Abstract: A system for scanning vibrations of a mass and for converting the mechanical vibrations into corresponding electrical signals is disclosed. The system includes a source of a scanning radiation beam, preferably of a light beam, which has a larger transverse cross section than the vibrating mass. The umbra behind the mass and the surrounding illuminated area are collected by a focussing lens and projected onto an optoelectric converter. The collecting surface and/or the active light receiving surface of the converter have an outline which is variable in the direction of displacement of the vibrating mass so that the illuminated area varies in size during the vibration of the mass.