Abstract
This contribution describes an opto-mechanical transducer with a non-linear transfer behaviour and its impact on the quantification of static and dynamic displacements in a vibrating measurement mode. The device's output signal is proportional to a lightflux that is modulated by two overlapping gratings. One of the gratings is deposited on a fixed glass cover while the other one is etched into a moveable seismic mass of a Si MEMS chip. The non-linear transfer characteristic is achieved by paring a triangular grating with a rectangular one. The mass is actuated by a mechanical shaker unit and the resulting 1st and 2nd harmonic of the output signal are recorded with Lock-In amplifiers. These harmonics contain information about the static displacement and the vibration amplitude of the mass. The presented method allows for a precise measerement of the static displacement with an error of ±0.017% compared to DC measurements exhibiting an error of ±0.066%.
Published Version
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