In adaptive optics systems, to obtain a high-precision result, wave front reconstruction is used according to measurements of the Shack-Hartmann wavefront sensor based on zonal ideology. The zonal approach to reconstruction of the wave front has a good ability to reconstruct local details from the phase surface profile. This is important when correcting turbulent distortions of optical radiation using a segmented mirror, MEMS, and a spatial phase modulator. This paper presents in detail the features of the zonal approach to reconstruction of the wavefront based on measurements obtained by the Shack – Hartmann wavefront sensor.
The optical element in the Shack-Hartman wavefront sensor is a microlens raster, which breaks the light field with phase distortions in the approximation of geometric optics into partial beams. The phase fluctuations of the light field within the sub-aperture correspond to the fluctuations of two angles of arrival or the fluctuations of two local inclinations of the wave front within the same limits of the sub-aperture and are associated with correlation relations. In this case, the correlation is a quantitative measure of the "similarity" of the two corresponding phase distributions within the subaperture on the two analyzed Shack-Hartmann patterns. The paper presents the results of numerical experiments on the reconstruction of the wave front using the correlation approach to the centering of focal spots.
The weighted centers of gravity algorithm calculate the centroids coordinates of the Shack-Hartmann patterns which are recorded by the Shack-Hartmann wave front sensor in the process of adaptive correction of turbulent distortions of laser radiation. It is believed that the algorithm of weighted centers of gravity gives an optimal result regardless of the signalto-noise ratio for point sources. In addition to the algorithm for weighted centers of gravity of focal spots, there are other algorithms for centering the image in the plane of the receiving device. Here, based on numerical experiments, we give an estimate of the weighting and quadrant algorithms for centering the focal spots of the registered Shack-Hartmann pattern.
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