Closed-Loop Active Optics: Its Advantages And Limitations For Correction Of Wind-Buffet Deformations Of Large Flexible Mirrors

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Abstract
Wind buffet deformation of large flexible mirrors is, from its frequency bandpass and other characteristics, an overlap area between normal low bandpass "Active Optics" and high bandpass "Adaptive Optics". The fundamental problem posed is that the time frequencies involved do not permit the elimination of external seeing effects by appropriate time integrations with the image analyser, as in normal low bandpass closed-loop operation. Confusion between the wind deformation and atmospheric functions results. For wind buffet correction in these circumstances, we analyse the possibilities and limitations of the closed-loop principle using one or more image analysers in a number of configurations. Some important parameters of the atmospheric function apear to be insufficiently known and should be measured experimentally if rapid practical progress is to be made. Cross-checks betweens closed-loop and open-loop methods in a two-pronged approach seem highly desirable.© (1989) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

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