| Adaptive optics systems have been playing an important role in improving imagequality obtained by large telescopes. Image quality can be reduced by the influence ofatmospheric turbulence and thermal blooming. Wavefront sensor-less adaptive optics isone of the most important research focuses in adaptive optics technology. Wavefrontsensor-less adaptive optics systems based on the optimization algorithm can avoid aseries of problems caused by conventional wavefront measurement. The structure issimple and compact. The efficiency of an optimization algorithm has influenced theperformance of wavefront sensor-less adaptive optics systems. In order to improve thecorrection capability of the system, the suitable optimization algorithm of wavefrontreconstruction is studied. In the paper, based on analysis and research on the adaptiveoptics technology, adaptive optics system models are established. Modal wavefrontreconstruction algorithms are discussed for improving the correction capability of theadaptive optics system.The main contents can be summarized as follows:1. This paper studies the principle of wavefront aberration and the propagation oflight beam. The system control structure is described. Further, the working process ofthe system is introduced in details such as wavefront detection, wavefrontreconstruction and wavefront aberration correction. The research on numericalsimulation of light propagation in the atmosphere is carried out. Light beam qualityevaluating methods are discussed.2. A wavefront sensor-less adaptive optics system is set up, and a modal wavefrontreconstruction algorithm based on particle swarm optimization (PSO) algorithm whichis applied to controlling a deformable mirror (DM) is proposed. It is initialized with apopulation of random solutions. The system takes the laser power through the pinhole asthe system performance metric. According to evolution rules of PSO algorithm, thesolution space is searched for the global optimization. The simulation results show thatthis algorithm can find the optimum DM shape which is applied to correcting phaseaberration. 3. To improve the convergence performance of the adaptive optics systemcontrolled by the optimization algorithm, an improved particle swarm optimization(IPSO) algorithm using mutation strategies is proposed. In this proposed algorithm,mutation strategies are used to keep the diversity of the particle swarm and makeparticles explore the space more efficiently. The experimental results show that thealgorithm can improve the precision of wavefront reconstruction.4. A modal wavefront reconstruction algorithm based on the parallel mutationparticle swarm optimization (PMPSO) is proposed by combining the inherentparallelism of PSO algorithm with parallel models. The PMPSO is designed based onmaster-slave model. The results show that the PMPSO has good convergenceperformance when the communication time step is appropriate. The experimental resultsshow that the optimization scheme can provide better efficiency for finding the optimalcombination of actuator voltages.5. A fast modal wavefront reconstruction approach based on mutual information isproposed. An adaptive optics system based the fast modal wavefront reconstructionalgorithm is established. By studying the capability of wavefront reconstruction of themodal basis and reducing the basis dimension of wavefront reconstruction, thereconstruction speed can be improved. The simulation results show that the proposedalgorithm can achieve good correction result.6. An object-oriented simulation platform of a61-element adaptive optics system isestablished. This paper solves the layout of actuators and subapertures on the adaptiveoptics simulation platform. The reconstruction matrix is calculated. The Gauss randomnumber is used to simulate influence of atmosphere turbulence on transmission of lightbeam. Finally, the performance of the adaptive optics system is analyzed and theexperimental results are presented. |
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