Measurement of longitudinal vibrations in a slender rod by optical heterodyne interferometry

摘要

The vibration of a slender rod subject to a longitudinal harmonic perturbation without physical contact and near the first resonance frequency is experimentally analyzed. The rod is exited by a magnetic field which produces an harmonic force acting on a small ferromagnetic disc glued at the end of the rod. The detection technique applied is based on the optical heterodyne speckle interferometry, which permits both the normal-to- surface displacement and the tangential displacement to be detected sequentially.