Modeling of grating/moiré based micro motion sensor

Abstract The design of a micro optical motion sensor is proposed. Fourier series analysis is used to determine the optical transmission function (OTF) of gratings. The optical flux generated by a grating (pair) and received by photodetector is then calculated through an integration of the OTF over the receiving window. A general relationship between photo-detector output current and grating translation displacement is finally established. The analysis is carried out for linear binary grating sensors, with single and double grating sensors. The influence of grating (pair) structure and receiving window on sensor sensitivity and linearity of output response is investigated. A numerical work is completed to simulate the various cases of optical structure design. Several types of photoresist gratings are fabricated and are used to experimentally characterize the grating sensor. The tested result is found to be in general agreement with the analysis result.