TDLAS (Tunable Diode Laser Absorption Spectroscopy)-based methane ethane laser gas telemetering sensing system and method

Abstract

The invention discloses a TDLAS (tunable diode laser absorption spectroscopy)-based methane ethane laser gas telemetering sensing system and method. The system comprises a laser driving unit, a detection unit and a signal data processing unit which are connected in sequence, the detection unit is provided with a parabolic reflector assembly support, the center of the assembly support is fixedly provided with a rotary parabola off-axis concave surface receiving reflector, a near-infrared collimation laser is fixedly arranged below one side of the assembly support, and a middle-infrared collimation laser is fixedly arranged right below the assembly support; a dual-wavelength photoelectric detector is fixedly arranged at the focus of the cyclotron parabola off-axis concave surface receiving reflector, and the focus of the cyclotron parabola off-axis concave surface receiving reflector coincides with the photosensitive surface of the dual-wavelength photoelectric detector; the near-infrared collimation laser and the middle-infrared collimation laser are respectively connected with the laser driving unit, and the dual-wavelength photoelectric detector is respectively connected with the two independent signal data processing units and is used for receiving signals and inverting the gas concentration, so that different gases can be measured at the same time, and whether the leaked gas is natural gas or marsh gas can be distinguished.

Description

Technical Field

[0001] This invention belongs to the field of laser gas concentration detection technology, and particularly relates to a TDLAS methane and ethane laser gas remote sensing system and method. Background Technology

[0002] The statements in this section are merely background information relating to this disclosure and do not necessarily constitute prior art.

[0003] Detecting gas leaks in valve wells is a core component of ensuring urban public safety and a crucial line of defense for safe production across various industries, the safety of personnel, and environmental protection. Utilizing conventional intelligent monitoring terminals to monitor and transmit real-time data on methane, water level, and displacement within valve wells can effectively improve the efficiency and accuracy of gas leak detection in valve wells.

[0004] However, since many valve wells are typically located underground in relatively enclosed spaces, organic matter easily accumulates at the bottom. Furthermore, because the environment inside the well is conducive to the growth of anaerobic bacteria, this organic matter is decomposed by these bacteria in an oxygen-deficient environment, producing methane and other biogas components during this process. If only laser methane sensors are used to monitor gas leaks in valve wells, it is crucial to accurately distinguish whether the methane gas detected in the valve well is natural gas or biogas. This practical gas monitoring requirement presents new technical challenges to the gas sensor industry.

[0005] Currently, TDLAS telemetry systems that enable simultaneous detection of multiple gases typically combine multiple independent single-gas detection modules, each containing an independent laser, detector, and optical receiving path. While this approach can functionally achieve multi-gas detection, it results in a complex system structure, large size, and high cost. Furthermore, it suffers from difficulties in optical path calibration and challenges in ensuring complete consistency of optical path measurements across channels, limiting its application in portable, integrated devices. In addition, existing systems often employ coaxial optical designs or simple lens groups for optical reception, which can lead to crosstalk between the emitted laser and the receiving field of view, or insufficient receiving efficiency and signal-to-noise ratio during long-distance measurements. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, this invention provides a TDLAS methane and ethane laser gas remote sensing system and method, which can effectively distinguish and identify whether the leaked gas is natural gas or biogas, providing important technical support for the monitoring of gas leaks in valve wells.

[0007] To achieve the above objectives, one or more embodiments of the present invention provide the following technical solutions: In a first aspect, the present invention provides a TDLAS methane and ethane laser gas telemetry sensing system, comprising a laser driving unit, a detection unit and a signal data processing unit connected in sequence. The detection unit is equipped with a parabolic reflector assembly bracket. A cyclotron off-axis concave receiving reflector is fixed at the center of the cyclotron off-axis receiving reflector assembly bracket. A near-infrared collimating laser is fixed below one side of the cyclotron off-axis receiving reflector assembly bracket, and a mid-infrared collimating laser is fixed directly below the cyclotron off-axis receiving reflector assembly bracket. A dual-wavelength photodetector is fixed at the focal point of the cyclotron off-axis concave receiving reflector, with its photosensitive surface facing the reflecting surface of the cyclotron off-axis concave receiving reflector. The focal point of the cyclotron off-axis concave receiving reflector coincides with the photosensitive surface of the dual-wavelength photodetector. The near-infrared collimated laser and the mid-infrared collimated laser are respectively connected to the laser driving unit, which is used to tune and control the laser driving current; the dual-wavelength photodetector is respectively connected to two independent signal data processing units, which are used to receive signals and invert gas concentration.

[0008] In a further technical solution, a red laser sight is fixedly installed on the lower side of the other side of the parabolic reflector assembly bracket and connected to the laser drive unit.

[0009] In a further technical solution, the parallel laser beams emitted by the red laser sight, the near-infrared collimating laser, and the mid-infrared collimating laser are parallel to each other and parallel to the optical axis of the off-axis concave surface receiving mirror of the cyclotron parabola.

[0010] In a further technical solution, the red laser emitted by the red laser sight is parallel to the collimated laser, which is used to indicate the direction and position of the collimated laser, as well as the distance from the measurement system to the reflective point.

[0011] A further technical solution involves fixing a wavelength filter at the reflected light receiving port of the parabolic reflector assembly bracket.

[0012] In a further technical solution, the dual-wavelength photodetector is provided with two independent detector chips, which are respectively connected to two independent signal data processing units.

[0013] In a further technical solution, the signal data processing unit is also equipped with a temperature and pressure sensor, and transmits the data it collects to the display unit.

[0014] Further technical solutions also include a data storage unit and a wireless communication unit, which are respectively connected to the signal data processing unit.

[0015] Secondly, the present invention provides a method for remote sensing of methane and ethane laser gases based on TDLAS, comprising: Start the telemetry instrument equipped with the TDLAS methane and ethane laser gas telemetry sensing system and point the indicator laser beam at the target area to be measured; The near-infrared collimating laser and the mid-infrared collimating laser are driven synchronously or in a time-division manner to emit measurement lasers. The two measurement lasers and the indicator laser beam are emitted in parallel. After being absorbed by the gas under test and reflected by the far-end reflecting surface, the reflected light signal carrying the gas absorption information returns to the telemetry instrument. The off-axis concave surface receiving mirror of the cyclotron parabola receives the reflected light signal and reflects and focuses it onto the photosensitive surface of the dual-wavelength photodetector, while simultaneously obtaining the optical path distance from the telemetry instrument to the reflection point. The dual-wavelength photodetector converts the received optical signals into corresponding electrical signals and transmits them to the corresponding signal data processing units. Two independent signal data processing units amplify, filter, and demodulate the received electrical signals respectively. Based on the optical path distance and the spectral theory of TDLAS wavelength absorption, they invert the methane and ethane concentrations respectively and transmit them to the display unit for display.

[0016] A further technical solution involves all incident light parallel to the optical axis of the off-axis concave surface receiving mirror of the cyclotronic parabola converging surface converging surface converging surface converging surface converging surface onto the photosensitive surface of the photodetector after reflection by the cyclotronic parabola converging surface receiving mirror.

[0017] The above one or more technical solutions have the following beneficial effects: The system of this invention achieves simultaneous detection of lasers of different wavelengths by integrating a near-infrared collimating laser, a mid-infrared collimating laser, a cyclotron off-axis concave receiving mirror, and a dual-wavelength photodetector. It is also compact and portable.

[0018] This invention is based on Tunable Semiconductor Laser Absorption Spectroscopy (TDLAS) technology, employing a 1653nm wavelength laser source to detect methane gas and a 3348nm wavelength laser source to detect ethane gas. Therefore, it fully utilizes the outstanding advantages of this technology, namely, minimal impact of environmental factors on measurement results, short response time, high sensitivity, good selectivity, and the ability to simultaneously measure multiple gases. Due to the use of an open optical path gas detection method, the dual-wavelength telemetry instrument is suitable for various applications. Besides its application in monitoring gas leaks in valve wells, it can also be used in on-site gas concentration detection and hazardous gas leak monitoring in the petroleum industry. Because of the telemetry detection system, personnel can be kept away from the area of ​​the gas being measured, effectively ensuring the safety of personnel and equipment.

[0019] The remote sensing system of this invention incorporates a cyclotronic off-axis concave receiving mirror in its detection unit. This mirror collects and converges reflected light, making it suitable for lasers of any wavelength. Therefore, the remote sensing instrument can simultaneously detect different gases. Furthermore, a dual-wavelength photodetector is positioned at the focal point of the cyclotronic off-axis concave receiving mirror. When laser beams reflected from the gas being measured strike the mirror, these reflected beams are automatically converged onto the TO-can detector's detection unit. This not only reduces system complexity but also lightens the weight of the measurement system.

[0020] This invention can be applied to on-site gas concentration detection and hazardous gas leak monitoring in the petroleum industry. Because it uses a remote sensing detection system, the detection personnel can stay away from the area of ​​the gas being measured, thereby effectively ensuring the safety of personnel and equipment. Attached Figure Description

[0021] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0022] Figure 1 This is a side view of the TDLAS methane and ethane laser gas telemetry sensing system according to an embodiment of the present invention. Figure 2 This is a front structural schematic diagram of the TDLAS methane and ethane laser gas telemetry sensing system according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the structure of the off-axis concave receiving mirror of the gyroparabolic curve according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the structure of the parabolic reflector assembly bracket according to an embodiment of the present invention; Figure 5 This is a schematic diagram of two photosensitive chips with different wavelengths in a TO-can according to an embodiment of the present invention.

[0023] Among them, 1-shell, 2-wavelength filter, 3-parabolic reflector assembly bracket, 301-near-infrared collimating laser mounting hole, 302-red laser sight mounting hole, 303-mid-infrared collimating laser mounting hole, 304-dual-wavelength photodetector mounting hole, 4-cyclotronic off-axis concave receiving reflector, 5-red laser sight, 6-near-infrared collimating laser, 7-mid-infrared collimating laser, 8-display unit, 9-display unit circuit board, 10-dual-wavelength photodetector, 11-laser drive circuit and signal processing circuit, 12-handle. Detailed Implementation

[0024] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0025] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0026] Where there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0027] Example 1 like Figure 1 , Figure 2 As shown, this embodiment discloses a TDLAS methane and ethane laser gas telemetry sensing system, which includes a laser driving unit, a detection unit and a signal data processing unit connected in sequence. The detection unit is equipped with a parabolic reflector assembly bracket 3. A cyclotron off-axis concave receiving reflector 4 is fixed at the center of the parabolic reflector assembly bracket 3. A near-infrared collimating laser 6 is fixed below one side of the parabolic reflector assembly bracket 3. A mid-infrared collimating laser 7 is fixed directly below the parabolic reflector assembly bracket 3. A dual-wavelength photodetector 10 is fixed at the focal point of the cyclotron off-axis concave receiving reflector 4. Its photosensitive surface faces the reflecting surface of the cyclotron off-axis concave receiving reflector 4. The focal point of the cyclotron off-axis concave receiving reflector 4 coincides with the photosensitive surface of the dual-wavelength photodetector 10. The near-infrared collimated laser 6 and the mid-infrared collimated laser 7 are respectively connected to the laser driving unit, which is used to tune and control the laser driving current; the dual-wavelength photodetector 10 is connected to the signal data processing unit, which is used to receive and process signals.

[0028] The laser driving unit, detection unit, and signal data processing unit are integrated inside the telemetry instrument, and all three are located inside the outer casing 1.

[0029] In this embodiment, the laser driving unit is implemented using a laser driving circuit, and the near-infrared collimating laser 6, the mid-infrared collimating laser 7, and the red laser aiming device 5 are respectively connected to the output terminal of the laser driving circuit.

[0030] In this embodiment, the detection unit is used to convert the reflected laser signal after being absorbed by the gas into an electrical signal and send it to the signal data processing unit.

[0031] like Figure 3 , Figure 4 As shown, the parabolic reflector assembly bracket 3 is a cylindrical shell with a fixed photoelectric transceiver assembly bracket. It is fixed on the central axis inside the shell 1 and the two are coaxial. The parabolic reflector assembly bracket 3 can fix the off-axis concave receiving reflector 4 of the gyroparabola, the red laser aiming device 5, the near-infrared collimating laser 6, the mid-infrared collimating laser 7 and the dual-wavelength photodetector 10. The bottom of the cylindrical shell is provided with a dual-wavelength photodetector mounting hole 304 for mounting and fixing the dual-wavelength photodetector 10. The off-axis concave-surface receiving mirror 4 of the cyclotron parabola is fixed to the bottom of the parabolic mirror assembly bracket 3, with its parabolic reflecting surface facing the opening (i.e., the reflected light receiving port) of the parabolic mirror assembly bracket 3, and the two are coaxial; the near-infrared collimating laser 6, the mid-infrared collimating laser 7, and the red laser aiming device 5 are respectively fixed at preset positions below the parabolic mirror assembly bracket 3, namely the near-infrared collimating laser mounting hole 301, the mid-infrared collimating laser mounting hole 303, and the red laser aiming device mounting hole 302. The parallel laser beams emitted by the three lasers are parallel to each other and parallel to the optical axis of the off-axis concave-surface receiving mirror 4 of the cyclotron parabola.

[0032] A red laser sight 5 is fixedly installed on the lower side of the other side of the parabolic reflector assembly bracket 3. The red laser emitted by the sight 5 (indicating laser beam) is parallel to the laser emitted by the collimating laser (measuring laser), used to mark the direction measured by the telemetry instrument, and to measure the distance from the telemetry instrument to the reflector point in the measurement direction of the telemetry instrument. The red laser emitted by the red laser sight 5 is parallel to the gas detection collimating laser, used to indicate the direction and position of the laser emitted by the detection laser, and to measure the distance from the telemetry instrument to the reflector point.

[0033] Near-infrared collimated laser 6 uses a near-infrared laser collimated source with a wavelength of 1653nm to detect methane gas; mid-infrared collimated laser 7 uses a mid-infrared laser collimated source with a wavelength of 3348nm to detect ethane gas.

[0034] In some implementations, the collimating laser includes various lasers of different wavelengths, such as DFB, ICL, or QCL, thereby enabling the measurement of different gases other than methane and ethane (1653 nm and 3348 nm), such as methane and carbon monoxide (1653 nm and 4610 nm).

[0035] The optical axis of the off-axis concave gyroparabolic receiving mirror 4 is parallel to the optical axes of the two collimated lasers (near-infrared collimated laser 6 and mid-infrared collimated laser 7), and the beam exit end of the collimated laser is aligned with the receiving port end of the off-axis concave gyroparabolic receiving mirror 4.

[0036] A wavelength filter 2 is fixed at the reflected light receiving port of the parabolic reflector assembly bracket 3. The filter is used to shield short wavelengths of visible light. It is a light-transmitting protective glass window (protective light-transmitting oblique window) that can simultaneously transmit wavelengths of 1653nm and 3348nm, so as to isolate possible external pollution and protect the internal reflector and detector.

[0037] The dual-wavelength photodetector 10 is a specially designed dual-wavelength Tocan detector capable of detecting two different wavelengths. Its photosensitive surface is located at the focal point of the off-axis concave cyclotronic receiving mirror 4. The focal point of the off-axis concave cyclotronic receiving mirror 4 coincides with the photosensitive surface of the dual-wavelength photodetector 10, ensuring that all incident light beams entering the telemetry instrument's reflected light receiving port and parallel to its optical axis can be reflected by the off-axis concave cyclotronic receiving mirror 4 and converge onto the photosensitive surface of the detector. In other words, all incident light parallel to the optical axis of the off-axis concave cyclotronic receiving mirror 4, after passing through the wavelength filter 2 (which only allows wavelengths of 1653nm and 3348nm to pass through), and then reflected by the off-axis concave cyclotronic receiving mirror 4, converges onto the photosensitive surface of the photodetector.

[0038] Furthermore, such as Figure 5 As shown, the photosensitive surface of the specially designed dual-wavelength photodetector 10 consists of two independent detector chips arranged side-by-side at the center of the TO-can base. These two detector chips are used to detect wavelength signals of 1653nm and 3348nm, respectively, to obtain the concentration detection values ​​of methane and ethane. When the specially designed dual-wavelength TO-can photodetector is placed in the preset position below the parabolic reflector assembly bracket 3, the photosensitive surface of the dual-wavelength TO-can photodetector will coincide with the focal point of the off-axis concave surface receiving reflector 4 of the parabolic gyrograph.

[0039] In some implementations, when detecting methane carbon monoxide, two detector chips can be used to detect wavelength signals of 1653 nm and 4610 nm, respectively.

[0040] In this embodiment, the signal data processing unit is implemented using a signal processing circuit. The dual-wavelength photodetector 10 is connected to the input terminals of two independent signal processing circuits to receive and process the weak electrical signals from the detection unit. For example, it performs amplification, filtering, demodulation, and other processing based on the signal magnitude generated in the detector by the reflected light of two different wavelengths. Then, based on the detected absorption spectrum signals and the distance measured by the red laser sight 5, the concentrations of methane and ethane are calculated.

[0041] The signal data processing unit is equipped with temperature and pressure sensors to display the temperature and pressure values ​​during measurement, as well as to correct and compensate for errors caused by temperature and pressure. The temperature and pressure sensors are based on existing models suitable for telemetry instruments, which will not be described in detail here.

[0042] In this embodiment, the laser gas telemetry sensing system includes a display unit 8 for real-time display of measurement results. The display unit 8 is located on the rear end of the telemetry housing 1 where the detection unit is mounted, and is implemented using a display screen. It is connected to the display unit circuit board 9. In other words, a display screen is located on the outer rear end of the telemetry housing 1 to display the concentration, temperature, and pressure values ​​of methane and ethane gases.

[0043] The system also includes a handle 12 and a handle fixing clip. The handle 12 is located at the bottom of the telemetry housing 1 and is used for handheld use or fixed to a bracket. The handle 12 contains a rechargeable and replaceable portable rechargeable battery, which powers the laser gas telemetry sensing system.

[0044] The laser gas telemetry sensing system also includes a replaceable data storage unit, which is connected to the signal data processing unit and is used to store the data information detected and processed by the detection unit.

[0045] The system also includes a wireless communication unit (wireless transmission module) which is connected to the data processing unit and is used to transmit the data detected by the detection unit.

[0046] The display screen, data storage unit, and wireless communication unit are each connected to the output of the signal processing circuit. It should be noted that the circuits used in the system are all existing circuits, and will not be described in detail in this embodiment.

[0047] In this embodiment, the laser gas telemetry sensing system also includes a reflection unit, which is a pyramidal reflecting prism composed of three mutually perpendicular right-angled facets. The characteristic of this reflection unit is that incident light is reflected on the three right-angled facets and returns along its original path. The pyramid is insensitive to the incident angle of the light, allowing the reflected beam to return to the beam emitter along a path parallel to the incident beam. In practical applications, the reflection unit is placed at the far end of the laser's emission path to reflect the emitted laser light back into the laser gas sensing system.

[0048] The specifications of the laser gas telemetry sensing system are shown in the table below:

[0049] In summary, to overcome the shortcomings of existing laser methane gas detection technologies that cannot distinguish between natural gas and biogas, this invention proposes a TDLAS-based methane and ethane laser gas remote sensing system and method. In this system, a near-infrared 1653nm wavelength laser source is used to detect methane gas, and a mid-infrared 3348nm wavelength laser source is used to detect ethane gas. To enable the dual-wavelength telemetry instrument to operate simultaneously in two different bands, near-infrared and mid-infrared, this invention employs two key innovations: First, it utilizes a cycloidal off-axis concave mirror to collect reflected light from the gas being measured. This avoids the need for separate focusing lenses adapted for near-infrared and mid-infrared wavelengths, reducing the size, cost, and weight of the telemetry instrument. Second, it employs a specially designed Tocan detector, which incorporates photosensitive elements capable of detecting two different wavelengths: one for detecting a near-infrared beam at 1653 nm and the other for detecting a mid-infrared beam at 3348 nm. This allows for the simultaneous detection of different wavelengths of laser light, enabling the simultaneous detection of methane and ethane gases, thus solving the technical challenge of distinguishing between natural gas and biogas in the field.

[0050] Example 2 This embodiment discloses a remote sensing method for methane and ethane laser gases based on TDLAS, including: S1: Start the telemetry instrument equipped with the TDLAS methane and ethane laser gas telemetry sensing system and point the indicator laser beam at the target area to be measured; S2: The near-infrared collimating laser 6 and the mid-infrared collimating laser 7 are driven synchronously or in a time-division manner to emit measurement lasers. The two measurement lasers and the indicator laser beams are emitted in parallel. After being absorbed by the gas under test and reflected by the far-end reflecting surface, the reflected light signal carrying the gas absorption information returns to the telemetry instrument. The off-axis concave surface receiving mirror 4 of the cyclotron parabola receives the reflected light signal and reflects and focuses it onto the photosensitive surface of the dual-wavelength photodetector 10. At the same time, the optical path distance from the telemetry instrument to the reflection point is obtained by using the red laser aiming device 5. S3: The dual-wavelength photodetector 10 converts the received optical signals into corresponding electrical signals and transmits them to the two corresponding independent signal data processing units. S4: The two independent signal data processing units amplify, filter and demodulate the electrical signals based on the signal magnitudes generated by the reflected light of two different wavelengths in the detector. Combined with the optical path distance, and based on the TDLAS wavelength absorption spectral theory, they respectively invert the methane concentration and ethane concentration and transmit them to the display unit 8. S5: Display unit 8 receives methane concentration and ethane concentration and displays them in real time.

[0051] The optical signals detected by the two detector chips of the dual-wavelength photodetector 10 are amplified and processed by two signal processing circuits connected to the chips, and the corresponding gas concentration values ​​are calculated according to the corresponding calibration coefficients. The detection results are then displayed on the screen, stored in the storage unit, and transmitted to the control room via a wireless transmission module. The laser driving circuit and the signal processing circuit 11 can each use two separate circuits, each circuit connecting a laser and detector corresponding to a specific wavelength. Since the two circuits can independently detect two different wavelengths, two different gases can be measured simultaneously.

[0052] As an alternative, the same circuit can be used for detection, but it requires a time-division driving mode for two lasers and detectors of different wavelengths. At different times, different wavelength lasers are driven, and the signals measured by the corresponding detectors represent different gas concentrations, thereby distinguishing different gases being measured.

[0053] Furthermore, the laser driving unit and the signal data processing unit are two independent sets, each connected to the corresponding collimated laser and detection unit, forming two laser telemetry systems with different wavelengths. These two systems share the same cyclotron off-axis concave reflector and dual-wavelength TO-can detector. When the laser driving unit and the signal data processing unit use a single circuit, a time-division driving mode can be used to drive the two lasers with different wavelengths. The measured signals corresponding to different wavelength lasers represent different gas concentrations, thereby distinguishing different measured gases.

[0054] When the telemetry instrument is powered on and in working condition, the red laser sight 5 is pointed towards the target direction of the gas being measured, such as above the gas pipeline valve, inside the valve well, or the place that needs to be detected in the gas transmission station. At this time, since the beam of the red laser sight 5 is parallel to the beam of the measuring laser and the optical axis of the cyclotron off-axis concave surface receiving mirror 4 that receives the scattered light, the light reflected from the target gas and absorbed by the gas will be received by the cyclotron off-axis concave surface receiving mirror 4 and focused on the photosensitive surface of the dual-wavelength photodetector 10.

[0055] In the gas telemetry sensing system, two sawtooth wave drive currents drive a near-infrared collimated laser 6 for methane detection and a mid-infrared collimated laser 7 for ethane detection, respectively. The parallel laser beams emitted by these two lasers are parallel to each other and directed towards the area to be detected. When these two laser beams pass through the detected space and are reflected back to the telemetry instrument by the gas being measured or other reflective surfaces, the energy of these two laser beams varies with the gas concentration due to the spectral absorption of methane and ethane. This causes the light intensity of the two reflected laser beams to vary according to the concentrations of methane and ethane, respectively. The change occurs when the reflected laser beam absorbed by the gas being measured is reflected and focused onto the dual-wavelength photodetector 10 by the off-axis concave reflector 4 of the cyclotron parabola. The two photosensitive chips in the detector can then convert the two different reflected lights into two sets of corresponding electrical signals. The red laser aiming device 5 with ranging function measures the distance between the reflection point and the laser gas telemetry instrument. After processing the two sets of electrical signals, the average concentration of the gas being measured in the measurement optical path can be inverted and displayed on the screen. The measured data is stored and transmitted through the data storage unit and the wireless communication unit.

[0056] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0057] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A TDLAS-based methane and ethane laser gas remote sensing system, characterized in that, It includes a laser driving unit, a detection unit, and a signal data processing unit connected in sequence; The detection unit is equipped with a parabolic reflector assembly bracket. A cyclotron off-axis concave receiving reflector is fixed at the center of the cyclotron off-axis receiving reflector assembly bracket. A near-infrared collimating laser is fixed below one side of the cyclotron off-axis receiving reflector assembly bracket, and a mid-infrared collimating laser is fixed directly below the cyclotron off-axis receiving reflector assembly bracket. A dual-wavelength photodetector is fixed at the focal point of the cyclotron off-axis concave receiving reflector, with its photosensitive surface facing the reflecting surface of the cyclotron off-axis concave receiving reflector. The focal point of the cyclotron off-axis concave receiving reflector coincides with the photosensitive surface of the dual-wavelength photodetector. The near-infrared collimated laser and the mid-infrared collimated laser are respectively connected to the laser driving unit, which is used to tune and control the laser driving current; the dual-wavelength photodetector is respectively connected to two independent signal data processing units, which are used to receive signals and invert gas concentration.

2. The TDLAS methane and ethane laser gas telemetry sensing system as described in claim 1, characterized in that, A red laser sight is fixedly installed on the lower side of the other side of the parabolic reflector assembly bracket and is connected to the laser drive unit.

3. The TDLAS methane and ethane laser gas telemetry sensing system as described in claim 2, characterized in that, The parallel laser beams emitted by the red laser sight, near-infrared collimating laser, and mid-infrared collimating laser are parallel to each other and parallel to the optical axis of the off-axis concave receiving mirror of the cyclotron parabola.

4. The TDLAS methane and ethane laser gas telemetry sensing system as described in claim 2, characterized in that, The red laser emitted by the red laser sight is parallel to the collimated laser and is used to indicate the direction and position of the collimated laser, as well as the distance from the measurement system to the reflective point.

5. The TDLAS methane and ethane laser gas telemetry sensing system as described in claim 1, characterized in that, A wavelength filter is fixedly installed at the reflected light receiving port of the parabolic reflector assembly bracket.

6. The TDLAS methane and ethane laser gas telemetry sensing system as described in claim 1, characterized in that, The dual-wavelength photodetector has two independent detector chips, which are respectively connected to two independent signal data processing units.

7. The TDLAS methane and ethane laser gas telemetry sensing system as described in claim 1, characterized in that, The signal data processing unit is also equipped with a temperature and pressure sensor, and transmits the data it collects to the display unit.

8. The TDLAS methane and ethane laser gas telemetry sensing system as described in claim 1, characterized in that, It also includes a data storage unit and a wireless communication unit, which are respectively connected to the signal data processing unit.

9. A remote sensing method for methane and ethane laser gases based on TDLAS, characterized in that, include: Start the telemetry instrument equipped with the TDLAS methane and ethane laser gas telemetry sensing system and point the indicator laser beam at the target area to be measured; The near-infrared collimating laser and the mid-infrared collimating laser are driven synchronously or in a time-division manner to emit measurement lasers. The two measurement lasers and the indicator laser beam are emitted in parallel. After being absorbed by the gas under test and reflected by the far-end reflecting surface, the reflected light signal carrying the gas absorption information returns to the telemetry instrument. The off-axis concave surface receiving mirror of the cyclotron parabola receives the reflected light signal and reflects and focuses it onto the photosensitive surface of the dual-wavelength photodetector, while simultaneously obtaining the optical path distance from the telemetry instrument to the reflection point. The dual-wavelength photodetector converts the received optical signals into corresponding electrical signals and transmits them to the corresponding signal data processing units. Two independent signal data processing units amplify, filter, and demodulate the received electrical signals respectively. Based on the optical path distance and the spectral theory of TDLAS wavelength absorption, they invert the methane and ethane concentrations respectively and transmit them to the display unit for display.

10. The method for remote sensing of methane and ethane laser gas based on TDLAS as described in claim 9, characterized in that, All incident light parallel to the optical axis of the off-axis concave gyroparabolic receiving mirror converges onto the photosensitive surface of the photodetector after being reflected by the off-axis concave gyroparabolic receiving mirror.

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