Optics 101

What is Adaptive Optics?

Jan 9 2008

Introduction
How Adaptive Optics Work?
Adaptive Optics in Astronomy

Introduction

Adaptive Optics can be defined as the optical systems that adapt to rectify optical effects that is caused by the medium between the object and its image. Adaptive optics leads to significantly sharper images by means of compensating for these optical effects.

How Adaptive Optics Work?

Adaptive optics systems work by calculating the shape of the distorted wavefront and re-impose the uniform wavefront by applying an opposite canceling distortion. This is usually accomplished by an adaptive optical element, which is normally a deformable mirror.

The requirements for an adaptive optics system include deformable mirrors, precision optics, special sensors and high-speed computers. High-speed computers are used to combine and control the entire system.

A point source of light is used by the adaptive optics system as a reference beam to precisely determine the distortion generated by the atmosphere. Next, electronics signals are sent to the deformable mirrors which can change shape to rapidly correct the distortions.

Figure 1. Neptune observed in the near infrared (1.65 microns) with adaptive optics (AO) (left) and without AO (right) (Image source National Science Foundation)

Adaptive Optics in Astronomy

Light is distorted from a distant galaxy or star as it passes through the turbulent atmosphere of the Earth. This prevents a telescope on the Earth¡¦s surface to form a sharp image. Adaptive optics is used in astronomy to reduce or eliminate these blurring effects of the atmosphere of the Earth.

An additional gain in contrast is the result of sharper images. This also leads to the detection and analysis of fainter objects such as stars where light levels are often very low. A bright reference beacon nearby is needed to image these very faint objects. The bright reference beacon permits the adaptive optics systems to study the effects of the atmosphere.