Laser methane anti-dust interference detection method and system based on dual-light-path cooperation

Abstract

The invention relates to the technical field of gas monitoring, and discloses a laser methane dust interference resistance detection method and system based on dual-light-path collaboration, and the system comprises an open light path module, a closed light path module and a drive circuit module; the closed light path module comprises a spectroscope and a trapezoidal air chamber; the driving circuit module comprises a DFB laser, a first photoelectric detector and a second photoelectric detector; the DFB laser emits laser, the laser enters the closed light path module after being reflected by the open light path module, the closed light path module divides the laser into a test light beam and a reference light beam, and the test light beam is transmitted to the first photoelectric detector. According to the laser methane dust interference resistance detection method and system based on dual-light-path cooperation, the reference light path can be used for locking the position of a gas absorption characteristic, common-mode noise caused by dust can be reduced through dual-light-path absorbance signal elimination, and the dust interference influence is relieved from the aspect of signal demodulation.

Description

Technical Field

[0001] This invention relates to the field of gas monitoring technology, specifically to a laser methane anti-dust interference detection method and system based on dual-optical-path coordination. Background Technology

[0002] In practical applications of laser sensors, dust interference is one of the key challenges affecting detection accuracy. Solid particles in dust (such as dust and smoke) can cause Mie scattering or Rayleigh scattering of the laser light, causing some of the laser light to deviate from the original transmission path and become unreceived by the detector. At the same time, the particles themselves absorb some of the laser energy, resulting in a significant attenuation of the laser light intensity. This attenuation, combined with the absorption effect of the target substance, directly interferes with the correlation between light intensity changes and substance concentration. Furthermore, the distribution of dust particles (concentration and particle size) is random and dynamically changing. The light intensity fluctuations caused by scattering and absorption are unpredictable and can be converted into noise in the detection signal, leading to a decrease in the signal-to-noise ratio. This further obscures the effective signal generated by the absorption of the target substance, ultimately causing distortion in the detection results.

[0003] In existing technologies, dust is generally isolated through physical protection methods such as dustproof shells and sintered metal filters. The core logic is to block dust particles from entering the core area of ​​the sensor's optical path through structural design or filter media. However, in practical applications, this approach faces many intractable problems: Although the dustproof shell can block large-diameter dust particles, in order to ensure the smooth flow of the gas to be tested for real-time detection, a ventilation gap must be reserved, and small-diameter dust particles can still seep in through the gap. The filtration accuracy and air permeability of filtration media such as sintered metal filter screens exhibit a significant non-linear contradiction: if the filtration effect is to be improved to block finer dust, the pore size of the medium needs to be reduced, but this will greatly increase the gas flow resistance, resulting in untimely gas renewal, affecting the detection response speed, and even causing unstable detection signals due to air pressure differences. If the pore size is enlarged to ensure air permeability, it will be unable to effectively intercept fine particulate matter, and the dustproof effect will be greatly reduced. During prolonged use, physical protective components can gradually clog air passages and filter pores due to dust accumulation on their surface or inside. This not only continuously worsens air permeability but may also cause localized obstruction due to blockages, indirectly affecting the stability of optical path transmission. Furthermore, regular disassembly, cleaning, or replacement of components is required, increasing maintenance costs and downtime. This makes it difficult to meet the long-term stable detection needs in dusty environments such as coal mines and chemical plants. Summary of the Invention

[0004] (a) Technical problems to be solved: To address the shortcomings of existing technologies, this invention provides a laser methane anti-dust interference detection method and system based on dual-optical-path collaboration. This solves the problems mentioned in the background technology that physical dust prevention methods are difficult to balance dust interception effect and gas flow efficiency, and that long-term use is prone to clogging, leading to decreased detection accuracy and increased maintenance costs.

[0005] (II) Technical Solution: To achieve the above objectives, the present invention provides the following technical solution: a laser methane anti-dust interference detection method and system based on dual-optical-path coordination, comprising: Open optical path module, closed optical path module, driver circuit module; The enclosed optical path module includes a beam splitter and a trapezoidal gas chamber; The driving circuit module includes a DFB laser, a first photodetector, and a second photodetector. The DFB laser emits laser light, which is reflected by the open optical path module and then enters the closed optical path module. The closed optical path module splits the laser light into a test beam and a reference beam. The test beam is transmitted to the first photodetector, and the reference beam is transmitted to the trapezoidal gas chamber and then to the second photodetector. The signals from the first and second photodetectors are processed to reduce dust common-mode noise, thereby achieving methane detection with dust interference resistance.

[0006] Preferably, it further includes: The sensor housing integrates the open optical path module, the closed optical path module, and the drive circuit module.

[0007] Preferably, the open optical path module includes: A reflector mounting support is disposed inside the open optical path module; The first reflector is mounted on the laser reflection path of the open optical path module via the reflector mounting support, and is used to change the laser transmission direction emitted by the DFB laser so that the laser enters the closed optical path module. A wedge-shaped window is provided at the junction of the open optical path module and the closed optical path module to allow the laser beam reflected by the first reflector to pass through, while reducing the interference of dust scattering on the laser beam and ensuring that the beam enters the closed optical path module stably.

[0008] A laser mounting hole is provided on the open optical path module for the DFB laser to pass through and be installed, so that the DFB laser can accurately emit laser light into the open optical path module.

[0009] Preferably, the enclosed optical path module further includes: A sealing cover is installed at the opening of the main body of the enclosed optical path module to seal the opening of the enclosed optical path module and prevent external dust from entering and affecting the optical path. The first screw, the second screw, the third screw, and the fourth screw are respectively installed at the connection positions between the sealing cover and the main body of the closed optical path module, and are used to fasten the sealing cover and the closed optical path module to ensure airtightness. The second reflector is installed on the transmission path of the reference beam within the closed optical path module and is located between the beam splitter and the trapezoidal air chamber. It is used to change the direction of the reference beam so that it passes through the trapezoidal air chamber. The first and second fixing rubber rings are both installed at both ends of the trapezoidal air chamber inside the closed optical path module, and are sleeved on the outer periphery of the trapezoidal air chamber to position and fix the trapezoidal air chamber inside the closed optical path module. The first photodetector mounting hole and the second photodetector mounting hole are both opened on the side wall of the test beam convergence point corresponding to the closed optical path module, and are respectively used for the first photodetector and the second photodetector to pass through and install to receive the reference signal; A sealing ring is installed on the mating surface of the sealing cover and the main body of the enclosed optical path module to enhance the sealing performance of both and isolate external dust.

[0010] Preferably, the drive circuit module further includes; A drive circuit board is installed inside the sensor housing and connected to the first photodetector and the second photodetector; A signal acquisition interface is installed on the drive circuit board and connected to an external device to realize the transmission of detection signals acquired by the first photodetector and the second photodetector to the outside. A power supply interface is installed on the drive circuit board and connected to an external power source to provide power to the drive circuit board and the various electrical components within the drive circuit module.

[0011] Preferably, the trapezoidal gas chamber is filled with methane, and the product of its effective optical path L2 and concentration C2, L2×C2, is comparable in magnitude to the product of the effective optical path L1 of the open optical path and the concentration C1 to be measured, L1×C1, with a ratio range of 0.5-2.0.

[0012] Preferably, the signals collected by the first photodetector and the second photodetector include dust interference signals and gas absorption signals.

[0013] Preferably, the wedge-shaped window and beam splitter are wedge-shaped lenses with a 0.5° tilt angle to reduce beam deflection caused by dust scattering, and the first and second reflectors are gold-plated reflectors without tilt angle.

[0014] Preferably, the installation angles of the first reflector, the wedge window, the beam splitter, and the second reflector are all based on the central axis of transmission in the open optical path module, and are 45°, 90°, 44.62°, and 45.29° respectively.

[0015] The laser methane anti-dust interference detection system based on dual-optical-path coordination adopts the laser methane anti-dust interference detection method based on dual-optical-path coordination as described in the claims: The open optical path module fixes the first reflector through the reflector mounting support, and changes the transmission direction of the laser emitted by the DFB laser through the first reflector. The wedge-shaped window reduces the interference of dust scattering on the beam, and the laser mounting hole ensures that the laser accurately enters the closed optical path module. The enclosed optical path module is sealed and protected by the sealing cover and the sealing ring. The beam splitter splits the laser into a test beam and a reference beam. The second reflector guides the reference beam into the trapezoidal gas chamber. The first and second fixing rubber rings fix the trapezoidal gas chamber. The first and second photodetector mounting holes are provided for the corresponding photodetectors to be installed to receive the beam signal. The driving circuit module, the driving circuit board is connected to and controls the DFB laser to emit laser light, the first photodetector and the second photodetector respectively collect the test beam and the reference beam signals, the signal acquisition interface realizes the signal transmission to the outside, and the power supply interface is connected to an external power supply to power the module; The sensor housing integrates and packages the open optical path module, the closed optical path module, and the driving circuit module into a single structure. The signal processing unit receives dust-containing interference signals and gas absorption signals collected by the first photodetector and the second photodetector, cancels dust common-mode noise through background subtraction and division operations, and outputs methane concentration detection results with dust interference resistance.

[0016] (III) Beneficial Effects: The laser methane anti-dust interference detection method and system based on dual-optical-path coordination provided by this invention has the following beneficial effects: 1. The laser methane anti-dust interference detection method and system based on dual-optical-path coordination can use the reference optical path to lock the position of gas absorption characteristics, and the dual-optical-path absorbance signal elimination can reduce common-mode noise caused by dust, thus mitigating the impact of dust interference from the signal demodulation aspect.

[0017] 2. The laser methane anti-dust interference detection method and system based on dual optical path collaboration, by rearranging the optical path structure of the transmitter, gas chamber and receiver and adopting a compact packaging design, enables the experimental system that originally required precision optical platform adjustment to be modularized and integrated, significantly reducing the system size and assembly complexity, and facilitating mass production and on-site installation. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the sensor structure of the present invention; Figure 2 This is a schematic diagram of the driving circuit module of the present invention; Figure 3 This is a simulation diagram of the sensor's optical operation.

[0019] In the diagram: 1. Open optical path module; 11. Mirror mounting support; 12. First mirror; 13. Wedge-shaped window; 14. Laser mounting hole; 2. Enclosed optical path module; 21. Sealing cover; 22. First screw; 23. Second screw; 24. Third screw; 25. Fourth screw; 26. Beam splitter; 27. Second reflector; 28. First fixing rubber ring; 29. ​​Trapezoidal air chamber; 210. Second fixing rubber ring; 211. First photodetector mounting hole; 212. Second photodetector mounting hole; 213. Sealing ring; 3. Drive circuit module; 31. Drive circuit board; 32. DFB laser; 33. Signal acquisition interface; 34. First photodetector; 35. Second photodetector; 36. Power supply interface; 4. Sensor housing. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Example 1 refer to Figures 1 to 3 The preferred embodiment of the laser methane anti-dust interference detection method and system based on dual-optical-path coordination according to the present invention will be described in detail below: Open optical path module 1, closed optical path module 2, drive circuit module 3; The enclosed optical path module 2 includes a beam splitter 26 and a trapezoidal air chamber 29; The driving circuit module 3 includes a DFB laser 32, a first photodetector 34, and a second photodetector 35; The DFB laser 32 emits a laser beam, which is reflected by the open optical path module 1 and then enters the closed optical path module 2. The closed optical path module 2 splits the laser beam into a test beam and a reference beam. The test beam is transmitted to the first photodetector 34, and the reference beam is transmitted to the trapezoidal gas chamber 29 and then to the second photodetector 35. The signals from the first photodetector 34 and the second photodetector 35 are processed to reduce dust common-mode noise, thus achieving methane detection with resistance to dust interference. Through the design of dual-beam separation and synchronous detection, the test signal and the reference signal can simultaneously capture the common characteristics of dust interference. The interference is canceled out through calculation. Compared with the single-optical-path method that relies solely on physical protection, the anti-interference capability is improved at the signal level, ensuring that the methane concentration detection is not affected by fluctuations in dust concentration.

[0022] The drive circuit module 3 also includes; The drive circuit board 31 is installed inside the sensor housing 4 and connected to the first photodetector 34 and the second photodetector 35. As the core control unit, the drive circuit board 31 can not only receive the detector signal in real time, but also synchronously control the emission parameters of the DFB laser 32 to ensure the stability of the laser output, provide a basis for the consistency of the dual optical path signals, and avoid detection errors caused by laser parameter drift.

[0023] The signal acquisition interface 33 is installed on the driver circuit board 31 and connected to external devices to realize the transmission of detection signals acquired by the first photodetector 34 and the second photodetector 35 to the outside, thereby ensuring that the pre-processed dual optical path signals can be completely transmitted to the external analysis equipment, supporting subsequent data analysis and concentration inversion, and adapting to various external device interface standards to improve system compatibility.

[0024] The power supply interface 36 is installed on the drive circuit board 31 and connected to an external power source. It is used to provide power to the drive circuit board 31 and the various electrical components in the drive circuit module 3, so as to avoid problems such as abnormal emission of DFB laser 32 and signal distortion of the first photodetector 34 and the second photodetector 35 due to unstable power supply, and to ensure the continuous and reliable operation of the system.

[0025] The trapezoidal gas chamber 29 is filled with methane. The product of its effective optical path L2 and concentration C2, L2×C2, is comparable in magnitude to the product of the effective optical path L1 and the concentration C1 to be measured, L1×C1, in the open optical path. The ratio ranges from 0.5 to 2.0, which ensures that the gas absorption signal intensity of the reference optical path is at a similar level to that of the test optical path. This ensures that the two can effectively cancel the common-mode noise of dust during the operation. If the ratio exceeds this range, one of the signals will account for too high a proportion, and interference cancellation will not be achieved, thus affecting the detection accuracy.

[0026] The signals collected by the first photodetector 34 and the second photodetector 35 include dust interference signals and gas absorption signals. The first photodetector 34 and the second photodetector 35 respectively capture the composite signals of the two beams, providing a complete data basis for subsequent signal calculations. The dust interference signal is the common mode component of the two signals, and the gas absorption signal is the characteristic component of each. By separating the common mode component and the characteristic component, the methane concentration can be accurately extracted.

[0027] The following is the complete working process and working principle of the above embodiments: The power supply interface 36 of the drive circuit module 3 is connected to an external power source to provide stable power to the drive circuit board 31 and other electrical components such as the DFB laser 32, the first photodetector 34, and the second photodetector 35. The drive circuit board 31 controls the DFB laser 32 to emit laser light. After the laser light is precisely injected through the laser mounting hole 14 of the open optical path module 1, the first reflector 12, which is fixed by the reflector mounting support 11, changes the transmission direction. After passing through the wedge-shaped window 13 to reduce dust scattering interference, it enters the closed optical path module 2. The beam splitter 26 in the closed optical path module 2 splits the laser light into a test beam and a reference beam. The test beam is directly transmitted to the first photodetector 34, and the reference beam is changed in direction by the second reflector 27 and passes through the trapezoidal gas chamber 29 filled with methane before being transmitted to the second photodetector 35. The first photodetector 34 and the second photodetector 35 respectively collect dust interference signals and gas absorption signals. After the signals are processed by the drive circuit board 31, they are transmitted to the external signal processing unit through the signal acquisition interface 33. The dust common-mode noise is reduced by background subtraction and division operation, and finally the methane concentration detection result with anti-dust interference is output.

[0028] Example 2 refer to Figures 1 to 3 It also includes: The sensor housing 4, open optical path module 1, closed optical path module 2, and drive circuit module 3 are all integrated inside the sensor housing 4, providing physical protection for the internal components, reducing the impact of external environment such as collisions and humidity changes on the system, while optimizing the internal optical path layout, shortening the optical path transmission distance, and reducing optical loss.

[0029] Open optical path module 1 includes: The reflector mounting support 11 is located inside the open optical path module 1, providing a stable mounting reference for the first reflector 12, ensuring that the mounting angle of the first reflector 12 is accurate and not easily shifted, avoiding changes in the laser transmission direction due to loosening of the first reflector 12, and ensuring the stability and consistency of the optical path.

[0030] The first reflector 12 is mounted on the laser reflection path of the open optical path module 1 via the reflector mounting support 11, and is used to change the laser transmission direction emitted by the DFB laser 32 so that the laser enters the closed optical path module 2.

[0031] The wedge-shaped window 13 is located at the junction of the open optical path module 1 and the closed optical path module 2. It is used to allow the laser beam reflected by the first reflector 12 to pass through, while reducing the interference of dust scattering on the laser beam and ensuring that the beam enters the closed optical path module 2 stably.

[0032] A laser mounting hole 14 is provided on the open optical path module 1 for the DFB laser 32 to pass through and be installed, so that the DFB laser 32 can accurately emit laser light into the open optical path module 1. The position and size of the laser mounting hole 14 are precisely designed to ensure that the emitting end of the DFB laser 32 can be aligned with the central axis of the open optical path after installation, ensuring the accuracy of laser emission and avoiding the beam from being unable to be effectively reflected into the closed optical path module 2 due to installation deviation.

[0033] Enclosed optical path module 2 also includes: The sealing cover 21 is installed at the opening of the main body of the closed optical path module 2 to seal the opening of the closed optical path module 2 and prevent external dust from entering and affecting the optical path, causing problems such as beam scattering and reduced reflection efficiency.

[0034] The first screw 22, the second screw 23, the third screw 24 and the fourth screw 25 are respectively installed at the connection position between the sealing cover plate 21 and the main body of the closed optical path module 2, and are used to fasten the sealing cover plate 21 and the closed optical path module 2 to ensure the sealing performance. The second reflector 27 is installed on the transmission path of the reference beam inside the closed optical path module 2 and is located between the beam splitter 26 and the trapezoidal air chamber 29. It is used to change the direction of the reference beam so that it passes through the trapezoidal air chamber 29.

[0035] The first fixing rubber ring 28 and the second fixing rubber ring 210 are both installed at both ends of the trapezoidal gas chamber 29 inside the closed optical path module 2. They are fitted around the outer periphery of the trapezoidal gas chamber 29 to position and fix the trapezoidal gas chamber 29 inside the closed optical path module 2. By utilizing the elasticity of the rubber material, the trapezoidal gas chamber 29 can be accurately positioned to ensure that it is aligned with the transmission path of the reference beam. It can also buffer the influence of external vibration on the trapezoidal gas chamber 29, preventing the trapezoidal gas chamber 29 from shifting and causing the beam to be unable to pass through effectively. At the same time, it enhances the sealing of both ends of the trapezoidal gas chamber 29 to prevent internal methane gas leakage.

[0036] The first photodetector mounting hole 211 and the second photodetector mounting hole 212 are both located on the side wall of the test beam convergence point corresponding to the closed optical path module 2. They are used for the first photodetector 34 and the second photodetector 35 to pass through and receive reference signals. The positions of the first photodetector mounting hole 211 and the second photodetector mounting hole 212 must be precisely aligned with the beam convergence point to ensure that the receiving ends of the first photodetector 34 and the second photodetector 35 can capture the beam signal to the maximum extent, improve the sensitivity of signal acquisition, and at the same time provide a stable mounting structure for the first photodetector 34 and the second photodetector 35 to avoid detector displacement leading to incomplete signal acquisition.

[0037] The sealing ring 213 is installed on the mating surface of the sealing cover 21 and the main body of the enclosed optical path module 2 to enhance the sealing performance of the two and isolate external dust. At the same time, it works with the sealing cover 21 and screws to form multiple sealing protections and improve the dustproof effect.

[0038] The wedge-shaped window 13 and beam splitter 26 are wedge-shaped mirrors with a 0.5° tilt angle to reduce beam deflection caused by dust scattering. The first reflector 12 and the second reflector 27 are gold-plated reflectors without tilt angles. The 0.5° tilt angle design breaks the symmetrical propagation path of dust-scattered light, reduces the interference of scattered light on the main beam, and avoids signal acquisition distortion caused by beam deflection. The high reflectivity of the gold-plated reflectors reduces energy loss during laser transmission, ensuring that the signal strength of the two beams meets the detection requirements, while the without tilt angle design ensures the accuracy of the beam reflection direction.

[0039] The installation angles of the first reflector 12, wedge window 13, beam splitter 26, and second reflector 27 are all based on the central axis of transmission in the open optical path module 1, and are 45°, 90°, 44.62°, and 45.29° respectively. By using fixed angles, it can be ensured that the laser is accurately transmitted between each optical component along a preset path, avoiding beam deviation that could lead to optical path failure. At the same time, it ensures that the test beam and the reference beam can be accurately focused onto the corresponding photodetectors, thus guaranteeing the effectiveness of signal acquisition.

[0040] The following is the complete working process and working principle of the above embodiments: An external power supply is connected through the power supply interface 36 of the drive circuit module 3, providing stable power to the drive circuit board 31 and other electrical components within the module, such as the DFB laser 32, the first photodetector 34, and the second photodetector 35. The drive circuit board 31 controls the DFB laser 32 to emit laser light. After the laser light is precisely injected through the laser mounting hole 14 on the open optical path module 1, the first reflector 12, which is fixed by the reflector mounting support 11, changes the transmission direction and then passes through the wedge-shaped window 13 with an installation angle of 90° to enter the closed optical path module 2. The sealed optical path module 2 achieves sealing protection through the tight connection of the sealing cover plate 21, the sealing ring 213 of the mating surface, and the first screw 22, the second screw 23, the third screw 24, and the fourth screw 25. The beam splitter 26 with an internal installation angle of 44.62° splits the laser into a test beam and a reference beam. The test beam is directly transmitted to the first photodetector 34 through the first photodetector mounting hole 211 on the side wall of the sealed optical path module 2. The reference beam changes direction through the second reflector 27 with an installation angle of 45.29°, passes through the trapezoidal air chamber 29 which is positioned and fixed by the first fixed rubber ring 28 and the second fixed rubber ring 210, and is transmitted to the second photodetector 35 through the second photodetector mounting hole 212. The first photodetector 34 and the second photodetector 35 respectively collect dust interference signals and corresponding gas absorption signals. After the signals are processed by the drive circuit board 31, they are transmitted to the external signal processing unit through the signal acquisition interface 33 on the drive circuit board 31. After calculation to reduce dust common-mode noise, the methane concentration detection result with anti-dust interference is finally output. In the whole process, the sensor housing 4 integrates and encapsulates the open optical path module 1, the closed optical path module 2, and the drive circuit module 3, providing protection for the internal components and ensuring the stable operation of the optical path and the circuit.

[0041] Example 3 refer to Figures 1 to 3 A laser-based methane dust interference detection system based on dual-optical-path coordination includes: The open optical path module 1 uses a reflector mounting support 11 to fix the first reflector 12, which changes the transmission direction of the laser emitted by the DFB laser 32. The wedge-shaped window 13 reduces the interference of dust scattering on the beam, and the laser mounting hole 14 ensures that the laser accurately enters the closed optical path module 2. Through the coordinated work of various components, the laser is stably transmitted in the open optical path, while initially resisting dust interference, laying the foundation for subsequent dual-optical-path signal acquisition. The fixation of the reflector and the accurate entry of the laser ensure the consistency of the optical path, while the wedge-shaped window 13 reduces the impact of dust on the beam from the source.

[0042] The enclosed optical path module 2 is sealed and protected by a sealing cover plate 21 and a sealing ring 213. The beam splitter 26 splits the laser into a test beam and a reference beam. The second reflector 27 guides the reference beam into the trapezoidal gas chamber 29. The first fixing rubber ring 28 and the second fixing rubber ring 210 fix the trapezoidal gas chamber 29. The first photodetector mounting hole 211 and the second photodetector mounting hole 212 are provided for the corresponding photodetectors to be installed to receive the beam signal. The driving circuit module 3 and the driving circuit board 31 are connected to and control the DFB laser 32 to emit lasers. The first photodetector 34 and the second photodetector 35 respectively collect the test beam and reference beam signals. The signal acquisition interface 33 realizes the external transmission of signals. The power supply interface 36 is connected to an external power supply to power the module.

[0043] The sensor housing 4 integrates and packages the open optical path module 1, the closed optical path module 2, and the drive circuit module 3 into a single structure. This not only reduces the system size and assembly complexity, but also reduces connection errors between modules, improves the coordination between the optical path and the circuit, and provides unified protection for internal components, enhancing the system's adaptability in complex field environments.

[0044] The signal processing unit receives dust-containing interference signals and gas absorption signals collected by the first photodetector 34 and the second photodetector 35. It cancels dust common-mode noise through background subtraction and division operations, and outputs methane concentration detection results that are resistant to dust interference. Background subtraction eliminates irrelevant interference such as baseline drift, and division operations specifically cancel dust common-mode noise, ultimately extracting accurate methane concentration information and ensuring the reliability of the detection results.

[0045] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A laser-based methane detection method with dust interference resistance based on dual-optical-path coordination, characterized in that, include: Open optical path module (1), closed optical path module (2), driving circuit module (3); The closed optical path module (2) includes a beam splitter (26) and a trapezoidal air chamber (29). The driving circuit module (3) includes a DFB laser (32), a first photodetector (34), and a second photodetector (35); The DFB laser (32) emits laser light, which is reflected by the open optical path module (1) and enters the closed optical path module (2). The closed optical path module (2) divides the laser light into a test beam and a reference beam. The test beam is transmitted to the first photodetector (34), and the reference beam is transmitted to the trapezoidal gas chamber (29) and then to the second photodetector (35). The signals from the first photodetector (34) and the second photodetector (35) are processed to reduce dust common-mode noise, thereby achieving methane detection with dust interference resistance.

2. The laser methane anti-dust interference detection method based on dual-optical-path coordination according to claim 1, characterized in that, Also includes: The sensor housing (4) integrates the open optical path module (1), the closed optical path module (2), and the driving circuit module (3).

3. The laser methane anti-dust interference detection method based on dual-optical-path coordination according to claim 1, characterized in that: The open optical path module (1) includes: A reflector mounting support (11) is disposed inside the open optical path module (1); The first reflector (12) is mounted on the laser reflection path of the open optical path module (1) via the reflector mounting support (11) to change the laser transmission direction emitted by the DFB laser (32) so that the laser enters the closed optical path module (2). A wedge-shaped window (13) is provided at the junction of the open optical path module (1) and the closed optical path module (2) to allow the laser beam reflected by the first reflector (12) to pass through, while reducing the interference of dust scattering on the laser beam and ensuring that the beam enters the closed optical path module (2) stably. A laser mounting hole (14) is provided on the open optical path module (1) for the DFB laser (32) to be installed through, so that the DFB laser (32) can accurately emit laser light to the open optical path module (1).

4. The laser methane anti-dust interference detection method based on dual-optical-path coordination according to claim 1, characterized in that: The closed optical path module (2) also includes: A sealing cover (21) is installed at the opening of the main body of the closed optical path module (2) to seal the opening of the closed optical path module (2) and prevent external dust from entering and affecting the optical path. The first screw (22), the second screw (23), the third screw (24) and the fourth screw (25) are respectively installed at the connection position between the sealing cover plate (21) and the main body of the closed optical path module (2) to fasten the sealing cover plate (21) and the closed optical path module (2) to ensure sealing. The second reflector (27) is installed on the transmission path of the reference beam in the closed optical path module (2) and is located between the beam splitter (26) and the trapezoidal air chamber (29) to change the direction of the reference beam so that it passes through the trapezoidal air chamber (29). The first fixing rubber ring (28) and the second fixing rubber ring (210) are both installed at both ends of the trapezoidal air chamber (29) inside the closed optical path module (2), and are sleeved on the outer periphery of the trapezoidal air chamber (29) to position and fix the trapezoidal air chamber (29) inside the closed optical path module (2); The first photodetector mounting hole (211) and the second photodetector mounting hole (212) are both opened on the side wall of the test beam convergence point corresponding to the closed optical path module (2), and are respectively used for the first photodetector (34) and the second photodetector (35) to pass through and be installed to receive the reference signal; A sealing ring (213) is installed on the mating surface of the sealing cover plate (21) and the main body of the closed optical path module (2) to enhance the sealing performance of both and isolate external dust.

5. The laser methane anti-dust interference detection method based on dual-optical-path coordination according to claim 2, characterized in that: The drive circuit module (3) also includes; The drive circuit board (31) is installed inside the sensor housing (4) and connected to the first photodetector (34) and the second photodetector (35); The signal acquisition interface (33) is installed on the drive circuit board (31) and connected to external devices to realize the transmission of the detection signals acquired by the first photodetector (34) and the second photodetector (35) to the outside. The power supply interface (36) is installed on the drive circuit board (31) and connected to an external power source to provide power to the drive circuit board (31) and the electrical components in the drive circuit module (3).

6. The laser methane anti-dust interference detection method based on dual-optical-path coordination according to claim 1, characterized in that: The trapezoidal gas chamber (29) is filled with methane. The product of its effective optical path L2 and concentration C2, L2×C2, is comparable to the product of the effective optical path L1 and the concentration C1 to be measured, L1×C1, with a ratio range of 0.5-2.

0.

7. The laser methane anti-dust interference detection method based on dual-optical-path coordination according to claim 1, characterized in that: The signals collected by the first photodetector (34) and the second photodetector (35) include dust interference signals and gas absorption signals.

8. The laser methane anti-dust interference detection method based on dual-optical-path coordination according to claim 3, characterized in that: The wedge window (13) and beam splitter (26) are wedge-shaped lenses with a 0.5° tilt angle to reduce beam deflection caused by dust scattering. The first reflector (12) and the second reflector (27) are gold-plated reflectors without tilt angle.

9. The laser methane anti-dust interference detection method based on dual-optical-path coordination according to claim 3, characterized in that: The installation angles of the first reflector (12), the wedge window (13), the beam splitter (26), and the second reflector (27) are all based on the central axis of transmission in the open optical path module (1), and are 45°, 90°, 44.62° and 45.29° respectively.

10. A laser methane anti-dust interference detection system based on dual-optical-path coordination, employing the laser methane anti-dust interference detection method based on dual-optical-path coordination as described in claim 9, characterized in that: The open optical path module (1) fixes the first reflector (12) through the reflector mounting support (11), and changes the transmission direction of the laser emitted by the DFB laser (32) through the first reflector (12). The wedge window (13) reduces the interference of dust scattering on the beam, and the laser mounting hole (14) ensures that the laser accurately enters the closed optical path module (2). The closed optical path module (2) is sealed and protected by the sealing cover plate (21) and the sealing ring (213). The beam splitter (26) splits the laser into a test beam and a reference beam. The second reflector (27) guides the reference beam into the trapezoidal air chamber (29). The first fixing rubber ring (28) and the second fixing rubber ring (210) fix the trapezoidal air chamber (29). The first photodetector mounting hole (211) and the second photodetector mounting hole (212) are provided for the corresponding photodetectors to be installed to receive the beam signal. The driving circuit module (3) and the driving circuit board (31) are connected to and control the DFB laser (32) to emit lasers. The first photodetector (34) and the second photodetector (35) respectively collect the test beam and reference beam signals. The signal acquisition interface (33) realizes the external transmission of signals. The power supply interface (36) is connected to an external power supply to power the module. The sensor housing (4) integrates and packages the open optical path module (1), the closed optical path module (2) and the driving circuit module (3) to form an integrated structure; The signal processing unit receives the dust interference signal and gas absorption signal collected by the first photodetector (34) and the second photodetector (35), cancels the dust common-mode noise through background subtraction and division operation, and outputs the methane concentration detection result with anti-dust interference.

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