Interferometric optical profilometers are increasingly used for the characterization of the static deformation of micromechanical devices and Micro(Opto)Electromechanical Systems (M(O)EMS). Recent works have shown that they can also be used for full field dynamic measurements provided that a stroboscopic light source is added or that time averaging of the interferograms is performed. In this work we investigate two methods to make quantitative time-averaged microscopic interferometric measurements. Both methods are based on the calibration of the fringe contrast variation as function of the vibration amplitude. It is demonstrated from experiments on micromechanical devices that 3D vibration modes shapes can be measured at any frequency with a spatial resolution in the micrometer range and a detection limit around 5 nm.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.