Adaptive Optics

Definition

Adaptive optics is a technique, used while performing visible or near-infrared imaging from a ground-based telescope, that improves the image quality that is otherwise degraded by the atmospheric turbulence. The wave-front distortions, measured on the studied object or a nearby star, are compensated by deforming a small, thin mirror at a speed higher than turbulence (1 kHz typically) (Fig. 1). The deformable mirror is conjugated to the pupil of the telescope. The use of this technique is mandatory in any method, such as coronagraphy, that aims at a direct imaging of exoplanets.

Fig. 1

Cartoon describing the principle of adaptive optics: The wave front deformed by atmospheric turbulence is corrected thanks to a deformable mirror that produces an inverse deformation several hundred times per second, after a device called a wave-front sensor has measured the residual distortion. A real-time computer is used to analyze the residuals and to define the proper surface to give to...