4. Optical correctors

The need to control the wavefront has led to the emergence of numerous technologies, such as deformable mirrors, liquid crystal modulators and liquid lenses. In AO, the choice of corrector must be guided by its ability to reproduce a time-varying aberration with a given degree of accuracy. The corrector's performance must therefore be analyzed in terms of its spatio-temporal characteristics. In this analysis, we focus on Deformable Mirrors (DM), whose advantages include achromaticity and the ability to correct numerous modes with a bandwidth generally far superior to that of the other solutions mentioned above. As such, they are used in the majority of AO systems. We also exclude so-called "active" mirrors, designed to correct quasi-static or slowly varying phenomena and associated with active optics, whose temporal characteristics are therefore significantly different. Numerous parameters...