Study On In-plane Motion In MEMS Using Digital Speckle Correlation Method

Micro-Electro Mechanical System (MEMS) develops rapidly and steps into industry in recent years. In MEMS industrialization course, many research departments attach much more importance to MEMS testing technique. MEMS dynamic testing technique has obviously significant place in MEMS R&D and industrialization.Aiming at solving the rigid-displacement restriction in the present micro-structure in-plane motion measurement method, a combination of the stroboscopic imaging technique and the digital speckle correlation method is put forward for the extraction of the information of global rigid displacement and local deformation. For the measurement of MEMS in-plane motion, the gradient method and the Newton-Raphson iterative method work together well. Key points are classified as following:1. Study on digital speckle correlation method. Digital speckle correlation method has the advantages of non-contact, full-field measurement, simple optical path, having the ability to obtain the displacement field and the strain field simultaneously. It will be applied in micro-device in-plane motion measurement.2. An improved digital speckle correlation method based on the combination of gradient method and the traditional Newton-Raphson iterative method is put forward for better calculation precision. The correlative formulas are deduced, and the phase correlation method, the binary-cubic spline interpolation method, gradient method and the traditional Newton-Raphson iterative method is programmed with MATLAB.3. Take deep research on the initial-value problem in correlation calculation. The displacement calculated from gradient method, its derivative item and its digital differential coefficient are combined as the initial value of Newton-Raphson iterative method. Thus the poor convergence property in the correlation calculation induced by large deviation of the initial value with the true value is avoided, and the convergence speed and the precision are improved greatly.4. Combine with the stroboscopic imaging technique and the digital speckle correlation method. In-plane motion measurement is directed using the micro-resonator periodic-motion image serials from image-forming system. The periodic-motion trace of the image serials is reconditioned through gradient method. The extracting of the information of area deformation is realized based on Newton-Raphson iterative method.5. The theory analysis and experimental research are conducted for the measurement errors in digital speckle correlation method. The eliminating and restraining measures are given for better measurement precision.