Laser gas telemetering imaging system based on micro galvanometer scanning and detection method

Abstract

The invention discloses a laser gas telemetering imaging system based on micro galvanometer scanning and a detection method, the system comprises: a laser transmit-receive optical unit, detection laser emitted by a semiconductor laser and aiming laser emitted by an aiming laser are combined by a beam combiner, and are collimated to an MEMS micro galvanometer through a collimation system; the MEMS micro galvanometer deflects by a corresponding angle to reflect the laser beam to a target detection area; the photoelectric detector array is used for receiving a light return signal of the detection laser; the signal processing and control unit is used for calculating the concentration information of the target gas in the target detection area according to the return light signal subjected to photoelectric conversion; the visual imaging unit is used for shooting a visual image of the detection area; and the information fusion unit is used for fusing the calculated gas concentration of the target detection area into a visual image, and sending the fused visual image to the signal output display unit for visual display of the gas concentration.

Description

Technical Field

[0001] The invention belongs to the technical field of laser gas telemetry, and in particular relates to a laser gas telemetry imaging system and a detection method based on micro-vibration mirror scanning. Background Art

[0002] At present, laser gas telemetry based on tunable laser absorption spectroscopy (TDLAS) is one of the main means of detecting dangerous gas leaks. Traditional laser telemetry instruments can only detect gas leaks along the path of the spot scan due to the small output spot of the laser telemetry instrument. It is difficult to aim and prone to missed reports, which cannot meet the early warning needs of safe production. In addition, laser gas detection can only reflect the size of the gas leak, and cannot visualize the gas leak.

[0003] In the prior art, some of them enlarge the detection spot of the laser, and some of them collimate the point spot of the laser into a linear spot through an optical system. After these changes, the laser telemetry system is easier to aim and reduces missed reports, but because it disperses the energy of the laser light, the detection distance becomes shorter and the sensitivity becomes worse. Others use a pan-tilt head to scan the laser telemetry system. Although the detection range is large and the detection distance is long, the belt life of the pan-tilt head is limited and needs to be replaced frequently, and the maintenance cost is high. There are also some that use a dual mechanical galvanometer laser scanning system. The mechanical galvanometer completes a comprehensive scan of the detection area. Although it solves the problem of expanding the detection range, the use of a mechanical galvanometer makes the system not only complex in structure, large in size, and difficult to integrate, but also has low control accuracy and poor synchronization.

[0004] Therefore, there is an urgent need for a laser gas remote sensing imaging system that integrates a wide detection range and a long detection distance to make up for the defects of existing detection methods and technologies. Summary of the invention

[0005] In order to solve the problems existing in the prior art, the present invention proposes a laser gas telemetry imaging system and a detection method based on micro-vibration mirror scanning.

[0006] The objective of the present invention is achieved by the following technical solutions: In a first aspect, the present invention provides a laser gas telemetry imaging system based on micro-vibration mirror scanning, comprising: Laser transceiver optical unit, signal processing and control unit, visualization imaging unit, information fusion unit, signal output display unit and power supply unit for providing power to each unit; The laser transceiver optical unit comprises a semiconductor laser, an aiming laser, a beam combiner, a collimation system, a MEMS micro-vibration mirror, a receiving lens and a photodetector array; the detection laser emitted by the semiconductor laser and the aiming laser emitted by the aiming laser are combined by the beam combiner and then collimated onto the MEMS micro-vibration mirror by the collimation system; The MEMS micro-vibration mirror has two axes, X and Y, and each axis has two electrodes; the MEMS micro-vibration mirror is connected to the signal processing and control unit and the power supply unit respectively, and the signal processing and control unit controls the power supply unit to provide the MEMS micro-vibration mirror with a voltage corresponding to a required deflection angle, so as to control the MEMS micro-vibration mirror to reflect the laser beam to a target detection area; The photoelectric detector array is used to receive the return light signal of the detection laser that passes through the target detection area, is absorbed by the target gas, is reflected back by the background reflector, and is collected by the receiving lens, and is transmitted to the signal processing and control unit after photoelectric conversion; The signal processing and control unit calculates the concentration information of the target gas in the target detection area according to the return light signal after photoelectric conversion; The visualization imaging unit is used to capture a visualization image of the detection area; The information fusion unit is connected to the signal processing and control unit, the visualization imaging unit and the signal output display unit, and is used to fuse the calculated gas concentration of the target detection area into the visualization image, and send the fused visualization image to the signal output display unit for visualization of the gas concentration.

[0007] In a second aspect, the present invention provides a detection method based on the laser gas telemetry imaging system based on micro-vibration mirror scanning, comprising the following steps: (1) The signal processing and control unit controls the semiconductor laser and the aiming laser to emit light, and controls the visualization imaging unit to start capturing a visualization image; (2) The signal processing and control unit controls the power supply unit to provide corresponding voltage values ​​to the four electrodes X1, X2, Y1 and Y2 of the X and Y axes of the MEMS micro-vibration mirror, so that it scans the target detection area in a quasi-static mode or a uniform scanning mode according to a pre-set path; (3) The signal processing and control unit synchronously starts the corresponding dot matrix in the photodetector array to collect the received light signal according to the voltage value of the four electrodes of the MEMS micro-vibration mirror, and transmits the signal after photoelectric conversion to the signal processing and control unit for calculation and processing to obtain the gas concentration value; the scanning angle of the MEMS micro-vibration mirror is synchronized with the corresponding photodetector array collection; (4) When the calculated gas concentration value is greater than a preset alarm threshold, the signal processing and control unit adjusts the voltage values ​​of the four electrodes X1, X2, Y1 and Y2 of the MEMS micro-vibration mirror X and Y axes, so that the MEMS micro-vibration mirror performs a re-inspection near the alarm position according to the preset re-inspection times and re-inspection paths to confirm whether the alarm is a real leak alarm; (5) When a real leak alarm is confirmed, the signal processing and control unit sends the gas concentration to the information fusion unit; the information fusion unit draws the corresponding area of ​​the visualization image into images of different colors or grayscales according to the gas concentration, so as to intuitively present the shape and size of the leaking gas mass; the information fusion unit sends the drawn image to the signal output display unit for alarm and display; (6) After completing the specified re-inspection, the signal processing and control unit controls the MEMS micro-vibration mirror to continue scanning along the original path; (7) If it is confirmed to be a false leakage alarm, the signal processing and control unit discards the alarm and controls the micro-vibration mirror to continue scanning along the original path; (8) When shutting down, the signal processing and control unit controls the power supply of the laser and the MEMS micro-vibration mirror to be turned off, so that the laser is powered off and the position of the MEMS micro-vibration mirror returns to zero, and then the power supply of other parts of the system is turned off.

[0008] Based on the above, the laser gas telemetry imaging system based on micro-vibration mirror scanning also calibrates the image of the visualization imaging unit, the scanning angle of the MEMS micro-vibration mirror and the photodetector array before detection: The visualization imaging unit divides the visualization image into a plurality of detection areas according to the scanning angle of the MEMS micro-vibration mirror and the photodetector array; The signal processing and control unit controls the semiconductor laser and the aiming laser to emit light, and controls the MEMS micro-vibration mirror to scan, and respectively records and stores the corresponding relationship between the voltages of the four electrodes X1, X2, Y1 and Y2 of the MEMS micro-vibration mirror on the X-axis and Y-axis and the corresponding areas of the photodetector array and the visualized image.

[0009] Based on the above, the MEMS micro-vibration mirror is placed at the center of the receiving lens, and a hole is punched at the center of the receiving lens; A reflector is arranged between the collimation system and the MEMS micro-vibration mirror; The detection laser emitted by the semiconductor laser and the aiming laser emitted by the aiming laser are combined by the beam combiner, collimated by the collimation system and emitted by the reflector in sequence to the MEMS micro-vibration mirror. The MEMS micro-vibration mirror reflects the combined laser from the center of the hole of the receiving lens to the target detection area.

[0010] Based on the above, the MEMS micro-vibration mirror is placed at the edge of the receiving lens to reflect the laser beam to the target detection area.

[0011] Based on the above, the scan path is set as: According to the detection area divided by the visualization imaging unit, the circular spot of the detection laser is continuously scanned from the initial position along the positive X-axis direction-the negative Y-axis direction-the negative X-axis direction-the positive Y-axis direction, from the outer layer to the center layer by layer and point by point to the center of the visualization imaging unit, and then scanned from the center of the visualization imaging unit along the opposite path to the initial position of the set scanning path; When scanning according to a set scanning path, the method for controlling the voltages of the four electrodes of the MEMS micro-vibration mirror includes: To achieve scanning in the X-axis direction: The signal processing and control unit controls the power supply unit to fix the voltage values ​​of the two electrodes Y1 and Y2 of the MEMS micro-vibration mirror Y axis, and provides corresponding voltage values ​​to the two electrodes X1 and X2 of the MEMS micro-vibration mirror X axis; To achieve scanning in the Y-axis direction: The signal processing and control unit controls the power supply unit to fix the voltage values ​​of the two electrodes X1 and X2 of the MEMS micro-vibration mirror X-axis, and provides corresponding voltage values ​​to the two electrodes Y1 and Y2 of the MEMS micro-vibration mirror Y-axis.

[0012] Based on the above, the scan path is set as: According to the detection area divided by the visualization imaging unit, the circular spot of the detection laser is scanned from the initial position along the Y direction from top to bottom to the lowest end in the Y direction, then moved rightward once along the X direction, then scanned from bottom to top along the Y direction to the highest end in the Y direction, then moved rightward once along the X direction, and the detection is cyclically performed in sequence until the last detection area of ​​the visualization imaging unit, and then the detection returns to the initial position of the scanning path along the opposite path; When scanning according to a set scanning path, the method for controlling the voltages of the four electrodes of the MEMS micro-vibration mirror includes: To achieve scanning in the X-axis direction: The signal processing and control unit controls the power supply unit to fix the voltage values ​​of the two electrodes Y1 and Y2 of the MEMS micro-vibration mirror Y axis, and provides corresponding voltage values ​​to the two electrodes X1 and X2 of the MEMS micro-vibration mirror X axis; To achieve scanning in the Y-axis direction: The signal processing and control unit controls the power supply unit to fix the voltage values ​​of the two electrodes X1 and X2 of the MEMS micro-vibration mirror X-axis, and provides corresponding voltage values ​​to the two electrodes Y1 and Y2 of the MEMS micro-vibration mirror Y-axis.

[0013] Based on the above, the mirror size of the MEMS micro-vibration mirror is φ1~φ10mm, and the deflection angle is ±1°~±10°; The photodetector array is a 10×10 photodetector array.

[0014] Based on the above, the laser gas telemetry imaging system based on micro-vibration mirror scanning also includes a positioning unit for obtaining the position information of the detection equipment and a target recognition module for identifying the target detection area; The positioning unit confirms whether the detection area has been entered according to the acquired detection device position information. If the detection area has been entered, the target recognition module is started to recognize the target detection area and obtain the azimuth information of the target to be detected in the target detection area.

[0015] Compared with the prior art, the present invention has outstanding substantive features and significant progress, specifically: 1. The present invention integrates GPS positioning technology, image classification technology, micro-vibration mirror scanning technology, tunable laser absorption spectroscopy technology (Tunable Diode Laser Absorption Spectroscopy, TDLAS) and imaging technology, and proposes a laser gas telemetry imaging system based on micro-vibration mirror scanning, and proposes an optical path system and detection control method based on micro-vibration mirror, which solves the problem that the existing detection system cannot simultaneously meet the monitoring and early warning requirements of wide detection range, long detection distance, high sensitivity and visualization.

[0016] 2. The laser gas telemetry system provided by the present invention can realize real-time monitoring of a large detection range by adjusting the deflection angles of the micro-vibration mirror in the X and Y axis directions. It has a wide detection range, a long detection distance, high sensitivity, and a long service life. It is particularly suitable for installation in natural gas transmission and distribution stations to conduct dynamic 24-hour real-time monitoring of the stations, reduce labor costs, increase detection frequency, and improve safety. At the same time, combined with a visual imaging system, the concentration and image of the air mass can be intuitively displayed.

[0017] 3. The present invention can realize line scanning laser telemetry by adjusting the deflection in the X-axis direction and fixing the Y-axis direction. It can cooperate with drones, cars, electric vehicles, etc. to realize laser gas inspection, conduct long-distance and large-scale telemetry inspection on transmission and distribution pipelines and emergency rescue, effectively detect leakage of toxic and harmful gases, and ensure the safety of inspection personnel.

[0018] 4. The present invention adopts a piezoelectric or electrostatic MEMS micro-vibration mirror, which is small in size and can be integrated in the optical path system. The optical path structure is simple, does not block effective light, and has a long detection distance. The micro-vibration mirror scans by controlling the voltage of the micro-vibration mirror's electrodes. The two-dimensional adjustment has high synchronization, high control accuracy, and a simple control system. The micro-vibration mirror can realize quasi-static scanning mode and uniform speed scanning mode, and is suitable for different application occasions.

[0019] 5. The present invention can measure different gases, such as ethane, acetylene, etc., by replacing lasers with different central wavelengths. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the related technologies, the drawings required for use in the embodiments or the related technical descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 It is a structural block diagram of the system of the present invention.

[0022] Figure 2 Schematic diagram of the light path between the photodetector array and the visualization imaging unit in the present invention.

[0023] Figure 3 It is a 10*10 array diagram of the photodetector array and a 10*10 array division diagram of the visualization imaging unit in the present invention.

[0024] Figure 4 It is a 5*5 array diagram of the photodetector array and a 10*10 array division diagram of the visualization imaging unit in the present invention.

[0025] Figure 5 Schematic diagram of the micro-mirror scanning light path in Example 3.

[0026] Figure 6 Schematic diagram of the micro-mirror scanning light path in Example 4.

[0027] Figure 7 This is the surface scanning route map in Example 5.

[0028] Figure 8 This is the surface scanning route map in Example 6.

[0029] Fig. 9 This is the line scanning route map in Example 7.

[0030] Fig.10 This is the inspection scanning route map in Example 7. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0032] Example 1 This embodiment provides a laser gas telemetry imaging system based on micro-vibration mirror scanning, such as Figure 1 As shown, including: Laser transceiver optical unit, signal processing and control unit, visualization imaging unit, information fusion unit, signal output display unit and power supply unit for providing power to each unit; The laser transceiver optical unit comprises a semiconductor laser, an aiming laser, a beam combiner, a collimation system, a MEMS micro-vibration mirror, a receiving lens and a photodetector array; the detection laser emitted by the semiconductor laser and the aiming laser emitted by the aiming laser are combined by the beam combiner and then collimated onto the MEMS micro-vibration mirror by the collimation system; The MEMS micro-vibration mirror is a micro-vibration mirror using the principle of piezoelectric or electrostatic effect, and has two axes, X and Y, and two electrodes on each axis; the MEMS micro-vibration mirror is connected to the signal processing and control unit and the power supply unit respectively, and the signal processing and control unit controls the power supply unit to provide the MEMS micro-vibration mirror with a voltage corresponding to the required deflection angle, so as to control the MEMS micro-vibration mirror to reflect the laser beam to the target detection area; The photoelectric detector array is used to receive the return light signal of the detection laser that passes through the target detection area, is absorbed by the target gas, is reflected back by the background reflector, and is collected by the receiving lens, and is transmitted to the signal processing and control unit after photoelectric conversion; The signal processing and control unit calculates the concentration information of the target gas in the target detection area according to the return light signal after photoelectric conversion; The visualization imaging unit is used to capture a visualization image of the detection area; The information fusion unit is connected to the signal processing and control unit, the visualization imaging unit and the signal output display unit, and is used to fuse the calculated gas concentration of the target detection area into the visualization image, and send the fused visualization image to the signal output display unit for visualization of the gas concentration.

[0033] Example 2 This embodiment provides a detection method of the laser gas telemetry imaging system based on micro-vibration mirror scanning as described in Embodiment 1, comprising the following steps: (1) Before the detection, the image of the visualization imaging unit, the scanning angle of the MEMS micro-mirror and the photodetector array are calibrated: The visualization imaging unit divides the visualization image into a plurality of detection areas according to the scanning angle of the MEMS micro-vibration mirror and the photodetector array; The signal processing and control unit controls the semiconductor laser and the aiming laser to emit light, and controls the MEMS micro-vibration mirror to scan, and respectively records and stores the corresponding relationship between the voltages of the four electrodes X1, X2, Y1 and Y2 of the MEMS micro-vibration mirror on the X-axis and Y-axis and the corresponding areas of the photodetector array and the visualized image.

[0034] (2) The signal processing and control unit controls the semiconductor laser and the aiming laser to emit light, and controls the visualization imaging unit to start capturing a visualization image.

[0035] (3) The signal processing and control unit controls the power supply unit to provide corresponding voltage values ​​to the four electrodes X1, X2, Y1 and Y2 of the X and Y axes of the MEMS micro-vibration mirror, so that it scans the target detection area in a quasi-static mode or a uniform scanning mode according to a pre-set path.

[0036] (4) The signal processing and control unit synchronously starts the corresponding dot matrix in the photodetector array to collect the received light signal according to the voltage value of the four electrodes of the MEMS micro-vibration mirror, and transmits the signal after photoelectric conversion to the signal processing and control unit for calculation and processing to obtain the gas concentration value; the scanning angle of the MEMS micro-vibration mirror is synchronized with the corresponding photodetector array collection.

[0037] Figure 2 A schematic diagram of the optical path between the photodetector array and the visualization imaging unit is shown. Figure 3 A 10*10 array diagram of the photodetector array and a 10*10 array division diagram of the visualization imaging unit are shown. Figure 4 The 5*5 array diagram of the photodetector array and the 10*10 array division diagram of the visualization imaging unit are shown. In step (4), if the visualization imaging unit is a 10*10 array and the photodetector array is also a 10*10 array, then according to Figure 2-Figure 4 It can be seen that when detecting the visualization imaging unit 1, the photodetector array is the photodetector No. 100 that can receive the signal, when detecting the visualization imaging unit 2, the photodetector array is the photodetector No. 99 that can receive the signal, and when detecting the visualization imaging unit 100, the photodetector array is the photodetector No. 1 that can receive the signal; If the visualization imaging unit is a 10*10 array and the photodetector array is a 5*5 array, then according to Figure 2-Figure 4 It can be seen that when detecting visualization imaging units 1, 2, 11, and 12, the photodetector array is photodetector No. 25 and can receive signals; when detecting visualization imaging units 3, 4, 13, and 14, the photodetector array is photodetector No. 24 and can receive signals; when detecting visualization imaging units 89, 90, 99, and 100, the photodetector array is photodetector No. 1 and can receive signals.

[0038] (5) When the calculated gas concentration value is greater than a preset alarm threshold, the signal processing and control unit adjusts the voltage values ​​of the four electrodes X1, X2, Y1 and Y2 of the MEMS micro-vibration mirror X and Y axes, so that the MEMS micro-vibration mirror performs a re-inspection near the alarm position according to the preset re-inspection times and re-inspection path to confirm whether the alarm is a real leak alarm.

[0039] (6) When a real leak alarm is confirmed, the signal processing and control unit sends the gas concentration to the information fusion unit; the information fusion unit draws the corresponding area of ​​the visualization image into images of different colors or grayscales according to the gas concentration, so as to intuitively present the shape and size of the leaking gas mass; the information fusion unit sends the drawn image to the signal output display unit for alarm and display. Furthermore, the gas concentration information can also be transmitted to other devices.

[0040] (7) After completing the specified re-inspection, the signal processing and control unit controls the micro-vibration mirror to continue scanning along the original path.

[0041] (8) If it is confirmed to be a false leakage alarm, the signal processing and control unit discards the alarm and controls the micro-vibration mirror to continue scanning along the original path.

[0042] (9) When shutting down, the signal processing and control unit controls the power supply of the laser and the MEMS micro-vibration mirror to be turned off, so that the laser is powered off and the position of the MEMS micro-vibration mirror returns to zero, and then the power supply of other parts of the system is turned off.

[0043] In this embodiment, the semiconductor laser is the current mainstream semiconductor laser. The photodetector array is a detector array that responds to the detection laser. The receiving lens is coated with an anti-reflection film of the measurement band to improve the transmittance and increase the measurement distance. The secondary focusing system includes a secondary focusing lens and a filter. The secondary focusing lens is used to converge the light converged by the receiving lens again to facilitate reception by the photodetector array. The filter is a narrow-band interference filter that is transparent to the measurement band. The aiming laser is a visible light laser. After being combined with the detection laser through a beam combiner, it is collimated by the collimation system to the MEMS micro-vibration mirror, and then reflected to the detection area by the MEMS micro-vibration mirror to indicate the detection position of the detection laser.

[0044] The laser control unit connects the signal processing and control unit, the semiconductor laser and the aiming laser. The laser control unit includes a current driving unit and a temperature control unit. After determining the driving current of the laser, the temperature of the TEC inside the laser is adjusted in real time so that the wavelength output by the laser is always locked on the absorption peak of the target gas. The laser driving signal output by the signal processing and control unit is used to debug the laser. After DA conversion, the driving signal is transmitted to the laser control unit to drive the semiconductor laser to emit light. At the same time, the temperature control unit in the laser control unit adjusts the TEC of the semiconductor laser in real time so that the output wavelength of the laser is always stable on the absorption peak of the gas.

[0045] The signal processing and control unit is connected to the MEMS micro-vibration mirror, the laser control unit, the photodetector array, the signal output unit, and the power supply unit. The MEMS micro-vibration mirror is connected to the power supply unit, and the signal processing and control unit controls the power supply unit to provide the corresponding voltage value to the MEMS micro-vibration mirror, thereby controlling the deflection angle of the MEMS micro-vibration mirror, so that the detection laser scans along a preset path. The signal processing and control unit starts a certain dot matrix in the photodetector array to collect the received signal according to the voltage value of the four electrodes of the MEMS micro-vibration mirror, and performs analysis and processing. The scanning angle of the MEMS micro-vibration mirror is synchronized with the corresponding photodetector array acquisition.

[0046] When the target gas leaks in the detection area, the detection laser passes through the target gas, is reflected by the background reflector, and the return light signal absorbed by the target gas is received by the photodetector array. After photoelectric conversion, it is transmitted to the signal processing and control unit, and the signal is amplified and filtered. After demodulating the first harmonic f and the second harmonic 2f, the concentration information of the target gas is calculated. When the concentration exceeds the set alarm threshold, the signal processing and control unit adjusts the voltage values ​​of the four electrodes X1, X2, Y1 and Y2 of the MEMS micro-vibration mirror X and Y axes, so that the MEMS micro-vibration mirror performs a re-inspection near the alarm position according to the pre-set re-inspection number and re-inspection path to determine whether the alarm is a real leakage alarm. Among them, the re-inspection number and re-inspection path are pre-set in the signal processing and control unit. Specifically, the re-inspection number can be 2 times or N times, and the re-inspection path is a 3*3 or 4*4 area scan near the alarm point.

[0047] When there are fewer photodetector arrays, the photodetector arrays can also be collected simultaneously without the need for time-sharing collection. Starting the collection of a certain point array in the photodetector array according to the scanning angle of the MEMS micro-vibration mirror is to reduce system computing resources, which is particularly suitable for the situation where there are more photodetector arrays.

[0048] When a leak is confirmed, the signal processing and control unit sends the gas concentration to the information fusion unit, which fuses the gas concentration with the visualization image, processes the image, and draws the corresponding area of ​​the image as an image of different colors (color) or different grayscales according to the gas concentration, thereby intuitively presenting the shape and size of the leaking gas mass.

[0049] If it is determined to be a false alarm, the concentration is discarded and the signal processing system controls the deflection angle of the micro-vibration mirror so that the detection laser continues to scan along the original path.

[0050] Preferably, in order to improve the detection efficiency, the laser gas telemetry imaging system based on micro-vibration mirror scanning further includes a target recognition module for identifying the target detection area; The target detection area can be set according to the target recognition result of the visual image by the target recognition module, so as to pre-recognize the scanning path; by identifying gas storage equipment such as gas pipelines as key target detection areas, the pipeline area where gas leakage may exist is scanned in a focused manner, wherein the gas pipeline recognition method includes but is not limited to image classification methods such as target recognition and target segmentation. The information fusion unit sends the orientation information of the key target detection area to the signal processing and control unit, and the signal processing and control unit controls the voltage of the MEMS micro-vibration mirror so that the semiconductor laser irradiates the corresponding position of the key target detection area for detection, thereby improving the detection efficiency.

[0051] Preferably, the laser gas telemetry imaging system based on micro-vibration mirror scanning also includes a positioning unit for obtaining position information of the detection equipment; the positioning unit confirms whether the detection area has been entered based on the obtained position information of the detection equipment, and if the detection area has been entered, the target recognition module is started to identify the target detection area and obtain the azimuth information of the target to be detected in the target detection area.

[0052] Example 3 For large-scale methane gas leakage monitoring, a DFB laser with a central wavelength of 1653.7nm or a quantum cascade laser with a central wavelength of 3260.2nm is selected as the light source, and an InGaAs detector array or a mercury cadmium telluride detector array is selected as the photodetector array. If the detection range is surface scanning, a surface array detector is selected, and if the detection range is linear, a linear array detector is selected; the receiving lens is an aspheric lens coated with an anti-reflection film near 1653.7nm or 3260.2nm. The anti-reflection film can improve the transmittance of the receiving lens to the measuring laser and increase the remote sensing distance; the filter is a narrow-band interference filter near 1653.7nm or 3260.2nm; the aiming laser is a 532nm green laser; after the detection laser and the aiming laser are combined by the beam combiner, they are collimated and emitted to the reflector through the laser collimation system, and then emitted by the reflector to the micro-vibration mirror, and then reflected by the micro-vibration mirror and irradiated into the monitoring area. After the detection laser passes through the target gas, it is reflected by the background reflector. The photodetector or photodetector array receives the return light signal absorbed by the target gas. After photoelectric conversion, it is transmitted to the signal processing and control unit, which amplifies and filters the signal to calculate the concentration information of the target gas in the target area.

[0053] Preferably, the MEMS micro-vibration mirror is a piezoelectric or electrostatic MEMS micro-vibration mirror with a mirror size of φ1~φ10mm, a deflection angle of ±1°~±10°, a gold-plated film on the reflector, and a reflectivity of more than 90% for lasers in the 1653.7nm or 3260.2nm band.

[0054] The signal processing and control unit controls the power supply unit to provide the voltage corresponding to the required deflection angle to the MEMS micro-vibration mirror, and controls the laser beam to detect different positions. For example, if the detection distance is 100 meters, the detection range is an area of ​​10 meters long and 10 meters wide, and the deflection angle range of the MEMS micro-vibration mirror is about ±1.35°. The detection spot output by the collimator is a circular spot with a diameter of 100 cm at 100 meters, so the deflection angle of the MEMS micro-vibration mirror is about 0.3° each time.

[0055] The photodetector array is a 10×10 array.

[0056] An optical path system for MEMS micro-mirror scanning: like Figure 5 As shown, the MEMS micro-vibration mirror is placed at the center of the receiving lens, and a hole is punched at the center of the receiving lens; A reflector is arranged between the collimation system and the MEMS micro-vibration mirror. After the detection laser emitted by the semiconductor laser and the aiming laser emitted by the aiming laser are combined by the beam combiner, they are collimated by the collimation system and emitted by the reflector in sequence to the MEMS micro-vibration mirror. The MEMS micro-vibration mirror reflects the combined laser from the hole center of the receiving lens to the target detection area. When the MEMS micro-vibration mirror is at zero position, the laser emission direction is the optical axis direction of the receiving lens.

[0057] In this embodiment, the MEMS micro-vibration mirror is placed at the center of the receiving lens, and the laser beam can be emitted from the center of the receiving lens, which has a compact structure, high sensitivity and a long detection distance.

[0058] Example 4 For large-scale methane gas leakage monitoring, a DFB laser with a central wavelength of 1653.7nm or a quantum cascade laser with a central wavelength of 3260.2nm is selected as the light source, and an InGaAs detector array or a mercury cadmium telluride detector array is selected as the photodetector array. If the detection range is surface scanning, a surface array detector is selected, and if the detection range is linear, a linear array detector is selected; the receiving lens is an aspheric lens coated with an anti-reflection film near 1653.7nm or 3260.2nm. The anti-reflection film can improve the transmittance of the receiving lens to the measuring laser and increase the remote sensing distance; the filter is a narrow-band interference filter near 1653.7nm or 3260.2nm; the aiming laser is a 532nm green laser; after the detection laser and the aiming laser are combined by the beam combiner, they are collimated and emitted to the micro-vibration mirror through the laser collimation system, and then reflected by the micro-vibration mirror and irradiated into the monitoring area. After the detection laser passes through the target gas, it is reflected by the background reflector. The photodetector or photodetector array receives the return light signal absorbed by the target gas. After photoelectric conversion, it is transmitted to the signal processing and control unit, which amplifies and filters the signal to calculate the concentration information of the target gas in the target area.

[0059] Preferably, the MEMS micro-vibration mirror is a piezoelectric or electrostatic MEMS micro-vibration mirror with a mirror size of φ1~φ10mm and a deflection angle of ±1°~±10°.

[0060] The signal processing and control unit controls the power supply unit to provide the voltage corresponding to the required deflection angle to the MEMS micro-vibration mirror, and controls the laser beam to detect different positions. For example, if the detection distance is 100 meters, the detection range is an area of ​​10 meters long and 10 meters wide, and the deflection angle range of the MEMS micro-vibration mirror is about ±1.35°. The detection spot output by the collimator is a circular spot with a diameter of 100 cm at 100 meters, so the deflection angle of the MEMS micro-vibration mirror is about 0.3° each time.

[0061] The photodetector array is a 10×10 array.

[0062] An optical path system for MEMS micro-mirror scanning: like Figure 6 As shown, no reflector is arranged between the collimation system and the MEMS micro-vibration mirror, and the MEMS micro-vibration mirror is placed at the edge of the receiving lens, and the center of the receiving lens does not need to be punched. The zero point of the MEMS micro-vibration mirror is 45° counterclockwise deflected from the horizontal position, and the laser collimation system irradiates the laser beam vertically upward onto the surface of the micro-vibration mirror; when the MEMS micro-vibration mirror is at the zero point, the laser emission direction is the optical axis direction of the receiving lens. In this embodiment, the MEMS micro-vibration mirror is placed at the edge of the receiving lens, and the center of the receiving lens does not need to be punched, and the reflector is omitted, which has a simple structure and free design.

[0063] Example 5 Based on the laser gas telemetry imaging system based on micro-vibration mirror scanning described in Example 3 and Example 4, this embodiment provides an implementation scheme of a set scanning path of the detection method of the present invention.

[0064] like Figure 7 As shown, the scan path is set as: According to the detection area divided by the visualization imaging unit, the circular spot of the detection laser is continuously scanned from the initial position along the positive X-axis direction-the negative Y-axis direction-the negative X-axis direction-the positive Y-axis direction, from the outer layer to the center layer by layer and point by point to the center of the visualization imaging unit, and then scanned from the center of the visualization imaging unit along the opposite path to the initial position of the set scanning path; When scanning according to a set scanning path, the method for controlling the voltages of the four electrodes of the MEMS micro-vibration mirror includes: To achieve scanning in the X-axis direction: The signal processing and control unit controls the power supply unit to fix the voltage values ​​of the two electrodes Y1 and Y2 of the MEMS micro-vibration mirror Y axis, and provides corresponding voltage values ​​to the two electrodes X1 and X2 of the MEMS micro-vibration mirror X axis; To achieve scanning in the Y-axis direction: The signal processing and control unit controls the power supply unit to fix the voltage values ​​of the two electrodes X1 and X2 of the MEMS micro-vibration mirror X-axis, and provides corresponding voltage values ​​to the two electrodes Y1 and Y2 of the MEMS micro-vibration mirror Y-axis.

[0065] Specifically, Figure 3 or Figure 4As shown in , the visualization imaging unit is divided into 10×10 (No. 1-No. 100) detection areas to form 5 layers of detection areas, and the small circle represents the circular spot of the detection laser. The method of controlling the MEMS micro-vibration mirror to realize the scanning path along the positive X-axis direction-negative Y-axis direction-negative X-axis direction-positive Y-axis direction is: 1) The signal processing and control unit controls the power supply unit to fix the voltage values ​​of the two electrodes Y1 and Y2 of the MEMS micro-vibration mirror on the Y axis, and provides corresponding voltage values ​​to the two electrodes X1 and X2 of the MEMS micro-vibration mirror on the X axis, and scans along the positive X axis direction to reach the last detection area in the positive X axis direction of the detection area of ​​the layer; 2) The signal processing and control unit controls the power supply unit to fix the voltage values ​​of the two electrodes X1 and X2 of the MEMS micro-vibration mirror on the X axis, and provides corresponding voltage values ​​to the two electrodes Y1 and Y2 of the MEMS micro-vibration mirror on the Y axis, and scans along the anti-Y axis direction to reach the last detection area in the anti-Y axis direction of the detection area of ​​the layer; 3) The signal processing and control unit controls the power supply unit to fix the voltage values ​​of the two electrodes Y1 and Y2 of the MEMS micro-vibration mirror on the Y axis, and provides corresponding voltage values ​​to the two electrodes X1 and X2 of the MEMS micro-vibration mirror on the X axis, and scans along the anti-X axis direction to reach the last detection area in the anti-X axis direction of the detection area of ​​the layer; 4) The signal processing and control unit controls the power supply unit, fixes the voltage values ​​of the two electrodes X1 and X2 of the MEMS micro-vibration mirror on the X axis, and provides corresponding voltage values ​​to the two electrodes Y1 and Y2 on the Y axis of the MEMS micro-vibration mirror, scanning along the positive Y axis direction to reach the second to last detection area in the positive Y axis direction of the detection area of ​​the layer.

[0066] Example 6 Based on the laser gas telemetry imaging system based on micro-vibration mirror scanning described in Example 3 and Example 4, this embodiment provides another implementation scheme of setting the scanning path of the detection method of the present invention.

[0067] like Figure 8 As shown, the scan path is set as: According to the detection area divided by the visualization imaging unit, the circular spot of the detection laser is scanned from the initial position along the Y direction from top to bottom to the lowest end in the Y direction, then moved rightward once along the X direction, then scanned from bottom to top along the Y direction to the highest end in the Y direction, then moved rightward once along the X direction, and the detection is cyclically performed in sequence until the last detection area of ​​the visualization imaging unit, and then the detection returns to the initial position of the scanning path along the opposite path; When scanning according to a set scanning path, the method for controlling the voltages of the four electrodes of the MEMS micro-vibration mirror includes: To achieve scanning in the X-axis direction: The signal processing and control unit controls the power supply unit to fix the voltage values ​​of the two electrodes Y1 and Y2 of the MEMS micro-vibration mirror Y axis, and provides corresponding voltage values ​​to the two electrodes X1 and X2 of the MEMS micro-vibration mirror X axis; To achieve scanning in the Y-axis direction: The signal processing and control unit controls the power supply unit to fix the voltage values ​​of the two electrodes X1 and X2 of the MEMS micro-vibration mirror X-axis, and provides corresponding voltage values ​​to the two electrodes Y1 and Y2 of the MEMS micro-vibration mirror Y-axis.

[0068] Specifically, Figure 3 or Figure 4 As shown in , the visualization imaging unit is divided into 10×10 (No. 1-No. 100) detection areas, and the small circle represents the circular spot of the detection laser.

[0069] When scanning according to the scanning path set in this embodiment, the control steps of the voltages of the four electrodes of the MEMS micro-vibration mirror are as follows: 1) The signal processing and control unit controls the power supply unit to provide corresponding voltage values ​​to the two electrodes Y1 and Y2 of the MEMS micro-vibration mirror on the Y axis, and fixes the voltage values ​​of the two electrodes X1 and X2 on the X axis, first realizes scanning in the Y axis direction, and after reaching the last detection area in the current Y axis direction, fixes the two voltages of Y1 and Y2; 2) The signal processing and control unit controls the power supply unit to provide corresponding voltage values ​​to the two electrodes X1 and X2 of the MEMS micro-vibration mirror X-axis, so that after one movement in the X-axis direction, the two voltages X1 and X2 are fixed; 3) Repeating steps 1) and 2) in a cycle until the last detection area of ​​the visualization imaging unit is scanned; 4) Then, from the last detection area of ​​the visualization imaging unit, scan along the opposite path according to 1), 2), and 3) to the initial position of the set scanning path.

[0070] Example 7 For long-distance pipeline inspection, the MEMS micro-vibration mirror can be set to linear scanning, and a large-scale inspection can be achieved by using the linear motion of drones, cars or electric vehicles. Fig. 9 As shown in the figure, from left to right, and then from right to left. Fig.10 As shown, the pipeline is covered with a line scanning spot, and the pipeline is scanned through the linear motion of the car.

[0071] The scan path is set as: According to the detection area divided by the visualization imaging unit, the circular spot of the detection laser moves from the initial position along the X direction, first from left to right, then from right to left and back to the initial position; When scanning according to the set scanning path, the control steps of the four electrode voltages of the MEMS micro-mirror are as follows: 1) The signal processing and control unit controls the power supply unit to provide corresponding voltage values ​​to the two electrodes X1 and X2 of the MEMS micro-vibration mirror on the X axis, and fixes the voltages of the two electrodes Y1 and Y2 on the Y axis to achieve scanning in the X axis direction. After reaching the edge of the detection area on the X axis direction, the device returns to the initial position of the X axis in the opposite path. 2) Loop sequentially.

[0072] The scanning path of this embodiment is based on the linear motion of a motor vehicle or electric vehicle, and a large-scale long-pipeline scanning is achieved through the principle of linear motion to surface.

[0073] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A laser gas telemetry imaging system based on micro-vibration mirror scanning, characterized in that: include: A laser transceiver optical unit, a signal processing and control unit, a visualization imaging unit, an information fusion unit, a signal output display unit, and a power supply unit for providing power to each unit; The laser transceiver optical unit comprises a semiconductor laser, an aiming laser, a beam combiner, a collimation system, a MEMS micro-vibration mirror, a receiving lens and a photodetector array; the detection laser emitted by the semiconductor laser and the aiming laser emitted by the aiming laser are combined by the beam combiner and then collimated onto the MEMS micro-vibration mirror by the collimation system; The MEMS micro-vibration mirror has two axes, X and Y, and each axis has two electrodes; the MEMS micro-vibration mirror is connected to the signal processing and control unit and the power supply unit respectively, and the signal processing and control unit controls the power supply unit to provide the MEMS micro-vibration mirror with a voltage corresponding to a required deflection angle, so as to control the MEMS micro-vibration mirror to reflect the laser beam to a target detection area; The photoelectric detector array is used to receive the return light signal of the detection laser that passes through the target detection area, is absorbed by the target gas, is reflected back by the background reflector, and is collected by the receiving lens, and is transmitted to the signal processing and control unit after photoelectric conversion; The signal processing and control unit calculates the concentration information of the target gas in the target detection area according to the return light signal after photoelectric conversion; The visualization imaging unit is used to capture a visualization image of the detection area; The information fusion unit is connected to the signal processing and control unit, the visualization imaging unit and the signal output display unit, and is used to fuse the calculated gas concentration of the target detection area into the visualization image, and send the fused visualization image to the signal output display unit for visualization of the gas concentration.

2. A detection method based on the laser gas telemetry imaging system based on micro-vibration mirror scanning according to claim 1, characterized in that: The following steps are involved: (1) The signal processing and control unit controls the semiconductor laser and the aiming laser to emit light, and controls the visualization imaging unit to start capturing a visualization image; (2) The signal processing and control unit controls the power supply unit to provide corresponding voltage values ​​to the four electrodes X1, X2, Y1 and Y2 of the X and Y axes of the MEMS micro-vibration mirror, so that it scans the target detection area in a quasi-static mode or a uniform scanning mode according to a pre-set path; (3) The signal processing and control unit synchronously starts the corresponding dot matrix in the photodetector array to collect the received light signal according to the voltage value of the four electrodes of the MEMS micro-vibration mirror, and transmits the signal after photoelectric conversion to the signal processing and control unit for calculation and processing to obtain the gas concentration value; the scanning angle of the MEMS micro-vibration mirror is synchronized with the corresponding photodetector array collection; (4) When the calculated gas concentration value is greater than a preset alarm threshold, the signal processing and control unit adjusts the voltage values ​​of the four electrodes X1, X2, Y1 and Y2 of the MEMS micro-vibration mirror X and Y axes, so that the MEMS micro-vibration mirror performs a re-inspection near the alarm position according to the preset re-inspection times and re-inspection paths to confirm whether the alarm is a real leak alarm; (5) When a real leak alarm is confirmed, the signal processing and control unit sends the gas concentration to the information fusion unit; the information fusion unit draws the corresponding area of ​​the visualization image into images of different colors or grayscales according to the gas concentration, so as to intuitively present the shape and size of the leaking gas mass; the information fusion unit sends the drawn image to the signal output display unit for alarm and display; (6) After completing the specified re-inspection, the signal processing and control unit controls the MEMS micro-vibration mirror to continue scanning along the original path; (7) If it is confirmed to be a false leakage alarm, the signal processing and control unit discards the alarm and controls the micro-vibration mirror to continue scanning along the original path; (8) When shutting down, the signal processing and control unit controls the power supply of the laser and the MEMS micro-vibration mirror to be turned off, so that the laser is powered off and the position of the MEMS micro-vibration mirror returns to zero, and then the power supply of other parts of the system is turned off.

3. The detection method of the laser gas remote sensing imaging system based on micro-vibration mirror scanning according to claim 2 is characterized in that: Before the detection, the laser gas telemetry imaging system based on micro-vibration mirror scanning also calibrates the image of the visualization imaging unit, the scanning angle of the MEMS micro-vibration mirror and the photodetector array: The visualization imaging unit divides the visualization image into a plurality of detection areas according to the scanning angle of the MEMS micro-vibration mirror and the photodetector array; The signal processing and control unit controls the semiconductor laser and the aiming laser to emit light, and controls the MEMS micro-vibration mirror to scan, and respectively records and stores the corresponding relationship between the voltages of the four electrodes X1, X2, Y1 and Y2 of the MEMS micro-vibration mirror on the X-axis and Y-axis and the corresponding areas of the photodetector array and the visualized image.

4. The detection method of the laser gas telemetry imaging system based on micro-vibration mirror scanning according to claim 3 is characterized in that: The MEMS micro-vibration mirror is placed at the center of the receiving lens, and a hole is punched at the center of the receiving lens; A reflector is arranged between the collimation system and the MEMS micro-vibration mirror; The detection laser emitted by the semiconductor laser and the aiming laser emitted by the aiming laser are combined by the beam combiner, collimated by the collimation system and emitted by the reflector in sequence to the MEMS micro-vibration mirror. The MEMS micro-vibration mirror reflects the combined laser from the center of the hole of the receiving lens to the target detection area.

5. The detection method of the laser gas remote sensing imaging system based on micro-vibration mirror scanning according to claim 3 is characterized in that: The MEMS micro-vibration mirror is placed at the edge of the receiving lens to reflect the laser beam to the target detection area.

6. The detection method of the laser gas remote sensing imaging system based on micro-vibration mirror scanning according to claim 4 or 5, characterized in that: The scan path is set as: According to the detection area divided by the visualization imaging unit, the circular spot of the detection laser is continuously scanned from the initial position along the positive X-axis direction-the negative Y-axis direction-the negative X-axis direction-the positive Y-axis direction, from the outer layer to the center layer by layer and point by point to the center of the visualization imaging unit, and then scanned from the center of the visualization imaging unit along the opposite path to the initial position of the set scanning path; When scanning according to a set scanning path, the method for controlling the voltages of the four electrodes of the MEMS micro-vibration mirror includes: To achieve scanning in the X-axis direction: The signal processing and control unit controls the power supply unit to fix the voltage values ​​of the two electrodes Y1 and Y2 of the MEMS micro-vibration mirror Y axis, and provides corresponding voltage values ​​to the two electrodes X1 and X2 of the MEMS micro-vibration mirror X axis; To achieve scanning in the Y-axis direction: The signal processing and control unit controls the power supply unit to fix the voltage values ​​of the two electrodes X1 and X2 of the MEMS micro-vibration mirror X-axis, and provides corresponding voltage values ​​to the two electrodes Y1 and Y2 of the MEMS micro-vibration mirror Y-axis.

7. The detection method of the laser gas remote sensing imaging system based on micro-vibration mirror scanning according to claim 4 or 5, characterized in that: The scan path is set as: According to the detection area divided by the visualization imaging unit, the circular spot of the detection laser is scanned from the initial position along the Y direction from top to bottom to the lowest end in the Y direction, then moved rightward once along the X direction, then scanned from bottom to top along the Y direction to the highest end in the Y direction, then moved rightward once along the X direction, and the detection is cyclically performed in sequence until the last detection area of ​​the visualization imaging unit, and then the detection returns to the initial position of the scanning path along the opposite path; When scanning according to a set scanning path, the method for controlling the voltages of the four electrodes of the MEMS micro-vibration mirror includes: To achieve scanning in the X-axis direction: The signal processing and control unit controls the power supply unit to fix the voltage values ​​of the two electrodes Y1 and Y2 of the MEMS micro-vibration mirror Y axis, and provides corresponding voltage values ​​to the two electrodes X1 and X2 of the MEMS micro-vibration mirror X axis; To achieve scanning in the Y-axis direction: The signal processing and control unit controls the power supply unit to fix the voltage values ​​of the two electrodes X1 and X2 of the MEMS micro-vibration mirror X-axis, and provides corresponding voltage values ​​to the two electrodes Y1 and Y2 of the MEMS micro-vibration mirror Y-axis.

8. The detection method of the laser gas remote sensing imaging system based on micro-vibration mirror scanning according to any one of claims 3 to 5, characterized in that: The mirror size of the MEMS micro-vibration mirror is φ1~φ10mm, and the deflection angle is ±1°~±10°; The photodetector array is a 10×10 photodetector array.

9. The scanning method of the laser gas telemetry imaging system based on micro-vibration mirror scanning according to any one of claims 2 to 5, characterized in that: The laser gas telemetry imaging system based on micro-vibration mirror scanning also includes a positioning unit for obtaining the position information of the detection equipment and a target recognition module for identifying the target detection area; The positioning unit confirms whether the detection area has been entered according to the acquired detection device position information. If the detection area has been entered, the target recognition module is started to recognize the target detection area and obtain the azimuth information of the target to be detected in the target detection area.

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