Abstract: A Coriolis mass flow measuring device, comprising at least one measurement pipe, through which a medium flows and which is induced to vibrate by an exciter arrangement, wherein two optical vibration sensors, arranged before and after the exciter arrangement in the longitudinal direction of the at least one measurement pipe, provide vibration signals, based on which an activation and evaluation device determines the mass flow and/or the density of the medium. The optical vibration sensors each have a pair of superimposed grids having periodic structures to improve the resolution that can be achieved by the optical vibration sensors.