An enhanced gas sensing method and system

Abstract

The application provides an enhanced gas sensing method and system. The system comprises: a light source module for generating modulated laser; a multi-dimensional collaborative enhanced photoacoustic cell arranged on the light path of the modulated laser, the multi-dimensional collaborative enhanced photoacoustic cell comprising a central spherical cavity, an annular buffer cavity, a plurality of exponential resonant cavities connected between the central spherical cavity and the annular buffer cavity, a corolla annular multi-pass series optical enhancement module and an acoustic sensor array; and a signal processing module electrically connected with the acoustic sensor array and configured to amplify an electric signal and inversely calculate the concentration of a gas to be detected based on the amplified electric signal. The system can realize substantial improvement of photoacoustic signals through collaborative enhancement in multiple dimensions such as sound field, phase, light field and space collection, thereby greatly improving the detection sensitivity and detection accuracy of trace gases.

Description

Technical Field

[0001] This application relates to the field of gas detection technology, and in particular to an enhanced gas sensing method and system. Background Technology

[0002] Photoacoustic spectroscopy (PAS) is a highly sensitive gas detection technology based on the photoacoustic effect. When a modulated light source illuminates the gas to be detected, the gas molecules absorb light energy and undergo periodic nonradiative relaxation, generating a concentration-dependent photoacoustic signal. Detecting the amplitude allows for quantitative analysis of the target gas concentration. Due to its high sensitivity, good selectivity, and fast response speed, this technology has been widely used in environmental monitoring, industrial process control, energy security, and medical diagnostics. Detection sensitivity is a core performance indicator of a PAS sensing system. Existing technologies improve the sound field distribution by optimizing the photoacoustic cell structure and enhance the acoustic quality factor (Q value) by adjusting the resonant cavity geometry to amplify the photoacoustic signal.

[0003] However, existing solutions have several drawbacks: First, the light and sound field enhancement structures are designed independently, lacking deep spatial coupling and synergistic enhancement mechanisms; second, acoustic sensors are placed at only a single location, resulting in limited sound field information and wasted acoustic energy; and third, single-dimensional enhancement is insufficient to meet the high precision and stability requirements of trace gas detection. These shortcomings severely impact detection sensitivity and accuracy. Summary of the Invention

[0004] The enhanced gas sensing method and system provided in this application can substantially improve the photoacoustic signal through the synergistic enhancement of multiple dimensions such as sound field, phase, light field and spatial acquisition, which greatly improves the detection sensitivity and accuracy of trace gases.

[0005] The enhanced gas sensing system provided in the first aspect of this application includes: a light source module configured to generate modulated laser light; a multi-dimensional synergistic enhancement photoacoustic cell disposed in the optical path of the modulated laser light, the multi-dimensional synergistic enhancement photoacoustic cell including a central spherical cavity, an annular buffer cavity, and multiple exponential resonant cavities connected between the central spherical cavity and the annular buffer cavity, a crown-shaped annular multi-pass series optical enhancement module, and an acoustic sensor array; wherein the central spherical cavity, the annular buffer cavity, and the exponential resonant cavities are all configured to contain the gas to be detected, and the gas to be detected generates a photoacoustic signal after absorbing the modulated laser light; the annular... A buffer cavity surrounds a central spherical cavity, and multiple exponential resonant cavities are uniformly distributed circumferentially along the annular buffer cavity. The photoacoustic signals within the exponential resonant cavities are coupled and converged through the central spherical cavity. A crown-shaped annular multi-pass series optical enhancement module is positioned opposite the exponential resonant cavities. An acoustic sensor array is positioned at the in-phase antinodes of the sound pressure distribution within the central spherical cavity, the annular buffer cavity, and the exponential resonant cavities, and is configured to acquire photoacoustic signals and output corresponding electrical signals. A signal processing module, electrically connected to the acoustic sensor array, is configured to amplify the electrical signals and invert the concentration of the gas to be detected based on the amplified electrical signals.

[0006] In some feasible implementations, the exponential resonant cavity includes a first opening and a second opening arranged opposite to each other; the first opening is connected to the central spherical cavity, and the second opening is connected to the annular buffer cavity; the size of the first opening is smaller than the size of the second opening.

[0007] In some feasible implementations, the corolla-shaped annular multi-path cascaded optical enhancement module includes a first reflector and multiple reflector groups; the first reflector and multiple reflector groups are all configured corresponding to an exponential resonant cavity; wherein, after the modulated laser enters the exponential resonant cavity through the reflector groups, it passes through multiple reflector groups in sequence and then acts on the first reflector to form multiple cascaded optical paths.

[0008] In some feasible implementations, the mirror assembly includes a second mirror and a collimator arranged in a one-to-one correspondence; the second mirror is located between the collimator and the exponential resonant cavity, and the second mirror is provided with a light-transmitting hole.

[0009] In some feasible implementations, the acoustic sensor array includes two sets of acoustic sensor groups arranged opposite each other, symmetrically arranged about the central spherical cavity; wherein each set of acoustic sensor groups includes multiple acoustic sensors, the central spherical cavity includes multiple through holes, and each acoustic sensor is arranged corresponding to one through hole.

[0010] In some feasible implementations, the acoustic sensor is a lead zirconate titanate piezoelectric ceramic sensor; each group of lead zirconate titanate piezoelectric ceramic sensors is arranged in an array.

[0011] In some feasible implementations, the signal processing module includes an amplifier circuit, a lock-in amplifier, and a processor; the amplifier circuit is electrically connected to the acoustic sensor array and is configured to amplify the electrical signal, the lock-in amplifier is configured to demodulate the electrical signal, and the processor is configured to invert the concentration of the gas to be detected based on the electrical signal.

[0012] In some feasible implementations, the light source module includes a signal generator, a laser driver, and a laser; the signal generator is configured to generate a first signal, a second signal, and a third signal, the first signal and the second signal being superimposed and input to the laser driver, and the third signal being input to a lock-in amplifier.

[0013] The enhanced gas sensing system provided in the first aspect of this application achieves a substantial improvement in photoacoustic signals through the synergistic enhancement of multiple dimensions such as sound field, phase, light field and spatial acquisition, which greatly improves the detection sensitivity and accuracy of trace gases.

[0014] The enhanced gas sensing method provided in the second aspect of this application includes: S1: generating and outputting a modulated laser; S2: introducing the modulated laser into a multi-dimensional synergistic enhancement photoacoustic cell, where the gas to be detected absorbs the modulated laser and generates a photoacoustic signal; S3: a crown-shaped annular multi-path series optical enhancement module in the multi-dimensional synergistic enhancement photoacoustic cell reflects the modulated laser multiple times; S4: acquiring the converged photoacoustic signal at the in-phase antinodes of the sound pressure distribution in the central spherical cavity, the annular buffer cavity, and the exponential resonant cavity, and outputting an electrical signal accordingly; S5: amplifying the electrical signal and inverting the concentration of the gas to be detected based on the amplified electrical signal.

[0015] In some feasible implementations, S3 includes: after the first reflector reflects the modulated laser into the exponential resonant cavity, the modulated laser is reflected between multiple reflector groups, so that the modulated laser passes through each exponential resonant cavity in sequence.

[0016] The enhanced gas sensing method provided in the second aspect of this application is applied to the enhanced gas sensing system provided in the first aspect of this application, and therefore its beneficial technical effects can be found in the first aspect. Attached Figure Description

[0017] To more clearly illustrate the technical solution of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the structure of an enhanced gas sensing system provided in an embodiment of this application; Figure 2This is a schematic diagram of a multi-dimensional synergistic enhancement photoacoustic cell provided in an embodiment of this application; Figure 3 This is an enhanced gas sensing system in a specific implementation provided in the embodiments of this application; Figure 4 This is a schematic diagram of a simulated sound pressure distribution provided in an embodiment of this application; Figure 5 This is a schematic diagram of a dense light spot provided in an embodiment of this application; Figure 6A This is one of the circuit structure schematic diagrams provided in the embodiments of this application; Figure 6B This is a second schematic diagram of a circuit structure provided in an embodiment of this application; Figure 7 This is a schematic diagram comparing photoacoustic signals under different enhancement modes provided in an embodiment of this application; Figure 8 This is a schematic flowchart of an enhanced gas sensing method provided in an embodiment of this application.

[0019] Illustration markings: 10. Light source module; 101. Signal generator; 102. Laser driver; 103. DFB laser; 20. Multi-dimensional synergistic enhancement photoacoustic cell; 201. Central spherical cavity; 202. Annular buffer cavity; 203. Exponential resonant cavity; 204. Crown-shaped annular multi-pass cascaded optical enhancement module; 2041. First reflecting mirror; 2042. Reflecting mirror group; 2042a. Second reflecting mirror; 2042b. Collimator; 205. Acoustic sensor array; 30. Signal processing module; 301. Lock-in amplifier; 302. Computer; 40. Gas distribution system. Detailed Implementation

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

[0021] In the following description, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0022] Furthermore, in this application, directional terms such as "upper," "lower," "inner," and "outer" are defined relative to the indicated placement of the components in the accompanying drawings. It should be understood that these directional terms are relative concepts, used for relative description and clarification, and can change accordingly depending on the placement of the components in the accompanying drawings.

[0023] Photoacoustic spectroscopy (PAS) is a highly sensitive gas detection technology based on the photoacoustic effect. When a modulated light source illuminates the gas to be detected, the gas molecules absorb light energy and undergo a periodic nonradiative relaxation process, thereby generating a photoacoustic signal related to the gas concentration. By detecting the amplitude of this photoacoustic signal, quantitative analysis of the target gas concentration can be achieved. Due to its advantages such as high sensitivity, good selectivity, and fast response speed, photoacoustic spectroscopy has been widely used in environmental monitoring, industrial process control, energy security, and medical diagnostics.

[0024] Detection sensitivity is a core indicator for evaluating the performance of a PAS sensing system. In existing technologies, to improve the intensity of photoacoustic signals, the sound field distribution characteristics are usually improved by optimizing the structure of the photoacoustic cell. This is mainly achieved by adjusting the geometric parameters of the exponential resonator to improve the acoustic quality factor (Q value), thereby amplifying the photoacoustic signal.

[0025] However, the aforementioned existing technical solutions still have the following defects and shortcomings in practical applications: First, most existing photoacoustic enhancement schemes are limited to independent optimization in a single dimension. The light field enhancement structure and the sound field enhancement structure are usually designed independently, and there is a lack of deep spatial coupling and synergistic enhancement mechanism between the two.

[0026] Secondly, traditional photoacoustic cells typically place acoustic sensors at only a single detection location, resulting in very limited sound field information being captured. This fails to effectively explore and utilize the potential spatial sound field distribution characteristics inside the cavity, leading to a waste of some acoustic energy.

[0027] Third, as the sensitivity requirements for trace and ultra-trace gas detection continue to increase, relying solely on single-dimensional enhancement mechanisms is no longer sufficient to meet the practical application demands for high precision and high stability. These solutions suffer from technical problems of low detection sensitivity and low detection accuracy.

[0028] To address the aforementioned technical problems, this application provides an enhanced gas sensing system to resolve the limitations in photoacoustic signal intensity, the reliance on a single enhancement mechanism, and the inability of single-point acoustic detection to fully utilize the acoustic field distribution characteristics within the cavity—all issues affecting detection sensitivity and accuracy—in existing photoacoustic spectral sensing systems. This application achieves efficient amplification of the photoacoustic signal and high-sensitivity, high-precision gas detection through the synergistic effect of multiple mechanisms, including multi-cavity acoustic coupling enhancement, optical field enhancement, and spatial array acquisition enhancement.

[0029] To better understand how this application enables an enhanced gas sensing system, the basic principles are explained below.

[0030] This application employs modulated laser to excite the gas to be detected to generate a photoacoustic effect. The multi-dimensional synergistic enhancement photoacoustic cell can be a Herriott multi-pass cell structure, which reflects the incident laser multiple times. Multiple piezoelectric sensing units are used to form an array to synchronously acquire and coherently superimpose the photoacoustic signals, thereby improving the system's detection sensitivity and signal-to-noise ratio.

[0031] According to Beer-Lambert's law, the transmission intensity of laser light in a gas satisfies: ; Where I0 is the incident light intensity, and I is the transmitted light intensity. denoted as the target gas absorption coefficient, C as the target gas concentration, and L as the optical path length.

[0032] As shown in the above equation, the optical path length L is an important parameter affecting the gas absorption capacity. When the optical path length L increases, the laser energy absorbed by the gas increases accordingly, thereby generating a stronger photoacoustic signal.

[0033] For weak absorption conditions: ; Expanding the exponential function and ignoring higher-order terms, we get: ; Therefore, the light power P absorbed by the gas abs for: ; Further results were obtained: ; The above formula shows that the gas absorption power has a linear relationship with the optical path length.

[0034] For a Herriott multipath cell, if the laser undergoes m effective propagations between the two mirrors, and the distance of each propagation is d, then the effective absorption optical path length L is... eff for: ; Therefore, it can be seen that increasing the number of reflections can significantly increase the effective optical path length, thereby improving laser absorption efficiency.

[0035] When a modulated laser irradiates a gas to be detected, the absorbed light energy is converted into heat energy through non-radiative relaxation, causing the gas medium to expand and compress periodically, ultimately forming photoacoustic waves.

[0036] The modulated laser power P(t) can be expressed as: ; Where P0 is the average laser power, w is the modulation angular frequency, and t is time.

[0037] Because the gas absorption process is periodic, the resulting photoacoustic pressure also has the same frequency characteristics, and its sound pressure amplitude p0 can be expressed as: ; Where k1 is the photothermal conversion coefficient, This represents the sound pressure amplitude in the non-resonant state.

[0038] When the laser modulation frequency f m With the natural frequency f of the photoacoustic cell r When consistent, that is ; The system enters a resonant state, and the sound pressure level increases significantly.

[0039] Traditional photoacoustic systems typically use a single acoustic sensor for sound signal detection, which limits the amount of sound field information that can be acquired, and the detection sensitivity is limited by the performance of the individual sensor. To further improve the system's ability to detect weak photoacoustic signals, this application employs an array structure composed of multiple piezoelectric sensors and arranges them in the region of the photoacoustic cell where the sound pressure is relatively strong.

[0040] In one embodiment of this application, the ideal photoacoustic signal amplitude received by a single acoustic sensor Follow the following relationship: ; In the formula, The inherent sensitivity of a single acoustic sensor; The equivalent excitation power can be obtained by calculating the excitation power and effective optical path along the integrated optical path; The photoacoustic cell constant under the condition of a single acoustic sensor; The concentration of the target gas to be measured; For the target gas at a specific wavenumber The absorption coefficient at that point. As can be seen from the above equation, the amplitude of the photoacoustic signal can be increased by using a multi-acoustic sensor array. In addition, by designing a Herriott multi-pass cell to increase the effective absorption optical path, the equivalent excitation optical power can be effectively increased, thereby enhancing the photoacoustic signal intensity.

[0041] To improve the detection sensitivity of the system, this application adopts an array structure containing N identical acoustic sensors, preferably N=8. To maximize signal extraction, all N acoustic sensors are arranged at the in-phase antinodes of the sound pressure distribution within the multi-dimensional synergistic enhancement photoacoustic cell.

[0042] Since all acoustic sensors are at the same acoustic phase point, their output photoacoustic signals are completely coherent. By using an equivalent summing circuit at the back end to superimpose the output electrical signals of the N acoustic sensors in phase, the total photoacoustic signal amplitude obtained by the system in this application is... for: ; Therefore, it can be seen that through array design, the effective signal amplitude of the system increases linearly with the number of acoustic sensors N.

[0043] Unlike the coherent characteristics of photoacoustic signals, the main noise in photoacoustic detection systems is usually characterized by independent and random incoherent noise.

[0044] Let the root mean square (RMS) voltage of the output noise of a single acoustic sensor be... According to the statistical superposition principle of independent random variables, when multiple independent noise channels are superimposed, their total variance is equal to the sum of the variances of each channel. Therefore, the total noise root-mean-square voltage of the N-channel acoustic sensor array used in this application... for: ; This indicates that the background noise amplitude of the system only increases with the number of acoustic sensors. increase.

[0045] Considering the superposition characteristics of signal and noise mentioned above, under ideal conditions, the theoretical signal-to-noise ratio of the array system is ( Compared to single acoustic sensor systems ( The enhancement factor should be: ; However, in practical implementation, the openings added to the photoacoustic cell wall to accommodate N acoustic sensors inevitably introduce additional acoustic leakage and heat conduction losses, leading to a decrease in the quality factor (Q value) of the photoacoustic exponential resonator. In this state, the actual photoacoustic cell constant of the system is... Reduce to .

[0046] Therefore, this application fully considers the physical losses of the system and derives the corrected actual array signal-to-noise ratio (SNR). The formula is: ; By optimizing the array arrangement of acoustic sensors, the aperture size, and the exponential resonant cavity structure design, the acoustic loss introduced by the aperture is strictly controlled to ensure the correction factor. This results in a substantial improvement in the overall signal-to-noise ratio and minimum detection limit (MDL) of the system in practical engineering applications.

[0047] Figure 1 This is a schematic diagram of an enhanced gas sensing system provided in an embodiment of this application.

[0048] See Figure 1 As shown in the embodiment of this application, an enhanced gas sensing system includes: a light source module 10, a multi-dimensional collaborative enhanced photoacoustic cell 20, and a signal processing module 30.

[0049] The light source module 10 is configured to generate modulated laser light.

[0050] Specifically, the light source module 10 is used to generate a modulated laser of a specific wavelength.

[0051] In one example, the light source module 10 includes a distributed feedback semiconductor laser with a center wavelength of 1531.58 nm, corresponding to the absorption spectral line of C2H2, and a corresponding operating temperature and driving current of 19 °C and 65 mA, respectively.

[0052] Figure 2 This is a schematic diagram of a multi-dimensional synergistic enhancement photoacoustic cell provided in an embodiment of this application.

[0053] Combination Figure 1 and Figure 2 As shown, a multi-dimensional synergistic enhancement photoacoustic cell 20 is disposed in the optical path of the modulated laser. The multi-dimensional synergistic enhancement photoacoustic cell 20 is configured to contain the gas to be detected, which generates a photoacoustic signal after absorbing the modulated laser. The multi-dimensional synergistic enhancement photoacoustic cell 20 includes a shell structure, a central spherical cavity 201, an annular buffer cavity 202, multiple exponential resonant cavities 203 connected between the central spherical cavity 201 and the annular buffer cavity 202, a crown-shaped annular multi-pass series optical enhancement module 204, and an acoustic sensor array 205. The annular buffer cavity 202 surrounds the outside of the central spherical cavity 201. The central spherical cavity 201, the annular buffer cavity 202, and the exponential resonant cavities 203 are formed on the shell structure, and the acoustic sensor array 205 is disposed within a mounting slot in the shell structure.

[0054] Specifically, the central spherical cavity 201, the annular buffer cavity 202, and the exponential resonant cavity 203 are all configured to contain the gas to be detected, which generates a photoacoustic signal after absorbing the modulated laser. The annular buffer cavity 202 is arranged around the central spherical cavity 201, and multiple exponential resonant cavities 203 are uniformly distributed along the circumference of the annular buffer cavity 202. The photoacoustic signal in the exponential resonant cavity 203 is coupled and converged through the central spherical cavity, thereby forming an enhanced sound field. The crown-shaped annular multi-pass series optical enhancement module 204 is arranged opposite to the exponential resonant cavity 203. The crown-shaped annular multi-pass series optical enhancement module 204 is configured to improve the light absorption efficiency and photoacoustic excitation intensity of the gas to be detected to the modulated laser. The acoustic sensor array 205 is located at the in-phase antinodes of the sound pressure distribution in the central spherical cavity 201, the annular buffer cavity 202, and the exponential resonant cavity 203, and is configured to collect the photoacoustic signal and output the corresponding electrical signal.

[0055] Along the central spherical cavity 201, multiple exponential resonant cavities 203 are symmetrically distributed about the central axis of the central spherical cavity 201 and at equal intervals. In this way, the in-phase sound waves generated by the multiple exponential resonant cavities 203 will form acoustic superposition within the central spherical cavity 201, achieving acoustic resonance enhancement. At the same time, the annular buffer cavity 202 can effectively isolate external environmental acoustic noise, reduce background noise interference, and further improve the signal-to-noise ratio of the photoacoustic signal.

[0056] The crown-shaped multi-path series optical enhancement module 204 includes a first reflector 2041 and multiple reflector groups 2042; the first reflector 2041 and multiple reflector groups 2042 are each corresponding to an exponential resonant cavity 203; after the modulated laser enters the exponential resonant cavity 203 through the reflector group 2042, it passes through multiple reflector groups 2042 in sequence and then acts on the first reflector 2041, forming multiple series optical paths.

[0057] Specifically, the first reflector 2041 serves as the terminating reflector, and its quantity is always one. The number of reflector groups 2042 is adjusted according to the number of exponential resonant cavities 203.

[0058] By setting up the crown-shaped annular multi-path series optical enhancement module 204, the optical path of the modulated laser within the multi-dimensional synergistic enhancement photoacoustic cell 20 can be extended. Through the series optical path, the modulated laser can be reflected multiple times, increasing its effective propagation distance in the gas to be detected, thereby improving light absorption efficiency and photoacoustic excitation intensity. The acoustic sensor array 205 is positioned at the in-phase antinodes of the sound pressure distribution within the central spherical cavity 201, the annular buffer cavity 202, and the exponential resonant cavity 203. It is configured to acquire photoacoustic signals and correspondingly output electrical signals. The acoustic sensor array 205 may include multiple lead zirconate titanate piezoelectric sensors, which are arranged in an array around the central spherical cavity 201 to synchronously acquire photoacoustic signals at different spatial locations.

[0059] See also Figure 2 As shown, the acoustic sensor array 205 consists of two sets, one above the other, and each set includes a 2×2 array of acoustic sensors.

[0060] Figure 3 This is an enhanced gas sensing system in a specific implementation provided in the embodiments of this application.

[0061] See Figure 3 As shown, the acoustic sensor array 205 includes two sets of acoustic sensor groups arranged opposite to each other, and the two sets of acoustic sensor groups are symmetrically arranged about the central spherical cavity 201; wherein, each set of acoustic sensor groups includes multiple acoustic sensors, the central spherical cavity 201 includes multiple through holes, and each acoustic sensor is arranged corresponding to one through hole and maintaining a preset distance.

[0062] In this way, multiple acoustic sensors in the acoustic sensor array 205 simultaneously collect photoacoustic signals from each exponential resonant cavity 203, and then transmit the collected multi-channel photoacoustic signals to the signal processing module 30 for coherent superposition and fusion, thereby achieving secondary amplification of the signals.

[0063] By coordinating the central spherical cavity 201, the annular buffer cavity 202, the exponential resonant cavity 203, the acoustic sensor array 205, and the crown-shaped annular multi-pass series optical enhancement module 204, multi-cavity enhancement, multi-pass optical enhancement, and multi-acoustic sensor enhancement can be achieved to realize multi-dimensional synergistic enhancement.

[0064] Figure 4 This is a schematic diagram of a simulated sound pressure distribution provided in an embodiment of this application.

[0065] See Figure 4 As shown, in order to determine the optimal operating mode of the multi-dimensional synergistic enhancement photoacoustic cell 20 and the optimal position of the acoustic sensor, the embodiments of this application used COMSOL Multiphysics to perform finite element simulation on it. The maximum sound pressure occurs in the spherical cavity part, so the acoustic sensor array 205 is placed in the central spherical cavity 201 part of the multi-dimensional synergistic enhancement photoacoustic cell 20.

[0066] The signal processing module 30 is electrically connected to the acoustic sensor array 205 and is configured to amplify the electrical signal to enhance the electrical signal, and to invert the concentration of the gas to be detected based on the amplified and enhanced electrical signal.

[0067] The enhanced gas sensing system provided in this application embodiment achieves multiple amplification of photoacoustic signals through the synergistic effect of optical multi-path enhancement, acoustic resonance enhancement, and acoustic sensor array coherence enhancement. At the same time, it suppresses external noise through the annular buffer cavity 202, thereby improving the system's detection sensitivity from both signal enhancement and noise suppression aspects. It can effectively solve the problems of short optical path and low signal amplitude in traditional photoacoustic gas sensing, and is suitable for high-sensitivity detection of various gases such as low-concentration acetylene.

[0068] In the actual testing process, the gas to be tested is first introduced into the central spherical cavity 201 and each exponential resonant cavity 203 of the multi-dimensional synergistic enhancement photoacoustic cell 20. After the gas stabilizes, the light source module 10 is activated to output a modulated laser corresponding to the absorption spectrum of the gas to be tested. After the modulated laser enters the crown-shaped multi-path series optical enhancement module 204, it is reflected multiple times between multiple mirror groups 2042 in the corresponding exponential resonant cavity 203, which prolongs the optical path in the gas to be tested, increases the total energy absorbed by the gas, and enhances the excitation intensity of the photoacoustic signal. After absorbing the modulated laser energy, the gas to be tested undergoes periodic thermal expansion, which in turn excites light in each exponential resonant cavity 203. The photoacoustic signals from each exponential resonant cavity 203 propagate to the central spherical cavity 201. Due to their in-phase nature, they undergo acoustic superposition, resulting in resonant amplification of the photoacoustic signals. Subsequently, acoustic sensor arrays 205, positioned at in-phase antinodes of the sound pressure distribution within the central spherical cavity 201, the annular buffer cavity 202, and the exponential resonant cavity 203, synchronously acquire the photoacoustic signals at each location. These signals are then converted into electrical signals and transmitted to the signal processing module 30. The signal processing module 30 coherently superimposes the multiple electrical signals to further amplify the photoacoustic signals. Finally, based on the amplitude of the amplified electrical signals and a preset concentration calibration curve, the actual concentration of the gas to be detected is calculated.

[0069] In some feasible implementations, the exponential resonant cavity 203 includes a first opening and a second opening disposed opposite to each other; the first opening is connected to the central spherical cavity 201, and the second opening is connected to the annular buffer cavity 202; the size of the first opening is smaller than the size of the second opening.

[0070] Specifically, the exponential resonant cavity 203 is generated by rotating an exponential function about the axis, and its geometric profile is described by the following parametric equations: .

[0071] In this system, a coordinate system is established with the center of the exponential resonant cavity 203 as the reference point. z represents the axial coordinate of the exponential resonant cavity 203, and r(z) represents the cross-sectional radius corresponding to the axial position z. R2 is the first opening radius, R1 is the second opening radius, and L is the axial length of the exponential resonant cavity 203.

[0072] In this way, when the sound wave oscillates in the exponential resonant cavity 203, the larger size of the second opening can reduce the reflection of the sound wave at the second opening, avoid the clutter reflected back into the exponential resonant cavity 203 from interfering with the original sound wave oscillation, and ensure the resonance amplification effect. At the same time, the first opening connects to the central spherical cavity 201 and is smaller in size, which can not only allow the resonated sound wave to be smoothly transmitted into the central spherical cavity 201 to achieve in-phase superposition, but also reduce the interference caused by the sound wave in the central spherical cavity 201 being transmitted back into the exponential resonant cavity 203, further improving the overall signal-to-noise ratio.

[0073] In one specific implementation, the mirror assembly 2042 includes a second mirror 2042a and a collimator 2042b arranged in a one-to-one correspondence; the second mirror 2042a is located between the collimator 2042b and the exponential resonant cavity 203. The collimator 2042b is an optical fiber collimator, and the second mirror 2042a has a light-transmitting aperture.

[0074] Specifically, the first reflector 2041 serves as the termination device within one conduction cycle of the modulated laser, and a group of reflectors 2042 adjacent to the first reflector 2041 serves as the starting device within one conduction cycle of the modulated laser. In the remaining groups of reflectors 2042, the collimators 2042b at adjacent positions are connected in pairs.

[0075] See also Figure 2 As shown, the modulated laser enters the exponential resonant cavity 203 through the second mirror 2042a in the mirror group 2042 adjacent to the first mirror 2041. Positions A to E represent different locations. For example, the second mirror 2042a at position A introduces the collimated modulated laser into the exponential resonant cavity 203, incident along the axial direction of the cavity, and propagates to the second mirror 2042a at position B. Through the light-transmitting hole on the second mirror 2042a, the modulated laser is introduced from the collimator 2042b at position B to the collimator 2042b at position C. Then, through the light-transmitting hole on the second mirror 2042a at position C, the modulated laser is introduced into the mirror group 2042 at position D. Subsequently, via the mirror group 2042 at position E, the modulated laser is finally introduced into the first mirror 2041. Since the first mirror 2041 does not have a light-transmitting hole, the modulated laser operation ends within one conduction cycle. In this way, the modulated laser generated by the light source module 10 propagates through multiple exponential resonant cavities 203 in sequence. After passing through the previous exponential resonant cavity 203, the modulated laser is received by the collimator 2042b. The two collimators 2042b are connected and then injected into the next adjacent exponential resonant cavity 203, so that multiple exponential resonant cavities 203 share the same modulated laser source and maintain a consistent modulation phase.

[0076] For examples, see below. Figure 2As shown, in this example, there are 6 exponential resonant cavities 203 and 1 first reflector 2041. In other implementations, the number of exponential resonant cavities 203 can be different.

[0077] In one specific implementation, the number of reflections on the first reflector 2041 and the second reflector 2042a is twice the number of their light spots.

[0078] Figure 5 This is a schematic diagram of a dense light spot provided in an embodiment of this application.

[0079] See Figure 5 As shown, the dense light spot is a corolla-shaped ring light spot, with a total of 250 spots formed on each mirror, undergoing 500 reflections.

[0080] In one specific implementation, the signal processing module 30 includes an amplifier circuit, a lock-in amplifier 301, and a processor; the amplifier circuit is electrically connected to the acoustic sensor array 205, the amplifier circuit is configured to amplify the electrical signal, the lock-in amplifier 301 is configured to demodulate the electrical signal, and the processor is configured to invert the concentration of the gas to be detected based on the electrical signal.

[0081] Specifically, the signal processing module 30 is used to synchronously process, coherently superimpose, and extract features from signals acquired by multiple acoustic sensors to obtain target gas concentration information. The raw electrical signals acquired by the acoustic sensor array 205 typically have small amplitudes and are subject to environmental noise interference. The amplification circuit first boosts the amplitude of the raw electrical signals, filters out some low-frequency baseline noise, and retains the response signal synchronized with the gas absorption modulation frequency. The lock-in amplifier 301 extracts only the signal that is in phase and frequency with the modulated laser, further suppressing irrelevant background noise and improving the signal-to-noise ratio. After receiving the demodulated signal, the processor, combined with the pre-calibrated correspondence between the photoacoustic response and gas concentration, directly inverts to obtain the actual concentration of the gas to be detected. The processor can be a computer 302.

[0082] In one specific implementation, the light source module 10 may include a signal generator 101, a laser driver 102, and a laser connected in sequence. The laser may be a DFB laser 103.

[0083] The signal generator 101 is configured to generate a first signal, a second signal, and a third signal. The first signal and the second signal are superimposed and input to the laser driver 102, and the third signal is input to the lock-in amplifier 301.

[0084] Specifically, the first, second, and third signals can be a sinusoidal modulation signal, a sawtooth scanning signal, and a square wave signal, respectively. The sinusoidal and sawtooth signals are superimposed by an adder circuit to jointly drive the DFB laser 103, achieving wavelength modulation and spectral scanning. The square wave signal is used as a reference signal for the lock-in amplifier 301.

[0085] The acquired weak electrical signals first pass through a two-stage preamplifier circuit: a fixed 11x amplification at the first stage and a variable amplification from 1x to 101x at the second stage, to sum and amplify the signals from different acoustic sensors. The signals are then input to a lock-in amplifier 301 for demodulation. The demodulated signal can be displayed in real time and saved to a computer 302 for subsequent data analysis and processing. Furthermore, the enhanced gas sensing system also includes a gas mixing system 40, which prepares sample gases of different concentrations by dynamically diluting standard gases for system performance testing and calibration experiments.

[0086] Figure 6A This is one of the circuit structure schematic diagrams provided in the embodiments of this application; wherein, Figure 6A Figure (a) shows a schematic diagram of an input circuit. Figure 6A Figure (b) shows a schematic diagram of a voltage regulator circuit. Figure 6A Figure (c) shows a schematic diagram of an amplifier circuit. Figure 6B This is a second schematic diagram of a circuit structure provided in an embodiment of this application. Figure 6B Figure (a) shows a schematic diagram of an adder circuit. Figure 6B Figure (b) shows a schematic diagram of a power supply circuit.

[0087] Combination Figure 6A (a) to (c) Figure 6B In (a) and (b), the external power supply is connected to the circuit through the terminals of the power supply circuit, and then regulated by the voltage regulator circuit. The voltage regulator circuit outputs a +2V voltage, which is used as the input circuit to power the acoustic sensor; at the same time, it outputs a +9V voltage to power the amplifier circuit. The acoustic sensor is connected to the circuit through terminals A1-A8 in the input circuit, and then the input signals are added by the adder circuit. The added signal is amplified by the amplifier circuit and finally output to the lock-in amplifier 301.

[0088] In the input circuit, R is a resistor, C is a capacitor, +2 is the supply voltage, GND is ground, and A1-A10 are terminals. In the voltage regulator circuit, TPS7A49 is a linear regulator; in the amplifier circuit, OPA2197 is a precision operational amplifier, and +9 and -9 are the supply voltages. In the adder circuit, AD825ARZ-REEL7 is an instrumentation amplifier.

[0089] Figure 7This is a schematic diagram comparing photoacoustic signals under different enhancement modes provided in an embodiment of this application.

[0090] See Figure 7 As shown, the signal enhancement of multiple exponential resonant cavities 203 is approximately 2.59 times greater than that of a single exponential resonant cavity 203. The multi-pass cell enhances the photoacoustic signal by approximately 92.31 times compared to the multi-pass cell. Finally, the acoustic sensor array enhances the signal by 7.68 times compared to the multi-pass cell. In summary, the enhanced gas sensing system of this application enhances the photoacoustic signal by approximately 1836.16 times, significantly reducing the detection limit of the system.

[0091] The enhanced gas sensing system provided in this application utilizes a coupling structure formed by multiple exponential resonant cavities 203 and a central spherical cavity 201 to achieve the convergence and superposition of photoacoustic signals from each exponential resonant cavity 203, thereby increasing the sound pressure amplitude in the central detection area. A single-beam series excitation method is used instead of the traditional beam-splitting parallel excitation method to avoid excitation phase differences caused by different optical paths, improving the coherent excitation effect between the multiple exponential resonant cavities 203. A crown-shaped multi-path series optical enhancement module 204 increases the effective absorption optical path between the laser and the gas to be detected, significantly improving the excitation intensity of the photoacoustic source. An acoustic sensor array enables omnidirectional acquisition of spatial sound field information, improving the ability to acquire effective signals and the overall signal-to-noise ratio of the system. Through the synergistic enhancement of multiple dimensions such as sound field, phase, optical field, and spatial acquisition, a substantial improvement in photoacoustic signals is achieved, greatly enhancing the detection sensitivity and accuracy of trace gases. Corresponding to the aforementioned embodiment of the synergistic enhancement gas sensing system, this application also provides an embodiment of an enhanced gas sensing method, applied in the enhanced gas sensing system.

[0092] Figure 8 This is a schematic flowchart of the enhanced gas sensing method provided in the embodiments of this application.

[0093] See Figure 8 As shown in the embodiments of this application, the enhanced gas sensing method includes: S1: Generates and outputs modulated laser light.

[0094] In this step, the light source module generates modulated laser light.

[0095] S2: The modulated laser is introduced into the multi-dimensional synergistic enhancement photoacoustic cell, and the gas to be detected absorbs the modulated laser to generate a photoacoustic signal.

[0096] S3: The corolla-shaped multi-path cascaded optical enhancement module in the multi-dimensional synergistic enhancement photoacoustic cell reflects the modulated laser multiple times to improve the light absorption efficiency and photoacoustic excitation intensity of the gas to be detected to the modulated laser.

[0097] S4: At the in-phase antinodes of the sound pressure distribution in the central spherical cavity, annular buffer cavity, and exponential resonant cavity, the converged photoacoustic signal is collected and converted into an electrical signal.

[0098] In steps S2-S4, the multi-dimensional synergistic enhancement photoacoustic cell uses a coupling structure between multiple exponential resonant cavities and the central spherical cavity to converge and superimpose the photoacoustic signals generated by each exponential resonant cavity into the central spherical cavity, thereby increasing the sound pressure amplitude in the central detection area. At the same time, a single-beam series excitation method is used to eliminate the optical path phase difference caused by traditional beam splitting parallel excitation, ensuring the coherent excitation effect of multiple exponential resonant cavities. The acoustic sensor array is set at the in-phase antinodes of the sound pressure distribution in the central spherical cavity, the annular buffer cavity, and the exponential resonant cavity, and after completing signal acquisition, it is converted into an electrical signal that can be processed later.

[0099] S5: Amplify the electrical signal and invert the concentration of the gas to be detected based on the amplified electrical signal.

[0100] In this step, the effective signal component with the same frequency as the modulation frequency is extracted from the amplified electrical signal using lock-in amplification technology, and the interference of environmental noise and circuit background noise is filtered out. Then, the inversion calculation of the concentration of the gas to be detected is completed by using the pre-calibrated correspondence between the signal amplitude and the gas concentration, and finally the accurate gas concentration detection result is obtained.

[0101] In some feasible implementations, S3 includes: after the first mirror reflects the modulated laser to the exponential resonant cavity, the modulated laser is reflected between multiple mirror groups, so that the modulated laser passes through each exponential resonant cavity in sequence, thereby improving the light absorption efficiency and photoacoustic excitation intensity of the gas to be detected to the modulated laser.

[0102] In this step, the modulated laser passes sequentially through each exponential resonant cavity containing the gas to be detected, exciting the gas molecules in each exponential resonant cavity to generate photoacoustic signals. This retains the signal enhancement advantages of the multi-exponential resonant cavity structure, while avoiding the optical path loss and phase asynchrony problems caused by traditional beam splitting schemes through single-beam series connection, thus ensuring the coherent superposition effect of the photoacoustic signals of each exponential resonant cavity in the central spherical cavity.

[0103] It should be noted that, upon considering the specification and practicing the application disclosed herein, those skilled in the art will readily conceive of other embodiments of this application. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein.

[0104] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The true scope is indicated by this application.

Claims

1. An enhanced gas sensing system, characterized in that, include: The light source module is configured to generate modulated laser light; A multi-dimensional synergistic enhancement photoacoustic cell is disposed in the optical path of the modulated laser. The multi-dimensional synergistic enhancement photoacoustic cell includes a central spherical cavity, an annular buffer cavity, and multiple exponential resonant cavities connected between the central spherical cavity and the annular buffer cavity, a crown-shaped annular multi-pass series optical enhancement module, and an acoustic sensor array. The central spherical cavity, the annular buffer cavity, and the exponential resonant cavity are all configured to contain the gas to be detected, which absorbs the modulated laser to generate a photoacoustic signal. The annular buffer cavity surrounds the central spherical cavity, and multiple exponential resonant cavities are uniformly distributed along the circumference of the annular buffer cavity. The photoacoustic signal in the exponential resonant cavity is coupled and converged through the central spherical cavity. The crown-shaped annular multi-pass series optical enhancement module is disposed opposite to the exponential resonant cavity. The acoustic sensor array is disposed at the in-phase antinodes of the sound pressure distribution in the central spherical cavity, the annular buffer cavity, and the exponential resonant cavity, and is configured to acquire the photoacoustic signal and output a corresponding electrical signal. The signal processing module, electrically connected to the acoustic sensor array, is configured to amplify the electrical signal and invert the concentration of the gas to be detected based on the amplified electrical signal.

2. The enhanced gas sensing system according to claim 1, characterized in that, The exponential resonant cavity includes a first opening and a second opening that are disposed opposite to each other; The first opening communicates with the central spherical cavity, and the second opening communicates with the annular buffer cavity; the size of the first opening is smaller than the size of the second opening.

3. The enhanced gas sensing system according to claim 2, characterized in that, The corolla-shaped multi-pass series optical enhancement module includes a first mirror and multiple mirror groups; the first mirror and multiple mirror groups are each configured to correspond to one of the exponential resonant cavities. The modulated laser enters the exponential resonant cavity through the mirror group, and then acts on the first mirror after passing through multiple mirror groups in sequence to form multiple series optical paths.

4. The enhanced gas sensing system according to claim 3, characterized in that, The mirror assembly includes a second mirror and a collimator arranged in a one-to-one correspondence; The second reflector is located between the collimator and the exponential resonant cavity, and the second reflector is provided with a light-transmitting hole.

5. The enhanced gas sensing system according to claim 1, characterized in that, The acoustic sensor array includes two sets of acoustic sensor groups arranged opposite each other, and the two sets of acoustic sensor groups are symmetrically arranged about the central spherical cavity; Each acoustic sensor group includes multiple acoustic sensors, and the central spherical cavity includes multiple through holes, with each acoustic sensor corresponding to one of the through holes.

6. The enhanced gas sensing system according to claim 5, characterized in that, The acoustic sensor is a lead zirconate titanate piezoelectric ceramic sensor. Each group of lead zirconate titanate piezoelectric ceramic sensors is arranged in an array.

7. The enhanced gas sensing system according to claim 1, characterized in that, The signal processing module includes an amplifier circuit, a lock-in amplifier, and a processor; The amplification circuit is electrically connected to the acoustic sensor array, the amplification circuit is configured to amplify the electrical signal, the lock-in amplifier is configured to demodulate the electrical signal, and the processor is configured to invert the concentration of the gas to be detected based on the electrical signal.

8. The enhanced gas sensing system according to claim 7, characterized in that, The light source module includes a signal generator, a laser driver, and a laser; The signal generator is configured to generate a first signal, a second signal, and a third signal. The first signal and the second signal are superimposed and input to the laser driver, and the third signal is input to the lock-in amplifier.

9. An enhanced gas sensing method, characterized in that, The method, applied to the enhanced gas sensing system according to any one of claims 1 to 8, comprises: S1: Generates and outputs modulated laser; S2: The modulated laser is introduced into a multi-dimensional synergistic enhancement photoacoustic cell, and the gas to be detected absorbs the modulated laser to generate a photoacoustic signal; S3: The corolla-shaped multi-path cascaded optical enhancement module in the multi-dimensional synergistic enhancement photoacoustic cell reflects the modulated laser multiple times; S4: At the in-phase antinodes of the sound pressure distribution in the central spherical cavity, the annular buffer cavity, and the exponential resonant cavity, the converged photoacoustic signal is collected and the corresponding electrical signal is output. S5: Amplify the electrical signal and invert the concentration of the gas to be detected based on the amplified electrical signal.

10. The enhanced gas sensing method according to claim 9, characterized in that, S3 includes: after the first reflector reflects the modulated laser to the exponential resonant cavity, the modulated laser is reflected between multiple reflector groups, so that the modulated laser passes through each of the exponential resonant cavities in sequence.

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