Research And Design Of The Two-dimensional Digital Speckle Pattern Interferometry System Based On Spatial Carrier Phase-shifting

The deformation measurement methods can be classified into optical measurement methods and non-optical measurement methods.Digital speckle pattern interferometry is a branch of optical measurement methods.It is widely used in three-dimensional deformation measurement,non-destructive testing,medicine,aerospace and other fields due to its advantages of fast speed,high precision and non-contact measurement.Digital speckle pattern interferometry obtains the needed measurement information by phase information.At present,the commonly used phase measurement methods include time phase-shifting method and spatial carrier method.Although the accuracy of phase obtained by time phase-shifting method is high,it is not suitable for dynamic measurement.Spatial carrier method only needs to collect two speckle images before and after deformation to calculate the phase information.This method is simple and suitable for dynamic measurement.This thesis studies the spatial carrier method,aiming to improve the real-time measurement performance of digital speckle pattern interferometry.In this thesis,the measurement principles of one-dimensional and two-dimensional deformation are described in detail,and the deformation equations are deduced.Some optical configuration design and parameters are discussed.Based on Visual Studio 2013 platform with MFC and OpenCV,a DSPI software is designed and compiled in Windows using C++ language.This software realizes the functions of image acquisition,image filtering,phase unwrapping,and 3D image display.Since the directly calculated phase is wrapped into the range of [-?,?),phase unwrapping is necessary.However,the classical path-following algorithms can not effectively prevent error propagation and optimize the unwrapping path simultaneously,which limits the phase unwrapping accuracy.In order to improve the accuracy of phase unwrapping,a region-growing phase unwrapping algorithm based on branch-cut and reliability is proposed.The improved algorithm prevents error propagation through branch-cut,and guides the selection of unwrapping path by reliability,thus it is able to improve the phase unwrapping accuracy.In order to verify the effectiveness of the improved algorithm,global and local noise simulations are performed.The improved algorithm can obtain better unwrapping results and smaller unwrapping errors when the global and local noises are strong.The simulation results show that the improved algorithm is able to improve the phase unwrapping accuracy.In order to verify the feasibility of the designed setup and software system,one-dimensional and two-dimensional deformation experiments are carried out by using a thin aluminum board firstly.Then the dynamic deformation measurement of the cans is performed.Experimental results show the designed system is able to dynamically measure the deformation of objects.