Measurement Of Diameter Distribution Of Particles In Cloud Chamber Based On Interferometric Particle Imaging

Clouds are aerosols composed of liquid droplets,ice crystals and snowflakes suspendedin the air.The study of cloud particle size distribution and particle concentration is of great significance for studying cloud evolution and guiding weather modification.Interferometric Particle Imaging(IPI)is a particle measurement technology based on particle scattering theory.Using this technology to measure cloud particle field,the particle size of each cloud particle can be obtained.The calculation formulas of spherical particles are analyzed by the phase difference method of scattering light and the transfer matrix method respectively.Taking the bubble particle field as an example,the ability of IPI system to measure the wide particle size distribution particle field is validated in the laboratory.A cloud particle measurement instrument is built to detect the warm cloud particle field in the cloud chamber.Main work of this paper:1.In a typical interferometric particle imaging system,the theoretical analysis of the IPI technique is carried out.The relationship between the particle interferometric image and the particle diameter is established by using the scattered light phase difference method and transfer matrix methodrespectively,then the two methods are compared.2.An image processing program for cloud particle size measurement is developed by OPENCV to locate the interference fringe circle and extract the fringe frequency.The fringe circle location algorithm based on template matching algorithm and the fringe frequency extraction algorithm based on 2D Fourier transform and Gauss interpolation are analyzed.A semi-automatic fringe frequency extraction algorithm is proposed for cloud particle image processing.For the high quality interference fringe circle,the method of automatic location is used,and for the poor image quality interference fringe circle,the method of manual interception is used.3.The detection ability of IPI system for particle field with wide size distribution was verified in laboratory.The bubble particle field was taken as a sample,and the bubble particle measurement theory was analyzed at the scattering angle of 45° ~120°.The experiments were carried out at the scattering angle of 90°and 45° to obtain the particle size distribution of the bubble field.4.An instrument for measuring cloud particle size was set up,and standard particles of 5?m,21.3?m and 45?m were measured in the laboratory to verify the accuracy of the instrument.The instrument was used to carry out experiments in the cloud chamber to measure cloud particle size distribution at 1,2,3,4 and 5 atmospheric pressures respectively.