Searched for: subject%3A%22Phase%255C+retrieval%22
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Alaifari, Rima (author), Bartolucci, F. (author), Steinerberger, Stefan (author), Wellershoff, Matthias (author)
Gabor phase retrieval is the problem of reconstructing a signal from only the magnitudes of its Gabor transform. Previous findings suggest a possible link between unique solvability of the discrete problem (recovery from measurements on a lattice) and stability of the continuous problem (recovery from measurements on an open subset of R<sup>2...
journal article 2024
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Cools, Liam (author)
Counter-acting image quality degradation caused by phase aberrations through physical correction requires the phase field to be known. As imaging hardware captures real-valued intensity, defined as the wave amplitude squared, obtaining this lost phase information is known as the phase retrieval problem and is a non-linear and non-convex...
master thesis 2023
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Shen, Dong (author)
Deformable Mirror (DM) is the key part in the AO system. Characterization of DM is important as it maps between input voltage signal and output mirror deformation. The precision of characterization largely affects the control performance. While characterizing the DM with wavefront sensors is easy and straightforward, there is very few research...
master thesis 2023
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Alaifari, Rima (author), Bartolucci, F. (author), Wellershoff, Matthias (author)
Sampled Gabor phase retrieval — the problem of recovering a square-integrable signal from the magnitude of its Gabor transform sampled on a lattice — is a fundamental problem in signal processing, with important applications in areas such as imaging and audio processing. Recently, a classification of square-integrable signals which are not phase...
conference paper 2023
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Ansuinelli, P. (author)
The importance of inverse problems is paramount in science and physics because their solution provides information about parameters that cannot be directly observed. This thesis discusses and details the application of a few inverse methods in optical imaging, metrology and inspection of lithographic targets, particularly patterned structures on...
doctoral thesis 2022
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Soloviev, O.A. (author), Noom, J. (author), Nguyen, Hieu Thao (author), Vdovin, Gleb (author), Verhaegen, M.H.G. (author)
We investigate the general adjustment of projection-based phase retrieval algorithms for use with saturated data. In the phase retrieval problem, model fidelity of experimental data containing a non-zero background level, fixed pattern noise, or overexposure, often presents a serious obstacle for standard algorithms. Recently, it was shown...
conference paper 2022
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Liu, Runfei (author)
Phase Retrieval Problem is very common and has a lot of applications in fields such as microscope, astronomy, crystallography, optical imaging etc.. In this problem, PSF and the pupil function are given, and the goal is to reconstruct the phase of the object. For camera which has 8 bits color depth, the maximum number of colors that can be...
master thesis 2021
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Nguyen, Hieu Thao (author), Soloviev, O.A. (author), Verhaegen, M.H.G. (author)
We present the convergence analysis of convex combination of the alternating projection and Douglas–Rachford operators for solving the phase retrieval problem. New convergence criteria for iterations generated by the algorithm are established by applying various schemes of numerical analysis and exploring both physical and mathematical...
journal article 2021
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Nguyen, Hieu Thao (author), Soloviev, O.A. (author), Luke, Russell (author), Verhaegen, M.H.G. (author)
We develop for the first time a mathematical framework in which the class of projection algorithms can be applied to high numerical aperture (NA) phase retrieval. Within this framework, we first analyze the basic steps of solving the high-NA phase retrieval problem by projection algorithms and establish the closed forms of all the relevant...
journal article 2021
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Trevisan, E. (author)
Microscopic imaging has a resolution that is often far from the diffraction limit due to aberrations induced by the optics or by the sample itself. It is therefore of interest sensing these aberrations either directly or indirectly to improve image quality in post-processing or with adaptive optics. To avoid the use of extra hardware, several...
master thesis 2020
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Konijnenberg, A.P. (author)
In this thesis, several phase retrieval methods are discussed. Since the focus will mainly be on theory rather than experiment, the structure has been determined by the similarities and differences of the mathematics of these methods. For example, a distinction is made between non-iterative and iterative methods, and between single-shot...
doctoral thesis 2019
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Doelman, R. (author)
Aberrations in optical systems, such as telescopes and microscopes, degrade the quality of the images that can be produced by these systems. For example, an object that is positioned out of focus produces a blurred image on a camera sensor and the turbulent air in the earth’s atmosphere reduces the imaging performance of telescopes. In this...
doctoral thesis 2019
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Noppen, Marko (author)
Adaptive optics are widely used to correct the wavefront distortion imposed by atmospheric turbulence. Focal plane phase retrieval from intensity measurements has advantages due to the ease of implementation, potential broader application, less computations, low cost, high system bandwidth, simplified hardware and less calibration. To cope with...
master thesis 2019
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Dwivedi, P. (author)
Lenses are indispensable tool to perform imaging and see the small details of an object which was otherwise not possible. The smallest feature of an object that one can see using a lens depends on the numerical aperture (NA) of the lens and the used wavelength of light. For a fixed NA, the shorter the wavelength is, the smaller the features of...
doctoral thesis 2019
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Dwivedi, P. (author), Pereira, S.F. (author), Urbach, Paul (author)
Wavefront aberration measurements are required to test an extreme ultraviolet (EUV) imaging system. For a high-NA EUV imaging system, where conventional wavefront-sensing techniques show limitations, ptychography can be used for this purpose. However, at the wavelength region of EUV (i.e., 13.5 nm), the position accuracy of the scanning mask...
journal article 2019
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Ansuinelli, P. (author), Coene, W.M.J.M. (author), Urbach, Paul (author)
EUV lithography is the main candidate for patterning of future technology nodes. Its successful implementation depends on many aspects, among which the availability of actinic mask metrology tools able to inspect the patterned absorber in order to control and monitor the lithographic process. In this work, we perform a simulation study to...
conference paper 2019
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Dwivedi, P. (author), Konijnenberg, A.P. (author), Pereira, S.F. (author), Meisner, J.A. (author), Urbach, Paul (author)
Ptychography is a form of coherent diffractive imaging; it employs far-field intensity patterns of the object to reconstruct the object. In ptychography, an important limiting factor for the reconstructed image quality is the uncertainty in the probe positions. Here, we propose a new approach which uses the hybrid input-output algorithm and...
journal article 2019
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Konijnenberg, A.P. (author), Coene, W.M.J.M. (author), Urbach, Paul (author)
A noise-robust extension of iterative phase retrieval algorithms that does not need to assume a noise model is proposed. It works by adapting the intensity constraints using the reconstructed object. Using a proof-of-principle ptychographic experiment with visible light and a spatial light modulator to create an object, the proposed method is...
journal article 2018
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Gupta, Abhimanyu (author)
The use of radial basis function (RBF) expansion as a means to represent the generalized pupil function for aberration retrieval from intensity point-spread function has been investigated in this research article. The optimal choice of RBF hyper-parameters is derived empirically to achieve an increased accuracy of approximation along with well...
master thesis 2017
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Konijnenberg, A.P. (author)
An overview of several ptychographic phase retrieval methods and the theory behind them is presented. By looking into the theory behind more basic single-intensity pattern phase retrieval methods, a theoretical framework is provided for analyzing ptychographic algorithms. Extensions of ptychographic algorithms that deal with issues such as...
journal article 2017
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