Method and System for Particulate Matter Concentration Detection Based on Light Scattering

Abstract

This application proposes a method and system for detecting particulate matter concentration based on light scattering, relating to the field of environmental monitoring technology. The method includes: separating a laser pulse beam used for detecting particulate matter concentration into a first incident light and a second incident light; performing photoelectric detection on the first incident light to generate a first current signal synchronized with the laser pulse beam; collecting particulate matter scattered light generated by the second incident light irradiating particulate matter; performing photoelectric detection on the particulate matter scattered light to obtain a second current signal triggered by the particulate matter scattered light; using the first current signal as a reference signal, performing phase-sensitive detection on the second current signal, and extracting the effective scattered signal synchronized with the laser pulse beam from the second current signal based on the phase-sensitive detection result; and determining the particulate matter concentration based on the effective scattered signal. This solution improves the accuracy of particulate matter concentration detection.

Description

Technical Field

[0001] This application relates to the field of environmental monitoring technology, and in particular to a method and system for detecting particulate matter concentration based on light scattering. Background Technology

[0002] Light scattering particle sensors infer concentrations by detecting the scattering signal of incident light by particles. Within a range where the light source wavelength and particle size satisfy the corresponding detection ratio, the intensity of the scattered light signal is approximately positively correlated with the square of the particle size. However, the dynamic measurement range of any detector is finite. To cover a large range of particle sizes, from submicron ultrafine particles to micron coarse particles, a dilemma inevitably arises: when adapting to strong signals from large particles, the weak scattering signals from small particles (especially PM1 and below) will be completely drowned out by the detector's inherent noise, leading to missed detections of ultrafine particles; when accommodating weak signals from small particles, strong signals from large particles can easily exceed the detector's measurement range limit, causing signal saturation distortion.

[0003] This inherent contradiction directly leads to the inability of traditional solutions to simultaneously achieve large-range coverage and high-precision detection. Furthermore, sensor light source aging and temperature drift further amplify noise interference, exacerbating detection errors. Related technologies such as optical filtering and software filtering can only passively suppress some external interference, failing to fundamentally resolve the core conflict between the positive correlation between particle size and signal intensity and the limited dynamic range of the detector. Ultimately, this results in distorted particle concentration quantification results, making it particularly difficult to meet the precise detection requirements for ultrafine particles.

[0004] Therefore, how to overcome the inherent technical bottlenecks of light scattering methods, accurately extract effective signals from small particles from strong noise under the premise of large-range particle size coverage, and at the same time compensate for errors caused by devices and the environment, has become a key pain point restricting the upgrading of light scattering particulate matter detection technology. Summary of the Invention

[0005] This application provides a method and system for detecting particulate matter concentration based on light scattering, aiming to solve the technical problem of insufficient detection accuracy of sensors in particulate matter concentration detection based on light scattering in related technologies.

[0006] In a first aspect, embodiments of this application provide a method for detecting particulate matter concentration based on light scattering, comprising:

[0007] The laser pulse beam used to detect particulate matter concentration is split into a first incident beam and a second incident beam.

[0008] The first incident light is photoelectrically detected to generate a first current signal synchronized with the laser pulse beam;

[0009] Collect the particulate scattered light generated when the second incident light irradiates the particulate matter;

[0010] Photoelectric detection is performed on the scattered light from the particulate matter to obtain a second current signal triggered by the scattered light from the particulate matter;

[0011] Using the first current signal as a reference signal, phase-sensitive detection is performed on the second current signal, and based on the result of the phase-sensitive detection, an effective scattering signal synchronized with the laser pulse beam is extracted from the second current signal.

[0012] The particulate matter concentration is determined based on the effective scattering signal.

[0013] In one embodiment of this application, optionally, before separating the laser pulse beam used for detecting particulate matter concentration into a first incident light and a second incident light, the method further includes:

[0014] The laser pulse beam is focused;

[0015] Before collecting the particulate scattered light generated by the second incident light irradiating the particulate matter, the method further includes:

[0016] Stray light in the optical path containing the second incident light is filtered out, so that the light beam passing through the optical path is a collimated light beam with a uniform cross-section.

[0017] Optionally, in one embodiment of this application, collecting the particulate scattered light generated by the second incident light irradiating the particulate matter includes:

[0018] At a specified scattering angle position relative to the propagation direction of the second incident light, the scattered light from the particles is received and converged by a concave focusing mirror for the scattered light signal. Simultaneously, at the end position of the optical path where the second incident light is located, the transmitted beam in the second incident light is absorbed by an optical trap, wherein the transmitted beam is the portion of the second incident light that has not been scattered by the particles.

[0019] Optionally, in one embodiment of this application, the step of performing phase-sensitive detection on the second current signal using the first current signal as a reference signal includes:

[0020] The first current signal and the second current signal are converted into a first voltage signal and a second voltage signal respectively by a transimpedance amplifier, and the first voltage signal and the second voltage signal are synchronously converted into a first digital signal and a second digital signal by an analog-to-digital converter;

[0021] Perform point-to-point multiplication on the first digital signal and the second digital signal to obtain the product signal;

[0022] The product signal is subjected to digital low-pass filtering to obtain a DC voltage signal, which serves as an effective scattering signal synchronized with the laser pulse beam.

[0023] In one embodiment of this application, optionally, determining the particulate matter concentration based on the effective scattering signal includes:

[0024] Based on the effective scattered signals continuously acquired within a sliding time window of a predetermined length, the average value of all the effective scattered signals within the sliding time window is determined as the dynamic baseline level of the effective scattered signals in the state of no particulate matter passing through. The sliding time window always slides forward along the time development line with the latest moment as the end of the window.

[0025] Based on the dynamic baseline level, the dynamic threshold of the effective scattered signal is determined, wherein,

[0026] V th = k×V baseline + V offset ,

[0027] V th V represents the dynamic threshold of the DC voltage signal. baseline The dynamic baseline level is represented by k > 1, and the margin of the dynamic threshold relative to the baseline noise is represented by V. offset Fixed voltage bias;

[0028] If the amplitude of the effective scattered signal exceeds the dynamic threshold, the effective particulate count is increased by 1; otherwise, the effective particulate count remains unchanged.

[0029] The particulate matter concentration is determined based on the effective particulate matter count, wherein,

[0030] C= ,

[0031] C represents the particulate matter concentration, N is the cumulative increment of the effective particulate matter count within the first predetermined time interval, Q is the volumetric flow rate of the sampling gas for detecting the particulate matter concentration, and T is the first predetermined time interval.

[0032] Optionally, in one embodiment of this application, before performing phase-sensitive detection on the second current signal using the first current signal as a reference signal, the method further includes:

[0033] Perform spectral analysis on the first digital signal to determine the signal intensity at the modulation frequency of the laser pulse beam;

[0034] Perform spectrum analysis on the frequency band adjacent to the modulation frequency of the first digital signal to obtain the noise power intensity corresponding to the adjacent frequency band;

[0035] The ratio of the signal strength to the noise power intensity is determined as the current signal-to-noise ratio;

[0036] If the current signal-to-noise ratio is less than a predetermined signal-to-noise ratio threshold, and / or the rate of change of the noise power intensity is greater than a predetermined rate of change threshold, a lock-in amplification parameter adjustment strategy is executed, wherein the lock-in amplification parameter adjustment strategy is used to optimize the parameters used to extract the effective scattered signal.

[0037] Optionally, in one embodiment of this application, the execution of the lock-in amplification parameter adjustment strategy includes:

[0038] Within a predetermined angle range of the initial phase setting value, the phase of the reference signal used for phase-sensitive detection is adjusted in steps with a predetermined step size;

[0039] The step of using the first current signal as a reference signal to perform phase-sensitive detection on the second current signal includes:

[0040] In each adjustment corresponding to a predetermined step size, phase-sensitive detection is performed on the second digital signal based on the current phase setting value to obtain the DC voltage signal, and the amplitude of the DC voltage signal is recorded.

[0041] The strategy for adjusting the phase-locked amplification parameters further includes:

[0042] The maximum amplitude value is determined from all recorded amplitude values, and the phase setting value corresponding to the maximum amplitude value is determined as the optimized working phase.

[0043] The net increment of the peak value of the DC voltage signal relative to the current dynamic baseline level is obtained as the signal pulse amplitude;

[0044] If the amplitude of the signal pulse remains within a specified range close to the maximum input voltage of the analog-to-digital converter during a second predetermined time interval, the gain of the signal processing channel is reduced so that the amplitude of the signal pulse is reduced to a first reasonable proportion range of the maximum input voltage.

[0045] If the amplitude of the signal pulse is lower than a specified percentage of the maximum input voltage of the analog-to-digital converter, the gain of the signal processing channel is increased so that the amplitude of the signal pulse is increased to a second reasonable proportion range of the maximum input voltage;

[0046] If the noise power intensity is greater than a predetermined power threshold, or the width of the noise spectrum is greater than a predetermined width threshold, the cutoff frequency of the digital low-pass filter is reduced.

[0047] Secondly, embodiments of this application provide a system for detecting particulate matter concentration based on light scattering, performing the method for detecting particulate matter concentration based on light scattering as described in any embodiment of the first aspect, comprising: an optical detection unit, including a focusing lens, a beam splitter, an aperture, a concave focusing mirror for scattered light signals, a light trap, a first photodetector, and a second photodetector, wherein...

[0048] The focusing lens is configured to focus the laser pulse beam used for detecting particulate matter concentration.

[0049] The beam splitter is used to separate the focused laser pulse beam into a first incident beam and a second incident beam.

[0050] The aperture is used to filter out stray light in the optical path of the second incident light, so that the light beam passing through the optical path is a collimated light beam with a uniform cross-section.

[0051] The concave focusing mirror for the scattered light signal is positioned at a specified scattering angle relative to the propagation direction of the second incident light, and is used to receive and converge the scattered light from the particles.

[0052] The optical trap is used to absorb the transmitted beam in the second incident light, wherein the transmitted beam is the portion of the second incident light that has not been scattered by the particles.

[0053] A first photodetector is used to receive the first incident light, perform photoelectric detection on the first incident light, and generate a first current signal synchronized with the laser pulse beam.

[0054] The second photodetector is used to receive the scattered light from the particulate matter, perform photoelectric detection on the scattered light from the particulate matter, and generate a second current signal.

[0055] A lock-in amplifier signal processing unit, electrically connected to the optical detection unit, is used to receive the first current signal and the second current signal, use the first current signal as a reference signal to perform phase-sensitive detection on the second current signal, and extract an effective scattering signal synchronized with the laser pulse beam from the second current signal based on the result of the phase-sensitive detection.

[0056] A microprocessor is electrically connected to the lock-in amplified signal processing unit to receive the effective scattering signal and determine the particulate matter concentration based on the effective scattering signal.

[0057] Optionally, in one embodiment of this application, the lock-in amplification signal processing unit includes:

[0058] A first transimpedance amplifier is used to convert the first current signal into a first voltage signal;

[0059] A second transimpedance amplifier is used to convert the second current signal into a second voltage signal;

[0060] An analog-to-digital converter (ADC) is provided, wherein a first terminal of the ADC is connected to a first transimpedance amplifier, and a second terminal of the ADC is connected to a second transimpedance amplifier. The ADC is used to receive a first voltage signal and a second voltage signal via the first terminal and the second terminal, respectively, and to synchronously convert the first voltage signal and the second voltage signal into a first digital signal and a second digital signal via dual channels.

[0061] The phase-sensitive detector includes a multiplier and a digital low-pass filter. The multiplier is connected to the analog-to-digital converter and is used to receive the first voltage signal and the second voltage signal, and to perform point-to-point multiplication on the first digital signal and the second digital signal to obtain a product signal. The digital low-pass filter is connected to the multiplier and is used to receive the product signal and to perform digital low-pass filtering on the product signal to obtain a DC voltage signal, which serves as an effective scattering signal synchronized with the laser pulse beam.

[0062] Thirdly, embodiments of this application provide a computer-readable storage medium storing computer-executable instructions for performing the method for detecting particulate matter concentration based on light scattering described in the first aspect above.

[0063] The above technical solution addresses the issue of insufficient sensor accuracy in particulate matter concentration detection based on light scattering in related technologies. It splits the laser pulse beam into a reference beam and a measurement beam, and uses the synchronization signal provided by the reference beam to perform phase-sensitive detection on the particulate matter scattering signal excited by the measurement beam. This allows for the accurate extraction of pure particulate matter scattering signals synchronized only with the laser pulse beam even in strong background noise, serving as an effective basis for calculating particulate matter concentration. This avoids the problem of weak particulate matter scattering signals being masked by stray light interference from ambient background light and reflections from the sensor cavity's inner surface. It enables accurate and stable extraction of pure particulate matter scattering signals synchronized only with the laser pulse beam under complex lighting conditions, reducing the negative impact of environmental interference and sensor-specific interference on particulate matter concentration detection, and improving the accuracy of particulate matter concentration detection. More specifically, it directly addresses the inherent technical contradictions of light scattering methods, creatively solving the pain point of the incompatibility between large range and high precision in traditional technologies through an integrated solution of "laser beam splitting synchronization - phase-sensitive detection - adaptive parameter optimization." This method separates the laser pulse beam into a reference beam and a measurement beam. Using the synchronization signal generated by the reference beam as a benchmark, phase-sensitive detection is performed on the scattering signal excited by the measurement beam. This accurately filters out the effective scattering signal synchronized with the laser from strong noise. Combined with adaptive adjustment of dynamic baseline thresholds and lock-in amplification parameters, it achieves precise extraction of small-diameter signals and stable quantification of concentration across the entire range. This overcomes the physical limitations of detector dynamic range, eliminates the need for complex manual calibration, and significantly improves the detection accuracy and long-term stability of ultrafine particles in large-range particle size detection scenarios, providing a breakthrough solution for light scattering particulate matter detection technology. Attached Figure Description

[0064] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0065] Figure 1 A flowchart of a method for detecting particulate matter concentration based on light scattering according to an embodiment of this application is shown;

[0066] Figure 2 A flowchart of a method for detecting particulate matter concentration based on light scattering according to another embodiment of this application is shown;

[0067] Figure 3 A schematic diagram of a system for detecting particulate matter concentration based on light scattering according to an embodiment of this application is shown;

[0068] Figure 4A flowchart of a method for adjusting phase-locked amplification parameters according to an embodiment of this application is shown;

[0069] Figure 5 A block diagram of a computer device according to one embodiment of this application is shown;

[0070] Figure 6 A block diagram of a computer device according to another embodiment of this application is shown. Detailed Implementation

[0071] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0072] Figure 1 A flowchart of a method for detecting particulate matter concentration based on light scattering according to an embodiment of this application is shown.

[0073] like Figure 1 As shown, in a method for detecting particulate matter concentration based on light scattering according to an embodiment of this application, a light scattering particulate matter sensor is used to detect the scattering signal of particulate matter on incident light, thereby retrieving the particulate matter concentration. The method includes:

[0074] Step 102: The laser pulse beam used to detect particulate matter concentration is separated into a first incident beam and a second incident beam.

[0075] The laser pulse beam is provided by a pulse-modulated laser transmitter, which generates a square wave modulation signal with a specified frequency and duty cycle. This square wave modulation signal provides a constant drive current to the laser diode, which is a semiconductor laser. When powered on, it provides a laser pulse beam for detecting particulate matter concentration.

[0076] The laser pulse beam is separated into a first incident beam and a second incident beam. The first incident beam serves as a pure reference object that is strictly synchronized with the light source, i.e., the state of the laser pulse beam. This provides a stable synchronization benchmark for subsequent phase-sensitive detection, thereby eliminating errors introduced by aging of the pulse-modulated laser emitter, power fluctuations, or temperature drift in particulate matter concentration detection, and improving measurement accuracy. The second incident beam serves as the main measurement beam to excite the scattered light from the particulate matter, providing a basis for subsequent detection.

[0077] Optionally, the energy proportion of the first incident light in the laser pulse beam is less than that of the second incident light in the laser pulse beam. In this way, when the first incident light is separated as a reference object, excessive attenuation of the measurement beam can be avoided. Furthermore, the higher energy proportion of the second incident light in the laser pulse beam ensures that the laser irradiating the detection area has sufficient power, thereby exciting sufficiently intense particle scattered light and providing an effective detection basis for subsequent detection.

[0078] Optionally, before step 102, the laser pulse beam can be focused, that is, the laser pulse beam can be focused and the optical path collimated to facilitate subsequent optical path applications.

[0079] Step 104: Perform photoelectric detection on the first incident light to generate a first current signal synchronized with the laser pulse beam.

[0080] The first current signal reflects the intensity, timing, and phase information of the laser pulse beam and serves as a synchronization reference for subsequent phase-sensitive detection.

[0081] Step 106: Collect the particulate scattered light generated by the second incident light irradiating the particulate.

[0082] The particulate scattered light is generated by the interaction between the second incident light and the particulate matter in the gas containing the particulate matter to be detected. It can reflect the number, size and optical properties of the particulate matter in the gas, and reflect the scattering result of the laser pulse beam after being affected by the particulate matter. It can provide a source of information to be measured for subsequent signal processing.

[0083] Specifically, at a specified scattering angle position relative to the propagation direction of the second incident light, the scattered light from the particles can be received and focused by a concave focusing mirror. At the same time, at the end of the optical path of the second incident light, the transmitted beam in the second incident light can be absorbed by an optical trap, wherein the transmitted beam is the portion of the second incident light that has not been scattered by the particles.

[0084] The specified scattering angle position relative to the propagation direction of the second incident light refers to the position that can effectively avoid interference from direct strong light and thus effectively collect the scattered light caused by particles. This specified scattering angle position can be set based on actual detection needs. Placing the concave focusing lens of the scattered light signal at this position can scatter the light from particles with a sufficiently high focusing signal intensity.

[0085] Optionally, the scattering angle position is specified as a position in the range of 30° to 150° relative to the propagation direction of the second incident light, and further, it can be a position of 90°±10°.

[0086] Optionally, before step 104, stray light in the optical path of the second incident light can be filtered out to make the light beam passing through the optical path a collimated beam with a uniform cross-section, that is, to leave uniform light passing through the center of the optical path, thus ensuring the uniform collimation of the optical path.

[0087] Step 108: Perform photoelectric detection on the scattered light of the particulate matter to obtain a second current signal triggered by the scattered light of the particulate matter.

[0088] The second current signal reflects the intensity, timing, and phase information of the light scattered by the particles, that is, it reflects the behavior of the second incident light after being affected by the particles in the gas, and is the main object of subsequent phase-sensitive detection.

[0089] Step 110: Using the first current signal as a reference signal, perform phase-sensitive detection on the second current signal, and based on the result of the phase-sensitive detection, extract the effective scattering signal that is synchronized with the laser pulse beam from the second current signal.

[0090] Phase-sensitive detection aims to use the first current signal, which serves as a reference signal, as a synchronization benchmark. Through multiplication and filtering operations, it extracts only the effective components that are in phase and frequency with the reference signal from the second current signal, which is a noisy signal. In essence, it transforms signal detection from the amplitude domain to the frequency and phase domain, thereby selectively amplifying signals of specific frequencies and phases and suppressing background noise of all other frequencies and different phases. The result obtained is the effective scattered signal that is synchronized with the laser pulse beam.

[0091] Step 112: Determine the particulate matter concentration based on the effective scattering signal.

[0092] In essence, the effective scattering signal reflects a sequence of pure pulses—time-domain aligned with the laser pulse beam and with amplitude proportional to the particle scattering intensity—that are extracted synchronously after the detection portion of the laser pulse beam interacts with particles in the gas. Each pulse in the effective scattering signal corresponds to an event where a particle passes through the detection area; therefore, the number of pulses represents the number of particles. Based on this, by statistically analyzing the number of pulses per unit time and combining it with the known gas flow rate, the particle number concentration per unit volume can be calculated.

[0093] In summary, this application splits a laser pulse beam into a reference beam and a measurement beam, and uses the synchronization signal provided by the reference beam to perform phase-sensitive detection on the particulate scattering signal excited by the measurement beam. This allows for the accurate extraction of the pure particulate scattering signal synchronized only with the laser pulse beam amidst strong background noise, serving as a valid basis for calculating particulate concentration. This avoids the situation where stray light interference from ambient background light and reflections from the inner surface of the sensor cavity masks the weak particulate scattering signal. It can accurately and stably extract the pure particulate scattering signal synchronized only with the laser pulse beam under complex lighting conditions, reducing the negative impact of environmental interference and sensor-specific interference on particulate concentration detection, and improving the accuracy of particulate concentration detection. More specifically, it directly addresses the inherent technical contradictions of light scattering methods, creatively solving the pain point of the incompatibility between large range and high precision in traditional technologies through an integrated solution of "laser beam splitting synchronization - phase-sensitive detection - adaptive parameter optimization." This method separates the laser pulse beam into a reference beam and a measurement beam. Using the synchronization signal generated by the reference beam as a benchmark, phase-sensitive detection is performed on the scattering signal excited by the measurement beam. This accurately filters out the effective scattering signal synchronized with the laser from strong noise. Combined with adaptive adjustment of dynamic baseline thresholds and lock-in amplification parameters, it achieves precise extraction of small-diameter signals and stable quantification of concentration across the entire range. This overcomes the physical limitations of detector dynamic range, eliminates the need for complex manual calibration, and significantly improves the detection accuracy and long-term stability of ultrafine particles in large-range particle size detection scenarios, providing a breakthrough solution for light scattering particulate matter detection technology.

[0094] exist Figure 1 Based on the illustrated embodiments, Figure 2 A flowchart of a method for detecting particulate matter concentration based on light scattering according to another embodiment of this application is shown.

[0095] like Figure 2 As shown, another embodiment of the method for detecting particulate matter concentration based on light scattering according to this application includes:

[0096] Step 202: Photodetect the first incident light to generate a first current signal synchronized with the laser pulse beam.

[0097] Step 204: Perform photoelectric detection on the scattered light from the particulate matter to obtain the second current signal triggered by the scattered light from the particulate matter.

[0098] Step 206: Convert the first current signal and the second current signal into a first voltage signal and a second voltage signal respectively using a transimpedance amplifier.

[0099] Step 208: The first voltage signal and the second voltage signal are synchronously converted into a first digital signal and a second digital signal using an analog-to-digital converter.

[0100] A transimpedance amplifier is used to convert the weak current signal output by the photodetector into a voltage signal, which can then be digitized by an analog-to-digital converter (ADC) in subsequent steps. The current signal directly output by the photodetector has a small amplitude, is susceptible to interference, and is difficult to sample with high precision. In contrast, the voltage signal is easier for the ADC to acquire. Furthermore, the transimpedance amplifier has the ability to provide gain and suppress noise, thereby improving the signal-to-noise ratio and further enhancing the accuracy of subsequent particulate matter concentration measurements. Thus, the converted first and second voltage signals correspond to the signals in the reference and detection optical paths, respectively, providing a suitable voltage-type input for subsequent phase-sensitive detection.

[0101] Step 210: Perform point-to-point multiplication on the first digital signal and the second digital signal to obtain the product signal.

[0102] The product signal reflects the instantaneous correlation between the first digital signal and the second digital signal in the time domain. Its mean or low-frequency component is proportional to the product of the in-phase and in-frequency components of the two signals. Thus, the problem of detecting the scattered signal can be transformed into the problem of extracting the amplitude of the specific frequency and phase components.

[0103] Step 212: Perform digital low-pass filtering on the product signal to obtain a DC voltage signal, which serves as an effective scattering signal synchronized with the laser pulse beam.

[0104] Digital low-pass filtering can remove high-frequency AC noise components from the product signal while retaining the DC component that is in phase and frequency with the reference signal. This smooths the time-varying product signal into a stable DC voltage signal, the amplitude of which directly corresponds to the intensity of the effective scattered signal. Thus, it can provide an equivalent reference for subsequent particulate matter concentration detection.

[0105] Step 214: Based on the effective scattering signals continuously acquired within a predetermined sliding time window, determine the average value of all effective scattering signals within the sliding time window as the dynamic baseline level of the effective scattering signals in the state of no particulate matter passing through, and determine the dynamic threshold of the effective scattering signals based on the dynamic baseline level.

[0106] Optionally, the predetermined sliding time window is 0.5s to 10s, wherein it can be selected as any duration within the range of 1s to 3s.

[0107] Step 216: Determine whether the amplitude of the effective scattered signal exceeds the dynamic threshold. If it does, proceed to step 218; otherwise, proceed to step 220.

[0108] The sliding time window always ends at the latest time and slides forward along the timeline. In other words, as this sliding time window moves over time, the average of all effective scattered signals within it, or the dynamic baseline level of the effective scattered signals under particulate-free conditions, is also dynamically updated over time. Setting a sliding time window, i.e., setting a buffer of a predetermined length, calculates the arithmetic mean of all data in the buffer as the current dynamic baseline level whenever a new sample value arrives. This effectively smooths out random noise and reflects slow changes in the baseline in real time.

[0109] The dynamic baseline level of the effective scattered signal under particulate-free conditions reflects the sum of real-time background noise and circuit noise in the current environment. Real-time updates to the dynamic baseline level fully account for baseline drift caused by negative factors such as ambient light changes, temperature drift, or device aging. In other words, by updating the dynamic baseline level in real time, negative factors such as ambient light changes, temperature drift, or device aging are always incorporated into subsequent measurement calculations, ensuring that the measurement results fully reflect the impact of the real-time environment and improving the accuracy of the measurement results.

[0110] Based on this, a dynamic threshold for the effective scattered signal is determined according to the dynamic baseline level. This dynamic threshold is updated to an appropriate level to adapt to the current total noise level as the environment changes in real time. This avoids false triggering due to an excessively low threshold in high-noise environments and avoids missed counts due to an excessively high threshold in low-noise environments, ensuring high sensitivity and reliability of particulate matter counting under various environmental conditions. Furthermore, based on the dynamic changes in the baseline level, a moving average algorithm can be used to calculate and dynamically adjust the counting threshold of subsequent comparators, ensuring accurate counting in different environments and preventing false or missed detections.

[0111] Furthermore, V th = k×V baseline + V offset V th V represents the dynamic threshold of the DC voltage signal. baseline The dynamic baseline level is represented by k > 1, and the margin of the dynamic threshold relative to the baseline noise is represented by V. offset For fixed voltage bias.

[0112] Optionally, the value of k can be in the range of [1.5-3.0]. Alternatively, the value of k can be in the range of [2.0-2.5].

[0113] Optionally, V offset It can be set to 0 or a very small positive value.

[0114] Optionally, Voffset A fixed voltage bias of 0-50mV is provided, wherein any value within the range of 10-20mV can be selected.

[0115] In one possible design, setting k=2.0 can balance sensitivity and anti-interference capability, and setting V... offset =10mV, which can avoid false triggering caused by zero drift.

[0116] Step 218: Determine that the effective particulate count increases by 1.

[0117] Step 220: Determine that the effective particulate matter count remains unchanged.

[0118] Step 222: After counting is completed, the particulate matter concentration is determined based on the effective particulate matter count. The formula for calculating the particulate matter concentration is:

[0119] C= ,

[0120] C represents the particulate matter concentration, N is the cumulative increment of the effective particulate matter count within the first predetermined time interval, Q is the volumetric flow rate of the sampling gas for detecting the particulate matter concentration, and T is the first predetermined time interval.

[0121] In other words, the product of the volumetric flow rate of the sampled gas and the first predetermined time interval of sampling can be determined, and the particulate matter concentration is the ratio of the cumulative increase of the effective particulate matter count within the first predetermined time interval to the product.

[0122] The above technical solution synchronously acquires a reference signal and a noisy signal triggered by particulate matter scattering light. Phase-sensitive detection extracts the effective scattering signal synchronized with the laser pulse beam from the noisy signal. The dynamic threshold used for effective particulate matter counting is dynamically updated by combining the average of all effective scattering signals within a sliding time window, achieving accurate particulate matter counting. Finally, an accurate particulate matter concentration is calculated based on this count. This overcomes the negative impacts of ambient light changes, temperature drift, device aging, or light source drift on particulate matter concentration detection in real-time environments. It achieves high-precision and high-flexibility particulate matter concentration detection in complex and variable environments, improving the environmental adaptability of particulate matter concentration detection and increasing its accuracy.

[0123] Figure 3 A schematic diagram of a system for detecting particulate matter concentration based on light scattering according to an embodiment of this application is shown.

[0124] like Figure 3As shown, the system for detecting particulate matter concentration based on light scattering executes the method for detecting particulate matter concentration based on light scattering described in any of the above embodiments. The system includes: an optical detection unit, a lock-in amplified signal processing unit, and a microprocessor.

[0125] The optical detection unit includes a focusing lens, a beam splitter, an aperture, a concave focusing mirror for scattered light signals, a light trap, a first photodetector, and a second photodetector.

[0126] The focusing lens is configured to focus the laser pulse beam used for detecting particulate matter concentration. Optionally, a plano-convex lens with an infrared anti-reflection coating and a focal length of 12 mm can be used to reduce aberrations and improve transmittance.

[0127] It should be added that the laser pulse beam is provided by a pulse-modulated laser transmitter, which generates a square wave modulation signal with a specified frequency and duty cycle. This square wave modulation signal provides a constant drive current to the laser diode, which is a semiconductor laser. After being powered on, it provides a laser pulse beam for detecting particulate matter concentration. Optionally, the pulse-modulated laser transmitter can generate a square wave modulation signal with a frequency of 1 kHz and a duty cycle of 10%. The laser driver receives the modulation signal and provides a constant drive current to the laser diode. The laser diode is a semiconductor laser with a wavelength of 780 nm and an output power of 30 mW.

[0128] The beam splitter is used to separate the focused laser pulse beam into a first incident beam and a second incident beam. Optionally, the beam splitter uses a 95 / 5 beam splitter to divide the pulsed laser emitted by the laser into two beams: a 95% energy measurement beam illuminates the detection area, and the other 5% energy reference beam is guided to the reference optical path.

[0129] The aperture is used to filter out stray light in the optical path of the second incident light, so that the light beam passing through the optical path is a collimated beam with a uniform cross-section. Optionally, a circular aperture with a diameter of φ=3±0.1mm is used to ensure the uniformity and collimation of the optical path.

[0130] The concave focusing mirror for the scattered light signal is positioned at a specified scattering angle relative to the propagation direction of the second incident light, and is used to receive and converge the scattered light from the particles. Optionally, the concave focusing mirror for the scattered light signal is positioned at a specific scattering angle of 90°, used to efficiently collect the scattered light generated by particles in the airflow detection zone and converge it to the second photodetector. In addition, an air pump is provided in the airflow detection zone, which is used to actively draw the air to be measured into the optical detection cavity at a constant flow rate to ensure that the particle sampling is representative and to provide an accurate volumetric flow rate basis for concentration calculation.

[0131] The light trap is used to absorb the transmitted beam in the second incident light, wherein the transmitted beam is the portion of the second incident light that is not scattered by the particles. Optionally, the light trap is coated with a matte varnish to absorb the portion of the beam that is not scattered by the particles.

[0132] A first photodetector is used to receive the first incident light, perform photodetection on the first incident light, and generate a first current signal synchronized with the laser pulse beam. Optionally, the first photodetector is a photodiode of the same type as the second photodetector, used to receive a reference beam and convert it into a first current signal strictly synchronized with the laser pulse.

[0133] A second photodetector is used to receive the scattered light from the particles, perform photoelectric detection on the scattered light, and generate a second current signal. Optionally, the second photodetector is a silicon photodiode located at the focal point of the collecting lens, used to convert the converged scattered light into a second current signal containing particle scattering pulses and environmental noise.

[0134] A lock-in amplification signal processing unit, electrically connected to the optical detection unit, is used to receive the first current signal and the second current signal, use the first current signal as a reference signal to perform phase-sensitive detection on the second current signal, and extract an effective scattering signal synchronized with the laser pulse beam from the second current signal based on the result of the phase-sensitive detection.

[0135] The microprocessor is electrically connected to the lock-in amplified signal processing unit to receive the effective scattering signal and determine the particulate matter concentration based on the effective scattering signal.

[0136] In one embodiment of this application, the lock-in signal processing unit optionally includes: a first transimpedance amplifier, a second transimpedance amplifier, an analog-to-digital converter, and a phase-sensitive detector.

[0137] A first transimpedance amplifier is used to convert the first current signal into a first voltage signal; a second transimpedance amplifier is used to convert the second current signal into a second voltage signal; a first terminal of the analog-to-digital converter is connected to the first transimpedance amplifier, and a second terminal of the analog-to-digital converter is connected to the second transimpedance amplifier. The analog-to-digital converter is used to receive the first voltage signal and the second voltage signal through the first terminal and the second terminal respectively, and to synchronously convert the first voltage signal and the second voltage signal into a first digital signal and a second digital signal through a dual-channel configuration; a phase-sensitive detector includes a multiplier and a digital low-pass filter. The multiplier is connected to the analog-to-digital converter and is used to receive the first voltage signal and the second voltage signal, and to perform point-to-point multiplication on the first digital signal and the second digital signal to obtain a product signal. The digital low-pass filter is connected to the multiplier and is used to receive the product signal and to perform digital low-pass filtering on the product signal to obtain a DC voltage signal, which serves as an effective scattering signal synchronized with the laser pulse beam.

[0138] Optionally, the analog-to-digital converter is a 24-bit precision dual-channel synchronous sampling analog-to-digital converter.

[0139] Optionally, the cutoff frequency of the digital low-pass filter is set to 1 / 100, i.e., 10Hz, and the system response time is 100ms, which meets the counting requirements of most aerosol particles. This filters out all high-frequency AC noise components, ultimately outputting a smooth DC voltage signal. The amplitude of the DC voltage signal is directly proportional to the intensity of the component in the second current signal that is in phase and at the same frequency as the first current signal, i.e., a pure particulate scattering signal.

[0140] In addition, the system also includes a communication interface module, which outputs particulate matter concentration to a host computer or display device via a UART (Universal Asynchronous Receiver / Transmitter) or I2C (Integrated Circuit Bus) interface.

[0141] The system uses the above Figure 1 and Figure 2 The solution described in any one of the embodiments shown has all the above-mentioned technical effects, which will not be repeated here.

[0142] exist Figures 1 to 3 Based on any of the embodiments shown, Figure 4 A flowchart of a lock-in amplifier parameter adjustment method according to an embodiment of this application is shown.

[0143] like Figure 4 As shown, a lock-in amplification parameter adjustment method according to an embodiment of this application includes:

[0144] Step 402: Perform spectrum analysis on the first digital signal to determine the signal intensity at the modulation frequency of the laser pulse beam.

[0145] The first digital signal is subjected to spectrum analysis, that is, the microprocessor performs fast Fourier transform analysis on the reference signal to identify the signal intensity at the modulation frequency of the laser pulse beam. This signal intensity reflects the actual output energy level of the current laser pulse source at the modulation frequency, that is, the instantaneous intensity of the source.

[0146] Step 404: Perform spectrum analysis on the frequency band adjacent to the modulation frequency of the first digital signal to obtain the noise power intensity corresponding to the adjacent frequency band.

[0147] The adjacent frequency band refers to a continuous frequency range near the modulation frequency that does not include the region where the signal energy is concentrated. It is used to assess the energy level of background noise within this frequency band. The noise power analysis of the adjacent frequency band is also based on the Fast Fourier Transform. The noise power intensity corresponding to the adjacent frequency band reflects the magnitude of interference energy introduced by ambient stray light and circuit background noise near the current modulation frequency.

[0148] Step 406: Determine the ratio of the signal strength to the noise power intensity as the current signal-to-noise ratio.

[0149] The current signal-to-noise ratio (SNR) is a quantitative indicator of the system's ability to extract effective scattered signals in the current environment. It reflects the prominence of the effective scattered signal relative to the background noise and directly determines the accuracy of signal detection.

[0150] Step 408: If the current signal-to-noise ratio is less than a predetermined signal-to-noise ratio threshold, and / or the rate of change of the noise power intensity is greater than a predetermined rate of change threshold, the lock-in amplification parameter adjustment strategy is allowed to be executed, wherein the lock-in amplification parameter adjustment strategy is used to optimize the parameters used to extract the effective scattered signal.

[0151] The predetermined signal-to-noise ratio threshold is the minimum signal-to-noise ratio required for the quality of the extracted effective scattered signal to meet the standard. If the current signal-to-noise ratio is less than the predetermined signal-to-noise ratio threshold, it indicates that the quality of the effective scattered signal extracted by the lock-in amplifier signal processing unit under the current parameter configuration cannot meet the standard.

[0152] The rate of change of noise power intensity reflects the abrupt change rate of environmental noise level. The predetermined rate of change threshold refers to the maximum rate of change of environmental noise level when the quality of the extracted effective scattered signal meets the standard. If the rate of change of noise power intensity is greater than the predetermined rate of change threshold, it indicates that the environmental noise level fluctuates too much, resulting in severe environmental interference, which makes it impossible for the quality of the effective scattered signal extracted by the lock-in amplifier signal processing unit to meet the standard under the current parameter configuration.

[0153] Therefore, if the current signal-to-noise ratio is less than a predetermined signal-to-noise ratio threshold, and / or the rate of change of the noise power intensity is greater than a predetermined rate of change threshold, the parameters used by the lock-in amplifier signal processing unit to extract the effective scattered signal need to be optimized.

[0154] First, proceed to the phase calibration step.

[0155] Step 410: Within the predetermined angle range of the initial phase setting value, the phase of the reference signal used for phase-sensitive detection is adjusted in steps with a predetermined step size. In each adjustment corresponding to the predetermined step size, phase-sensitive detection is performed on the second digital signal based on the current phase setting value to obtain the DC voltage signal, and the amplitude of the DC voltage signal is recorded.

[0156] The initial phase setting reflects the phase alignment state between the reference signal and the effective scattered signal preset by the system before adjustment. This value may deviate from the optimal value due to environmental changes or device drift. The adjustment corresponding to each predetermined step size, that is, the phase alignment state is adjusted in a discretized manner within a limited angle range, so that the reference signal and the effective scattered signal are strictly identical, maximizing the multiplier output. This ensures that the phase-sensitive detection of the lock-in amplifier signal processing unit is always in the highest sensitivity operating state, maximizing the extraction of the required signal and suppressing noise, thereby improving the accuracy of particle counting.

[0157] Optionally, the predetermined angle range is from -10° to +10°, and the predetermined step size is 0.5°.

[0158] Optionally, the phase of the reference signal is adjusted by any predetermined step size within the range of 0.1° to 1°, the amplitude of the DC voltage signal corresponding to each phase is recorded, and the phase corresponding to the largest amplitude is taken as the optimized working phase.

[0159] Step 412: Determine the maximum amplitude value among all recorded amplitude values, and determine the phase setting value corresponding to the maximum amplitude value as the optimized working phase.

[0160] The phase setting value corresponding to the maximum amplitude ensures optimal alignment between the reference signal and the effective scattered signal. At this point, the output signal of the lock-in amplifier signal processing unit is strongest, and the signal-to-noise ratio is highest, thus ensuring optimal detection sensitivity of the particulate matter scattering signal. It should be noted that the above phase calibration process can be completed within milliseconds and has no impact on the continuity of counting.

[0161] Next, we will proceed to the gain optimization step.

[0162] Step 414: Obtain the net increment of the peak value of the DC voltage signal relative to the current dynamic baseline level as the signal pulse amplitude.

[0163] The amplitude of the signal pulse reflects the effective signal strength generated by a single particle scattering event.

[0164] If the amplitude of the signal pulse remains within a specified range close to the maximum input voltage of the analog-to-digital converter during the second predetermined time interval, it indicates that the current system gain setting is too high, which may cause the signal to approach saturation. The gain needs to be reduced to avoid signal clipping distortion.

[0165] If the amplitude of the signal pulse remains below a specified percentage of the maximum input voltage of the analog-to-digital converter for a second predetermined time interval, it indicates that the current system gain setting is too low and the signal amplitude is too small. The gain needs to be increased to improve the detection sensitivity.

[0166] Step 416: If the signal pulse amplitude remains within a specified range near the maximum input voltage of the analog-to-digital converter during a second predetermined time interval, reduce the gain of the signal processing channel to reduce the signal pulse amplitude to a first reasonable proportion range of the maximum input voltage.

[0167] Optionally, the second predetermined time interval is any duration within the range of 1s to 5s.

[0168] Optionally, the specified range of the maximum input voltage is 80%-95% of the maximum input voltage of the analog-to-digital converter.

[0169] Step 418: If the signal pulse amplitude is lower than a specified percentage of the maximum input voltage of the analog-to-digital converter, increase the gain of the signal processing channel to increase the signal pulse amplitude to a second reasonable percentage range of the maximum input voltage.

[0170] Optionally, the first reasonable ratio range is a specified range below 100% of the maximum input voltage. Optionally, the gain of the signal processing channel is reduced until the signal pulse amplitude is between 30% and 50%.

[0171] Optionally, the second reasonable range is 10% below the maximum input voltage.

[0172] Optionally, when reducing or increasing the gain of the signal processing channel, the signal pulse amplitude can be adjusted to a range of 30%-70% of the maximum input voltage.

[0173] Step 420: If the noise power intensity is greater than a predetermined power threshold, or the width of the noise spectrum is greater than a predetermined width threshold, reduce the cutoff frequency of the digital low-pass filter.

[0174] Noise power intensity reflects the total interference magnitude of ambient background light and circuit noise, while the width of the noise spectrum reflects the distribution breadth of interference noise in the frequency domain. Based on this, reducing the cutoff frequency of the digital low-pass filter can enhance the system's ability to suppress high-frequency interference with strong total interference capabilities and broadband noise with wide distribution, thereby effectively improving the signal-to-noise ratio of the signal output by the lock-in amplifier signal processing unit.

[0175] In addition, after completing the parameter adjustments in the above steps, if the increase in the signal-to-noise ratio relative to the signal-to-noise ratio before adjustment reaches the specified increment threshold, it indicates that the adjustment has effectively optimized the detection performance of the system and the system's ability to extract the target signal has been substantially improved. Therefore, the adjustment can be determined to be effective, and the parameters obtained from this adjustment can be locked and applied to the lock-in amplifier signal processing unit.

[0176] Conversely, if the increase in signal-to-noise ratio relative to the signal-to-noise ratio before adjustment does not reach the specified increment threshold, it indicates that the adjustment has failed to effectively optimize the detection performance of the system. Therefore, the adjustment can be determined to be invalid, and the system should revert to the previous parameter combination or enable the backup parameter set, and try to adjust again later.

[0177] Optionally, the incremental threshold can be specified as 3dB.

[0178] It is understood that this application actually uses the first detector of the first beam splitter as the detection signal reference, and the second detector of the other beam splitter for signal detection and phase-locked amplification threshold demodulation signal processing. Based on this, the experimental data obtained by applying the detection methods of optical filtering and software filtering in related technologies and the technical solution of this application are compared as shown in Table 1 below. It can be seen that the technical solution of this application effectively optimizes performance in multiple dimensions compared to the detection methods of optical filtering and software filtering, including PM0.5 particle detection error, signal-to-noise ratio under strong background light, baseline drift over 30 days of continuous operation, and stable working cycle without calibration.

[0179] Table 1

[0180]

[0181] The above technical solution, by analyzing the spectral characteristics of the reference and detection signals in real time and dynamically evaluating the system's signal-to-noise ratio, allows for the calibration of the lock-in amplifier signal processing unit's parameters, including phase adjustment, gain optimization, and cutoff frequency adjustment. This enables the automatic maintenance of optimal signal detection performance of the lock-in amplifier signal processing unit even under complex and variable environmental noise and sensor drift conditions, significantly improving the accuracy of particulate matter counting. It also enhances the adaptability of the light scattering-based particulate matter concentration detection system to environmental changes and equipment aging, effectively solving the measurement error problems caused by environmental interference and device drift in related technologies.

[0182] In another embodiment, this application provides a computer device, which may be a server, and its internal structure diagram may be as follows. Figure 5 As shown, the computer device includes a processor, memory, network interface, and database connected via a system bus. The processor provides computing and control capabilities. The memory includes non-volatile and / or volatile storage media and internal memory. The non-volatile storage media stores the operating system, computer programs, and database. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage media. The network interface is used to communicate with external clients via a network connection. When the computer program is executed by the processor, it can implement the method for detecting particulate matter concentration based on light scattering as described in any of the above embodiments.

[0183] In one embodiment, this application also provides a computer device, which can be a client, and its internal structure diagram can be as follows: Figure 6 As shown, the computer device includes a processor, memory, network interface, display screen, and input device connected via a system bus. The processor provides computing and control capabilities. The memory includes a non-volatile storage medium and internal memory. The non-volatile storage medium stores an operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage medium. The network interface is used to communicate with an external server via a network connection. When the computer program is executed by the processor, it can implement the method for detecting particulate matter concentration based on light scattering as described in any of the above embodiments.

[0184] Any of the computer devices described in the embodiments of this application exist in various forms, including but not limited to:

[0185] (1) Mobile communication devices: These devices are characterized by their mobile communication capabilities and primarily aim to provide voice and data communication. These terminals include smartphones, multimedia phones, feature phones, and low-end phones.

[0186] (2) Ultra-mobile personal computer devices: These devices fall under the category of personal computers, possessing computing and processing capabilities, and generally also have mobile internet access features. These terminals include PDAs, MIDs, and UMPCs, etc.

[0187] (3) Portable entertainment devices: These devices can display and play multimedia content. This category includes: audio and video players, handheld game consoles, e-books, as well as smart toys, wearable devices, and portable car navigation devices.

[0188] (4) Server: A device that provides computing services. The components of a server include a processor, hard disk, memory, system bus, etc. Servers are similar to general computer architectures, but because they need to provide highly reliable services, they have higher requirements in terms of processing power, stability, reliability, security, scalability, and manageability.

[0189] (5) Other electronic devices with data interaction functions.

[0190] Additionally, embodiments of this application provide a computer-readable storage medium storing computer-executable instructions, which are used to perform the following steps:

[0191] The laser pulse beam used to detect particulate matter concentration is split into a first incident beam and a second incident beam.

[0192] The first incident light is photoelectrically detected to generate a first current signal synchronized with the laser pulse beam;

[0193] Collect the particulate scattered light generated when the second incident light irradiates the particulate matter;

[0194] Photoelectric detection is performed on the scattered light from the particulate matter to obtain a second current signal triggered by the scattered light from the particulate matter;

[0195] Using the first current signal as a reference signal, phase-sensitive detection is performed on the second current signal, and based on the result of the phase-sensitive detection, an effective scattering signal synchronized with the laser pulse beam is extracted from the second current signal.

[0196] The particulate matter concentration is determined based on the effective scattering signal.

[0197] It should be noted that the functions or steps that can be implemented by the computer-readable storage medium or computer device described above can be referred to the relevant descriptions in the foregoing method embodiments. To avoid repetition, they will not be described one by one here.

[0198] The technical solution of this application has been described in detail above with reference to the accompanying drawings. This technical solution divides the laser pulse beam into a reference beam and a measurement beam, and uses the synchronization signal provided by the reference beam to perform phase-sensitive detection on the particulate scattering signal excited by the measurement beam. This allows for the accurate extraction of the pure particulate scattering signal synchronized only with the laser pulse beam amidst strong background noise, serving as an effective basis for calculating particulate concentration. This avoids the situation where weak particulate scattering signals are masked by stray light interference from ambient background light and reflections from the inner surface of the sensor cavity. It enables accurate and stable extraction of the pure particulate scattering signal synchronized only with the laser pulse beam under complex lighting conditions, reducing the negative impact of environmental interference and sensor-specific interference on particulate concentration detection and improving the accuracy of particulate concentration detection.

[0199] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0200] It should be understood that although the terms "first," "second," etc., may be used to describe current signals in the embodiments of this application, these current signals should not be limited to these terms. These terms are only used to distinguish current signals from each other. For example, without departing from the scope of the embodiments of this application, a first current signal may also be referred to as a second current signal, and similarly, a second current signal may also be referred to as a first current signal.

[0201] Depending on the context, the word "if" as used here can be interpreted as "when," "when," "in response to determination," or "in response to detection." Similarly, depending on the context, the phrase "if determination" or "if detection (of the stated condition or event)" can be interpreted as "when determination," "in response to determination," "when detection (of the stated condition or event)," or "in response to detection (of the stated condition or event)."

[0202] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0203] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0204] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or in a combination of hardware and software functional units.

[0205] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium. When executed, the computer program can include the processes of the embodiments of the above methods. Any references to memory, storage, databases, or other media used in the embodiments provided in this application can include non-volatile and / or volatile memory. Non-volatile memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory may include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in a variety of forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), dual data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), RAMbus direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM), etc.

[0206] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A method for detecting particulate matter concentration based on light scattering, characterized in that, include: The laser pulse beam used to detect particulate matter concentration is split into a first incident beam and a second incident beam. The first incident light is photoelectrically detected to generate a first current signal synchronized with the laser pulse beam; Collect the particulate scattered light generated when the second incident light irradiates the particulate matter; Photoelectric detection is performed on the scattered light from the particulate matter to obtain a second current signal triggered by the scattered light from the particulate matter; Using the first current signal as a reference signal, phase-sensitive detection is performed on the second current signal, and based on the result of the phase-sensitive detection, an effective scattering signal synchronized with the laser pulse beam is extracted from the second current signal. Specifically, the phase-sensitive detection of the second current signal using the first current signal as a reference signal includes: converting the first current signal and the second current signal into a first voltage signal and a second voltage signal respectively using a transimpedance amplifier; synchronously converting the first voltage signal and the second voltage signal into a first digital signal and a second digital signal using an analog-to-digital converter; performing point-to-point multiplication on the first digital signal and the second digital signal to obtain a product signal; and performing digital low-pass filtering on the product signal to obtain a DC voltage signal, which serves as the effective scattering signal synchronized with the laser pulse beam. Based on the effective scattering signal, the particulate matter concentration is determined, including: Based on the effective scattered signals continuously acquired within a sliding time window of a predetermined length, the average value of all the effective scattered signals within the sliding time window is determined as the dynamic baseline level of the effective scattered signals in the state of no particulate matter passing through. The sliding time window always slides forward along the time development line with the latest moment as the end of the window. Based on the dynamic baseline level, the dynamic threshold of the effective scattered signal is determined, wherein, V th = k×V baseline + V offset , V th V represents the dynamic threshold of the DC voltage signal. baseline The dynamic baseline level is represented by k > 1, and the margin of the dynamic threshold relative to the baseline noise is represented by V. offset Fixed voltage bias; If the amplitude of the effective scattered signal exceeds the dynamic threshold, the effective particulate count is increased by 1; otherwise, the effective particulate count remains unchanged. The particulate matter concentration is determined based on the effective particulate matter count, wherein, C= ， C represents the particulate matter concentration, N is the cumulative increment of the effective particulate matter count within the first predetermined time interval, Q is the volumetric flow rate of the sampling gas for detecting the particulate matter concentration, and T is the first predetermined time interval.

2. The method for detecting particulate matter concentration based on light scattering according to claim 1, characterized in that, Before separating the laser pulse beam used for detecting particulate matter concentration into a first incident beam and a second incident beam, the method further includes: The laser pulse beam is focused; Before collecting the particulate scattered light generated by the second incident light irradiating the particulate matter, the method further includes: Stray light in the optical path containing the second incident light is filtered out, so that the light beam passing through the optical path is a collimated light beam with a uniform cross-section.

3. The method for detecting particulate matter concentration based on light scattering according to claim 1 or 2, characterized in that, The collection of particulate scattered light generated by the second incident light irradiating the particulate matter includes: At a specified scattering angle position relative to the propagation direction of the second incident light, the scattered light from the particles is received and converged by a concave focusing mirror for the scattered light signal. Simultaneously, at the end position of the optical path where the second incident light is located, the transmitted beam in the second incident light is absorbed by an optical trap, wherein the transmitted beam is the portion of the second incident light that has not been scattered by the particles.

4. The method for detecting particulate matter concentration based on light scattering according to claim 1, characterized in that, Before performing phase-sensitive detection on the second current signal using the first current signal as a reference signal, the method further includes: Perform spectral analysis on the first digital signal to determine the signal intensity at the modulation frequency of the laser pulse beam; Perform spectrum analysis on the frequency band adjacent to the modulation frequency of the first digital signal to obtain the noise power intensity corresponding to the adjacent frequency band; The ratio of the signal strength to the noise power intensity is determined as the current signal-to-noise ratio; If the current signal-to-noise ratio is less than a predetermined signal-to-noise ratio threshold, and / or the rate of change of the noise power intensity is greater than a predetermined rate of change threshold, a lock-in amplification parameter adjustment strategy is executed, wherein the lock-in amplification parameter adjustment strategy is used to optimize the parameters used to extract the effective scattered signal.

5. The method for detecting particulate matter concentration based on light scattering according to claim 4, characterized in that, The strategy for adjusting the phase-locked amplification parameters includes: Within a predetermined angle range of the initial phase setting value, the phase of the reference signal used for phase-sensitive detection is adjusted in steps with a predetermined step size; The step of using the first current signal as a reference signal to perform phase-sensitive detection on the second current signal includes: In each adjustment corresponding to a predetermined step size, phase-sensitive detection is performed on the second digital signal based on the current phase setting value to obtain the DC voltage signal, and the amplitude of the DC voltage signal is recorded. The strategy for adjusting the phase-locked amplification parameters further includes: The maximum amplitude value is determined from all recorded amplitude values, and the phase setting value corresponding to the maximum amplitude value is determined as the optimized working phase. The net increment of the peak value of the DC voltage signal relative to the current dynamic baseline level is obtained as the signal pulse amplitude; If the amplitude of the signal pulse remains within a specified range close to the maximum input voltage of the analog-to-digital converter during a second predetermined time interval, the gain of the signal processing channel is reduced so that the amplitude of the signal pulse is reduced to a first reasonable proportion range of the maximum input voltage. If the amplitude of the signal pulse is lower than a specified percentage of the maximum input voltage of the analog-to-digital converter, the gain of the signal processing channel is increased so that the amplitude of the signal pulse is increased to a second reasonable proportion range of the maximum input voltage; If the noise power intensity is greater than a predetermined power threshold, or the width of the noise spectrum is greater than a predetermined width threshold, the cutoff frequency of the digital low-pass filter is reduced.

6. A system for detecting particulate matter concentration based on light scattering, characterized in that, The method for detecting particulate matter concentration based on light scattering as described in any one of claims 1 to 5 includes: The optical detection unit includes a focusing lens, a beam splitter, an aperture, a concave focusing mirror for scattered light signals, a light trap, a first photodetector, and a second photodetector. The focusing lens is configured to focus the laser pulse beam used for detecting particulate matter concentration. The beam splitter is used to separate the focused laser pulse beam into a first incident beam and a second incident beam. The aperture is used to filter out stray light in the optical path of the second incident light, so that the light beam passing through the optical path is a collimated light beam with a uniform cross-section. The concave focusing mirror for the scattered light signal is positioned at a specified scattering angle relative to the propagation direction of the second incident light, and is used to receive and converge the scattered light from the particles. The optical trap is used to absorb the transmitted beam in the second incident light, wherein the transmitted beam is the portion of the second incident light that has not been scattered by the particles. A first photodetector is used to receive the first incident light, perform photodetection on the first incident light, and generate a first current signal synchronized with the laser pulse beam. The second photodetector is used to receive the scattered light from the particulate matter, perform photoelectric detection on the scattered light from the particulate matter, and generate a second current signal. A lock-in amplifier signal processing unit, electrically connected to the optical detection unit, is used to receive the first current signal and the second current signal, use the first current signal as a reference signal to perform phase-sensitive detection on the second current signal, and extract an effective scattering signal synchronized with the laser pulse beam from the second current signal based on the result of the phase-sensitive detection. A microprocessor is electrically connected to the lock-in amplified signal processing unit to receive the effective scattering signal and determine the particulate matter concentration based on the effective scattering signal.

7. The system for detecting particulate matter concentration based on light scattering according to claim 6, characterized in that, The lock-in amplification signal processing unit includes: A first transimpedance amplifier is used to convert the first current signal into a first voltage signal; A second transimpedance amplifier is used to convert the second current signal into a second voltage signal; An analog-to-digital converter (ADC) is provided, wherein a first terminal of the ADC is connected to a first transimpedance amplifier, and a second terminal of the ADC is connected to a second transimpedance amplifier. The ADC is used to receive a first voltage signal and a second voltage signal via the first terminal and the second terminal, respectively, and to synchronously convert the first voltage signal and the second voltage signal into a first digital signal and a second digital signal via dual channels. The phase-sensitive detector includes a multiplier and a digital low-pass filter. The multiplier is connected to the analog-to-digital converter and is used to receive the first voltage signal and the second voltage signal, and to perform point-to-point multiplication on the first digital signal and the second digital signal to obtain a product signal. The digital low-pass filter is connected to the multiplier and is used to receive the product signal and to perform digital low-pass filtering on the product signal to obtain a DC voltage signal, which serves as an effective scattering signal synchronized with the laser pulse beam.

8. A computer-readable storage medium, characterized in that, The device stores computer-executable instructions configured to perform the method for detecting particulate matter concentration based on light scattering as described in any one of claims 1 to 5.

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