A micro-mechanical actuator includes a partially cylindrical rotatable rotor assembly, a stationary stator structure, rotatable connectors, connecting the rotor assembly and the stator structure, and a switch controller, controlling the actuator. The rotor assembly includes a rotor cylindrical surface, rotor-electrode strips on the rotor cylindrical surface, and a rigid platform. The stator structure includes stator-electrode strips on a stator cylindrical surface. The micro-mechanical actuator may be part of an optical system, which includes a light source and a light receiving element. The actuator in an active position reflects the emitted light towards the light receiving element and n a passive position leaves the emitted light unreflected. A method of operating the micro-mechanical actuator includes activating the stator-electrodes and the rotor-electrodes in a timing sequence and exerting a force on the activated rotor-electrodes by the activated stator-electrodes, thereby rotating the activated rotor-electrodes and the rotor in rotation-intervals corresponding to the timing sequence.