Self-Balancing, Optical-Center-Pivot, Fast-Steering Mirror

A complete, self-contained fast-steering-mirror (FSM) mechanism is reported consisting of a housing, a mirror and mirror-mounting cell, three PZT (piezoelectric) actuators, and a counterbalance mass. Basically, it is a comparatively stiff, two-axis (tip-tilt), self-balanced FSM. Prior technology required two systems back-to-back on a center bulkhead, employing six opposing actuators, which must then be electronically balanced and recalibrated from time to time. The present invention requires only three (or three pairs for flight redundancy) actuators. If a PZT actuator degrades, the inherent balance remains, and compensation for degraded stroke is made by simply increasing the voltage to the PZT. Prior designs typically do not pivot at the mirror optical center, creating unacceptable beam shear.