US Patent 7715076 Micromirror device with a hybrid actuator

A hybrid electro-static actuator for rotating a two-dimensional micro-electro-mechanical micro-mirror device about two perpendicular axes includes a vertical comb drive for rotating the micro-mirror about a tilt axis, and a parallel plate drive for rotating the micro-mirror about a roll axis. The rotor comb fingers of the comb drive extend from a sub-frame of the micro-mirror, which is only rotatable about the tilt axis, while one of the parallel plate electrodes is mounted on the underside of a main platform, which generally surrounds the sub-frame. The vertical comb drive rotates both the sub-frame and the main platform about the tilt axis, while the parallel plate drive only rotates the main platform about the roll axis.