Abstract
The correction capability and the convergence speed of the wavefront-sensorless adaptive optics (AO) system are compared based on two different system control algorithms, which both use the information of focal plane. The first algorithm is designed through the linear relationship between the second moment of the aberration gradients and the masked far-field intensity distribution and the second is stochastic parallel gradient descent (SPGD), which is the most commonly used algorithm in wavefront-sensorless AO systems. A wavefront-sensorless AO model is established with a 61-element deformable mirror (DM) and a CCD. Performance of the two control algorithms is investigated and compared through correcting different wavefront aberrations. Results show that the correction ability of AO system based on the proposed control algorithm is obviously better than that of AO system based on SPGD algorithm when the wavefront aberrations increase. The time needed by the proposed control algorithm is much less than that of SPGD when the AO system achieves similar correction results. Additionally, the convergence speed of the proposed control algorithm is independent of the turbulence strength while the number of intensity measurements needed by SPGD increases as the turbulence strength magnifies.
Highlights
Compared with the conventional adaptive optics (AO) system [1], the complexity of wavefront-sensorless AO system [2] is reduced greatly because of no wavefront sensor in system structure
To investigate the convergence speed and the correction capability of the wavefront-sensorless AO system with a 61element deformable mirror based on the proposed control algorithm, we perform the adaptation process over random
The AO system based on two kinds of algorithms has strong correction ability on wavefront aberrations under different turbulence from Figure 6(a), in which MR values are very close to ideal correction of deformable mirror offered by the minimum variance solution
Summary
Compared with the conventional adaptive optics (AO) system [1], the complexity of wavefront-sensorless AO system [2] is reduced greatly because of no wavefront sensor in system structure. We design a control algorithm for the wavefront-sensorless AO system through the linear relationship between the second moment of the aberration gradients and the masked far-field intensity distribution. In order to find out the control parameters of deformable mirror, N orthogonal modes are taken as predetermined bias functions and are added by the DM sequentially with coefficient α to the wavefront aberration to be corrected. Preprocessing Step (1) Calculate the second moment of the wavefront gradients S, the diagonal vector Sm, and its inverse matrix S−1 according to the predefined bias function Z(x, y) by (5). (2) Gather the corresponding far-field intensity of the wavefront to be corrected φ(r) from CCD, calculate MDS according to (2), and call it MDS0. (4) Get the corresponding far-field intensity of the wavefront aberration superimposed from CCD and calculate MDS according to (2).
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