The Experts below are selected from a list of 291 Experts worldwide ranked by ideXlab platform
Norbert Lindlein - One of the best experts on this subject based on the ideXlab platform.
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interferometric grazing incidence test of rough steep convex spherics experimental data analysis
Applied Optics, 2021Co-Authors: Sergej Rothau, Klaus Mantel, Norbert LindleinAbstract:Grazing incidence interferometry has been applied to plane, cylindrical, acylindrical, and general rod-like surfaces using diffractive beam splitters. Here, in a first step towards measuring Aspherics, we demonstrate that also rough convex steep rotationally symmetric spherics can be measured along one meridian in a single step using diffractive beam splitters and phase shifting techniques. The measurement of rough surfaces is possible, i.e., without the need to polish the surfaces, due to the large effective wavelength (λeff≈10µm) of the test. We include, besides the short recapitulation of the measurement principle and experimental setup, a presentation of the measured data of one small meridian region for the special case of spherical objects under test. The subsequent data analysis combined with suitable simulations focuses on elimination of the misalignment aberrations from the results caused by specimen displacements in the setup.
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grazing incidence interferometry for rough convex Aspherics
arXiv: Optics, 2016Co-Authors: Johannes Schwider, Norbert Lindlein, Christine Kellermann, Sergej Rothau, Klaus MantelAbstract:Grazing incidence interferometry has been applied to rough planar and cylindrical surfaces. As suitable beam splitters diffractive optical phase elements are quite common because these allow for the same test sensitivity for all surface points. But a rotational-symmetric convex aspheric has two curvatures which reduces the measurable region to a meridian through the vortex of the aspheric, which is in contrast to cylindrical surfaces having a one-dimensional curvature which allows the test of the whole surface in gracing incidence. The meridional limitation for rotational-symmetric Aspherics nevertheless offers the possibility to measure single meridians in a one-step measurement. An extension to the complete surface can be obtained by rotating the aspheric around its vortex within the frame of the test interferometer.
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interferometric quasi absolute tests for Aspherics using a radial shear position
Optics Letters, 2009Co-Authors: Klaus Mantel, Eduard Geist, Irina Harder, Norbert Lindlein, Gerd LeuchsAbstract:Increasing accuracy requirements in aspheric metrology make the development of absolute testing procedures for aspheric surfaces important. One strategy is transferring the standard practice three-position test for spheres to Aspherics. The three-position test, however, involves a cat's eye position and therefore has certain drawbacks. We propose an absolute testing method for rotationally symmetric Aspherics where the cat's eye position is replaced with a radially sheared position. Together with rotational movements of the specimen, the surface deviations can be obtained in an absolute manner. To demonstrate the validity of the procedure, we present a measurement result for a sphere and compare it with a result obtained by the standard three-position test.
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design considerations for the absolute testing approach of Aspherics using combined diffractive optical elements
Applied Optics, 2007Co-Authors: Gufran S Khan, Klaus Mantel, Irina Harder, Norbert Lindlein, Johannes SchwiderAbstract:Aspheric optical surfaces are often tested using diffractive optics as null elements. For precise measurements, the errors caused by the diffractive optical element must be calibrated. Recently, we reported first experimental results of a three position quasi-absolute test for rotationally invariant Aspherics by using combined-diffractive optical elements (combo-DOEs). Here we investigate the effects of the DOE substrate errors on the proposed calibration procedure and present a set of criteria for designing an optimized combo-DOE. It is demonstrated that this optimized design enhances the overall consistency of the procedure. Furthermore, the rotationally varying part of the surface deviations is compared with the rotationally varying deviations obtained by an N-position averaging procedure and is found to be in good agreement.
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dual wave front computer generated holograms for quasi absolute testing of Aspherics
Applied Optics, 2002Co-Authors: Mathias Beyerlein, Norbert Lindlein, Johannes SchwiderAbstract:Testing of Aspherics by means of computer-generated holograms (CGHs) is well known. To perform a quasi-absolute test of rotationally symmetric aspheric surfaces, two wave fronts must be encoded in the CGH. Both the null lens and a spherical lens have to be stored. This enables successive measurements of the aspheric and of a cat's-eye position without changing the object arm of the interferometer. Two possibilities for encoding both wave fronts have been investigated. A first-order approximation for estimating the influence of disturbing diffraction orders is given.
Emmanuel Hugot - One of the best experts on this subject based on the ideXlab platform.
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Stress mirror polishing for future large lightweight mirrors: design using shape optimization
Optics Express, 2020Co-Authors: Sabri Lemared, Marc Ferrari, Christian Jeu, Thibault Dufour, Nathalie Soulier, Emmanuel HugotAbstract:This study proposes a new way to manufacture large lightweight Aspherics for space telescopes using Stress Mirror Polishing (SMP). This technique is well known to allow reaching high quality optical surfaces in a minimum time period, thanks to a spherical full-size polishing tool. To obtain the correct surface' aspheric shape, it is necessary to define precisely the thickness distribution of the mirror to be deformed, according to the manufacturing parameters. We first introduce active optics and Stress Mirror Polishing techniques, and then, we describe the process to obtain the appropriate thickness mirror distribution allowing to generate the required aspheric shape during polishing phase. Shape optimization procedure using PYTHON programing and NASTRAN optimization solver using Finite Element Model (FEM) is developed and discussed in order to assist this process. The main result of this paper is the ability of the shape optimization process to support SMP technique to generate a peculiar aspherical shape from a spherical optical surface thanks to a thickness distribution reshaping. This paper is primarily focused on a theoretical framework with numerical simulations as the first step before the manufacturing of a demonstrator. This "two-steps" approach was successfully used for previous projects.
Klaus Mantel - One of the best experts on this subject based on the ideXlab platform.
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interferometric grazing incidence test of rough steep convex spherics experimental data analysis
Applied Optics, 2021Co-Authors: Sergej Rothau, Klaus Mantel, Norbert LindleinAbstract:Grazing incidence interferometry has been applied to plane, cylindrical, acylindrical, and general rod-like surfaces using diffractive beam splitters. Here, in a first step towards measuring Aspherics, we demonstrate that also rough convex steep rotationally symmetric spherics can be measured along one meridian in a single step using diffractive beam splitters and phase shifting techniques. The measurement of rough surfaces is possible, i.e., without the need to polish the surfaces, due to the large effective wavelength (λeff≈10µm) of the test. We include, besides the short recapitulation of the measurement principle and experimental setup, a presentation of the measured data of one small meridian region for the special case of spherical objects under test. The subsequent data analysis combined with suitable simulations focuses on elimination of the misalignment aberrations from the results caused by specimen displacements in the setup.
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grazing incidence interferometry for rough convex Aspherics
arXiv: Optics, 2016Co-Authors: Johannes Schwider, Norbert Lindlein, Christine Kellermann, Sergej Rothau, Klaus MantelAbstract:Grazing incidence interferometry has been applied to rough planar and cylindrical surfaces. As suitable beam splitters diffractive optical phase elements are quite common because these allow for the same test sensitivity for all surface points. But a rotational-symmetric convex aspheric has two curvatures which reduces the measurable region to a meridian through the vortex of the aspheric, which is in contrast to cylindrical surfaces having a one-dimensional curvature which allows the test of the whole surface in gracing incidence. The meridional limitation for rotational-symmetric Aspherics nevertheless offers the possibility to measure single meridians in a one-step measurement. An extension to the complete surface can be obtained by rotating the aspheric around its vortex within the frame of the test interferometer.
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interferometric quasi absolute tests for Aspherics using a radial shear position
Optics Letters, 2009Co-Authors: Klaus Mantel, Eduard Geist, Irina Harder, Norbert Lindlein, Gerd LeuchsAbstract:Increasing accuracy requirements in aspheric metrology make the development of absolute testing procedures for aspheric surfaces important. One strategy is transferring the standard practice three-position test for spheres to Aspherics. The three-position test, however, involves a cat's eye position and therefore has certain drawbacks. We propose an absolute testing method for rotationally symmetric Aspherics where the cat's eye position is replaced with a radially sheared position. Together with rotational movements of the specimen, the surface deviations can be obtained in an absolute manner. To demonstrate the validity of the procedure, we present a measurement result for a sphere and compare it with a result obtained by the standard three-position test.
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design considerations for the absolute testing approach of Aspherics using combined diffractive optical elements
Applied Optics, 2007Co-Authors: Gufran S Khan, Klaus Mantel, Irina Harder, Norbert Lindlein, Johannes SchwiderAbstract:Aspheric optical surfaces are often tested using diffractive optics as null elements. For precise measurements, the errors caused by the diffractive optical element must be calibrated. Recently, we reported first experimental results of a three position quasi-absolute test for rotationally invariant Aspherics by using combined-diffractive optical elements (combo-DOEs). Here we investigate the effects of the DOE substrate errors on the proposed calibration procedure and present a set of criteria for designing an optimized combo-DOE. It is demonstrated that this optimized design enhances the overall consistency of the procedure. Furthermore, the rotationally varying part of the surface deviations is compared with the rotationally varying deviations obtained by an N-position averaging procedure and is found to be in good agreement.
Johannes Schwider - One of the best experts on this subject based on the ideXlab platform.
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grazing incidence interferometry for rough convex Aspherics
arXiv: Optics, 2016Co-Authors: Johannes Schwider, Norbert Lindlein, Christine Kellermann, Sergej Rothau, Klaus MantelAbstract:Grazing incidence interferometry has been applied to rough planar and cylindrical surfaces. As suitable beam splitters diffractive optical phase elements are quite common because these allow for the same test sensitivity for all surface points. But a rotational-symmetric convex aspheric has two curvatures which reduces the measurable region to a meridian through the vortex of the aspheric, which is in contrast to cylindrical surfaces having a one-dimensional curvature which allows the test of the whole surface in gracing incidence. The meridional limitation for rotational-symmetric Aspherics nevertheless offers the possibility to measure single meridians in a one-step measurement. An extension to the complete surface can be obtained by rotating the aspheric around its vortex within the frame of the test interferometer.
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design considerations for the absolute testing approach of Aspherics using combined diffractive optical elements
Applied Optics, 2007Co-Authors: Gufran S Khan, Klaus Mantel, Irina Harder, Norbert Lindlein, Johannes SchwiderAbstract:Aspheric optical surfaces are often tested using diffractive optics as null elements. For precise measurements, the errors caused by the diffractive optical element must be calibrated. Recently, we reported first experimental results of a three position quasi-absolute test for rotationally invariant Aspherics by using combined-diffractive optical elements (combo-DOEs). Here we investigate the effects of the DOE substrate errors on the proposed calibration procedure and present a set of criteria for designing an optimized combo-DOE. It is demonstrated that this optimized design enhances the overall consistency of the procedure. Furthermore, the rotationally varying part of the surface deviations is compared with the rotationally varying deviations obtained by an N-position averaging procedure and is found to be in good agreement.
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dual wave front computer generated holograms for quasi absolute testing of Aspherics
Applied Optics, 2002Co-Authors: Mathias Beyerlein, Norbert Lindlein, Johannes SchwiderAbstract:Testing of Aspherics by means of computer-generated holograms (CGHs) is well known. To perform a quasi-absolute test of rotationally symmetric aspheric surfaces, two wave fronts must be encoded in the CGH. Both the null lens and a spherical lens have to be stored. This enables successive measurements of the aspheric and of a cat's-eye position without changing the object arm of the interferometer. Two possibilities for encoding both wave fronts have been investigated. A first-order approximation for estimating the influence of disturbing diffraction orders is given.
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Aspherical surface testing by using spherical compensation
18th Congress of the International Commission for Optics, 1999Co-Authors: Johannes Pfund, Norbert Lindlein, Johannes SchwiderAbstract:Abstract A technique for testing aspherical surfaces without the use of a null-corrector is described. The wave-front sensor for thedetection of the aspherical wave-front is a Shack-Hartmann sensor which has a significantly expanded range of measurablewave-front slopes. The optical testing set-up, the used algorithm for the dynamic range expansion, and experimentalresults are presented in this paper.Aspheric testing is commonly carried out by using a so-called null-corrector in the measuring arm of the test set-up. For general Aspherics a computer generated hologram is the best choice for a null-corrector but this approach is very expensive. Alternatively, we try to measure the deviations of an aspheric from the CAD-data in the presence of a rather bigaberration. The big aberrations are the result of the incomplete compensation provided by a spherical compensatorcommonly used in spherical testing (Fig. 1).telescope virtual image ofAsphericsphericalcondenserFig. 1 : Optical set-up for testing aspherical surfaces with spherical compensationThe main advantage of this set-up is that it can be used for different aspherical surfaces. The main drawback of thisapproach is the necessity to measure small deviations of the aspheric from ideal in the presence of a rather big aberration
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Interferometric tests for Aspherics
Fabrication and Testing of Aspheres, 1999Co-Authors: Johannes SchwiderAbstract:Interferometric tests of Aspherics are discussed under three main aspects: (1) the reduction of the sensitivity to measure even steep Aspherics, (2) the extended use of diffractive optical elements as phase conjugate members within the interferometer, and (3) the calibration issue which is especially involved with Aspherics. In addition rod-type Aspherics are included in our discussion because cylindrical and toroidal surfaces become more and more important.
Gerd Leuchs - One of the best experts on this subject based on the ideXlab platform.
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interferometric quasi absolute tests for Aspherics using a radial shear position
Optics Letters, 2009Co-Authors: Klaus Mantel, Eduard Geist, Irina Harder, Norbert Lindlein, Gerd LeuchsAbstract:Increasing accuracy requirements in aspheric metrology make the development of absolute testing procedures for aspheric surfaces important. One strategy is transferring the standard practice three-position test for spheres to Aspherics. The three-position test, however, involves a cat's eye position and therefore has certain drawbacks. We propose an absolute testing method for rotationally symmetric Aspherics where the cat's eye position is replaced with a radially sheared position. Together with rotational movements of the specimen, the surface deviations can be obtained in an absolute manner. To demonstrate the validity of the procedure, we present a measurement result for a sphere and compare it with a result obtained by the standard three-position test.
