Aerosol particle scattering characteristic experimental platform and experimental method based on Pockels effect

Abstract

The invention relates to an aerosol particle scattering characteristic experimental platform and experimental method based on a Pockels effect, and belongs to the technical field of optical measurement. The experimental platform comprises an optical platform, an aerosol particle transport system, an optical path system and a data processing system, the aerosol particle conveying system comprises a combustion chamber, a dust aerosol generator, a water mist aerosol generator, a pipeline and an aerosol jet hole; the combustion chamber, the dust aerosol generator and the water mist aerosol generator are all placed outside a room where the optical platform is located, and the light path system is placed on the indoor optical platform; all parts of the data processing system are placed inside or on the top of the cabinet, and the cabinet is close to the optical platform. According to the aerosol particle scattering characteristic experiment platform based on the Pockels effect, the electro-optical modulator based on the Pockels effect and the phase-locked demodulation technology are used, the Mueller matrix measurement time can be shortened, and the measurement precision is improved.

Description

Technical Field

[0001] This invention belongs to the field of optical measurement technology, specifically relating to an experimental platform and method for the scattering characteristics of aerosol particles based on the Pockels effect. Background Technology

[0002] Fire, as a sudden disaster, is extremely destructive, threatening not only people's lives but also potentially causing huge economic losses. Therefore, fire prevention and early detection are crucial. Currently, one of the main means of fire prevention is installing fire detectors for real-time fire monitoring. Among various fire detectors, photoelectric fire detectors are widely used due to their high sensitivity. However, existing photoelectric fire detectors are mainly based on the principle of light scattering, which has certain limitations in practical applications. These detectors are prone to false alarms under aerosol interference in non-fire conditions such as dust and water mist, causing unnecessary trouble and wasting resources. False alarms not only disrupt normal life and work but may also lead to excessive consumption of fire-fighting resources, reducing the reliability and effectiveness of fire detectors. Improving the accuracy and false alarm resistance of fire detectors can be achieved through in-depth research into the scattering characteristics of particles. Most existing technologies improve the false alarm resistance of photoelectric smoke detectors by obtaining the scattering asymmetry ratio through multi-wavelength, multi-scattering-angle optical paths. However, this method relies on the size difference between fire smoke particles and interfering aerosol particles to affect the intensity of scattered light. Due to the wide particle size distribution of fire smoke particles, this method still has a false alarm rate. Summary of the Invention

[0003] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0004] An experimental platform for the scattering characteristics of aerosol particles based on the Pockels effect includes: an optical platform, an aerosol particle transport system, an optical path system, and a data processing system;

[0005] The aerosol particle transport system includes a combustion chamber, a dust aerosol generator, a water mist aerosol generator, pipes, and aerosol jet orifices. The combustion chamber, dust aerosol generator, and water mist aerosol generator are all located outside the room where the optical platform is located. Combustion of combustibles in the combustion chamber generates fire smoke aerosol particles. The dust aerosol generator and water mist aerosol generator respectively generate dust and water mist interfering aerosol particles. The fire smoke aerosol particles, dust, and water mist interfering aerosol particles enter the pipes, are transported through the bottom of the optical platform, and are ejected from the aerosol jet orifices on the optical platform to the light scattering center. The optical path system is located on the indoor optical platform. All components of the data processing system are located inside or on top of a cabinet, which is close to the optical platform.

[0006] The optical path system includes a polarizer, an analyzer, a PMT (partial magnetic resonance imaging) module, and a rotating ring-track module. The rotating ring-track module is placed on an optical platform with the aerosol jet aperture as its center. The polarizer is positioned at the front end of the rotating ring-track module, with its optical axis aligned along the 0° scattering angle. During a single operation, the analyzer rapidly rotates from the 0° direction to the 180° direction of the rotating ring-track module, measuring the scattering characteristic signal within the 0°~180° scattering angle range. The PMT module is fixed at the -30° scattering angle direction of the rotating ring-track module and is used for measurement... The scattering characteristic signal is measured in the direction of a scattering angle of -30°. The polarization analyzer is set on the rotating arm of the circular track rotating module and moves with the rotating arm on the circular track. The polarization structure includes a laser, a first polarizer, and an electro-optic modulator. The laser, the first polarizer, and the electro-optic modulator are respectively embedded in a fixed frame, a first step motor rotating seat, and an adjustable bracket. The optical axes of the laser, the first polarizer, and the electro-optic modulator are located on a straight line, and the straight line is directly opposite the aerosol jet hole. The first polarizer and the electro-optic modulator modulate the polarization state of the light source emitted by the laser to obtain the polarization characteristics of light scattering from aerosol particles.

[0007] An experimental method for the scattering properties of aerosol particles based on the Pockels effect, used in the aforementioned experimental platform for the scattering properties of aerosol particles based on the Pockels effect, includes:

[0008] Step 1: Perform position calibration of optical components: laser, first polarizer, electro-optic modulator, quarter-wave plate, second polarizer, PMT (Position Detector), and PMT (Position Detector).

[0009] Step 2: Adjust the optical axis orientation of the optical components: laser, first polarizer, electro-optic modulator, quarter-wave plate, second polarizer, PMT (probe sensor), and PMT (probe detector), and begin measuring the scattering characteristic signal;

[0010] Step 3: Demodulate the first and second harmonics of the scattered light harmonic signal measured by the detector PMT, as well as the DC signal data measured by the detector PMT and the monitor PMT, and import them into the computer for processing; By comparing and analyzing the Mueller matrix elements of different types of aerosols, the differences in scattering polarization characteristics between fire smoke aerosol particles and interference aerosol particles are obtained, and then the method for distinguishing between the two is summarized.

[0011] The present invention has the following beneficial effects:

[0012] (1) The experimental platform for aerosol particle scattering characteristics based on the Pockels effect of the present invention uses an electro-optic modulator based on the Pockels effect and a phase-locked demodulation technique, which can shorten the measurement time of the Mueller matrix and improve the measurement accuracy.

[0013] (2) The optical components of the experimental platform for aerosol particle scattering characteristics based on the Pockels effect of the present invention are all adjusted automatically by precise mechanical control, so as to avoid the angle and displacement deviation caused by manual adjustment, which leads to the measurement error of Mueller matrix data.

[0014] (3) The experimental method for aerosol particle scattering characteristics based on the Pockels effect (anti-interference method for fire smoke detection based on polarization characteristics) of this invention measures all Mueller matrix elements of aerosol particles by combining eight optical elements at different angles. It deeply explores the influence of aerosol particle morphology, size and refractive index on light polarization characteristics. Based on the differences in light scattering polarization characteristics of different aerosol particles, it can distinguish between fire smoke particles and interfering aerosol particles, providing a theoretical basis for the design of detector anti-false alarm performance.

[0015] (4) The experimental platform for aerosol particle scattering characteristics based on the Pockels effect of the present invention uses a high-precision servo motor to drive the rotating arm, which can complete the range of movement from 0° to 180° on the rotating track within 2 seconds. Its angular resolution can reach 0.001°, and it can generate 1000 pulse signals within a 1° range to trigger phase-locked operation, thereby achieving accurate capture and demodulation of scattering signals within the scattering angle range of 0° to 180°.

[0016] (5) The experimental platform for aerosol particle scattering characteristics based on the Pockels effect of the present invention adds another monitor PMT (monitor PMT26) at the -30° scattering angle position, which can eliminate the influence of the fluctuation of smoke particles on the measurement of scattered light at different angles. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the experimental platform for aerosol particle scattering characteristics based on the Pockels effect of the present invention, wherein 1-optical platform, 2-aerosol particle transport system, 5-combustion chamber, 6-dust aerosol generator, 7-water mist aerosol generator, 8-pipeline, 9-aerosol jet hole, 10-exhaust fan, 11-smoke hood, 12-exhaust duct, 34-computer, 39-cabinet;

[0018] Figure 2This diagram illustrates the optical path system and data processing system of the experimental platform for aerosol particle scattering characteristics based on the Pockels effect of the present invention. In the diagram, 3-optical path system, 4-data processing system, 9-aerosol jet aperture, 13-polarizing structure, 14-analyzing structure, 15-monitor PMT module, 16-ring track rotation module, 17-laser, 35-fixed frame, 18-first polarizer, 36-first stepper motor rotating seat, 19-electro-optic modulator, 37-adjustable bracket, 20-1 / 4 waveplate, 21-second polarizer, 22-first electric displacement stage, 23-second electric displacement stage, 38-second stepper motor rotating seat, 24-detector PMT, 25-first dovetail rail, 26-monitor PMT, 27-second dovetail rail, 28-ring track, 29-servo motor, 30-rotating arm, 31-signal generator, 32-lock-in amplifier, 33-data acquisition card, and 34-computer. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0020] According to Maxwell's electromagnetic propagation theory, light scattering from microparticles should include three pieces of information: intensity, polarization, and phase. While the phase information of the scattered light is difficult to measure, its intensity and polarization information are relatively easy to obtain. The polarization information of the scattered light can reflect in detail the influence of parameters such as the shape, size, and refractive index of the microparticles on the light scattering process, providing an important basis for distinguishing different microparticles. By measuring the elements of the Mueller matrix, which reflects the polarization characteristics of particle light scattering, a scientific basis can be provided for distinguishing different types of aerosols, as different aerosol particles have different Mueller matrix characteristics.

[0021] This invention applies Mueller matrix measurement technology to the field of fire detection. By deeply studying the scattering characteristics of aerosol particles, it provides a theoretical and data foundation for improving the false alarm resistance of fire detectors. This invention can accurately measure the Mueller matrix elements reflecting the scattering characteristics of aerosol particles, thereby distinguishing between smoke generated by fire and other types of aerosol interference. This provides a scientific basis for the design of fire detectors to resist false alarms, improving the accuracy and reliability of fire detector detection.

[0022] This invention provides an experimental platform (or experimental platform) for the scattering characteristics of aerosol particles based on the Pockels effect, comprising: an optical platform 1, an aerosol particle transport system 2, and an optical path system 3. Figure 2 (shown) and data processing system 4 ( Figure 2 (As shown). The aerosol particle transport system 2 includes a combustion chamber 5, a dust aerosol generator 6, a water mist aerosol generator 7, a pipe 8, and an aerosol jet orifice 9. The combustion chamber 5, the dust aerosol generator 6, and the water mist aerosol generator 7 are all placed outside the room where the optical platform 1 is located. Combustion of combustibles in the combustion chamber 5 produces fire smoke aerosol particles. The dust aerosol generator 6 and the water mist aerosol generator 7 respectively produce dust and water mist to interfere with the aerosol particles. The aerosol particles generated by these three components enter the pipe 8, are transported through the bottom of the optical platform 1, and are ejected from the aerosol jet orifice 9 on the optical platform 1 to the light scattering center. The optical path system 3 is placed on the indoor optical platform 1. All components of the data processing system 4 are placed inside or on top of the cabinet 39, which is close to the optical platform 1.

[0023] Figure 1 This is a schematic diagram of the experimental platform for aerosol particle scattering characteristics based on the Pockels effect of the present invention. The aerosol particle transport system 2 further includes an exhaust fan 10, a smoke hood 11, and an exhaust duct 12. The smoke hood 11 is located directly above the aerosol jet hole 9, and the exhaust fan 10 inside provides exhaust power. Aerosol particles entering the smoke hood 11 are transported to a safe outdoor area through the exhaust duct 12.

[0024] Figure 2 This is a schematic diagram of the optical path system and data processing system of the experimental platform for aerosol particle scattering characteristics based on the Pockels effect of the present invention. The optical path system 3 is placed on the optical platform 1, and all components of the data processing system 4 are placed inside or on top of the cabinet 39, which is located close to the optical platform 1.

[0025] The optical path system 3 includes a polarizing structure 13, an analyzing structure 14, a PMT (photomultiplier tube) module 15, and a circular track rotation module 16. The circular track rotation module 16 is placed on the optical platform 1 with the aerosol jet hole 9 as its center. The polarizing structure 13 is located at the front end of the circular track rotation module 16, with its optical axis aligned along the 0° scattering angle direction. During a single operation, the analyzing structure 14 rapidly rotates from the 0° direction to the 180° direction of the circular track rotation module 16, measuring the scattering characteristic signal within the 0°~180° scattering angle range. The PMT module 15 is fixed at the -30° scattering angle direction of the circular track rotation module 16, used to measure the scattering characteristic signal in the -30° scattering angle direction. The analyzing structure 14 is mounted on the rotating arm 30 of the circular track rotation module 16 and moves with the rotating arm 30 on the circular track 28, with a movement range of 0~180° scattering angle.

[0026] The circular track rotation module 16 includes a circular track 28, a servo motor 29, and a rotating arm 30. The servo motor 29 drives the rotating arm 30 to rotate along the circular track 28 within a scattering angle range of 0° to 180°. The servo motor 29 is connected to a lock-in amplifier 32. The servo motor 29 has a resolution of up to 0.001° and can generate 1000 pulse signals within a 1° range to trigger the lock-in amplifier 32 to work, thereby achieving precise capture and demodulation of scattered signals within the scattering angle range of 0° to 180°.

[0027] The polarization structure 13 includes three optical elements: a laser 17, a first polarizer 18, and an electro-optic modulator 19. These three optical elements are respectively embedded in a fixed frame 35, a first stepper motor rotating base 36, and an adjustable bracket 37. The optical axes of the three optical elements are aligned on a straight line, directly opposite the aerosol jet aperture 9. The first polarizer 18 and the electro-optic modulator 19 can modulate the polarization state of the light emitted by the laser 17, thereby exploring the polarization characteristics of light scattering from aerosol particles.

[0028] The polarizer 14 includes three optical elements: a quarter-wave plate 20, a second polarizer 21, and a detector PMT 24. The quarter-wave plate 20 is fixed on the slide plate of the first motorized displacement stage 22 and can move laterally along the first motorized displacement stage 22, thereby enabling the quarter-wave plate 20 to automatically exit or return to the optical path. The second polarizer 21 is embedded in the second stepper motor rotating seat 38, which is fixed on the second motorized displacement stage 23 and can move laterally along the second motorized displacement stage 23, thereby enabling the second polarizer 21 to automatically exit or return to the optical path. The first motorized displacement stage 22, the second motorized displacement stage 23, and the detector PMT 24 are fixed on the first dovetail guide rail 25 in a sequence that moves away from the aerosol jet hole 9. The first dovetail guide rail 25 is fixed on the rotating arm 30 and rotates along the annular track 28 with the rotating arm 30.

[0029] The PMT module 15 includes a PMT (photomultiplier tube) 26 and a second dovetail rail 27. The PMT 26 is fixed on the second dovetail rail 27, and the feet of the second dovetail rail 27 are fixed on the optical platform 1. The two feet span the annular track 28 in the direction of scattering angle -30°.

[0030] The data processing system 4 includes a signal generator 31, a lock-in amplifier 32, a data acquisition card 33, and a computer 34. The signal generator 31 modulates the electro-optic modulator 19 by applying different forms of voltage. Simultaneously, the signal generator 31 provides a reference voltage to the lock-in amplifier 32. The lock-in amplifier 32 demodulates the scattered light harmonic signal measured by the detector PMT24 based on the reference voltage. The demodulated signal is sent to the computer 34 for processing and analysis. The signals measured by the detector PMT24 and the monitor PMT26 are converted by the data acquisition card 33 and then sent to the computer 34. The computer 34 controls the first electric displacement stage 22, the second electric displacement stage 23, the first stepper motor rotary seat 36, the second stepper motor rotary seat 38, and the servo motor 29 through software, achieving automated task control.

[0031] This invention also provides an experimental method (or experimental method) for the scattering characteristics of aerosol particles based on the Pockels effect, used in the aforementioned experimental platform for the scattering characteristics of aerosol particles based on the Pockels effect, comprising:

[0032] The light source emitted by the laser 17 enters the electro-optic modulator 19 after passing through the first polarizer 18. The light modulated by the electro-optic modulator 19 is scattered by the aerosol particles ejected from the aerosol jet hole 9. The scattered light enters the detector PMT24 after passing through the quarter-wave plate 20 and the second polarizer 21. The detector PMT24 detects the intensity signal of the scattered light. The intensity signal of the scattered light is processed by the lock-in amplifier 32 and the data acquisition card 33 and then imported into the computer 34 for calculation and analysis.

[0033] The experimental method specifically includes the following steps:

[0034] Step 1: Perform position calibration of optical components: laser 17, polarizer (first polarizer 18), electro-optic modulator 19, quarter-wave plate 20, analyzer (second polarizer 21), and PMT (monitor PMT26, detector PMT24).

[0035] Step 2: Adjust the optical axis direction of the above optical components and begin measurement;

[0036] Step 3: Import the amplitudes of the first-order harmonic and second-order harmonic signals and the DC signal into the computer 34 for processing; by comparing and analyzing the Mueller matrix elements of different types of aerosols, the differences in scattering polarization characteristics between fire smoke aerosol particles and interference aerosol particles are obtained, and then the method for distinguishing the two is summarized.

[0037] By combining the eight angles of various optical elements, all Mueller matrix elements that can reflect the scattering polarization characteristics of aerosol particles can be determined. This allows us to explore the influence of particle morphology, size, and refractive index on light scattering polarization characteristics, thereby distinguishing different particles.

[0038] The electro-optic modulator 19 is based on the Pockels effect. The experimental platform uses the Pockels effect-based electro-optic modulator 19 to modulate the polarization state of the incident light. Changing the magnitude of the electric field voltage applied to the electro-optic modulator 19 changes the phase difference between the two perpendicular components of the incident photoelectric field, and the magnitude of the phase delay between the two components is proportional to the voltage applied to the electro-optic modulator 19. The modulated incident light is scattered by aerosol particles, and the scattered light passes through a quarter wave plate 20 and a second polarizer 21. The detector PMT 24 detects the light scattering signal, and the light scattering signal is processed by a lock-in amplifier 32 to obtain DC, first-order harmonic, and second-order harmonic components, each corresponding to a different Mueller matrix element.

[0039] To eliminate the influence of smoke particle fluctuations on the measurement of scattered light at different angles, a monitor PMT26 was added to the experimental platform to measure the intensity of scattered light at a fixed scattering angle. Changes in this intensity reflect the fluctuations in smoke particle flow, and the monitor PMT26 serves to "monitor" the stability of the smoke particle stream. The entire experimental platform uses two photoelectric receiving devices (detector PMT24 and monitor PMT26, both used for detecting scattered signals). The monitor PMT26 only needs to measure the scattered light intensity to normalize the signal value measured by detector PMT24.

[0040] The debugging of the experimental platform includes: adjusting the relative positions between the laser 17, the first polarizer 18 and the electro-optic modulator 19 to maximize the transmittance of the emitted light through the electro-optic modulator 19, and adjusting the spatial orientation of the detector PMT24 and the aerosol jet hole 9 so that the detector PMT24 is always aligned with the center of the aerosol jet hole 9 when the rotating arm 30 rotates.

[0041] When measuring the Mueller matrix, the Stokes vectors of the incident light are used for multiple different known polarization states. Measure the Stokes vector of its scattered light Thus, we obtain the linear equation system (Equation 1) concerning each element of the Mueller matrix. By solving this linear equation system, we obtain the values ​​of each element of the Mueller matrix. In this invention, a first polarizer 18, an electro-optic modulator 19, a quarter-wave plate 20, and a second polarizer 21 are used to polarize the optical path. The optical path transmission equation is as shown in Equation (1):

[0042] (1)

[0043] In the formula, The vector is a constant; the 4x1 vectors on both sides of the equation are the Stokes vectors of the incident light and the scattered light, respectively. The total intensity of the beam. Due to the difference between horizontal and vertical polarization, The difference in light intensity between the linearly polarized components at 45° and 135° is considered. This represents the difference in light intensity between the right-hand circularly polarized and left-hand circularly polarized components. This represents the 4×4 Mueller matrix of the aerosol particles. , , , These are the Mueller matrices of the second polarizer 21, the quarter-wave plate 20, the electro-optic modulator 19, and the first polarizer 18, respectively. , , , These are the angles between the optical axis directions of the second polarizer 21, the quarter-wave plate 20, the electro-optic modulator 19, and the first polarizer 18 and the reference plane (usually the scattering plane in scattering measurements). For the scattering angle, with Figure 2 With a 0° scattering angle as the reference, The total intensity of the incident light beam. Due to the difference in horizontal and vertical polarization of the incident light, The difference in incident light intensity between the linearly polarized components at 45° and 135° is considered. This represents the difference in incident light intensity between the right-handed and left-handed circularly polarized components.

[0044] The Mueller matrices of each optical element are shown in equations (2), (3), and (4), respectively:

[0045] (2)

[0046] (3)

[0047] (4)

[0048] in, =cos2γ; =sin2γ, where γ is the angle between the optical axis directions of the second polarizer 21, quarter-wave plate 20, electro-optic modulator 19, and first polarizer 18 and the reference plane (usually the scattering plane in scattering measurements).

[0049] The electro-optic modulator 19 is the core of the entire experimental platform. It operates based on the linear electro-optic effect of crystals, also known as the Pockels effect, which describes the birefringence of certain crystals after a voltage is applied. If the voltage applied to the crystal varies sinusoidally with time, the phase difference between the horizontal and vertical components of the incident photoelectric field vector passing through the crystal will be... It also varies sinusoidally with time, that is:

[0050] (5)

[0051] in, Let be the phase difference between the horizontal and vertical components of the incident photoelectric field vector. The maximum phase difference between the horizontal and vertical components of the incident photoelectric field vector. The angular frequency of the phase difference change. For time.

[0052] for and Expanding using the first type of Bessel function, we get:

[0053] (6)

[0054] (7)

[0055] in, For the summation index, For the first The relative amplitude of each harmonic. The relative amplitude of the 0th harmonic. For the first The relative amplitude of each harmonic. For summation index. The relative amplitude of the nth harmonic is referred to here, where the Bessel function acts as a weighting factor.

[0056] By adjusting the amplitude of the modulation voltage of the electro-optic modulator 19, the maximum phase difference it generates can be adjusted accordingly. (The maximum phase difference between the horizontal and vertical components of the incident photoelectric field vector) is the first zero of the Bessel function, i.e., when When =2.40483, =0. Therefore:

[0057] (8)

[0058] (9)

[0059] , These are the relative amplitudes of the first harmonic (1st order harmonic) and the second harmonic (2nd order harmonic), respectively.

[0060] (10)

[0061] (11)

[0062] Substituting equations (2), (3), and (4) into equation (1), and omitting the third and higher harmonics in the expansions of equations (8) and (9), the scattered light intensity signal measured by the detector PMT24 can be obtained after simplification, as shown in equation (13):

[0063] (12)

[0064] In equation (12), It is a constant and is related to the Stokes parameters of the incident light and the angles, modulation amplitudes, and other parameters of all optical elements on optical platform 1; This represents the DC component (i.e., light intensity) of the scattered light signal. It is the first harmonic of the scattered light signal; It is the second harmonic of the scattered light signal. , and It contains Mueller matrix elements of aerosol particles. Among them, the DC component of the scattered light signal... After DC amplification, the first harmonic of the scattered light signal is directly measured via data acquisition card 33. With second-order harmonics Then synchronous acquisition is required through lock-in amplifier 32.

[0065] The parts of this invention not described in detail are well-known to those skilled in the art. The embodiments described above are merely preferred embodiments of the invention, and do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Various modifications and improvements to the technical solutions of this invention made by those skilled in the art without departing from the spirit of the invention should fall within the protection scope defined by the claims of this invention.

Claims

1. An experimental platform for the scattering characteristics of aerosol particles based on the Pockels effect, characterized in that, include: Optical platform, aerosol particle transport system, optical path system, and data processing system; The aerosol particle transport system includes a combustion chamber, a dust aerosol generator, a water mist aerosol generator, pipes, and aerosol jet orifices. The combustion chamber, dust aerosol generator, and water mist aerosol generator are all located outside the room where the optical platform is located. Combustion of combustibles in the combustion chamber generates fire smoke aerosol particles. The dust aerosol generator and water mist aerosol generator respectively generate dust and water mist interfering aerosol particles. The fire smoke aerosol particles, dust, and water mist interfering aerosol particles enter the pipes, are transported through the bottom of the optical platform, and are ejected from the aerosol jet orifices on the optical platform to the light scattering center. The optical path system is located on the indoor optical platform. All components of the data processing system are located inside or on top of a cabinet, which is close to the optical platform. The optical path system includes a polarizer, an analyzer, a PMT (partial magnetic resonance imaging) module, and a rotating ring-track module. The rotating ring-track module is placed on an optical platform with the aerosol jet aperture as its center. The polarizer is positioned at the front end of the rotating ring-track module, with its optical axis aligned along the 0° scattering angle. During a single operation, the analyzer rapidly rotates from the 0° direction to the 180° direction of the rotating ring-track module, measuring the scattering characteristic signal within the 0°~180° scattering angle range. The PMT module is fixed at the -30° scattering angle direction of the rotating ring-track module and is used for measurement... The scattering characteristic signal is measured in the direction of a scattering angle of -30°. The polarization analyzer is set on the rotating arm of the circular track rotating module and moves with the rotating arm on the circular track. The polarization structure includes a laser, a first polarizer, and an electro-optic modulator. The laser, the first polarizer, and the electro-optic modulator are respectively embedded in a fixed frame, a first step motor rotating seat, and an adjustable bracket. The optical axes of the laser, the first polarizer, and the electro-optic modulator are located on a straight line, and the straight line is directly opposite the aerosol jet hole. The first polarizer and the electro-optic modulator modulate the polarization state of the light source emitted by the laser to obtain the polarization characteristics of light scattering from aerosol particles.

2. The experimental platform for aerosol particle scattering characteristics based on the Pockels effect according to claim 1, characterized in that, The circular track rotation module includes a circular track, a servo motor, and a rotating arm; the servo motor drives the rotating arm to rotate along the circular track within a scattering angle range of 0° to 180°; the servo motor is connected to a lock-in amplifier.

3. The experimental platform for aerosol particle scattering characteristics based on the Pockels effect according to claim 2, characterized in that, The polarization analyzer includes three optical components: a quarter-wave plate, a second polarizer, and a detector PMT. The quarter-wave plate is fixed on the slide plate of the first motorized displacement stage and can move laterally along the first motorized displacement stage, thereby enabling the quarter-wave plate to automatically exit or return to the optical path. The second polarizer is embedded in the second stepper motor rotating seat, which is fixed on the second motorized displacement stage and can move laterally along the second motorized displacement stage, enabling the second polarizer to automatically exit or return to the optical path. The first motorized displacement stage, the second motorized displacement stage, and the detector PMT are fixed on the first dovetail guide rail in order of gradually moving away from the aerosol jet orifice. The first dovetail guide rail is fixed on the rotating arm and rotates along the circular track with the rotating arm.

4. The experimental platform for aerosol particle scattering characteristics based on the Pockels effect according to claim 3, characterized in that, The monitor PMT module includes a monitor PMT and a second dovetail rail. The monitor PMT is fixed on the second dovetail rail, and the feet of the second dovetail rail are fixed on the optical platform. The two feet span the annular rail in the direction of scattering angle -30°.

5. The experimental platform for aerosol particle scattering characteristics based on the Pockels effect according to claim 4, characterized in that, The data processing system includes a signal generator, a lock-in amplifier, a data acquisition card, and a computer. The signal generator modulates the electro-optic modulator by applying different forms of voltage, and at the same time, the signal generator provides a reference voltage to the lock-in amplifier. The lock-in amplifier demodulates the scattered light harmonic signal measured by the detector PMT according to the reference voltage. The demodulated signal is sent to the computer for processing and analysis. The DC signals measured by the detector PMT and the monitor PMT are converted into data by the data acquisition card and then sent to the computer. The computer controls the first electric displacement stage, the second electric displacement stage, the first stepper motor rotary seat, the second stepper motor rotary seat, and the servo motor to realize automated task control.

6. The experimental platform for aerosol particle scattering characteristics based on the Pockels effect according to claim 5, characterized in that, The light source emitted by the laser enters the electro-optic modulator after passing through the first polarizer. The light modulated by the electro-optic modulator is scattered by the aerosol particles ejected from the aerosol jet orifice. The scattered light enters the detector PMT after passing through the quarter-wave plate and the second polarizer. The detector PMT detects the intensity signal of the scattered light. The intensity signal of the scattered light is processed by the lock-in amplifier and the data acquisition card and then imported into the computer for calculation and analysis.

7. The experimental platform for aerosol particle scattering characteristics based on the Pockels effect according to claim 6, characterized in that, By changing the magnitude of the electric field voltage applied to the electro-optic modulator, the phase difference between the two perpendicular components of the incident photoelectric field is changed, and the magnitude of the phase delay amplitude of the two components is proportional to the voltage applied to the electro-optic modulator. The modulated incident light is scattered by aerosol particles, and the scattered light passes through a quarter wave plate and a second polarizer. The detector PMT detects the light scattering signal, and the light scattering signal is processed by a lock-in amplifier to obtain DC, first-order harmonic, and second-order harmonic components. The DC, first-order harmonic, and second-order harmonic components all correspond to different Mueller matrix elements.

8. The experimental platform for aerosol particle scattering characteristics based on the Pockels effect according to claim 7, characterized in that, The servo motor is connected to a lock-in amplifier. The servo motor has a resolution of 0.001° and can generate 1,000 pulse signals within a 1° range to trigger the lock-in amplifier to work, thereby achieving accurate capture and demodulation of scattered signals within the scattering angle range of 0° to 180°.

9. The experimental platform for aerosol particle scattering characteristics based on the Pockels effect according to claim 7, characterized in that, The Mueller matrix is ​​measured by considering the Stokes vectors of the incident light for multiple different known polarization states. Measure the Stokes vector of its scattered light This yields a system of linear equations relating to the elements of the Mueller matrix. By solving this system of linear equations, the values ​​of each element of the Mueller matrix can be obtained. Using the second polarizer, quarter-wave plate, electro-optic modulator, and first polarizer at eight different angle combinations, determine all Mueller matrix elements of the aerosol particles.

10. An experimental method for the scattering characteristics of aerosol particles based on the Pockels effect, used in the experimental platform for the scattering characteristics of aerosol particles based on the Pockels effect as described in any one of claims 5 to 9, characterized in that, include: Step 1: Perform position calibration of optical components: laser, first polarizer, electro-optic modulator, quarter-wave plate, second polarizer, PMT (Position Detector), and PMT (Position Detector). Step 2: Adjust the optical axis orientation of the optical components: laser, first polarizer, electro-optic modulator, quarter-wave plate, second polarizer, PMT (probe sensor), and PMT (probe detector), and begin measuring the scattering characteristic signal; Step 3: Demodulate the first and second harmonics of the scattered light harmonic signal measured by the detector PMT, as well as the DC signal data measured by the detector PMT and the monitor PMT, and import them into the computer for processing; By comparing and analyzing the Mueller matrix elements of different types of aerosols, the differences in scattering polarization characteristics between fire smoke aerosol particles and interference aerosol particles are obtained, and then the method for distinguishing between the two is summarized.

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