Transient 3D Deformation Measurement Based On ESPI

Transient three dimensional electronic speckle pattern interferometry(3D-ESPI) is the simultaneous acquisition of the three components of the electronic speckle interference pattern,and through data processing and data synthesis dimensional object deformation inforination.It is mainly applied in measuring the parameters,such as deformation,stress,strain,vibration and so on,owing to speckle images carrying the phase information of object surface.Because of the three-dimensional nature,transient characteristics and high sensitivity,this technology has potentially important application value.In this dissertation,a transient method of three-dimensional deformation measurement by color splitting based electronic speckle pattern interferometry(ESPI)is presented and applied in the measurement of transient three dimensional object surface deformation.The method takes red,green and blue wavelength lasers as the light sources,uses a color CCD to capture the speckle interference images from three paths.The color light is used to achieve the separation of the speckle interference image information from the in-plane vertical direction,in-plane horizontal direction and out-of-plane direction of the object.The Windowed Fourier transform,the Wavelet transform or phase-shifting algorithm is applied to process the speckle interference fringe pattern to demodulate the deformation phase field in all directions separately and to obtain three-dimensional deformation field.The method can achieve the deformation measurements of an object's vertical,horizontal and out-of-plane directions simultaneously,so that it is applied to measure transient three-dimensional deformation of the object's surface and to realize independent measurements of the in-plane and out-of-plane two-dimensional deformations.The paper briefly presents the development and principle of ESPI.Then the geometric theories of in-plane deformation,out-plane deformation and three-dimensional deformations of measured object are analysed in details.At last,several types of con ventional 1 D-ESPI?static 3D-ESPI and transient 3D-ESPI system are introduced.A new Windowed Fourier transform phase algorithm based on continuous Wavelet transform and Hilbert is proposed in order to overcome the shortcomings of old Windowed Fourier transform phase algorithm.A Wavelet transform method based on Fourier transform is proposed to improve the speed of processing interferogram owing to the disadvantage of time-consuming for the existing continuous Wavelet transform algorithm.A transient three-dimensional deformation and shape measurement system based on Wavelet transform is proposed according to shortcoming existing transient three-dimensional deformation detection system.A kind of transient 3D-ESPI system and an image acquisition mode for phase-shifting algorithms are designed according to the advantages of phase-shifting algorithms.A Gauss-Seidel iterative algorithm is provided to improve the accuracy of the phase-shifting algorithm.We totally analyze the main errors of transient 3D-ESPI detection system.Then an algorithm of solving the deformation based on Gauss-Seidel iterative is designed to improve the accuracy of the system.The experiment which measures the stainless steel board's 3D deformation in transient state has been done,and gives the display images of the 3D deformation.We achieve the experimental verification of transient three-dimensional deformation detection systems and algorithms.