The multidither principle in adaptive optics

Coherent optical adaptive techniques (COAT) offer promise for overcoming the deleterious effects of phase distortions experienced by optical beams propagating through distorting optics or via a turbulent and absorbing atmosphere. The theory of four classes of such systems, which employ similar multidither principles, is explored. Many modes of operating these systems are briefly reviewed and a detailed analysis of the most widely employed - a glint referencing system with sinusoidal dithers - is developed. A servo signal-to-noise analysis indicates how the optimum choice of dither magnitude depends on the system noise.