High-performance adaptive control of optical jitter in laser beam systems

The research reported by this thesis explores the line-of-sight control problem in laser beam steering applications. Both experimental and theoretical results are presented. A typical fast steering mirror was used for part of the experimental research. Another part of the research demonstrates the capabilities of a novel liquid crystal device, uniquely designed for line-of-sight control. The optical jitter is suppressed with an adaptive controller, which is based on a recursive least-squares finite-impulse-response (FIR) lattice filter. The steady-state performance of the high-order adaptive controller approximates closely the theoretically achievable minimum-variance steady-state performance, which is derived from the identified plant and jitter dynamics.; Also included are theoretical results on minimum-variance steady-state performance of adaptive and optimal linear-time-invariant controllers. It is shown that the problem of finding the optimal FIR filter is equivalent to a linear-quadratic regulator problem on a finite interval of length equal to the order of the filter. The analysis permits evaluation of the experimental results.