A biaxial fast steering mirror for precision optical pointing systems

To mitigate the base motion jitter, many optical systems use a Fast Steering Mirror (FSM) in order to enhance the pointing precision. The FSM is usually a nonredundant electromechanical device, having a flexurally suspended mirror, capable of biaxial steer-, ing ( f 1 degree) and high frequency (600-2000 Hz) responses. This paper describes the implementing hardware for two FSM articulators. The f i s t features flexural suspension, and the second is a fully redundant FSM. The latter has a magnetically suspended 0.7 inch diameter mirror and 2000 Hz closed loop bandwidth. The servo loop controls five degrees of freedom. The magnetic suspension elements, in addition to the levitation, are also utilized for the articulation functions. A novel five degrees of freedom, payload displacement sensing system provides the required feedback signals. The basic design algorithms for the suspension and articulation functions are also given. Their quality is indicated through comparisons with experimental data when such is available.