Motion nonlinearity of gimbaled MEMS micromirror in omnidirectional scanning

The motion nonlinearity of gimbaled micromirror is studied using the motion equations for the application to omnidirectional scanning of light detection and ranging. The numerical calculations show that the nonlinearity by the motion interaction between mirror and gimbals is dependent intricately on the moments of inertia along respective axes as well as angular velocities and damping factors. The nonlinear terms of the equations increase with the increase of the difference of the moments of inertia along the two orthogonal axes of mirror. The motion nonlinearity relatively decreases with the increase of the dumping coefficient. A gimbaled micromirror with the electrostatic comb actuators was fabricated from a silicon-on-insulator wafer and the motion was observed around the resonant frequency of 5.3 kHz. The expected circular trajectory was deformed to be elliptical. The trajectory was stable but occasionally became uncontrollable by the voltage and the frequency of the actuators. The minimization of the motion nonlinearity is discussed from the viewpoints of inertia and damping.