A multi-component gas photoacoustic spectroscopy detection device and method based on dual-sided opposing lasers

Abstract

This invention relates to the field of photoacoustic detection technology, providing a photoacoustic spectral detection device and method for multi-component gases based on dual-sided opposing lasers. The invention configures independent excitation and sensing channels for each analyte gas, employs a dual-sided opposing, parallel laser incident method, and is paired with corresponding acoustic sensors to initially separate multiple signals in physical space. A transfer matrix accurately characterizing the acoustic-electric coupling relationship of the system is pre-obtained through calibration experiments. During real-time measurement, this matrix is ​​used to perform mathematical decoupling operations on the mixed signals synchronously acquired by multiple sensors, and the independent concentration information corresponding to each analyte gas is solved in reverse. This invention achieves truly synchronous and high-precision measurement of multiple gas concentrations, effectively overcoming the signal interference bottleneck in traditional single-sensor multiplexing technology. Simultaneously, the device has a clear structure, strong universality, and significantly improves the detection reliability in dynamic gas environments.

Description

Technical Field

[0001] This invention relates to the field of photoacoustic detection technology, and more specifically, to a multi-component gas photoacoustic spectroscopy detection device and method based on dual-sided opposing lasers. Background Technology

[0002] Photoacoustic spectroscopy is a highly sensitive and selective gas detection technology based on the photoacoustic effect. Its principle is as follows: when a modulated laser of a specific wavelength is absorbed by the molecules of the gas to be measured, the gas molecules convert light energy into heat energy through non-radiative relaxation, generating periodic pressure waves (i.e., photoacoustic signals); this signal is detected by a highly sensitive acoustic sensor, and its amplitude is proportional to the gas concentration.

[0003] Currently, common photoacoustic spectroscopy schemes for multi-component gas detection have the following limitations: (1) Multi-cell scheme: Each gas requires an independent system, resulting in large size, high cost, and complex calibration; (2) Single-cell sequential measurement (time-division multiplexing): Different components are detected sequentially by scanning laser wavelengths, which cannot achieve true synchronization and introduces time asynchrony errors in dynamic gas environments; (3) Single-cell frequency-division multiplexing: Different gases are excited using different modulation frequencies, but only a single sensor is used to receive the mixed sound field of all frequencies. Since the sound waves generated by different gases will be linearly superimposed and interfered in the cavity, and the gas absorption spectrum may have cross-interference, directly analyzing the concentration of each component from a single mixed signal will face serious signal crosstalk problems, which greatly limits the detection accuracy and reliability.

[0004] Therefore, existing technologies struggle to achieve high-precision, high-synchronization, and strong anti-interference detection of multiple gas components while maintaining a relatively compact structure. This has become a technological bottleneck for dynamic application scenarios such as industrial process monitoring, online environmental monitoring, and safety early warning. Summary of the Invention

[0005] This invention addresses the technical problems existing in the prior art by providing a multi-component gas photoacoustic spectroscopy detection device and method based on dual-sided opposing lasers. By configuring an independent and spatially isolated photoacoustic resonant cavity and laser-sensor channel for each gas to be measured in the same device, the problem of signal crosstalk in multi-component gas photoacoustic spectroscopy detection is solved, thereby realizing high-precision and truly synchronous measurement of multiple gases.

[0006] According to a first aspect of the present invention, a multi-component gas photoacoustic spectroscopy detection device based on dual-sided opposing lasers is provided, comprising: The photoacoustic cell contains independent photoacoustic resonant cavities corresponding to the number of laser emitting units. At least two laser emitting units are used to emit at least two lasers with different wavelengths and modulation frequencies. The at least two lasers are incident on at least two photoacoustic resonant cavities in a one-to-one correspondence, and the lasers do not interfere with each other in space. At least two acoustic sensors are configured one-to-one with at least two of the photoacoustic resonant cavities to detect photoacoustic signals within the corresponding photoacoustic resonant cavities; The signal processing unit is electrically connected to each of the acoustic sensors and is used to extract the concentration of each gas component from the photoacoustic signal.

[0007] Based on the above technical solution, the present invention can also be improved as follows.

[0008] Optionally, the photoacoustic cell includes a first buffer chamber, at least two photoacoustic resonant cavities arranged in parallel, and a second buffer chamber connected sequentially along the gas flow direction; At least two of the laser emitting units are respectively disposed on the first buffer chamber and the second buffer chamber.

[0009] Optionally, the signal processing unit includes a decoupling calculation module, which is configured to: Based on the pre-stored system transfer matrix, the photoacoustic signal is decoupled to separate the independent signal values ​​corresponding to each gas component.

[0010] According to a second aspect of the present invention, based on the aforementioned multi-component gas photoacoustic spectroscopy detection device based on dual-sided opposing lasers, a multi-component gas photoacoustic spectroscopy detection method is provided, comprising: S1, acquire the pre-calibrated system transfer characteristics from each gas excitation source to each acoustic sensor; S2, a mixed gas containing at least two test gases flows through the photoacoustic cell, and each laser emitting unit is controlled to work synchronously, so that each laser beam is incident on the corresponding photoacoustic resonant cavity, and photoacoustic signals are collected synchronously through each acoustic sensor; S3. Based on the transmission characteristics of the system, the photoacoustic signals of each channel are processed to calculate the concentration of each gas component to be measured.

[0011] Based on the above technical solution, the present invention can also be improved as follows.

[0012] Optionally, before step S1, a system transfer characteristic calibration step from each gas excitation source to each acoustic sensor is included, specifically including: A single standard gas of known concentration is sequentially introduced into the photoacoustic cell, with each single standard gas corresponding to a gas component to be tested. Each time a single standard gas is introduced, only the laser emitting unit corresponding to that standard gas is turned on, and the photoacoustic signal detected by each acoustic sensor at this time is recorded. The photoacoustic signals recorded by each acoustic sensor are processed to extract the signal response amplitude at the characteristic frequency corresponding to the modulation frequency of the activated laser emitting unit. The system transfer matrix is ​​calculated and stored based on the signal response amplitude, standard gas concentration, and laser parameters. H Multiple transmission coefficients, of which the first... j The acoustic sensor for the first i Transfer coefficient of the gas source , characterizing the first i The unit concentration of the gas excitation effect on the first j The theoretical contribution intensity of the output signal of each acoustic sensor.

[0013] Optionally, step S3 includes: S301, Process the time-domain photoacoustic signals synchronously acquired by each of the acoustic sensors and extract the signal amplitude at each laser modulation frequency; S302, Based on the signal amplitude, construct an observation vector or observation matrix for decoupling calculation; S303, call the pre-stored system transfer matrix, perform calculations on the observation vector or observation matrix, and solve for the independent source strength values ​​corresponding one-to-one with the concentration of each gas to be measured; S304. Based on the independent source strength value and the pre-stored calibration parameters, calculate and output the concentration of each gas component to be measured.

[0014] Optionally, step S301 includes: Using digital lock-in amplification technology, the following operations are performed on the time-domain photoacoustic signals acquired by each acoustic sensor: For each laser modulation frequency Generates a frequency that matches the laser modulation frequency. A sinusoidal reference signal that is both synchronous and of the same frequency Sum and cosine reference signal , i This refers to the serial number of the laser emitting unit; The time-domain photoacoustic signal is compared with the sinusoidal reference signal. Sum and cosine reference signal Multiply them to obtain two product signals; The two product signals are low-pass filtered to remove high-frequency and low-frequency components, resulting in the signal at the laser modulation frequency. The in-phase component of the signal and orthogonal components ,in, jThis refers to the serial number of the acoustic sensor. According to the in-phase component and orthogonal components Calculate at frequency Signal amplitude below , represented as: .

[0015] Optionally, step S302 includes: Based on the signal amplitude of each acoustic sensor at each laser modulation frequency Construct an M-row, N-column observation matrix R, where: M represents the total number of acoustic sensors, and the row index j (j=1,2,…,M) of the matrix corresponds to the j-th acoustic sensor; N represents the total number of gas components to be tested, and the column index i (i=1,2,…,N) of the matrix corresponds to the i-th gas to be tested and its associated laser modulation frequency. ; In the observation matrix R, the element located in the j-th row and i-th column is assigned the value of the signal amplitude. .

[0016] Optionally, step S303 includes: Establish a mathematical model between the observation matrix R, the pre-stored M-row N-column system transfer matrix H, and the N-order independent source strength diagonal matrix S to be determined: R = H·S + N, where N is the noise matrix and S is the diagonal element. The independent source strength corresponding to the i-th gas; The diagonal matrix S of the independent source strengths is solved using the least squares method, specifically by calculating its corresponding independent source strength estimates. :

[0017] In this context, the superscript T denotes the matrix transpose, and the superscript -1 denotes the matrix inverse.

[0018] Optionally, step S304 includes: From each independent source strength estimate Subtract the pre-stored background source strength value obtained when only background gas is introduced under the same measurement conditions. The net source strength value is obtained. :

[0019] The net source strength value Compared with the pre-stored concentration calibration coefficient corresponding to the i-th gas Multiply to obtain the concentration value of the i-th gas. :

[0020] Simultaneously output the concentration values ​​of all gas components to be measured. .

[0021] This invention provides a photoacoustic spectroscopy detection device and method for multi-component gases based on dual-sided opposing lasers. Each analyte gas is configured with an independent excitation and sensing channel. A dual-sided opposing, parallel laser incident method is employed, coupled with correspondingly arranged acoustic sensors, to initially separate multiple signals in physical space. A transfer matrix accurately characterizing the acoustic-electric coupling relationship of the system is pre-obtained through calibration experiments. During real-time measurement, this matrix is ​​used to perform mathematical decoupling operations on the mixed signals synchronously acquired by multiple sensors, and the independent concentration information corresponding to each analyte gas is solved in reverse. This invention achieves truly synchronous and high-precision measurement of multiple gas concentrations, effectively overcoming the signal interference bottleneck in traditional single-sensor multiplexing technology. Furthermore, the device has a clear structure, strong versatility, and significantly improves the detection reliability in dynamic gas environments. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of a multi-component gas photoacoustic spectroscopy detection device based on dual-sided opposing lasers, provided in an embodiment of the present invention. Figure 2 This is a flowchart of a multi-component gas photoacoustic spectroscopy detection method provided in an embodiment of the present invention.

[0023] The attached diagram lists the components represented by each number as follows: 1. Photoacoustic cell; 1a. First buffer chamber; 1b. Photoacoustic resonant cavity; 1c. Second buffer chamber; 2. First laser entrance window; 3. Second laser entrance window; 4. First laser emitting unit; 5. Second laser emitting unit; 6. First acoustic sensor; 7. Second acoustic sensor; 8. Air inlet; 9. Air outlet; L1. First laser beam; L2. Second laser beam. Detailed Implementation

[0024] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0025] Example 1: Figure 1 The diagram shows a schematic of a multi-component gas photoacoustic spectroscopy detection device based on dual-sided opposing lasers provided in this embodiment. The device includes a photoacoustic cell 1, multiple laser emitting units, multiple acoustic sensors, and a signal processing unit. The signal processing unit is not shown in the figure, but it is an essential component of the device.

[0026] like Figure 1 As shown, the photoacoustic cell 1 is the core component of the device, and it contains multiple independent photoacoustic resonant cavities 1b corresponding to the number of laser emitting units. In this embodiment, two photoacoustic resonant cavities 1b are specifically provided. The photoacoustic cell 1 includes components along the gas flow direction (e.g., ... Figure 1 The first buffer chamber 1a, two parallel photoacoustic resonant cavities 1b, and the second buffer chamber 1c are connected sequentially (as indicated by the solid black arrow in the middle). The first buffer chamber 1a has an air inlet 8, and the second buffer chamber 1c has an air outlet 9. The first buffer chamber 1a and the second buffer chamber 1c are used to stabilize the airflow, while the two photoacoustic resonant cavities 1b serve as the core acoustic resonance and detection areas. They are physically parallel and isolated, forming independent photoacoustic resonant cavities.

[0027] like Figure 1 As shown, the device includes at least two laser emitting units; in this embodiment, specifically, it comprises a first laser emitting unit 4 and a second laser emitting unit 5. Figure 1 As shown, the first laser emitting unit 4 is correspondingly disposed on the first buffer chamber 1a. Its emitted first laser beam L1 enters through the first laser entrance window 2, continues through a photoacoustic resonator 1b, and then reaches the second buffer chamber 1c. The second laser emitting unit 5 is correspondingly disposed on the second buffer chamber 1c. Its emitted second laser beam L2 enters through the second laser entrance window 3, continues through another photoacoustic resonator 1b, and then reaches the first buffer chamber 1c. The wavelengths and modulation frequencies of the first laser beam L1 and the second laser beam L2 are different; for example, they correspond to the characteristic absorption lines and modulation frequencies of CH4 and CO gases, respectively. and Two laser beams are incident one-to-one into two photoacoustic resonant cavities 1b, that is, the first laser beam L1 is incident into... Figure 1 The photoacoustic resonator 1b above is shown, and the second laser beam L2 is incident on it. Figure 1 The photoacoustic resonant cavity 1b below is shown, and the two laser beams are parallel and do not intersect in space, achieving spatial non-interference between the laser beams. Distributing the first laser emitting unit 4 and the second laser emitting unit 5 on the first buffer chamber 1a and the second buffer chamber 1c can prevent structural interference between multiple laser emitting units, facilitate device integration and miniaturization, and also facilitate overall heat dissipation of the device, thereby improving the service life of the device.

[0028] like Figure 1 As shown, the device includes at least two acoustic sensors (e.g., a microphone-type photoacoustic sensor), specifically a first acoustic sensor 6 and a second acoustic sensor 7 in this embodiment. Figure 1As shown, the first acoustic sensor 6 and the second acoustic sensor 7 are configured in a one-to-one correspondence with the two photoacoustic resonant cavities 1b: the first acoustic sensor 6 is installed on the photoacoustic resonant cavity 1b corresponding to the first laser beam L1, and is used to detect the photoacoustic signal in the cavity; the second acoustic sensor 7 is installed on the photoacoustic resonant cavity 1b corresponding to the second laser beam L2, and is used to detect the photoacoustic signal in the cavity.

[0029] The signal processing unit (not shown in the figure) is electrically connected to both the first acoustic sensor 6 and the second acoustic sensor 7, and includes a decoupling calculation module. This decoupling calculation module is configured to process the photoacoustic signals acquired by the first acoustic sensor 6 and the second acoustic sensor 7 based on a pre-stored system transfer matrix H, perform decoupling operations, and ultimately separate independent signal values ​​corresponding only to CH4 concentration and independent signal values ​​corresponding only to CO concentration from the mixed signal, thereby resolving the concentrations of both.

[0030] In this embodiment, a spatially isolated dual-channel detection structure is constructed at the hardware level by configuring independent, parallel photoacoustic resonant cavities and corresponding laser and acoustic sensors for each gas to be tested. The dual-sided opposing configuration formed in this embodiment ensures that the two lasers and their excited photoacoustic signals do not physically interfere with each other, reducing the signal crosstalk inherent in traditional single-cavity multi-component detection. Combined with the decoupling algorithm based on the system transfer matrix in the signal processing unit, the device can perform high-precision mathematical separation of the mixed signals acquired by the dual channels, thereby achieving truly synchronous, rapid, and highly accurate measurement of the concentrations of multiple gases, while maintaining the compactness and reliability of the device structure.

[0031] Example 2: This embodiment details a high-precision, synchronous multi-component gas photoacoustic spectroscopy detection method applied to the device described in Embodiment 1. The overall flow of this detection method is as follows: Figure 2 As shown.

[0032] This embodiment provides a photoacoustic spectroscopy detection method for multi-component gases, which mainly includes steps S0 to S3.

[0033] S0, System Transmission Characteristic Calibration Steps This step is performed before the formal measurement to obtain the system transfer matrix H. The system transfer coefficients in the system transfer matrix H are defined as follows: , where represents the transfer coefficient from the i-th gas to the j-th acoustic sensor. This represents the modulation frequency of the laser emitting unit corresponding to the i-th type of gas to be tested.

[0034] This embodiment uses the simultaneous detection of two gases, methane (CH4) and carbon monoxide (CO), as an example for illustration, and mainly includes the following sub-steps (1) to (4): (1) Calibrate CH4 (i=1): A known concentration of [substance] is introduced into photoacoustic cell 1 Pure CH4 standard gas. Only the first laser emitting unit 4 (modulation frequency) is turned on. Record the photoacoustic signals detected by the first acoustic sensor 6 (j=1) and the second acoustic sensor 7 (j=2).

[0035] (2) Signal processing and coefficient calculation: The two photoacoustic sensor signals are modulated at a frequency The signal is processed using the reference frequency to extract the corresponding signal response amplitude. and .according to 、 、 And laser parameters, calculate the transfer coefficient and . The theoretical contribution of the CH4 gas source to the first acoustic sensor 6 is characterized. The contribution intensity of the CH4 gas source to the second acoustic sensor 7 (also known as the crosstalk coefficient) is characterized.

[0036] (3) Calibrate CO (i=2): After cleaning photoacoustic cell 1, a known concentration was introduced. Pure CO standard gas. Only the second laser emission unit 5 (modulation frequency) is activated. The photoacoustic signals detected by the first acoustic sensor 6 (j=1) and the second acoustic sensor 7 (j=2) are recorded to modulate the frequency. Extract the corresponding signal response amplitude for the reference frequency. and And calculate the transfer coefficient. and .

[0037] (4) Storage system transfer matrix H: Construct and store the 2x2 system transfer matrix H:

[0038] The system transfer matrix H accurately quantifies the response intensity of each gas source to each sensor, and is the key to the subsequent decoupling algorithm.

[0039] S1, Obtain the pre-calibrated system transport characteristics In the subsequent detection stage, the system transfer matrix H from each gas excitation source to each acoustic sensor, which was pre-calibrated in step S0, is directly invoked.

[0040] S2, Synchronous Excitation and Signal Acquisition This step mainly includes the following sub-steps (1) to (4): (1) Mixed gas introduction and flow path control A mixed gas sample containing at least two test gases (such as methane CH4 and carbon monoxide CO) is introduced through the inlet 8 of the photoacoustic cell 1. The mixed gas first enters the first buffer chamber 1a, where the airflow is stabilized, and then splits into two parallel and independent photoacoustic resonant cavities 1b. After interacting with the incident laser in their respective photoacoustic resonant cavities 1b, the mixed gas then merges in the second buffer chamber 1c and is finally discharged through the outlet 9, forming a continuous and stable measurement airflow environment.

[0041] (2) Synchronous control and excitation of laser The signal processing unit sends a synchronization trigger command to the drivers of the first laser emitting unit 4 and the second laser emitting unit 5. The two laser emitting units (lasers) are simultaneously activated, each emitting light with wavelengths locked to the characteristic absorption lines of its respective target gas (e.g., CH4@1653nm, CO@1567nm) at a specific frequency. , A first laser beam L1 and a second laser beam L2 are subjected to intensity modulation. These two laser beams are incident in a strictly one-to-one spatial relationship: the first laser beam L1 enters through the first laser entrance window 2 on the first buffer chamber 1a and passes through a corresponding photoacoustic resonator 1b; the second laser beam L2 enters through the second laser entrance window 3 on the second buffer chamber 1c and passes through another corresponding photoacoustic resonator 1b. This process ensures complete synchronization and isolation of the optical excitation in time and space.

[0042] Furthermore, distributing the first laser emitting unit 4 and the second laser emitting unit 5 on the first buffer chamber 1a and the second buffer chamber 1c can prevent structural interference between multiple laser emitting units, facilitate device integration and miniaturization, and also facilitate overall heat dissipation of the device.

[0043] (3) Generation of photoacoustic signals Within their respective photoacoustic resonant cavities 1b, CH4 molecules in the mixed gas selectively absorb frequencies... The laser energy of the modulated first laser beam L1 is selectively absorbed by CO molecules via a frequency... The laser energy of the modulated second laser beam L2. After absorbing the light energy, gas molecules generate periodic heat through non-radiative relaxation, thereby exciting the generation of lasers with frequencies of [missing values] within their respective photoacoustic resonant cavities 1b. and The sound waves (i.e., photoacoustic signals) are amplified. Due to the acoustic resonance effect of the cavity, sound waves of a specific frequency are significantly amplified.

[0044] (4) Synchronous acquisition of photoacoustic signals Synchronous with laser excitation, the first acoustic sensor 6 and the second acoustic sensor 7 begin operation, each located at the antinode of the corresponding photoacoustic resonant cavity 1b, simultaneously and continuously detecting changes in sound pressure within the cavity. The signal received by each sensor is the superposition of sound waves generated by the excitation of gas molecules within its respective cavity. Due to the gas connectivity, the first acoustic sensor 6 receives not only the frequency... The corresponding signal (main signal) will also receive a small amount of frequency from another cavity, coupled through gas propagation. The corresponding signal (crosstalk); similarly, the second acoustic sensor 7 not only receives the frequency The corresponding signal (main signal) will also receive a small amount of frequency from another cavity, coupled through gas propagation. The corresponding signal (crosstalk). The first acoustic sensor 6 and the second acoustic sensor 7 convert the sound pressure signal into an analog electrical signal, which is then labeled as the first time-domain photoacoustic signal. Second time domain photoacoustic signal The data acquisition card of the signal processing unit synchronously samples and converts the two analog signals to digital, ensuring strict alignment of the two data streams on the time axis. This provides a raw, synchronous data foundation for subsequent signal separation based on frequency and spatial differences.

[0045] This step S2, under hardware collaborative control, completes the entire chain from mixed gas excitation to multi-channel signal synchronous digital acquisition, which is a prerequisite for subsequent high-precision signal decoupling and concentration inversion.

[0046] S3, Signal Processing and Concentration Calculation This step is mainly executed by the decoupling calculation module in the signal processing unit, including sub-steps S301 to S304.

[0047] S301, Signal Demodulation and Amplitude Extraction This step mainly focuses on the first time-domain photoacoustic signal. Second time domain photoacoustic signal The digital phase-locked amplification process is as follows: First, for each laser modulation frequency Generates a frequency that matches the laser modulation frequency. A sinusoidal reference signal that is both synchronous and of the same frequency Sum and cosine reference signal ,For example: For frequency Generate a sinusoidal reference signal Sum and cosine reference signal ; For frequency Generate a sinusoidal reference signal Sum and cosine reference signal .

[0048] Next, the first time-domain photoacoustic signal With sinusoidal reference signal Sum and cosine reference signal Multiply them separately to obtain two product signals. Similarly, the second time-domain photoacoustic signal... With sinusoidal reference signal Sum and cosine reference signal Multiply them separately to obtain two other product signals.

[0049] Then, the two product signals are low-pass filtered to remove high-frequency and low-frequency components, resulting in the signal at the laser modulation frequency. The in-phase component of the signal and orthogonal components ,in, j This is the serial number of the acoustic sensor. For example, to obtain the frequency... The corresponding in-phase component of the signal and orthogonal components ,frequency The corresponding in-phase component of the signal and orthogonal components .

[0050] Finally, based on the in-phase components and orthogonal components Calculate at frequency Signal amplitude below , represented as:

[0051] For example, calculation and :

[0052]

[0053] S302, Construct the observation matrix This step is based on the signal amplitude of each acoustic sensor at each laser modulation frequency. Construct an M x N observation matrix R ,in: M represents the total number of acoustic sensors, and the row index of the matrix. j ( j =1,2,…,M) corresponds to the first j One acoustic sensor; N represents the total number of gas components to be measured, and the column index of the matrix. i (i =1,2,…,N) corresponds to the first i Analytical gas and its associated laser modulation frequency ; In the observation matrix R, the position located at the... j line, number i The elements of the column are those assigned the value of the signal amplitude. .

[0054] For example, this embodiment constructs an observation matrix of 2 rows (M=2 sensors) and 2 columns (N=2 types of gases). R :

[0055] S303, Matrix Decoupling Calculation For a system with M acoustic sensors and N types of gases to be measured (in this embodiment, M=N=2), steps S301 and S302 have yielded the observation matrix R (dimension M×N) and the pre-stored system transfer matrix. H (Dimensions M×N). System transfer matrix H elements This has been obtained through calibration step S0, indicating the first... i The unit concentration of the gas relative to the first j The theoretical response coefficient of each sensor.

[0056] Based on the principle of linear superposition, the observed signal can be modeled as a linear superposition of the signals from each independent gas source after transmission through the system, plus noise. Let S be an N-order diagonal matrix, whose diagonal elements... Indicates the relationship with the first i The strength of an independent source is directly proportional to the actual concentration of a gas, that is: S=diag (S1, S2, ..., SN). N is the noise matrix (dimension M × N). The following mathematical model can then be established:

[0057] To facilitate solving, the above matrix equations are usually transformed into vector form. The observation matrix R and the noise matrix N are stacked column-wise to form a column vector. and (Dimension MN×1). Meanwhile, the independent source strength vector to be determined is denoted as... =[S1,S2,...,S N ] T (Dimension N×1).

[0058] The system transfer matrix H also needs to be extended accordingly. Define the extended transfer matrix. (Dimension MN×N), its construction method is as follows: for the i-th gas (i=1,...,N), its transfer matrix The corresponding column vectors in the matrix are formed by repeating the i-th column of the original matrix H M times and stacking them. This structure reflects the contribution pattern of each gas source to all M photoacoustic sensors.

[0059] The transformed vector form equation is:

[0060] Using the transformed vector form equation, with the known observation vector... and system matrix In this case, optimally estimate the unknown independent source strength vector. .

[0061] Due to measurement noise The least squares method is usually used to solve this problem. The estimated value The criterion for least squares is to find the sum of the squares of the observed residuals. The smallest solution.

[0062] The analytical solution to this optimization problem (when) (when reversible) is

[0063] in, Representation matrix transpose, Representation matrix The inverse matrix, product Called a matrix The pseudo-inverse (Moore-Penrose generalized inverse).

[0064] The above calculated estimated values The process is called matrix decoupling.

[0065] From a mathematical perspective, the solution (in (Referring to pseudo-inverse) means the observation signal A process was conducted by The defined linear transformation. Numerically equivalent to using known system coupling relationships (included in H) to perform inverse correction on the original mixed signal, thereby canceling out signal crosstalk components caused by acoustic field cross-coupling and sensor cross-response. The final output... That is, the decoupled, significantly improved purity, and one-to-one independent source strength estimates corresponding to the concentrations of each gas. .

[0066] The independent source strength estimation vector obtained in this step This will be directly passed to subsequent steps for the final gas concentration inversion.

[0067] S304, Concentration Inversion and Output First, the independent source strength estimates for each analyte gas obtained from the decoupled S303 calculation. In addition to the signal generated by the target gas, the signal also includes the inherent background noise of the system (such as electronic noise, weak photothermal absorption by the windows and pool walls). Background subtraction is required to obtain a clean signal.

[0068] In practice, the individual source strength estimates for each gas are used. Subtract the corresponding background source intensity value that was measured and stored beforehand under the same measurement conditions (such as the same laser power, modulation frequency, and gain settings) when only background gas (usually high-purity nitrogen or zero gas) was introduced into the photoacoustic cell. .

[0069] The net source strength value is calculated using the following formula. :

[0070] Here, 'i' corresponds to the ordinal number of the gas component. This operation eliminates the inherent background bias of the system, ensuring the accuracy of subsequent concentration calculations.

[0071] Then, the concentrations of each component of the gas to be tested are calculated.

[0072] Due to net source strength value With gas concentration There exists a linear relationship between them, which is determined by the sensitivity or calibration coefficient of the device. Decision. Therefore, the net source strength value of the i-th gas is determined. Compared with the pre-stored concentration calibration coefficient corresponding to the gas Multiplying them allows us to calculate the concentration of the i-th gas. :

[0073] This calibration coefficient This is not a theoretical value, but rather determined experimentally in step S0 (system transfer characteristic calibration step). Specifically, a concentration of... When calibrating with a standard gas, record the net source strength value obtained after decoupling and subtracting the background. Then the calibration coefficient The calculation formula is:

[0074] This calibration coefficient The device's specific response to the gas (including all factors such as absorption coefficient, acoustic gain, and electrical gain) is quantified into a constant, thereby establishing a direct quantitative relationship between signal amplitude and gas concentration.

[0075] This embodiment, after calculating the concentrations of all gas components, presents the concentration inversion results in a clear and synchronous manner. For example, the signal processing unit (such as host computer software) synchronously updates the display interface, or synchronously outputs the concentration values ​​of all N gas components to be measured via a data interface. The results are typically output in the form of real-time numerical displays, data logging to files, or transmission to external systems via communication protocols (such as Modbus, 4-20mA). This operation ensures that users can simultaneously obtain the concentration information of all analytes in the gas mixture, achieving the ultimate goal of synchronous detection.

[0076] This invention provides a multi-component gas photoacoustic spectroscopy detection device and method based on dual-sided opposing lasers. Each analyte gas is configured with an independent excitation and sensing channel. A dual-sided opposing, parallel laser incident method is employed, coupled with correspondingly arranged acoustic sensors, to initially separate multiple signals in physical space. A transfer matrix accurately characterizing the acoustic-electric coupling relationship of the system is pre-obtained through calibration experiments. During real-time measurement, this matrix is ​​used to perform mathematical decoupling operations on the mixed signals synchronously acquired by multiple sensors, and the independent concentration information corresponding to each analyte gas is solved in reverse. This invention achieves truly synchronous and high-precision measurement of multiple gas concentrations, effectively overcoming the signal interference bottleneck in traditional single-sensor multiplexing technology. Furthermore, the device has a clear structure, strong universality, and significantly improves the detection reliability in dynamic gas environments.

[0077] It should be noted that the descriptions of each embodiment in the above embodiments have different focuses. For parts that are not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0078] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0079] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0080] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0081] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0082] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0083] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A multi-component gas photoacoustic spectroscopy detection device based on bilateral counter laser, characterized in that, include: The photoacoustic cell contains independent photoacoustic resonant cavities corresponding to the number of laser emitting units. At least two laser emitting units are used to emit at least two lasers with different wavelengths and modulation frequencies. The at least two lasers are incident on at least two photoacoustic resonant cavities in a one-to-one correspondence, and the lasers do not interfere with each other in space. At least two acoustic sensors are configured one-to-one with at least two of the photoacoustic resonant cavities to detect photoacoustic signals within the corresponding photoacoustic resonant cavities; The signal processing unit is electrically connected to each of the acoustic sensors and is used to extract the concentration of each gas component from the photoacoustic signal.

2. The multi-component gas photoacoustic spectroscopy detection device based on bilateral counteracting laser according to claim 1, characterized in that, The photoacoustic cell includes a first buffer chamber, at least two photoacoustic resonant cavities arranged in parallel, and a second buffer chamber, which are connected sequentially along the gas flow direction. At least two of the laser emitting units are respectively disposed on the first buffer chamber and the second buffer chamber.

3. The dual-sided counter-propagating laser-based multi-component gas photoacoustic spectroscopy detection device according to claim 1 or 2, characterized in that, The signal processing unit includes a decoupling calculation module, which is configured to: Based on the pre-stored system transfer matrix, the photoacoustic signal is decoupled to separate the independent signal values ​​corresponding to each gas component.

4. A method for detecting multi-component gases by photoacoustic spectroscopy, based on the apparatus according to any one of claims 1 to 3, characterized in that, include: S1, acquire the pre-calibrated system transfer characteristics from each gas excitation source to each acoustic sensor; S2, a mixed gas containing at least two test gases flows through the photoacoustic cell, and each laser emitting unit is controlled to work synchronously, so that each laser beam is incident on the corresponding photoacoustic resonant cavity, and photoacoustic signals are collected synchronously through each acoustic sensor; S3. Based on the transmission characteristics of the system, the photoacoustic signals of each channel are processed to calculate the concentration of each gas component to be measured.

5. The method for detecting multi-component gas photoacoustic spectroscopy according to claim 4, characterized in that, Before step S1, there is also a system transfer characteristic calibration step from each gas excitation source to each acoustic sensor, which specifically includes: A single standard gas of known concentration is sequentially introduced into the photoacoustic cell, with each single standard gas corresponding to a gas component to be tested. Each time a single standard gas is introduced, only the laser emitting unit corresponding to that standard gas is turned on, and the photoacoustic signal detected by each acoustic sensor at this time is recorded. The photoacoustic signals recorded by each acoustic sensor are processed to extract the signal response amplitude at the characteristic frequency corresponding to the modulation frequency of the activated laser emitting unit. Based on the signal response amplitude, standard gas concentration, and laser parameters, multiple transfer coefficients constituting the system transfer matrix H are calculated and stored, where the transfer coefficient of the j-th acoustic sensor to the i-th gas source is... This characterizes the theoretical contribution intensity of the excitation of the i-th gas per unit concentration to the output signal of the j-th acoustic sensor.

6. The method for detecting multi-component gas photoacoustic spectroscopy according to claim 5, characterized in that, Step S3 includes: S301, Process the time-domain photoacoustic signals synchronously acquired by each of the acoustic sensors and extract the signal amplitude at each laser modulation frequency; S302, Based on the signal amplitude, construct an observation vector or observation matrix for decoupling calculation; S303, call the pre-stored system transfer matrix, perform calculations on the observation vector or observation matrix, and solve for the independent source strength values ​​corresponding one-to-one with the concentration of each gas to be measured; S304. Based on the independent source strength value and the pre-stored calibration parameters, calculate and output the concentration of each gas component to be measured.

7. The method for detecting multi-component gas photoacoustic spectroscopy according to claim 6, characterized in that, Step S301 includes: Using digital lock-in amplification technology, the following operations are performed on the time-domain photoacoustic signals acquired by each acoustic sensor: For each laser modulation frequency Generates a frequency that matches the laser modulation frequency. A sinusoidal reference signal that is both synchronous and of the same frequency Sum and cosine reference signal i is the serial number of the laser emitting unit; The time-domain photoacoustic signal is compared with the sinusoidal reference signal. Sum and cosine reference signal Multiply them to obtain two product signals; The two product signals are low-pass filtered to remove high-frequency and low-frequency components, resulting in the signal at the laser modulation frequency. The in-phase component of the signal and orthogonal components , where j is the acoustic sensor serial number; According to the in-phase component and orthogonal components Calculation at frequency Signal amplitude below , is represented as: 。 8. The method for detecting multi-component gas photoacoustic spectroscopy according to claim 7, characterized in that, Step S302 includes: Based on the signal amplitude of each acoustic sensor at each laser modulation frequency Construct an M-row, N-column observation matrix R, where: M represents the total number of acoustic sensors, and the row index j (j=1,2,…,M) of the matrix corresponds to the j-th acoustic sensor; N represents the total number of gas components to be tested, and the column index i (i=1,2,…,N) of the matrix corresponds to the i-th gas to be tested and its associated laser modulation frequency. ; In the observation matrix R, the element located in the j-th row and i-th column is assigned the value of the signal amplitude. .

9. The method for detecting multi-component gas photoacoustic spectroscopy according to claim 8, characterized in that, Step S303 includes: Establish a mathematical model between the observation matrix R, the pre-stored M-row N-column system transfer matrix H, and the N-order independent source strength diagonal matrix S to be determined: R = H·S + N, where N is the noise matrix and S is the diagonal element. The independent source strength corresponding to the i-th gas; The diagonal matrix S of the independent source strengths is solved using the least squares method, specifically by calculating its corresponding independent source strength estimates. : In this context, the superscript T denotes the matrix transpose, and the superscript -1 denotes the matrix inverse.

10. The method for detecting multi-component gas photoacoustic spectroscopy according to claim 9, characterized in that, Step S304 includes: From each independent source strength estimate Subtract the pre-stored background source strength value obtained when only background gas is introduced under the same measurement conditions. The net source strength value is obtained. : The net source strength value Compared with the pre-stored concentration calibration coefficient corresponding to the i-th gas Multiply to obtain the concentration value of the i-th gas. : Simultaneously output the concentration values ​​of all gas components to be measured. .

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