Bandwidth estimation for adaptive optical systems based on stochastic parallel gradient descent optimization

Adaptive system bandwidth estimation techniques that can be applied to the adaptive optical systems based on stochastic parallel gradient descent (SPGD) optimizations are described. A useful parameter characterizing temporal dynamics of phase fluctuations resulting from the pupil-plane phase distorting layer moving at a certain velocity (wind velocity) is the Greenwood frequency. The knowledge of the Greenwood frequency and clock frequency of the adaptive control system (first order controller) allows simple estimation of the performance metric Strehl ratio. The numerical analyses indicate that the system performance can be characterized through the ratio of the Greenwood frequency and the system iterative process clock-frequency. A formula that estimates how the degradation of the adaptation performance in SPGD based compensators are derived and analyzed numerically. The bandwidth estimation for SPGD control systems with different resolution and decoupled SPGD (D-SPGD) control system is detailed.