Micrograting Displacement Sensor with Integrated Electrostatic Actuation

A high-resolution micro-grating displacement sensor with diffraction-based and integrated electrostatic actuation is proposed and experimentally demonstrated. The Al reflecting membrane is fabricated at the bottom of a silicon moving part and the Au micro-gratings are patterned on a transparent substrate. This structure forms a phase sensitive diffraction grating, providing the displacement sensitivity of the micro-grating interferometer. It shows sensitivity adjustment and self-calibration capabilities with electrostatic actuation. Additional system components include a coherent light source, photodiodes, and required electronics. Experimental results show that the displacement sensor has a sensitivity of about 1.8 mV/nm and a resolution of less than 1 nm in the linear region. This displacement sensor is very promising in the fields requiring high sensitivity, broad dynamic range, and immunity to electromagnetic interference.