Practical adaptive filter controls for precision beam pointing and tracking with jitter attenuation

The imaging, pointing, and tracking performance of precision optical systems are degraded by various disturbances which induce optical beam jitter. The present research proposes adaptive filter control methods for actively attenuating beam jitter using a fast steering mirror. Control loops with various structures of adaptive transversal filters are developed to suppress time-varying or uncertain jitter, and their characteristics and performances are compared. In particular, for situations when obtaining reference signals which are fully coherent with the disturbance is not possible, methods for incorporating multiple semi-coherent reference signals into the control law are developed. An index variable is defined to measure quality of various references signals, and a few signals are selected based on this index. The developed controllers are verified on a jitter control testbed, and experimental results show that the adaptive methods show superior performance in jitter attenuation over the conventional non-adaptive method.