3D measurement of micromechanical devices vibration mode shapes by stroboscopic microscopic interferometry

Microscopic interferometry is a powerful technique for the static and dynamic characterization of micromechanical devices. In this paper we emphasize its capabilities for 3D vibration mode shapes profiling of Al cantilever microbeams and Cr micromachined membranes. It is demonstrated that time-resolved measurements up to 800 kHz can be performed with a lateral resolution in the micrometer range and a detection limit of 3-5 nm. In addition, with reduced image sizes (256x256), quasi real time (150-500ms) visualisation of the vibration mode 3D profiles becomes possible. These performances were obtained by using stroboscopic illumination with an array of superluminescent LED and an optimised automatic Fast Fourier Transform phase demodulation of the interferograms. The results are compared with theoretical shapes of the vibration modes and with point measurements of the vibration spectra