Large-area multi-point gas monitoring system based on photoacoustic spectroscopy

Abstract

The application provides a large-area multi-point gas monitoring system based on photoacoustic spectroscopy, which is applied to multi-point gas concentration monitoring and comprises a laser output module, a gas detection module, a light path amplification module and a local demodulation module; a laser output module and a local demodulation module are shared by multiple points; each point in the multiple points is provided with a gas detection module and a light path amplification module. Laser collection of the preset wavelength and frequency and the effect of the light path amplification module enable the multiple points in a large area to share one laser output module, so that the system can generate gas voltage signals of the multiple points, and then the multi-point gas concentration information is obtained through calculation of the local demodulation module, thereby greatly improving the utilization rate of the device and reducing the material and manpower costs.

Description

Technical Field

[0001] This invention belongs to the field of gas monitoring technology, specifically relating to a large-area, multi-point gas monitoring system based on photoacoustic spectroscopy. Background Technology

[0002] In recent years, photoacoustic spectroscopy gas sensing technology has developed rapidly due to its advantages such as small size and high sensitivity. This technology can be applied to atmospheric environmental quality monitoring, power system safety testing, and non-invasive diagnosis of medical diseases.

[0003] However, existing photoacoustic spectroscopy gas sensing technologies require multiple complete gas detection devices to be deployed at various points within a large area for simultaneous detection of gas concentrations at multiple locations, and these devices must operate simultaneously. Another novel multi-point measurement photoacoustic spectroscopy technology uses fiber optic beam splitters to disperse the light source for multi-point measurement. However, applying this technology to large-area, real-time multi-point measurement makes it difficult to guarantee that the laser power transmitted through the fiber optic cable to each point will meet the detection requirements. Furthermore, this technology uses a tuning fork-type quartz crystal oscillator to detect sound waves, but the gap between the two arms of a quartz tuning fork is only 300 μm, which is unsuitable for the use of high-power excitation light sources.

[0004] Because multiple sets of gas detection equipment are required, and each set of gas detection equipment requires technicians to be deployed to the corresponding locations, and each system equipment includes its own laser emitting device, gas detection device and data demodulation device, this results in problems such as low utilization rate of equipment components and high material and labor costs. Summary of the Invention

[0005] To address the aforementioned problems in the existing technology, this invention provides a large-area, multi-point gas monitoring system based on photoacoustic spectroscopy.

[0006] The technical problem to be solved by this invention is achieved through the following technical solution:

[0007] This invention provides a large-area multi-point gas monitoring system based on photoacoustic spectroscopy, which is applied to gas concentration monitoring at multiple points. The large-area multi-point gas monitoring system based on photoacoustic spectroscopy includes: a laser output module, a gas detection module, an optical path amplification module, and a local demodulation module.

[0008] The multiple points share a single laser output module and a local demodulation module; each of the multiple points is equipped with a gas detection module and an optical path amplification module.

[0009] The laser output module is used to generate a laser and modulation signal with a preset wavelength and frequency for initial gas detection;

[0010] The multiple gas detection modules and multiple optical path amplification modules work together to collect the laser of the preset wavelength and frequency to form a modulated collected laser. Under the action of the modulated collected laser, gas voltage signals are generated at multiple points.

[0011] The local demodulation module is used to obtain multi-point gas concentration information through the gas voltage signals at multiple points and the modulation signal.

[0012] Optionally, when the number of test points is N, the large-area multi-point gas monitoring system based on photoacoustic spectroscopy further includes: a gas detection and optical path amplification module;

[0013] The laser output module is used to generate a scanning signal and a modulation signal. After combining the scanning signal and the modulation signal, a laser with a preset wavelength and frequency is formed. The laser with the preset wavelength and frequency is input into the optical path amplification module, and the modulation signal is simultaneously input into the local demodulation module.

[0014] The optical path amplification module is used to narrowband amplify the laser of the preset wavelength and frequency to obtain modulated laser, and input the modulated laser into the gas detection module;

[0015] The gas detection module is used to acquire the gas at the current location. The gas at the current location forms a current gas voltage signal under the action of the modulated laser, and the current gas voltage signal is input to the local demodulation module through wireless transmission.

[0016] The gas detection module is also used to collect the modulated laser to obtain modulated collected laser, and input the modulated collected laser into the gas detection and optical path amplification module via the optical path amplification module;

[0017] The gas detection and optical path amplification module includes N-1 gas detection modules and optical path amplification modules; the gas detection and optical path amplification module is used to generate gas voltage signals and modulate and collect lasers at N-1 points other than the current point, and transmit them to the local demodulation module and the corresponding optical path amplification module accordingly.

[0018] The local demodulation module is used to obtain a signal containing target gas concentration information through the modulation signal and the gas voltage signal, and to calculate multi-point gas concentration information through the signal containing target gas concentration information.

[0019] Optionally, the gas detection module includes: a beam collimator, a photoacoustic spectroscopy gas detection device, a light receiving device, an air inlet, an air outlet, and a wireless transmission module;

[0020] The gas at the current location is introduced into the photoacoustic spectroscopy gas detection device through the inlet and outlet.

[0021] The modulated laser passes through the beam collimator and enters the photoacoustic spectroscopy gas detection device.

[0022] The photoacoustic spectroscopy gas detection device uses the current point gas and the modulated laser to form a current gas voltage signal, and inputs the current gas voltage signal into the local demodulation module through wireless transmission.

[0023] Optionally, the light-collecting device includes: a converging lens and a laser beam collecting device;

[0024] After the modulated laser passes through the photoacoustic spectroscopy gas detection device, it is focused by the converging lens to the laser beam collecting device, which collects the modulated laser and transmits it to the corresponding optical path amplification module.

[0025] Optionally, the laser beam receiving device includes: a receiving lens, a collimating lens, a coupling lens, and a single-mode fiber arranged in sequence;

[0026] The light-collecting lens is used to collect the modulated laser to obtain an initial modulated collected laser; the collimating lens is used to collimate and calibrate the initial modulated collected laser to obtain a modulated collected laser; and the coupling lens is used to couple the modulated collected laser to a single-mode fiber and complete signal transmission through the single-mode fiber.

[0027] Optionally, the surface of the light-collecting lens is coated with an anti-reflection film of a predetermined thickness.

[0028] Optionally, the collimating lens is a biconvex lens with a diameter of 6 mm.

[0029] Optionally, the distance between the collimating lens and the light-collecting lens is the sum of the focal lengths of the collimating lens and the light-collecting lens.

[0030] Optionally, the coupling lens is a plano-convex lens with a diameter of 6 mm.

[0031] Optionally, the laser output module includes: a scanning signal source, a modulation signal source, a signal adder, and a distributed feedback laser;

[0032] The scanning signal source is used to output a scanning signal; the modulation signal source is used to output a modulation signal; the signal adder is used to combine the scanning signal and the modulation signal to form a combined signal.

[0033] The distributed feedback laser is used to feed back the combined signal to form a laser with a preset wavelength and frequency.

[0034] This invention provides a large-area multi-point gas monitoring system based on photoacoustic spectroscopy, applicable to gas concentration monitoring at multiple locations. The system includes a laser output module, a gas detection module, an optical path amplification module, and a local demodulation module. Multiple locations share a single laser output module and a local demodulation module; each location has a gas detection module and an optical path amplification module. The laser output module generates a laser and modulation signal of a preset wavelength and frequency for initial gas detection. Multiple gas detection modules and multiple optical path amplification modules work together to collect the laser of the preset wavelength and frequency to form a modulated laser. Under the action of the modulated laser, gas voltage signals are generated at multiple locations. The local demodulation module obtains gas concentration information at multiple locations from the gas voltage signals and modulation signals. By using the gas detection module to collect laser light of preset wavelength and frequency, and the optical path amplification module, multiple points in a large area can share a single laser output module. This allows the system to generate and transmit gas voltage signals at multiple points, and then calculate the gas concentration information at multiple points through the local demodulation module. This greatly improves the utilization rate of the device and reduces material and labor costs.

[0035] The present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0036] Figure 1 This is a structural diagram of a large-area, multi-point gas monitoring system based on photoacoustic spectroscopy provided in an embodiment of the present invention.

[0037] Figure 2 This is a schematic diagram of the structure of the laser beam collecting device provided in an embodiment of the present invention;

[0038] Figure 3 This is an internal system diagram of the gas detection module provided in an embodiment of the present invention;

[0039] Figure 4 This is a device appearance diagram of the laser output module provided in an embodiment of the present invention;

[0040] Figure 5 This is an external view of the gas detection module provided in an embodiment of the present invention;

[0041] Figure 6 This is a device appearance diagram of the optical path amplification module provided in an embodiment of the present invention;

[0042] Figure 7 This is a device appearance diagram of the local demodulation module provided in an embodiment of the present invention. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. It should be understood that the accompanying drawings in this application are for illustrative and descriptive purposes only and are not intended to limit the scope of protection of this application. In addition, it should be understood that the schematic drawings are not drawn to scale.

[0044] Furthermore, the described embodiments are merely some, not all, of the embodiments of this application. The components of the embodiments of this application described and illustrated herein can typically be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0045] It should be noted that, where there is no conflict, the features in the embodiments of this application can be combined with each other.

[0046] To address the problems of low equipment utilization and high material and labor costs in existing technologies, this invention provides a large-area multi-point gas monitoring system based on photoacoustic spectroscopy, applicable to gas concentration monitoring at multiple locations. Figure 1 This is a structural diagram of a large-area, multi-point gas monitoring system based on photoacoustic spectroscopy provided in an embodiment of the present invention. Figure 1 As shown, the large-area multi-point gas monitoring system based on photoacoustic spectroscopy includes: a laser output module 1, a gas detection module 6, an optical path amplification module 13, and a local demodulation module 16;

[0047] Multiple points share a single laser output module 1 and a local demodulation module 16; each of the multiple points is equipped with a gas detection module 6 and an optical path amplification module 13.

[0048] Laser output module 1 is used to generate a laser and modulation signal with a preset wavelength and frequency for initial gas detection;

[0049] Multiple gas detection modules 6 and multiple optical path amplification modules 13 work together to collect lasers of preset wavelengths and frequencies to form modulated collected lasers. Under the action of the modulated collected lasers, gas voltage signals are generated at multiple points.

[0050] The local demodulation module 16 is used to obtain multi-point gas concentration information through gas voltage signals and modulation signals at multiple points.

[0051] It should be noted that, in the embodiments of the present invention, the gas voltage signals at multiple points can specifically be the target gas voltage signals at multiple points.

[0052] This invention provides a large-area multi-point gas monitoring system based on photoacoustic spectroscopy, applied to gas concentration monitoring at multiple locations. The system includes a laser output module 1, a gas detection module 6, an optical path amplification module 13, and a local demodulation module 16. Multiple locations share one laser output module 1 and one local demodulation module 16. Each location has one gas detection module 6 and one optical path amplification module 13. The laser output module 1 generates a laser and modulation signal with a preset wavelength and frequency for initial gas detection. Multiple gas detection modules 6 and multiple optical path amplification modules 13 work together to collect the laser of the preset wavelength and frequency to form a modulated laser. Under the action of the modulated laser, gas voltage signals are generated at multiple locations. The local demodulation module 16 obtains gas concentration information at multiple locations from the gas voltage signals and modulation signals. By using the gas detection module 6 to collect lasers of preset wavelengths and frequencies, and the optical path amplification module 13, multiple points in a large area can share a single laser output module 1 to generate gas voltage signals for multiple points. Then, the gas concentration information for multiple points can be obtained through calculation by the local demodulation module 16, which greatly improves the utilization rate of the device and reduces material and labor costs.

[0053] Optionally, when the number of test points is N, the large-area multi-point gas monitoring system based on photoacoustic spectroscopy also includes: a gas detection and optical path amplification module 15;

[0054] The laser output module 1 is used to generate scanning signals and modulation signals. After combining the scanning signals and modulation signals, a laser with a preset wavelength and frequency is formed. The laser with the preset wavelength and frequency is input into the optical path amplification module 13, and the modulation signal is simultaneously input into the local demodulation module 16.

[0055] The optical path amplification module 13 is used to narrowband amplify the laser of preset wavelength and frequency to obtain modulated laser, and input the modulated laser into the gas detection module 6;

[0056] Gas detection module 6 is used to acquire the gas at the current point. The gas at the current point forms a current gas voltage signal under the action of the modulated laser, and the current gas voltage signal is wirelessly transmitted to the local demodulation module 16.

[0057] The gas detection module 6 is also used to collect the modulated laser to obtain the modulated collected laser, and input the modulated collected laser into the gas detection and optical path amplification module 15 via the optical path amplification module 13;

[0058] The gas detection and optical path amplification module 15 includes N-1 gas detection modules 6 and optical path amplification modules 13; the gas detection and optical path amplification module 15 is used to generate gas voltage signals and modulate the collected laser at N-1 points other than the current point, and transmit them to the local demodulation module 16 and the corresponding optical path amplification module 13 accordingly.

[0059] The local demodulation module 16 is used to obtain a signal containing target gas concentration information through the modulation signal and the gas voltage signal, and to calculate multi-point gas concentration information through the signal containing target gas concentration information.

[0060] It should be noted that in this embodiment of the invention, the local demodulation module 16 uses a local computer to calculate the target gas concentration information at each point in a large area. The specific calculation steps are as follows: The relationship between the gas voltage signal S and the target gas absorption coefficient α is as follows: S ~ αPQ / f0, where P is the laser power, Q is the quality factor, and f0 is the modulation frequency of the modulation signal. Thus, the target gas absorption coefficient α can be calculated from the measured gas voltage signal S. The relationship between the target gas absorption coefficient α and the gas concentration N is as follows: α = σN, where σ is the gas absorption cross section. Substituting the target gas absorption coefficient α into the formula yields the target gas concentration information.

[0061] Optionally, the gas detection module 6 includes: a beam collimator 7, a photoacoustic spectroscopy gas detection device 8, a light receiving device 9, an air inlet 10, an air outlet 11, and a wireless transmission module 12.

[0062] The gas at the current location is introduced into the photoacoustic spectroscopy gas detection device 8 through the air inlet 10 and the air outlet 11;

[0063] The modulated laser passes through the beam collimator 7 and enters the photoacoustic spectroscopy gas detection device 8;

[0064] The photoacoustic spectroscopy gas detection device 8 uses the current point gas and modulated laser to form a current gas voltage signal, and inputs the current gas voltage signal into the local demodulation module 16 through wireless transmission.

[0065] Optionally, the light-collecting device 9 includes: a converging lens 28 and a laser beam collecting device 29;

[0066] After the modulated laser passes through the photoacoustic spectroscopy gas detection device 8, it is focused by the converging lens 28 to the laser beam collecting device 29. The laser beam collecting device 29 collects the modulated laser and transmits it to the corresponding optical path amplification module 13.

[0067] Optionally, the laser beam receiving device 29 includes: a receiving lens 20, a collimating lens 21, a coupling lens 22, and a single-mode fiber 23 arranged in sequence.

[0068] The light-collecting lens 20 is used to collect the modulated laser to obtain the initial modulated collected laser; the collimating lens 21 is used to collimate and calibrate the initial modulated collected laser to obtain the modulated collected laser; and the coupling lens 22 is used to couple the modulated collected laser to the single-mode fiber 23 and complete the signal transmission through the single-mode fiber 23.

[0069] Optionally, the surface of the light-collecting lens 20 is coated with an anti-reflection film of a preset thickness.

[0070] Specifically, the light-collecting lens 20 is a biconvex lens with a diameter of 12.7 mm, and its surface is coated with an anti-reflection film of a preset thickness. The working wavelength of the anti-reflection film corresponds to the center wavelength of the output laser of the distributed feedback laser 5.

[0071] It is understood that, in this embodiment of the invention, by depositing an anti-reflection film of a preset thickness on the surface of the light-collecting lens 20, laser collection can be performed more efficiently.

[0072] Optionally, the collimating lens 21 is a biconvex lens with a diameter of 6 mm.

[0073] It is understood that, in this embodiment of the invention, by adding a collimating lens 21, the subsequent coupling lens 22 can perform laser processing better.

[0074] Optionally, the distance between the collimating lens 21 and the light-collecting lens 20 is the sum of the focal lengths of the collimating lens 21 and the light-collecting lens 20.

[0075] Optionally, the coupling lens 22 is a plano-convex lens with a diameter of 6 mm.

[0076] It should be noted that the distance between the coupling lens 22 and the single-mode fiber 23 needs to be such that the laser transmission angle through the coupling lens must meet the numerical aperture (NA) requirement of the single-mode fiber. Generally, the numerical aperture of a single-mode fiber is about 0.14, so the angle of the laser transmitted to the single-mode fiber must be less than 0.14 rad.

[0077] Optionally, the laser output module 1 includes: a scanning signal source 2, a modulation signal source 3, a signal adder 4, and a distributed feedback laser 5;

[0078] Scan signal source 2 is used to output the scan signal; modulation signal source 3 is used to output the modulation signal; signal adder 4 is used to combine the scan signal and the modulation signal to form a combined signal.

[0079] The distributed feedback laser 5 is used to feed back the combined signal to form a laser with a preset wavelength and frequency.

[0080] To illustrate the large-area, multi-point gas monitoring system based on photoacoustic spectroscopy provided in this embodiment of the invention, the operation of the entire system will be described using an example of 5 monitoring points. The equipment involved includes: one laser output module device 1, one local demodulation module device 16, five gas detection module devices 6, and five optical path amplification module devices 13.

[0081] Figure 1 The laser output module 1 includes: a scanning signal source 2, a modulation signal source 3, a signal adder 4, and a distributed feedback laser 5. The gas detection module 6 includes: a beam collimator 7, a photoacoustic spectroscopy gas detection device 8, a light receiving device 9, a gas inlet 10, a gas outlet 11, and a wireless transmission module 12. The optical path amplification module 13 includes an EDFA power amplifier and an FBG narrowband filter device 14. The gas detection and optical path amplification module 15 includes multiple laser output modules 1 and gas detection modules 6. The local demodulation module 16 includes: a wireless transmission module 17, a lock-in amplifier 18, and a local computer 19.

[0082] Figure 2 This is a schematic diagram of the structure of the laser beam receiving device 9 provided in an embodiment of the present invention. Figure 2 As shown, the laser beam receiving device 9 includes a receiving lens 20, a collimating lens 21, a coupling lens 22, and a single-mode fiber 23 arranged in sequence.

[0083] Figure 3 This is an internal system diagram of the gas detection module 6 provided in an embodiment of the present invention. Figure 3 As shown, the internal system of the gas detection module 6 includes: a beam collimator 7, an air inlet 10, an air outlet 11, a wireless transmission module 12, a quartz tuning fork sensor 27, a converging lens 28, a laser beam receiving device 29, a gain resistor 30, a gas sensing device 31, and an operational amplifier 32. Specifically, Figure 2 The laser beam receiving device 9 in the middle corresponds to Figure 3 The laser beam receiving device 29 in the middle.

[0084] Figure 4 This is a device appearance diagram of the laser output module 1 provided in an embodiment of the present invention, as shown below. Figure 4 As shown, it includes: a modulation signal output port 24, a power input 25, and an FC / PC interface 26.

[0085] Figure 5 This is an external view of the gas detection module 6 provided in an embodiment of the present invention, as shown in the figure. Figure 5 As shown, it includes: an air inlet 10, an air outlet 11, an FC / PC interface 26, and an FC / PC interface 33.

[0086] Figure 6This is a device appearance diagram of the optical path amplification module 13 provided in an embodiment of the present invention, as shown below. Figure 6 As shown, it includes: FC / PC interface 33 and FC / PC interface 26.

[0087] Figure 7 This is a device appearance diagram of the local demodulation module 16 provided in an embodiment of the present invention, such as... Figure 7 As shown, it includes: power input 25, reference signal input port 38, and USB interface 39.

[0088] First, a scanning signal, a triangular wave signal, is output from the scanning signal source 2 in the laser output module 1. Simultaneously, a modulation signal, a sinusoidal signal with a frequency half the resonant frequency of a quartz tuning fork, is output from the modulation signal source 3 to modulate the laser. The modulation signal source 3 also inputs the modulation signal as a reference signal to the lock-in amplifier 18 in the local demodulation module 16. The scanning and modulation signals are combined by the signal combiner 4 to drive the distributed feedback laser 5, which then outputs laser light of a preset wavelength and frequency through a single-mode fiber to the first optical amplification module 13.

[0089] Secondly, the optical path amplification module 13 performs narrowband amplification of the laser with the preset wavelength and frequency output from the laser output module 1. Since the detection sensitivity of photoacoustic spectroscopy gas sensing technology is proportional to the excitation light power, the narrowband amplification of the laser with the preset wavelength and frequency here can improve the performance of the subsequent gas detection module 6. After the laser with the preset wavelength and frequency is transmitted to the optical path amplification module 13 through a single-mode fiber, it will first be amplified by an erbium-doped fiber amplifier. The erbium-doped fiber amplifier (EDFA) can pump a 20mW laser to 1.36W, but the EDFA will also amplify the interference light near the non-absorption line. Therefore, a fiber optic circulator and a Bragg grating (FBG) are set at the back end of the EDFA. The laser with the preset wavelength and frequency enters the Bragg grating through the fiber optic circulator. The operating wavelength of the Bragg grating is the wavelength of the target gas absorption line, so it will reflect the wavelength light near the target gas absorption line into the fiber optic circulator, and then into the subsequent optical path, that is, into the gas detection module 6 at the first point. In addition, the optical path amplification module 13 is equipped with an optical power threshold system. Once the optical power is lower than a certain threshold, the optical path amplifier 13 will amplify the output laser of the laser output module 1, and vice versa.

[0090] Next, the first-point gas detection module 6 performs gas detection and related data transmission, and collects and transmits the laser light passing through the gas sensing device 31. The first optical path amplification module 13 outputs a laser light of a preset wavelength and frequency to the beam collimator 7, which then enters the gas sensing device 31. Under the action of the laser light of the preset wavelength and frequency, the target gas (entering through the inlet 10 and exiting through the outlet 11) generates periodic sound waves. This sound wave signal causes the quartz tuning fork sensor 27 to generate a weak alternating current, which is then converted into a gas voltage signal by the gain resistor 30 and the operational amplifier 32 and transmitted to the wireless transmission module 12. This gas voltage signal is received by the wireless transmission module 17 in the local demodulation module 16. The gas detection module 6 is also responsible for collecting and transmitting the laser light passing through the gas sensor 31. The laser light of a preset wavelength and frequency passes through the gas sensor 31 and is focused by the converging lens 28 onto the laser beam collecting device 29. The laser beam collecting device 29 collects this laser light to obtain modulated collected laser light and transmits it to a single-mode fiber, which then transmits it to the subsequent optical path amplification module. Due to insertion loss at the fiber optic interface, spatial light transmission loss, target gas absorption, and the collection loss of the collecting device, the actual modulated collected laser power collected by the collecting device is only in the hundreds of milliwatts range.

[0091] Next, a second optical amplification module amplifies the modulated laser in the optical fiber using a narrowband method. This compensates for the light loss during long-distance transmission in the fiber and filters out interference light near the absorption line of the non-target gas. Here, the second optical amplification module is placed near the second detection point. Therefore, the single-mode fiber connecting the gas detection module 6 at the first point and the second optical amplification module 13 will reach the km level, necessitating consideration of the laser's long-distance transmission loss in the fiber. The optical amplification module 13 operates in the same manner as the first optical amplification module 13. On one hand, it amplifies the modulated laser in the fiber to 1.5W using an erbium-doped fiber amplifier (EDFA). On the other hand, it filters out interference light near the absorption line of the non-target gas using a fiber circulator and a Bragg grating (FBG). Simultaneously, the threshold system in this module monitors the power of the modulated laser in the fiber in real time for selective amplification.

[0092] The working steps of the subsequent gas detection module 6 and optical path amplification module 13 are similar to those described above, and this process is repeated until the modulated and collected laser is transmitted through a single-mode optical fiber to the optical path amplification module 13 and gas detection module 6 at the fifth point.

[0093] Specifically, the gas detection modules 13 at the five locations operate simultaneously and transmit their respective detection data to the wireless transmission module 17 in the local demodulation module 16 via the wireless transmission module 12.

[0094] Finally, the local demodulation module 16 processes and analyzes the signals measured at the five points, and ultimately obtains the concentration information of the target gas at each target point. Specifically, the local demodulation module 16 outputs the data to the local computer 19 via a USB interface, and the local computer 19 processes and calculates the acquired data according to the gas concentration calculation formula to finally obtain the concentration information of the target gas at the five points.

[0095] In the several embodiments provided in this application, it should be understood that the disclosed systems and methods can be implemented in other ways. For example, the system embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection through some interfaces, devices, or units, and may be electrical, mechanical, or other forms.

[0096] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0097] In the various embodiments of this application, the functional units can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or in the form of hardware plus software functional units.

[0098] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A large-area, multi-point gas monitoring system based on photoacoustic spectroscopy, characterized in that, The large-area multi-point gas monitoring system based on photoacoustic spectroscopy, which is applied to gas concentration monitoring at multiple locations, includes: a laser output module (1), a gas detection module (6), an optical path amplification module (13), and a local demodulation module (16). The multiple points share a laser output module (1) and a local demodulation module (16), and each of the multiple points is provided with a gas detection module (6) and an optical path amplification module (13); The laser output module (1) is used to generate a laser and modulation signal with a preset wavelength and frequency for initial gas detection; Multiple gas detection modules (6) and multiple optical path amplification modules (13) work together to collect lasers of preset wavelength and frequency to form modulated collection lasers. Under the action of the modulated collection lasers, gas voltage signals at multiple points are generated. The local demodulation module (16) is used to obtain multi-point gas concentration information through the gas voltage signals at multiple points and the modulation signal; When the number of test points is N, the large-area multi-point gas monitoring system based on photoacoustic spectroscopy also includes: a gas detection and optical path amplification module (15); The laser output module (1) is used to generate a scanning signal and a modulation signal. After combining the scanning signal and the modulation signal, a laser with a preset wavelength and frequency is formed. The laser with the preset wavelength and frequency is input into the optical path amplification module (13), and the modulation signal is simultaneously input into the local demodulation module (16). The optical path amplification module (13) is used to narrowband amplify the laser of the preset wavelength and frequency to obtain a modulated laser, and input the modulated laser into the gas detection module (6); The gas detection module (6) is used to acquire the gas at the current location. The gas at the current location forms a current gas voltage signal under the action of the modulated laser, and the current gas voltage signal is input to the local demodulation module (16) through wireless transmission. The gas detection module (6) is also used to collect the modulated laser to obtain the modulated collected laser, and input the modulated collected laser into the gas detection and optical path amplification module (13) via the optical path amplification module (13); The gas detection and optical path amplification module (15) includes N-1 gas detection modules (6) and optical path amplification modules (13); the gas detection and optical path amplification module (15) is used to generate gas voltage signals and modulate and collect lasers at N-1 points other than the current point, and transmit them to the local demodulation module (16) and the corresponding optical path amplification module (13) accordingly. The local demodulation module (16) is used to obtain a signal containing target gas concentration information through the modulation signal and the gas voltage signal, and to calculate multi-point gas concentration information through the signal containing target gas concentration information. The gas detection module (6) includes: a beam collimator (7), a photoacoustic spectroscopy gas detection device (8), a light receiving device (9), an air inlet (10), an air outlet (11), and a wireless transmission module (12); The gas at the current location is introduced into the photoacoustic spectroscopy gas detection device (8) through the inlet (10) and outlet (11); The modulated laser passes through the beam collimator (7) and enters the photoacoustic spectroscopy gas detection device (8); The photoacoustic spectroscopy gas detection device (8) uses the current point gas and the modulated laser to form a current gas voltage signal, and inputs the current gas voltage signal into the local demodulation module (16) through wireless transmission.

2. The large-area multi-point gas monitoring system based on photoacoustic spectroscopy according to claim 1, characterized in that, The light-collecting device (9) includes: a converging lens (28) and a laser beam collecting device (29); After the modulated laser passes through the photoacoustic spectroscopy gas detection device (8), it is focused by the converging lens (28) to the laser beam collecting device (29), which collects the modulated laser and transmits it to the corresponding optical path amplification module (13).

3. The large-area multi-point gas monitoring system based on photoacoustic spectroscopy according to claim 2, characterized in that, The laser beam receiving device (29) includes: a receiving lens (20), a collimating lens (21), a coupling lens (22), and a single-mode fiber (23) arranged in sequence; The light-collecting lens (20) is used to collect the modulated laser to obtain an initial modulated collected laser; the collimating lens (21) is used to collimate and calibrate the initial modulated collected laser to obtain a modulated collected laser; the coupling lens (22) is used to couple the modulated collected laser to a single-mode fiber (23) and complete signal transmission through the single-mode fiber (23).

4. The large-area multi-point gas monitoring system based on photoacoustic spectroscopy according to claim 3, characterized in that, The light-collecting lens (20) is coated with an anti-reflection film of a preset thickness.

5. The large-area multi-point gas monitoring system based on photoacoustic spectroscopy according to claim 3, characterized in that, The collimating lens (21) is a biconvex lens with a diameter of 6 mm.

6. The large-area multi-point gas monitoring system based on photoacoustic spectroscopy according to claim 3, characterized in that, The distance between the collimating lens (21) and the light-collecting lens (20) is the sum of the focal lengths of the collimating lens (21) and the light-collecting lens (20).

7. The large-area multi-point gas monitoring system based on photoacoustic spectroscopy according to claim 3, characterized in that, The coupling lens (22) is a plano-convex lens with a diameter of 6 mm.

8. The large-area multi-point gas monitoring system based on photoacoustic spectroscopy according to claim 1, characterized in that, The laser output module (1) includes: a scanning signal source (2), a modulation signal source (3), a signal adder (4), and a distributed feedback laser (5); The scanning signal source (2) is used to output a scanning signal; the modulation signal source (3) is used to output a modulation signal; the signal adder (4) is used to combine the scanning signal and the modulation signal to form a combined signal. The distributed feedback laser (5) is used to feed back the combined signal to form a laser with a preset wavelength and frequency.

Images