Wave-front sensing for adaptive optics in astronomy

Since the invention of the telescope, astronomers have been ableto view fainter and smaller objects in the sky. The mainlimitation to the quality of the images obtained has been, untilrecently, the presence of turbulence in the atmosphere. Tomitigate the effects of the turbulence, adaptive optics systemshave been successfully implemented. Adaptive optics relies uponmeasuring the distortion of the wave-front caused by theatmospheric turbulence, called wave-front sensing, andcompensating for it in an adaptive fashion. The aim of this thesisis to provide a summary of the state-of-the-art of wave-frontsensing and to describe my contributions to the field.The most significant result in the thesis is the derivation of a new wave-front sensing technique.This approach uses the geometric optics approximation, which considers light to travelperpendicular to the wave-front. Consequently, a wave-front slope in a region of the telescopeaperture causes the displacement of a ray of light passing through that region. By taking twodefocused images, it is possible to deduce how the light intensity changed from one image to theother.