Damping of Micro Electrostatic Torsion Mirror caused by Air-film Viscosity Norio UCHIDA, Kiyotaka UCHIMARU, Minoru YONEZAWA and Masayuki SEKIMURA An analysis method of the damping characteristics for electrostatically driven torsion micro actuators which have deep grooves on their electrodes is described. The damping force is caused by viscous friction (squeeze action) of the gas film between a moving mirror plate and the electrodes. The grooves decrease the damping force and enable the moving

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... late to be driven at high speed and low driving voltage. To calculate the damping force correctly, it is required to consider the viscous friction not only on the moving plate and electrodes, but also on the side walls of the grooves. For that purpose, the idea of hydraulic mean depth is introduced and is applied to Reynolds equation. The calculated damping force shows good agreement with the measured damping force of the developed torsion mirror actuator for optical heads.