Research Of Three-dimensional Stress Measurement Based On Laser Holographic Technology

Usually, stress measurement is realized based on three dimensional deformation measurement. The measurement of three dimensional deformation is always a important issue in the field of structure engineering. A measure method of three dimensional stress has been put forward. The method, named laser holographic three dimensional stress measurements, is based on the holographic interferometry and digital holography.Digital holographic measure technology is an optical measure method, which can measure object change with non-intervention and visual. It has many advantages, such as full-field, real-time, non-contact, high-contrast, high-precision. Therefore, it has wide/broad application prospect in the research of irregular displacement and deformation. In this paper, holographic interference measure system has been design. And many issues on the system have been studied in detail, such as theoretical research, optical path design, optical assembling and adjusting, experiment demonstration and feasibility analysis. Some practical research results have been obtained.In order to make up for the disadvantages of high cost and complex operation of phase-shifting controller, a method of digital phase shifting has been put forward. Combining the method with holographic interferometry, the research of phase shifting holographic interferometry has been made. Based on MATLAB and image processing, the holographic interference fringes have been directional moved on the condition of precise control. Then, four step phase shifting method has been realized and four interferogram have been obtained. According to the principle of four step phase shifting method and phase unwrapping method, using digital phase shifting method for three times to obtain four interferogram, the three dimensional phase difference map of object deformation can be successfully obtained. The measurement of three dimensional deformation has been realized. The experiment results show that the method can not only simplify the optical setup of holographic interference test, but also avoid the disadvantages of phase shifting error caused by the low precision of phase-shifting controller. Moreover, the method is simple operation and has high precision. The precision has easily reached1/10wavelength. This shows that,Laser holographic method for measuring three dimensional stress is an effective method.