Increasing the corrected field of view of an adaptive optical telescope.

摘要

Current adaptive optical telescope designs use a single deformable mirror (DM), usually conjugated to the telescope pupil, to compensate for the cumulative effects of optical turbulence along a single observation direction. The corrected field of view (FOV) of an adaptive optics system could theoretically be increased through the use of multiple DMs optically conjugated to a like number of corresponding planes which sample the turbulence region in altitude. Often, the atmospheric turbulence responsible for the degradation of long-exposure telescope images is concentrated in several relatively strong layers. The logical location for the conjugate planes in a multiconjugate adaptive optics (MCAO) system would be the same as these "seeing layers." Each DM would correct for the component of the total wavefront in the pupil contributed by its corresponding turbulent layer. If the atmosphere does not possess a distinctly layered structure, the best fit of the turbulence profile can be made to a layered model, with the number of layers in the model equal to the number of DMs. This dissertation describes and analyzes two novel methods for estimating the proper DM surfaces which would result in wide-FOV compensation. Both methods take advantage of spatial diversity in multiple wavefront sensor (WFS) measurements in order to reconstruct an estimate of the three-dimensional turbulence structure. The wavefront measurements are made using an array of artificial guide stars created by scattered laser light. The analysis includes the integrated effects of measurement noise, realistic models of systems components, and the limitations of artificial guide stars. It is shown that multiple-DM, multiple-guide-star systems can significantly increase the compensated FOV relative to single-DM, single-guide star systems.