A study of integrated position sensors for PZT resonant micromirrors

Abstract

PZT driven resonant micromirrors offer advantages of large scan angles and decreasing power consumption due to the benefits of resonant driving and high torque delivered by PZT actuators. Therefore they are entering into different application fields recently, for example as laser projection or head-up displays. For many uses position sensing of the micromirrors is necessary to set up closed loop controls. Thus, the development of integrated position sensors is aimed in this work. Investigation and evaluation of different position sensing principles have been performed. In previous works 1D and 2D PZT driven resonant micromirrors have been presented, which feature various spring suspensions and thinfilm PZT actuators as drivers. Due to the considerably different motion modes and resonant frequencies, which vary from 100 Hz up to 64 kHz, various position detection methods have been investigated. This work presents primarily fabrication and characterization results of the position sensors based on the direct piezoelectric effect, which will be compared to the position sensors using metallic strain gauge realized by the same fabrication technology. Analyses of the sensitivity, linearity and dynamic behavior of the sensors have been performed, by means of comparing the sensor signals and the micromirror position signals measured by a Position-Sensitive-Device. Advantages and drawbacks of the sensors are discussed and methods for eliminating the drawbacks are proposed.