A resonant cavity differential photoacoustic spectroscopy gas detection device

Abstract

This utility model discloses a resonant cavity differential photoacoustic spectroscopy gas detection device, belonging to the technical field of gas detection devices. It solves the problem that existing gas detection devices cannot maintain high sensitivity while achieving miniaturization. This utility model includes a laser emitter, the emitting end of which is connected to a detection module. The detection module has a first buffer cavity and a second buffer cavity at its two ends, respectively. The first and second buffer cavities are connected via a first resonant cavity and a second resonant cavity. The laser emitted from the emitting end of the laser emitter can pass through the first buffer cavity, the first resonant cavity, and the second buffer cavity sequentially. The first resonant cavity has a first and a second acoustic transmitter, and the second resonant cavity has a third acoustic transmitter. All three acoustic transmitters are connected to a signal processing system. By increasing the number of microphones, the detection sensitivity and anti-interference capability are significantly improved.

Description

Technical Field

[0001] This utility model relates to the technical field of gas detection devices, and in particular to a resonant cavity differential photoacoustic spectroscopy gas detection device. Background Technology

[0002] Resonant cavity photoacoustic spectroscopy is a gas detection technique. Its core principle is to enhance the sensitivity of gas detection by utilizing the dual resonance of an optical resonant cavity and an acoustic resonant cavity. While resonant photoacoustic spectroscopy offers significant advantages such as high sensitivity and high resolution, it still has some limitations in practical applications. Noise generated by ambient vibrations, gas turbulence, and other factors can easily interfere with its acoustic characteristics, leading to a decrease in system monitoring sensitivity and affecting the accuracy and reliability of detection results.

[0003] Differential cavity photoacoustic spectroscopy can effectively reduce interference from changes in the surrounding environment such as vibration, noise, and gas turbulence, providing a strong guarantee for improving detection sensitivity. In traditional methods of achieving high-sensitivity detection, increasing the optical path is usually adopted, but this inevitably leads to an increase in the size of the detection device, which contradicts the current trend of sensor miniaturization.

[0004] Chinese invention patent CN119619067B discloses a device and method for detecting SF6 decomposition products using a tunable photoacoustic spectrometer, belonging to the field of electrical equipment fault diagnosis and assessment. The device includes a laser control module, a resonant cavity module, an air intake module, a gas recovery module, and a data processing module. The laser control module outputs periodic laser light to the resonant cavity module. The air intake module is connected to the resonant cavity module and is used to input the gas to be tested into the resonant cavity module. The gas recovery module is connected to the resonant cavity module and is used to recover the gas detected by the resonant cavity module. The data processing module is connected to both the laser control module and the resonant cavity module, and is used to receive the reference signal output by the laser control module, process the electrical signal output by the resonant cavity module, and calculate the concentration of the gas to be tested. The resonant cavity module is used for gas analysis.

[0005] In this scheme, the direction of the optical path is changed by using a built-in right-angle prism, increasing the effective optical path between the infrared light and the gas, and improving the accuracy of gas measurement. Therefore, this scheme still relies on increasing the optical path to improve accuracy, inevitably increasing the overall size of the equipment and hindering miniaturization. Utility Model Content

[0006] To address the shortcomings in the aforementioned background technology, this utility model proposes a resonant cavity differential photoacoustic spectroscopy gas detection device, which solves the problem that existing gas detection devices cannot maintain high sensitivity while meeting miniaturization requirements.

[0007] The technical solution of this utility model is implemented as follows: A resonant cavity differential photoacoustic spectroscopy gas detection device includes a laser emitter, the emitting end of the laser emitter is connected to a detection module, the two ends of the detection module are respectively provided with a first buffer cavity and a second buffer cavity, the first buffer cavity and the second buffer cavity are connected through a first resonant cavity and a second resonant cavity, the laser emitted by the emitting end of the laser emitter can pass through the first buffer cavity, the first resonant cavity and the second buffer cavity in sequence; the first resonant cavity is provided with a first sound transmission device and a second sound transmission device, the second resonant cavity is provided with a third sound transmission device, and the first sound transmission device, the second sound transmission device and the third sound transmission device are all connected to a signal processing system.

[0008] Preferably, both the opening ends of the first buffer chamber and the second buffer chamber are provided with light-transmitting isolation plates. The detection module has an air inlet and an air outlet that respectively connect the first buffer chamber and the second buffer chamber.

[0009] Preferably, the detection module has symmetrical through holes I on both sides, vertically connecting to the first resonant cavity, and the first and second sound transmitting devices are respectively disposed in the two through holes I; the detection module has a through hole II vertically connecting to the second resonant cavity, and the third sound transmitting device is disposed in the through hole II. The first resonant cavity, the second resonant cavity, the first buffer cavity, and the second buffer cavity are all cylindrical chambers, and the first resonant cavity and the second resonant cavity are centrally symmetrically arranged along the axis of the first buffer cavity and the second buffer cavity.

[0010] Preferably, the signal processing system includes a filter amplification circuit module electrically connected to the first, second, and third microphones, the filter amplification circuit module being electrically connected to a microprocessor module, the microprocessor module being electrically connected to a laser temperature control drive circuit module, and the laser temperature control drive circuit module being electrically connected to a laser emitter.

[0011] Preferably, the first and third sound transmitting devices are electrically connected to differential circuit A, the second and third sound transmitting devices are electrically connected to differential circuit B, differential circuit A and differential circuit B are both electrically connected to superimposed circuit module, and superimposed circuit module is electrically connected to filter amplifier circuit module.

[0012] Preferably, the filter amplifier circuit module includes a filter amplifier circuit A module, a filter amplifier circuit B module, and a filter amplifier circuit C module. One end of each of the filter amplifier circuit A module, filter amplifier circuit B module, and filter amplifier circuit C module is electrically connected to the first microphone, the second microphone, and the third microphone, respectively, and the other end of each module is electrically connected to the microprocessor module.

[0013] Preferably, the laser emitter includes a fiber laser, and the emitting end of the fiber laser is provided with a collimator. The laser emitted by the fiber laser can be collimated by the collimator and then pass through the first buffer cavity, the first resonant cavity and the second buffer cavity in sequence.

[0014] Preferably, the laser emitter includes a spatial laser emitter, the emitting end of which is provided with a convex lens. The laser emitted by the spatial laser emitter can be focused and collimated by the convex lens and then exit through the first buffer cavity, the first resonant cavity and the second buffer cavity in sequence.

[0015] The beneficial effects of this utility model are: By increasing the number of microphones, especially by setting the first and second sound transmission devices on the first resonant cavity, the detection sensitivity and anti-interference ability are significantly improved. By setting the first and second resonant cavities and utilizing dual-cavity differential photoacoustic spectroscopy, interference from airflow turbulence noise, window noise, and external environmental noise is effectively suppressed, improving the system's signal-to-noise ratio, enhancing signal resolution, and further increasing detection sensitivity. Optimizing the resonant cavity structure layout, without relying on optical path extension, achieves high-sensitivity gas detection while meeting miniaturization requirements. This invention achieves significant improvements in sensitivity, anti-interference ability, and miniaturization, providing a reliable solution for high-precision gas detection. Attached Figure Description

[0016] To more clearly illustrate the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the structure of the first type of device of this utility model; Figure 2 This is a schematic diagram of the second type of device structure of this utility model; Figure 3 This is a schematic diagram of the device structure when the present invention is configured as a space-emitting laser. In the figure: 1: Laser emitter, 13: Detection module, 3: First buffer cavity, 8: Second buffer cavity, 5: First resonant cavity, 6: Second resonant cavity, 9: First sound transmission device, 10: Second sound transmission device, 11: Third sound transmission device, 12: Light-transmitting isolation plate, 4: Air inlet, 7: Air outlet, 2: Collimator, 14: Spatial light-emitting laser, 15: Convex lens. Detailed Implementation

[0018] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0019] like Figure 1 , 2 As shown in Embodiment 1, a resonant cavity differential photoacoustic spectroscopy gas detection device includes a laser emitter 1. The emitting end of the laser emitter 1 is connected to a detection module 13. The detection module 13 has a first buffer cavity 3 and a second buffer cavity 8 at its two ends, respectively. The first buffer cavity 3 and the second buffer cavity 8 are connected via a first resonant cavity 5 and a second resonant cavity 6. The laser emitted from the emitting end of the laser emitter 1 can pass through the first buffer cavity 3, the first resonant cavity 5, and the second buffer cavity 8 sequentially. By setting the first and second resonant cavities and utilizing dual-cavity differential photoacoustic spectroscopy technology, interference from airflow turbulence noise, window noise, and external environmental noise is effectively suppressed, improving the system's signal-to-noise ratio, enhancing signal resolution, and further improving detection sensitivity. The first resonant cavity 5 is equipped with a first microphone 9 and a second microphone 10. By increasing the number of microphones, the detection sensitivity and anti-interference capability are significantly improved. The second resonant cavity 6 is equipped with a third microphone 11. The first microphone 9, the second microphone 10, and the third microphone 11 are all connected to a signal processing system.

[0020] Specifically, in this embodiment, the first resonant cavity 5, the second resonant cavity 6, the first buffer cavity 3, and the second buffer cavity 8 are all cylindrical chambers. The first buffer cavity 3 and the second buffer cavity 8 are respectively opened at both ends of the detection module, and the first buffer cavity 3 and the second buffer cavity 8 have openings at their end faces to allow light to pass through. A light-transmitting isolation plate 12 is provided at the opening ends of both the first buffer cavity 3 and the second buffer cavity 8. In this embodiment, the light-transmitting isolation plate can be made of conventional light-transmitting materials such as glass. Sealing the opening ends of the first buffer cavity 3 and the second buffer cavity 8 with a light-transmitting isolation plate made of light-transmitting material achieves gas sealing, effectively preventing gas leakage, and ensures that the optical fiber enters the first resonant cavity 5 and stably exits from the resonant cavity, thus guaranteeing the smoothness of the optical path and the stability of optical performance.

[0021] Furthermore, the detection module 13 is provided with an air inlet 4 and an air outlet 7, respectively connecting the first buffer chamber 3 and the second buffer chamber 8. The air inlet 4 introduces the gas to be tested. The gas first enters the first buffer chamber 3, and after buffering, it enters the first resonant chamber 5 and the second resonant chamber 6. After the test is completed, the gas enters the second buffer chamber and is discharged through the air outlet 7. The first resonant chamber 5 and the second resonant chamber 6 are centrally symmetrically arranged along the axes of the first buffer chamber 3 and the second buffer chamber 8, maintaining the uniformity of gas and pressure within the first resonant chamber 5 and the second resonant chamber 6. The main function of setting up the first buffer chamber 3 and the second buffer chamber 8 is to make the gas flow more stable and reduce the influence of turbulence on the detection.

[0022] By optimizing the resonant cavity structure layout and eliminating reliance on optical path extension, high-sensitivity gas detection is achieved while meeting miniaturization requirements. This invention achieves significant improvements in sensitivity, anti-interference capabilities, and miniaturization, providing a reliable solution for high-precision gas detection.

[0023] In Example 2, based on Example 1, the detection module 13 has symmetrical through holes I on both sides, vertically connecting to the first resonant cavity 5. The first sound transmitting device 9 and the second sound transmitting device 10 are respectively disposed within the two through holes I. By providing through holes I and II, the first sound transmitting device 9 and the second sound transmitting device 10 can be installed perpendicular to the axis of the resonant position of the first resonant cavity 5. When the gas to be tested enters the first resonant cavity 5, under the action of a specific wavelength laser emitted by the laser emitter 1, the gas molecules undergo resonant absorption, thereby generating an acoustic signal. The first sound transmitting device 9 and the second sound transmitting device 10 sense the acoustic signal generated by the resonant absorption of the gas to be tested and convert it into an electrical signal for subsequent signal processing and analysis.

[0024] The detection module 13 has a through hole II that vertically connects to the second resonant cavity 6, and the third sound transmission device 11 is disposed within the through hole II. By providing the through hole II, the third sound transmission device 11 can be installed in the direction perpendicular to the axis of the second resonant cavity 6. The main function of the third sound transmission device 11 is to sense noise signals within the second resonant cavity 6. This noise may originate from interference factors such as vibrations and gas flows in the surrounding environment. By monitoring the noise signals and performing differential processing using a signal processing system, the influence of noise on the detection results can be effectively eliminated, improving the accuracy and stability of the detection.

[0025] In Example 3, based on Example 2, the signal processing system includes a filter amplification circuit module electrically connected to the first sound transmission device 9, the second sound transmission device 10, and the third sound transmission device 11. The filter amplification circuit module is used to filter and amplify the signal. The filter amplification circuit module is electrically connected to the microprocessor module, which is responsible for overall calculation and control. The microprocessor module is electrically connected to the laser temperature control drive circuit module, which is electrically connected to the laser emitter 1. The laser temperature control drive circuit module can accurately regulate the laser temperature to achieve stable wavelength output of the laser emitter.

[0026] As the first option, such as Figure 1 As shown, the first microphone 9 and the third microphone 11 are electrically connected to differential circuit A, and the second microphone 10 and the third microphone 11 are electrically connected to differential circuit B. Differential circuit A and differential circuit B are used for differential signal processing and analysis. Both differential circuit A and differential circuit B are electrically connected to the superposition circuit module, which performs multi-channel signal superposition processing. The superposition circuit module is also electrically connected to the filter and amplifier circuit module.

[0027] In practical use, the microprocessor module outputs a laser drive signal, which, through the laser temperature control drive module, precisely controls the temperature of the laser emitter 1, causing it to emit laser light covering the characteristic absorption wavelengths of the target gas. The laser emitted by the laser emitter 1, after collimation, passes through the first buffer cavity 3 and irradiates the first resonant cavity 5. After resonant absorption by the target gas in the first resonant cavity 5, the optical signal is converted into a periodic pressure fluctuation signal, i.e., an acoustic signal. The first and second acoustic devices 9 and 10 accurately capture these weak acoustic signals and convert them into voltage signals. No laser light passes through the second resonant cavity 6, which serves as a reference cavity. Noise generated by environmental vibrations, airflow turbulence, etc., is sensed by the third acoustic device 11 and converted into corresponding voltage signals. The voltage signals output by the first and second acoustic devices and the third acoustic device are processed by differential circuit A and differential circuit B, respectively, to subtract noise signals. These signals are then further optimized by the superposition circuit module and the filter amplification circuit module before being acquired by the sampling circuit of the microprocessor module. The microprocessor extracts the second harmonic information containing gas concentration from the acquired signal using lock-in amplification technology. Then, it calculates the concentration of the target gas using an interpolation algorithm and outputs the gas concentration. This provides reliable and accurate data support for monitoring and analysis in related fields and is widely used in environmental monitoring, industrial production and other fields.

[0028] As a second option, such as Figure 2As shown, in this embodiment, the filter amplification circuit module includes three modules: filter amplification circuit A, filter amplification circuit B, and filter amplification circuit C. One end of each module is electrically connected to the first microphone 9, the second microphone 10, and the third microphone 11, respectively, and the other end is electrically connected to the microprocessor module. The voltage signals output by the first, second, and third microphones are processed by filter amplification circuits A, B, and C, respectively, and then acquired by the sampling circuit of the microprocessor. The microprocessor module first processes the signals using a software differential signal algorithm and a superposition algorithm, then extracts the second harmonic information containing the gas concentration using lock-in amplification technology, and finally calculates the concentration of the target gas using an interpolation algorithm and outputs the gas concentration.

[0029] As a further optional implementation, the filter amplifier circuit module, the microprocessor module, the laser temperature control drive circuit module, and related modules from the above two optional schemes are all integrated on the signal processing board. The signal processing board is also fixedly equipped with an output / display module, which is electrically connected to the microprocessor module, thereby enabling the presentation of gas concentration data output by the microprocessor.

[0030] Example 4, based on Example 3, as a first optional solution, the laser emitter 1 includes a fiber laser. A collimator 2 is provided at the emission end of the fiber laser. The laser emitted by the fiber laser can be collimated by the collimator and then exit sequentially through the first buffer cavity 3, the first resonant cavity 5, and the second buffer cavity 8. Because fiber lasers require optical fibers for light transmission, the introduction of optical fibers into their overall structure increases the system's complexity and space occupation. The collimator mainly relies on the end-face coupling of the optical fiber and its internal optical design to achieve light collimation. Its volume is relatively large, and the requirements for fiber installation and fixation are high. However, the laser emitted by the fiber laser after passing through the collimator has higher collimation accuracy, resulting in more precise measurement results.

[0031] As a second option, such as Figure 3As shown, the laser emitter 1 includes a spatial laser 14, with a convex lens 15 at its emitting end. The laser emitted by the spatial laser 14 is focused and collimated by the convex lens 15 before exiting sequentially through the first buffer cavity 3, the first resonant cavity 5, and the second buffer cavity 8. Compared to the fiber laser of the first alternative, the spatial laser eliminates the intermediate transmission link of the optical fiber, simplifying the optical path structure. The convex lens, based on the principle of geometric optics, focuses and collimates the spatially emitted laser beam. Its structure is simple and compact, with the advantage of a significant reduction in system size. Smaller size means higher space utilization and more convenient installation and deployment, providing strong support for the integration and miniaturization of equipment and helping to promote the widespread application of photoacoustic spectroscopy detection technology in more fields.

[0032] In practical applications, the appropriate laser emitter type should be selected for gas detection based on the actual sensor size requirements.

[0033] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A resonant cavity differential photoacoustic spectroscopy gas detection device, characterized in that: The system includes a laser emitter (1), the emitting end of which is connected to a detection module (13). The detection module (13) has a first buffer cavity (3) and a second buffer cavity (8) at both ends. The first buffer cavity (3) and the second buffer cavity (8) are connected through a first resonant cavity (5) and a second resonant cavity (6). The laser emitted by the emitting end of the laser emitter (1) can pass through the first buffer cavity (3), the first resonant cavity (5), and the second buffer cavity (8) in sequence. The first resonant cavity (5) is provided with a first sound transmission device (9) and a second sound transmission device (10). The second resonant cavity (6) is provided with a third sound transmission device (11). The first sound transmission device (9), the second sound transmission device (10), and the third sound transmission device (11) are all connected to the signal processing system.

2. The resonant cavity differential photoacoustic spectroscopy gas detection device according to claim 1, characterized in that: Both the opening ends of the first buffer cavity (3) and the second buffer cavity (8) are provided with light-transmitting isolation plates (12).

3. The resonant cavity differential photoacoustic spectroscopy gas detection device according to claim 2, characterized in that: The detection module (13) has an air inlet (4) and an air outlet (7) that are respectively connected to the first buffer chamber (3) and the second buffer chamber (8).

4. The resonant cavity differential photoacoustic spectroscopy gas detection device according to claim 3, characterized in that: The detection module (13) has through holes I that are vertically connected to the first resonant cavity (5) on both sides, and the first sound transmission device (9) and the second sound transmission device (10) are respectively located in the two through holes I; the detection module (13) has through holes II that are vertically connected to the second resonant cavity (6), and the third sound transmission device (11) is located in through hole II.

5. The resonant cavity differential photoacoustic spectroscopy gas detection device according to claim 4, characterized in that: The first resonant cavity (5), the second resonant cavity (6), the first buffer cavity (3), and the second buffer cavity (8) are all cylindrical chambers. The first resonant cavity (5) and the second resonant cavity (6) are centrally symmetrically arranged along the axis of the first buffer cavity (3) and the second buffer cavity (8).

6. The resonant cavity differential photoacoustic spectroscopy gas detection device according to any one of claims 1 to 5, characterized in that: The signal processing system includes a filter amplification circuit module electrically connected to the first sound transmission device (9), the second sound transmission device (10), and the third sound transmission device (11). The filter amplification circuit module is electrically connected to the microprocessor module, the microprocessor module is electrically connected to the laser temperature control drive circuit module, and the laser temperature control drive circuit module is electrically connected to the laser emitter.

7. The resonant cavity differential photoacoustic spectroscopy gas detection device according to claim 6, characterized in that: The first sound transmitting device (9) and the third sound transmitting device (11) are electrically connected to the differential circuit A, the second sound transmitting device (10) and the third sound transmitting device (11) are electrically connected to the differential circuit B, the differential circuit A and the differential circuit B are both electrically connected to the superposition circuit module, and the superposition circuit module is electrically connected to the filter amplifier circuit module.

8. The resonant cavity differential photoacoustic spectroscopy gas detection device according to claim 6, characterized in that: The filter amplifier circuit module includes filter amplifier circuit module A, filter amplifier circuit module B, and filter amplifier circuit module C. One end of filter amplifier circuit module A, filter amplifier circuit module B, and filter amplifier circuit module C are electrically connected to the first sound transmission device (9), the second sound transmission device (10), and the third sound transmission device (11), respectively, and the other end of each is electrically connected to the microprocessor module.

9. The resonant cavity differential photoacoustic spectroscopy gas detection device according to claim 1, characterized in that: The laser emitter (1) includes a fiber laser. The output end of the fiber laser is provided with a collimator (2). The laser emitted by the fiber laser can be collimated by the collimator and then pass through the first buffer cavity (3), the first resonant cavity (5), and the second buffer cavity (8) in sequence.

10. The resonant cavity differential photoacoustic spectroscopy gas detection device according to claim 1, characterized in that: The laser emitter (1) includes a spatial laser (14), and the emitting end of the spatial laser (14) is provided with a convex lens (15). The laser emitted by the spatial laser (14) can be focused and collimated by the convex lens (15) and then pass through the first buffer cavity (3), the first resonant cavity (5), and the second buffer cavity (8) in sequence.

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