Projection method and control circuit based on synchronous movement of electrostatic MEMS (Micro Electro Mechanical System) micromirror and laser

Abstract

The invention discloses a projection method and control circuit based on synchronous movement of an electrostatic MEMS micromirror and a laser, the projection method and control circuit are applied to an LBS projection system, the system adopts a two-dimensional electrostatic resonant MEMS micromirror and a laser, and the method comprises the following steps: generating a fast-axis driving square wave and a slow-axis driving square wave, performing simultaneous frequency sweeping, and outputting the fast-axis driving square wave and the slow-axis driving square wave after frequency sweeping; respectively driving a fast axis and a slow axis of the two-dimensional electrostatic resonant MEMS micromirror to move based on the fast axis driving square wave and the slow axis driving square wave after frequency sweeping; respectively applying a first light emitting delay and a second light emitting delay to the fast axis driving square wave and the slow axis driving square wave to realize synchronous movement of the laser, the fast axis and the slow axis; finding the positions of the fast-axis light-emitting point and the slow-axis light-emitting point at the same moment for the first time, and determining the positions as projection starting points; the number of projection points is preset, and projection is performed from the projection starting point in sequence according to the scanning track. The LBS projection system has the remarkable advantages of being high in frame rate, large in field angle, small in size, low in power consumption and high in mechanical stability.

Description

Technical Field

[0001] The present invention relates to the field of augmented reality display technology, and in particular to a projection method and a control circuit based on the synchronous movement of an electrostatic MEMS micromirror and a laser. Background Art

[0002] Augmented Reality (AR) display technology can seamlessly overlay virtual data into the real world, and is currently leading a profound change in human perception and interaction. Therefore, designing high-performance display devices that can integrate virtual digital content with real-world experience has become the focus of the AR field. AR display systems can be roughly divided into panel-based display systems and scanning display systems. Panel-based display systems, such as common digital light processing technology (DLP) and liquid crystal display technology (LCD), use global pixel illumination and then pixel-by-pixel shading to adjust the light intensity, ultimately achieving image projection display. However, for AR applications, image projection usually only requires 30% of the global pixels to be lit, while the entire panel remains lit during display, resulting in limited luminous efficiency, low image contrast, and significant heat generation. In addition, since the system requires multiple optical lenses for projection, this type of technology inevitably increases the volume of the optical system. In contrast, the laser beam scanning projection display system (LBS) based on the micro-electro-mechanical system (MEMS) micro-mirror has become an attractive alternative in the field of AR display due to its focus-free, efficient on-demand projection mechanism, which fully combines the respective advantages of laser technology and MEMS technology. The LBS display system modulates light pulses in time and space, and uses MEMS mirrors to form each pixel of the image in sequence. This display technology lights up or extinguishes the laser with pixel-level accuracy, improves high optical efficiency and contrast, and can reduce the generation of waste heat. In addition, the feature of LBS focus-free projection eliminates the need for projection and significantly reduces the volume of the optical system. Therefore, LBS projection display technology has broad application prospects in typical AR display fields such as AR glasses and automotive AR head up display (HUD).

[0003] In the LBS projection system, due to the different working principles of MEMS micromirrors, there are many laser scanning projection methods. The two most commonly used scanning methods are grating scanning and Lissajous scanning. Among them, traditional grating scanning is more common in current applications. The working mode of grating scanning is the synthesis of two mutually perpendicular vibrations, simple harmonic vibration along the X-axis direction and linear vibration along the Y-axis direction. The scanning rate in the Y direction is much smaller than the scanning rate in the X direction. After scanning a cycle in the X direction, the scanning in the Y direction only moves a very short distance, so it can be approximately regarded as the laser scanning a horizontal line in the X direction. After scanning a cycle in the Y direction, the entire display area is covered by many horizontal lines, and the resulting scanning pattern is similar to a grating. This scanning method is similar to the cathode ray tube (CRT) display technology, and the two can learn from each other in theory and practice. In addition, the scanning trajectory of raster scanning is fixed, similar to the image pixel storage method, the pixel position and time have a simple corresponding relationship, and the image encoding algorithm is relatively simple. However, the disadvantages of the LBS projection system based on grating scanning are also quite obvious. For example, the low scanning frequency in the Y direction leads to limited frame rate of grating scanning and weak resistance to external vibration interference; the existence of the scanning return state leads to low display efficiency; the vibration in the Y direction does not work in a resonant state, resulting in limited scanning angle; and the device is difficult to manufacture.

[0004] The working mode of Lissajous scanning is the synthetic motion of two mutually perpendicular simple harmonic vibrations, one along the X direction and the other along the Y direction. At this time, the scanning frequencies in the X and Y directions are both operated at a faster frequency near the resonant frequency of the two axes of the MEMS micromirror. When the frequency ratio of the two axes is an integer, its scanning trajectory is a closed curve of some form, which is called a Lissajous figure. Compared with grating scanning, the LBS projection system based on Lissajous scanning drives the MEMS reflector in a resonant state of high frequency in both axes. Therefore, the LBS projection system based on Lissajous scanning has the advantages of high frame rate, strong anti-external interference ability, large scanning angle, and low operating voltage. At the same time, since Lissajous scanning does not need to consider the return time, its display efficiency is higher. In addition, the micromirrors that realize Lissajous scanning are mainly electrostatic drive types, and the device manufacturing is relatively easy. Therefore, the LBS projection system based on Lissajous scanning has a broader prospect in the field of AR projection display.

[0005] Since the Lissajous scanning trajectory is diagonally offset in sequence, it does not conform to conventional thinking in terms of image encoding and timing control. Compared with raster scanning, the LBS projection system based on Lissajous scanning is more difficult to implement. In terms of two-dimensional electrostatic MEMS micromirror drive, since the movement of the MEMS micromirror and the laser needs to be synchronously controlled, the hardware needs to provide two accurate fast and slow axis drive signals for the MEMS micromirror according to the frame rate and drive frequency. In addition, according to the sweep frequency characteristics of the MEMS micromirror, when the micromirror drive frequency works between the first resonance point and the second resonance point, the micromirror can produce a larger scanning angle, but it is necessary to add a corresponding sweep frequency module through hardware. However, in order to simplify the hardware design, conventional LBS projection systems based on Lissajous scanning often do not add a sweep frequency module in the actual circuit. In terms of the synchronous control of the MEMS micromirror and the laser, due to the inherent delay of each axis of the MEMS micromirror and the delay of the drive circuit, the relationship between the square wave drive signal applied to the fast and slow axes of the MEMS micromirror and the angle vibration of the MEMS micromirror is changed, and the synchronous control relationship between the MEMS micromirror movement and the laser cannot be directly established through the square wave drive signal. In addition, the projection start point of the LBS projection system needs to be determined based on the synchronous control relationship between the MEMS micromirror movement and the laser. In conventional LBS projection systems based on Lissajous scanning, the laser is usually lit for a fixed time and the position of the Lissajous scanning trajectory is continuously adjusted to determine the delay size of the system. By delaying the laser lighting time or applying a delay to the pixel data, the movement of the MEMS micromirror and the laser is synchronously controlled and the projection start point of the LBS projection system is determined. These methods have many disadvantages. First, the debugging method based on the Lissajous trajectory is cumbersome and difficult; second, when the Lissajous trajectory is dense, it is difficult for the human eye to distinguish it. It is necessary to use a high-speed camera to capture and design additional programs to debug the Lissajous trajectory, which greatly increases the design complexity. Summary of the invention

[0006] The purpose of the present invention is to provide a projection method and a control circuit based on the synchronous movement of an electrostatic MEMS micromirror and a laser, so as to realize the fast and slow axis driving and frequency sweeping movement of a two-dimensional electrostatic resonant MEMS micromirror, so that an LBS projection system can achieve a higher frame rate and a larger field of view; determine the first light output delay of the fast axis and the second light output delay of the slow axis of the two-dimensional electrostatic resonant MEMS micromirror, and determine the starting point of the projection in combination with the parameters of the LBS projection system, and then control the synchronous movement of the laser and the two-dimensional electrostatic resonant MEMS micromirror, so that the LBS projection system has the significant advantages of high frame rate, large field of view, small size, low power consumption and high mechanical stability.

[0007] In order to achieve the above object, the present invention adopts the following technical scheme:

[0008] In a first aspect, the present invention provides a projection method based on the synchronous movement of an electrostatic MEMS micromirror and a laser, which is applied to a LBS projection system. The LBS projection system uses a two-dimensional electrostatic resonant MEMS micromirror and a laser, and comprises the following steps:

[0009] S1. Configuring the preset frequency and sweep range of the fast-axis driving square wave and the slow-axis driving square wave of the two-dimensional electrostatic resonant MEMS micromirror, generating the fast-axis driving square wave and the slow-axis driving square wave while sweeping the frequency, and outputting the fast-axis driving square wave and the slow-axis driving square wave after the sweep; and driving the fast-axis and slow-axis motions of the two-dimensional electrostatic resonant MEMS micromirror respectively based on the fast-axis driving square wave and the slow-axis driving square wave after the sweep;

[0010] S2. Control the synchronous movement of the laser and the fast axis and slow axis, including:

[0011] S20. Determine a first light output delay and a second light output delay, wherein the first light output delay and the second light output delay are respectively the time difference when the laser is at the rising edge relative to the fast axis driving square wave and the slow axis driving square wave;

[0012] S21. When it is detected that the fast-axis driving square wave is at the rising edge, after the first light-emitting delay, the laser is turned on to achieve synchronous movement of the laser and the fast axis, and the deflection position of the fast axis at the time of lighting is determined as the fast-axis light-emitting point of the laser relative to the rising edge of the fast-axis driving square wave;

[0013] S22. When it is detected that the slow axis driving square wave is at the rising edge, after the second light output delay, the laser is turned on to achieve synchronous movement of the laser and the slow axis, and the deflection position of the slow axis at the lighting moment is determined as the slow axis light output point of the laser relative to the rising edge of the slow axis driving square wave;

[0014] S3. Within one frame time, adjust the time difference between the fast-axis driving square wave and the slow-axis driving square wave, find the first time that the fast-axis light-emitting point and the slow-axis light-emitting point are at the same time, and determine it as the projection starting point;

[0015] S4. Preset the number of projection points, and start projection in the order of the scanning trajectory from the projection starting point.

[0016] As a possible implementation method, S1 specifically includes the following sub-steps:

[0017] S10. Based on the frame rate, clock frequency and preset frequencies of the fast-axis driving square wave and the slow-axis driving square wave of the two-dimensional electrostatic resonant MEMS micromirror of the LBS projection system, calculate the fast-axis driving square wave generation period, the slow-axis driving square wave generation period, and the number of fast-axis driving square waves and the number of slow-axis driving square waves included in one frame time;

[0018] S11. Based on the fast-axis drive square wave generation cycle and the number of fast-axis drive square waves, the total time of the fast-axis drive square wave within one frame time is obtained; based on the slow-axis drive square wave generation cycle and the number of slow-axis drive square waves, the total time of the slow-axis drive square wave within one frame time is obtained; and the difference between the total time of the fast-axis drive square wave and the total time of the slow-axis drive square wave is calculated;

[0019] S12. Compensate the difference time to the total time of the slow axis driving square wave, so that within the time of projecting one frame of image, the total time of the fast axis driving square wave is equal to the total time of the slow axis driving square wave, and obtain the compensated slow axis driving square wave generation cycle;

[0020] S13. Generate a fast-axis drive square wave based on the frame rate and the fast-axis drive square wave generation period, generate a slow-axis drive square wave based on the frame rate and the compensated slow-axis drive square wave generation period, generate the fast-axis drive square wave and the slow-axis drive square wave while sweeping the frequency, and output the swept fast-axis drive square wave and the slow-axis drive square wave; respectively drive the fast-axis and slow-axis movements of the two-dimensional electrostatic resonant MEMS micromirror based on the swept fast-axis drive square wave and the slow-axis drive square wave.

[0021] As a possible implementation method, the first light emission delay is determined as follows: when the rising edge of the fast-axis drive square wave is detected, the laser is turned on, and after half a cycle of the fast-axis drive square wave, the laser is turned off, and the first light emission delay is determined based on the deviation between the field of view covered by the laser and the entire field of view within half a cycle; the second light emission delay is determined as follows: when the rising edge of the slow-axis drive square wave is detected, the laser is turned on, and after half a cycle of the slow-axis drive square wave, the laser is turned off, and the second light emission delay is determined based on the deviation between the field of view covered by the laser and the entire field of view within half a cycle.

[0022] As a possible implementation method, S3 specifically includes the following sub-steps:

[0023] S30. When the first fast-axis light point is detected within one frame, the timing is started, and when the first slow-axis light point is detected, the timing is stopped to obtain the time difference;

[0024] S31. Apply a time difference to the fast-axis driving square wave so that the first fast-axis light-emitting point coincides with the first slow-axis light-emitting point, and the coincidence point is the projection starting point.

[0025] As a possible implementation method, S4 is implemented based on a state machine, specifically:

[0026] The state machine outputs the corresponding pixel data based on the address corresponding to each projection point. At the same time, the projection points that have completed the projection are counted until the count reaches the preset number of projection points, completing the projection of one frame of image and continuing the projection of the next frame of image.

[0027] In a second aspect, the present invention provides a projection control circuit based on the synchronous movement of an electrostatic MEMS micromirror and a laser, which is used to execute the projection method based on the synchronous movement of an electrostatic MEMS micromirror and a laser provided in the first aspect, wherein the control circuit at least comprises: a main control module, a micromirror driving module, a synchronous control module and a projection control module;

[0028] The main control module is electrically connected to the micromirror driving module, the synchronization control module and the projection control module, and is used to generate a first enable signal, a test signal and a second enable signal; the main control module sends the first enable signal to the micromirror driving module, sends the test signal to the synchronization control module, and sends the second enable signal to the projection control module to control the operation of the micromirror driving module, the synchronization control module and the projection control module;

[0029] The micromirror driving module is connected to the synchronization control module and the projection control module, and is used to generate fast-axis and slow-axis driving square waves and status signals, and sweep the frequency while generating the fast-axis driving square wave and the slow-axis driving square wave; the fast-axis and slow-axis driving square waves respectively drive the fast-axis and slow-axis movements of the two-dimensional electrostatic resonant MEMS micromirror, and the status signals are simultaneously transmitted to the synchronization control module and the projection control module;

[0030] The synchronous control module receives the test signal and the state signal, determines the first light output delay and the second light output delay, and controls the two-dimensional electrostatic resonant MEMS micromirror to move synchronously with the laser;

[0031] The projection control module is used to determine the projection starting point and perform a projection operation under the control of a second enable signal.

[0032] As a possible implementation method, the projection operation is implemented based on a state machine, and the state machine has a projection state and an idle state. At the initial moment and the non-projection moment, the state machine is in the idle state. When the second enable signal state is high, the state machine jumps from the idle state to the projection state, and projects each projection point one by one. The corresponding pixel data is output based on the address corresponding to each projection point. At the same time, a counter is used to count the projection points that have completed the projection until the count reaches the preset number of projection points, completing the projection of one frame of image, and continuing the projection of the next frame of image. When the second enable signal state is low, the state machine jumps from the projection state to the idle state.

[0033] As a possible implementation method, the micromirror driving module includes a fast-axis driving square wave generation module and a slow-axis driving square wave generation module and a frequency sweeping module. The fast-axis driving square wave generation module is used to generate fast-axis driving square waves and slow-axis driving square waves and status signals. The frequency sweeping module is used to sweep the frequency while generating the fast-axis driving square wave and the slow-axis driving square wave.

[0034] As a possible implementation method, the control circuit also includes a serial port module and a RAM. The serial port module is connected to the main control module and the RAM, and is used to send instructions and data to the main control module, and send image data to the RAM under the control of the main control module; the main control module controls the RAM based on the address corresponding to each projection point, and outputs the corresponding pixel data to the projection control module.

[0035] Compared with the prior art, the beneficial effects of the present invention are:

[0036] 1. The projection method based on the synchronous movement of an electrostatic MEMS micromirror and a laser provided by the present invention drives a two-dimensional electrostatic resonant MEMS micromirror to perform Lissajous scanning through two-way fast and slow axis square wave driving signals, so that the projection system has the significant advantages of high frame rate, small size, low power consumption and high mechanical stability. At the same time, a frequency sweeping module is added when generating a driving square wave. Compared with a direct driving method, the two-dimensional electrostatic resonant MEMS micromirror can produce a larger field of view. In addition, since Lissajous scanning has high requirements for both fast and slow axis frequencies, a counter-based method is used to generate a driving square wave with a fixed frequency to ensure stable imaging.

[0037] 2. The projection method based on the synchronous movement of the electrostatic MEMS micromirror and the laser provided by the present invention determines and applies the light emission delay of the laser for the fast and slow axes separately, so that the system can light up the laser when the two-dimensional electrostatic resonant MEMS micromirror is deflected to the zero angle. The method is simple and has low requirements. It is not necessary to measure the specific size of each part of the delay such as the response delay of the fast and slow axes of the micromirror and the circuit propagation delay. In addition, when the Lissajous scanning track is dense, that is, when the projection resolution is required to be high, the synchronous control of the micromirror and the laser drive can also be achieved by this method.

[0038] 3. The projection method based on the synchronous movement of the electrostatic MEMS micromirror and the laser provided by the present invention does not need to be repeatedly adjusted according to the actual trajectory when determining the projection origin. After determining the light emitting delay of the fast and slow axes of the micromirror, the phase difference of the fast and slow axis driving square waves can be automatically obtained through internal digital logic collection. By applying it to the fast and slow axis driving square wave generation process, the projection origin can be found, thereby realizing the projection work of the system and eliminating the complicated work of actual measurement and debugging of the projection origin. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0040] Figure 1 It is a flow chart of a method for controlling synchronous motion of a two-dimensional electrostatic resonant MEMS micromirror and a laser in an embodiment of the present invention;

[0041] Figure 2 It is a control logic diagram of a two-dimensional electrostatic resonant MEMS micromirror and laser synchronous motion control circuit in an embodiment of the present invention;

[0042] Figure 3 Schematic diagram of the frequency sweep process in an embodiment of the present invention;

[0043] Figure 4 Schematic diagram of the relationship between the single-axis deflection angle of a two-dimensional electrostatic resonant MEMS micromirror and a driving square wave in an embodiment of the present invention;

[0044] Figure 5 A schematic diagram of the embodiment of the present invention showing that the laser light emission delay is applied at the rising edge of the driving square wave to adjust the angle of deflection of the two-dimensional electrostatic resonant MEMS micromirror at the laser light emission moment;

[0045] Figure 6 The figure is a schematic diagram of determining the projection starting point in an embodiment of the present invention.

[0046] Reference numerals

[0047] 1- Main control module, 2- Micromirror drive module, 3- Synchronous control module, 4- Projection control module, 5- Serial port module. DETAILED DESCRIPTION

[0048] In order to clearly describe the technical solutions of the embodiments of the present invention, in the embodiments of the present invention, words such as "first" and "second" are used to distinguish the same items or similar items with basically the same functions and effects. For example, the first threshold and the second threshold are only used to distinguish different thresholds, and their order is not limited. Those skilled in the art can understand that words such as "first" and "second" do not limit the quantity and execution order, and words such as "first" and "second" do not necessarily limit them to be different.

[0049] It should be noted that, in the present invention, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the present invention should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way.

[0050] In the present invention, "at least one" means one or more, and "plurality" means two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone, where A and B can be singular or plural. The character " / " generally indicates that the associated objects before and after are in an "or" relationship. The following at least one item (items) or similar expressions thereof refer to any combination of these items, including any combination of single items (items) or plural items (items). For example, at least one item (items) of a, b or c can mean: a, b, c, the combination of a and b, the combination of a and c, the combination of b and c, or the combination of a, b and c, where a, b, c can be single or multiple.

[0051] In the field of augmented reality display technology, the LBS projection system based on Lissajous scanning has broad prospects in AR projection display. However, since the Lissajous scanning trajectory is offset in an oblique direction in sequence, it does not conform to conventional thinking in terms of image encoding and timing control. Therefore, in terms of the two-dimensional electrostatic resonant MEMS micromirror drive, it is necessary to synchronously control the movement of the two-dimensional electrostatic resonant MEMS micromirror and the laser. There are many disadvantages in the existing methods. For example, the debugging method based on the Lissajous trajectory is cumbersome and difficult; for example, when the Lissajous trajectory is dense, it is difficult for the human eye to distinguish it. It is necessary to use a high-speed camera to capture and design additional programs to debug the Lissajous trajectory, which greatly increases the design complexity.

[0052] The present invention proposes a projection method and a control circuit based on the synchronous movement of an electrostatic MEMS micromirror and a laser, which can realize the fast and slow axis driving and frequency sweeping movement of a two-dimensional electrostatic resonant MEMS micromirror, so that an LBS projection system can achieve a higher frame rate and a larger field of view; the response delays of the fast and slow axes of the two-dimensional electrostatic resonant MEMS micromirror are measured, and the starting point of the projection is determined in combination with the parameters of the LBS projection system, and then the movement of the laser and the two-dimensional electrostatic resonant MEMS micromirror is synchronously controlled, so that the LBS projection system has the significant advantages of high frame rate, large field of view, small size, low power consumption and high mechanical stability.

[0053] In the first aspect, the present invention provides a projection method based on the synchronous movement of an electrostatic MEMS micromirror and a laser, which is applied to a LBS projection system. The LBS projection system uses a two-dimensional electrostatic resonant MEMS micromirror and a laser, see Figure 1 , including the following steps:

[0054] S1. Configuring the preset frequency and sweep range of the fast-axis driving square wave and the slow-axis driving square wave of the two-dimensional electrostatic resonant MEMS micromirror, generating the fast-axis driving square wave and the slow-axis driving square wave while sweeping the frequency, and outputting the fast-axis driving square wave and the slow-axis driving square wave after the sweep; and driving the fast-axis and slow-axis motions of the two-dimensional electrostatic resonant MEMS micromirror respectively based on the fast-axis driving square wave and the slow-axis driving square wave after the sweep;

[0055] As a possible implementation method, S1 specifically includes the following sub-steps:

[0056] S10. Based on the frame rate, clock frequency and preset frequencies of the fast-axis driving square wave and the slow-axis driving square wave of the two-dimensional electrostatic resonant MEMS micromirror of the LBS projection system, calculate the fast-axis driving square wave generation period, the slow-axis driving square wave generation period, and the number of fast-axis driving square waves and the number of slow-axis driving square waves included in one frame time;

[0057] S11. Based on the fast-axis drive square wave generation cycle and the number of fast-axis drive square waves, the total time of the fast-axis drive square wave within one frame time is obtained; based on the slow-axis drive square wave generation cycle and the number of slow-axis drive square waves, the total time of the slow-axis drive square wave within one frame time is obtained; and the difference between the total time of the fast-axis drive square wave and the total time of the slow-axis drive square wave is calculated;

[0058] S12. Compensate the difference time to the total time of the slow axis driving square wave, so that within the time of projecting one frame of image, the total time of the fast axis driving square wave is equal to the total time of the slow axis driving square wave, and obtain the compensated slow axis driving square wave generation cycle;

[0059] S13. Generate a fast-axis drive square wave based on the frame rate and the fast-axis drive square wave generation period, generate a slow-axis drive square wave based on the frame rate and the compensated slow-axis drive square wave generation period, generate the fast-axis drive square wave and the slow-axis drive square wave while sweeping the frequency, and output the swept fast-axis drive square wave and the slow-axis drive square wave; respectively drive the fast-axis and slow-axis movements of the two-dimensional electrostatic resonant MEMS micromirror based on the swept fast-axis drive square wave and the slow-axis drive square wave.

[0060] Exemplarily, the preset frequency of the fast-axis driving square wave of the two-dimensional electrostatic resonant MEMS micromirror is 37092Hz, and the preset frequency of the slow-axis driving square wave is 3630Hz. Assuming that the frame rate of the LBS projection system is 33Hz and the clock frequency is 100Mhz, the generation method of the fast and slow-axis driving square waves of the two-dimensional electrostatic resonant MEMS micromirror based on the counter is further explained. There are many ways to generate square waves, and the common ones include driving square wave generation based on direct digital frequency synthesis (Direct Digital Synthesizer, DDS) and driving square wave generation based on counters. Here, taking the fast-axis driving square wave as an example, it is known that the clock frequency of the LBS projection system is 100Mhz, then one cycle of the fast-axis driving square wave contains approximately 2696 system clock cycles clk, and the formula is as follows:

[0061]

[0062] Wherein clk is the system clock cycle. Due to the square wave generation principle based on DDS, the process of continuous cyclic accumulation of the accumulator will cause the periods of different square waves to have a clk deviation in time when the square waves are continuously generated. For example, when the fast-axis drive square wave is continuously generated, its period will periodically change between 2969 clk and 2970 clk. This kind of change is not accepted when performing synchronous control of two-dimensional electrostatic resonant MEMS micromirror and laser drive. Therefore, the present invention generates fast and slow axis drive square waves based on the counter method, and the period of the single-axis drive square wave is an integer multiple of clk, and is as close as possible to the driving frequency of the two-dimensional electrostatic resonant MEMS micromirror. Therefore, one period of the fast and slow axis drive square waves is composed of 2696 and 27548 clk respectively. The generation of driving square waves should also be considered from the perspective of a frame of image. According to the principle of Lissajous scanning motion, it is known that the frame rate of the LBS projection system is 33Hz. In the time interval of projecting a frame of image, there are 1124 fast-axis driving square waves and 110 slow-axis driving square waves, respectively. The formula is as follows:

[0063] Fast Axis:

[0064] Slow axis:

[0065] The reason is that when performing projection control, the projection starting point needs to be determined based on a frame of image. Therefore, the product of the period of the fast-axis drive square wave and the number of fast-axis drive square waves contained in a frame of image, that is, the total time of the fast-axis drive square wave; and the product of the period of the slow-axis drive square wave and the number of slow-axis drive square waves contained in a frame of image, that is, the total time of the slow-axis drive square wave, should be equal, that is, the projection time of a frame of image (the inverse of the frame rate). According to the above calculation, it can be known that:

[0066] △ = 2696*1124-27548*110 = 24 clks

[0067] Δ is the difference between the total time of the fast-axis drive square wave and the total time of the slow-axis drive square wave in a frame of image. It can be seen that the total time of the fast-axis drive square wave is 24 clk more than the total time of the slow-axis drive square wave. Therefore, when the slow-axis drive square wave is generated, within the time range of a frame of image, it is considered to increase the time of 24 clk to meet the relationship that the total time of the fast-axis drive square wave and the slow-axis drive square wave in a frame of image are equal. Exemplarily, every 53 cycles of a slow-axis drive square wave equal to 27548 clk, two cycles of a slow-axis drive square wave equal to 27554 clk are inserted, that is, a frame of image contains a total of 110 slow-axis drive square waves, of which 106 drive square waves have a cycle equal to 27548 clk, and 4 drive square waves have a cycle equal to 27554 clk, and are generated in the order of 53-2-53-2. In actual application, this quasi-sequential operation is implemented using a state machine. The fast axis driving square wave is based on a counter that generates a driving square wave with a period equal to 2696 clks. The hysteresis amplitude-frequency characteristic of the MEMS micromirror itself is that when the driving frequency applied to the fast and slow axes of the micromirror is gradually reduced from a high frequency to a target frequency, a larger field of view angle will be generated compared to the case where the target frequency is directly applied to the fast and slow axes of the micromirror. This method is also called frequency sweeping. Therefore, in order to obtain a larger field of view angle, when the fast and slow axis driving square waves are generated, it is necessary to set the frequency sweep range for the fast and slow axes respectively and perform the frequency sweeping operation.

[0068] S2. Control the synchronous movement of the laser and the fast axis and slow axis, including:

[0069] S20. Determine a first light output delay and a second light output delay, wherein the first light output delay and the second light output delay are respectively the time difference when the laser is at the rising edge relative to the fast axis driving square wave and the slow axis driving square wave;

[0070] S21. When it is detected that the fast-axis driving square wave is at the rising edge, after the first light-emitting delay, the laser is turned on to achieve synchronous movement of the laser and the fast axis, and the deflection position of the fast axis at the time of lighting is determined as the fast-axis light-emitting point of the laser relative to the rising edge of the fast-axis driving square wave;

[0071] S22. When it is detected that the slow axis driving square wave is at the rising edge, after the second light output delay, the laser is turned on to achieve synchronous movement of the laser and the slow axis, and the deflection position of the slow axis at the lighting moment is determined as the slow axis light output point of the laser relative to the rising edge of the slow axis driving square wave;

[0072] As a possible implementation method, the first light emission delay is determined as follows: when the rising edge of the fast-axis drive square wave is detected, the laser is turned on, and after half a cycle of the fast-axis drive square wave, the laser is turned off, and the first light emission delay is determined based on the deviation between the field of view covered by the laser and the entire field of view within half a cycle; the second light emission delay is determined as follows: when the rising edge of the slow-axis drive square wave is detected, the laser is turned on, and after half a cycle of the slow-axis drive square wave, the laser is turned off, and the second light emission delay is determined based on the deviation between the field of view covered by the laser and the entire field of view within half a cycle.

[0073] When the two-dimensional electrostatic resonant MEMS micromirror is working, its fast and slow axes are both in a resonant state. When the driving mode is a square wave, the deflection angle of the micromirror's single axis has a clear corresponding relationship with the driving square wave of the single axis. The deflection angle of the micromirror's single axis changes sinusoidally, and one cycle of the single axis angle deflection corresponds to two driving square waves of the axis. Ideally, the rising edge of the driving square wave corresponds to the maximum value of the micromirror's single axis deflection angle. However, due to the characteristics of the micromirror device itself, the fast and slow axes will not immediately respond to the corresponding deflection angle after receiving their respective driving square waves. This response time is called the response delay of the fast and slow axes of the micromirror. Considering the delay factors such as the circuit propagation delay introduced when the driving square wave propagates in the circuit, the corresponding relationship between the deflection of the fast and slow axes of the micromirror and the driving square wave deviates from the ideal situation. The rising edge of the driving square wave no longer corresponds to the maximum value of the micromirror's single axis deflection angle, and the position of the micromirror's single axis deflection cannot be determined by the rising edge of the driving square wave.

[0074] Since the starting point of the projection of the LBS projection system is the position where the fast and slow axes of the two-dimensional electrostatic resonant MEMS micromirror are both at zero angle (the two-dimensional electrostatic resonant MEMS micromirror is not deflected), the idea of ​​controlling the synchronous movement of the laser and the fast and slow axes of the two-dimensional electrostatic resonant MEMS micromirror is that when the rising edge of the fast-axis driving square wave is detected, the first light output delay is applied to the laser, and when the fast axis of the electrostatic MEMS micromirror is deflected to zero angle, the laser is turned on, and a corresponding relationship between the rising edge of the fast-axis driving square wave and the laser drive is established to achieve synchronous movement of the laser and the fast axis; when the rising edge of the slow-axis driving square wave is detected, a second light output delay is applied to the laser, and when the slow axis of the electrostatic MEMS micromirror is deflected to zero angle, the laser is turned on, and a corresponding relationship between the rising edge of the slow-axis driving square wave and the laser drive is established to achieve synchronous movement of the laser and the slow axis. Taking the fast axis as an example, the method to determine the delay of the first light output of the laser is to turn on the laser when the rising edge of the fast axis drive square wave is detected, and turn off the laser after half a cycle of the fast axis drive square wave (the duration of the high level of the fast axis drive square wave). Ideally, the rising edge of the fast axis drive square wave corresponds to the maximum value of the fast axis deflection angle of the two-dimensional electrostatic resonant MEMS micromirror. After the above processing, the laser emitted by the laser is scanned from the positive and negative maximum deflection angle positions to the zero angle position under the action of the deflection of the two-dimensional electrostatic resonant MEMS micromirror, covering the entire field of view. However, due to the existence of delay, there is a phase difference between the fast axis drive square wave and the fast axis angle deflection of the electrostatic MEMS micromirror, and the laser scanning will not cover the entire field of view. Therefore, when the rising edge of the fast-axis driving square wave is detected, a light emission delay is applied to the laser, and it can be observed that the phase of the laser scanning changes. By changing the light emission delay, the laser emission time is adjusted to the moment when the micromirror deflects to the zero angle position. At this time, the laser scans from the zero angle position to both sides to the maximum angle position. At this point, the synchronization control of the fast-axis driving square wave and the laser emission time is completed, that is, when the rising edge of the fast-axis driving square wave is detected, after the set light emission delay, the electrostatic MEMS micromirror deflects to the zero angle point position, and the laser emits light. The set light emission delay is the first light emission delay, and the deflection position of the fast axis at the moment of lighting is determined as the fast-axis light emission point of the laser relative to the rising edge of the fast-axis driving square wave. The method for determining the second light emission delay and the slow-axis light emission point of the laser is the same as the first light emission delay and the fast-axis light emission point.

[0075] The present invention determines and applies the light emission delay of the laser for the fast and slow axes separately, so that the system can light up the laser at the origin of the micromirror deflection. The method is simple and has low requirements. It is not necessary to measure the specific magnitude of each delay such as the response delay of the fast and slow axes of the micromirror and the circuit propagation delay. In addition, when the Lissajous scanning track is dense, that is, when the projection resolution is required to be high, the method can also realize the synchronous control of the micromirror and the laser drive.

[0076] S3. Within one frame time, adjust the time difference between the fast-axis driving square wave and the slow-axis driving square wave, find the first time that the fast-axis light-emitting point and the slow-axis light-emitting point are at the same time, and determine it as the projection starting point;

[0077] As a possible implementation method, S3 specifically includes the following sub-steps:

[0078] S30. When the first fast-axis light point is detected within one frame, the timing is started, and when the first slow-axis light point is detected, the timing is stopped to obtain the time difference;

[0079] S31. Apply the above time difference to the fast-axis driving square wave, so that the first fast-axis light-emitting point coincides with the first slow-axis light-emitting point, and the coincidence point is the projection starting point.

[0080] As an example of determining the starting point of the projection, in a rectangular coordinate system, according to the trajectory equation of the Lissajous scan, the formula is as follows:

[0081] x=Asin(2πft)

[0082] =Bsin(2mf slow tt)

[0083] Among them, f 快 、f 慢 are the frequencies of the fast and slow axis driving square waves of the two-dimensional electrostatic resonant MEMS micromirror, t is the current moment of Lissajous scanning motion, A and B are the amplitudes of the fast and slow axis scanning angles of the two-dimensional electrostatic resonant MEMS micromirror, x and y are the horizontal and vertical coordinates of the Lissajous scanning point, respectively. The position where the fast and slow axes of the two-dimensional electrostatic resonant MEMS micromirror are simultaneously at zero angle is called the origin.

[0084] Exemplarily, a counter is used to count the number of fast and slow axis driving square waves respectively to determine the time interval of a frame image, and the projection is performed in frames. Within a frame scanning time, the Lissajous scanning trajectory will pass through the origin twice, and the time interval is half of a frame time, that is, half-frame projection time, and the positions of the two times passing through the origin need to be considered. For the fast axis, the light-emitting point of the first driving square wave is used as the first origin in a frame, then the second origin position is after half a frame time, that is, the moment when half of the total number of driving square waves in a frame is counted, and these two moments are marked with signals. The same is true for the slow axis. If the identification signal of the fast axis and the identification signal of the slow axis are at the same time, it means that the two-dimensional electrostatic resonant MEMS micromirror is at the origin position at this time. Therefore, it is necessary to change the relative position of the fast and slow axis identification signals by adjusting the time difference between the fast and slow axis driving square waves, so as to align the fast and slow axis identification signals to the same time, and find the origin position of the two-dimensional electrostatic resonant MEMS micromirror, which is the projection starting point.

[0085] When determining the projection origin, the present invention does not need to repeatedly adjust according to the actual trajectory. After determining the light emitting delay of the fast and slow axes of the micromirror, the time difference of the fast and slow axis driving square waves can be obtained by timing with a counter. The time difference is applied to the generation of the fast and slow axis driving square waves, and the projection origin can be found, thereby realizing the projection work of the system and eliminating the complicated work of actually measuring and debugging the projection origin.

[0086] S4. Preset the number of projection points, and start projection in the order of the scanning trajectory from the projection starting point.

[0087] As a possible implementation method, S4 is implemented based on a state machine, specifically:

[0088] The state machine outputs the corresponding pixel data based on the address corresponding to each projection point. At the same time, the projection points that have completed the projection are counted until the count reaches the preset number of projection points, completing the projection of one frame of image and continuing the projection of the next frame of image.

[0089] Exemplarily, the state machine has a projection state and an idle state. At the initial moment and the non-projection moment, the state machine is in the idle state. After receiving the projection start signal, the state machine jumps from the idle state to the projection state, and projects each projection point one by one. The corresponding pixel data is output based on the address corresponding to each projection point. At the same time, a counter is used to count the projection points that have completed the projection until the count reaches the preset number of projection points, completing the projection of one frame of image, and continuing the projection operation of the next frame of image. When the projection enable signal state is low, the state machine jumps from the projection state to the idle state.

[0090] The projection method based on the synchronous movement of an electrostatic MEMS micromirror and a laser provided by the present invention drives a two-dimensional electrostatic resonant MEMS micromirror to perform Lissajous scanning through two-way fast and slow axis square wave driving signals, so that the projection system has the significant advantages of high frame rate, small size, low power consumption and high mechanical stability. At the same time, a frequency sweeping module is added when generating a driving square wave. Compared with a direct drive method, the two-dimensional electrostatic resonance type can produce a larger field of view. In addition, since Lissajous scanning has high requirements for both fast and slow axis frequencies, a counter-based method is used to generate a driving square wave with a fixed frequency to ensure stable imaging.

[0091] In a second aspect, the present invention provides a projection control circuit based on the synchronous movement of an electrostatic MEMS micromirror and a laser, which is used to execute the projection method based on the synchronous movement of an electrostatic MEMS micromirror and a laser provided in the first aspect, see Figure 2 , the control circuit at least includes: a main control module 1, a micromirror driving module 2, a synchronization control module 3 and a projection control module 4;

[0092] See also Figure 2, the main control module 1 is electrically connected to the micromirror driving module 2, the synchronization control module 3 and the projection control module 4, and is used to generate a first enable signal, a test signal and a second enable signal; the main control module 1 sends the first enable signal to the micromirror driving module 2, sends the test signal to the synchronization control module 3, and sends the second enable signal to the projection control module 4 to control the operation of the micromirror driving module 2, the synchronization control module 3 and the projection control module 4;

[0093] See also Figure 2 The micromirror driving module 2 is connected to the synchronous control module 3 and the projection control module 4, and is used to generate fast-axis and slow-axis driving square waves and state signals, and sweep the frequency while generating the fast-axis driving square wave and the slow-axis driving square wave; the fast-axis and slow-axis driving square waves respectively drive the fast-axis and slow-axis movements of the two-dimensional electrostatic resonant MEMS micromirror, and the state signals are simultaneously transmitted to the synchronous control module 3 and the projection control module 4;

[0094] The synchronous control module receives the test signal and the state signal, determines the first light output delay and the second light output delay, and controls the two-dimensional electrostatic resonant MEMS micromirror to move synchronously with the laser;

[0095] The projection control module is used to determine the projection starting point and perform a projection operation under the control of a second enable signal.

[0096] As a possible implementation method, the projection operation is implemented based on a state machine, and the state machine has a projection state and an idle state. At the initial moment and the non-projection moment, the state machine is in the idle state. When the second enable signal state is high, the state machine jumps from the idle state to the projection state, and projects each projection point one by one. The corresponding pixel data is output based on the address corresponding to each projection point. At the same time, a counter is used to count the projection points that have completed the projection until the count reaches the preset number of projection points, completing the projection of one frame of image, and continuing the projection of the next frame of image. When the second enable signal state is low, the state machine jumps from the projection state to the idle state.

[0097] As a possible implementation method, the micromirror driving module includes a fast-axis driving square wave generation module and a slow-axis driving square wave generation module and a frequency sweeping module. The fast-axis driving square wave generation module is used to generate fast-axis driving square waves and slow-axis driving square waves and status signals. The frequency sweeping module is used to sweep the frequency while generating the fast-axis driving square wave and the slow-axis driving square wave.

[0098] See also Figure 2 As a possible implementation method, the control circuit also includes a serial port module 5 and a RAM. The serial port module 5 is connected to the main control module 1 and the RAM, and is used to send instructions and data to the main control module 1, and send image data to the RAM under the control of the main control module 1; the main control module 1 controls the RAM based on the address corresponding to each projection point, and outputs the corresponding image data to the projection control module 4.

[0099] To facilitate understanding of the technical solution of the present application, the projection control circuit based on the synchronous movement of the electrostatic MEMS micromirror and the laser and the process of executing the projection method proposed by the present invention are further explained below in conjunction with specific embodiments.

[0100] See also Figure 2 , the host computer sends instructions and data through the serial port module 5. The image data is stored in the RAM under the control of the address output by the main control module 1, and the instructions are parsed by the main control module 1. The main control module 1 controls other modules to perform corresponding functions according to the instructions. When the first enable signal is high, the micromirror driving module 2 performs the function of generating fast and slow axis driving square waves. First, the frequency of the fast and slow axis driving signals is controlled to sweep from high frequency to target frequency in a pre-set sweep frequency range, so that the two-dimensional electrostatic resonant MEMS micromirror can scan a larger field of view. The sweep process is shown in Figure 3 . Since the fast and slow axis frequencies of the two-dimensional electrostatic resonant MEMS micromirror are relatively high, according to the principle of Lissajous scanning, a higher frame rate can be generated. After completing the frequency sweep, the fast and slow axis driving square waves with fixed frequencies are output to drive the two-dimensional electrostatic resonant MEMS micromirror, which can meet the frequency requirements of the fast and slow axes for Lissajous scanning for stable imaging. At the same time, the status signals such as the period, rising edge, falling edge, and frequency sweep completion signal of the driving square wave are output to the synchronous control module.

[0101] In the synchronous control module, the same test method is used for the fast and slow axes to determine the light delay value of the laser relative to the fast and slow axes respectively. Taking the fast axis as an example, when the rising edge of the driving square wave is detected, the laser is turned on, and after half a cycle of the driving square wave, the laser is turned off. At this time, due to the existence of delays such as the response delay of the two-dimensional electrostatic resonant MEMS micromirror and circuit delay, the scanning of the laser deviates from the ideal correspondence between the driving square wave of the two-dimensional electrostatic resonant MEMS micromirror and the angle, such as Figure 4 As shown. Since the projection starting point needs to be found in the projection control module, the corresponding relationship between the rising edge of the driving square wave and the zero-angle deflection point of the micromirror needs to be found in the synchronization control module. Therefore, when the driving square wave rises, a light emission delay is applied to the laser to adjust the angle of the micromirror deflection at the moment of laser emission. The test method is as follows: Figure 5As shown. When the laser emits light at the moment when the two-dimensional electrostatic resonant MEMS micromirror is deflected to the zero angle position, the laser scans from the zero angle position to both sides to the maximum angle position, covering the entire field of view of the two-dimensional electrostatic resonant MEMS micromirror. The delay value at this time is the first light emission delay value of the required laser light emission moment relative to the rising edge of the driving square wave, and the deflection position of the fast axis at the moment of lighting is determined as the fast axis light emission point of the laser relative to the rising edge of the fast axis driving square wave. This measurement method is relatively simple and has strong applicability. It does not need to measure the specific size of each delay in the system, and it is also suitable for scenes with high projection resolution. The test method of the slow axis is the same. The electrostatic MEMS micromirror state signal and the fast axis light emission point and slow axis light emission point finally obtained by this module are output to the projection control module.

[0102] The projection control module first determines the projection starting point, and the process is as follows: Figure 6As shown. A counter is used to count the number of fast and slow axis driving square waves to determine the time interval of a frame image, and the projection is performed in frames. Within a frame scanning time, the Lissajous scanning trajectory will pass through the origin twice, with a time interval of half a frame time, that is, half a frame projection time, and the positions of the two times passing through the origin need to be considered. For the fast axis, the light-emitting point of the first driving square wave is taken as the first origin in a frame, then the second origin position is after half a frame time, that is, the moment when half of the total number of fast axis driving square waves in a frame is counted, and these two moments are marked with signals. The same is true for the slow axis. If the identification signal of the fast axis and the identification signal of the slow axis are at the same time, it means that the two-dimensional electrostatic resonant MEMS micromirror is at the origin position at this time. The relative position of the fast and slow axis identification signals is changed by adjusting the time difference between the fast and slow axis driving square waves, so that the fast and slow axis identification signals are aligned to the same time, the origin position of the two-dimensional electrostatic resonant MEMS micromirror is found, and the position of the fast and slow axis identification signals when they are aligned for the first time is determined as the projection starting point. At this time, within one frame of image time, the two identification signals of the fast and slow axes, which are half a frame apart, are aligned respectively, that is, they are located at the same time. This part of the logic adopts a state machine design. Within one frame time, when the first fast axis light point is detected (the first identification signal of the fast axis driving square wave in one frame), the number of clock cycles is counted by the counter until the first slow axis light point is detected (the first identification signal of the slow axis driving square wave in one frame), the timing is stopped, the time difference is obtained by counting the value, and the time difference value is stored in the register, and the setting of the time difference between the fast and slow axis driving square waves is completed by sending instructions to the main control module. This method can find the projection starting point through the calculation of circuit logic, eliminating the tedious actual debugging work of the projection starting point. After finding the projection starting point, normal projection can be carried out. The projection logic is implemented based on the state machine, and the state machine has an idle state and a projection state. When not projecting, the state machine is in an idle state. When the second enable signal is high and the projection starting point is detected, the state machine jumps to the projection state. Each scanning point is projected according to the order of the Lissajous scanning trajectory and the time interval between the preset scanning points. The pixel data corresponding to the scanning point is taken out from the RAM according to the corresponding address. At the same time, the number of projected scanning points is counted by a counter. The RAM address is incremented each time until all scanning points are projected. Then, the projection operation of the next frame of the image is continued. When the projection enable signal state is low, the state machine jumps from the projection state to the idle state.

[0103] Although the present invention is described herein in conjunction with various embodiments, in the process of implementing the claimed invention, those skilled in the art may understand and implement other variations of the disclosed embodiments by viewing the drawings, the disclosure, and the drawings, etc. In the specification, the word "comprising" does not exclude other components or steps, and "one" or "an" does not exclude multiple situations. A single processor or other unit can implement several functions listed in the specification. Certain measures are recorded in different embodiments, but this does not mean that these measures cannot be combined to produce good results.

[0104] Although the present invention has been described in conjunction with specific features and embodiments thereof, it is apparent that various modifications and combinations may be made thereto without departing from the spirit and scope of the present invention. Accordingly, this specification and the accompanying drawings are merely exemplary illustrations of the present invention and are deemed to cover any and all modifications, variations, combinations or equivalents within the scope of the present invention. Obviously, those skilled in the art may make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, the present invention is intended to include such modifications and variations if they fall within the scope of the present invention and its equivalents.

Claims

1. A projection method based on the synchronous movement of an electrostatic MEMS micromirror and a laser, applied to a LBS projection system, wherein the LBS projection system uses a two-dimensional electrostatic resonant MEMS micromirror and a laser, characterized in that: The steps include: S1. Configure the preset frequency and sweep range of the fast-axis driving square wave and the slow-axis driving square wave of the two-dimensional electrostatic resonant MEMS micromirror, generate the fast-axis driving square wave and the slow-axis driving square wave and sweep the frequency simultaneously, and output the fast-axis driving square wave and the slow-axis driving square wave after the frequency sweep; Based on the swept fast-axis driving square wave and the slow-axis driving square wave, respectively driving the fast-axis and slow-axis motions of the two-dimensional electrostatic resonant MEMS micromirror; S2. Control the synchronous movement of the laser and the fast axis and slow axis, including: S20. Determine a first light emission delay and a second light emission delay, wherein the first light emission delay and the second light emission delay are respectively the time difference when the laser is at the rising edge relative to the fast axis driving square wave and the slow axis driving square wave; S21. When it is detected that the fast-axis driving square wave is at the rising edge, after the first light-emitting delay, the laser is turned on to achieve synchronous movement of the laser and the fast axis, and the deflection position of the fast axis at the lighting moment is determined as the fast-axis light-emitting point of the laser relative to the rising edge of the fast-axis driving square wave; S22. When it is detected that the slow axis driving square wave is at the rising edge, after the second light output delay, the laser is turned on to achieve synchronous movement of the laser and the slow axis, and the deflection position of the slow axis at the lighting moment is determined as the slow axis light output point of the laser relative to the rising edge of the slow axis driving square wave; S3. Within one frame time, adjust the time difference between the fast-axis driving square wave and the slow-axis driving square wave, find the first time that the fast-axis light-emitting point and the slow-axis light-emitting point are at the same time, and determine it as the projection starting point; S4. Preset the number of projection points, and start projecting in order of the scanning trajectory from the projection starting point.

2. The projection method based on the synchronous movement of electrostatic MEMS micromirror and laser according to claim 1, characterized in that: The S1 specifically includes the following sub-steps: S10. Based on the frame rate, clock frequency and preset frequency of the LBS projection system, calculate the fast-axis drive square wave generation period, the slow-axis drive square wave generation period, and the number of fast-axis drive square waves and the number of slow-axis drive square waves included in one frame time; S11. Based on the fast-axis drive square wave generation cycle and the number of fast-axis drive square waves, obtain the total time of the fast-axis drive square wave within one frame time; based on the slow-axis drive square wave generation cycle and the number of slow-axis drive square waves, obtain the total time of the slow-axis drive square wave within one frame time; and calculate the difference between the total time of the fast-axis drive square wave and the total time of the slow-axis drive square wave; S12. Compensate the difference time to the total time of the slow axis driving square wave, so that within the time of projecting one frame of image, the total time of the fast axis driving square wave is equal to the total time of the slow axis driving square wave, and obtain the compensated slow axis driving square wave generation cycle; S13. Generate a fast-axis drive square wave based on the frame rate and the fast-axis drive square wave generation period, generate a slow-axis drive square wave based on the frame rate and the compensated slow-axis drive square wave generation period, generate the fast-axis drive square wave and the slow-axis drive square wave while sweeping the frequency, and output the fast-axis drive square wave and the slow-axis drive square wave after the sweep; The fast axis and slow axis motions of the two-dimensional electrostatic resonant MEMS micromirror are driven respectively based on the fast axis driving square wave and the slow axis driving square wave after the frequency sweep.

3. The projection method based on the synchronous movement of electrostatic MEMS micromirror and laser according to claim 1, characterized in that: Determining the first light emission delay is specifically as follows: when a rising edge of a fast-axis driving square wave is detected, the laser is turned on, and after half a cycle of the fast-axis driving square wave, the laser is turned off, and the first light emission delay is determined based on a deviation between the field of view covered by the laser and the entire field of view within the half cycle; The second light emission delay is determined specifically as follows: when the rising edge of the slow axis driving square wave is detected, the laser is turned on, and after half a cycle of the slow axis driving square wave, the laser is turned off, and the second light emission delay is determined based on the deviation between the field of view covered by the laser and the entire field of view within half a cycle.

4. The projection method based on the synchronous movement of electrostatic MEMS micromirror and laser according to claim 1, characterized in that: The S3 specifically includes the following sub-steps: S30. When the first fast-axis light point is detected within one frame, the timing is started, and when the first slow-axis light point is detected, the timing is stopped to obtain the time difference; S31. Apply the time difference to the fast-axis driving square wave, so that the first fast-axis light-emitting point coincides with the first slow-axis light-emitting point, and the coincidence point is the projection starting point.

5. The projection method based on the synchronous movement of electrostatic MEMS micromirror and laser according to claim 1, characterized in that: The S4 is implemented based on a state machine, specifically: The state machine outputs corresponding pixel data based on the address corresponding to each projection point, and at the same time, counts the projection points that have completed the projection until the count reaches the preset number of projection points, completing the projection of one frame of image and continuing the projection of the next frame of image.

6. A projection control circuit based on the synchronous motion of an electrostatic MEMS micromirror and a laser, used to execute the projection method based on the synchronous motion of an electrostatic MEMS micromirror and a laser according to any one of claims 1 to 5, characterized in that: The control circuit at least includes: a main control module, a micromirror driving module, a synchronization control module and a projection control module; The main control module is electrically connected to the micromirror driving module, the synchronization control module and the projection control module, and is used to generate a first enable signal, a test signal and a second enable signal; the main control module sends the first enable signal to the micromirror driving module, sends the test signal to the synchronization control module, and sends the second enable signal to the projection control module, so as to control the operation of the micromirror driving module, the synchronization control module and the projection control module; The micromirror driving module is connected to the synchronization control module and the projection control module, and is used to generate fast-axis and slow-axis driving square waves and status signals, and sweep the frequency while generating the fast-axis driving square wave and the slow-axis driving square wave; the fast-axis and slow-axis driving square waves respectively drive the fast-axis and slow-axis movements of the two-dimensional electrostatic resonant MEMS micromirror, and the status signal is simultaneously transmitted to the synchronization control module and the projection control module; The synchronization control module receives the test signal and the state signal, determines the first light output delay and the second light output delay, and controls the two-dimensional electrostatic resonant MEMS micromirror to move synchronously with the laser; The projection control module is used to determine a projection starting point and perform a projection operation under the control of the second enable signal.

7. The projection control circuit based on the synchronous movement of electrostatic MEMS micromirror and laser according to claim 6, characterized in that: The projection operation is implemented based on a state machine, and the state machine has a projection state and an idle state. At the initial moment and the non-projection moment, the state machine is in the idle state. When the second enable signal state is high, the state machine jumps from the idle state to the projection state, and projects each projection point one by one, and outputs corresponding pixel data based on the address corresponding to each projection point. At the same time, a counter is used to count the projection points that have completed the projection until the count reaches the preset number of projection points, completing the projection of one frame of image, and continuing the projection of the next frame of image. When the second enable signal state is low, the state machine jumps from the projection state to the idle state.

8. The projection control circuit based on the synchronous movement of electrostatic MEMS micromirror and laser according to claim 6, characterized in that: The micromirror driving module includes a fast and slow axis driving square wave generating module and a frequency sweeping module. The fast and slow axis driving square wave generating module is used to generate fast and slow axis driving square waves and status signals. The frequency sweeping module is used to sweep the frequency while generating the fast axis driving square wave and the slow axis driving square wave.

9. The projection control circuit based on the synchronous movement of electrostatic MEMS micromirror and laser according to claim 6, characterized in that: The control circuit also includes a serial port module and a RAM. The serial port module is connected to the main control module and the RAM, and is used to send instructions and data to the main control module, and send image data to the RAM under the control of the main control module; the main control module controls the RAM based on the address corresponding to each projection point, and outputs the corresponding pixel data to the projection control module.

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