Seminari: Point-spread function reconstruction in ground-based ground astronomy + Medical Morphometry using Quasiconformal Teichmuller Theory

Venerdì 10 Luglio 2015, ore 10:00 - Aula 1BC50 - Raymond Honfu Chan + Ronald Lok Ming Lui



Venerdì 10 Luglio 2015 alle ore 10:00 in Aula 1BC50 si terranno i seguenti seminari:

Raymond Honfu Chan (Department of Mathematics, The Chinese University of Hong Kong)
"Point-spread function reconstruction in ground-based ground astronomy"

Ground-based astronomy refers to acquiring images of objects in outer space via ground-based telescopes. Because of atmospheric turbulence, images so acquired are blurry. One way to estimate the unknown blur or point spread function (PSF) is by using natural or artificial guide stars. Once the PSF is known, the images can be deblurred using well-known deblurring methods. Another way to estimate the PSF is to make use the aberration of wavefronts received at the telescope, i.e., the phase, to derive the PSF. However, the phase is not readily available; instead only its low-resolution gradients can be collected by wavefront sensors. In this talk, we will discuss how to use regularization methods to reconstruct high-resolution phase gradients and then use them to recover the phase and then the PSF in high accuracy. Our model can be solved efficiently by alternating direction method of multiplier whose convergence has been well established. Numerical results will be given to illustrate that our new model is efficient and give more accurate estimation for the PSF.

Ronald Lok Ming Lui (Department of Mathematics, The Chinese University of Hong Kong)
"Medical Morphometry using Quasiconformal Teichmuller Theory"

Medical morphometry is an important topic in medical imaging. Its goal is to systematically analyze anatomical structures of different subjects, and to generate diagnostic images to help doctors to visualise abnormalities for disease analysis. Quasiconformal (QC) Teichmuller theory, which studies the deformation patterns between shapes, is a useful tool for this purpose. In practice, anatomical structures are usually represented discretely by meshes. In this talk, I will firstly describe how QC theories can be implemented on discrete meshes, which gives a discrete analogue of QC geometry on surfaces. Then, I will talk about how computational QC geometry can be practically applied to medical imaging for disease analysis.

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