How do adaptive optics work

The most basic systems use a point source of light as a reference beacon , whose light is used to probe the shape of the wavefronts. This may be a bright star, or in the case of vision research a laser spot focused on the retina. Light from this reference source is analysed by a wavefront sensor , and then commands are sent to actuators pistons which change the surface of a deformable mirror to provide the necessary compensations.

As light from distant celestial objects enters our atmosphere it gets disturbed by our ever-moving atmosphere. Adaptive optics AO corrects for the distortions in an image caused by this atmospheric turbulence. The distortion to incoming light is shown schematically below. What effect does atmospheric turbulence have on an image of a star? The image below shows how what should effectively be a point source from a distant star is smeared out due to turbulence.

Adaptive optics compensates for this, resulting in a much sharper stellar image as seen on the right. Adaptive optics systems operate at high frequencies, typically about Hz. This is too fast for altering a primary mirror so adaptive optic systems are designed to act via the secondary mirror and additional optical elements placed in the light path.

The need for high speed computer calculations and special deformable mirrors means that AO is a relatively new field of development in astronomy.

Rapid progress in developing the technology for telescope use occurred following the end of the Cold War when much of the military technology for AO systems was declassified. There are several different methods that can be used to monitor and correct the incoming wavefront of light but many use a tip-tilt mirror and a thin, deformable one. The one shown below is used on Gemini North and has 85 actuators on it to control the mirror shape.

Vital to all is the need for powerful, fast computer processing and modelling of the incoming waveforms. Systems either rely on a bright reference star within the field of view which is surprisingly hard to find given the narrow field of view in many large telescopes or they produce an artificial reference star using a laser.

Australia is an active participant in the development of adaptive optic systems through the Research Network for Adaptive Optics. What are the most commonly used optical transmitters? What is a single mirror? What is a single lense? See all questions in Advanced Optics Applications.

Impact of this question views around the world. You can reuse this answer Creative Commons License. The Paranal Observatory has the most advanced and the largest number of adaptive optics systems in operation today. ESO's adaptive optics facilities have obtained top-notch scientific results. These include the first direct observations of an extrasolar planet near a bright star, as well as key characterisations of the black hole at the centre of the Milky Way. Also under development are advanced systems tailored to meet the challenges of the ELT, which will have a revolutionary metre-class diameter primary mirror.

Significant recent progress has also paved the way for attaining a wider corrected field of view, a result that will have an impact on the design of future VLT and ELT adaptive optics systems. Select Language en. Science User Portal. Subscribe Contact Site Map.