Telescopes and Pyramids

My name is Victoria Hutterer and I am currently working as a member of the Austrian Adaptive Optics Group in Industrial Mathematics at the Johannes Kepler University in Linz. My research is mainly concerned with wavefront reconstruction from pyramid wavefront sensor data in astronomical Adaptive Optics.

Adaptive Optics:
Due to diffraction of light and turbulences in the atmosphere, images of objects on the sky suffer from distortions  when they are observed by earthbound telescopes.
Adaptive Optics (AO) is a technology that compensates for the rapidly changing optical perturbations arising during the imaging process and physically corrects for atmospheric blurring via deformable mirrors in real-time. The correction usually is split into two steps: First, the distorted wavefronts of a guide star, which is situated near the astronomical object one wants to observe, are measured by wavefront sensors. The obtained information is then used to calculate the actuator commands of the deformable mirror in order to optimally balance the aberrations by shaping the mirror appropriately. Unfortunately, the incoming light cannot be measured directly. Reconstruction of the unknown wavefront and further calculation of the optimal mirror deformations from given sensor measurements is an inverse problem which has to be solved within milliseconds.

The pyramid wavefront sensor:
One type of wavefront sensor nowadays in high demand for the generation of Extremely Large Telescopes (ELTs) is the so called pyramid wavefront sensor. The Fourier optics based model of the sensor is complex and highly non-linear. My focus lies on a detailed mathematical analysis of the pyramid sensor model followed by the application of sophisticated methods from the field of inverse problems in order to perform fast and accurate wavefront reconstruction.


Figure: Sketch of a pyramid wavefront sensor. Source: The Optical Society

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