Interferometric System Images Small Vibrating Structures

A commercial scanning imaging white-light interferometer designed for measuring surface profiles of stationary objects has been modified into an interferometric instrument for imaging vibrating microelectromechanical structures. The modified instrument operates in a stroboscopic mode, generating a set of interferograms at a selected instant in the vibrational cycle. A number of sets of interferograms can be acquired at different instants of time corresponding to small increments of phase through the vibrational cycle so that the resulting collection of interferograms shows how the shape of the vibrating surface changes during the cycle; thus, the interferograms yield information on the shape and amplitude of the vibrational mode or modes.