Adaptive optics with segmented deformable bimorph mirrors

The degradation of astronomical images caused by atmospheric turbulence will be much more severe in the next generation of terrestrial telescopes and its compensation will require deformable mirrors with up to tens-of-thousands of actuators.Current designs for these correctors consist of scaling up the proven technologies of flexible optical plates deformed under the out-of-plane action of linear actuators. This approach will lead to an exponential growth of cost with the number of actuators, and in very complex mechanisms.This thesis proposes a new concept of optical correction which is modular, robust, lightweight and low-cost and is based on the bimorph in-plane actuation.The adaptive mirror consists of segmented identical hexagonal bimorph mirrors allowing to indefinitely increase the degree of correction while maintaining the first mechanical resonance at the level of a single segment and showing an increase in price only proportional to the number of segments.Each bimorph segment can be mass-produced by simply screen-printing an array of thin piezoelectric patches onto a silicon wafer resulting in very compact and lightweight modulesand at a price essentially independent from the number of actuators.The controlled deformation of a screen-printed bimorph mirror was experimentally achieved with meaningful optical shapes and appropriate amplitudes; its capability for compensating turbulence was evaluated numerically. The generation of continuous surfacesby an assembly of these mirrors was numerically simulated and a demonstrator of concept consisting of 3 segments was constructed.Doctorat en Sciences de l'ingénieur