Performance of an electrostatic actuated micromirror in a vacuum and non-vacuum packaging

Experimental results of micromirrors sealed in vacuum and non-vacuum environments are presented. The micromirror is 1.0 mm in diameter and is supported by four electrostatic repulsive actuators. The micromirror exhibits linear out-of-plane motion and rotational motion in two axes. The measured data shows that translational motion is 71 μm and 76 μm at 200 V for vacuumed and non-vacuumed micromirrors, respectively. The maximum optical rotational displacements for the vacuum and non-vacuum packaged micromirrors are 1.0° and 1.1°, respectively at 160 V. Packaging the micromirror in a vacuum decreases the squeeze film damping in the system. The settling time for the vacuum packaged micromirrors is 75 ms with an average overshoot of 116%. The settling times for the non-vacuumed micromirror are 2.75 ms with 5% overshoot for downward motion and 3.32 ms with 48% overshoot for upward motion. The estimated resonant frequency of the vacuum packaged micromirror is 2900 Hz, whereas the resonant frequency for the non-vacuumed micromirror is 1400 Hz. The static and dynamic results for the micromirror in reduced pressures determined that effects approaching the breakdown voltage become evident, resulting in lower displacements, and squeeze film damping effects are mitigated, leading to more consistent performance characteristics such as settling time and percent overshoot.