A micro opto-mechanical displacement sensor based on micro-diffraction gratings: Design and characterization

Abstract

A micro opto-mechanical displacement sensor is here presented. It is constituted by a sensing element based on two overlapped micro-diffraction gratings (MDGs). They present a platinum layer (45 nm of thick) on a glass substrate, a period of 525 µm constituted by a width of 150 µm of platinum separated (71.4% duty cycle). The working principle is based on the modulation of light intensity induced by the relative displacement between the MDGs: when a laser light perpendicularly hits the MDGs, the intensity of the transmitted light is a periodic function of the relative displacement between the two MDGs. A fiber optic is used to transport the transmitted light to a photodetector in order to avoid concerns related to the alignment between the optical components. The sensor's output is the ratio between the light intensity measured by the photodetector during the displacement of the MDGs and largest light intensity values measured in the whole range of measurement, therefore, it is lower than 1. The proposed sensor allows to discriminate displacement lower than 10 µm, using a cost effective micro-fabrication process implemented by the technique of Lift-Off. It shows a good linear behaviour in two ranges covering about one half of the MDGs period. Within the linear ranges it shows high sensitivity (about 0.5%/µm) and good accuracy (lower than 4% in the whole range of calibration); furthermore, the results show that a design with a duty cycle of 50% overcomes the marked decrease of sensitivity in a range of measurement corresponding to a grating period.

DOI: 10.1109/EMBC.2013.6610600

Cite this paper

@article{Accoto2013AMO, title={A micro opto-mechanical displacement sensor based on micro-diffraction gratings: Design and characterization}, author={Dino Accoto and Emiliano Schena and M. Cidda and Maria Teresa Francomano and Paola Saccomandi and S. Silvestri}, journal={Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference}, year={2013}, volume={2013}, pages={4714-7} }