Research And Implementation Of Fast Iterative Control Algorithm In Adaptive Optics System

The adaptive optics system can effectively correct the optical aberration caused by atmospheric turbulence in real time to improve the optical quality of the system.However,if you want to improve the precision,you must increase the size of the adaptive optics system.Correspondingly,the number of sub-apertures of wavefront sensor and the channels of deformable mirror are also increased.This will directly increase the amount of the computation and the time delay,thereby reducing the control bandwidth so that it cannot ensure the instantaneity.Therefore,it is an important research direction to decrease the time delay to increase the control bandwidth.Firstly,this paper analyzes the wavefront control algorithm theoretically based on large-scale adaptive optics system,aiming at decrease the time delay to increase the control bandwidth.Because of the sparsity of the slope response matrix,we choose the iterative control algorithm to calculate the control voltage.The conjugate gradient algorithm is appropriate compared with other iterative algorithms from convergence and computational complexity.In addition,we simulate conjugate gradient algorithm to calculate control voltage.Moreover,we compared the advantages and disadvantages of direct gradient control algorithm and conjugate gradient from two aspects: the amount of calculation and the storage space.Secondly,this paper verify the control algorithm based on an adaptive optics experiment device with a 37-element deformable mirror.We design the wavefront controller based on FPGA chip architecture modularly,which is conducive to system maintenance and upgrade.Wavefront computation refers to a class of processing consisting of wavefront slope computation,wavefront iterative control algorithm.The computation Structure of the wavefront controller are dual pipelines and parallel processing.In the process of design,we use RTL design diagram and timing simulation judge whether modules meet the requirements.Finally,we verify the technical feasibility of the iterative control algorithm by experiments.Results show that the design of iterative control algorithm in 37-element adaptive optics meets the system requirements and ensure the instantaneity.