Electronic Speckle Pattern Interferometry And Digital Image Processing

Speckle metrology is a kind of new NDT technique which develops in recent years. Speckle metrology is to record speckles formed in front of an object surface because of interference of light waves. When the object moves or deforms due to the action of loads, these random distributed speckles also move in space according to certain laws. Therefore, the recorded speckle pattern can be used to analyze the motions or deformations of objects. Compared to the traditional measuring method, speckle metrology has lots of advantages, such as real-time, non-contact and whole-field, thus has been used widely measurement of vibrations, displacements, strains and medical diagnoses.Electronic speckle pattern interfometry and digital image processing techniques are studied in this thesis. Based on properties of MATLAB and LabVIEW, LabVIEW and MATLAB are combined to design the electronic speckle image processing system. The speckle patterns can be captured based on the LabVIEW platform. The filtering processing and phase calculation of the captured speckle patterns can be obtained by calling MATLAB Script. Finally, the processed results can be displayed by using LabVIEW.The main research work in the thesis involves: (1) The syetem which can be used to collect and process electronic speckle patterns is established by LabVIEW and MATLAB; (2) The filtering techniques of spatial and frequency domains are investigated and the electronic speckle patterns are processed by the median flitering and cosine filtering methods; (3) The phase measuring technique is studied in this thesis, and the continuous displacement distribution of objects can be evaluated by using the phase-shifting technique.