Design and simulation of modified 1-D electrostatic torsional micromirrors with z-axis displacement

Micromirrors based on Micromechanical. systems (MEMS) have been essential components in many applications, such as micro confocal microscopy, optical data storage and biomedical imaging [1-3]. A variety of microfabrication and actuation technologies have been used to realize micromirrors, including electrothermal [3], electrostatic [1], etc., of which electrostatic torsional drive ha s been thought to be the most popular driving mechanism. K. E. Peterson [4] has developed the world first 1-D electrostatic driven torsional micromirror. The Lucent [5] Lambdroutor is one of famous and successful examples of 2-D electrostatic torsional micromirrors. For design improvement of this type of 2-D micromirror, Toshiyoshi et al. [6] have proposed a linearization method based on applying a small control voltage over a large bias voltage. Chiou et al. [7] have presented improved design to demonstrate linear stepping angles of 1-D micromirrors based on multiple electrodes. These developments are focus on realizing linear steps in angle. As mentioned by above articles, there are also displacements in z-axis as the micromirror is actuated, which have been ignored. The z-axis displacements have become a significant problem when the micromirrors are used on high resolution spatial scanning. Krishnamoorthy et al. [8] presents a dual-mode 1-D micromirror utilizing stacked multilayer vertical comb drive actuators, which can provide both piston and tilt motion. We have developed a z-axis displacement compensation concept for 2-D electrostatic torsional micromirrors previously [9].