Predictability of fractional-Brownian-motion wavefront distortions and some implications for closed-loop adaptive optics control

摘要

Abstract: Kolmogorov turbulence has a temporal behavior best described by fractional Brownian motion (FBM) with a self-similarity parameter of H $EQ 5/6. Non-Kolmogorov behavior, which has also been observed and reported, is characterized by H other than 5/6. Although FBM has strong inter-sample correlations, the signals arising in an adaptive optics control loop are not FBM, have weaker inter-sample correlation,and exhibit quite different characteristics with regard to predictability. One conclusion is that for greatest advantage, prediction within the loop should be introduced at the point where signals represent the reconstructed wavefront, i.e. mirror drive signals, and not at the level of the wavefront sensor output or wavefront error signals. !16