Precision Stabilization of a Ball Joint Gimbaled (BJG) Mirror

A novel non-contact approach is proposed for the direct measurement of mirror or antenna angular displacement in azimuth and elevation. This approach is uniquely suited for implementation in systems where the angular displacement is estimated or implied by an indirect method that has inherent error sources limiting the ultimate achievable accuracy. The error for the proposed measurement system has its' lower bound defined by the capability to process the output of a detector to the equivalent of a subpixel level. The direct angular measurement provides an accurate feedback signal to the overall control loop(s) turning the system into a position feedback configuration. Since the measurement is non-mechanical, and the processing can be relatively simple, the feedback component can be high bandwidth introducing very little if any additional phase shift into the control loops, thus keeping the original system's rapid response intact.