Adaptive optics ultimate performance and main concepts

Adaptive optics is now an operational reality which provides a real time compensation for turbulence degraded images. The degree of correction of an adaptive optics system is fundamentally limited by the flux density received from the object or from a guide source, and by atmospheric turbulence strength and speed. The ultimate performance which can be expected for ideal systems with an optimization of the key parameters are estimated. Two types of systems are routinely operated to date: a Hartmann-Shack wave-front sensor with a discrete actuator deformable mirror and a curvature wave- front sensor with a bimorph mirror. They are compared from physical and technological standpoints.