Research On Object Dynamic Deformation Measurement Based On Image-plane Digital Holography

Compared with other digital holographic measurement technologies,image-plane digital holography has the advantages of simple recording equipment,high resolution,low noise and small amount of calculation.Therefore,it is widely used in Micro-nano measurement,biological cell analysis,particle imaging and tracking.The effective measurement range of image-plane digital holography is proportional to the wavelength,when the corresponding optical path difference exceeds 2? in the measurement range,phase wrapping will occur.The unwrapping algorithm will bring uncertain errors to the reconstructed phase,therefore,the single exposure of digital holographic interference method can be used to divide the movement process of the measurement target into multiple sub-processes,and each sub-process is separately reconstructed to achieve rapid measurement of objects with large dynamic deformation.This article aims at shape measurement of dynamic object.At first,the image-plane digital holography measurement method is studied.The difference of two filtering methods including image plane filtering and frequency spectrum filtering in holographic reconstruction are analyzed,and the image-plane digital holographic fast measurement algorithm for macroscopic objects is proposed.Secondly,in order to achieve a faster computing speed,combined with the GPU,the GP-GPU image-plane digital holography fast processing static library CLibrary is established.Thirdly,the vibration characteristics of the MEMS microphone and the deformation movement of the silicone film are studied.Finally,a digital holographic high-speed measurement system is established.The main research contents of this article are as follows:1.The basic principles of wavefront recording and wavefront reconstruction in digital holography are introduced,and the microscopic measurement theory of digital microscopic image-plane holography is analyzed.The problem of compensation for quadratic phase distortion in the pre-amplified Fresnel off-axis diffraction optical path is studied.The single-exposure method is proposed to solve the problem of phase wrapping during the reconstruction of the hologram.The theories of image plane filtering and frequency spectrum filtering are studied.Aiming at the shortcomings of the small range of the micro-vibration rapid measurement algorithm proposed by Li Jianyi et al.,a image-plane digital holographic fast measurement algorithm is proposed,which increases the measurement range of the algorithm and makes it not limited to microscopic measurement.2.The image processing algorithm based on CUDA is studied.The basic principle of parallel computing is expounded,and the CUDA and Visual Studio 2013 based GP-GPU image-plane digital holography fast processing static library CLibrary is built,which includes: digital microscopic image-plane holographic algorithm,image-plane digital holographic fast measurement algorithm and two filtering methods of frequency spectrum filtering and image-plane filtering.3.The CUDA-based image-plane digital holographic dynamic measurement is researched.The mechanical model of the MEMS microphone is analyzed and the motioncharacteristics of the MEMS microphone is studied using the image-plane digital holographic algorithm based on CLibrary.The measurement accuracy of the algorithm is analyzed,and the difference of the two filtering methods of frequency spectral filtering and image filtering are compared.The image-plane digital holographic fast measurement algorithm is used to analyze the deformation of the silicone film,and the measurement error of the algorithm is calculated.The performance advantages of the GPU-based reconstruction algorithm compared with the traditional CPU reconstruction algorithm is demonstrated.Among them,the maximum processing speed of the frequency spectral filtering reconstruction algorithm reaches 43 fps,and the maximum acceleration ratio of the image-plane digital holographic fast measurement algorithm reaches 306.5.4.A digital holographic dynamic deformation measurement system is established.The hardware part are composed of a pre-amplified Fresnel off-axis diffraction optical path,a high-speed camera,and the workstation with tesla K80.The software part is the GP-GPU image-plane digital holography fast processing static library CLibrary based on CUDA and Visual Studio 2013 and the digital holographic interactive interface established by MATLAB.