Research On In-plane Displacement Measurement Technology Based On Electronic Speckle Pattern Interferometry

Measuring deformation within the material surface is a common problem in testing the mechanical properties, as opposed to the popular contact measurement methods, the use of non-contact optical measurement method has many advantages. Accurately measuring the in-plane displacement of the material is important for subsequent measurement of the elastic modulus and Poisson’s ratio.This paper focus on the application of the digital speckle pattern interferometry (ESPI) in the material in-plane deformation, as well as some related technologies.This paper first discusses the popular in-plane displacement measurements methods and speckle interferometry measurement principle.Current traditional measurement techniques are described,such as common mechanical method,and measuring method based on CCD, etc, and then the basic principles of speckle interferometry and several in-plane displacement sensitive measurements optical design are introduced.This paper then discusses the key technologies in ESPI. In order to obtain accurate phase, several different phase extraction techniques are discussed, including time and space phase shift phase shift technique. In order to be able to better access to speckle image feature, the different filtering algorithms are discussed, including a strong tradition of several adaptive speckle filtering algorithm and image filtering algorithms. Then, a detailed analysis of the basic principle of phase unwrapping and computer simulations is introduced, focusing on two types of phase unwrapping algorithms, which are based on the path selection and based on global statistics.Finally, in order to cope with the practical needs of the laboratory, a set of speckle pattern interferometry measurement software is designed,basically achieve the functions of ESPI.The design of in-plane displacement specimen is introduced,and set up a measurement light path to measure that specimen.Besides,the Dantec Q-300 speckle interferometer is used as a reference.Then utilize the finite element analysis to verify the consistency of theory and practice. Through the above experiments and analysis, the measurement results and theory of in-plane deformation confirm each other,prove the feasibility of speckle interferometry method for measuring the in-plane displacement of material.