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Braat, J.J.M. (author), Janssen, A.J.E.M. (author)
Various authors have presented the aberration function of an optical system as a power series expansion with respect to the ray coordinates in the exit pupil and the coordinates of the intersection point with the image field of the optical system. In practical applications, for reasons of efficiency and accuracy, an expansion with the aid of...
journal article 2013
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Van Haver, S. (author), Braat, J.J.M. (author), Pereira, S.F. (author)
We propose a measurement approach that allows the determination of aberrations of a microlens by analyzing the through-focus intensity image it produces when the object is a point source. To simulate image formation by a microlens we apply the extended version of the Nijboer-Zernike diffraction theory (ENZ) that uses the Debye diffraction...
conference paper 2010
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Cui, M. (author), Zeitouny, M.G. (author), Bhattacharya, N. (author), Van den Berg, S.A. (author), Urbach, H.P. (author), Braat, J.J.M. (author)
We experimentally demonstrate that a femtosecond frequency comb laser can be applied as a tool for longdistance measurement in air. Our method is based on the measurement of cross correlation between individual pulses in a Michelson interferometer. From the position of the correlation functions, distances of up to 50 m have been measured. We...
journal article 2009
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Braat, C.C.M. (author), Landwehr, J.C. (author), Lambert, J.W.M. (author)
Grondwaterstandsveranderingen brengen knelpunten en kansen met zich mee. Om een betere globale inschatting te kunnen maken zal een effectenanalyse methode hulp bieden. In dit rapport is een effectenanalysemethode uitgedacht voor grondwaterstandsverandering. Het doel van deze studie is het geven van een aanzet en richting voor het uitwerken van...
report 2009
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Van Haver, S. (author), Braat, J.J.M. (author), Janssen, A.J.E.M. (author), Janssen, O.T.A. (author), Pereira, S.F. (author)
We present details of a novel imaging algorithm based on the extended Nijboer–Zernike (ENZ) theory of diffraction. We derive integral expressions relating the electric field distribution in the entrance pupil of an optical system to the electric field in its focal region. The evaluation of these integrals is made possible by means of a highly...
journal article 2009
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Braat, J. (author)
public lecture 2008
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Sluijter, M. (author), De Boer, D.K.G. (author), Braat, J.J.M. (author)
Uniaxial optical anisotropy in the geometrical-optics approach is a classical problem, and most of the theory has been known for at least fifty years. Although the subject appears frequently in the literature, wave propagation through inhomogeneous anisotropic media is rarely addressed. The rapid advances in liquid-crystal lenses call for a good...
journal article 2008
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Van Haver, S. (author), Janssen, O.T.A. (author), Braat, J.J.M. (author), Janssen, A.J.E.M. (author), Urbach, H.P. (author), Pereira, S.F. (author)
In this paper we introduce a new mask imaging algorithm that is based on the source point integration method (or Abbe method). The method presented here distinguishes itself from existing methods by exploiting the through-focus imaging feature of the Extended Nijboer-Zernike (ENZ) theory of diffraction. An introduction to ENZ-theory and its...
conference paper 2008
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Janssen, O.T.A. (author), Van Haver, S. (author), Janssen, A.J.E.M. (author), Braat, J.J.M. (author), Urbach, H.P. (author), Pereira, S.F. (author)
Results are presented of mask imaging using the Extended Nijboer-Zernike (ENZ) theory of diffraction. We show that the efficiency of a mask imaging algorithm, derived from this theory, can be increased. By adjusting the basic Finite Difference Time Domain (FDTD) algorithm, we can calculate the near field of isolated mask structures efficiently,...
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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Van der Avoort, C. (author), Pereira, S.F. (author), Braat, J.J.M. (author), Den Herder, J.W. (author)
In optical aperture-synthesis imaging of stellar objects, different beam combination strategies are used and proposed. Coaxial Michelson interferometers are very common and a homothetic multiaxial interferometer is recently realized in the Large Binocular Telescope. Laboratory experiments have demonstrated the working principles of two new...
journal article 2007
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Vuelban, E.M. (author), Bhattacharya, N. (author), Braat, J.M. (author)
Recently, a new type of liquid based deformable mirror has been proposed and demonstrated. The device consists of an array of vertically oriented open capillary channels immersed in a pool of two immiscible liquids and a freefloating reflective membrane, which serves as the reflecting surface. Liquid surface and membrane deformations are...
conference paper 2006
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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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Spronck, J. (author), Pereira, S.F. (author), Braat, J.J.M. (author)
We introduce a new concept of nulling interferometer without any achromatic device, using polarization properties of light. This type of interferometer should enable a high rejection ratio in a theoretically unlimited spectral band. We analyze several consequences of the proposed design, notably, the possibility of fast internal modulation.
journal article 2006
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Dirksen, P. (author), Braat, J.J.M. (author), Janssen, A.J.E.M. (author), Leeuwestein, A. (author), Matsuyama, T. (author), Noda, T. (author)
Phase Measurement Interferometers (PMI) are widely used during the manufacturing process of high quality lenses. Although they have an excellent reproducibility and sensitivity, the set-up is expensive and the accuracy of the measurement needs to be checked frequently. This paper discusses an alternative lens metrology method that is based on an...
conference paper 2006
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Vuelban, E.M. (author), Bhattacharya, N. (author), Braat, J.J.M. (author)
We propose and demonstrate a novel liquid deformable mirror, based on electrocapillary actuation, for highorder wavefront correction. The device consists of a two-dimensional array of vertically oriented microchannels filled with two immiscible liquids, an aqueous electrolyte, and a viscous dielectric liquid, where the dielectric liquid...
journal article 2006
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Spronck, J. (author), Pereira, S.F. (author), Braat, J.J.M. (author)
We introduce the concept of chromatism compensation in nulling interferometry that enables a high rejection ratio in a wide spectral band. Therefore the achromaticity condition considered in most nulling interferometers can be relaxed. We show that this chromatism compensation cannot be applied to a two-beam nulling interferometer, and we make...
journal article 2006
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Dirksen, P. (author), Braat, J. (author), Janssen, A.J.E.M. (author)
journal article 2006
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