Gas leak remote sensing system and method based on oxygen concentration spatial imaging

Abstract

This invention belongs to the field of gas detection technology, specifically providing a gas leak telemetry system and method based on spatial imaging of oxygen concentration. The system includes a computer, a digital lock-in amplifier, a signal generator, a laser emitting unit, an optical scanning unit, a signal receiving and processing unit, a hardware triggering unit, and a scanning control unit. This invention uses oxygen as a tracer and reference gas for detecting leaks of weak / non-absorbing characteristic gases. It combines TDLAS technology with high-speed spatial optical scanning imaging technology, creatively employing hardware parallel triggering and multi-level timing correction algorithms to achieve spatiotemporal registration. This precisely binds the oxygen concentration values ​​at each scanning point to their corresponding spatial coordinates, obtaining a visualization of the spatial distribution of oxygen concentration in the target monitoring area. This invention is of great significance for solving the industrial-grade leak monitoring problem of weak / non-absorbing characteristic gases and realizing long-distance, large-area, and high-precision leak telemetry and location in industrial scenarios.

Description

Technical Field

[0001] This invention belongs to the field of gas detection technology, specifically relating to a gas leak telemetry system and method based on spatial imaging of oxygen concentration. Background Technology

[0002] Tunable Diode Laser Absorption Spectroscopy (TDLAS) technology, due to its high sensitivity and selectivity, has been widely used for leak detection of gases with distinctive absorption lines, such as methane (CH4) and carbon dioxide (CO2). Its basic principle is to use a laser beam of a specific wavelength to pass through the test area. Because the target gas molecules selectively absorb this characteristic wavelength of laser light, causing the light intensity to attenuate, the concentration of the target gas can be deduced by detecting the intensity of the absorption spectrum.

[0003] However, existing laser absorption spectroscopy gas leak telemetry technology has significant limitations: (1) Target gas dependence: This technology can only detect gases with significant absorption characteristics in the laser band used. It cannot directly and effectively detect gases with symmetrical molecular structures such as hydrogen (H2), nitrogen (N2), and helium (He) that have extremely weak or no absorption lines in the near-infrared and mid-infrared bands. (2) Limited application scope: In many industrial scenarios (such as hydrogen energy, semiconductor manufacturing, inert gas protection, etc.), there is an urgent need for leakage monitoring of gases such as H2, N2, and He, but there is a lack of effective long-distance and large-scale telemetry methods. At present, monitoring can only be completed by contact sensors or manual inspection, which not only has low detection efficiency and slow response speed, but also makes it difficult to accurately locate the leakage source.

[0004] To address the challenge of detecting gases without infrared absorption characteristics, Lambrecht, Armin, et al. proposed a gas leak detection method based on atmospheric oxygen dilution. This method utilizes the principle of "indirect detection of non-infrared-absorbing gas leaks due to the ambient oxygen dilution effect." It measures O2 concentration using tunable laser spectroscopy (TLS) technology and employs extraction and long-distance detection methods for localization, successfully locating N2 leaks and determining a minimum detection leak rate of 0.1 mbar·L / s (LAMBRECHT A, MAIER E, PERNAU HF, et al. Gas Leak Detection by Dilution of Atmospheric Oxygen [J]. Sensors, 2017, 17 (12): 2804.). However, this research remains limited to single-point, static concentration detection verification in the laboratory, with detection distances limited to within 1 meter. Furthermore, it only enables single-point TLS detection and cannot achieve long-distance, large-scale, and high-precision leak telemetry and localization in industrial settings. Therefore, it does not yet solve the problem of industrial-grade leak monitoring for gases with weak or no absorption characteristics. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a gas leakage telemetry system and method based on oxygen concentration spatial imaging, so as to realize long-distance, large-area, and high-precision leakage telemetry and location of gases with weak / non-absorption characteristics.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: This invention first provides a gas leakage telemetry system based on spatial imaging of oxygen concentration. The system uses a computer as the control core, a digital lock-in amplifier as the signal hub, and a collaborative scanning control unit to achieve overall control of the signal modulation and acquisition link as well as the beam scanning and triggering link. Specifically, the system includes a computer, a digital lock-in amplifier, a signal generator, a laser emitting unit, an optical scanning unit, a signal receiving and processing unit, a hardware triggering unit, and a scanning control unit; The computer is communicatively connected to the digital lock-in amplifier and is used to set the operating parameters of the digital lock-in amplifier and perform concentration inversion, spatial registration, temporal cropping and image reconstruction processing on its output harmonic signal. The signal generator is electrically connected to the signal output module of the digital lock-in amplifier. The high-frequency sinusoidal modulation signal generated by the digital lock-in amplifier and the low-frequency sawtooth scanning signal generated by the signal generator are superimposed to form a mixed modulation wave, which drives the laser emitting unit to emit a laser beam toward the target monitoring area. The signal receiving and processing unit converts the diffusely reflected laser echo signal in the target monitoring area into a voltage signal. The voltage signal is demodulated into a harmonic signal by the digital lock-in amplifier and then transmitted to the computer. The above process is referred to as the signal modulation and acquisition link. The auxiliary output of the digital lock-in amplifier receives the trigger command from the computer and outputs a high-level trigger signal. The high-level trigger signal is transmitted in two parallel paths: one path is input to and turns on the hardware trigger unit to activate the trigger circuit of the scanning control unit, thereby driving the optical scanning unit to perform scanning action and achieve precise pointing control of the laser beam; the other path is connected back to the trigger input of the digital lock-in amplifier to trigger its internal data transmission and acquisition module to acquire the voltage signal returned by the signal receiving and processing unit, and demodulate it to obtain the first and second harmonic signals corresponding to oxygen absorption—the above process is referred to as the beam scanning and triggering link.

[0007] Furthermore, the laser emitting unit emits a laser beam of a specific wavelength, which corresponds to a characteristic absorption line of oxygen molecules. The laser emitting unit includes a current driver, a temperature controller, a collimator, and a near-infrared tunable semiconductor laser. The near-infrared tunable semiconductor laser is preferably located at 760nm near-infrared tunable semiconductor laser; The input terminal of the current driver receives a mixed modulation wave, and the output terminal is electrically connected to the laser to provide an adaptive driving current; the temperature controller is electrically connected to the laser to maintain a constant operating temperature of the laser; the collimator is coupled to the laser optical path to calibrate the diverging laser into a parallel narrow beam.

[0008] Furthermore, the optical scanning unit, also known as the two-dimensional galvanometer scanning system, is a high-precision, high-speed servo control system composed of a high-frequency two-dimensional galvanometer and a drive board. It receives the laser beam from the laser emitting unit and deflects it at high speed and with precision through its internal reflective mirror, so that the laser beam can perform two-dimensional or three-dimensional spatial scanning of the target monitoring area according to a preset path. The high-frequency two-dimensional galvanometer has a rapid deflection capability to achieve continuous scanning of the target area. It has a built-in galvanometer motor, laser reflector and integrated position sensor; the drive board integrates a position distinguisher, error amplifier, power amplifier and processor.

[0009] Furthermore, the signal receiving and processing unit includes a focusing lens, a filter, and a photodetector that are optically coupled in sequence; preferably, the filter is a 760nm narrowband filter; The focusing lens converges the laser echo signal, the filter removes background interference light, and the photodetector converts the filtered light signal into a voltage signal and outputs it to the digital lock-in amplifier.

[0010] Furthermore, the output terminal of the hardware trigger unit is connected to the trigger input terminal of the scan control unit. When the hardware trigger unit is turned on, it inputs a valid trigger signal to the trigger input terminal of the scan control unit to activate its trigger circuit.

[0011] Furthermore, the hardware triggering unit includes, but is not limited to, relays, solid-state relays, photoelectric switches, or electronic switch circuits.

[0012] Furthermore, the scanning control unit includes, but is not limited to, any hardware unit that implements scanning control functions, such as a control card, FPGA, microcontroller, dedicated driver chip, or embedded controller.

[0013] Furthermore, the computer has a built-in concentration inversion and imaging unit as well as a control and data analysis unit; The concentration inversion and imaging unit stores oxygen absorption spectral parameters and processes the harmonic signal output by the digital lock-in amplifier based on the principle of laser absorption spectroscopy (such as Lambert-Beer law) to calculate the oxygen concentration value at each scanning point on the laser scanning path. The control and data analysis unit includes a scanning control module, a spatial registration module, an imaging recognition module, and an alarm positioning module. The scanning control module is used to regulate the scanning path, speed, and range of the optical scanning unit (i.e., the scanning galvanometer system); the spatial registration module associates the oxygen concentration value calculated for each scanning point with the spatial coordinates of that scanning point in the actual monitoring area; the imaging recognition module generates an oxygen concentration distribution image based on the coordinates and concentration data, and identifies low-oxygen abnormal areas; the alarm positioning module triggers an alarm when a low-oxygen abnormal area is detected, and marks the coordinates of the leak point.

[0014] Furthermore, in the spatial registration module, the spatial coordinates of any scanning point on the field of view plane are calculated based on the deflection angle of the two-dimensional galvanometer, combined with the system installation position and geometric structure, through geometric projection relationships. The calculation formula for coordinates (x, y) is as follows: ; ; Among them, the e The mounting distance between the X-axis and Y-axis reflectors of the two-dimensional galvanometer; d θ is the distance from the rotation axis of the Y-axis reflector to the origin of the field of view plane coordinate system; x and θ yThese are the optical deflection angles of the X-axis and Y-axis reflectors, respectively, and the field of view is the ground or wall surface to be measured illuminated by the laser.

[0015] This invention also provides a long-distance telemetry method for gas leakage based on spatial imaging of oxygen concentration, which is implemented based on the above-mentioned system and includes the following steps: S1 System Initialization and Calibration The system is powered on and initialized. The laser emitting unit continuously and stably emits a laser beam, while the computer completes the configuration of system parameters, including the scanning path and alarm thresholds. S2 Hardware Parallel Triggering and Spatial Scanning The computer issues a trigger command, and the optical scanning unit drives the laser beam emitted by the laser emitting unit to scan the target monitoring area. The signal receiving and processing unit simultaneously collects the laser echo light signal and converts it into an electrical signal. S3 Oxygen Concentration Calculation The digital lock-in amplifier acquires the electrical signal mentioned in S2, extracts the harmonic signal through analytical processing, and transmits it to the computer. The computer uses a multi-level timing correction algorithm to complete the signal correction, and performs real-time calculations in combination with absorption spectroscopy technology to calculate the oxygen concentration at each scanning point. Construction of S4 oxygen concentration distribution map The computer correlates the oxygen concentration values ​​of all scan points with their spatial coordinates to construct a visualized two-dimensional or three-dimensional oxygen concentration distribution map. S5 Leak Detection and Location The computer analyzes the oxygen concentration distribution image using image processing algorithms, identifies low-oxygen abnormal areas below the alarm threshold, determines them as gas leak areas, triggers an alarm, and marks the coordinates of the leak point.

[0016] Furthermore, the multi-level timing correction algorithm includes the following procedures: (1) Initial timing compensation: By using the logic of "whether it is the first frame", the computer program automatically identifies the scanning start time and discards the initial invalid data in the system response time difference stage to eliminate the initial coordinate misalignment; (2) Concentration inversion and image reconstruction mapping: Real-time concentration calculation and spatial mapping are performed on the effective data after correction in step (1); (3) Inter-frame dead zone removal: By determining whether a single frame has ended, the computer program removes invalid data during the time period when the optical scanning unit returns to its original position after each complete frame scan is completed.

[0017] Furthermore, the multi-level time-series correction algorithm is executed synchronously with spatial scanning and oxygen concentration distribution map construction to achieve real-time acquisition, real-time correction, and real-time imaging.

[0018] Furthermore, the alarm threshold is the background oxygen concentration value measured under normal conditions without gas leakage, preferably 20.5% to 21%.

[0019] Furthermore, the image processing algorithm is one or more of the following: threshold segmentation, edge detection, and cluster analysis.

[0020] The detection principle of this invention is as follows: The problem of "detecting target gas (gas with no / weak infrared absorption)" is transformed into "detecting anomalies in oxygen concentration". Oxygen is used as a tracer and reference gas for gases with no / weak infrared absorption. Taking advantage of the physical phenomenon that the leakage of non-oxygen gas dilutes the oxygen in the ambient air, resulting in the local oxygen concentration in the leakage area being lower than the normal environmental level, a tunable semiconductor laser in the 760nm near-infrared band combined with TDLAS technology is used to achieve high-precision and high-sensitivity detection of ambient oxygen concentration.

[0021] This invention creatively combines high-sensitivity laser absorption spectroscopy gas sensing technology with high-speed spatial optical scanning imaging technology. A two-dimensional galvanometer scanning system enables long-distance two-dimensional / three-dimensional spatial scanning of the monitoring area using a laser beam. Combined with specific spatiotemporal registration and imaging algorithms, the oxygen concentration values ​​at each scanning point are precisely bound to their corresponding spatial coordinates, generating a spatial distribution map of oxygen concentration in the monitoring area. This transforms one-dimensional concentration measurement data into a two-dimensional or three-dimensional visualized distribution map, thereby achieving intuitive location of the leak point. By simply identifying continuous low-oxygen anomaly areas in the concentration distribution map, the occurrence of a gas leak can be determined, and the coordinates of the leak point can be marked and an automatic alarm can be triggered, enabling long-distance telemetry and precise location of gases with no or weak infrared absorption characteristics. Compared with existing technologies, this invention has the following significant advantages: (1) Realize long-distance, large-area non-contact telemetry This invention uses 760nm TDLAS detection technology combined with two-dimensional galvanometer spatial scanning to complete long-distance, large field of view, non-contact full-domain scanning monitoring, replacing traditional contact sensor single-point detection and manual inspection, and greatly improving detection coverage, work efficiency and response speed. (2) High detection sensitivity and strong anti-interference ability This invention employs hardware parallel triggering and a multi-level timing correction algorithm to achieve spatiotemporal registration, effectively eliminating timing misalignment, environmental stray light, and circuit noise interference. The detection accuracy and stability are significantly superior to similar technologies. (3) Visual imaging and precise location of leak points This invention correlates the oxygen concentration value of the scanning point with the corresponding spatial coordinates to generate an intuitive oxygen concentration distribution cloud map; combined with image processing algorithms, it automatically identifies low oxygen abnormal areas and can mark the coordinates of the leak point in real time, solving the problem of traditional technology being unable to visualize. (4) Strong detection universality This invention uses ambient oxygen as a tracer reference gas and indirectly determines the leak through the oxygen concentration dilution effect. It does not rely on the infrared absorption characteristics of the target gas itself and can be used to detect gases with no or weak infrared absorption, such as hydrogen, nitrogen, helium, and argon. It completely eliminates the dependence of traditional TDLAS technology on gas absorption spectra. (5) High security This invention employs a non-contact remote sensing method, eliminating the need for personnel to enter hazardous areas such as flammable, explosive, toxic, and harmful environments. It is suitable for high-risk / special industrial scenarios such as hydrogen energy stations, semiconductor manufacturing, chemical industries, and inert gas protection, offering a wider range of applications and higher detection safety. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the gas leak telemetry system of the present invention.

[0023] Figure 2 This is a schematic diagram of the scanning galvanometer system.

[0024] Figure 3 This describes the spatiotemporal registration workflow of the gas leakage telemetry system of the present invention.

[0025] Figure 4 This is a flowchart illustrating the working process of the gas leakage telemetry method of the present invention.

[0026] Figure 5 This is a schematic diagram of the spatial distribution of oxygen concentration when a gas leak occurs in Example 3 (a clear low-concentration anomaly area appears near the leak point).

[0027] Figure 6 This is a comparison chart of the theoretical true values ​​and reconstructed results of oxygen concentration distribution at different scanning positions in Example 4. Figure 6 (ac) are the actual locations of the helium gas bags in the upper right, middle, and lower left of the scanned area, respectively. Figure 6 (df) are the reconstructed spatial distribution maps of oxygen concentration in the upper right, middle, and lower left of the scanned area, respectively. Detailed Implementation

[0028] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0029] Example 1

[0030] This embodiment provides a gas leak telemetry system based on spatial imaging of oxygen concentration. The system uses a computer as its control core and a digital lock-in amplifier as its signal hub. A collaborative scanning control unit enables unified control of the signal modulation and acquisition links, as well as the beam scanning and triggering links, achieving synchronous hardware operation for indirect gas leak telemetry. Specifically, through a parallel hardware triggering mechanism, the system ensures synchronization of photoelectric signal acquisition and mechanical scanning actions on a time scale.

[0031] like Figure 1 As shown, the system includes: a computer, a digital lock-in amplifier, a signal generator, a laser emitting unit, an optical scanning unit, a signal receiving and processing unit, a hardware triggering unit (a relay in this embodiment), and a scanning control unit (a control card in this embodiment).

[0032] The laser emitting unit emits a laser beam of a specific wavelength, which corresponds to a characteristic absorption line of oxygen molecules. It includes a current driver, a temperature controller, a collimator, and a 760nm near-infrared tunable semiconductor laser. The input of the current driver receives a mixed modulation wave, and its output is electrically connected to the laser to provide an adaptive driving current. The temperature controller is electrically connected to the laser to maintain a constant operating temperature for the laser. The collimator is coupled to the laser's optical path to calibrate the divergent laser beam into a parallel, narrow beam.

[0033] The optical scanning unit, also known as the two-dimensional galvanometer scanning system, is a high-precision, high-speed servo control system composed of a high-frequency two-dimensional galvanometer and a drive board. It receives the laser beam from the laser emitting unit and deflects it at high speed and with precision through its internal reflective mirror, enabling the laser beam to scan the target monitoring area in two-dimensional or three-dimensional space along a preset path. The high-frequency two-dimensional galvanometer has a rapid deflection capability to achieve continuous scanning of the target area. It has a built-in galvanometer motor, a laser reflector, and an integrated position sensor. The drive board integrates a position distinguisher, an error amplifier, a power amplifier, and a processor.

[0034] The signal receiving and processing unit includes a focusing lens, a 760nm narrowband filter, and a photodetector that are optically coupled in sequence. The focusing lens converges the laser echo light signal, the filter filters out background interference light, and the photodetector converts the filtered light signal into a voltage signal and outputs it to a digital lock-in amplifier.

[0035] The computer has a built-in concentration inversion and imaging unit, as well as a control and data analysis unit. The concentration inversion and imaging unit stores oxygen absorption spectral parameters and processes the harmonic signals output by the digital lock-in amplifier based on the principle of laser absorption spectroscopy (such as Lambert-Beer's law) to calculate the oxygen concentration values ​​at each scanning point on the laser scanning path.

[0036] The control and data analysis unit includes a scanning control module, a spatial registration module, an imaging recognition module, and an alarm location module. The scanning control module is used to adjust the scanning path, speed, and range of the optical scanning unit (i.e., the scanning galvanometer system). The spatial registration module associates the oxygen concentration value calculated for each scanning point with the spatial coordinates of that scanning point. The imaging recognition module generates an oxygen concentration distribution image based on the coordinates and concentration data and identifies hypoxia anomaly areas. The alarm location module triggers an alarm when a hypoxia anomaly area is detected and marks the coordinates of the leak point.

[0037] Furthermore, in the spatial registration module, the spatial coordinates of any scanning point on the field of view plane are calculated based on the deflection angle of the two-dimensional galvanometer, combined with the system installation position and geometric structure, through geometric projection relationships. The specific principle is as follows: The two-dimensional galvanometer incorporates a built-in galvanometer motor, laser reflectors (in the X and Y directions), and a position sensor. When a laser beam is incident on the galvanometer, the oscillation of the two reflectors can be adjusted by controlling the deflection angle and oscillation speed of the galvanometer motor, thereby controlling the scanning angle and speed of the laser in the X and Y directions. If the telemetry distance is fixed (i.e., the distance between the light outlet of the galvanometer and the opposite obstacle), the entire scanning range of the laser can be calculated based on this distance.

[0038] like Figure 2 As shown in the diagram, a and b are reflecting mirrors. By rotating reflecting mirrors a and b, the incident light beam can be projected onto a specified position on the XY plane. The formula for calculating the coordinates (x, y) of the corresponding scanning point on the field of view plane is as follows: ; ; Among them, the e The mounting distance between the X-axis and Y-axis reflectors of the two-dimensional galvanometer; d The distance from the rotation axis of the Y-axis reflector to the origin of the field of view (i.e., the ground or wall surface (the surface to be measured) illuminated by the laser beam) is oriented in the same direction as the coordinate system. z Axis consistent; the θ x and θ y Let θ be the optical deflection angles of the X-axis and Y-axis mirrors, respectively. When x = y = 0, θ x =θ y =0.

[0039] In the system described in this embodiment, the computer is communicatively connected to the digital lock-in amplifier to set the operating parameters of the digital lock-in amplifier and to perform concentration inversion, spatial registration, temporal cropping and image reconstruction processing on the harmonic signal output by it.

[0040] In the signal modulation and acquisition link, the system uses a digital lock-in amplifier (DLP) as its core hub. A low-frequency sawtooth scanning signal (M) generated by a signal generator is input to the DLP and superimposed with a high-frequency sinusoidal modulation signal (~) generated internally by the DLP to form a hybrid modulation wave. This wave is transmitted to a current driver, which converts the hybrid modulation wave into a current suitable for the laser's operation, driving a 760 nm laser to emit a laser beam. A temperature controller maintains a constant operating temperature for the laser. The laser beam is collimated by a collimator and then directed towards the target monitoring area. The diffuse reflection echo signal carrying the concentration information of the gas to be measured is amplified by a focusing lens, filtered by a 760 nm narrowband filter to remove background interference bands, and then received by a photodetector. The photodetector converts the diffusely reflected laser echo signal from the target monitoring area into a voltage signal and transmits it back in real-time to the data transmission and acquisition module of the DLP. The DLP demodulates the voltage signal, extracts the first harmonic (1f) and second harmonic (2f) signals, and transmits them to a computer for subsequent concentration inversion and image reconstruction.

[0041] In the beam scanning and triggering link, the system constructs a parallel hardware triggering mechanism. The auxiliary output of the digital lock-in amplifier receives the trigger command from the computer and outputs a 3V high-level trigger signal. The trigger signal is transmitted in parallel through two paths: one path inputs to a relay, driving the relay to close, thereby activating the trigger circuit of the control card. The control card then drives the optical scanning unit (galvanometer scanning system) to perform continuous two-dimensional scanning tasks, achieving precise pointing control of the laser beam; the other path is connected back to the trigger input of the digital lock-in amplifier, triggering its internal data transmission and acquisition module to acquire the voltage signal returned by the signal receiving and processing unit, and demodulating it to obtain the first and second harmonic signals corresponding to oxygen absorption.

[0042] Example 2

[0043] The gas leak telemetry system described in this invention employs hardware parallel triggering and a multi-level timing correction algorithm to achieve spatiotemporal registration of the system. Based on the hardware parallel control mechanism of Embodiment 1, this embodiment further explains the multi-level timing correction algorithm in the data processing loop.

[0044] The hardware parallel control logic ensures complete time synchronization between the two links at the hardware level, avoiding the problem of "the galvanometer scans to point A, but the signal collected is the laser echo from point B" caused by software delays and poor system response, thus solving the problem of time misalignment between concentration values ​​and coordinates. The multi-level timing correction algorithm further addresses the inherent errors of the system hardware (such as startup response time difference and scan positioning dead zone) and the timing deviation of data transmission. Through software algorithms, it filters, corrects, and maps the collected raw data, solving the problems of coordinate misalignment within a single frame and splicing discontinuity between frames, ultimately achieving continuous, complete, and accurate oxygen concentration imaging of the monitoring area.

[0045] like Figure 3 As shown, the computer receives the 1f and 2f harmonic signals demodulated by the digital lock-in amplifier and sequentially executes the following multi-level timing correction algorithm to achieve accurate two-dimensional imaging of oxygen concentration: (1) Initial timing compensation: By using the logic of "whether it is the first frame", the computer program automatically identifies the scanning start time and forcibly discards the initial part of the data (corresponding to the system response time difference) to eliminate the initial coordinate misalignment; (2) Concentration inversion and image reconstruction mapping: Real-time concentration calculation and spatial mapping are performed on the effective data after correction in step (1) to complete the registration of "concentration, location and time" within a single frame scanning area; (3) Inter-frame dead zone removal: By determining whether a single frame has ended, the computer program performs inter-frame dead zone removal after each complete frame scan is completed, that is, deletes invalid data within the time period of the return to position, and realizes accurate inter-frame stitching in continuous mode.

[0046] Finally, the system determines the loop state based on whether to stop the experiment. If the experiment continues, the process will automatically backtrack to the data receiving stage to maintain continuous imaging; if the experiment is terminated, the termination protocol will be executed, the hardware will be shut down, and the process will end.

[0047] Example 3

[0048] This embodiment provides a method for remotely detecting leaked gas using the gas leak telemetry system of Embodiment 1. Its workflow is as follows: Figure 4 As shown, it includes the following steps: S1 System Initialization and Calibration After the system is powered on and initialized, the low-frequency sawtooth scanning signal output by the signal generator is superimposed with the high-frequency sinusoidal modulation signal output by the digital lock-in amplifier to drive the laser emitting unit to continuously and stably emit laser. At the same time, the computer completes the configuration of system parameters, including scanning path and alarm threshold. In this embodiment, under normal conditions with no leakage, the background oxygen concentration value of approximately 21% is measured and recorded, and 21% is used as the alarm threshold.

[0049] S2 Hardware Parallel Triggering and Spatial Scanning The computer issues a trigger command, and the optical scanning unit drives the laser beam emitted by the laser emitting unit to scan the target monitoring area. The signal receiving and processing unit simultaneously collects the laser echo light signal and converts it into an electrical signal.

[0050] S3 Oxygen Concentration Calculation The digital lock-in amplifier acquires the electrical signal mentioned in S2, extracts the harmonic signal through analytical processing, and transmits it to the computer. The computer uses a multi-level timing correction algorithm to complete the signal correction, and performs real-time calculations in conjunction with absorption spectroscopy technology to calculate the oxygen concentration at each scanning point.

[0051] Construction of S4 oxygen concentration distribution map The computer's control and data analysis unit correlates the oxygen concentration values ​​of all scan points with their spatial coordinates to construct a visualized two-dimensional or three-dimensional oxygen concentration distribution map.

[0052] S5 Leak Detection and Location The computer's control and data analysis unit uses image processing algorithms to analyze the oxygen concentration distribution image, locates and delineates continuous areas where the concentration is below a preset alarm threshold. These areas are identified as gas leak zones, and the system outputs a leak alarm and location information.

[0053] The following example demonstrates the system deployment described in Example 1, using the monitoring of hydrogen leakage at a hydrogen fuel cell station as an example: The telemetry system described in Example 1 is installed at a high point in the station area or on an inspection robot. The laser emitting unit, optical scanning unit, and signal receiving and processing unit are integrated into a protective cover and aimed at the pipelines, valves, and equipment areas that need to be monitored.

[0054] Parameter settings: The laser selected is a tunable diode laser with a center wavelength of 760nm, which is used to scan the oxygen A absorption band; the galvanometer is set with a horizontal scanning field of view of 120° and a vertical scanning field of view of 60°, and the scanning resolution is set to 0.1°; the alarm threshold is set to 20.7% (which can be adjusted according to environmental fluctuations and sensitivity requirements).

[0055] Operational monitoring: After system startup, the optical scanning unit controls the laser beam to scan the entire area in a grid pattern. For each scan point, the system measures the oxygen concentration along that path.

[0056] Leakage identification: such as Figure 5 As shown, under normal circumstances, the generated oxygen concentration cloud map has a uniform color, indicating a concentration above 20.7%. When a hydrogen leak occurs in a pipeline, the leaking hydrogen rises and spreads rapidly, diluting the surrounding air. In subsequent scan cycles, the system will generate a plume-like anomaly area with a significantly reduced oxygen concentration above the leak point.

[0057] Alarm and Action: The system detects the abnormal area with a concentration value below 20.7%, immediately triggers a high-level alarm, and highlights the specific location of the leak point with a red circle on the control room's visualization interface.

[0058] The computer displays the following alarm message: Warning! An area of ​​abnormal oxygen concentration detected! Position: (X: 5.5, Y: 4.5) - (X: 7.5, Y: 6.5) Minimum concentration: 16% @ (X: 6, Y: 5) Deduction: Suspected hydrogen leak! Security personnel can quickly proceed to the scene based on the location information.

[0059] Example 4

[0060] To further verify the detection of helium leaks, the experiment used a high-purity helium gas bag (15 cm × 15 cm) to simulate the spatial dilution effect of background oxygen, and used a fan to simulate actual airflow disturbance. The telemetry distance was 2.2 m, and the scanning coverage area was 37.5 cm × 36.25 cm. A helium gas bag with a thickness of 30 cm was fixed in the scanning area. Figure 6 (ac) represents the actual location of the helium gas bag, placed at the upper right, middle, and lower left of the scanning area, respectively. The reconstructed spatial distribution of oxygen concentration is verified by imaging at these three typical locations within the scanning area. Figure 6 As shown in (df), the actual physical distribution map is compared and analyzed with the imaging results, and the corresponding quantitative evaluation indicators are shown in Table 1.

[0061] Table 1 Quantitative evaluation indicators of imaging performance at different scanning positions

[0062] As shown in Table 1, under the condition of a system sampling step size of 1.25 cm, the maximum edge transition band span of the reconstructed images at the three typical experimental locations is approximately 1.2 cm, and the spatial positioning deviation between the geometric center of the reconstructed target and the theoretical true value location is better than 0.33 cm. Furthermore, the average absolute error of the inversion concentration in the target region remains stable within 0.38%, and the standard deviation of the maximum background region concentration is 0.2%. These quantitative results fully verify that the system possesses good accuracy and stability within the full scanning field of view.

[0063] The above are merely preferred embodiments of this application. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A gas leak telemetry system based on spatial imaging of oxygen concentration, characterized in that, It includes a computer, a digital lock-in amplifier, a signal generator, a laser emitting unit, an optical scanning unit, a signal receiving and processing unit, a hardware triggering unit, and a scanning control unit; The computer is communicatively connected to the digital lock-in amplifier and is used to set the operating parameters of the digital lock-in amplifier and perform concentration inversion, spatial registration, temporal cropping and image reconstruction processing on its output harmonic signal. The signal generator is electrically connected to the signal output module of the digital lock-in amplifier. The signals output by the two are superimposed to form a hybrid modulation wave, which drives the laser emitting unit to emit a laser beam toward the target monitoring area. The signal receiving and processing unit converts the laser echo light signal diffusely reflected from the target monitoring area into a voltage signal. The voltage signal is demodulated into a harmonic signal by the digital lock-in amplifier and then transmitted to the computer. The auxiliary output terminal of the digital lock-in amplifier receives the trigger command from the computer and outputs a high-level trigger signal. The high-level trigger signal is transmitted in parallel in two paths: one path is input to and turns on the hardware trigger unit to activate the trigger circuit of the scanning control unit, thereby driving the optical scanning unit to perform scanning action and realize precise pointing control of the laser beam; the other path is connected back to the trigger input terminal of the digital lock-in amplifier to trigger its internal data transmission and acquisition module to acquire and demodulate the voltage signal returned by the signal receiving and processing unit.

2. The system according to claim 1, characterized in that, The laser emitting unit includes a current driver, a temperature controller, a collimator, and a near-infrared tunable semiconductor laser; The input terminal of the current driver receives a mixed modulation wave, and the output terminal is electrically connected to the laser to provide an adaptive drive current. The temperature controller is electrically connected to the laser to maintain a constant operating temperature for the laser; the collimator is coupled to the laser's optical path to calibrate the diverging laser beam into a parallel narrow beam.

3. The system according to claim 1, characterized in that, The optical scanning unit consists of a high-frequency two-dimensional galvanometer and a drive board; the high-frequency two-dimensional galvanometer has a built-in galvanometer motor, a laser reflector and an integrated position sensor, and the drive board integrates a position distinguisher, an error amplifier, a power amplifier and a processor.

4. The system according to claim 1, characterized in that, The signal receiving and processing unit includes a focusing lens, a filter, and a photodetector that are optically coupled in sequence.

5. The system according to claim 1, characterized in that, The computer has a built-in concentration inversion and imaging unit, as well as a control and data analysis unit. The concentration inversion and imaging unit stores oxygen absorption spectral parameters, processes harmonic signals based on the principle of laser absorption spectroscopy, and calculates the oxygen concentration value at the laser scanning point. The control and data analysis unit includes a scanning control module, a spatial registration module, an imaging recognition module, and an alarm positioning module. The scanning control module regulates the scanning path, speed, and range of the optical scanning unit. The spatial registration module associates the oxygen concentration value of each scanning point with its spatial coordinates. The imaging recognition module generates an oxygen concentration distribution image based on the coordinates and concentration data and identifies hypoxia anomaly areas. The alarm positioning module triggers an alarm when a hypoxia anomaly area is detected and marks the coordinates of the leak point.

6. The system according to claim 5, characterized in that, In the spatial registration module, the formula for calculating the coordinates (x, y) of any scan point on the field of view plane is as follows: ； ； Among them, the e The mounting distance between the X-axis and Y-axis reflectors of the two-dimensional galvanometer; d θ is the distance from the rotation axis of the Y-axis reflector to the origin of the field of view plane coordinate system; x and θ y These are the optical deflection angles of the X-axis and Y-axis reflectors, respectively, and the field of view is the ground or wall surface illuminated by the laser.

7. A gas leakage telemetry method based on spatial imaging of oxygen concentration, characterized in that, The system implementation based on any one of claims 1-6 includes the following steps: S1 System Initialization and Calibration The system is powered on and initialized. The laser emitting unit continuously and stably emits a laser beam, while the computer completes the configuration of system parameters, including the scanning path and alarm thresholds. S2 Hardware Parallel Triggering and Spatial Scanning The computer issues a trigger command, the optical scanning unit drives the laser beam to scan the target monitoring area, and the signal receiving and processing unit simultaneously collects the laser echo light signal and converts it into an electrical signal. S3 Oxygen Concentration Calculation The digital lock-in amplifier acquires the electrical signal mentioned in S2, extracts the harmonic signal through analytical processing, and transmits it to the computer. The computer uses a multi-level timing correction algorithm to complete the signal correction, and performs real-time calculations in combination with absorption spectroscopy technology to calculate the oxygen concentration at each scanning point. Construction of S4 oxygen concentration distribution map The computer correlates the oxygen concentration values ​​of all scan points with their spatial coordinates to construct a visualized two-dimensional or three-dimensional oxygen concentration distribution map. S5 Leak Detection and Location The computer analyzes the oxygen concentration distribution image using image processing algorithms, identifies low-oxygen abnormal areas below the alarm threshold, determines them as gas leak areas, triggers an alarm, and marks the coordinates of the leak point.

8. The method according to claim 7, characterized in that, The multi-level timing correction algorithm includes the following procedures: (1) Initial timing compensation: By using the logic of "whether it is the first frame", the computer program automatically identifies the scan start time and discards the initial invalid data during the system response time difference stage; (2) Concentration inversion and image reconstruction mapping: Real-time concentration calculation and spatial mapping are performed on the effective data after correction in step (1); (3) Inter-frame dead zone removal: By determining whether a single frame has ended, the computer program removes invalid data during the time period when the optical scanning unit returns to its original position after each complete frame scan is completed.

9. The method according to claim 7, characterized in that, The multi-level time-series correction algorithm is executed synchronously with spatial scanning and oxygen concentration distribution map construction to achieve real-time acquisition, real-time correction, and real-time imaging.

10. The method according to claim 7, characterized in that, The alarm threshold is the background oxygen concentration value measured under normal conditions with no gas leaks.

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