Grating scanning correction method and system for electromagnetic MEMS micromirror

Abstract

The invention discloses a raster scanning correction method and system for an electromagnetic MEMS micromirror, and belongs to the technical field of raster scanning correction, and the method comprises the steps: collecting the real-time three-axis attitude information of an electromagnetic MEMS micromirror product in a three-dimensional space, and the fast and slow axis piezoresistive signals of the micromirror; carrying out PID control by taking the angle difference value as an error signal, outputting a driving voltage of a fast axis and a slow axis of the MEMS micro-mirror after the scanning view field correction, and further mapping to obtain a correction angle of micro-mirror scanning; and taking the correction angle as the input of PID control, and correcting the rotation angle of the micromirror by minimizing the tracking error between the rotation angle of the micromirror and the correction angle. Three-axis attitude information of an electromagnetic MEMS micro-mirror product is collected, and an angle difference value between the three-axis attitude information and standard three-axis attitude information is introduced into PID control to adjust a fast-slow axis driving signal, so that the rotation angle of the micro-mirror is corrected, and correction and compensation of grating distortion in grating scanning are realized. And the accuracy of the reconstruction quality of the three-dimensional point cloud is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of grating scanning correction, and in particular to a grating scanning correction method and system for an electromagnetic MEMS micromirror. Background Art

[0002] MEMS micromirrors can be used in high-precision optoelectronic systems such as OCT (optical endoscopic imaging), spectrometers, and lidar. The micromirrors are driven to rotate by electrical signals of specific voltage, frequency, and waveform. Position detection or open / closed-loop control is used to obtain the motion information of the micromirrors and then obtain calibration data, maintain stable operation of the micromirrors, or compensate for the motion of the micromirrors.

[0003] Electromagnetic actuation (EM) is to prepare a conductive micro-coil on the structure of a MEMS micro-mirror. When the magnitude and direction of the current in the micro-coil are changed, the Ampere force generated by the interaction with the externally packaged permanent magnetic material can move the driving structure of the micro-mirror and achieve mirror deflection. The micro-mirror prepared by this principle is called an electromagnetic MEMS micro-mirror. Electromagnetic actuation can provide a large driving force, so that the micro-mirror has a large range and large angle dual-axis scanning while taking into account a large mirror size. In addition, electromagnetic actuation also has the advantages of high linearity and low driving voltage.

[0004] Raster scanning is a common scanning method for electromagnetic MEMS micromirrors. When working in this state, the fast axis should be in a resonant state and the slow axis should be in a quasi-static state. At this time, a sine wave signal should be applied to the fast axis and a triangular wave signal should be applied to the slow axis. The fast axis voltage signal and the slow axis voltage signal should be continuously collected. The voltage parameters of the subsequent output drive signal and other information are calculated according to the relationship between the fast and slow axis voltage signals and the micromirror rotation angle to achieve regulation and control, so as to achieve efficient beam deflection and precise scanning control. When the MEMS micromirror scanning system is applied to laser radar or other devices (electromagnetic MEMS micromirror products), the laser radar or other devices are prone to offset in three-dimensional space due to external environment or mobile scanning. At this time, the grating shape of the electromagnetic MEMS micromirror for two-dimensional scanning of the laser will cause different degrees of distortion of the scanning grating due to different degrees of offset. The distortion of the grating will affect the reconstruction quality of the three-dimensional point cloud. Therefore, how to correct the offset of the MEMS micromirror in three-dimensional space is an urgent problem to be solved. Summary of the invention

[0005] The purpose of the present invention is to overcome the problems of the prior art and to provide a grating scanning correction method and system for an electromagnetic MEMS micromirror.

[0006] The object of the present invention is to achieve the following technical solution: a grating scanning correction method for an electromagnetic MEMS micromirror, the method comprising the following steps:

[0007] Collect the real-time three-axis attitude information of the electromagnetic MEMS micromirror product in three-dimensional space, including real-time pitch angle information and real-time yaw angle information; at the same time, collect the fast and slow axis piezoresistance signals of the micromirror, and then calculate the rotation angle of the micromirror;

[0008] The angle difference between the real-time three-axis posture information and the standard three-axis posture information is calculated to determine whether the angle difference is within a first threshold range. If not, PID control is performed using the angle difference as an error signal to output the driving voltage of the fast and slow axes of the MEMS micromirror after the scanning field of view is corrected, and the corrected angle of the micromirror scanning is obtained according to the driving voltage mapping of the fast and slow axes; the corrected angle is used as the input of the PID control to minimize the tracking error between the rotation angle of the micromirror and the corrected angle, thereby correcting the rotation angle of the micromirror.

[0009] In one example, after the rotation angle of the micromirror is corrected, the method further includes:

[0010] Determine the left and right deviation directions according to the real-time yaw angle, and when the right deviation occurs, apply a first positive bias voltage to the driving signal of the fast axis; when the left deviation occurs, apply a first negative bias voltage to the driving signal of the fast axis;

[0011] The up and down offset directions are determined according to the real-time pitch angle. When the deflection is upward, a second positive bias voltage is applied to the driving signal of the slow axis; when the deflection is downward, a second negative bias voltage is applied to the driving signal of the slow axis.

[0012] In one example, the first positive bias voltage and the first negative bias voltage are determined according to the real-time yaw angle increment size, and the second positive bias voltage and the second negative bias voltage are determined according to the real-time pitch angle increment size.

[0013] In one example, after the rotation angle of the micromirror is corrected or the bias voltage is applied, the method further includes:

[0014] The up and down offset directions are determined according to the real-time pitch angle. When the deflection is upward, the voltage of the positive half-cycle of the slow-axis drive signal is intercepted, so that the slow-axis drive signal remains in a non-driven state between the first interception voltage and the positive peak voltage; when the deflection is downward, the voltage of the negative half-cycle of the slow-axis drive signal is intercepted, so that the slow-axis drive signal remains in a non-driven state between the second interception voltage and the negative peak voltage.

[0015] In one example, the first clipping voltage and the second clipping voltage are determined according to the size and direction of the increment of the pitch angle.

[0016] In one example, the fitting relationship between the driving voltage of the fast axis and the rotation angle of the micromirror is:

[0017] D fast =0.93V fast3 +6.34V fast 2 +20V fast +0.88;

[0018] Among them, D fast is the fast axis rotation angle, V fast is the fast axis driving voltage.

[0019] In one example, the fitting relationship between the slow axis pressure driving voltage and the micromirror rotation angle is:

[0020] D slow =6.15V slow +0.82;

[0021] Among them, D slow is the slow axis rotation angle, V slow is the slow axis driving voltage.

[0022] In one example, the fast and slow axes of the electromagnetic MEMS micromirror share the same driving electrode, and the driving signal of the fast axis and the driving signal of the slow axis are amplified, summed and superimposed before being input into the driving electrode of the MEMS micromirror.

[0023] It should be further explained that the technical features corresponding to the above-mentioned method examples can be combined or replaced with each other to form a new technical solution.

[0024] The present invention also includes a grating scanning correction system of an electromagnetic MEMS micromirror, the system comprising:

[0025] A three-axis attitude information acquisition unit is used to acquire real-time three-axis attitude information of the electromagnetic MEMS micromirror product in three-dimensional space, including real-time pitch angle information and real-time yaw angle information;

[0026] The piezoresistive voltage acquisition unit is used to collect the fast and slow axis piezoresistive signals of the micromirror and feed them back to the main control unit, so that the main control unit can calculate the rotation angle of the micromirror according to the fast and slow axis piezoresistive signals of the micromirror;

[0027] The main control unit is used to calculate the angle difference between the real-time three-axis posture information and the standard three-axis posture information, determine whether the angle difference is within a first threshold range, and if not, use the angle difference as an error signal to perform PID control, output the driving voltage of the fast and slow axes of the MEMS micromirror after the scanning field correction, and obtain the corrected angle of the micromirror scanning according to the driving voltage mapping of the fast and slow axes; use the corrected angle as the input of the PID control, minimize the tracking error between the current rotation angle of the micromirror and the corrected angle, and correct the rotation angle of the micromirror.

[0028] In one example, the main control unit is connected to an operational amplifier summing circuit via a digital-to-analog conversion circuit, and the operational amplifier summing circuit is used to amplify, sum, and superimpose the fast-axis driving signal and the slow-axis driving signal, and output them to the driving electrode of the MEMS micromirror.

[0029] It should be further explained that the technical features corresponding to the above examples can be combined or replaced with each other to form a new technical solution.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. In one example, by collecting the three-axis posture information of the electromagnetic MEMS micromirror product, and introducing the angle difference between the three-axis posture information and the standard three-axis posture information into the PID control, the fast and slow axis drive signals are adjusted, and then the rotation angle of the micromirror is corrected, so as to realize the correction and compensation of the grating distortion of the grating scanning, and ensure the accuracy of the reconstruction quality of the three-dimensional point cloud.

[0032] 2. In one example, by applying a bias voltage to the fast and slow axis drive signals, the scanning field of view is made to appear as a regular rectangle, and the grating is further corrected, thereby further improving the reconstruction quality of the three-dimensional point cloud.

[0033] 3. In one example, by intercepting the peak-to-peak value of the fast and slow axis drive signals, the non-ROI area is no longer scanned, and only the area of ​​interest is scanned, thereby improving the scanning resolution and efficiency, and further improving the reconstruction quality of the three-dimensional point cloud.

[0034] 4. In one example, the fast and slow axes of the electromagnetic MEMS micromirror share the same driving electrode. Compared with designing independent driving electrodes for the fast and slow axes respectively, the MEMS micromirror structure of the present application is simpler, which can reduce the peripheral size of the micromirror and reduce cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The specific implementation methods of the present invention are further described in detail below in conjunction with the accompanying drawings. The accompanying drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The same reference numerals are used in these drawings to represent the same or similar parts. The schematic embodiments of the present application and their descriptions are used to explain the present application and do not constitute improper limitations on the present application.

[0036] Figure 1 A method flow chart provided for an example of the present invention;

[0037] Figure 2 A schematic diagram of an IMU angle provided for an example of the present invention;

[0038] Figure 3 A piezoresistive sensor schematic diagram provided for an example of the present invention;

[0039] Figure 4 A schematic diagram of the mapping relationship between the fast-axis piezoresistive feedback voltage and the scanning angle provided in an example of the present invention;

[0040] Figure 5 A schematic diagram of the mapping relationship between the slow-axis piezoresistive feedback voltage and the scanning angle provided in an example of the present invention;

[0041] Figure 6 A schematic diagram of a mapping relationship between a fast axis driving voltage and a scanning angle provided for an example of the present invention;

[0042] Figure 7 A schematic diagram of a mapping relationship between a slow axis driving voltage and a scanning angle provided for an example of the present invention;

[0043] Figure 8 A schematic diagram of a test scenario provided for an example of the present invention;

[0044] Fig. 9 A schematic diagram of a target field of view provided for an example of the present invention;

[0045] Fig.10 A schematic diagram of a distortion situation provided for an example of the present invention;

[0046] Fig.11 A PID control block diagram for voltage amplitude regulation provided by an example of the present invention;

[0047] Fig.12 A schematic diagram of the fields of view of four distorted fields of view provided in an example of the present invention after being adjusted by PID control;

[0048] Fig.13 A fast axis drive signal analysis diagram provided for an example of the present invention;

[0049] Fig.14 A slow axis driving signal analysis diagram provided for an example of the present invention;

[0050] Fig.15 A schematic diagram of a mapping relationship between a yaw angle and a bias voltage provided for an example of the present invention;

[0051] Fig.16 A schematic diagram of a mapping relationship between a pitch angle and a bias voltage provided for an example of the present invention;

[0052] Fig.17 A schematic diagram of the field of view after bias voltage correction provided by an example of the present invention;

[0053] Fig.18 A schematic diagram of the voltage regulation principle provided for an example of the present invention;

[0054] Fig.19A schematic diagram of a mapping between a pitch angle and a cutoff voltage provided for an example of the present invention;

[0055] Fig. 20 A schematic diagram of a field of view after correction of the intercept voltage provided by an example of the present invention;

[0056] Fig.21 A method flow chart provided for a preferred example of the present invention;

[0057] Fig. 22 A principle block diagram of a driving subsystem of an electromagnetic MEMS micromirror provided as an example of the present invention;

[0058] Fig.23 A schematic diagram of a MEMS fast-axis drive digital-to-analog conversion circuit provided as an example of the present invention;

[0059] Fig.24 A schematic diagram of a MEMS slow axis drive digital-to-analog conversion circuit provided as an example of the present invention;

[0060] Fig.25 A schematic diagram of an operational amplifier summing circuit provided as an example of the present invention;

[0061] Fig.26 A schematic diagram of a fast axis feedback signal instrument amplifier circuit provided for an example of the present invention;

[0062] Fig. 27 A schematic diagram of a slow axis feedback signal instrument amplifier circuit provided as an example of the present invention. DETAILED DESCRIPTION

[0063] The technical solution of the present invention is described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0064] In the description of the present invention, it should be noted that the directions or positional relationships indicated by "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc. are directions or positional relationships based on the drawings, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the use of ordinal numbers (e.g., "first and second", "first to fourth", etc.) is to distinguish objects, and is not limited to this order, and cannot be understood as indicating or implying relative importance.

[0065] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0066] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0067] In one example, if Figure 1 As shown, a grating scanning correction method for an electromagnetic MEMS micromirror comprises the following steps:

[0068] S10: Collect the real-time three-axis attitude information of the electromagnetic MEMS micromirror product in three-dimensional space, including real-time pitch angle information and real-time yaw angle information; at the same time, collect the fast and slow axis piezoresistance signals of the micromirror, and then calculate the rotation angle of the micromirror.

[0069] Among them, the electromagnetic MEMS micromirror product is a product (device, equipment, system, etc.) integrated with an electromagnetic MEMS micromirror, such as a MEMS laser radar, a grating scanning imaging device, a grating industrial camera, a grating spectrometer, etc., and some of the electromagnetic MEMS micromirror products in the specific embodiments of the present invention are MEMS laser radars. For the electromagnetic MEMS micromirror driving subsystem, it generally includes a main control unit, a digital-to-analog conversion circuit, and an operational amplifier circuit connected in sequence, which provide driving signals for the fast-axis driving electrode and the slow-axis driving electrode respectively. The digital-to-analog conversion circuit and the operational amplifier circuit are both provided with two paths, and the output ends of the two operational amplifier circuits are respectively connected to the fast-axis driving electrode and the slow-axis driving electrode. The driving signal is sent through the main control unit, including a sine wave signal applied to the fast axis and a triangular wave signal applied to the slow axis. The sine wave signal and the triangular wave signal are output to the fast-axis driving electrode and the slow-axis driving electrode after digital-to-analog conversion and amplification processing, and the MEMS micromirror is controlled to scan or deflect in the horizontal direction and the vertical direction. Optionally, the fast and slow axes of the electromagnetic MEMS micromirror of the present invention share the same driving electrode, and the driving signal of the fast axis (sine wave driving signal) and the driving signal of the slow axis (triangular wave driving signal) are amplified, summed and superimposed before being input to the driving electrode of the MEMS micromirror. The fast and slow axes of the electromagnetic MEMS micromirror share the same driving electrode. Compared with designing independent driving electrodes for the fast and slow axes respectively, the MEMS micromirror structure of the present application is simpler, the peripheral size of the mirror surface of the micromirror can be reduced, and the cost can also be reduced.

[0070] Furthermore, the present invention uses an inertial measurement unit (IMU) to measure the three-axis attitude angle (or angular rate) and acceleration of the MEMS laser radar. Generally, an IMU contains three single-axis accelerometers and three single-axis gyroscopes. The accelerometer detects the acceleration signal of the MEMS laser radar in the carrier coordinate system in three independent axes, and the gyroscope detects the angular velocity signal of the MEMS laser radar relative to the navigation coordinate system, thereby measuring the angular velocity and acceleration of the MEMS laser radar in three-dimensional space. The three attitude angles are pitch angle Pitch, roll angle Roll, and yaw angle Yaw, such as Figure 2 As shown, the present invention mainly uses the pitch angle Pitch and yaw angle Yaw information provided by the IMU to correct the distortion of the scanning grating of the MEMS micromirror.

[0071] Furthermore, the piezoresistive voltage of the fast and slow axes is collected by the piezoresistive sensor, and the motion state of the micromirror is fed back to the main control unit according to the relationship between the piezoresistive voltage and the rotation angle of the micromirror for subsequent control processing. Figure 3 As shown in the figure, the piezoresistive sensor in this example is implemented based on a Wheatstone bridge. When the micromirror rotates, the piezoresistive voltage will change, and then the rotation angle (scanning angle) of the micromirror will be fed back through the piezoresistive voltage. Under the external bias voltage, the output voltage of the Wheatstone bridge reflects the angle information of the micromirror movement. The amplitude of the fast and slow axis piezoresistive signal fed back corresponds to the deflection angle of the MEMS micromirror. Figure 4 and Figure 5 As shown. More specifically, by collecting the piezoresistive voltage signal (piezoresistive signal) of the MEMS micromirror, the piezoresistive voltage signal reflects the movement angle of the micromirror, and the collected piezoresistive voltage signal is amplified. According to the relationship between the piezoresistive voltage of the micromirror and the scanning angle, the scanning angle of the micromirror is analyzed, and the real-time input is processed in the main control unit, and the voltage amplitude of the subsequent output drive signal is negatively feedbacked and controlled in real time, so as to compensate the micromirror drive signal and stabilize the scanning angle of the micromirror. According to the mapping relationship between the fast and slow axis piezoresistive signals and the scanning angle, the fast and slow axis piezoresistive sensitivities of the electromagnetic micromirror can be obtained by linear fitting. In this example, the fast axis piezoresistive sensitivity of the electromagnetic micromirror is 12.35mV / V°, and the slow axis piezoresistive sensitivity of the electromagnetic micromirror is: 11.40mV / V°.

[0072] Alternatively, if Figure 6 As shown, the fast axis driving voltage and the micromirror rotation angle are further fitted, and the fitting relationship is:

[0073] D fast =0.93V fast 3 +6.34V fast 2 +20V fast +0.88

[0074] Among them, D fast is the fast axis rotation angle, V fast is the fast axis driving voltage.

[0075] Alternatively, if Figure 7 As shown, the slow axis pressure driving voltage and the micromirror rotation angle are further fitted, and the fitting relationship is:

[0076] D slow =6.15V slow +0.82

[0077] Among them, D slow is the slow axis rotation angle, V slow is the slow axis driving voltage.

[0078] S20: Calculate the angle difference between the real-time three-axis posture information and the standard three-axis posture information, determine whether the angle difference is within the first threshold range, if not, use the angle difference as an error signal for PID control, output the driving voltage of the fast and slow axes of the MEMS micromirror after the scanning field correction, and obtain the corrected angle of the micromirror scanning according to the driving voltage mapping of the fast and slow axes; use the corrected angle as the input of the PID control to minimize the tracking error between the rotation angle of the micromirror and the corrected angle, and then correct the rotation angle of the micromirror. Among them, the first threshold range can be set according to user needs, for example, it can be set to 0-0.1°. When the angle difference between the real-time three-axis posture information and the standard three-axis posture information is not within the first threshold range, the laser radar has a more serious offset, and the grating scan has a more serious distortion, and correction processing is required at this time.

[0079] Specifically, when the LiDAR is working, the hardware circuit drives the pulsed laser emission and the MEMS micromirror to perform two-dimensional scanning normally. The scene diagram is as follows: Figure 8 As shown in the figure, the MEMS micromirror emits a rectangular laser dot matrix. The area in the red box is the ROI (Region of Interest). Fig. 9As shown, at this time, the three-axis attitude information of the laser radar is the standard three-axis attitude information, that is, the standard three-axis attitude information is the three-axis attitude information when the MEMS laser radar is not offset in the three-dimensional space. The standard three-axis attitude information can be the three-axis attitude information after the initial correction, or it can be the three-axis attitude information after the last correction, such as the three-axis attitude information after calibration at the previous moment. When the laser radar produces an offset in the three-dimensional space due to the external environment or during the mobile scanning process, the scanned grating will be distorted. The present invention mainly adjusts the deflection amount of the pitch angle Pitch and the yaw angle Yaw. There are mainly four basic distortion conditions: pitch angle Pitch>0, that is, upward deviation occurs; pitch angle Pitch<0, ​​that is, downward deviation occurs; yaw angle Yaw>0, that is, right deviation occurs; yaw angle Yaw>0, that is, right deviation occurs; the scanning grating will have the following distortions: Fig.10 In this example, the fast and slow axis voltage amplitudes are adjusted by PID to correct the grating with trapezoidal distortion, thereby improving the quality of point cloud reconstruction.

[0080] At this time, the PID control sub-method for correcting the rotation angle of the micromirror includes:

[0081] S201: Get IMU angle information θ IMU , calculate the angle change (angle difference) Δθ = θ IMU -θ HOR ;

[0082] S202: Determine whether the angle change is within the first threshold range. If so, the laser radar is not offset and the grating scanning will not produce distortion. No correction is required and the entire correction process ends. If the angle change exceeds the first threshold range, execute step S203 for correction.

[0083] S203: The offset direction and deviation angle of the current field of view can be known according to the value of Δθ, e(k) is assigned a value according to Δθ, the micromirror fast and slow axis driving voltage after field of view correction is calculated through f[e(k)], and the micromirror scanning correction angle θ is obtained through the relationship between the driving voltage and the scanning angle. d Among them, e(k) is the error signal, which is defined as the difference between the standard pitch angle (standard three-axis attitude information) and the angle measured by the IMU. By mapping the error signal (angle deviation) to the control function f[e(k)], the change in the driving voltage that needs to be applied to the micromirror can be determined to compensate for the angle deviation. The calculation expression is as follows:

[0084]

[0085] Among them, V totalIndicates the sum of the fast and slow axis drive voltages required for this PID adjustment; V0 indicates the sum of the fast and slow axis drive voltages after the last PID adjustment. The PID algorithm calculates the control output of the error signal e(k) through three links: proportional (P), integral (I) and differential (D). The control output is used to adjust the drive voltage of the MEMS micromirror.

[0086] S204: Fig.11 As shown, the micromirror scan correction angle θ d As the input of the PID controller, the current rotation angle θ of the micromirror is the output, with the tracking error e = θ d -θ value as the PID controller parameters (proportional gain K p , integral gain K i , differential gain K d ) adjustment basis; when e = 0, the micromirror has reached the correction angle position θ d .

[0087] S205: Proportional gain K p , integral gain K i , differential gain K d Assign initial values ​​to K p0 , K i0 , K d0 ;

[0088] S206: The current micromirror rotation angle θ is fed back through the piezoresistive signal. According to e(k)=θ d -θ, for K p , K i , K d Correction is made, and the kth correction value is ΔK p(k) , ΔK i(k) , ΔK d(k) , so the corrected K p , K i , K d They are:

[0089] K p =K p0 +ΔK p(k)

[0090] K i =K i0 +ΔK i(k)

[0091] K d =K d0 +ΔK d(k)

[0092] S207: After k times of PID control adjustment, the micromirror rotation angle finally converges to the target position θd In this way, the grating field of view is corrected. The four distorted fields of view are adjusted by PID control as follows: Fig.12 shown.

[0093] In one example, after the rotation angle of the micromirror is corrected, the method further includes:

[0094] Determine the left and right deviation directions according to the real-time yaw angle, and when the right deviation occurs, apply a first positive bias voltage to the driving signal of the fast axis; when the left deviation occurs, apply a first negative bias voltage to the driving signal of the fast axis;

[0095] The up and down offset directions are determined according to the real-time pitch angle. When the deflection is upward, a second positive bias voltage is applied to the driving signal of the slow axis; when the deflection is downward, a second negative bias voltage is applied to the driving signal of the slow axis.

[0096] like Fig.12 As shown in the figure, the field of view after PID control adjustment can basically cover the target field of view, but the field of view still presents a trapezoid. In order to make the field of view present a regular rectangle (similar to the target field of view), this example adds bias voltage to the fast axis and slow axis drive signals to achieve the overall left or right shift of the horizontal scanning field of view, and also to achieve the overall upward or downward shift of the vertical scanning field of view. By adjusting in the opposite direction of the grating distortion direction, the grating correction is played. It is known that the fast axis is the axis of horizontal scanning, and the drive signal is a sine wave, such as Fig.13 As shown, the blue area is the left area of ​​the fast axis horizontal scan, and the yellow area is the right area of ​​the fast axis horizontal scan. The slow axis is the axis of vertical scan, and the driving signal is a triangular wave, such as Fig.14 As shown, the blue area is the upper area of ​​the slow axis vertical scanning, and the yellow area is the lower area of ​​the slow axis vertical scanning. When the yaw angle is deviated to the right, that is, the yaw angle is greater than 0, the first positive bias voltage is applied to the fast-axis driven sinusoidal signal to shift the overall scanning trajectory of the micromirror to the left; when the yaw angle is deviated to the left, that is, the yaw angle is less than 0, the first negative bias voltage is applied to the sinusoidal drive signal to shift the scanning trajectory to the right, thereby achieving the purpose of correction. Furthermore, the bias voltage (first positive bias voltage, first negative bias voltage) is determined according to the real-time yaw angle increment value, and the functional relationship is as shown below. Fig.15 As shown, the relationship between the bias voltage V and the yaw angle increment is expressed as:

[0097] V=0.028Δθ+6e -17

[0098] Furthermore, when the pitch angle is upward, that is, the pitch angle is greater than 0, a second negative bias voltage is applied to the triangular wave signal of the slow axis drive to move the overall scanning track of the micromirror downward. When the pitch angle is downward, that is, the pitch angle is less than 0, a second positive bias voltage is applied to the triangular wave drive signal to move the scanning track upward, thereby achieving the purpose of correction. Furthermore, the size of the bias voltage (second positive bias voltage, second negative bias voltage) depends on the size of the pitch angle increment, and the functional relationship is as follows: Fig.16 As shown in the figure, the relationship between the bias voltage and the pitch angle increment is expressed as:

[0099] V=-0.028Δθ-6e -17

[0100] The field of view corrected by the bias voltage (first positive bias voltage, first negative bias voltage, second positive bias voltage, second negative bias voltage) is as follows: Fig.17 shown.

[0101] In one example, after applying a bias voltage to a driving signal of a fast axis or a slow axis, the method further includes:

[0102] The up and down offset directions are determined according to the real-time pitch angle. When the deflection is upward, the voltage of the positive half-cycle of the slow-axis drive signal is intercepted, so that the slow-axis drive signal remains in a non-driven state between the first interception voltage and the positive peak voltage; when the deflection is downward, the voltage of the negative half-cycle of the slow-axis drive signal is intercepted, so that the slow-axis drive signal remains in a non-driven state between the second interception voltage and the negative peak voltage.

[0103] After adjusting the bias voltage, it is necessary to intercept the point cloud in the non-ROI area. The principle of interception in this example is to intercept the peak-to-peak value of the slow axis drive signal (triangle wave). Fig.18 As shown in FIG. 1 , when the peak voltage of the driving signal of the triangular wave is 2.5V and the reverse peak voltage is -2.5V, when the pitch angle increment changes, the driving signal after adding the bias voltage correction is intercepted again, so that the non-ROI area is not scanned. Specifically, when the pitch angle is greater than 0, that is, upward deflection, the voltage of the upper scanning area of ​​the triangular wave is intercepted, that is, at the first intercepted voltage V m The voltage between the peak voltage V and 2.5V is no longer driven, and the point cloud of this part cannot be generated. Similarly, when the pitch angle is less than 0, that is, downward, the voltage of the lower scanning area of ​​the triangle wave is intercepted, that is, at the second interception voltage V n If the voltage between the reverse peak voltage and -2.5V is no longer driven, the point cloud of this part cannot be generated. m 、V n The voltage value is determined by the size and direction of the pitch angle increment, such as Fig.19As shown, when the pitch angle increment is greater than 0, the upper intercept voltage (first intercept voltage) is:

[0104] V m =-0.069Δθ+2.5

[0105] When the pitch angle increment is less than 0, the lower cutoff voltage (second cutoff voltage) is:

[0106] V n =0.069Δθ-2.5

[0107] After processing by the intercept voltage method, the grating field of view is as follows Fig. 20 shown.

[0108] Combining the above examples, such as Fig.21 As shown, the grating scanning correction method of the present invention comprises the following steps:

[0109] S100: Collects real-time three-axis attitude information of electromagnetic MEMS micromirror products in three-dimensional space, including real-time pitch angle information and real-time yaw angle information; collects the fast and slow axis piezoresistance signals of the micromirror at the same time, and then calculates the rotation angle of the micromirror;

[0110] S200: Calculate the angle difference between the real-time three-axis posture information and the standard three-axis posture information, and determine whether the angle difference is 0. If not, use the angle difference as an error signal to perform PID control, output the driving voltage of the fast and slow axes of the MEMS micromirror after the scanning field correction, and obtain the corrected angle of the micromirror scanning according to the driving voltage mapping of the fast and slow axes; use the corrected angle as the input of PID control to minimize the tracking error between the rotation angle of the micromirror and the corrected angle, and then correct the rotation angle of the micromirror.

[0111] S300: Determine the left and right offset directions according to the real-time yaw angle, and when the vehicle is deflected to the right, apply a first positive bias voltage to the driving signal of the fast axis; when the vehicle is deflected to the left, apply a first negative bias voltage to the driving signal of the fast axis; determine the up and down offset directions according to the real-time pitch angle, and when the vehicle is deflected to the up, apply a second positive bias voltage to the driving signal of the slow axis; when the vehicle is deflected to the down, apply a second negative bias voltage to the driving signal of the slow axis; wherein the first positive bias voltage and the first negative bias voltage are determined according to the real-time yaw angle increment, and the second positive bias voltage and the second negative bias voltage are determined according to the real-time pitch angle increment;

[0112] S400: Determine the up and down offset directions according to the real-time pitch angle. When the deflection is upward, intercept the voltage of the positive half cycle of the slow axis drive signal, so that the slow axis drive signal remains in a non-driven state between the first interception voltage and the positive peak voltage; when the deflection is downward, intercept the voltage of the negative half cycle of the slow axis drive signal, so that the slow axis drive signal remains in a non-driven state between the second interception voltage and the negative peak voltage; wherein the first interception voltage and the second interception voltage are determined according to the size and direction of the pitch angle increment.

[0113] In this example, the voltage amplitudes of the fast and slow axes are adjusted in turn by PID, the corresponding bias voltage is added to the drive signal, and the drive signal voltage of the slow axis is intercepted, and then the grating scanning field displayed by the host computer point cloud software connected to the main control unit is used to determine whether the corrected grating meets the requirements. If it meets the requirements, the single correction is completed. If it does not meet the requirements, steps S200-S400 are repeated until it meets the requirements. The present invention adjusts the driving signal amplitude, applies bias voltage, and intercepts voltage through PID closed-loop control, which corrects and improves the trapezoidal distortion of the grating. The distortion caused by multi-angle deflection can be decomposed into the above-mentioned basic conditions through an algorithm for processing. The present invention has a good compensation effect on MEMS laser radar, grating scanning imaging, grating industrial camera, grating spectrometer and other fields.

[0114] The present invention also includes a grating scanning correction system for an electromagnetic MEMS micromirror, which has the same inventive concept as the grating scanning correction method formed by any one of the above examples or a combination of multiple examples. The system includes a main control unit, a three-axis attitude information acquisition unit connected to the main control unit, and a piezoresistive voltage acquisition unit. Among them, the three-axis attitude information acquisition unit is used to collect real-time three-axis attitude information of the electromagnetic MEMS micromirror product in three-dimensional space, including real-time pitch angle information and real-time yaw angle information. This example preferably uses an inertial measurement unit IMU. The piezoresistive voltage acquisition unit is used to collect the fast and slow axis piezoresistive signals of the micromirror and feed them back to the main control unit, so that the main control unit calculates the rotation angle of the micromirror based on the fast and slow axis piezoresistive signals of the micromirror; this example preferably uses a piezoresistive sensor based on a Wheatstone bridge. The main control unit is used to calculate the angle difference between the real-time three-axis posture information and the standard three-axis posture information, determine whether the angle difference is within the first threshold range, and if not, use the angle difference as an error signal to perform PID control, output the driving voltage of the fast and slow axes of the MEMS micromirror after the scanning field correction, and obtain the correction angle of the micromirror scanning according to the driving voltage mapping of the fast and slow axes; use the correction angle as the input of the PID control, minimize the tracking error between the current rotation angle of the micromirror and the correction angle, and correct the rotation angle of the micromirror. The main control unit can be an MCU, an FPGA, etc., and preferably the main control unit is also connected to a host computer.

[0115] In one example, the main control unit is connected to an operational amplifier summing circuit via a digital-to-analog conversion circuit, and the operational amplifier summing circuit is used to amplify, sum, and superimpose the fast-axis driving signal and the slow-axis driving signal, and output them to the driving electrode of the MEMS micromirror. Specifically, Fig. 22 As shown, the driving subsystem of the electromagnetic MEMS micromirror includes a main control unit MCU, a digital-to-analog conversion circuit DAC, and an operational amplifier summing circuit connected in sequence. The circuit principles of the digital-to-analog conversion circuit and the operational amplifier summing circuit are respectively as shown in FIG. Figure 23-Figure 25 As shown, the digital-to-analog conversion circuit includes a MEMS fast-axis drive digital-to-analog conversion circuit and a MEMS slow-axis drive digital-to-analog conversion circuit, and the operational amplifier summing circuit includes a reverse summing circuit, a low-pass filter circuit, and a voltage follower circuit. The drive subsystem also includes a piezoresistive sensor, which is connected to the main control unit MCU via a dual-channel instrumentation amplifier and an analog-to-digital conversion circuit ADC, as shown in FIG. Figure 26-Figure 27 As shown, the dual-channel instrument amplifier includes a fast-axis feedback signal instrument amplifier circuit and a slow-axis feedback signal instrument amplifier circuit. At this time, the digital signal of the drive signal required by the micromirror is sent through the MCU, and the digital drive signal is converted into an analog drive signal through the DAC. Because the voltage amplitude of the analog drive signal is not enough, it needs to be amplified by the post-stage amplifier circuit, and then the summation process is performed. The two drive signals are summed and superimposed, and then the superimposed analog drive signal is injected into the electrode of the MEMS micromirror for driving. At the same time, the ADC collects the piezoresistive voltage information of the fast and slow axes, and according to the relationship between the piezoresistive voltage and the rotation angle, the motion state of the micromirror is fed back to the MCU, which is convenient for subsequent control processing.

[0116] The above system examples are combined. At this time, the angle information fed back by the IMU inertial measurement unit can reflect the offset of the laser radar in the three-dimensional space. When the laser radar itself is offset, the grating shape scanned by the electromagnetic MEMS micromirror will be distorted, and the shape of the grating has a very important influence on the quality of point cloud reconstruction. The distorted grating shape cannot reconstruct the three-dimensional point cloud well. The present invention uses the angle information of the IMU to infer the offset of the laser radar in the three-dimensional space at this moment, and according to the influence of the offset on the degree of distortion of the grating shape, according to the offset position and offset size and the V-degree change relationship of the fast-axis and slow-axis drive signals, the driving signal of the electromagnetic MEMS micromirror is compensated and adjusted based on PID control, and the shape of the scanning grating is adjusted from the bias voltage method and the intercept voltage method, so as to compensate and correct the grating scanned by the micromirror.

[0117] The above specific implementation methods are detailed descriptions of the present invention. It cannot be determined that the specific implementation methods of the present invention are limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions and substitutions can be made without departing from the concept of the present invention, which should be regarded as belonging to the protection scope of the present invention.

Claims

1. A grating scanning correction method for an electromagnetic MEMS micromirror, characterized in that: The method comprises: Collect the real-time three-axis attitude information of the electromagnetic MEMS micromirror product in three-dimensional space, including real-time pitch angle information and real-time yaw angle information; at the same time, collect the fast and slow axis piezoresistance signals of the micromirror, and then calculate the rotation angle of the micromirror; The angle difference between the real-time three-axis posture information and the standard three-axis posture information is calculated to determine whether the angle difference is within a first threshold range. If not, PID control is performed using the angle difference as an error signal to output the driving voltage of the fast and slow axes of the MEMS micromirror after the scanning field of view is corrected, and the corrected angle of the micromirror scanning is obtained according to the driving voltage mapping of the fast and slow axes; the corrected angle is used as the input of the PID control to minimize the tracking error between the rotation angle of the micromirror and the corrected angle, thereby correcting the rotation angle of the micromirror.

2. The grating scanning correction method of the electromagnetic MEMS micromirror according to claim 1, characterized in that: After correcting the rotation angle of the micromirror, it also includes: Determine the left and right deviation directions according to the real-time yaw angle, and when the right deviation occurs, apply a first positive bias voltage to the driving signal of the fast axis; when the left deviation occurs, apply a first negative bias voltage to the driving signal of the fast axis; The up and down offset directions are determined according to the real-time pitch angle. When the deflection is upward, a second positive bias voltage is applied to the driving signal of the slow axis; when the deflection is downward, a second negative bias voltage is applied to the driving signal of the slow axis.

3. The grating scanning correction method of the electromagnetic MEMS micromirror according to claim 2, characterized in that: The first positive bias voltage and the first negative bias voltage are determined according to the real-time yaw angle increment, and the second positive bias voltage and the second negative bias voltage are determined according to the real-time pitch angle increment.

4. The grating scanning correction method of the electromagnetic MEMS micromirror according to claim 1, characterized in that: After correcting the rotation angle of the micromirror, it also includes: The up and down offset directions are determined according to the real-time pitch angle. When the deflection is upward, the voltage of the positive half-cycle of the slow-axis drive signal is intercepted, so that the slow-axis drive signal remains in a non-driven state between the first interception voltage and the positive peak voltage; when the deflection is downward, the voltage of the negative half-cycle of the slow-axis drive signal is intercepted, so that the slow-axis drive signal remains in a non-driven state between the second interception voltage and the negative peak voltage.

5. The grating scanning correction method of the electromagnetic MEMS micromirror according to claim 4, characterized in that: The first intercepting voltage and the second intercepting voltage are determined according to the size and direction of the increment of the pitch angle.

6. The grating scanning correction method of the electromagnetic MEMS micromirror according to claim 1, characterized in that: The fitting relationship between the fast axis driving voltage and the micromirror rotation angle is: <h2 style=";text-align:left;direction:ltr">D<h2 style=";text-align:left;direction:ltr"> fast <h2 style=";text-align:left;direction:ltr"> <0.93V<h2 style=";text-align:left;direction:ltr"> fast <h2 style=";text-align:left;direction:ltr"> 3 <h2 style=";text-align:left;direction:ltr"> +6.34V<h2 style=";text-align:left;direction:ltr"> fast <h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> +20V<h2 style=";text-align:left;direction:ltr"> fast <h2 style=";text-align:left;direction:ltr"> +0.88; Among them, D fast is the fast axis rotation angle, V fast is the fast axis driving voltage.

7. The grating scanning correction method of the electromagnetic MEMS micromirror according to claim 1, characterized in that: The fitting relationship between the slow axis pressure driving voltage and the micromirror rotation angle is: D slow =6.15V slow +0.82; Among them, D slow is the slow axis rotation angle, V slow is the slow axis driving voltage.

8. The grating scanning correction method of the electromagnetic MEMS micromirror according to claim 1, characterized in that: The fast and slow axes of the electromagnetic MEMS micromirror share the same driving electrode, and the driving signal of the fast axis and the driving signal of the slow axis are amplified, summed and superimposed before being input into the driving electrode of the MEMS micromirror.

9. A grating scanning correction system for an electromagnetic MEMS micromirror, characterized in that: The system comprises: A three-axis attitude information acquisition unit is used to acquire real-time three-axis attitude information of the electromagnetic MEMS micromirror product in three-dimensional space, including real-time pitch angle information and real-time yaw angle information; The piezoresistive voltage acquisition unit is used to collect the fast and slow axis piezoresistive signals of the micromirror and feed them back to the main control unit, so that the main control unit can calculate the rotation angle of the micromirror according to the fast and slow axis piezoresistive signals of the micromirror; The main control unit is used to calculate the angle difference between the real-time three-axis posture information and the standard three-axis posture information, and determine whether the angle difference is within a first threshold range. If not, the angle difference is used as an error signal for PID control, and the driving voltage of the fast and slow axes of the MEMS micromirror after the scanning field correction is output, and the corrected angle of the micromirror scanning is obtained according to the driving voltage mapping of the fast and slow axes; the corrected angle is used as the input of the PID control, and the tracking error between the current rotation angle of the micromirror and the corrected angle is minimized to correct the rotation angle of the micromirror.

10. The grating scanning correction system of the electromagnetic MEMS micromirror according to claim 9, characterized in that: The main control unit is connected to an operational amplifier summing circuit via a digital-to-analog conversion circuit. The operational amplifier summing circuit is used to amplify, sum, and superimpose the driving signal of the fast axis and the driving signal of the slow axis, and output them to the driving electrode of the MEMS micromirror.

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