Design of hybrid actuation piezoelectric MEMS scanning mirror with reduced nonlinearity

MEMS scanning mirrors are compact, high-frequency devices widely used for precise light steering in applications such as image projection. However, conventional piezoelectric MEMS scanners often exhibit nonlinear behavior that distorts images and limits system performance. This study presents a novel hybrid-actuator design that integrates a normal force actuator and a transmission spring with a traditional clamped-clamped torsional actuator to reduce nonlinearity while enhancing the scanning angle. Finite element simulations were conducted to analyze the dynamic behavior and stress distribution of the design, followed by device fabrication on SOI wafers incorporating a KNN piezoelectric film. Experimental measurements demonstrate that the hybrid-actuator design effectively reduces nonlinearity, achieving a 44.6 % increase in scanning angle and producing significantly clearer projected images compared to conventional designs. Additionally, Fast Fourier Transform analysis of vibration signals revealed a substantial reduction in Total Harmonic Distortion (THD), decreasing from 43.8 % in the reference design to 14.8 % in the proposed design. This reduction in THD directly contributes to the mitigation of image blurriness, further highlighting the superior performance of the proposed scanner.