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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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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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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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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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Dirksen, P. (author), Braat, J. (author), Janssen, A.J.E.M. (author)
journal article 2006
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Serebriakov, A. (author), Bocoirt, F. (author), Braat, J. (author)
journal article 2005
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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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Vuelban, E.M. (author), Bhattacharya, N. (author), Braat, J. (author)
We propose and demonstrate a novel liquid based deformable mirror (LDM). The proposed LDM consists of an array of vertically oriented open capillary channels immersed in a pool of two immiscible liquids. A free-floating thin reflective membrane serves as the reflecting surface. By means of jet action, membrane deformation is induced. The control...
conference paper 2005
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Swinkels, B.L. (author), Bhattacharya, N. (author), Wielders, A.A. (author), Braat, J.J.M. (author)
Future space missions, among which the Darwin Space Interferometer, will consist of several free flying satellites. A complex metrology system is required to have all the components fly accurately in formation and have it operate as a single instrument. Our work focuses on a possible implementation of the sub-system that measures the absolute...
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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Dirksen, P. (author), Braat, J.J.M. (author), Janssen, A.J.E.M. (author), Leeuwesteijn, A. (author)
conference paper 2005
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Serebriakov, A. (author), Bociort, F. (author), Braat, J. (author)
In the year 2001 it was reported that the birefringence induced by spatial dispersion (BISD), sometimes also called intrinsic birefringence, had been measured and calculated for fluorides CaF2 and BaF2 in the deep UV range. It was also shown that the magnitude of the BISD in these cubic crystals is sufficiently large to cause serious problems...
conference paper 2005
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Koek, W.D. (author), Chan, V.S.S. (author), Ooms, T.A. (author), Bhattacharya, N. (author), Westerweel, J. (author), Braat, J.J.M. (author)
We present a novel holographic particle image velocimetry (HPIV) system using a reversible holographic material as the recording medium. In HPIV the three-dimensional flow field throughout a volume is detected by adding small tracer particles to a normally transparent medium. By recording the particle distribution twice with a known time shift...
conference paper 2005
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Bal, M.F. (author), Singh, M. (author), Braat, J.J.M. (author)
journal article 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
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