Research On The Key Technology Of Atmospheric Particle Size Spectrum Measurement Based On Mie Scattering

Atmospheric particles can form a relatively stable suspension system in the air,and their pollution often spreads over a large area.The requirements for accuracy and efficiency of pollution particle measurement in air media are increasing in many fields,and it is important to study the light scattering characteristics of particles,explore the mapping law of interaction between physical light field and particles,and invert to obtain the atmospheric particle size spectrum distribution in the field of optical remote sensing and environmental measurement.In this paper,the objective is to develop a high-efficiency atmospheric particle size spectrum measurement test system.Based on Mie scattering theory,a spherical atmospheric particle model is constructed using MATLAB.Under the incident light condition of 0.65μm wavelength,the extinction,scattering and absorption efficiency as well as the scattering phase function of particles with diameters from 0.1μm to 50μm are simulated and analyzed to study the effects of the size parameters and complex refractive index of particles on the angular distribution of scattered light energy,and it is concluded that the detector placed at90° laterally facilitates the differentiation of scattered light energy of different size particles.The measurement system adopts the light scattering method to measure the atmospheric particles.After the analysis of the structure of the photosensitive area,the optimized design based on ZEMAX uses a lens set consisting of a spherical lens,an aspherical lens and a cylindrical mirror to collimate-shape the incident light,and the output line spot size is3.2mm×0.028 mm,which ensures a uniform incident light energy,while a narrower spot improves the incident light density and counting The voltage pulse signal measurement circuit design adopts junction type field effect transistor(JFET)three-stage amplification and comparison circuit,and the zero bias source of JFET is grounded with the in-phase and antiphase amplification circuit,which suppresses the noise interference of the system and improves the small signal amplification and detection capability.Finally,Lab VIEW is used to write the upper computer program to collect and process the data collected by the test system to obtain the atmospheric particle size and particle size spectrum distribution.On this basis,the data measured by the atmospheric particle size spectrometry test system were verified and analyzed,and the error of particle size distribution for 0.4μm and0.6μm size particles were 6.38% and 11.76% respectively,which met the requirements of domestic standards.The results were compared and analyzed with similar benchmark products,and the efficiency of the atmospheric particle size measurement test system for0.3μm particles was improved by 244.5%,achieving the design goal of accuracy and efficiency of measurement results,and proving that the research content of this paper has certain reference value for improving the efficiency of atmospheric particle size measurement.In this paper,the current research status of particle size measurement and spectral distribution description is firstly studied,and the main research content of this paper is introduced;Chapter 2 studies a variety of common particle measurement methods and analyzes their advantages and disadvantages,then the principle of atmospheric particle measurement based on Mie scattering theory is studied,and the effects of atmospheric particle size,complex refractive index and incident light wavelength on the particle light scattering characteristics are simulated and analyzed;Chapter 3 makes an overall structural design of the Chapter 3 presents the overall structure design of the atmospheric particle size measurement system,including the selection of laser light source and detection unit,the optimization of photosensitive area spot size and particle concentration of sampling airflow,the design of voltage pulse detection and comparison circuit,etc.Chapter 4 uses Lab VIEW to write the host computer program to collect and process the data collected by the atmospheric particle size measurement test system,count and plot the particle size distribution for different sizes of atmospheric particles.Finally,the measurement results are compared and analyzed with the same type of products to verify that the research content of this paper can help improve the efficiency of atmospheric particle size spectrum measurement.