3. Wave surface analysis

Controlling the wavefront is at the heart of adaptive optics. This control obviously relies on knowledge of the wave surface to be corrected. To measure it, optical control has been at the origin of the development of numerous methods. Adaptive optics has made a major contribution to improving these methods, as well as introducing new ones.

The methods used in adaptive optics are usually divided into two broad categories: interferometric techniques and methods based on geometrical optics. In practice, most of the methods used in adaptive optics can be described in terms of either of these two approaches, and this classification turns out to be rather artificial. A more interesting approach is to classify them according to the quantity actually measured: the phase (Smart interferometer, phase retrieval, phase diversity...), the phase gradient (shift interferometer,...