Simplified time-averaged digital interferometry for vibration studies of microelements

摘要

Among interferometric techniques for analyzing mechanical properties and behaviors of microelements and microsystems time-averaged interferometry deserves particular attention because of its relative simplicity and data video display for arbitrary vibration frequency. This communication presents an implementation of the approach of Petitgrand et al. to quantitative analysis of vibration mode shapes based on the calibration of the fringe contrast variation as a function of the vibration amplitude. Fringe contrast maps for static and resonant frequency states are determined using the four-frame method with the phase shift of π/2 between the frames. Then the dynamic map is divided by the static one to obtain the square of the modulus of the characteristic fringe function. For sinusoidal vibrations it is the zero-order Bessel function J_0 squared with the vibration amplitude encoded in its argument. The simplicity of our approach and speed of calculations are to be emphasized. The fringe processing method proposed is suitable for conventional two-beam and digital speckle interferometry. The results of experiments carried with silicone cantilever beams used in AFM resonant sensors are presented.