11 August 2008 Interferometric null test of a parabolic reflector generating a Hertzian dipole field
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Interferometric surface tests of stigmatic aspherics can be carried out in a null test configuration. Null tests require reference null elements either plane or spherical surfaces or both. A parabolic reflector transforms a plane into a spherical wave which converges to the focus of the paraboloid. Therefore, a spherical ball lens or a steel ball can be placed into the focus enabling a double-pass geometry for the null test. Here a Fizeau interferometer geometry has been selected in order to guarantee invariance against polarization distortions under the assumption that radially polarized laser light is used for the interferometer. Radial polarized light is necessary to mimic a Hertzian dipole field. Due to the extreme solid angle produced by the paraboloid the alignment of the setup is very critical and needs auxiliary systems for the control. Aberrations caused by misalignments are removed via fitting of suitable functionals provided through ray-trace simulations. It turned out that the usual vector approximations fail under these extreme circumstances. Test results are given for a paraboloid with 2mm focal length transforming a plane wave into a near dipole wave comprising a solid angle of about 3,4π.
© (2008) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
G. Leuchs, G. Leuchs, K. Mantel, K. Mantel, A. Berger, A. Berger, H. Konermann, H. Konermann, M. Sondermann, M. Sondermann, U. Peschel, U. Peschel, N. Lindlein, N. Lindlein, J. Schwider, J. Schwider, } "Interferometric null test of a parabolic reflector generating a Hertzian dipole field", Proc. SPIE 7063, Interferometry XIV: Techniques and Analysis, 706314 (11 August 2008); doi: 10.1117/12.797423; https://doi.org/10.1117/12.797423

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