Piezoresistive displacement sensor integrated in resonant varifocal mirror

Abstract

An electrostatically actuated resonant varifocal mirror with a piezoresistive displacement sensor is reported. The focal length of the varifocal mirror is monitored by the sensor. The device is fabricated from a silicon-on-insulator wafer and a glass wafer. The p-type silicon region which is formed in n-type top silicon layer by boron ion implantation is used as the piezoresistive displacement sensor. The mirror surface profile and sensor signal are measured.