A rib-reinforced micro torsional mirror driven by electrostatic torque generators

A novel micromachined torsional mirror for use as an optical scanner is reported in this study. The proposed micromachined torsional mirror exploits novel electrostatic actuators and a reinforced thin-film mirror plate to improve the performance of the device. The electrostatic actuator is actuated by near gap-closing electrodes so as to decrease the driving voltage. Moreover, the actuator employs a lever mechanism to magnify its output displacement. A torque generator is implemented by combining two electrostatic actuators, which prevents the mirror plate from wobbling. A reinforced rib is used to stiffen the thin-film mirror plate to improve the optical performance of the scanner. In order to demonstrate the proposed concept, micromachined torsional mirrors were fabricated through the integration of DRIE, surface, and bulk micromachining processes. Measurements revealed that the proposed torsional mirror could operate at a low driving voltage, the scanning frequency of the mirror can reach 17.7 kHz, and the optical scan angle is 5°.