Particle analysis method, device, storage medium and electronic device based on particle size spectrum

Abstract

The present invention relates to a particle analysis method, device, storage medium, and electronic device based on particle size spectrum, comprising: a beam generating and shaping unit, a light source monitoring unit, a stray light filtering unit, an isolation unit, a sample chamber, an APD, a PMT, and an operation unit. The beam generating and shaping unit excites collimated light, which, after light splitting, produces a laser beam output to the light source monitoring unit for detection and a laser beam output to the stray light filtering unit; the stray light filtering unit forms equally spaced parallel beams, which are output to the sample chamber through the isolation unit; when a sample falls to the focus of the light, the sample chamber inputs the lateral diffusely reflected beam to the APD for detection and the forward diffusely reflected beam to the PMT for detection; the operation unit receives detection information from the light source monitoring unit, the APD, and the PMT, and performs coherent operation; and determines information for particle analysis based on the signal-to-noise ratio of the information after the coherent operation. This can improve analysis efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of kinetic particle size analysis, and in particular to a particle analysis method, device, storage medium and electronic equipment based on particle size spectrum. Background Art

[0002] A kinetic particle size spectrometer (particle size spectrometer) is a device based on fluid dynamics and polarization optics for statistical analysis of different kinetic particle sizes. It can analyze the size and concentration of particles of different sizes in a sample in real time and is widely used in environmental monitoring, pharmaceutical production and research and development, gaseous particulate matter analysis, liquid particulate matter detection, advanced manufacturing, and dust-free analysis. Using a kinetic particle size spectrometer to measure particle size and concentration can be used to assess the condition of the sample. For example, in the environmental protection field, a kinetic particle size spectrometer monitors the size and concentration of particles in the atmosphere (the sample to be tested) to determine the degree of contamination. Pharmaceutical companies determine the quality of a drug (the sample to be tested) by determining the size and concentration of particles after atomization. And in high-end manufacturing fields such as semiconductors, the cleanliness of a workshop can be assessed by measuring the concentration and size of particles in the air (the sample to be tested).

[0003] The following is a brief introduction to the related kinetic particle size spectrometers for measuring particle concentration in the prior art.

[0004] The first method uses a particle size spectrum based on membrane weighing. This method uses a filter membrane with multiple preset pore sizes as a filter screen placed in the test environment. The weight-based volume of particles remaining on the membrane over a certain period of time is measured. Based on the pore size, the volume of a single particle corresponding to that pore size is obtained. The concentration of the particles is then calculated based on the volume of the large particle and the measured weight-based volume. This method has the advantage of low cost; the disadvantage is high error and the need for manual intervention.

[0005] The second method is particle size spectroscopy based on the extinction method. This method is a particle concentration measurement method based on the Lambert-Beer law. By measuring the absorption intensity of light by particles and combining it with filtering, it can detect the concentration of particles within a certain size range. Its advantage is automated measurement; its disadvantage is susceptibility to interference.

[0006] The third type is particle size spectroscopy based on light scattering. Its fundamental principle is Mie scattering theory. Light irradiated by particles is absorbed and scattered. The intensity of the scattered light is related to the particle size, concentration, wavelength of the incident light, and the scattering angle. Therefore, the scattered light intensity can be used to calculate parameters such as particle concentration and size distribution. This method offers the advantages of automated measurement and high accuracy; however, it is susceptible to interference.

[0007] The fourth method uses beta-ray absorption to measure particle size. Beta rays are absorbed as they pass through particles. When the energy of the emitted rays is constant, the absorbed energy is proportional to the mass of the particle. This allows for concentration measurement of particles within a certain size range when combined with a filter membrane with a certain pore size. This method offers the advantage of high measurement accuracy; however, it requires regular filter membrane replacement, which can be time-consuming.

[0008] The fifth type is a particle size spectrum based on the oscillating balance method. Its core principle is the correspondence between the mass of the oscillating end and the oscillation frequency. When the mass of the oscillating end changes, its oscillation frequency also changes. This change measures the mass of the oscillating end. A vacuum pump is used to draw the gas to be tested into a replaceable filter membrane installed at the oscillating end. The mass concentration of the particulate matter is corrected based on the flow rate of the test gas passing through per unit time, the temperature of the test gas, and the pressure of the test gas. Its advantages are high measurement accuracy and good real-time performance; its disadvantages are high maintenance frequency and susceptibility to interference.

[0009] The sixth type is charge-based particle size spectroscopy. The measurement principle is that when particles flow near the probe, electrostatic induction generates a certain amount of charge. The amount of charge is proportional to the number of particles. By measuring the amount of charge, the particle concentration can be obtained. Its advantages are high accuracy, high timeliness, and stability and reliability. However, its disadvantages are susceptibility to interference and the fact that it can only measure charged particles.

[0010] There are mainly the following types of equipment for measuring particle size.

[0011] The first type is particle size profiling based on scanning electromigration. Scanning electromigration technology measures the electrical charge of particles. The instrument uses a vacuum pump to draw particles into an internal particle impactor, which generates an electrical charge. Generally, the larger the particle diameter, the greater the charge. These charged particles are drawn into a measurement area with a narrow slit (typically consisting of inner and outer concentric circles). By controlling the voltage across the slit to manipulate the electric field, varying the electric field allows for the selection of particles of varying sizes. Its advantages are fast measurement speed and high resolution; its disadvantages are its inability to measure uncharged particles and its inability to measure particles 1μm or smaller.

[0012] The second method is particle size analysis based on laser diffraction scattering. This method, based on Furanhofer diffraction and Mie scattering theory, states that when incident light strikes particles, a diffraction effect occurs. Larger particles produce smaller scattered light angles, while smaller particles produce larger scattered light angles. Therefore, the size of the diffraction spot can be used to measure particle size. Its advantage is that the measurement results are unaffected by factors such as temperature, medium viscosity, particle density, and surface properties. Its disadvantages include high cost, complex equipment, and susceptibility to vibration.

[0013] The third type is an aerodynamic particle size spectrum. Particles of different diameters are generated at different speeds by a gas jet at a certain velocity. When particles of different speeds pass through a measurement area composed of parallel light beams with gaps between them, they are illuminated by the parallel light beams. The longer the particle travels through the parallel light beams, the wider the peak intervals between the light scattering peaks detected by the detector. This time interval between the peaks can be used to determine the particle's aerodynamic diameter. Its advantages are high reliability, real-time performance, and high accuracy. Its disadvantage is insufficient sensitivity for measuring small particles.

[0014] As can be seen from the above, the aerodynamic-based particle size spectrometer has the characteristics of high reliability, high real-time performance and high precision. However, due to its designed optical structure, its recognition sensitivity for particles with a size below 1 μm is low, and its measurement efficiency is low when used for particle size measurement, thus limiting its further application. Summary of the Invention

[0015] In view of this, the present invention provides a particle analysis method, device, storage medium and electronic device based on particle size spectrum.

[0016] Specifically, the present invention is achieved through the following technical solutions:

[0017] According to a first aspect of the present invention, a particle analysis device based on particle size spectrum is provided, the particle analysis device based on particle size spectrum comprising:

[0018] Beam forming and shaping unit, light source monitoring unit, stray light filtering unit, isolation unit, sample chamber, avalanche photodiode detector, photomultiplier tube detector and computing unit, among which,

[0019] a beam generating and shaping unit, configured to excite a first linearly polarized light of the collimated light, adjust the polarization state of the first linearly polarized light into a second linearly polarized light having the same energy as the horizontal component and the vertical component, expand the second linearly polarized light, and then split the light according to a preset splitting ratio to obtain a first laser beam and a second laser beam, output the first laser beam to a light source monitoring unit, and converge the second laser beam to form a converged beam and output it to a stray light filtering unit, wherein the laser energy of the first laser beam is less than the laser energy of the second laser beam;

[0020] a light source monitoring unit, configured to detect first light intensity information of the first laser beam, obtain first voltage information after conversion, and output the first voltage information to the calculation unit;

[0021] A stray light filtering unit is used to split the converged light beam to form two parallel light beams along the X axis with equal spacing along the Y axis at the light focus in the sample chamber, filter out stray light from the parallel light beams, and output the parallel light beams after the stray light is filtered into the sample chamber through the isolation unit;

[0022] An isolation unit, comprising a first window mirror and a second window mirror, wherein the first window mirror is connected to the aperture and is used to isolate the sample chamber from the beam generating and shaping unit, or the sample chamber from the stray light filtering unit, so as to prevent the gas to be detected with particulate matter in the sample chamber from contaminating the optical path environment of the beam generating and shaping unit and the stray light filtering unit, and the second window mirror is used to isolate the sample chamber from the avalanche photodiode detector, and the sample chamber from the photomultiplier tube detector, respectively;

[0023] The sample chamber is used to input the sample to be tested. When the sample to be tested falls to the focus of the two parallel light beams, it is illuminated by the two parallel light beams and diffusely reflected by the particles contained in the sample to be tested. The side diffusely reflected light beams are converged and input to the avalanche photodiode detector, and the forward diffusely reflected light beams are converged and input to the photomultiplier tube detector.

[0024] an avalanche photodiode detector, configured to detect second light intensity information of the lateral diffusely reflected light beam, obtain second voltage information after transformation, and output the second voltage information to the calculation unit;

[0025] a photomultiplier tube detector, used for detecting third light intensity information of the forward diffusely reflected light beam, obtaining third voltage information after transformation, and outputting the third voltage information to the calculation unit;

[0026] an operation unit for receiving the first light intensity information, the second light intensity information, and the third light intensity information, and performing a coherent operation on the first light intensity information and the second light intensity information according to a preset coherent algorithm to obtain effective information detected by the APD, and performing a coherent operation on the first light intensity information and the third light intensity information to obtain effective information detected by the PMT;

[0027] According to the signal-to-noise ratio of the effective information detected by the APD, it is determined whether the effective information detected by the APD or the effective information detected by the PMT is used for particle analysis. The particle analysis includes: particle concentration corresponding to the particle size distribution.

[0028] According to a second aspect of the present invention, a particle analysis method based on a particle size spectrum is provided, which is applied to the above-mentioned particle analysis device. The particle analysis method based on a particle size spectrum includes:

[0029] Turning on the particle analyzer, introducing zero gas after self-testing, obtaining an optimal APD coefficient based on first light intensity information from the light source monitoring unit and second light intensity information from the avalanche photodiode detector, and obtaining an optimal PMT coefficient based on the first light intensity information from the light source monitoring unit and third light intensity information from the photomultiplier tube detector;

[0030] Passing the sample gas, obtaining a first light-scattering APD based on first light intensity information of the light source monitoring unit, second light intensity information of the avalanche photodiode detector, and an optimal APD coefficient, and obtaining a second light-scattering APD based on the first light intensity information of the light source monitoring unit, third light intensity information of the photomultiplier tube detector, and an optimal PMT coefficient;

[0031] Calculating the signal-to-noise ratio of the first light-scattering APD and the signal-to-noise ratio of the second light-scattering APD based on a preset signal-to-noise ratio calculation formula;

[0032] Based on the signal-to-noise ratio of the first light-scattering APD, the signal-to-noise ratio of the second light-scattering APD, and a preset signal-to-noise ratio threshold, a light-scattering APD for particle analysis is determined from the first light-scattering APD and the second light-scattering APD.

[0033] According to a third aspect of the present invention, there is provided a storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the particle analysis method based on particle size spectrum in any possible implementation of the first aspect.

[0034] According to a fourth aspect of the present invention, there is provided an electronic device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the steps of the particle analysis method based on particle size spectrum in any possible implementation of the first aspect are implemented. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or related technical descriptions. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0037] Figure 1 A schematic structural diagram of a particle analysis device based on particle size spectrum provided by an embodiment of the present invention;

[0038] Figure 2 A schematic diagram of the aperture structure provided by an embodiment of the present invention;

[0039] Figure 3 A schematic diagram of the main structure of the sample chamber provided in an embodiment of the present invention;

[0040] Figure 4 A schematic side view of the sample chamber structure provided in an embodiment of the present invention;

[0041] Figure 5 Another schematic diagram of the main structure of the sample chamber provided by an embodiment of the present invention;

[0042] Figure 6 A schematic diagram of the aerodynamic gas nozzle structure provided by an embodiment of the present invention;

[0043] Figure 7 A schematic diagram of calculating the Brewster angle provided by an embodiment of the present invention;

[0044] Figure 8 A schematic diagram of the particle analysis principle provided by an embodiment of the present invention;

[0045] Figure 9 A schematic flow chart of a particle analysis method based on particle size spectrum provided in an embodiment of the present invention;

[0046] Figure 10 Another schematic flow chart of a particle analysis method based on particle size spectrum provided by an embodiment of the present invention;

[0047] Figure 11 A schematic diagram of another process of a particle analysis method based on particle size spectrum provided by an embodiment of the present invention;

[0048] Figure 12 A schematic structural diagram of an electronic device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0049] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0050] In the prior art, the sensitivity of an aerodynamic particle size spectrometer primarily depends on two factors. First, the sensitivity of the photodetector—its ability to detect the faint scattered light from micron-sized particles. Because aerodynamic particle size spectrometers utilize avalanche photodiodes (APDs), which have a high internal photocurrent gain, they offer a higher gain than photodiodes (PDs). However, this gain still falls short of photon-level detection, hindering efficient detection of submicron-sized particles. Second, the signal-to-noise ratio (SNR) of the entire optical system. High noise levels can drown out the light scattered by small particles, while the sample chamber-level light source of an aerodynamic particle size spectrometer utilizes conventional stray light extinction devices, resulting in a high background light that drowns out the scattered light from small particles and prevents detection of tiny particles. Current kinetic particle size spectrometers utilize APD photodetectors only on the side of the light beam. Under a certain voltage, they can amplify photoelectrons generated by surface materials, achieving a magnification of approximately 100x, and are typically used for weak-light detection and analysis. However, due to its limited gain and relatively high noise, it is still unable to detect the size and concentration of particles below 1 μm, and its sensitivity for detecting small particles in the Rayleigh scattering range is insufficient. Therefore, it cannot be used in fields requiring smaller particle size, resulting in low measurement efficiency of particle size spectrometers.

[0051] According to the Mie scattering theory and Rayleigh scattering theory in light scattering, when particles of different speeds pass through a measurement area composed of parallel light with a fixed gap, a scattering effect will be produced on the parallel light. Among them, if the particle size and the wavelength of the light are close, the Mie scattering effect will occur, and the forward scattered light energy will be majority, followed by the side, and the backward scattering will be the least; when the particle size is much smaller than the wavelength of the light, the Rayleigh scattering effect will occur, and the forward and backward scattered light energy will be majority, and the side scattered light will be the least; when the particle size is much larger than the wavelength of the light, it tends to the scattering in geometric optics, and the forward scattered light will be majority.

[0052] In this embodiment, based on the Mie scattering theory and Rayleigh scattering theory in light scattering, a particle size acquisition and analysis method based on an improved optical structure particle size spectrum is provided, which can solve the problem of low sensitivity in detecting particles below 1um in the kinetic particle size spectrometer based on related technologies, and help to quickly distinguish the size and concentration of finer particles, thereby meeting high-end application scenarios of quickly measuring the particle size and concentration of smaller particles, effectively expanding the application field of kinetic particle size spectrometers, while improving the accuracy and speed of particle size measurement, reducing the cost in the field of particle size measurement, and improving the measurement efficiency of particle size spectrometers. Specifically,

[0053] (1) The surface material of the PMT photomultiplier tube can generate photoelectrons by utilizing the photoelectric effect, and the multi-stage high-voltage circuit can multiply and amplify the photoelectrons. For example, a general 10-stage photomultiplier tube can internally achieve 1024 (2^10) times amplification, and due to its special structural characteristics, its noise is also low. If combined with a low-noise analog amplifier circuit, it can achieve a higher magnification gain, making PMT widely used in photon-level signal detection, such as in the fields of medicine, nuclear energy, space exploration, etc. Therefore, in this embodiment, a particle size spectrometer based on two detectors, avalanche photodiode (APD) and photomultiplier tube (PMT), is used to detect the scattered light intensity and flight time of particles of different sizes respectively. Among them, the relatively low-sensitivity APD is used to measure the scattered light intensity of particles above the micron level passing through the optical system of the particle size spectrometer, and the size and concentration of the corresponding particles are analyzed based on the measured scattered light intensity; the PMT with single-photon sensitivity is used to measure the scattered light intensity of particles below the micron level passing through the optical system, and then analyze their size and concentration. Specifically, this embodiment, based on the Mie and Rayleigh scattering principles, adds a forward-scattering single-photon PMT detector to the aerodynamic particle size spectrometer. This detector detects forward-scattered light from particles smaller than micrometers. This compensates for the limited sensitivity of the APD photoelectric sensor in existing aerodynamic particle size spectrometers to the extremely weak side-scattered light signals from small particles. In this embodiment, the PMT detector is mounted at the end of the detection chamber in the direction of laser emission.

[0054] (2) By designing a laser light source status monitoring function for the particle size spectrometer, the light source noise caused by changes in temperature and electromagnetic environment can be monitored in real time. In this way, the output results of the APD at the light source end used for the monitoring function and the output results of the APD and PMT at the particle measurement end can be correlated to reduce the system noise of the particle size spectrometer, improve the signal-to-noise ratio, and thus improve the measurement accuracy of particle size and concentration.

[0055] (3) For the polarization differential optical path of the (dynamic) particle size spectrometer, by designing the extinction structure of the sample chamber light entrance, the light contamination of the particle sample chamber by the diffracted light can be minimized, thereby reducing the background noise of the APD and PMT at the back end (particle measurement end) and effectively improving the signal-to-noise ratio.

[0056] (4) A high-efficiency extinction chamber is designed for the end of the optical path of the kinetic particle size spectrometer to reduce the amount of light reflected back to the detection chamber (optical chamber), thereby reducing the background noise of the APD and PMT and effectively improving the signal-to-noise ratio.

[0057] See also Figure 1An embodiment of the present invention provides a particle analysis device based on particle size spectrum. In this embodiment, the particle analysis device based on particle size spectrum includes: a beam generating and shaping unit, a light source monitoring unit, a stray light filtering unit, an isolation unit, a sample chamber, an avalanche photodiode detector 11, a photomultiplier tube detector 12 and a computing unit, wherein the beam generating and shaping unit, the light source monitoring unit, the stray light filtering unit, the isolation unit, the sample chamber and the computing unit are not shown in the figure.

[0058] a beam generating and shaping unit, configured to excite a first linearly polarized light of the collimated light, adjust the polarization state of the first linearly polarized light into a second linearly polarized light having the same energy as the horizontal component and the vertical component, expand the second linearly polarized light, and then split the light according to a preset splitting ratio to obtain a first laser beam and a second laser beam, output the first laser beam to a light source monitoring unit, and converge the second laser beam to form a converged beam and output it to a stray light filtering unit, wherein the laser energy of the first laser beam is less than the laser energy of the second laser beam;

[0059] In this embodiment, as an optional embodiment, the beam generating and shaping unit includes: a laser 001, a paddle 002, a first concave lens 003, a first convex lens 004, a beam splitter 005, a second convex lens 006, and a third convex lens 007, wherein:

[0060] Laser 001, used for exciting and outputting the first linear polarized light of the collimated light;

[0061] The paddle 002 is connected to the laser 001, vertically receives the first linearly polarized light emitted by the laser 001, adjusts the polarization state of the incident first linearly polarized light so that the energy of the horizontal component is equal to the energy of the vertical component, obtains the second linearly polarized light and outputs it;

[0062] In this embodiment, as an optional embodiment, the diameter of the first linearly polarized light emitted by the laser is 1 mm, and the plate is a quarter-wave plate. The laser emitting collimated light outputs the first linearly polarized light with a diameter of 1 mm, which is perpendicularly incident on the quarter-wave plate. By rotating and adjusting the angle of the quarter-wave plate, the polarization state of the incident first linearly polarized light is adjusted to a second linearly polarized light with the same energy in the horizontal and vertical components.

[0063] The first concave lens 003 is connected to the paddle 002 and receives the second linearly polarized light output by the paddle 002;

[0064] The first convex lens 004 is connected to the first concave lens 003. The first concave lens 003 and the first convex lens 004 form a beam expander for expanding the incident second polarized light to obtain expanded light;

[0065] In this embodiment, as an optional embodiment, both the first concave lens and the first convex lens are circular. After the second linearly polarized light output by the quarter-wave plate after adjusting the rotation angle passes through a beam expander composed of a circular concave lens and a circular convex lens, the diameter of the first linearly polarized light (the first polarized light of the thin beam emitted by the laser) or the second linearly polarized light can be widened to 4-5 mm. In this way, the beam expander composed of the first concave lens and the first convex lens can be used to filter out some stray light, improve the quality of the expanded light (laser beam) obtained after expanding the second linearly polarized light, and enhance the accuracy of subsequent particle size and concentration statistics. As an optional embodiment, the diameter of the expanded light is 4-5 mm.

[0066] Beam splitter 005 is connected to first convex lens 004 and is used to split the expanded beam to obtain a first laser beam reflected from beam splitter 005 and a second laser beam that penetrates the beam splitter. The first laser beam is incident on second convex lens 006, converged by second convex lens 006, and then incident on the light source monitoring unit. The second laser beam is incident on third convex lens 007. The laser energy of the first laser beam is much smaller than the laser energy of the second laser beam.

[0067] In this embodiment, as an optional embodiment, the spectroscope is a calcite spectroscope.

[0068] The third convex lens 007 is connected to the beam splitter 005 and is used to converge the second laser beam in the Y-axis direction representing the energy of the vertical component to obtain a converged beam, which is incident on the stray light filtering unit, wherein the horizontal component energy and the vertical component energy of the polarization state of the converged beam are the same.

[0069] In this embodiment, the first laser beam is output to the light source monitoring unit through the second convex lens, and the second laser beam is output to the stray light filtering unit through the third convex lens.

[0070] In this embodiment, as an optional embodiment, the third convex lens is a cylindrical convex lens. As an optional embodiment, the ratio of the laser energy of the first laser beam to the laser energy of the second laser beam is less than 1:9. For example, after the expanded light passes through the beam splitter, 90% of the laser energy (the second laser beam) can be transferred to the next cylindrical convex lens, thereby converging the light of the second laser beam in the Y-axis direction after the expanded light is split to the focal point, thereby forming a 4-5 mm wide light plane along the X-axis at the focal point.

[0071] In this embodiment, the horizontal component energy and the vertical component energy of the polarization state of the light rays converged in the Y-axis direction by the cylindrical convex lens are the same.

[0072] In this embodiment, a laser, a quarter-wave plate, a calcite beam splitter, a beam expander consisting of a first concave lens and a first convex lens, and a cylindrical convex lens form a beam shaping unit. Within the beam shaping unit, the laser is a linearly polarized light output unit; the quarter-wave plate adjusts the polarization angle of the beam, aligning the horizontal and vertical components of the first linearly polarized light, thereby producing a second linearly polarized light. The second linearly polarized light passes through the first concave lens, the first convex lens, and the beam splitter, forming a first laser beam and a second laser beam. The beam expander and cylindrical convex lens are primarily used for beam shaping, filtering stray light with large divergence angle deviations and improving beam quality.

[0073] In the beam shaping unit, as an optional embodiment, the expanded beam passes through a beam splitter to reflect 10% of the expanded beam to the ADP, i.e., the light source monitoring unit, in a direction perpendicular to the original beam (expanded beam), to achieve real-time monitoring of the expanded beam.

[0074] a light source monitoring unit, configured to detect first light intensity information of the first laser beam, obtain first voltage information after conversion, and output the first voltage information to the calculation unit;

[0075] In this embodiment, as an optional embodiment, the light source monitoring unit includes a first avalanche photodiode 008 (light source end ADP). After the expanded beam passes through the beam splitter, 10% of the expanded beam (the first laser beam) is reflected onto the first ADP in a direction perpendicular to the original beam (expanded beam), thereby enabling real-time monitoring of the light source.

[0076] In this embodiment, the light source noise monitoring unit is used to monitor the light source, which can solve the problem of abnormal light source fluctuation.

[0077] In this embodiment, the stability of the linearly polarized light used as the light source in the aerodynamic particle size spectrometer significantly impacts its overall performance. The light source is a semiconductor laser, which is susceptible to temperature fluctuations and electromagnetic radiation, causing light source jitter, which can affect the detection of light scattering characteristics. For example, when the light source weakens, the scattered light from the same particles will also weaken, potentially being misidentified as scattered light from particles, thus affecting the operation of the aerodynamic particle size spectrometer. Furthermore, as the laser in the aerodynamic particle size spectrometer operates over time, it will experience a certain degree of attenuation, which can also lead to deviations in the analysis of particle scattering characteristics. Furthermore, the emission of the semiconductor laser can be affected by electromagnetic environments and vibrations. For example, power supply noise, periodic electromagnetic radiation, and strong vibrations can cause instantaneous fluctuations in the laser intensity output by the semiconductor laser. These transient fluctuations can cause the recognition algorithm of the aerodynamic particle size spectrometer to misjudge noise signals as particles. In this embodiment, the kinetic particle size spectrometer is provided with a light source monitoring unit to realize the function of real-time monitoring while performing temperature control on the light source. The light source signal is detected by the APD at the light source end. In this way, the changes of the light source can be fed back to the operation unit. The feedback light source detection signal (first voltage information) is coherently calculated with the scattered light detection signal of the APD and PMT at the subsequent chamber end, thereby improving the signal-to-noise ratio, increasing the resolution and detection sensitivity, and ensuring the stability of the aerodynamic particle size spectrum.

[0078] A stray light filtering unit is used to split the converged light beam to form two parallel light beams along the X axis with equal spacing along the Y axis at the light focus in the sample chamber, filter out stray light from the parallel light beams, and output the parallel light beams after the stray light is filtered into the sample chamber through the isolation unit;

[0079] In this embodiment, as an optional embodiment, the stray light filtering unit includes: a beam splitting crystal 009 and an aperture 010, wherein:

[0080] Beam splitting crystal 009 is used to split the converged light beam to form two parallel beams along the X axis with equal spacing on the Y axis at the focus of the light beam. The X axis is the direction connecting the laser, the paddle, the concave lens, the first convex lens, the second convex lens, and the center point of the beam splitting crystal, and the Y axis is the direction perpendicular to the X axis.

[0081] In this embodiment, as an optional embodiment, the beamsplitting crystal is a calcite beamsplitter. The beamsplitter crystal is used to separate the X-axis horizontal component energy and the Y-axis vertical component energy of the input linearly polarized light (convergent beam). The beamsplitting distance is related to the wavelength of the light and the thickness of the beamsplitter crystal. For example, for 630nm red light incident on a 1mm thick calcite beamsplitter, the beamsplitting distance is approximately 100µm. After the converging beam passes through the calcite beamsplitter, it outputs two equally spaced parallel beams of equal brightness.

[0082] In this embodiment, after the converging light beam passes through the calcite beam splitter, the polarized light along the X-axis does not shift or change, but due to the increase in the optical path, the polarized light along the Y-axis shifts a certain distance, thereby forming two parallel light beams with a certain splitting distance on the Y-axis (for example, for a calcite beam splitter with a thickness of 1 mm, the splitting distance is approximately 100 μm) but whose propagation direction does not change. That is, after passing through the calcite beam splitter, the converging light beam can form two parallel light beams along the X-axis with equal spacing along the Y-axis at the light focus in the sample chamber, wherein the width of the parallel light beam is 4-5 mm, the height (the vertical distance between the centers of the two parallel light beams) is approximately 100 μm, and the light intensity distribution of the single parallel light beam exhibits a normal distribution on the Y-axis.

[0083] The aperture 010 is used to perform multi-stage stray light filtering on the parallel light beam, and output the parallel light beam after the stray light is filtered into the sample chamber through the isolation unit.

[0084] Figure 2 Schematic diagram of the aperture structure provided by an embodiment of the present invention. Figure 2As shown, in this embodiment, as an optional embodiment, the aperture 010 is a rectangular slit aperture, comprising a first-stage rectangular slit aperture 020, a second-stage rectangular slit aperture 021, and a third-stage rectangular slit aperture 022, each connected in sequence. Adjacent rectangular slit apertures are 5 mm apart, and the slit width is 1 mm. The two focused parallel light beams pass through three stages of 1 mm x 5 mm rectangular slit apertures spaced 5 mm apart, then pass through an isolation unit, such as the first window mirror 011, and enter the gap between the air inlet 023 and the air outlet 024 in the sample chamber. The three-stage rectangular slit apertures are used to filter stray light, ensuring that the parallel light beams entering the sample chamber have good directionality and reducing scattered light caused by the optical path. In this way, by using multiple stages of slit apertures of the same size, when a parallel light beam passes through the first stage slit aperture, the diffracted light or scattered light generated by the first stage slit aperture will be blocked by the second stage slit aperture. Since the main light beam (parallel light beam) is of the same size as the slit, the second stage slit aperture can block a large amount of diffracted light, resulting in a small amount of diffracted light entering the third stage slit aperture. In this way, after passing through the third stage slit aperture, the diffracted light is greatly reduced. The use of multiple stages of slit apertures can effectively reduce the diffracted light caused by the slit edges in parallel light beams.

[0085] In this embodiment, by providing a multi-stage slit aperture at the light entrance of the sample chamber, stray light diffracted by the pinhole is effectively reduced.

[0086] In this embodiment, to shield stray light from the light source, a slit is placed at the light input port (light entrance) of the sample chamber. This slit effectively filters out stray light introduced by the optical system and controls beam quality. However, since the light beam scatters at the edges of the slit, diffracted light can scatter within the sample chamber. After striking components such as the jet column within the chamber, it generates strong diffuse reflections that couple to the detector, affecting detection results. To suppress slit-scattered light, this embodiment improves the optical path structure by nesting multiple slit apertures. This effectively reduces the amount of scattered light entering the chamber, thereby reducing background light noise within the chamber.

[0087] In this embodiment, the laser light source output by the aerodynamic particle size spectrometer is split into two parallel beams separated by 100 μm in the Y-axis direction. These parallel beams pass through a slit and are input into the chamber within the sample chamber. As the particles fall, they irradiate and scatter. In related art, because only a single slit is designed at the chamber entrance, a large amount of derivative light enters the chamber, irradiating the airflow nozzle and airflow absorption nozzle within the chamber that drive the particles. This diffuse reflection increases the noise floor of the APD detector, thereby affecting the accuracy and sensitivity of the particle size spectrometer.

[0088] An isolation unit, comprising a first window mirror 011 and a second window mirror 012. The first window mirror 011 is connected to the aperture 010 and is used to isolate the sample chamber from the beam generating and shaping unit, or the sample chamber from the stray light filtering unit, so as to prevent the gas to be detected with particulate matter in the sample chamber from contaminating the optical path environment of the beam generating and shaping unit and the stray light filtering unit. The second window mirror 012 is used to isolate the sample chamber from the avalanche photodiode detector 11, and from the photomultiplier tube detector 12, respectively.

[0089] In this embodiment, the first window mirror is used to isolate the sample chamber from the optical path generation and shaping unit and the stray light filtering unit, so that the gas to be detected with particulate matter in the sample chamber will not contaminate the optical path environment of the optical path generation unit and the stray light filtering unit; the two parallel light beams passing through the first window mirror will be focused on the light focus at the middle position between the air inlet and the air outlet of the sample chamber. The light focus has a certain distance interval on the Y axis (the direction of particle movement), which serves as the convergent focus of the two parallel light beams.

[0090] The sample chamber is used to input the sample to be tested. When the sample to be tested falls to the focus of the two parallel light beams, it is illuminated by the two parallel light beams and diffusely reflected by the particles contained in the sample to be tested. The side diffusely reflected light beams are converged and input to the avalanche photodiode detector, and the forward diffusely reflected light beams are converged and input to the photomultiplier tube detector.

[0091] Figure 3 A schematic diagram of the main structure of the sample chamber provided in an embodiment of the present invention;

[0092] Figure 4 A schematic side view of the sample chamber structure provided in an embodiment of the present invention;

[0093] Figure 5 This is another schematic diagram of the main structure of the sample chamber provided by the embodiment of the present invention. Figures 3 to 5 As shown, in this embodiment, as an optional embodiment, the sample chamber includes: an aerodynamic gas nozzle 013, a second concave mirror 014, a focusing lens 015, a fourth convex lens 016 and a chamber 025, wherein,

[0094] Figure 6 Schematic diagram of the aerodynamic gas nozzle structure provided by an embodiment of the present invention. Figures 3 to 6As shown, the aerodynamic gas nozzle 013 is used to input the sample to be tested into the chamber 025. When the sample to be tested falls to the focus of the light in the chamber, two parallel light beams, namely the split O light 026 and the split E light 019, pass through the stray light filtering unit to illuminate the particles 020 in the sample to be tested, causing diffuse reflection in the chamber 025, forming a lateral diffuse reflection light beam and a forward diffuse reflection light beam. The sample to be tested is the gas to be tested. Before the gas to be tested is input, it is verified by inputting a particle-free sheath gas. As an optional embodiment, the aerodynamic gas nozzle is a sheath-type nozzle, including but not limited to: a sheath-type nozzle outer nozzle 61 and a sheath-type nozzle inner nozzle 62, wherein the sheath-type nozzle outer nozzle 61 has an inner diameter of 6 mm, the sheath-type nozzle outer nozzle opening 63 has a diameter of 1.1 mm, the sheath-type nozzle inner nozzle 62 has an inner diameter of 2 mm, the sheath-type nozzle inner nozzle opening 64 has a diameter of 0.8 mm, and the spacing 65 between the sheath-type nozzle outer nozzle and the sheath-type nozzle inner nozzle is 1 mm.

[0095] In this embodiment, the two parallel light beams filtered by the stray light filtering unit are focused at a position between the air inlet and the air outlet of the aerodynamic gas nozzle (light focus), and the focused light focuses are spaced apart on the Y axis.

[0096] The second concave mirror 014 is disposed at a lateral position in the chamber 025 to converge the diffusely reflected light beam from the side of the sample to be measured to the focusing lens 015;

[0097] In this embodiment, as an optional embodiment, the second concave mirror is located at a lateral position in the chamber at the same height as the parallel light beam.

[0098] The focusing lens 015 focuses the lateral diffusely reflected light collected by the second concave mirror 014 and inputs the focused light into the avalanche photodiode detector 11;

[0099] The fourth convex lens 016 is disposed at a forward position in the chamber 025 , and converges the forward diffusely reflected light beam received from the sample to be tested onto the photomultiplier tube detector 12 .

[0100] In this embodiment, as an optional embodiment, the focusing lens and the second concave mirror are located on the same side.

[0101] In this embodiment, when particulate matter falls from the air inlet and passes through the focal points of two parallel light beams, the two parallel light beams illuminate the particulate matter and scatter. At the two focal points, scattered light (diffusely reflected light beams) of a certain intensity is emitted outward. A portion of the side scattered light (lateral diffusely reflected light beam) is focused by the second side concave mirror, i.e., the concave mirror and the focusing lens, and then detected by the other side rear-end APD, i.e., the APD detector, thereby forming two photocurrent pulses (light intensity information) with a certain time interval. After being converted into voltage information, it is output to the calculation unit. After circuit processing and analysis by the calculation unit, the size and other characteristics of the particulate matter can be obtained.

[0102] The avalanche photodiode detector 11 is used to detect the second light intensity information of the lateral diffusely reflected light beam, obtain the second voltage information after transformation, and output it to the calculation unit;

[0103] The photomultiplier tube detector 12 is used to detect the third light intensity information of the forward diffusely reflected light beam, obtain the third voltage information after transformation, and output it to the calculation unit;

[0104] In this embodiment, the avalanche photodiode detector is a back-end APD that detects light scattering peak information (second light intensity information) of a scattered light signal from a diffusely reflected light beam (lateral diffusely reflected light beam) input from a focusing lens. The detected light scattering peak information is transformed and then output to a computing unit. As another alternative embodiment, the avalanche photodiode detector may also output the detected light scattering peak information to a computing unit, which then performs the corresponding transformation.

[0105] In this embodiment, as an optional embodiment, the rear-end APD is located on the other side opposite to the second concave mirror.

[0106] In this embodiment, as an optional embodiment, the device further includes:

[0107] The filter assembly is used to perform extinction processing on the other parallel light beams among the two parallel light beams except for the parallel light beams irradiating the particles in the sample to be measured.

[0108] In this embodiment, as an optional embodiment, the filter assembly can be set in the sample chamber, including: a first neutral density filter 017 and a second neutral density filter 018, wherein:

[0109] The first neutral density filter 017 is installed in the optical path of the parallel light beam at a preset Brewster angle, absorbs the incident horizontally polarized parallel light beam and part of the vertically polarized parallel light beam, and reflects the other part of the vertically polarized parallel light beam that is not absorbed to the second neutral density filter 018;

[0110] The second neutral density filter 018 is arranged spatially relative to the first neutral density filter 017 and rotated 90° in the vertical light path propagation direction to absorb another part of the incident vertically polarized parallel light beam.

[0111] In this embodiment, as an optional embodiment, a first neutral density filter with a reflector function is arranged at the center position of the fourth convex lens, which can reflect and absorb the parallel light beam to prevent the parallel light beam from directly entering the target surface of the PMT detector. The receiving surface of the fourth convex lens that is not blocked by the reflector (first neutral density filter) can focus the forward scattered light of the particulate matter onto the detection surface of the PMT detector, thereby achieving the maximum reception of the forward scattered light of the particulate matter.

[0112] In this embodiment, a parallel light beam passes through a first neutral density filter, mounted at a pre-set Brewster's angle, in the optical path. Theoretically, this first neutral density filter absorbs 100% of the horizontally polarized parallel light beam and a portion of the vertically polarized parallel light beam, while reflecting the remaining vertically polarized parallel light beam to a second neutral density filter. The second neutral density filter is spatially rotated 90° relative to the first neutral density filter, perpendicular to the propagation direction of the optical path. This position, along with the Brewster's angle, allows for 100% absorption of the vertically polarized light beam. Thus, through the absorption filtering of the two-stage polarization filter, maximum extinction can be achieved. That is, after the parallel light beam passes through the focus of the light and irradiates the particles, it will diverge and continue to propagate along the direction of the light beam to illuminate the rear convex lens, that is, the neutral density filter installed at the Brewster angle on the fourth convex lens. The neutral density filter can achieve complete absorption of polarized light along the X axis and partial absorption of polarized light along the Y axis, and at the same time reflect the unabsorbed Y-axis polarized light to another neutral density filter installed at the Brewster angle, achieving complete absorption of the Y-axis polarized light again, thereby achieving complete extinction of the parallel light beam in the sample chamber.

[0113] In this embodiment, the extinction chamber composed of a filter assembly is designed for polarized light, which can theoretically absorb 100% of the laser energy, thereby effectively improving the extinction efficiency and reducing light reflection.

[0114] In this embodiment, as another optional embodiment, black Teflon matte material may be coated on the sample chamber and the filter assembly to minimize diffuse reflection of the parallel light beam, thereby increasing the signal-to-noise ratio.

[0115] Figure 7 Schematic diagram of calculating Brewster angle provided by an embodiment of the present invention. Figure 7 As shown, in this embodiment, as an optional embodiment, the Brewster angle is calculated using the following formula:

[0116]

[0117] Where, is Brewster's angle, is the refractive index of the filter element (first neutral density filter or second neutral density filter), is the refractive index of air.

[0118] In this embodiment, the filter assembly forms a laser absorption extinction chamber to reduce light rebound.

[0119] an operation unit for receiving the first light intensity information, the second light intensity information, and the third light intensity information, and performing a coherent operation on the first light intensity information and the second light intensity information according to a preset coherent algorithm to obtain effective information detected by the APD, and performing a coherent operation on the first light intensity information and the third light intensity information to obtain effective information detected by the PMT;

[0120] According to the signal-to-noise ratio of the effective information detected by the APD, it is determined whether the effective information detected by the APD or the effective information detected by the PMT is used for particle analysis. The particle analysis includes: particle concentration corresponding to the particle size distribution.

[0121] In this embodiment, as an optional embodiment, the coherent operation is to perform dynamic differential calculation based on the first light intensity information obtained by the light source monitoring unit, the second light intensity information obtained by the avalanche photodiode detector, and the third light intensity information obtained by the photomultiplier tube detector, so as to calculate the multiplication factor used for light intensity correction through calibration.

[0122] In this embodiment, whether it is Mie scattering or Rayleigh scattering, the side scattered light is relatively small, so the APD installed on the side can receive a certain intensity of light scattering signal and is not easily saturated. However, due to the light scattering angle of small particles and the low sensitivity of the APD, the APD detector cannot detect the scattered light emitted by small particles when passing through the parallel light beam, and therefore cannot provide effective data to the back-end processing method, resulting in the inability to identify small particles. In this embodiment, the PMT detector is installed in the direction of the particle size forward scattering of the stronger scattered light in the aerodynamic particle size spectrometer. At the same time, due to its high gain, the PMT detector can detect the scattered light of small particles. At the same time, it is easily saturated for large particles, resulting in the inability to normally output effective signals. In this embodiment, based on the above characteristics, the data output by the APD detector and the PMT detector after coherent operation are fused through a pre-set algorithm, and the signal-to-noise ratio (SNR) of the APD detector output signal is used as the measurement benchmark. Specifically, as an optional embodiment, based on the signal-to-noise ratio of the APD detection effective information, it is determined whether to use the APD detection effective information or the PMT detection effective information for particle analysis, including:

[0123] Determining that a signal-to-noise ratio of effective information detected by the APD is greater than or equal to a first signal-to-noise ratio threshold and the effective information detected by the APD is not saturated, and performing conventional peak time difference detection using the effective information detected by the APD; or determining that a signal-to-noise ratio of effective information detected by the APD is less than the first signal-to-noise ratio threshold, and a signal-to-noise ratio of effective information detected by the PMT is greater than or equal to a second signal-to-noise ratio threshold and the effective information detected by the PMT is not saturated, and performing conventional peak time difference detection using the effective information detected by the PMT, so as to perform particle analysis based on the conventional peak time difference detection result;

[0124] Determine whether the signal-to-noise ratio of the effective information detected by the APD is greater than or equal to the first signal-to-noise ratio threshold and the effective information detected by the APD is saturated, calculate the peak difference at the middle moment of the effective information detected by the APD instead of the peak time difference, or, if the signal-to-noise ratio of the effective information detected by the APD is less than the first signal-to-noise ratio threshold, the signal-to-noise ratio of the effective information detected by the PMT is greater than or equal to the second signal-to-noise ratio threshold, and the effective information detected by the PMT is saturated, calculate the peak difference at the middle moment of the effective information detected by the PMT instead of the peak time difference, and perform particle analysis based on the replaced peak time difference detection result.

[0125] In this embodiment, as an optional embodiment, when the signal-to-noise ratio of the APD detection effective information is less than the first signal-to-noise ratio threshold and the signal-to-noise ratio of the PMT detection effective information is less than the second signal-to-noise ratio threshold, the PMT detection effective information is considered invalid and peak time difference detection is not performed.

[0126] In this embodiment, as an optional embodiment, the first signal-to-noise ratio threshold is 10 dB, and the second signal-to-noise ratio threshold is 6 dB, which is not limited in this embodiment.

[0127] In this embodiment, due to factors such as the circuit, optical path structure, and sensor production process, the signals output by the light source monitoring unit, APD detector, and PMT detector will have certain noise. In order to effectively reduce the impact of the noise, the operation unit is further used to:

[0128] After receiving the first light intensity information, the second light intensity information and the third light intensity information, before performing coherent operations on the first light intensity information and the second light intensity information respectively according to a preset coherence algorithm, the first light intensity information, the second light intensity information and the third light intensity information are filtered respectively using a preset filtering algorithm.

[0129] In this embodiment, a filtering algorithm is implemented within the computational unit to filter the detector's output signal, thereby removing spurious noise from the output signal, improving peak resolution accuracy, and enabling peak time difference detection. As an optional embodiment, the filtering algorithm is based on an FIR low-pass filter and dynamically adaptive parameter adjustment to achieve adaptive filtering of signals under different conditions.

[0130] In this embodiment, when a particle falls through the focal point of two parallel light beams, they are incident on the particle, each emitting scattered light of varying intensity. This scattered light includes forward scattered light, side scattered light, and back scattered light. Of the scattered light emitted by the focal point of the two parallel light beams, a portion of the forward scattered light is focused by a forward lens and detected by a forward PMT detector, generating two photocurrent pulses separated by a predetermined time interval. This pulse is then processed and analyzed by subsequent circuitry to determine the particle size and other characteristics.

[0131] In this embodiment, the PMT detector has better sensitivity than the front-end APD detector, and can detect weak scattered light from tiny particles that the APD detector cannot detect.

[0132] In this embodiment, the aerodynamic method involves the principles of aerodynamics, polarized laser optics, time-of-flight, and light scattering. Particles of different diameters experience different velocities in the high-speed jet flow created by the aerodynamic airflow path structure. Large particles experience lower velocities, while small particles experience higher velocities. Because the laser light emitted by a polarized laser possesses excellent linear polarization properties, it is rotated by a certain angle by a wave plate before undergoing shaping and reentering the beam splitter crystal. This polarized light passes through the crystal in a straight line relative to the horizontal light (O light) from the beam splitter crystal, while the vertical light (E light) is offset by a certain distance. The offset depends on the wavelength of the light and the length of the crystal. Therefore, using a polarized laser, it is possible to achieve beam splitting of the output light.

[0133] Figure 8 Schematic diagram of particle analysis principle provided by an embodiment of the present invention. Figure 8 As shown, in this embodiment, when particles ejected at high speed pass through a parallel light beam at a certain distance, they scatter. A photoelectric detector, such as a PMT detector, located at an angle not directly incident on the light beam receives the scattered light signal. The scattered light signal is converted into an electrical signal for collection and processing by the back-end circuit. The longer the particle travels through the parallel light beam, the wider the peak-to-peak interval between the light scattering peaks of the scattered light signal obtained by the photoelectric detector. Conversely, the shorter the peak-to-peak interval between the light scattering peaks of the scattered light signal obtained by the detector, the smaller the peak-to-peak interval between the light scattering peaks of the scattered light signal. Thus, the aerodynamic diameter of the particle can be determined from the peak-to-peak interval. Furthermore, by determining the peak-to-peak value, the light scattering characteristics of the particle size can also be determined, facilitating further analysis of other properties of the particle.

[0134] In this embodiment, a PMT detector is added to the aerodynamic particle size spectrometer, allowing the combined use of an APD and PMT detectors to address the technical issue of the APD's low sensitivity. Specifically, by combining the PMT and APD detectors, the APD detector detects side-scattered light from large particles in the aerodynamic particle size spectrometer, while the PMT detector detects forward-scattered light from Mie scattering from small particles in the aerodynamic particle size spectrometer. This enables continuous, real-time statistical analysis of particles ranging from tens of nanometers to hundreds of microns.

[0135] Figure 9 The following is a flow chart of a particle analysis method based on particle size spectrum provided by an embodiment of the present invention. Figure 9 As shown, the particle analysis is performed using the above device, and the method includes:

[0136] S101, turning on the particle analyzer, introducing zero gas after self-test, obtaining an optimal APD coefficient based on first light intensity information from the light source monitoring unit and second light intensity information from the avalanche photodiode detector, and obtaining an optimal PMT coefficient based on the first light intensity information from the light source monitoring unit and third light intensity information from the photomultiplier tube detector;

[0137] In this embodiment, the first light intensity information is the light source APD measurement value, the second light intensity information is the light scattering APD measurement value, and the third light intensity information is the light scattering PMT measurement value. The light source monitoring unit is called the light source end ADP, the avalanche photodiode detector is called the front-end ADP, and the photomultiplier tube detector is called the back-end PMT.

[0138] In this embodiment, after the particle analysis device (equipment) is turned on, data collection and measurement are performed using the ADP at the light source end, the front-end APD, and the back-end PMT under the condition of introducing zero gas. Since the output data intensity of the APD at the light source end is linearly correlated with the output data intensity of the front-end APD and the output data intensity of the back-end PMT, the light-scattering APD measurement value is subtracted from the light source APD measurement value multiplied by the APD coefficient to obtain the APD effective value (error), and the APD coefficient corresponding to the minimum APD effective value is obtained to obtain the optimal APD coefficient.

[0139] In this embodiment, the optimal APD coefficient is calculated using the following formula:

[0140]

[0141] Where, is the APD coefficient, is the light scattering APD measurement value, is the light source APD measurement value. In this embodiment, Corresponding is the optimal APD coefficient, that is .

[0142] In this embodiment, by changing the APD coefficient When the effective value of the calculated result is the smallest, the corresponding APD coefficient is the optimal APD coefficient, and the optimal APD coefficient is saved.

[0143] In this embodiment, the light source APD measurement value multiplied by the PMT coefficient is subtracted from the light dispersion PMT measurement value to obtain the PMT effective value. The PMT coefficient corresponding to the minimum PMT effective value is obtained to obtain the optimal PMT coefficient.

[0144] In this embodiment, the optimal APD coefficient is calculated using the following formula:

[0145]

[0146] Where, Corresponding is the optimal PMT coefficient, that is , is the PMT coefficient, is the light scattering PMT measurement value.

[0147] S102, introducing a sample gas, obtaining a first light-scattering APD based on first light intensity information from a light source monitoring unit, second light intensity information from an avalanche photodiode detector, and an optimal APD coefficient, and obtaining a second light-scattering APD based on the first light intensity information from the light source monitoring unit, third light intensity information from a photomultiplier tube detector, and an optimal PMT coefficient;

[0148] In this embodiment, the first light scattering APD is obtained based on the light source APD measurement value of the light source end APD, the light scattering APD measurement value of the front-end APD and the optimal APD coefficient, and the second light scattering APD is obtained based on the light source APD measurement value of the light source end APD, the light scattering PMT measurement value of the back-end PMT and the optimal PMT coefficient.

[0149] In this embodiment, a sample gas (gas containing particles to be measured) is introduced into the device, and the scattered light measurement results obtained are:

[0150]

[0151]

[0152] Where, is the scattered light APD measurement result, namely the first light scattered APD, is the scattered light PMT measurement result, namely the second light scattering APD.

[0153] S103, calculating the signal-to-noise ratio of the first light-scattering APD and the signal-to-noise ratio of the second light-scattering APD based on a preset signal-to-noise ratio calculation formula;

[0154] In this embodiment, the signal-to-noise ratio is calculated using the following formula:

[0155] SNR=20×log10(Vs / Vn)

[0156] Where, SNR is the signal-to-noise ratio, Vs is the maximum value of the detector output signal (first light scattering APD), Vn It is the maximum value of the detector output noise when there is no light signal (only zero gas is introduced).

[0157] S104 , determining a light scattering APD for particle analysis from the first light scattering APD and the second light scattering APD based on the signal-to-noise ratio of the first light scattering APD, the signal-to-noise ratio of the second light scattering APD, and a preset signal-to-noise ratio threshold.

[0158] In this embodiment, after the device is turned on and passes the self-test, zero gas (filtered clean air or high-purity nitrogen) is introduced, and the maximum noise value of the side-scattering APD and forward-scattering PMT is detected. The gas to be tested (sample gas) is introduced, and the maximum value of the scattered light from the front-end APD and rear-end PMT after particles of different particle sizes enter the particle analyzer is measured. The signal-to-noise ratio (SNR) of the front-end APD and rear-end PMT is calculated in real time. The SNR of the front-end APD output signal is then used as the measurement benchmark:

[0159] When the signal-to-noise ratio of the APD output signal is greater than or equal to 10 dB and the APD output signal is not saturated, the APD output signal is used for conventional peak time difference detection;

[0160] When the APD output signal signal-to-noise ratio is greater than or equal to 10 dB and the APD output signal is saturated, the peak time difference is replaced by calculating the peak difference at the middle moment of the APD output signal saturation value;

[0161] When the APD output signal signal-to-noise ratio is less than 10dB and the PMT output signal is not saturated and the signal-to-noise ratio is greater than or equal to 6dB, the PMT signal is used for conventional peak time difference detection;

[0162] When the APD output signal signal-to-noise ratio is less than 10dB and the PMT output signal is saturated and the signal-to-noise ratio is greater than or equal to 6dB, the peak time difference is replaced by calculating the peak difference at the middle moment of the PMT output signal saturation value;

[0163] When the APD output signal signal-to-noise ratio is less than 10dB and the PMT signal signal-to-noise ratio is less than 6dB, the PMT output signal is considered invalid and peak time difference detection is not performed.

[0164] Figure 10Another flow chart of a particle analysis method based on particle size spectrum provided by an embodiment of the present invention. Figure 10 As shown, the method includes:

[0165] S201, perform a self-test on the particle analysis device, if the self-test passes;

[0166] S202, introduce zero gas;

[0167] S203, wait for 30 minutes;

[0168] S204, collecting APD and PMT signals;

[0169] S205, filtering using an adaptive parameter FIR filter;

[0170] S206, measuring data for a certain time. If the measurement time is not met, return to step S204;

[0171] S207, calculating the maximum value of APD and PMT noise;

[0172] S208, introducing sample gas;

[0173] S209, collecting APD and PMT signals;

[0174] S210, filtering using an adaptive parameter FIR filter;

[0175] S211, measure data for a certain time. If the measurement time is not met, return to step S209;

[0176] S212, measuring the maximum value of APD and PMT signals;

[0177] S213, calculating the signal-to-noise ratio of the APD and PMT;

[0178] S214, if APD SNR ≥ 10dB and APD is not saturated, execute step S215;

[0179] S215, APD peak time difference method;

[0180] S216, if APD SNR ≥ 10dB and APD is saturated, execute step S217;

[0181] S217, APD saturation region median time difference method;

[0182] S218, if APD SNR<10dB, PMT SNR≥6dB and PMT is not saturated, execute step S219;

[0183] S219, PMT peak time difference method;

[0184] S220, if APD SNR<10dB, PMT SNR≥6dB and PMT is saturated, execute step S221;

[0185] S221, PMT saturation region median time difference method;

[0186] S222: If APD SNR < 10dB, PMT SNR < 6dB, and PMT is not saturated, proceed to step S223.

[0187] S223, do not detect time difference;

[0188] S224, store the calculation result and return to step S208.

[0189] Figure 11 Another flow chart of a particle analysis method based on particle size spectrum provided by an embodiment of the present invention. Figure 11 As shown, the method includes:

[0190] S301, perform a self-test on the particle analysis device, if the self-test passes;

[0191] S302, introduce zero gas;

[0192] S303, obtain initialization and ;

[0193] S304, wait for 30 minutes;

[0194] S305, measuring the light source APD and scattered light APD measurement values;

[0195] S306, filtering using an adaptive parameter FIR filter;

[0196] S307, measuring data for a certain period of time;

[0197] S308, calculate ( )’s effective value;

[0198] S309, determine whether the effective value is the minimum, if so, execute step S310, if not, change , return to step S305;

[0199] S310, storage record ;

[0200] S311, measuring the light source APD and scattered light PMT measurement values;

[0201] S312, filtering using an adaptive parameter FIR filter;

[0202] S313, measuring data for a certain period of time;

[0203] S314, calculate ( )’s effective value;

[0204] S315, determine whether the effective value is the minimum, if so, execute step S316, if not, change , return to step S311;

[0205] S316, store records ;

[0206] S317, confirming that the calibration is completed;

[0207] S318, introduce sample gas;

[0208] S319, calculate the light dispersion APD: ;

[0209] S320, calculate light scatter PMT: ;

[0210] S321, fusion calculation of light scattering APD and light scattering PMT.

[0211] In this embodiment, the above implementation process is combined to achieve a sample chamber measurement environment with extremely low background stray light. Simultaneously, the use of high-quality, equally spaced, focused parallel light beams increases the energy of the light irradiating the particles, improving the signal-to-noise ratio and resolution. It also increases the particle incident area, reducing particle escape, increasing the probability of detection, and improving the dynamic range. Therefore, the present invention, designed to broaden the dynamic range and resolution of a particle size spectrometer, has achieved excellent results through actual measurements and verification, achieving its intended purpose.

[0212] Based on the same inventive concept, an embodiment of the present invention further provides a storage medium storing a computer program, which, when executed by a processor, implements the steps of the particle analysis method based on particle size spectrum in any possible implementation manner described above.

[0213] Alternatively, the storage medium may be a non-transitory computer-readable storage medium, for example, a ROM, a random access memory (RAM), a CD-ROM, a magnetic tape, a floppy disk, an optical data storage device, and the like.

[0214] Based on the same inventive concept, see Figure 12An embodiment of the present invention further provides an electronic device comprising a memory 101 (e.g., a nonvolatile memory), a processor 102, and a computer program stored in the memory 101 and executable on the processor 102. When the processor 102 executes the program, it implements the steps of the particle analysis method based on particle size spectrum described in any of the possible implementations described above, which is equivalent to the particle analysis device based on particle size spectrum described above. Of course, the processor can also be used to process other data or perform other operations. The electronic device can be a PC, server, terminal, or other device.

[0215] like Figure 12 As shown, the electronic device may also generally include: a memory 103, a network interface 104, and an internal bus 105. In addition to these components, other hardware may also be included, which will not be described in detail.

[0216] It should be pointed out that the above-mentioned particle analysis device based on particle size spectrum can be implemented through software. As a device in a logical sense, it is formed by the processor 102 of the electronic device in which it is located reading the computer program instructions stored in the non-volatile memory into the memory 103 for execution.

[0217] Embodiments of the subject matter and functional operations described in this specification may be implemented in the following: digital electronic circuits, tangibly embodied computer software or firmware, computer hardware including the structures disclosed in this specification and their structural equivalents, or a combination of one or more of them. Embodiments of the subject matter described in this specification may be implemented as one or more computer programs, i.e., one or more modules of computer program instructions encoded on a tangible, non-transitory program carrier to be executed by a data processing device or to control the operation of the data processing device. Alternatively or additionally, the program instructions may be encoded on an artificially generated propagation signal, such as a machine-generated electrical, optical, or electromagnetic signal, which is generated to encode information and transmit it to a suitable receiver device for execution by the data processing device. The computer storage medium may be a machine-readable storage device, a machine-readable storage substrate, a random or serial access memory device, or a combination of one or more of them.

[0218] The processes and logic flows described in this specification can be performed by one or more programmable computers executing one or more computer programs to perform the corresponding functions by operating on input data and generating output. The processes and logic flows can also be performed by, and apparatus can be implemented as, special-purpose logic circuitry, such as an FPGA (field programmable gate array) or an ASIC (application-specific integrated circuit).

[0219] Computers suitable for executing computer programs include, for example, general-purpose and / or special-purpose microprocessors, or any other type of central processing unit. Typically, the central processing unit will receive instructions and data from a read-only memory and / or random access memory. The basic components of a computer include a central processing unit for implementing or executing instructions and one or more memory devices for storing instructions and data. Typically, a computer will also include one or more mass storage devices for storing data, such as magnetic disks, magneto-optical disks, or optical disks, or the computer will be operably coupled to such mass storage devices to receive data from them or to transmit data to them, or both. However, a computer does not necessarily have such devices. In addition, a computer can be embedded in another device, such as a mobile phone, a personal digital assistant (PDA), a mobile audio or video player, a game console, a global positioning system (GPS) receiver, or a portable storage device such as a universal serial bus (USB) flash drive, to name a few.

[0220] Computer-readable media suitable for storing computer program instructions and data include all forms of non-volatile memory, media, and storage devices, including, for example, semiconductor memory devices (e.g., EPROM, EEPROM, and flash memory devices), magnetic disks (e.g., internal hard disks or removable disks), magneto-optical disks, and CD-ROM and DVD-ROM disks. The processor and memory can be supplemented by, or incorporated in, special purpose logic circuitry.

[0221] Although this specification contains many specific implementation details, these should not be interpreted as limiting the scope of any invention or the scope of protection claimed, but are mainly used to describe the features of specific embodiments of specific inventions. Certain features described in multiple embodiments within this specification can also be implemented in combination in a single embodiment. On the other hand, the various features described in a single embodiment can also be implemented separately in multiple embodiments or in any suitable sub-combination. In addition, although the features can work in certain combinations as above and even initially claim protection, one or more features from the claimed combination can be removed from the combination in some cases, and the claimed combination can point to a sub-combination or a variation of the sub-combination.

[0222] Similarly, although operations are depicted in a particular order in the accompanying drawings, this should not be understood as requiring that these operations be performed in the particular order shown or performed sequentially, or that all illustrated operations be performed to achieve the desired results. In some cases, multitasking and parallel processing may be advantageous. In addition, the separation of various system modules and components in the above-described embodiments should not be understood as requiring such separation in all embodiments, and it should be understood that the described program components and systems can generally be integrated together in a single software product, or packaged into multiple software products.

[0223] Thus, specific embodiments of the subject matter have been described. Other embodiments are within the scope of the following claims. In some cases, the actions recited in the claims can be performed in a different order and still achieve the desired results. Furthermore, the processes depicted in the accompanying drawings do not necessarily require the particular order shown or sequential sequence to achieve the desired results. In some implementations, multitasking and parallel processing may be advantageous.

[0224] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or device that includes the element.

[0225] The foregoing is merely a detailed description of the present invention, intended to enable those skilled in the art to understand and implement the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein, but is to be construed in the widest manner consistent with the principles and novel features claimed herein.

Claims

1. A particle analysis device based on particle size spectrum, characterized in that: include: Beam forming and shaping unit, light source monitoring unit, stray light filtering unit, isolation unit, sample chamber, avalanche photodiode detector, photomultiplier tube detector and computing unit, among which, a beam generating and shaping unit, configured to excite a first linearly polarized light of the collimated light, adjust the polarization state of the first linearly polarized light into a second linearly polarized light having the same energy as the horizontal component and the vertical component, expand the second linearly polarized light, and then split the light according to a preset splitting ratio to obtain a first laser beam and a second laser beam, output the first laser beam to a light source monitoring unit, and converge the second laser beam to form a converged beam and output it to a stray light filtering unit, wherein the laser energy of the first laser beam is less than the laser energy of the second laser beam; a light source monitoring unit, configured to detect first light intensity information of the first laser beam, obtain first voltage information after conversion, and output the first voltage information to the calculation unit; A stray light filtering unit is used to split the converged light beam to form two parallel light beams along the X axis with equal spacing along the Y axis at the light focus in the sample chamber, filter out stray light from the parallel light beams, and output the parallel light beams after the stray light is filtered into the sample chamber through the isolation unit; The sample chamber is used to input the sample to be tested. When the sample to be tested falls to the focus of the two parallel light beams, it is illuminated by the two parallel light beams and diffusely reflected by the particles contained in the sample to be tested. The side diffusely reflected light beams are converged and input to the avalanche photodiode detector, and the forward diffusely reflected light beams are converged and input to the photomultiplier tube detector. an avalanche photodiode detector, configured to detect second light intensity information of the lateral diffusely reflected light beam, obtain second voltage information after transformation, and output the second voltage information to the calculation unit; a photomultiplier tube detector, used for detecting third light intensity information of the forward diffusely reflected light beam, obtaining third voltage information after transformation, and outputting the third voltage information to the calculation unit; The operation unit is used to receive the first light intensity information, the second light intensity information and the third light intensity information, perform coherent operations on the first light intensity information and the second light intensity information according to a preset coherent algorithm, and calculate the optimal APD coefficient using the following formula: ; Get the effective information of APD detection, where, is the APD coefficient, is the light scattering APD measurement value, is the APD measurement value of the light source, and, after performing coherent operation on the first light intensity information and the third light intensity information, the optimal PMT coefficient is calculated using the following formula: , get the effective information of PMT detection; where, is the PMT coefficient, is the light scattering PMT measurement value; Based on the signal-to-noise ratio of the APD detection effective information, it is determined whether to use the APD detection effective information or the PMT detection effective information for particle analysis. If the signal-to-noise ratio of the APD detection effective information is greater than or equal to the first signal-to-noise ratio threshold and the APD detection effective information is saturated, the APD saturation region median time difference method is used for detection. The particle analysis includes: particle concentration corresponding to the particle size distribution.

2. The particle analysis device based on particle size spectrum according to claim 1, characterized in that The beam forming and shaping unit includes: a laser, a pick, a first concave lens, a first convex lens, a beam splitter, a second convex lens, and a third convex lens, wherein: A laser, for exciting and outputting a first linearly polarized light of the collimated light; The paddle is connected to the laser, vertically receives the first linear polarized light emitted by the laser, adjusts the polarization state of the incident first linear polarized light so that the energy of the horizontal component is equal to the energy of the vertical component, obtains the second linear polarized light and outputs it; a first concave lens connected to the pick and receiving the second linearly polarized light output by the pick; a first convex lens connected to the first concave lens, the first concave lens and the first convex lens forming a beam expander for expanding the incident second polarized light to obtain expanded light; A beam splitter connected to the first convex lens is used to split the expanded light to obtain a first laser beam reflected from the beam splitter and a second laser beam penetrating the beam splitter. The first laser beam is incident on the second convex lens, converged by the second convex lens, and incident on the light source monitoring unit. The second laser beam is incident on the third convex lens. The laser energy of the first laser beam is much smaller than the laser energy of the second laser beam. The third convex lens is connected to the beam splitter and is used to converge the second laser beam in the Y-axis direction representing the energy of the vertical component to obtain a converged beam, which is incident on the stray light filtering unit, wherein the horizontal component energy and the vertical component energy of the polarization state of the converged beam are the same.

3. The particle analysis device based on particle size spectrum according to claim 1, characterized in that The stray light filtering unit includes: a beam splitting crystal, an aperture and an isolation unit, wherein: A beam splitter crystal is used to split the converged light beam to form two parallel beams along the X axis with equal spacing on the Y axis at the focus of the light beam. The X axis is the direction connecting the center point of the laser, the paddle, the concave lens, the first convex lens, the second convex lens, and the beam splitter crystal, and the Y axis is the direction perpendicular to the X axis. An aperture is used to perform multi-stage stray light filtering on the parallel light beam, and output the parallel light beam after the stray light is filtered into the sample chamber through the isolation unit; The isolation unit includes a first window mirror and a second window mirror. The first window mirror is connected to the aperture and is used to isolate the sample chamber from the beam generating and shaping unit, or the sample chamber from the stray light filtering unit, so as to prevent the gas to be detected with particulate matter in the sample chamber from contaminating the optical path environment of the beam generating and shaping unit and the stray light filtering unit. The second window mirror is used to isolate the sample chamber from the avalanche photodiode detector, and the sample chamber from the photomultiplier tube detector, respectively.

4. The particle analysis device based on particle size spectrum according to claim 3, characterized in that The aperture is a rectangular slit aperture, including a first-stage rectangular slit aperture, a second-stage rectangular slit aperture and a third-stage rectangular slit aperture connected in sequence, wherein the distance between adjacent rectangular slit diaphragms is 5 mm, and the slit width is 1 mm.

5. The particle analysis device based on particle size spectrum according to claim 1, characterized in that The sample chamber comprises: an aerodynamic gas nozzle, a second concave mirror, a focusing lens, a fourth convex lens and a chamber, wherein: The aerodynamic gas nozzle is used to input the sample to be tested into the chamber. When the sample to be tested falls to the focus of the light in the chamber, two parallel light beams passing through the stray light filtering unit illuminate the particles in the sample to be tested, and diffuse reflection occurs in the chamber to form a lateral diffuse reflection beam and a forward diffuse reflection beam; A second concave mirror is provided at a lateral position in the chamber to converge the received lateral diffuse reflection light beam of the sample to be measured to the focusing lens; A focusing lens is used to focus the lateral diffusely reflected light collected by the second concave mirror and input the focused light into the avalanche photodiode detector; The fourth convex lens is arranged at a forward position in the chamber, and converges the forward diffuse reflection light beam received from the sample to be tested to the photomultiplier tube detector.

6. The particle analysis device based on particle size spectrum according to any one of claims 1 to 5, characterized in that: Also includes: The filter assembly is used to perform extinction processing on the other parallel light beams among the two parallel light beams except for the parallel light beams irradiating the particles in the sample to be measured.

7. The particle analysis device based on particle size spectrum according to claim 6, characterized in that The filter assembly is arranged in the sample chamber and includes: a first neutral density filter and a second neutral density filter, wherein: The first neutral density filter is installed in the optical path of the parallel light beam at a preset Brewster angle, absorbs the incident horizontally polarized parallel light beam and part of the vertically polarized parallel light beam, and reflects the other part of the vertically polarized parallel light beam that is not absorbed to the second neutral density filter; The second neutral density filter is arranged spatially relative to the first neutral density filter and rotated 90 degrees in the vertical light path propagation direction to absorb another part of the incident vertically polarized parallel light beam.

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