface of a substrate 130, and a gap of several micrometers to tens of micrometers is arranged between the micro-mirror 120 and the bottom plane electrode;
When the electrostatic flat-panel driver is a double-shaft driver, the bottom plane electrode comprises 4 electrically isolated plane electrodes which are symmetrically distributed by two torsion shafts and have the same shape, and the shape of the plane electrode is a conical graph, an isosceles trapezoid or an isosceles triangle;
the static vertical comb tooth driver consists of movable comb teeth and fixed comb teeth, wherein the movable comb teeth and the fixed comb teeth are arranged at equal intervals in a staggered manner, and a height difference exists between the movable comb teeth and the fixed comb teeth; the movable comb teeth and the fixed comb teeth are symmetrically arranged at two sides of the scanning shaft.
In one embodiment, the motion pattern of the micro-mirrors 120 of the high bandwidth MEMS scanning mirror chip 100 is a quasi-static scan, enabling vector scanning (i.e., scanning in a particular temporal order and a specified scan path).
In one embodiment, as shown in FIG. 1, the high bandwidth MEMS scanning mirror chip 100 is a frame motion structure, i.e., a gimbal structure between the micro mirror 120 and the substrate 130 that includes a motion frame 113; the flexible torsion beam is divided into an inner shaft torsion beam 111 and an outer shaft torsion beam 112, and the inner shaft torsion beam 111 and the outer shaft torsion beam 112 are mutually perpendicular in the plane of the high bandwidth MEMS scanning mirror chip 100; two inner torsion beams 111 connecting the micromirror 120 with the moving frame 113; two outer shaft torsion beams 112 connecting the moving frame 113 with the substrate 130 at the periphery of the moving frame 113; the existence of the moving frame 113 makes the inter-axis coupling of the biaxial small, and the torsion angle of the micromirror 120 on one torsion axis has little influence on the other torsion axis when torsion is performed along the other torsion axis. Specifically, the high bandwidth MEMS scanning mirror chip 100 at this time is a biaxial MEMS scanning mirror.
In one embodiment, as shown in fig. 1, a mirror dynamic deformation buffer structure is further disposed between the inner shaft torsion beam 111 and the micro-mirror 120, the mirror dynamic deformation buffer structure includes a flexible support microstructure 114 and buffer flexible support beams 115, and the flexible support microstructure 114 includes an even number of buffer flexible support beams 114, which are symmetrically arranged with the scanning inner shaft 161 and the scanning outer shaft 162 as symmetry axes; one end of the flexible support microstructure 114 supports the micro mirror 120, and the other end thereof is connected to the bumper flexible support beam 115, while the bumper flexible support beam 115 is connected to the inner shaft torsion beam 111.
In one embodiment, the high bandwidth MEMS scanning mirror chip 100 is a frameless motion structure, i.e., no motion frame 113 between the micro mirror 120 and the substrate 130; the flexible torsion beams can twist around the inner shaft and the outer shaft, 4 flexible torsion beams are totally arranged, two flexible torsion beams are symmetrically arranged along one torsion shaft in the inner shaft and the outer shaft, the other two flexible torsion beams are symmetrically arranged along the other torsion shaft, the flexible torsion beams connect the micro-mirror 120 with the peripheral substrate 130, and when the micro-mirror 120 is twisted in a double-shaft manner, the coupling between shafts of the double shafts exists, and when the micro-mirror 120 is twisted along one torsion shaft, the torsion angle of the micro-mirror 120 on the other torsion shaft can be influenced.
Specifically, the high bandwidth scanning mirror device 300 is a single-axis or dual-axis MEMS scanning mirror, and the technical solution of the present invention can be used, which falls within the scope of the present invention.
Preferably, when the high bandwidth scanning mirror device is a dual-axis scanning mirror device, the scanning feedback control of the scanning inner shaft 161 and the scanning outer shaft 162 each use a separate corresponding control channel to receive feedback control signals from the feedback control chip 230, and a crossover control signal is provided between the two control channels to eliminate inter-axis coupling between the dual axes of the dual-axis scanning mirror device.
In one embodiment, the micro-mirrors 120 are silicon micro-mirrors 120.
In one embodiment, the micro-mirror 120 is one of a circle, an ellipse, a square, and a rectangle, and the surface of the micro-mirror 120 is plated with an optical high reflection film, and the material type of the optical high reflection film is gold, silver, aluminum, or a dielectric film.
Specifically, the micro-mirror 120 can be classified into a small-sized mirror having a size of 0.2 mm to 1mm and a mirror thickness of 5 μm to 50 μm according to the mirror size thereof; the size of the medium-size mirror surface is 1 mm-3 mm, and the thickness of the mirror surface is 20 micrometers-200 micrometers; the large-size mirror has a size of 3 mm-20 mm and a mirror thickness of 50 μm-500 μm.
Preferably, when the micro-mirror 120 is a large-sized mirror surface, the mirror surface dynamic deformation buffer structure is provided between the inner torsion beam 111 and the micro-mirror 120.
In one embodiment, the high bandwidth MEMS scanning mirror device 300 is a single axis scanning mirror device.
In one embodiment, the high bandwidth MEMS scanning mirror device 300 is a dual axis scanning mirror device.
In one embodiment, the high bandwidth MEMS scanning mirror device 300 is a three-axis scanning mirror device. In particular, the high bandwidth MEMS scanning mirror device 300 may also be other multi-axis scanning mirror devices as desired.
In one embodiment, the preset high bandwidth feedback control algorithm adopted by the feedback control chip 230 is a PID algorithm, and the real-time angle signal and the target angle signal are processed by the PID algorithm to generate the adjusted closed loop feedback driving signal.
In the prior art, the MEMS scanning mirror is generally driven by a "step driving" manner, and the micro mirror 120 is directly driven to a preset torsion angle, but the driving method is easy to generate overshoot, so that the torsion angle control precision of the micro mirror 120 is low, and the scanning time for reaching the preset torsion angle is long. The present invention provides a bi-directional torsion drive of high angular acceleration for the micromirror 120 by employing PID (Proportion INTEGRAL DIFFERENTIAL, proportional-integral-derivative) algorithm, as can be seen from the foregoing, the driving moment of the high bandwidth MEMS scanning mirror device 300 in the optimized solution is the same as that in the ordinary design at the same driving voltage, but the torsional stiffness of the flexible torsion beam in the optimized design is only 1/N 2 of the ordinary design, The maximum angular acceleration value of the scanning driving in the optimization scheme is at least larger than N 2 times of the maximum angular acceleration value theta max(2πf)2 when the electric driving signal is in step driving, wherein f is the working mode frequency which is reduced to be 1/N times of the working mode frequency f Ordinary times in the high-bandwidth MEMS scanning mirror device 300 in the optimization scheme of the embodiment; Setting the feedback control bandwidth of the PID algorithm to be at least 2 times of the design working bandwidth of the high-bandwidth MEMS scanning mirror device 300, so that the feedback control bandwidth of the feedback control chip 230 is 5 to 15 times of the working bandwidth of the MEMS scanning mirror chip; Because the scanning operating bandwidth BW of the high bandwidth MEMS scanning mirror chip 100 is greater than or equal to 4N times the eigen-resonance frequency f Ordinary times of the operating mode of the MEMS scanning mirror chip in the ordinary design, while the scanning operating bandwidth BW Ordinary times of the MEMS scanning mirror chip in the ordinary design is 4 times the eigen-resonance frequency f Ordinary times of the operating mode of the MEMS scanning mirror chip in the ordinary design, So that the scanning bandwidth BW of the high bandwidth MEMS scanning mirror chip 100 can be up to 4.4 to 80 times f Ordinary times ; the bidirectional torsion driving is matched with the high-bandwidth PID feedback control to dynamically adjust the driving of the micro-mirror 120 more flexibly, so that the hysteresis quality of feedback is greatly reduced, torsion overshoot is avoided, meanwhile, the problems of insufficient resilience force and small deceleration acceleration caused by the reduction of the torsion rigidity of the flexible torsion beam of the micro-mirror 120 during torsion deceleration are solved, the micro-mirror 120 can ensure high-speed reaction in the acceleration and deceleration processes, and the scanning working bandwidth of the MEMS scanning mirror is greatly improved.
In one embodiment, N is 1.1 or more and 20 or less.
The invention ensures that the torsional rigidity of the flexible torsion beam is reduced and the resilience force is reduced by limiting the value range of N so as to improve the initial acceleration, and simultaneously ensures that the translational rigidity of the flexible torsion beam can meet the strength requirement of the manufacture and application of the micro-mirror 120 on the flexible torsion beam and ensure the reliability and service life of the MEMS scanning mirror structure. Specifically, the value of N is set according to the shock resistance/vibration energy of the flexible torsion beam in the torsion scanning process of the MEMS scanning mirror, so that the service life and the structural reliability of the flexible torsion beam are ensured.
In one embodiment, the angle sensing structure 150 is one of a capacitive angle sensor or a piezoresistive angle sensor;
When the angle sensing detecting structure 150 is a capacitive angle sensor, it may be a plate capacitive angle sensor or a comb capacitive angle sensor;
When the angle sensing structure 150 is a piezoresistive angle sensor, a silicon strain resistor is fabricated on the flexible torsion beam, the scanning of the micro-mirror 120 causes the strain of the flexible torsion beam to change linearly with the scanning angle, and the change of the silicon strain resistor is detected by forming a wheatstone bridge circuit by the silicon strain resistor and a reference resistor, so that the scanning angle of the micro-mirror 120 can be sensed.
Example 2:
The present embodiment provides a high bandwidth MEMS scanning mirror device 300, the high bandwidth MEMS scanning mirror device 300 being substantially identical to the other features of the high bandwidth MEMS scanning mirror device 300 of embodiment 1, except that:
In this embodiment, the mirror surface diameter of the micro-mirror 120 is 0.2 mm-1 mm, the mirror surface thickness of the micro-mirror 120 is 5 micrometers-50 micrometers, and N is 5 or more and 20 or less.
In the prior art, the MEMS scanning mirror device with a small-size mirror surface of 0.2-1 mm has the working mode eigenfrequency of about 1-2kHz, the scanning working bandwidth of 500-1000Hz under open-loop control and 4-8kHz under closed-loop control, and can meet the requirements of common application, but is difficult to meet the requirements of higher scanning working bandwidth, such as the high-speed MEMS optical switching technology with microsecond switching time.
According to the invention, the N value of the small-size micro-mirror 120 is set, so that the small-size micro-mirror 120 can meet the requirements of MEMS scanning mirror devices of small-size mirrors such as microsecond-level high-speed optical switches and the like while the torsional rigidity of the small-size micro-mirror 120 ensures the structural reliability and simultaneously maximizes the scanning working bandwidth which can be realized by the small-size micro-mirror 120.
In one embodiment, the high bandwidth MEMS scanning mirror device 300 is one of a MEMS high speed optical phase shifter array, a MEMS microsecond level high speed optical switch, or a MEMS microsecond level high speed optical switch array.
The optical path switching time of the existing MEMS optical switch and the array thereof can only reach about 1ms, and the optical circuit level switching can only be realized at present. The invention can realize high-efficiency optical switching of 10-100 mu s, even 10 mu s-1 mu s and efficiency up to 99% by applying the flexible torsion beam with reduced torsional rigidity in a microsecond optical switch or an optical switch array, and realize MEMS all-optical burst packet switching with large port number (256 multiplied by 256) with low optical loss (about 1-2 dB), and subvert the existing optical line level switching architecture to realize the quality change of the optical fiber communication network switching technology.
In one embodiment, the MEMS high-speed optical switch array is a dual-axis high-bandwidth MEMS scanning mirror device 300 comprising small-sized micro mirrors 120, wherein the high-bandwidth MEMS scanning mirror chip 100 comprises a plurality of micro mirrors 120 and corresponding structures such as flexible torsion beams thereof, driving structures 140 and angle sensing detection structures 150, and a plurality of micro mirrors 120 and corresponding structures thereof are arranged in a square array.
Example 3:
The present embodiment provides a high bandwidth MEMS scanning mirror device 300, the high bandwidth MEMS scanning mirror device 300 being substantially identical to the other features of the high bandwidth MEMS scanning mirror device 300 of embodiment 1, except that:
in this embodiment, the mirror surface diameter of the micro-mirror 120 is 3 mm-20 mm, the mirror surface thickness of the micro-mirror 120 is 50 μm-500 μm, and N is less than 5.
According to the invention, the N value of the large-size micro-mirror 120 is set, so that the large-size micro-mirror 120 can meet the requirements of torsional rigidity of the large-size micro-mirror 120 on structural reliability and simultaneously maximize the scanning working bandwidth which can be realized by the large-size micro-mirror 120, and the problem that the flexible torsion beam is broken or the reliability is poor due to too small torsional rigidity in the process of improving the working bandwidth is solved, thereby being beneficial to meeting the requirements of MEMS scanning mirror bandwidth and structural rigidity of the large-size mirror for applications such as fine tracking of space laser communication terminals, image stabilizers or laser pointing stabilizers of vehicle-mounted or airborne motion platforms and the like.
In one embodiment, the high bandwidth MEMS scanning mirror device 300 is one of a MEMS fast mirror, an image stabilizer, a laser pointing stabilizer, a high speed laser machining scanning mirror, or a high speed 3D laser printing scanning mirror.
As the mirror radius R increases, the moment of inertia I of the MEMS scanning mirror increases to the power of 4-5 of the mirror radius R, so that the working mode resonance frequency of the large-size mirror MEMS scanning mirror is sharply reduced, and when the mirror diameter increases to 10 mm, the working mode frequency of the MEMS scanning mirror is reduced to about 100-200 Hz; under the existing MEMS feedforward open-loop drive control technology, the working bandwidth of the large-size mirror MEMS scanning mirror can only reach 50-100Hz, the working bandwidth of the large-size mirror MEMS scanning mirror can only reach 400-800Hz by adopting closed-loop feedback control, and compared with a scanning mirror device of a small-size mirror, the working bandwidth is lower, and the requirement of the bandwidth larger than 1000Hz in the rapid scanning application cannot be met.
The invention greatly improves the scanning working bandwidth which can be realized by the large-size MEMS scanning mirror device by applying the flexible torsion beam with reduced torsional rigidity to the large-size MEMS scanning mirror device, and meets the requirement of the large-size mirror surface on the scanning working bandwidth.
In one embodiment, the MEMS fast mirror is a dual-axis high bandwidth MEMS scanning mirror device 300 that includes a large-sized micro mirror 120.
Example 4:
The present embodiment provides a high bandwidth MEMS scanning mirror device 300, the high bandwidth MEMS scanning mirror device 300 being substantially identical to the other features of the high bandwidth MEMS scanning mirror device 300 of embodiment 1, except that:
in this embodiment, the mirror surface diameter of the micro-mirror 120 is 1 mm-3 mm, and the mirror surface thickness of the micro-mirror 120 is 20 micrometers-200 micrometers, where N is equal to or greater than 4 and equal to or less than 15.
According to the invention, the N value of the middle-size micro-mirror 120 is set, so that the middle-size micro-mirror 120 can maximize the scanning working bandwidth which can be realized by the middle-size micro-mirror 120 while meeting the requirements of torsional rigidity to ensure the structural reliability, and the problem of flexible torsion beam fracture or poor reliability caused by too small torsional rigidity in the process of improving the working bandwidth is avoided.
Example 5:
the present embodiment provides a high bandwidth MEMS scanning mirror device 300, the high bandwidth MEMS scanning mirror device 300 being substantially identical to the other features of any one of the high bandwidth MEMS scanning mirror devices 300 of embodiments 1 or 3, except that:
In this embodiment, as shown in fig. 1 to 3, the high bandwidth MEMS scanning mirror chip 100 of the high bandwidth MEMS scanning mirror device 300 is a MEMS dual-axis scanning mirror chip, an electrostatic flat panel driver is used as a driving structure 140 to drive a micro mirror 120 of a silicon mirror to scan, a capacitive sensor is used as an angle sensing detecting structure 150 to detect the scanning angle of the micro mirror 120, and a moving frame 113 is used to connect the micro mirror 120 and a substrate 130, so as to realize dual-axis scanning of a single micro mirror 120; the high bandwidth MEMS scanning mirror device 300 is a MEMS fast mirror that has significant technical and cost advantages over conventional electromechanical fast mirrors.
In this embodiment, the high bandwidth MEMS scanning mirror chip 100 includes a flexible torsion beam, a micro mirror 120, a substrate 130, a driving structure 140, and an angle sensing detection structure 150; the flexible torsion beam includes an inner shaft torsion beam 111 and an outer shaft torsion beam 112, the driving structure 140 includes an inner shaft electrostatic flat driver and an outer shaft electrostatic flat driver, and the angle sensing detecting structure 150 includes an inner shaft scanning angle sensor and an outer shaft scanning angle sensor; the high bandwidth MEMS scanning mirror chip 100 further comprises a dynamic deformation buffer structure, a moving frame 113 and an electrode pad 133, wherein the dynamic deformation buffer structure comprises a buffer flexible supporting beam 115 and a flexible supporting microstructure 114, the flexible supporting microstructure 114 comprises an even number of buffer flexible supporting beams 114, which are symmetrically arranged by taking a scanning inner shaft 161 and a scanning outer shaft 162 as symmetry axes, one end of the flexible supporting microstructure 114 supports a micro-mirror 120, the other end of the flexible supporting microstructure is connected with the buffer flexible supporting beam 115, and meanwhile, the buffer flexible supporting beam 115 is connected with the inner shaft torsion beam 111; the substrate 130 and the MEMS wafer with the structures such as the flexible torsion beam and the micro-mirror 120 are bonded by adopting an Au-Si bonding-based MEMS bulk silicon process through an Au layer as a bonding layer 131.
According to the application requirement of the fine tracking of the space laser communication system, the key indexes of the MEMS fast reflecting mirror are as follows: 1) The diameter of the silicon mirror surface is 10mm; 2) Biaxial scan angle range ±2.6mrad (mechanical angle); 3) The biaxial scanning bandwidth is not less than 1kHz; 4) Scanning accuracy 1 μrad (mechanical angle); 5) Mirror surface shape accuracy λ/20 (measurement wavelength λ=632.8 nm); 6) The impact acceleration is greater than 500G (gravitational acceleration unit 1 g=10m/s 2).
According to the index requirement of the MEMS quick reflection mirror, the structure of the MEMS biaxial scanning mirror chip is designed as follows:
1) The diameter of the micro mirror 120 is 10mm; ti 50nm/Au 200nm is plated on the surface of the micro-reflector 120 to serve as an optical high-reflection film 121, and the reflectivity of infrared laser with the working wavelength of 1550nm is as high as 98.5%; in order to ensure that the micro mirror 120 reaches a high-precision static surface shape of lambda/20 and reduce dynamic deformation of the silicon mirror surface during high-speed scanning, the mirror surface thickness of the micro mirror 120 is 400 μm.
2) And a dynamic deformation buffer structure including a buffer flexible support beam 115 and a flexible support microstructure 114 is employed to greatly reduce dynamic motion deformation of the micromirror 120. The dynamic deformation buffer structure provides uniform mechanical support around the micro-mirror 120 and dynamic stress buffering, so as to greatly reduce the mirror surface dynamic deformation caused by high angular acceleration of the micro-mirror 120 during high-speed scanning. As shown in fig. 1, the flexible support microstructures 114 are 8 buffer flexible support beams 114, the beam length of the buffer flexible support beams 114 is 100 μm, the beam width is 15 μm, liang Hou μm, and the 8 buffer flexible support beams 114 are distributed at equal angular intervals in a radial manner at the center of the micro-mirror 120; wherein, there are 2 buffer flexible support beams 114 coaxial with the scan inner shaft 161, 2 buffer flexible support beams 114 coaxial with the outer scan shaft, and the other 4 buffer flexible support beams 114 are distributed along 4 directions forming 45 degrees with the scan inner shaft 161 and the scan outer shaft 162 respectively; one end of the flexible supporting microstructure 114 is connected with the micro-mirror 120, and the other end is connected with the buffer flexible supporting beam 115, so that uniform stress relief supporting of the micro-mirror 120 is realized, and the mirror surface of the micro-mirror 120 can still ensure high surface shape accuracy during high-speed scanning; the cushioning flexible support beam 115 has a ring structure with a ring width of 300 μm and a ring thickness of 400 μm.
3) As shown in fig. 1, the flexible torsion beam includes an inner shaft torsion beam 111 and an outer shaft torsion beam 112; the inner shaft torsion beams 111 have a beam length of 520 μm and a beam width of 28 μm and Liang Hou μm, and comprise two inner shaft torsion beams 111, wherein one end of each inner shaft torsion beam 111 is connected with the buffer flexible support beam 115, and the other end is connected with the moving frame 113, so that the support of the micro-mirror 120 and the dynamic deformation buffer structure is realized; the outer spindle twist beams 112 having a beam length of 520 μm and a beam width of 28 μm and Liang Hou μm comprise two outer spindle twist beams 112, and one end of each outer spindle twist beam 112 is connected to the moving frame 113 and the other end is connected to the substrate 130 around the high bandwidth MEMS scanning mirror chip 100.
4) The high bandwidth MEMS scanning mirror chip 100 is fabricated on a single crystal silicon substrate 130, the substrate 130 further comprising a perimeter substrate 134 around the high bandwidth MEMS scanning mirror chip 100. As shown in fig. 2, an insulating oxide layer 132 having a thickness of 2um is grown on a substrate 130; as shown in fig. 5, the 4 Au-material driving electrodes 141 of the driving structure 140 are arranged on the surface of the insulating oxide layer 132 in a central symmetry manner, the 4 driving electrodes 141 are fan-shaped patterns with the same size, the central angle (vertex angle) is 90 degrees, the radius of the fan shape is 4mm, the thickness of the Au-material driving electrode 141 is about 1 μm, linear insulating grooves 143 are arranged between two adjacent driving electrodes 141 for insulating isolation, each driving electrode 141 is led out from the corresponding linear insulating groove 143 to the electrode welding pad 133 of the high bandwidth MEMS scanning mirror chip 100 through one driving electrode lead 142 electrically connected with the driving electrode 141, and the driving electrode lead 142 is made of Au; the width of each linear insulation groove 143 is 100um, each driving electrode lead 142 is located on the central line of the linear insulation groove 143, the width of the driving electrode lead 142 is 20um, and the distance between the driving electrode lead 142 and the other sensing electrode 151 is 40um.
As shown in fig. 5, on the substrate 130, the outer periphery of the driving electrode 141, sensing electrodes 151 made of Au are arranged in a central symmetry manner, the 4 sensing electrodes 151 are in a quarter-circular pattern with the same size, the corresponding central angle is 90 °, the minimum distance between the inner diameter and the outer diameter of each circular ring is 0.9mm, the thickness of the sensing electrode 151 is about 1 μm, each sensing electrode 151 is led out to the electrode pad 133 of the high bandwidth MEMS scanning mirror chip 100 through one sensing electrode lead 152, and the width of the sensing electrode lead 152 is 50um. The adjacent Au driving electrodes 141 and Au sensing electrodes 151 are electrically isolated by the linear insulation grooves 143 and the circular insulation grooves 153, and the width of the circular insulation grooves 153 is 50um.
As shown in fig. 2-3, all the driving electrodes 141 and the sensing electrodes 151 are located right below the micro-mirror 120, and an air gap 170 is formed between the driving electrodes 141 and the sensing electrodes 151 and the micro-mirror 120; the air gap 170 has a height of 40um to avoid electrostatic plate driven Pull-in (Pull-in) effects. The mirror surface of the micro mirror 120 is grounded to constitute 4 driving plate capacitances together with the 4 driving electrodes 141 and 4 sensing plate capacitances together with the 4 sensing electrodes 151 as a common ground electrode.
5) The driving structure 140 of the high-bandwidth MEMS biaxial scanning mirror chip adopts an electrostatic flat-panel driver, which comprises an inner-axis electrostatic flat-panel driver and an outer-axis electrostatic flat-panel driver, to respectively drive the micro-mirror 120 around the scanning inner axis 161 and the scanning outer axis 162 to realize bidirectional (clockwise and anticlockwise) torsion scanning.
The inner shaft electrostatic flat panel driver includes two inner shaft electrostatic flat panel drivers arranged in pairs with a scanning inner shaft 161, constituting a differential type inner shaft electrostatic flat panel driver. The two inner shaft electrostatic flat plate drivers realize 'push-pull' electrostatic torsion driving under the driving of a bias DC power supply V0 (100V) and a programmable power supply V1 (bipolar, 60V), and electric signal control torsion scanning can be realized in both directions. In other words, the voltage value and polarity of the programmable power supply V1 can be controlled to control the magnitude and direction of the scanning angular acceleration (or positive and negative, assuming that the counterclockwise direction is positive and the clockwise direction is negative), so that the micro-mirror 120 can be controlled to be driven flexibly in a fully electrically controlled manner, and the micro-mirror 120 can be driven flexibly by the feedback control chip 230. When the voltage of the bipolar programmable power supply V1 is positive (i.e., positive), the inner-shaft electrostatic flat-panel driver is driven to twist counterclockwise around the scan inner shaft 161; similarly, when the voltage of the bipolar programmable power supply V1 is negative (i.e., negative), the inner-shaft electrostatic plate driver is driven to twist clockwise about the scan inner shaft 161. The magnitude of the electrostatic driving torque tau 1 of the inner shaft can be controlled by controlling the magnitude of the voltage value of the programmable power supply V1. The electrostatic inner shaft driving torque τ1 can be decomposed into two parts τ11, τ12, one part (τ11) is used to overcome the elastic rebound torque of the inner shaft torsion beam 111 (the driving torque overcomes an elastic rebound torque that linearly increases with the scanning angle, thus generating an angular acceleration curve that quickly decays from the initial angular acceleration to zero), and the other part (τ12) implements the accelerating torsion (the angular acceleration that increases/decreases the angular velocity of the micromirror 120 with dynamic deformation buffer structure) of the micromirror 120 around the inner shaft, that is, the angular acceleration scanning of the inner shaft increment, thereby accelerating the scanning motion of the micromirror 120, and implementing the high-speed scanning. It should be noted that, only a part of the torque of the inner-shaft electrostatic driving torque τ1 exceeding the rebound torque of the inner-shaft torsion beam 111 can be converted into the net angular acceleration (or negative angular acceleration) of the inner shaft of the micromirror 120, so that to achieve high-speed scanning, the inner-shaft electrostatic flat panel driver needs to provide a driving torque that is large enough to exceed the rebound torque of the inner-shaft torsion beam 111, thereby generating a scanning angular acceleration of the micromirror 120 that is large enough. This is significantly different from the driving technique of the existing MEMS scanning mirror in that the driving technique of the existing MEMS scanning mirror provides only the driving torque τ11, that is, the elastic rebound torque of the inner shaft torsion beam 111 corresponding to the specified scanning angle, as the driving torque. Of course, in order to ensure that the micromirror 120 reaches the specified scan angle position quickly and accurately, it is also necessary that the in-axis electrostatic flat panel drive is capable of providing sufficient negative angular acceleration (i.e., deceleration), and feedback control is used to ensure that the micromirror 120 does not overshoot or jitter after reaching the specified angular position, so as to obtain the maximum scan operating bandwidth, which is achieved by the feedback control chip 230.
The outer shaft electrostatic pad driver includes two outer shaft electrostatic pad drivers arranged in pairs with the scan outer shaft 162, constituting a differential outer shaft electrostatic pad driver. Under the drive of a bias DC power supply V0 (100V) and a programmable power supply V2 (bipolar, 60V), the two outer shaft electrostatic flat plate drivers realize electrostatic torsion drive of push-pull type, and torsion scanning controlled by electric signals can be realized in both directions. When the voltage of the bipolar programmable power supply V2 is positive, the outer shaft electrostatic flat-panel driver is driven to twist counterclockwise around the scan outer shaft 162; when the voltage of the bipolar programmable power supply V2 is negative, the outer shaft electrostatic pad driver is torsionally driven clockwise about the scan outer shaft 162. The magnitude of the outer shaft driving torque τ2 can be controlled by controlling the magnitude of the V2 voltage. The outer shaft driving torque τ2 can be decomposed into two parts τ21, τ22, one part (τ21) overcomes the elastic rebound torque of the outer shaft torsion beam 112, and the other part (τ22) implements the accelerating torsion of the micro mirror 120 (including the dynamic deformation buffer structure, the inner shaft torsion beam 111 and the moving frame 113 together) around the scanning outer shaft 162, that is, the accelerating scanning of the outer shaft angle. Likewise, only a partial torque of the electrostatic outer shaft driving torque τ2 exceeding the rebound torque of the outer shaft torsion beam 112 can be converted into an outer shaft angular acceleration (or negative angular acceleration) of the micromirror 120, thereby achieving high-speed scanning of the micromirror 120.
6) The dual-axis high bandwidth MEMS scanning mirror chip 100 employs a capacitive angle sensor to detect the scanning angle position in real time, including an inner axis scanning angle sensor and an outer axis scanning angle sensor, to detect the scanning angle values of the micro-mirror 120 around the scanning inner axis 161 and the scanning outer axis 162, respectively, so that real-time measurement of the bidirectional scanning angle values (assuming that the counterclockwise scanning angle is positive and the clockwise scanning angle is negative) can be achieved.
The inner shaft scanning angle sensor comprises two inner shaft scanning angle sensors which are symmetrically arranged by the scanning inner shaft 161, and forms a differential type inner shaft scanning angle sensor, and the design of the differential type scanning angle sensor can eliminate a large amount of common mode interference signals and improve the sensitivity by one time.
The outer shaft scanning angle sensor includes two outer shaft scanning angle sensors arranged in a pair of scanning outer shafts 162, and constitutes a differential inner shaft scanning angle sensor.
Example 6:
the present embodiment provides a design method of a high bandwidth MEMS scanning mirror device 300, the design method being used for designing the high bandwidth MEMS scanning mirror device 300 according to any one of embodiments 1 to 5, the design method comprising:
Calculating the maximum torque which can be provided to the micro-mirror 120 by the high bandwidth MEMS scanning mirror device 300 as tau according to the driving structure 140 and the driving voltage of the high bandwidth MEMS scanning mirror device 300 by a simulation tool, wherein the design target of the maximum scanning angle of the micro-mirror 120 of the high bandwidth MEMS scanning mirror device 300 is theta max;
Calculating the torsional stiffness K θ＝τ/(θmaxN2 of the flexible torsion beam of the high bandwidth MEMS scanning mirror device 300, N being a number greater than 1; a flexible torsion beam with a torsional stiffness of K θ is used as a torsional connection between the micro mirror 120 and the moving frame 113, between the moving frame 113 and the substrate 130 (the perimeter substrate 134) of the high bandwidth MEMS scanning mirror device 300.
In the prior art, the torsion rigidity of the flexible torsion beam is increased to improve torsion resilience force and acceleration during deceleration, but at the same time, the torsion initial acceleration is too high to cause rebound resistance, and acceleration during acceleration is limited, so that the whole scanning working bandwidth of the MEMS scanning mirror device is always limited and cannot be greatly improved, and when the torsion rigidity of the flexible torsion beam is increased to a certain degree, the scanning working bandwidth is limited and cannot be continuously improved, and the high requirement of the current high-speed scanning application scene on the scanning working bandwidth of the MEMS scanning mirror is difficult to meet.
The invention breaks through the conventional design method for improving the scanning working bandwidth of the MEMS scanning mirror, reversely reduces the torsional rigidity of the flexible torsion beam, solves the problem of limited acceleration of initial torsion acceleration caused by the increase of the torsional rigidity, adopts the bidirectional torsion driving to cooperate with the feedback control chip 230 to flexibly control the driving state in real time and high bandwidth feedback in the deceleration, improves the acceleration in the deceleration, and improves the acceleration in the acceleration and deceleration stages, thereby obviously improving the whole scanning working bandwidth of the MEMS scanning mirror device.
To illustrate the significant technical advantages of the design method of the high bandwidth MEMS scanning mirror device 300 of the present invention, in this embodiment, it is compared to the existing MEMS scanning mirror design method (the ordinary design method). In the following alignment of the design method, the micro-mirrors 120 are all silicon mirrors, the buffer structure is the dynamic deformation buffer structure described in embodiment 4, the driving structure 140 is an electrostatic driver, and the parameters of the silicon mirrors, the parameters of the buffer structure, the parameters of the electrostatic driver, the driving voltage, etc. are all unchanged, and the parameters are shown in table 1.
TABLE 1 microstructure parameters of high bandwidth MEMS scanning mirrors (without flexible torsion beams)
By setting the different sizes of the corresponding flexible torsion beams in the design scheme and the ordinary design scheme, the different torsional rigidity of the corresponding flexible torsion beams in the two schemes is obtained, the different driving torques required for obtaining the same static torsion angle are obtained, the different torsional working mode frequencies and the different scanning net angular accelerations of the flexible torsion beams are obtained, and the specific parameter difference pairs of the two schemes are shown in a table 2.
Table 2 comparison of the design scheme of this patent and the ordinary design scheme of MEMS scanning mirror flexible torsion beam structural parameters and scanning mirror electromechanical performance parameters
Specifically, the "ordinary design" of a MEMS scanning mirror is as follows:
1) According to the application requirements of the MEMS scanning mirror device, the design parameters shown in table 1 are obtained through the design of the electrostatic flat panel driver and the selection of a driving power supply, wherein the design parameters comprise the chip size, the microstructure technological parameters (limited by the existing MEMS processing technology), the driving mode and the driving signal size, and the maximum driving torque (torsion moment) tau max of the electrostatic driver of the MEMS scanning mirror device is 3.913 mu Nm through calculation and simulation, and the maximum driving torques of the inner shaft and the outer shaft are the same;
2) According to the index requirement of the angle scanning range (-2.6 mrad to +2.6mrad) of the MEMS scanning mirror, under the guidance of the design thought of 'maximally improving the working mode eigenfrequency' of the MEMS scanning mirror, the torsional rigidity of the flexible torsion beam of the MEMS scanning mirror is maximally improved in design, and the torsional rigidity of the inner shaft is as follows in the design torsional rigidity of the flexible torsion beam: k θ Inner part ＝τmax Inner part /θmax Inner part =1505 μnm/rad, the torsional stiffness of the outer shaft is: k θ Outer part ＝τmax Outer part /θmax Outer part =1505 μnm/rad;
3) According to a formula f 0＝(2π)-1(Kθ/I)1/2, wherein f 0 is the intrinsic frequency of a scanning working mode in an ordinary design, K θ is the torsional rigidity of a corresponding flexible torsion beam, I is the moment of inertia of the MEMS scanning mirror around a scanning axis, and the intrinsic frequency f 0 Inner part = 287.7Hz of an inner shaft scanning working mode of the MEMS scanning mirror and the intrinsic frequency f 0 Outer part =242.9 Hz of an outer shaft scanning working mode are obtained;
4) Through PID feedback control, the maximum possible driving torque is generated under the driving of the maximum possible driving voltage, and the maximum possible angular acceleration value is further generated, wherein the maximum working bandwidth is 4 times of the working mode frequency f 0, namely the maximum scanning working bandwidth of the inner shaft is 1150.8Hz, and the maximum scanning working bandwidth of the outer shaft is 971.4Hz.
The optimal design method according to the invention is as follows:
1) According to the application requirements of the high bandwidth MEMS scanning mirror device 300, and the design parameters as shown in table 1 obtained by the design of the electrostatic driver as the driving structure 140 and the selection of the driving power supply, the maximum driving torque τ max of the MEMS driver is calculated and simulated to be 3.913 μnm, the design parameters of the present scheme are the same as those of the "ordinary design" in table 1, so as to ensure that the two design schemes are the same as other irrelevant variables except for the study target variable related to torsional rigidity.
2) Taking n=2, the design torsional stiffness of the high bandwidth MEMS scanning mirror chip 100 is obtained
An inner shaft: k θ Inner part ( Optimization )＝τmax Inner part /(θmax Inner part ×N2)＝3.913μNm/(2.6mrad×22) =376 μnm/rad, corresponding inner shaft flexible torsion beam design parameters: a length of 520 μm, a width of 28 μm, and a thickness of 400 μm;
An outer shaft: k θ Outer part ( Optimization )＝τmax Outer part /(θmax Outer part ×N2)＝3.913μNm/(2.6mrad×22) =376 μnm/rad, corresponding outer shaft flexible torsion beam design parameters: a length of 520 μm, a width of 28 μm, and a thickness of 400 μm;
3) According to the formula f= (2pi) -1(Kθ/I)1/2, we get
The eigenfrequency of the in-axis scanning mode of operation of the high bandwidth MEMS scanning mirror chip 100: f Inner part ≈f0 Inner part /N＝f0 Inner part /2=143.8 Hz.
The outer axis scanning mode eigenfrequency of the high bandwidth MEMS scanning mirror chip 100: f Outer part ≈f0 Outer part /N＝f0 Outer part /2=115.9 Hz (a small difference in motion mass and radius due to the difference in torsional stiffness, which cannot be eliminated, results in a non-identical moment of inertia, resulting in a small variation of f in the present solution, not just half of f 0 in the ordinary design);
4) By PID feedback control, the maximum possible driving torque is generated under the driving of the maximum possible driving signal, and the maximum possible angular acceleration value is generated, and the scanning operation bandwidth is 4n=8 times of the modal frequency f 0 in the ordinary design, that is, the inner shaft scanning operation bandwidth is 2300Hz, the outer shaft scanning operation bandwidth is 1855Hz, and the scanning operation bandwidth of the high bandwidth MEMS scanning mirror chip 100 is increased by N times, and in this embodiment, by 2 times, relative to the "ordinary design".
According to the above-mentioned optimal design scheme of the patent, through the optimal design of the flexible torsion beam, in the embodiment, under the condition that the design constraint condition is unchanged, the working bandwidth of the high-bandwidth MEMS scanning mirror chip 100 is improved by 2 times compared with that of an MEMS scanning mirror with 'ordinary design', and the technical advantage of remarkable high-bandwidth scanning is shown.
In another preferred embodiment, taking n=3, the operating bandwidth of the high bandwidth MEMS scanning mirror chip 100 is improved by a factor of 3 over the "normally designed" MEMS scanning mirror.
In another preferred embodiment, taking n=4, the operating bandwidth of the high bandwidth MEMS scanning mirror chip 100 is increased by a factor of 4 relative to a MEMS scanning mirror of "ordinary design".
It should be noted that, the value of N has a limit, and the limit of the value of N depends on the technical requirements of the working scenario of the high bandwidth MEMS scanning mirror device 300 on the device for anti-vibration, because as the value of N increases, the beam width of the flexible torsion beam is properly narrowed, or the beam length is properly lengthened, or both the beam width is properly narrowed and the beam length is properly lengthened. On the premise of meeting the application requirements of the device, the value of N is preferably 2-5, and in the embodiment, the silicon mirror surface has larger size (the mirror surface diameter is 10 mm) and thick thickness (the mirror surface layer thickness is 400 μm), and the value of N cannot be too large; if the silicon mirror is small in size (mirror diameter is about 1 mm) and thin in thickness (mirror thickness is 20-30 μm), the range of N can be extended to 5-20, and specific N can be selected by referring to the range of the corresponding mirror sizes in examples 1-4.
In summary, the high-bandwidth MEMS scanning mirror device and the design method thereof can reduce the torsional rigidity of the flexible torsion beam to 1/N 2 of the conventional design torsional rigidity tau/theta max so as to improve the acceleration of the micro-mirror during torsional acceleration, and cooperate with the feedback control of the bidirectional torsional driving and feedback control chip on the torsional motion state to improve the acceleration of the micro-mirror during torsional deceleration, avoid overshoot caused by overlarge torsional amplitude of the scanning mirror, and greatly improve the scanning working bandwidth which can be realized by the scanning mirror device; simultaneously, torsional rigidity of different degrees is reduced through the micro-reflectors with different sizes, so that the structural strength of the micro-reflectors is ensured, and the optimization of the scanning working bandwidth is realized; in addition, the PID algorithm is utilized to carry out torsion feedback control on the micro-mirror, so that the achievable scanning working bandwidth is further improved; finally, by reducing the torsional rigidity of the torsion beam instead of the conventional mode of increasing the torsional rigidity, the working bandwidth is increased by matching with feedback control, the design thinking inertia of the MEMS scanning mirror device for increasing the bandwidth is broken, and the remarkable effect of greatly increasing the scanning working bandwidth of the MEMS scanning mirror device is generated.
Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.
The above embodiments are merely illustrative of the principles of the present invention and its effectiveness, and are not intended to limit the invention. Modifications and variations may be made to the above-described embodiments by those skilled in the art without departing from the spirit and scope of the invention. Accordingly, it is intended that all equivalent modifications and variations of the invention be covered by the claims, which are within the ordinary skill of the art, be within the spirit and scope of the present disclosure.

Claims (10)

1. A high bandwidth MEMS scanning mirror device, the high bandwidth MEMS scanning mirror device comprising: the high-bandwidth MEMS scanning mirror chip, the power supply driving chip, the angle sensing detection circuit chip, the feedback control chip and the input/output connector;
The high-bandwidth MEMS scanning mirror chip comprises a flexible torsion beam, a micro-mirror, a substrate, a driving structure and an angle sensing detection structure, wherein torsion connection is formed between the micro-mirror and the substrate through the flexible torsion beam, the driving structure controls the micro-mirror to perform torsion motion relative to the substrate, and the angle sensing detection structure is used for detecting the real-time torsion angle of the micro-mirror; the maximum torque that the driving structure can provide for the micro-mirror is tau, the torsional rigidity K θ＝τ/(θmaxN2 of the flexible torsion beam when the maximum scanning angle of the micro-mirror is theta max,
N is a number greater than 1;
The power supply driving chip is electrically connected with the driving structure to control the driving state of the driving structure on the micro-reflecting mirror; the angle sensing detection circuit chip is electrically connected with the angle sensing detection structure to receive and process the real-time torsion angle of the micro-mirror detected by the angle sensing detection structure to obtain a real-time angle signal; the input/output connector is electrically connected with the external control system to receive a target angle signal input by the external control system; the feedback control chip is electrically connected with the angle sensing detection circuit chip, the power supply driving chip and the input/output connector, so as to receive the real-time angle signal calculated by the angle sensing detection circuit chip and the target angle signal received by the input/output connector, obtain an adjustment closed-loop feedback driving signal through processing of a preset high-bandwidth feedback control algorithm, transmit the adjustment closed-loop feedback driving signal to the power supply driving chip, control the driving structure to drive the driving state of the micro-mirror through the power supply driving chip, and control the driving structure to drive the micro-mirror to twist in a bidirectional manner through the power supply driving chip.
2. The high bandwidth MEMS scanning mirror device according to claim 1, wherein the high bandwidth MEMS scanning mirror chip comprises M micro-mirrors arranged in an array, each micro-mirror having a corresponding flexible torsion beam, driving structure, and angle sensing detection structure, M micro-mirrors being on the same substrate, M being an integer greater than or equal to 1.
3. The high bandwidth MEMS scanning mirror device according to claim 1, wherein the preset high bandwidth feedback control algorithm employed by the feedback control chip is a PID algorithm, and the real time angle signal and the target angle signal are processed by the PID algorithm to generate the adjusted closed loop feedback drive signal.
4. A high bandwidth MEMS scanning mirror device according to any of claims 1-3, wherein N is greater than or equal to 1.1 and less than or equal to 20.
5. The high bandwidth MEMS scanning mirror device according to claim 4, wherein the micro-mirrors have a mirror diameter of 0.2 mm to 1mm, and the micro-mirrors have a mirror thickness of 5 μm to 50 μm, and N is 5 or more and 20 or less.
6. The high bandwidth MEMS scanning mirror device according to claim 5, wherein the high bandwidth MEMS scanning mirror device is one of a MEMS high speed optical phase shifter array, a MEMS microsecond level high speed optical switch, or a MEMS microsecond level high speed optical switch array.
7. The high bandwidth MEMS scanning mirror device according to claim 4, wherein the micro-mirrors have a mirror diameter of 3 mm to 20mm, and the micro-mirrors have a mirror thickness of 50 μm to 500 μm, and N is less than 5.
8. The high bandwidth MEMS scanning mirror device according to claim 7, wherein the high bandwidth MEMS scanning mirror device is one of a MEMS fast mirror, an image stabilizer, a laser pointing stabilizer, a high speed laser machining scanning mirror, or a high speed 3D laser printing scanning mirror.
9. The high bandwidth MEMS scanning mirror device according to claim 4, wherein the micro-mirrors have a mirror diameter of 1mm to 3mm, and the micro-mirrors have a mirror thickness of 20 μm to 200 μm, and N is equal to or greater than 4 and equal to or less than 15.
10. A method of designing a high bandwidth MEMS scanning mirror device according to any one of claims 1-9, the method comprising:
According to the driving structure and the driving voltage of the high-bandwidth MEMS scanning mirror device, calculating the maximum torque which can be provided for the micro-mirror by the high-bandwidth MEMS scanning mirror device as tau through a simulation tool, wherein the design target of the maximum scanning angle of the micro-mirror of the high-bandwidth MEMS scanning mirror device is theta max;
Calculating the torsional rigidity K θ＝τ/(θmaxN2 of the flexible torsion beam of the high-bandwidth MEMS scanning mirror device, wherein N is a number larger than 1; a flexible torsion beam with a torsional stiffness of K θ is used as a torsional connection between the micro-mirror and the substrate of the high bandwidth MEMS scanning mirror device.
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