Concept

Ptychographie

Publications associées (12)

Phase Retrieval: From Computational Imaging to Machine Learning: A tutorial

Michaël Unser, Thanh-An Michel Pham, Jonathan Yuelin Dong

Phase retrieval consists in the recovery of a complex-valued signal from intensity-only measurements. As it pervades a broad variety of applications, many researchers have striven to develop phase-retrieval algorithms. Classical approaches involve techniqu ...

2023

Phase Reconstruction of Low-Energy Electron Holograms of Individual Proteins

Klaus Kern, Stephan Rauschenbach, Sven Alexander Szilagyi, Hannah Julia Ochner

Low-energy electron holography (LEEH) is one of the few techniques capable of imaging large and complex three-dimensional molecules, such as proteins, on the single molecule level at subnanometer resolution. During the imaging process, the structural infor ...

AMER CHEMICAL SOC2022

Stochasticity helps to navigate rough landscapes: comparing gradient-descent-based algorithms in the phase retrieval problem

Lenka Zdeborová, Francesca Mignacco

In this paper we investigate how gradient-based algorithms such as gradient descent (GD), (multi-pass) stochastic GD, its persistent variant, and the Langevin algorithm navigate non-convex loss-landscapes and which of them is able to reach the best general ...

IOP PUBLISHING LTD2021

3D nanometrology of transparent objects by phase calibration of a basic bright-field microscope for multiple illumination apertures

Martinus Gijs, Daniel Migliozzi, Bingying Zhao

Optical retrieval of the structure of transparent objects at the nanoscale requires adapted techniques capable of probing their interaction with light. Here, we considered a method based on calibration of the defocusing with partially coherent illumination ...

2020

Cellular Dynamics and Three-Dimensional Refractive Index Distribution Studied with Quantitative Phase Imaging

Nicolas Pavillon

We present in this PhD thesis work various applications of digital holographic microscopy (DHM), an imaging technique based on coherent illumination which enables the recovery of the full complex wavefront, i.e. the amplitude and phase of a wave field whic ...

EPFL2011

Performance Analysis of Reconstruction Techniques for Frequency-Domain Optical-Coherence Tomography

Michaël Unser, Chandra Sekhar Seelamantula

We address the issue of noise robustness of reconstruction techniques for frequency-domain optical-coherence tomography (FDOCT). We consider three reconstruction techniques: Fourier, iterative phase recovery, and cepstral techniques. We characterize the re ...

Institute of Electrical and Electronics Engineers2010

Phase Retrieval and Gaussian Beam Mode Decomposition of Gyrotron Beams

In this dissertation, we have developed the necessary basis for the characterization of the RF output of a gyrotron. The characterization includes the phase reconstruction and Gaussian beam mode decomposition. In order to analyze the phase reconstruction i ...

EPFL2010

Theoretical Investigation of Iterative Phase Retrieval Algorithm for Quasi-Optical Millimeter-Wave RF Beams

Stefano Alberti, Jean-Philippe Hogge

In this paper, we present a detailed analysis of the iterative phase retrieval approach (TPRA) for determining the phase profile of the output microwave beam of a gyrotron from known intensity patterns emphasizing the field propagation techniques which are ...

IEEE2009

Diffractive imaging for periodic samples: retrieving one-dimensional concentration profiles across microfluidic channels

Christian David

A technique has been developed that allows determination of the concentration profiles of colloidal solutions or any kind of fluid under confinement. Currently, submicrometre-wide channels are sampled with a resolution in the 10 nm range. The method compri ...

2007

Confinement-induced liquid ordering investigated by x-ray phase retrieval

Hairun Guo, Christian David

Using synchrotron x-ray diffraction, we have determined the ensemble-averaged density profile of colloidal fluids within confining channels of different widths. We observe an oscillatory ordering-disordering behavior of the colloidal particles as a functio ...

2007

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