Speckle imaging

Speckle imaging comprises a range of high-resolution astronomical imaging techniques based on the analysis of large numbers of short exposures that freeze the variation of atmospheric turbulence. They can be divided into the shift-and-add ("image stacking") method and the speckle interferometry methods. These techniques can dramatically increase the resolution of ground-based telescopes, but are limited to bright targets. Explanation The principle of all the techniques is to take very short exposure images of astronomical targets, and then process those so as to remove the effects of astronomical seeing. Use of these techniques led to a number of discoveries, including thousands of binary stars that would otherwise appear as a single star to a visual observer working with a similar-sized telescope, and the first images of sunspot-like phenomena on other stars. Many of the techniques remain in wide use today, notably when imaging relatively bright targets. The resolutio

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Divertor Erosion Monitoring in ITER Using Two-Wavelength Speckle Interferometry

Eric Gauthier, Pierre Jacquot

ITER will operate long-time discharges (400 s) at high performances (Q = 10) and will have to satisfy strong safety and operational limits in term of tritium and dust inventory. This implies to control the erosion of the plasma facing components. Erosion monitoring diagnostic based on speckle interferometry and an optical design with its implementation in ITER are presented.

Ieee-Inst Electrical Electronics Engineers Inc2014

High resolution displacement detection by speckle pattern analysis : accuracy limits in linear displacement speckle metrology

Hans Peter Herzig, Toralf Scharf

We propose a simple reflection measurement setup and a motion evaluation procedure based on a two dimensional recording of subsequent speckle images. The averaging of cross correlation functions is used to measure displacements. We demonstrate experimentally a 10 nm precision on a 50 μm measurement range limited by systematical errors. An image library is proposed to extend the measurement range. Limitations are given and documented improvements predicted an accuracy better than 5 nm over a range of 150 μm.

European Optical Society2010

Imaging through multimode fibers using deep learning: The effects of intensity versus holographic recording of the speckle pattern

Navid Borhani, Eirini Kakkava, Georgia Konstantinou, Damien Claude-Marie Loterie, Christophe Moser, Demetri Psaltis, Babak Rahmani, Ugur Tegin

Information transmission through multimode fibers (MMFs) has been a topic of great interest for many years. Deep learning algorithms have been applied successfully to MMFs in particular to fiber endoscopy. In this work, we show how Deep Neural Networks (DNNs) can be a versatile technique for classification and recovery of input images that have been significantly distorted while propagating along the MMF forming a speckle pattern. A comparison between holographic and intensity-only recording of the speckle output, which is used as an input to the DNNs, shows that high performance can be achieved without having the full field information (amplitude and phase). Impressive reconstruction fidelity and classification accuracy of the fiber inputs from the intensity-only images of the speckle patterns is reported.

ELSEVIER SCIENCE INC2019

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