Dynamic ESPI (DESPI) and Hilbert transform method for deformation analysis of MEMS and very small object

In this study a Dynamic Electronic Speckle Pattern Intereferometry (ESPI) method was applied to investigate deformation field of small industrial elements. In the proposed phase analysis method, the interference signal is considered in time domain and the phase was analyzed by Hilbert transform method. Two experiments were performed, with in-plane and out-of-plane sensitive systems in order to make a complete characterization of the deformation field in three dimension. First, experiments were carried out for the measurements of thermal expansion of a joint material (ceramic-copper-stainless steel). The deformation field showed clearly the difference between the thermal expansions of the stainless steel and ceramic. The thin copper layer can also be clearly distinguished in the deformation distribution. Next, experiments were performed for a scratch-drive device of MEMS. Movement of the element of the device was accurately measured while the device is operating.