Searched for: collection%3Air
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document
Slob, E.C. (author), Wapenaar, C.P.A. (author)
We present a three-dimensional scheme that can be used to compute the electromagnetic impulse response between any two subsurface points from surface reflection data measured at a single surface of a lossless medium. The scheme first computes a virtual vertical radar profile using the Marchenko scheme from which focusing wavefields are...
conference paper 2017
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Naghibzadeh, S. (author), Mouri Sardarabadi, A. (author), van der Veen, A.J. (author)
Image formation using the data from an array of sensors is a familiar problem in many fields such as radio astronomy, biomedical and geodetic imaging. The problem can be formulated as a least squares (LS) estimation problem and becomes ill-posed at high resolutions, i.e. large number of image pixels. In this paper we propose two regularization...
conference paper 2016
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Verdel, Arie (author), Wedemeijer, Harry (author), Paap, B (author), Vandeweijer, Vincent (author), Weemstra, C. (author), Jousset, Philippe (author), Franke, Steven (author), Blanck, Hanna (author), Águstsson, K. (author), Hersir, Gylfi Páll (author)
We present results from the application of ambient noise seismic interferometry (ANSI) to data that were recorded continuously in 2014 and 2015 at Iceland’s peninsula Reykjanes. The objective of this study is the retrieval of reflected body waves (P-waves) that provide high-resolution velocity-versus-depth as well as subsurface structural...
conference paper 2016
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Hartstra, I.E. (author), Wapenaar, C.P.A. (author)
We discuss a method to interferometrically retrieve the body wave reflection response from local high-frequency scattering coda wave fields with the purpose to obtain an input dataset suitable for the application of advanced exploration-type imaging methods
conference paper 2015
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Slob, E.C. (author), Hunziker, J.W. (author), Thorbecke, J.W. (author), Wapenaar, C.P.A. (author)
conference paper 2014
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Nitti, D.O. (author), Hanssen, R.F. (author), recife, A. (author), Bovenga, F. (author), Milillo, G. (author), Nutricato, R. (author)
Image alignment is without doubt the most crucial step in SAR Interferometry. Interferogram formation requires images to be coregistered with an accuracy of better than 1/8 pixel to avoid significant loss of phase coherence. Conventional interferometric precise coregistration methods for full-resolution SAR data (Single-Look Complex imagery, or...
conference paper 2008
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Spronck, J.F.P. (author), Los, J.W.N. (author), Pereira, S.F. (author)
The optical properties of materials are wavelength-dependent. This property, called dispersion, affects the performance of a wide-band nulling interferometer by inducing wavelength-dependent phase differences between the arms of the interferometer. In this paper, we analyze the influence of dispersion in nulling interferometers for exoplanet...
conference paper 2008
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Spronck, J. (author), Pereira, S.F. (author), Braat, J.J.M. (author)
We show the theoretical limitations of a multi-axial nulling interferometer with respect to longitudinal polarization. We furthermore analyze the filtering capabilities of a single-mode fiber in this case.
conference paper 2007
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Spronck, J. (author), Vosteen, L.L.A. (author), Pereira, S.F. (author), Braat, J.J.M. (author)
We present the design of a new testbed experiment to demonstrate nulling interferometry using polarization properties. This three-beam set-up is perfectly symmetric with respect to the number of reflections and transmissions and should therefore allow a high rejection ratio in a wide spectral band.
conference paper 2007
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Spronck, J. (author), Pereira, S.F. (author), Braat, J.J.M. (author)
We present a new type of nulling interferometer that makes use of polarization properties to have on-axis destructive interference. The proposed design, which only involves commercial components and no achromatic device, is also suitable for internal modulation. This type of interferometer should enable a high rejection ratio in a theoretically...
conference paper 2006
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Spronck, J. (author), Pereira, S.F. (author), Braat, J.J.M. (author)
We discuss the previously-reported measurements of a three-beam nulling interferometer without achromatic phase-shifters, using delay lines only. The theoretical rejection ratio of a few thousand has not been achieved experimentally. In order to explain the obtained results, some direct spectral and polarization measurements have been performed....
conference paper 2006
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Van der Avoort, C. (author), Den Herder, J.W. (author), Braat, J. (author)
This paper compares two well-known types of interferometer arrays for optical aperture synthesis. An analytical model for both types describes the expected output, in terms of photon counts. The goal is to characterize the performance of both types of array for blind imaging of a wide-field or extended object that would be partially resolved by...
conference paper 2005
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Soloviev, O. (author), Vdovin, G. (author)
This article presents a prototype of a CMOS phase sensor for high accuracy (1 Angstrom) heterodyne interferometry. Switched integrators realization of a lock-in pixel for 4-bucket phase detection algorithm is described and illustrated by experimental results. Factors that limit the accuracy of this implementation and possible ways for its...
conference paper 2005
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Krieg, M.L. (author), Braat, J.J.M. (author)
A previously reported interferometer without intermediate optics is used to perform measurements on an aspherical extreme ultraviolet lithography mirror substrate. Acousto-optic modulation based phase shifting is used together with a novel phase retrieval algorithm to retrieve the phase distribution from our interferograms. The phase...
conference paper 2005
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Soloviev, O. (author), Vdovin, G. (author)
We propose an algorithm for phase retrieval from three interferograms which differ only by an arbitrary unknown tilt terms in the phase. The method is illustrated by examples.
conference paper 2005
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Van der Avoort, C. (author), Van Brug, H. (author), Den Herder, J.W. (author), d'Arcio, L. (author), Le Poole, R. (author), Braat, J. (author)
Homothetic mapping is an aperture synthesis technique that allows interferometric imaging over a wide fieldof-view. A laboratory experiment was set up to demonstrate the feasibility of this technique. Here, we present the first static experiments on homothetic mapping that have been done on the Delft Testbed for Interferometry (DTI). Before a...
conference paper 2004
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Montilla, I. (author), Pereira, S.F. (author), Braat, J.J.M. (author)
Wide field interferometry has become a subject of increasing interest in the recent years. New methods have been suggested in order to avoid the drawbacks of the standard wide field method (homothetic mapping) which is not applicable when the aperture is highly diluted; for this reason imaging with non-homothetic arrays is being extensively...
conference paper 2004
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Van der Avoort, C. (author), Mieremet, A. (author), Pereira, S. (author), Braat, J. (author)
We present results of experiments obtained using a new nulling technique that enables deep nulling without the use of achromatic phase shifters. The experimental set-up consists of a three-beam interferometer that should provide a nulling depth of several thousands over a wavelength range of 500 to 650 nm. The intended depth of null was not...
conference paper 2004
document
Krieg, M.L. (author), Braat, J.J.M. (author)
This paper will illustrate several approaches to retrieving the shape of aspherical reflective surfaces as used in EUV Lithography, from measurements from a previously reported angstrom-accuracy interferometer. First, the working principles of the interferometer will be reviewed, and typical measurement data expected from the instrument will be...
conference paper 2004
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