Research On Particle Field Measurement Technology Based On Digital Holography

In today's society,science and technology are developing with each passing day,ranging from aerospace and even macroscopic observation of stars to microscopic measurements such as cell particles.Particle field has important applications in medicine,biology,chemistry,smelting and combustion,fluid composition detection and many other aspects,so the study of particle field is of great significance in people's production and life.Holography as an important branch of optics,the development of digital holography is a fast,convenient,low-cost measurement technology,it by recording and reconstruction process of two stage light is scattered by the object to recover complete wavefront information,namely the amplitude and phase distribution,and the most used in measuring the amplitude of particle field information.Digital holography technology USES digital photoelectric imaging digital devices such as CCD to replace the dry plate recording of traditional holography.The recording process is essentially similar to that of traditional optical holography,and the reconstruction process and the measurement information extraction of particle field are completed in the computer.This project "Research on particle field measurement technology based on digital holography",the purpose of this research is to propose an algorithm that can measure the size and number of microparticles in a given area by using the single-wavelength coaxial digital holography.The specific research contents are as follows:Firstly,the recording and reproducing principles of digital holography are studied,and the in-line and off-axis digital holography structures are discussed.Then the light diffraction theory is introduced,based on which the three reconstruction algorithms commonly used in digital holography,Fresnel diffraction method,convolution method and Angle spectrum method are studied in detail,and their respective characteristics and the advantages of the Angle spectrum method adopted in this subject are analyzed,which lays a basic theoretical foundation for the follow-up research.Then,the common digital holographic image processing techniques used in two-dimensional particle field measurement are introduced in detail,including image filtering,binarization,edge detection and hough transform.Then,the simulation,experimentand result analysis of simulated and actual two-dimensional particle field are carried out.The simulated two-dimensional particle field can be divided into two cases: sparse particles and dense particles.The feasibility of the process is proved by the simulation results and experimental results.Finally,on the basis of the two-dimensional particle field,the theory and technique applied to the measurement of the three-dimensional particle field are analyzed and discussed,including the focusing criterion of the pure phase object and the pure amplitude object,and the acquisition of the minimum intensity diagram and the maximum sharpness diagram.Then the experiment is carried out on the actual 3d particle field,the experimental sample is polystyrene spherical particles of 50?m.Finally,the experimental results are analyzed and compared to prove the feasibility of the theory proposed in this paper and the practical operation process.Finally,the measurement of particle size and position extracted from 3d reconstructed optical field is realized.