A novel electrostatically driven torsional actuator

A novel CMOS-compatible manufactured electrostatically driven torsional actuator for periodic deflection of light is presented. The mechanical elements consist of a single crystal silicon film. The realized scan frequency of the resonantly excited actuator devices ranges from 0.14 kHz up to 20 kHz while the mirror area ranges from 0.5 x 0.5 mm2 up to 3.0 x 3.0 mm2. Due to a special configuration of the driving electrodes small gaps of typically 5 mu m can be used resulting in large electrostatic moments for the actuation of the mirror plate. Scan angles up to 60 deg (+-15 deg mechanical) at a driving voltage of only 20 V are achieved. The starting of the oscillation is possible because of asymmetries induced during fabrication. This asymmetries are enhanced artificially by an additional starting electrode which significantly reduced the settling time. Two different excitation modes are discussed.