Requirements for the dynamic characteristics of adaptive optics systems
V.P. Lukin
V.E. Zuev Institute of Atmospheric Optics of Siberian Branch of the Russian Academy of Science, Tomsk, Russia
Keywords: atmosphere, adaptive optics, turbulence, Fried parameter, open and closed tracking loops, wind, forecast
Abstract
The dynamic (temporal) characteristics of adaptive optics systems operating through a turbulent atmosphere are analyzed. An analytical calculation of the Strehl parameter is used based on the results of the theory of optical wave propagation in randomly inhomogeneous media. The analysis uses a model of the active correcting mirror. A traditional adaptive optics system with a finite response time is described as a dynamic constant lag system. In such a system, the admissible time delay turns out to be comparable with the time of transport of turbulent inhomogeneities through the radius of coherence by the average wind speed. An expression is derived which connects all the most important parameters of the system: the accuracy and frequency of the wavefront sensor, the size of the aperture of the optical system, the parameters of the atmosphere: the Fried parameter and the wind speed with an achievable level by the Strehl parameter. Differences between open and closed loops in AO systems are analyzed. The possibilities of the "predictive" algorithm for adaptive correction are shown.
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