Deflection properties of a MEMS optical scanner with four torsion beams and L-shaped arms

Abstract

A structural design of a micro-electromechanical-system (MEMS) optical scanner with four torsion beams and arms was investigated to improve the optical scanning properties. Scanners described in previous reports had two pairs of beams and straight arms. In this study, the arm structure was examined without increasing the chip size of the scanner, and the L-shaped arm design was investigated by running simulations and evaluating fabricated samples.The measured resonant frequencies decreased with decreasing connection arm width and agreed with those of the simulation results. The hysteresis of the frequency response at a large deflection was reduced by approximately one half in the L-shaped arm structure as compared to that within the straight arm structure when the connection arm width was designed so that the resonant frequencies of each arm were equal. The optical beam deflection of the L-shaped arm structure for an applied voltage of 2 Vp-p was 20% higher than that for the straight arm structure when the connection arm width was over 800μm. These results indicate that the L-shaped arm structure decreases the hysteresis range by one half and increases the driving efficiency by 20%, even though the device chip size and the other scanner characteristics remained unchanged from those of the straight arm structure.