A semiconductor laser particle counting sensor, particle monitoring method and system

Abstract

The application provides a semiconductor laser particle counting sensor, a particle monitoring method and a system, relates to the technical field of particle counting devices, and comprises a shell, a laser light source, a first photodetector group, a second photodetector group and a signal processing module, a counting cavity is arranged in the shell, and a photosensitive area for particle monitoring is formed in the counting cavity; the laser light source is arranged on the shell and is used for generating a light beam for irradiating the photosensitive area. According to the application, the first photodetector group and the second photodetector group are oppositely arranged on both sides of the photosensitive area along a first direction which is perpendicular to the motion direction of the particles and perpendicular to the propagation direction of the light beam, the particles pass between the two groups of detectors, the signal processing module is used for synchronously acquiring the scattering signal intensity distribution output by the two groups of detectors, the three-dimensional space coordinates of the particles are directly solved in combination with the space coordinates of the detectors, and the application does not need any focusing or imaging optical elements, so that the material cost and assembly complexity of the sensor are greatly reduced.

Description

Technical Field

[0001] This invention relates to the field of particle counting device technology, and in particular to a semiconductor laser particle counting sensor, particle monitoring method and system. Background Technology

[0002] Laser particle counters are core instruments for aerosol particulate matter monitoring. Their basic principle is that a laser source generates a beam that illuminates a photosensitive area. When the particles to be measured pass through the photosensitive area with the airflow, light scattering occurs. A photodetector receives the scattered light and converts it into electrical pulse signals. The particle size and concentration are then determined by analyzing the pulse amplitude and number. Traditional laser particle counters typically employ a single light source and a single detector structure, using concave or ellipsoidal mirrors to focus the scattered light from the photosensitive area onto the detector surface to improve light collection efficiency. This type of solution is widely used in cleanroom monitoring, ambient air quality detection, and industrial emission monitoring due to its simple structure and mature technology.

[0003] Existing single-detector particle counters have several drawbacks. For example, the manufacturing precision requirements for concave or ellipsoidal mirrors are extremely high, and the coating process is complex, resulting in high sensor costs. Additionally, the mirror surface easily attracts dust, generating stray light, increasing system noise, and reducing the signal-to-noise ratio for small-diameter particles. Furthermore, a single detector can only acquire the total intensity of scattered light and cannot determine the specific spatial location of the particle within the photosensitive area. Since the trajectory of particles in actual airflow does not strictly pass through the center of the photosensitive area, the efficiency of the scattered light collected by the concave mirror varies significantly at different particle positions. This results in particles of the same diameter generating different pulse amplitudes due to their different passing positions, causing particle size measurement errors. Moreover, the single-detector solution cannot obtain the spatial coordinate information of the particle within the photosensitive area, thus failing to achieve particle trajectory tracking, velocity measurement, and multi-particle spatial distribution analysis. This severely limits the use of particle counters in high-end applications such as flow field diagnostics and pollution source localization. Summary of the Invention

[0004] In view of this, the present invention proposes a semiconductor laser particle counting sensor, particle monitoring method and system. By setting a first photodetector group and a second photodetector group opposite each other on both sides of the photosensitive area along a first direction perpendicular to the particle motion direction and the beam propagation direction, the particle passes between the two groups of detectors. The signal processing module synchronously acquires the intensity distribution of the scattered signal output by the two groups of detectors, and directly calculates the three-dimensional spatial coordinates of the particle by combining the spatial coordinates of each detector. It does not require any focusing or imaging optical elements, which greatly reduces the material cost and assembly complexity of the sensor. At the same time, it avoids stray light noise caused by concave mirrors, improves the signal-to-noise ratio of small-diameter particles, and achieves quantitative acquisition of particle spatial coordinates without imaging optical system, providing a basis for position compensation in subsequent particle size measurement.

[0005] The technical solution of this invention is implemented as follows: In a first aspect, the present invention provides a semiconductor laser particle counting sensor, comprising a housing, a laser source, a first photodetector group, a second photodetector group, and a signal processing module, wherein... A counting chamber is provided inside the housing, and a photosensitive area for particle monitoring is formed inside the counting chamber; A laser source is mounted on the housing to generate a beam of light that illuminates the photosensitive area; The first photodetector group is disposed on the housing and located on the first side of the photosensitive area along the first direction, which is perpendicular to the expected direction of particle movement and perpendicular to the direction of beam propagation. The second photodetector group is disposed on the housing and located on the second side of the photosensitive area along the first direction. The first side and the second side are arranged opposite to each other, so that when a particle passes through the photosensitive area, it passes between the first photodetector group and the second photodetector group. The signal processing module is electrically connected to the first photodetector group and the second photodetector group. It is used to synchronously acquire the first scattering signal set output by the first photodetector group and the second scattering signal set output by the second photodetector group. Based on the intensity distribution of the first scattering signal set and the second scattering signal set, combined with the spatial coordinates of each detector in the first photodetector group and the second photodetector group, the number of particles and spatial coordinates of the current photosensitive region are obtained.

[0006] In one embodiment, it further includes a first circuit board and a second circuit board, wherein, The housing is provided with a first opening and a second opening, which are located on both sides of the counting cavity along the first direction and are in communication with the counting cavity. The first photodetector group is fixed on the first circuit board, which is sealed on the housing and covers the first opening, so that the first photodetector group is located inside the first opening and the photosensitive surface of each photodetector faces the photosensitive area. The second photodetector group is fixed on the second circuit board, which is sealed on the housing and covers the second opening, so that the second photodetector group is located inside the second opening and the photosensitive surface of each photodetector faces the photosensitive area. The first circuit board and the second circuit board are used to lead the output signals of the first photodetector group and the second photodetector group to the signal processing module.

[0007] In one embodiment, the photodetectors in the first photodetector group and the second photodetector group are both PIN silicon photodiodes. The first photodetector group and the second photodetector group each include at least two photodetectors. The photodetectors in the first photodetector group and the second photodetector group are respectively arrayed on both sides of the photosensitive area, and the normal of the photosensitive surface of each photodetector points to the photosensitive area. The number of photodetectors in the first photodetector group and the second photodetector group are the same and their positions correspond one-to-one to form a symmetrical scattered light receiving structure.

[0008] Secondly, the present invention provides a particle monitoring method based on the aforementioned semiconductor laser particle counting sensor, comprising the following steps: The scattered signal set output by each photodetector group is collected synchronously, and the scattered signal set includes the scattered signal intensity output by each detector in the corresponding photodetector group; The intensity of each scattered signal in the scattered signal set is monitored in real time. When the intensity of any scattered signal exceeds a preset threshold, it is determined that a particle has entered the photosensitive area, and the start time and duration of the particle event are recorded. Within the time window, the peak intensity of each detector in the two sets of scattered signals is extracted and used to construct a first intensity vector and a second intensity vector, respectively. The first intensity vector and the second intensity vector are then merged into a joint intensity vector. Based on the joint intensity vector and the spatial coordinates of each detector, the three-dimensional spatial coordinates of the particle in the photosensitive area are calculated using a pre-established spatial positioning model. At the same time, the spatial coordinate sequence of the particle is obtained by calculating the coordinates of the particle at multiple consecutive sampling times within the time window. Based on the spatial coordinate sequence, the motion trajectory of the particle is fitted, and the velocity vector of the particle is obtained from the motion trajectory. The velocity vector contains the direction and speed of the particle's motion. Based on at least one intensity value in the joint intensity vector, the intensity value is corrected by position compensation in combination with the solved spatial coordinates, and then the particle size is calculated using the corrected intensity value. Output the spatial coordinates, velocity vector, and particle size information of the particles in the photosensitive region.

[0009] In one embodiment, the intensity of each scattered signal in the real-time monitoring scattered signal set is determined to indicate that a particle has entered the photosensitive area when the intensity of any scattered signal exceeds a preset threshold. Specifically, this includes: Continuous monitoring of the scattered signal intensity of all photodetectors; When the signal strength of any photodetector exceeds the preset trigger threshold multiple times consecutively, the start time of the event is recorded. A valid particle event is confirmed when the signal strength of at least one detector in each of the two photodetector groups simultaneously exceeds the trigger threshold. Otherwise, it is judged as an interference signal and ignored.

[0010] In one embodiment, the step of extracting the peak intensities of each detector in the two sets of scattered signals and constructing a first intensity vector and a second intensity vector respectively includes: Within the time window, a local peak search is performed on the scattered signal intensity sequence of each photodetector to obtain the maximum intensity value and occurrence time of each detector within the time window; Using the peak time of the detector with the earliest rising edge as a reference, the intensity sequences of other detectors are time-aligned to obtain temporally consistent intensity values ​​of each detector. All aligned peak intensities are arranged in the order of the detectors to form the first intensity vector and the second intensity vector, respectively.

[0011] In one embodiment, the step of calculating the three-dimensional spatial coordinates of the particle within the photosensitive region based on the joint intensity vector and the spatial coordinates of each detector using a pre-established spatial positioning model specifically includes: The intensity values ​​of each component in the joint intensity vector are used as weights to perform a weighted average of the spatial coordinates of each detector, resulting in the three-dimensional spatial coordinates of the particle. For detectors whose intensity values ​​are lower than a certain proportion of the maximum intensity value, the weights are reset to zero. Calculate the spatial coordinate sequence for each sampling time within the time window.

[0012] In one embodiment, the step of fitting a particle's trajectory based on a spatial coordinate sequence and obtaining the particle's velocity vector based on the trajectory specifically includes: Outliers in the spatial coordinate sequence are removed and replaced by interpolation. The processed coordinate sequence is linearly fitted using the least squares method to obtain the fitted line. The direction of the fitted straight line is taken as the direction of particle motion, and the slope modulus of the fitted straight line is taken as the particle's velocity, thus obtaining the velocity vector.

[0013] In one embodiment, the step of performing position compensation correction on the intensity value based on at least one intensity value in the joint intensity vector and the calculated spatial coordinates, and then using the corrected intensity value to calculate the particle size, specifically includes: The detector with the largest intensity value in the joint intensity vector is selected as the main detector, and the scattering angle and solid angle of the particle relative to the main detector are calculated based on the solved spatial coordinates. The equivalent center intensity is obtained by querying the pre-stored correction factor table and dividing the original intensity value by the correction factor. The correction factor table is used to record the intensity correction factor under different scattering angles and solid angles. Substituting the equivalent center strength into the particle size-strength calibration curve, the particle size is obtained.

[0014] Thirdly, the present invention provides a particle monitoring system, including the aforementioned semiconductor laser particle counter and a data processing unit electrically connected to the semiconductor laser particle counting sensor. The data processing unit is configured to synchronously acquire scattering signals output by two sets of photodetector groups, detect particle events in real time, calculate the three-dimensional spatial coordinates, velocity vector and particle size of the particles, and output particle monitoring results.

[0015] The semiconductor laser particle counting sensor, particle monitoring method, and system of the present invention have the following advantages over the prior art: 1. By setting up a first photodetector group and a second photodetector group opposite each other on both sides of the photosensitive area along a first direction perpendicular to the particle motion direction and the beam propagation direction, the particle passes between the two groups of detectors. The intensity distribution of the scattered signal output by the two groups of detectors is acquired synchronously by the signal processing module. The three-dimensional spatial coordinates of the particle are directly calculated by combining the spatial coordinates of each detector. This method does not require any focusing or imaging optical elements, which greatly reduces the material cost and assembly complexity of the sensor. At the same time, it avoids stray light noise caused by concave mirrors, improves the detection signal-to-noise ratio of small-diameter particles, and achieves quantitative acquisition of the spatial coordinates of the particle without an imaging optical system, which provides a basis for position compensation in subsequent particle size measurement. 2. Based on the acquisition of spatial coordinates, by fitting the spatial coordinates of the particles at multiple consecutive sampling moments during the process of the particles passing through the photosensitive area, the motion direction and velocity vector of the particles can be output simultaneously, realizing a full-dimensional characterization of the motion state of a single particle. This fills the information gap that traditional particle counters can only output particle size and count. In addition, the calculated spatial coordinates are used to perform position compensation correction on the scattered light intensity of the detector, eliminating the influence of particle position on the scattered light intensity and significantly improving the consistency and accuracy of particle size measurement. Attached Figure Description

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

[0017] Figure 1This is a perspective view of the semiconductor laser particle counting sensor of the present invention; Figure 2 This is a side view of the semiconductor laser particle counting sensor of the present invention; Figure 3 This is a side cross-sectional view of the semiconductor laser particle counting sensor of the present invention; Figure 4 This is another cross-sectional view of the semiconductor laser particle counting sensor of the present invention; Figure 5 This is a schematic flowchart of the particle monitoring method of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this 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 this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0019] like Figure 1-4 As shown, the semiconductor laser particle counting sensor of the present invention includes a housing 1, a laser source 2, a first photodetector group 3, a second photodetector group 4, and a signal processing module.

[0020] A counting cavity 101 is provided inside the housing 1. The counting cavity 101 has an inlet and an outlet for gas to flow in and out. A photosensitive area for particle monitoring is formed in the central region of the counting cavity 101. This photosensitive area is located at the intersection of the beam emitted by the laser source 2 and the particle gas flow. In this embodiment, the shape of the counting cavity 101 can be, but is not limited to, a cuboid or a cylinder. Its inner wall is preferably coated with a light-absorbing material or blackened to reduce stray light reflection.

[0021] The laser source 2 is fixedly mounted on the housing 1, and its light emission direction is directly facing the photosensitive area in the counting cavity 101. The laser source 2 can be a semiconductor laser diode, such as a red laser diode with a wavelength of 650nm or 780nm. The beam emitted by the laser source 2 becomes a parallel beam after passing through a collimating lens. The cross-section of the parallel beam can be circular or rectangular. The intensity distribution of the beam in the photosensitive area is preferably uniform to ensure that the particles receive a consistent irradiation intensity when passing through different positions. In this embodiment, the propagation direction of the beam is defined as the Z-axis direction.

[0022] The expected direction of particle motion is determined by the airflow direction in the counting chamber 101, which is usually set as a straight line from the air inlet to the air outlet. In this embodiment, it is defined as the X-axis direction, that is, the particles pass through the photosensitive area from left to right.

[0023] The first photodetector group 3 is disposed on the housing 1 and located on the first side of the photosensitive area along the first direction. The first direction is perpendicular to both the expected direction of particle motion and the direction of light beam propagation, that is, perpendicular to the X-axis and Z-axis. Therefore, the first direction is the Y-axis direction. In this embodiment, the first side of the first direction can be the positive Y-axis side, such as the front side of the counting cavity 101, and the second side is the negative Y-axis side, the rear side of the counting cavity 101. The first photodetector group 3 includes multiple photodetectors. These photodetectors can be independent PIN silicon photodiodes or photodetector arrays integrated on the same substrate. The photosensitive surface of each detector faces the photosensitive area so as to directly receive the scattered light from the particles in the photosensitive area without passing through any concave mirror or imaging lens.

[0024] The second photodetector group 4 is disposed on the housing 1 and located on the second side of the photosensitive area along the first direction, that is, opposite to the first photodetector group 3. When a particle passes through the photosensitive area, it passes between the first photodetector group 3 and the second photodetector group 4. The second photodetector group 4 also contains multiple photodetectors, and its photosensitive surface also faces the photosensitive area. The relative positions of the first photodetector group 3 and the second photodetector group 4 in the Y-axis direction can be completely symmetrical, or they can be slightly offset according to the actual scattered light collection requirements, but the spatial coordinates of both are known and fixed.

[0025] The signal processing module is electrically connected to the first photodetector group 3 and the second photodetector group 4, respectively. This module synchronously acquires the first set of scattered signals output by the first photodetector group 3 and the second set of scattered signals output by the second photodetector group 4. Each set of scattered signals contains the intensity value of scattered light output by each photodetector in the corresponding group. Since the intensity of scattered light received by photodetectors at different spatial locations is closely related to the spatial location of the particle within the photosensitive area, and based on Mie scattering theory, the intensity of scattered light varies at different scattering angles, the signal processing module calculates the three-dimensional spatial coordinates (x, y, z) of the particle using a predetermined spatial positioning algorithm based on the intensity distribution of these two sets of scattered signals and the pre-stored spatial coordinates of each detector. Simultaneously, by detecting whether there are pulses in the scattered signals exceeding a preset threshold, the signal processing module can also count the number of particle events, thereby obtaining the particle count result within the current photosensitive area. In some embodiments, the signal processing module may be a circuit board containing a multi-channel preamplifier, an analog-to-digital converter, and an embedded microcontroller or DSP.

[0026] It should be noted that no concave mirrors, ellipsoidal mirrors, or imaging lenses are used in this embodiment to collect or focus scattered light. All photodetectors receive scattered light directly without imaging. This not only reduces the cost and assembly difficulty of the optical system, but also avoids the impact of stray mirror light on the measurement signal-to-noise ratio.

[0027] In some embodiments, a first circuit board 5 and a second circuit board 6 are provided for convenient installation and optical sealing of the photodetector group. Specifically, a first opening and a second opening are provided on the housing 1. These two openings are located on both sides of the counting cavity 101 along the first direction and are both connected to the inside of the counting cavity 101. The first photodetector group 3 is fixedly installed on the first circuit board 5. The first circuit board 5 is sealed and fixed to the housing 1 by a sealing gasket or adhesive and completely covers the first opening, so that the first photodetector group 3 is located exactly in the first opening, and the photosensitive surface of each photodetector is facing the photosensitive area inside the counting cavity 101.

[0028] Similarly, the second photodetector group 4 is fixedly mounted on the second circuit board 6, and the second circuit board 6 seals and covers the second opening, so that the second photodetector group 4 is located inside the second opening and the photosensitive surface faces the photosensitive area.

[0029] Conductive lines are also provided on the first circuit board 5 and the second circuit board 6 to lead the output signals of the first photodetector group 3 and the second photodetector group 4 to the signal processing module. This sealed mounting structure with an opening and circuit board ensures unobstructed light path between the photodetector and the photosensitive area, prevents external ambient light or dust from entering the counting chamber, and facilitates sensor assembly and maintenance.

[0030] In some embodiments, the device types and arrangements of the first photodetector group 3 and the second photodetector group 4 are designed. The photodetectors in the first photodetector group 3 and the second photodetector group 4 are all PIN silicon photodiodes. These devices have the advantages of fast response speed, low dark current and low cost, and are very suitable for the detection of scattered light in the visible to near-infrared band.

[0031] To ensure that the two-dimensional coordinates of the particle in the measurement plane can be uniquely determined, the first photodetector group 3 and the second photodetector group 4 each include at least two photodetectors. These photodetectors are arranged in an array on both sides of the photosensitive area, and the normal of the photosensitive surface of each detector points to the center of the photosensitive area, so as to ensure that each detector can effectively receive the scattered light from the photosensitive area.

[0032] In a specific configuration, the number of photodetectors in the first photodetector group 3 and the second photodetector group 4 are the same, and they are in a one-to-one correspondence in spatial position. For example, they are arranged symmetrically on both sides of the Y-axis in a ring array with the same angular interval, thus forming a symmetrical scattered light receiving structure. This symmetrical layout helps to eliminate positioning deviations caused by uneven detector distribution and improves the accuracy and consistency of spatial coordinate calculation.

[0033] like Figure 5 As shown, the particle monitoring method of the present invention is implemented based on the above-mentioned semiconductor laser particle counting sensor, and includes steps S100-S700.

[0034] S100: Synchronously acquire the set of scattered signals output by each photodetector group, wherein the set of scattered signals includes the intensity of the scattered signals output by each detector in the corresponding photodetector group.

[0035] The signal processing module synchronously acquires the output signals of all photodetectors in the first and second photodetector groups at a fixed sampling frequency. Each photodetector outputs an analog voltage or current signal, which is converted from analog to digital to obtain the corresponding digital intensity value. For the first photodetector group, the intensity values ​​of all its detectors are arranged in a predetermined order to form a first scattered signal set; similarly, the intensity values ​​of all detectors in the second photodetector group are arranged to form a second scattered signal set. Each element in the scattered signal set is associated one-to-one with the spatial coordinates of the corresponding photodetector.

[0036] S200: Real-time monitoring of the intensity of each scattering signal in the scattering signal set. When the intensity of any scattering signal exceeds a preset threshold, it is determined that a particle has entered the photosensitive area, and the start time and duration of the particle event are recorded.

[0037] The system monitors the intensity value of each signal in the first and second scattered signal sets in real time and compares each intensity value with a pre-set trigger threshold. When the intensity of the scattered signal from any photodetector exceeds the threshold multiple times consecutively, for example, three consecutive sampling points, it is determined as the start of a particle entering the photosensitive area, and the start time of the event is recorded. Simultaneously, to eliminate false triggers caused by unilateral noise or electrical interference, a valid particle event is only confirmed when the signal intensity of at least one detector in both the first and second photodetector sets exceeds the threshold within the same time window. The duration of this particle event is recorded as the time from the rising edge of the signal exceeding the threshold to the falling edge falling below the threshold. If only one side of the detector set has a signal while the other side remains silent, it is considered interference and ignored.

[0038] S300: Within the time window, extract the peak intensity of each detector in the two sets of scattered signals and construct the first intensity vector and the second intensity vector respectively. Then, merge the first intensity vector and the second intensity vector into a joint intensity vector.

[0039] For each confirmed valid particle event, peak search is performed on each photodetector in the first and second photodetector groups within its corresponding time window.

[0040] Specifically, the maximum intensity value output by each detector within the time window is identified as the peak intensity of that detector. Since there may be slight differences in the response time of each detector, the intensity sequences of other detectors are time-interpolated and aligned based on the earliest rising edge of the signal among all detectors, thereby obtaining the peak intensities of each detector that are consistent in time.

[0041] All aligned peak intensities are arranged in the order of the detectors to form the first intensity vector and the second intensity vector, respectively. Then, these two vectors are concatenated end to end to obtain a joint intensity vector, which contains the intensity distribution information of the particle scattered light in various directions in space.

[0042] S400: Based on the joint intensity vector and the spatial coordinates of each detector, the three-dimensional spatial coordinates of the particle in the photosensitive area are calculated using a pre-established spatial positioning model. At the same time, the spatial coordinate sequence of the particle is obtained by calculating the coordinates of multiple consecutive sampling times within the time window.

[0043] Using a pre-established spatial positioning model, the joint intensity vector obtained in step S300 is used as input. Combined with the known spatial coordinates of each detector in the first and second photodetector groups, the three-dimensional spatial coordinates (x, y, z) of the particle within the photosensitive area are calculated. This spatial positioning model can be a lookup table model based on calibration data, a weighted centroid model, or a neural network model, etc. Its core idea is to infer the particle position using the relative relationship of scattered light intensity in different directions. In addition, to obtain the particle's motion information, the above calculation is repeated for each consecutive sampling moment (or every few sampling points) within the time window of the particle event, thereby obtaining a set of spatial coordinate sequences arranged in chronological order, i.e., the discrete points of the particle's motion trajectory within the photosensitive area.

[0044] S500: Based on the spatial coordinate sequence, fit the motion trajectory of the particle, and obtain the velocity vector of the particle based on the motion trajectory. The velocity vector contains the direction and speed of the particle's motion.

[0045] Based on the spatial coordinate sequence obtained in step S400, trajectory fitting is performed on these discrete points. Since the particle's motion time within the photosensitive region is extremely short and the airflow direction is stable, it can generally be approximated as uniform linear motion. Therefore, the least squares method can be used to linearly fit the coordinate sequence, obtaining a spatial straight line. The direction of this fitted line is the particle's motion direction, and the slope modulus of the fitted line is the particle's velocity. Combining the direction and velocity yields the particle's velocity vector. If the coordinate sequence exhibits significant nonlinear characteristics, a second-order or higher-order polynomial fitting can also be used, and the instantaneous slope at the center point of the time window can be taken as the velocity vector.

[0046] S600: Based on at least one intensity value in the joint intensity vector, the intensity value is corrected by position compensation using the calculated spatial coordinates, and then the particle size is calculated using the corrected intensity value.

[0047] Since the actual position of a particle within the photosensitive region affects the intensity of scattered light received by each detector, even with the same particle size, particles located at the edge of the photosensitive region will produce different signal intensities than those located at the center. Directly using the original intensity value to calculate the particle size will introduce errors. Therefore, the intensity value is corrected for position using the calculated particle spatial coordinates.

[0048] Specifically, the detector with the highest signal-to-noise ratio (SNR), such as the detector with the largest intensity value, is selected from the joint intensity vector as the main detector. The scattering angle and solid angle of the particle relative to the main detector are calculated based on the particle's spatial coordinates. Then, a pre-stored correction factor table is consulted. This table records the ratio of theoretical intensity to the intensity at the center position under different scattering angles and solid angles. The original intensity value of the main detector is divided by the corresponding correction factor to obtain the equivalent scattering intensity when the particle is located at the center of the photosensitive region. This equivalent intensity is then substituted into a pre-calibrated particle size-intensity calibration curve. The particle size-intensity calibration curve is obtained by measuring the intensity of a standard particle of known size at the center position, and the optical particle size can be calculated through interpolation.

[0049] S700: Outputs the spatial coordinates, velocity vector, and particle size information of the particles in the photosensitive area.

[0050] The results obtained from the above steps are summarized, and the following information is output for each valid particle event: three-dimensional spatial coordinates (x, y, z), velocity vector, and particle size. Furthermore, by counting the number of valid particle events detected per unit time, particle concentration information can also be output. This multidimensional information can be transmitted in real time to a host computer or stored locally for subsequent applications such as aerosol analysis, flow field diagnosis, or pollution source localization.

[0051] In some embodiments, step S200 involves real-time monitoring of the intensity of each scattering signal in the scattering signal set. When the intensity of any scattering signal exceeds a preset threshold, it is determined that a particle has entered the photosensitive area. This can be specifically divided into sub-steps S201-S203.

[0052] S201: Continuously monitor the intensity of scattered signals from all photodetectors.

[0053] The signal processing module independently and continuously monitors the scattered signal intensity of each photodetector in the first and second photodetector groups in real time at a fixed sampling frequency, such as 2MHz. Data from each channel is stored in a circular buffer for subsequent analysis.

[0054] S202: When the signal strength of any photodetector exceeds the preset trigger threshold multiple times consecutively, record the start time of the event.

[0055] For each photodetector, the signal processing module compares the intensity value of its current sampling point with a preset trigger threshold Th. To eliminate false triggers caused by single noise spikes, this embodiment uses a criterion of multiple consecutive exceedances of the threshold. Only when the signal intensity of a detector is greater than Th at three consecutive sampling points, i.e., within three consecutive time intervals Δt, is it determined to be a particle entry candidate event, and the start time T of the event is recorded. start The time corresponding to the first sampling point that exceeds the threshold can be taken. This continuous judgment can be implemented by a simple counter. Each time the intensity is greater than Th, the counter is incremented by 1. Once it is less than Th, the counter is cleared to zero. When the counter reaches 3, the candidate event is triggered.

[0056] S203: When the signal strength of at least one detector in each of the two photodetector groups exceeds the trigger threshold simultaneously, it is confirmed as a valid particle event.

[0057] After a candidate event is triggered, further checks are conducted to determine whether, within the current time window, at least one detector in each of the first and second photodetector groups simultaneously exceeds the trigger threshold Th.

[0058] Specifically, the intensity data of the two sets of detectors are scanned separately. If at least one channel in the first set has a peak value exceeding Th, and at least one channel in the second set also has a peak value exceeding Th, then the event is confirmed as a valid particle event. Otherwise, it is determined to be interference signal caused by electrical noise or stray light from one side, ignored, and the candidate event record is cleared. The dual-set joint confirmation mechanism fully utilizes the geometric characteristics of the relative arrangement of the two sets of detectors. That is, when a real particle passes between the two sets of detectors, it will necessarily be detected by both sets of detectors simultaneously, while noise or interference usually only affects one side.

[0059] In some embodiments, step S300, which involves extracting the peak intensity of each detector in the two sets of scattered signals and constructing a first intensity vector and a second intensity vector, can be further divided into sub-steps S301-S303.

[0060] S301: Within the time window, perform a local peak search on the scattering signal intensity sequence of each photodetector to obtain the maximum intensity value and occurrence time of each detector within the time window.

[0061] For each confirmed valid particle event, within its recorded time window [T] start ,T end Within this time window, a local peak search is performed on the scattered signal intensity sequence of each photodetector. Specifically, for each detector, the maximum intensity I within that time window is found. max And record the precise time T when the maximum value occurs. peak To reduce the impact of noise, a simple moving average filter can be applied to the signal before the search. For channels with low signal-to-noise ratios, if the difference between the maximum and second-largest values ​​is less than 10% of the maximum value, the earliest peak value is taken as the representative.

[0062] S302: Using the peak time of the detector with the earliest rising edge of the signal as a reference, the intensity sequences of other detectors are time-aligned to obtain temporally consistent intensity values ​​of each detector.

[0063] Because particles may tilt within the photosensitive region, or different detectors may have different response delays, the peak time T of each detector varies. peak They are often not exactly the same. In order to obtain the scattering intensity distribution at the same spatial moment, this embodiment adopts a time alignment method based on the earliest rising edge. First, the detector with the earliest signal rising edge among all detectors is found, that is, its T peak The time when the intensity first exceeds the threshold is the smallest, or the earliest time when the intensity first exceeds the threshold, is denoted as T. ref Then, for each of the other detectors, using its intensity time series as data points, at T... ref Interpolation is performed at each time step to obtain the detector's value at T. ref Intensity value I' at time i The interpolation method can use the linear interpolation formula:

[0064]

[0065] Where T1 and T2 are T ref For detectors whose peak times deviate significantly between two adjacent sampling times, such as those deviating by more than 1 / 3 of the time window width, their weights can be reset to zero to avoid introducing excessive errors.

[0066] S303: Arrange all aligned peak intensities in the order of the detectors to form the first intensity vector and the second intensity vector respectively.

[0067] The intensity values ​​I' of each detector obtained after time alignment i Arranged according to a pre-defined detector numbering order, the first intensity vector V1=(I1',I2',...,I...) is formed for the first photodetector group (a total of M detectors). M For the second photodetector group, a total of N detectors form the second intensity vector V2=(I M+1 ',I M+2 ',...,I M+N Then, these two vectors are concatenated end to end to obtain the joint intensity vector V=(V1,V2). This joint intensity vector contains the information on the distribution of scattered light intensity received by the detectors at different angles on both sides when the particle passes through the photosensitive area. It is the direct input of the subsequent spatial positioning model.

[0068] In some embodiments, step S400, which calculates the three-dimensional spatial coordinates of the particle in the photosensitive area based on the joint intensity vector and the spatial coordinates of each detector using a pre-established spatial positioning model, can be specifically divided into sub-steps S401-S402.

[0069] S401: The intensity values ​​of each component in the joint intensity vector are used as weights to perform a weighted average of the spatial coordinates of each detector, resulting in the three-dimensional spatial coordinates of the particle. For detectors whose intensity values ​​are lower than a certain proportion of the maximum intensity value, the weights are reset to zero.

[0070] Let the joint strength vector be V=(I1,I2,...,I...). K ), where K is the total number of photodetectors in the first and second photodetector groups, K=M+N, and the spatial coordinates of each photodetector are (x... i ,y i ,z i (i=1~K), using the intensity values ​​of each detector as weights, a weighted average is calculated on the spatial coordinates of each detector to determine the three-dimensional spatial coordinates of the particle:

[0071] In order to reduce the positioning error of low signal-to-noise ratio channels during the calculation process, for detectors whose intensity value is lower than the maximum intensity value by a certain percentage, such as 5% of the maximum intensity value, their weight is directly set to zero, that is, they are not included in the weighted average. This percentage threshold can be preset according to the actual noise level.

[0072] S402: Calculate for each sampling time within the time window to obtain a continuous spatial coordinate sequence.

[0073] Within the time window of the particle event, the signal processing module repeatedly performs the above weighted centroid calculation at each sampling moment (or at fixed intervals of sampling points), thereby obtaining a set of spatial coordinates arranged in chronological order: (x1,y1,z1),(x2,y2,z2),...,(x L ,y L ,z L ), where L is the number of effective calculations within the time window, and this coordinate sequence reflects the continuous spatial position changes of the particle as it passes through the photosensitive region.

[0074] The weighted centroid method described above can quickly obtain the three-dimensional coordinates of particles without complex iterative optimization, making it suitable for real-time processing. In cases where the detector distribution is non-uniform or the light intensity distribution is not ideal, a pre-calibrated lookup table method or a neural network model can be used to replace the weighted centroid method. This embodiment does not impose any restrictions on this.

[0075] In some embodiments, step S500, which involves fitting a particle's motion trajectory based on a spatial coordinate sequence and obtaining the particle's velocity vector based on the motion trajectory, can be further divided into sub-steps S501-S503.

[0076] S501: Remove outliers from the spatial coordinate sequence and process them using interpolation.

[0077] Due to noise or transient interference, there may be individual outliers in the spatial coordinate sequence that significantly deviate from the true trajectory. The signal processing module first performs outlier detection on the coordinate sequence. For each coordinate point P... j =(xj,y j ,z j ), calculate the line connecting it to the two adjacent points before and after it, P j-1 To P j+1 If the vertical distance *d* between the two points is greater than a preset anomaly threshold (e.g., one-tenth of the feature size of the photosensitive area, such as 0.05 mm), then the point is considered an anomaly. For detected anomalies, linear interpolation between the two points is used as the replacement: P j ′=(P j-1 +P j+1 If an anomaly occurs at either end of the sequence, the nearest normal point is used to replace it.

[0078] S502: The processed coordinate sequence is linearly fitted using the least squares method to obtain the fitted straight line.

[0079] After removing outliers and interpolating, the processed coordinate sequence (x) is obtained. j ′,y j ′,z jSince the particle's motion time within the photosensitive region is extremely short, typically tens to hundreds of microseconds, and the airflow direction is stable, it can be approximated as uniform linear motion. Therefore, the least squares method is used to linearly fit the three-dimensional coordinates. Taking the x-coordinate as an example, the fitted straight line equation is x=a x t+b x Where t is time, the slope a is solved by minimizing the sum of squared residuals. x and intercept b x Similarly, we can obtain a y ,a z Then the direction vector of the fitted line is This direction is the direction of the particle's motion.

[0080] S503: The direction of the fitted straight line is taken as the direction of particle motion, and the slope modulus of the fitted straight line is taken as the velocity of the particle, thus obtaining the velocity vector.

[0081] slope modulus of the fitted line This is the particle's velocity. Combining direction and velocity yields the particle's velocity vector. If a more precise description of the velocity vector is required, the direction cosine and velocity values ​​can be directly output. For coordinate sequences with low linear correlation, such as a correlation coefficient less than 0.8, it indicates that the particles may be accelerating or undergoing curvilinear motion. In this case, a quadratic polynomial fitting can be used, and the instantaneous slope at the center point of the time window can be taken as the velocity vector.

[0082] In some embodiments, step S600 involves performing position compensation correction on the intensity value based on at least one intensity value in the joint intensity vector and the calculated spatial coordinates, and then using the corrected intensity value to calculate the particle size. This can be specifically divided into sub-steps S601-S604.

[0083] S601: Select the detector with the largest intensity value in the joint intensity vector as the main detector.

[0084] The signal processing module obtains the joint intensity vector V=(I1,I2,...,I... K The detector with the highest intensity value among the selected detectors is chosen as the master detector. The master detector is selected because it has the highest signal-to-noise ratio and is least affected by noise. The original intensity value I of this master detector is recorded. raw Spatial coordinates (x) d ,y d ,z d ) and the direction of the normal to its photosensitive surface.

[0085] S602: Calculate the scattering angle and solid angle of the particle relative to the main detector based on the solved spatial coordinates.

[0086] Based on the particle space coordinates (x) calculated in step S400 p ,y p ,z p To calculate the geometric relationship between the particle and the main detector, firstly, the vector from the particle to the main detector is: The scattering angle θ is defined as the angle between the vector and the direction of beam propagation, that is:

[0087] in, The solid angle Ω is determined by the effective photosensitive area A of the main detector and the distance from the particle to the detector. Approximate calculation: If the detector uses a non-circular photosensitive surface, a table showing the relationship between its solid angle and position can be stored in advance.

[0088] S603: Query the pre-stored correction factor table, divide the original intensity value by the correction factor to obtain the equivalent center intensity, the correction factor table is used to record the intensity correction factor under different scattering angles and solid angles.

[0089] Beforehand, under standard conditions, such as using a standard particle of known size placed at the center of the photosensitive region, a correction factor table is established. This table records the correction coefficient f(θ,Ω) for different combinations of scattering angles θ and solid angles Ω. It is defined as the ratio of the theoretical intensity received by the main detector when the particle is at the center of the photosensitive region to the intensity received when the particle is at its actual position. The signal processing module looks up the calculated θ and Ω in the table. If no exact matching point is found, bilinear interpolation is used to obtain the correction coefficient f. The equivalent center intensity is then:

[0090] I corr =I raw / f The equivalent central intensity eliminates the influence of particle position on the scattered light collection efficiency, and is equivalent to the intensity measured when the particle is moved to the center of the photosensitive region.

[0091] S604: Substitute the equivalent center strength into the particle size-strength calibration curve to obtain the particle size.

[0092] The equivalent center strength I corr The pre-calibrated particle size-intensity calibration curve is substituted into the data. This calibration curve is obtained by measuring the scattering intensity at the center of the photosensitive region using a series of standard particles with known sizes, such as 0.3 μm, 0.5 μm, 1.0 μm, 2.5 μm, and 5.0 μm, and then performing curve fitting, such as power function or polynomial fitting. The signal processing module finds I on the calibration curve. corr If the corresponding particle size value is between two calibration points, linear interpolation or spline interpolation is used to output the optical particle size of the particle.

[0093] If multiple detectors in the joint intensity vector have high signal-to-noise ratios, the particle size can be calculated using each detector as the main detector, and then the multiple results can be weighted and averaged to further improve the accuracy and stability of particle size measurement.

[0094] The above-mentioned position compensation correction can effectively solve the particle size measurement error caused by the random position of particles passing through the photosensitive area in traditional single-detector particle counters, and significantly improve the consistency of particle size measurement.

[0095] The particle monitoring system of the present invention includes the aforementioned semiconductor laser particle counter and a data processing unit electrically connected to the semiconductor laser particle counting sensor. The data processing unit is configured to synchronously acquire the scattering signals output by two sets of photodetectors, detect particle events in real time, calculate the three-dimensional spatial coordinates, velocity vector and particle size of the particles, and output the particle monitoring results.

[0096] It should be noted that, for the sake of simplicity, the foregoing method embodiments are all described as a series of actions. However, those skilled in the art should understand that this application is not limited to the described order of actions, as some steps may be performed in other orders or simultaneously according to this application. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to this application.

[0097] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0098] In the several embodiments provided in this application, it should be understood that the disclosed apparatus 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 shown or discussed mutual couplings or direct couplings or communication connections may be through some service interfaces; indirect couplings or communication connections between apparatuses or units may be electrical or other forms.

[0099] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0100] 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 as a software functional unit.

[0101] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage device (CMD). Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a memory and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of this application. The aforementioned memory includes various media capable of storing program code, such as USB flash drives, portable hard drives, magnetic disks, or optical disks.

[0102] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A semiconductor laser particle counting sensor, characterized in that, It includes a housing (1), a laser source (2), a first photodetector group (3), a second photodetector group (4), and a signal processing module, wherein, A counting chamber (101) is provided inside the housing (1), and a photosensitive area for particle monitoring is formed inside the counting chamber (101); A laser source (2) is mounted on the housing (1) to generate a beam of light that irradiates the photosensitive area; The first photodetector group (3) is disposed on the housing (1) and located on the first side of the photosensitive area along the first direction, which is perpendicular to the expected direction of particle movement and perpendicular to the direction of beam propagation. The second photodetector group (4) is disposed on the housing (1) and located on the second side of the photosensitive area along the first direction. The first side and the second side are arranged opposite to each other, so that when a particle passes through the photosensitive area, it passes between the first photodetector group and the second photodetector group. The signal processing module is electrically connected to the first photodetector group (3) and the second photodetector group (4) to synchronously acquire the first scattering signal set output by the first photodetector group (3) and the second scattering signal set output by the second photodetector group (4). Based on the intensity distribution of the first scattering signal set and the second scattering signal set, combined with the spatial coordinates of each detector in the first photodetector group (3) and the second photodetector group (4), the number of particles and spatial coordinates of the current photosensitive area are obtained.

2. The semiconductor laser particle counting sensor as described in claim 1, characterized in that, It also includes a first circuit board (5) and a second circuit board (6), wherein, The housing (1) is provided with a first opening and a second opening, which are located on both sides of the counting cavity (101) along the first direction and are connected to the counting cavity (101); The first photodetector group (3) is fixed on the first circuit board (5). The first circuit board (5) is sealed on the housing (1) and covers the first opening, so that the first photodetector group (3) is located in the first opening and the photosensitive surface of each photodetector faces the photosensitive area. The second photodetector group (4) is fixed on the second circuit board (6). The second circuit board (6) is sealed on the housing (1) and covers the second opening, so that the second photodetector group (4) is located inside the second opening and the photosensitive surface of each photodetector faces the photosensitive area. The first circuit board (5) and the second circuit board (6) are used to lead the output signals of the first photodetector group (3) and the second photodetector group (4) to the signal processing module.

3. The semiconductor laser particle counting sensor as described in claim 2, characterized in that, The photodetectors in the first photodetector group (3) and the second photodetector group (4) are all PIN silicon photodiodes. The first photodetector group (3) and the second photodetector group (4) each include at least two photodetectors. The photodetectors in the first photodetector group (3) and the second photodetector group (4) are arranged in arrays on both sides of the photosensitive area, and the normal of the photosensitive surface of each photodetector points to the photosensitive area. The number of photodetectors in the first photodetector group (3) and the second photodetector group (4) are the same and their positions correspond one-to-one to form a symmetrical scattered light receiving structure.

4. A particle monitoring method, characterized in that, The semiconductor laser particle counting sensor based on any one of claims 1-3 is implemented by comprising the following steps: The scattered signal set output by each photodetector group is collected synchronously, and the scattered signal set includes the scattered signal intensity output by each detector in the corresponding photodetector group; The intensity of each scattered signal in the scattered signal set is monitored in real time. When the intensity of any scattered signal exceeds a preset threshold, it is determined that a particle has entered the photosensitive area, and the start time and duration of the particle event are recorded. Within the time window, the peak intensity of each detector in the two sets of scattered signals is extracted and used to construct a first intensity vector and a second intensity vector, respectively. The first intensity vector and the second intensity vector are then merged into a joint intensity vector. Based on the joint intensity vector and the spatial coordinates of each detector, the three-dimensional spatial coordinates of the particle in the photosensitive area are calculated using a pre-established spatial positioning model. At the same time, the spatial coordinate sequence of the particle is obtained by calculating the coordinates of the particle at multiple consecutive sampling times within the time window. Based on the spatial coordinate sequence, the motion trajectory of the particle is fitted, and the velocity vector of the particle is obtained from the motion trajectory. The velocity vector contains the direction and speed of the particle's motion. Based on at least one intensity value in the joint intensity vector, the intensity value is corrected by position compensation in combination with the solved spatial coordinates, and then the particle size is calculated using the corrected intensity value. Output the spatial coordinates, velocity vector, and particle size information of the particles in the photosensitive region.

5. The particle monitoring method as described in claim 4, characterized in that, The intensity of each scattered signal in the real-time monitoring scattered signal set is determined to indicate the presence of a particle entering the photosensitive area when the intensity of any scattered signal exceeds a preset threshold. Specifically, this includes: Continuous monitoring of the scattered signal intensity of all photodetectors; When the signal strength of any photodetector exceeds the preset trigger threshold multiple times consecutively, the start time of the event is recorded. A valid particle event is confirmed when the signal strength of at least one detector in each of the two photodetector groups simultaneously exceeds the trigger threshold. Otherwise, it is judged as an interference signal and ignored.

6. The particle monitoring method as described in claim 4, characterized in that, The step of extracting the peak intensity of each detector in the two sets of scattered signals and constructing a first intensity vector and a second intensity vector respectively includes: Within the time window, a local peak search is performed on the scattered signal intensity sequence of each photodetector to obtain the maximum intensity value and occurrence time of each detector within the time window; Using the peak time of the detector with the earliest rising edge as a reference, the intensity sequences of other detectors are time-aligned to obtain temporally consistent intensity values ​​of each detector. All aligned peak intensities are arranged in the order of the detectors to form the first intensity vector and the second intensity vector, respectively.

7. The particle monitoring method as described in claim 4, characterized in that, The step of calculating the three-dimensional spatial coordinates of the particle within the photosensitive area based on the joint intensity vector and the spatial coordinates of each detector, using a pre-established spatial positioning model, specifically includes: The intensity values ​​of each component in the joint intensity vector are used as weights to perform a weighted average of the spatial coordinates of each detector, resulting in the three-dimensional spatial coordinates of the particle. For detectors whose intensity values ​​are lower than a certain proportion of the maximum intensity value, the weights are reset to zero. Calculate the spatial coordinate sequence for each sampling time within the time window.

8. The particle monitoring method as described in claim 4, characterized in that, The process of fitting the particle's trajectory based on the spatial coordinate sequence and obtaining the particle's velocity vector from the trajectory specifically includes: Outliers in the spatial coordinate sequence are removed and replaced by interpolation. The processed coordinate sequence is linearly fitted using the least squares method to obtain the fitted line. The direction of the fitted straight line is taken as the direction of particle motion, and the slope modulus of the fitted straight line is taken as the particle's velocity, thus obtaining the velocity vector.

9. The particle monitoring method as described in claim 4, characterized in that, The step of calculating the particle size using at least one intensity value from the joint intensity vector, combined with the solved spatial coordinates, to perform position compensation correction on that intensity value, and then using the corrected intensity value, specifically includes: The detector with the largest intensity value in the joint intensity vector is selected as the main detector, and the scattering angle and solid angle of the particle relative to the main detector are calculated based on the solved spatial coordinates. The equivalent center intensity is obtained by querying the pre-stored correction factor table and dividing the original intensity value by the correction factor. The correction factor table is used to record the intensity correction factor under different scattering angles and solid angles. Substituting the equivalent center strength into the particle size-strength calibration curve, the particle size is obtained.

10. A particle monitoring system, characterized in that, The invention includes a semiconductor laser particle counter as described in any one of claims 1-3, and a data processing unit electrically connected to the semiconductor laser particle counting sensor. The data processing unit is configured to synchronously acquire scattering signals output from two sets of photodetectors, detect particle events in real time, calculate the three-dimensional spatial coordinates, velocity vector, and particle size of the particles, and output particle monitoring results.

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