Deflectometric measurement of large mirrors
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Evelyn Olesch
Evelyn Olesch is working as a PhD student at the University of Erlangen-Nuremberg, Institute of Optics, Information and Photonics in the group of Prof. Häusler. She got her diploma degree in mathematics in 2008 from the University of Erlangen-Nuremberg. Her diploma thesis was about surface reconstruction from 2D gradient data. Her current fields of research are deflectometry, calibration, and simulation.
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Gerd Häusler
Gerd Haeusler, 1970 Diplom-Physicist, 1974 PhD at Optics Institute, TU Berlin. Since 1974 University of Erlangen, Institute for Optics, Information and Photonics. 1987 professor at Erlangen. Postdoc, visiting professorships: ENST-Paris, IBM-Sindelfingen, Paul-Scherrer Institute Zurich, University of Munich, Riken Institute Tokyo. 1981 ‘Rudolf Kingslake Award’ of the SPIE, (with G. Ferrano). 1996–2010 member executive board of ‘German Society for Applied Optics’. 2012 Fellow of EOS. 2001 Foundation of ‘3D-Shape GmbH, Erlangen’. 3D-Shape is developing and marketing optical 3D-sensors. Field of research: physical and information theoretical limits of optical information acquisition. Around 240 papers, patents for Fourier Domain OCT (Spectral Radar), WLI (Coherence Radar), deflectometry (PMD), single-shot 3D-camera (Flying Triangulation).
André Wörnlein is working as a PhD student at the University of Erlangen-Nuremberg, Erlangen Centre of Astroparticle Physics (ECAP), in the group of Prof. van Eldik. He got his diploma degree in physics in 2012 from the University of Erlangen-Nuremberg. His diploma thesis was about Methods to measure optical properties of mirror facets for CTA.
Friedrich Stinzing is working as scientist at ECAP, Erlangen Centre of Astroparticle Physics at the University of Erlangen-Nuremberg since 1991. He received his PhD studying the hyperon-antihyperon production in proton-antiproton collisions. He worked for many years in high energy particle physic experiments at CERN and DESY focussing on detector development, simulation studies and analyses of subatomic particle properties. In 2009 he changed his working field to astro particle physics and contributes to the instrumentation of the H.E.S.S and CTA gamma-ray experiments.
Christopher van Eldik received his PhD from Dortmund University in 2004, where he worked on the production of vector mesons in proton-nucleus collisions. After a short postdoc at DESY (Hamburg, Germany) he changed fields from particle physics to gamma-ray astronomy and became senior postdoc in the group of Werner Hofmann at Max-Planck-Institute for Nuclear Physics (Heidelberg, Germany). In 2011 he was appointed Professor of Physics (experimental Astroparticle Physics) at University of Erlangen-Nuremberg. Van Eldik is member of the H.E.S.S. Collaboration and the CTA Consortium and is leading the Analysis and Reconstruction Working Group of the H.E.S.S. Instrument. Besides the development of instrumentation and analysis techniques for gamma-ray telescopes, his scientific focus is on the astrophysics of the Galactic center and on the detection of dark matter with gamma-ray instruments.
Abstract
We discuss the inspection of large-sized, spherical mirror tiles by ‘Phase Measuring Deflectometry’ (PMD). About 10 000 of such mirror tiles, each satisfying strict requirements regarding the spatial extent of the point-spread-function (PSF), are planned to be installed on the Cherenkov Telescope Array (CTA), a future ground-based instrument to observe the sky in very high energy gamma-rays. Owing to their large radii of curvature of up to 60 m, a direct PSF measurement of these mirrors with concentric geometry requires large space. We present a PMD sensor with a footprint of only 5×2×1.2 m3 that overcomes this limitation. The sensor intrinsically acquires the surface slope; the shape data are calculated by integration. In this way, the PSF can be calculated for real case scenarios, e.g., when the light source is close to infinity and off-axis. The major challenge is the calibration of the PMD sensor, specifically because the PSF data have to be reconstructed from different camera views. The calibration of the setup is described, and measurements presented and compared to results obtained with the direct approach.
About the authors
Evelyn Olesch is working as a PhD student at the University of Erlangen-Nuremberg, Institute of Optics, Information and Photonics in the group of Prof. Häusler. She got her diploma degree in mathematics in 2008 from the University of Erlangen-Nuremberg. Her diploma thesis was about surface reconstruction from 2D gradient data. Her current fields of research are deflectometry, calibration, and simulation.
Gerd Haeusler, 1970 Diplom-Physicist, 1974 PhD at Optics Institute, TU Berlin. Since 1974 University of Erlangen, Institute for Optics, Information and Photonics. 1987 professor at Erlangen. Postdoc, visiting professorships: ENST-Paris, IBM-Sindelfingen, Paul-Scherrer Institute Zurich, University of Munich, Riken Institute Tokyo. 1981 ‘Rudolf Kingslake Award’ of the SPIE, (with G. Ferrano). 1996–2010 member executive board of ‘German Society for Applied Optics’. 2012 Fellow of EOS. 2001 Foundation of ‘3D-Shape GmbH, Erlangen’. 3D-Shape is developing and marketing optical 3D-sensors. Field of research: physical and information theoretical limits of optical information acquisition. Around 240 papers, patents for Fourier Domain OCT (Spectral Radar), WLI (Coherence Radar), deflectometry (PMD), single-shot 3D-camera (Flying Triangulation).
André Wörnlein is working as a PhD student at the University of Erlangen-Nuremberg, Erlangen Centre of Astroparticle Physics (ECAP), in the group of Prof. van Eldik. He got his diploma degree in physics in 2012 from the University of Erlangen-Nuremberg. His diploma thesis was about Methods to measure optical properties of mirror facets for CTA.
Friedrich Stinzing is working as scientist at ECAP, Erlangen Centre of Astroparticle Physics at the University of Erlangen-Nuremberg since 1991. He received his PhD studying the hyperon-antihyperon production in proton-antiproton collisions. He worked for many years in high energy particle physic experiments at CERN and DESY focussing on detector development, simulation studies and analyses of subatomic particle properties. In 2009 he changed his working field to astro particle physics and contributes to the instrumentation of the H.E.S.S and CTA gamma-ray experiments.
Christopher van Eldik received his PhD from Dortmund University in 2004, where he worked on the production of vector mesons in proton-nucleus collisions. After a short postdoc at DESY (Hamburg, Germany) he changed fields from particle physics to gamma-ray astronomy and became senior postdoc in the group of Werner Hofmann at Max-Planck-Institute for Nuclear Physics (Heidelberg, Germany). In 2011 he was appointed Professor of Physics (experimental Astroparticle Physics) at University of Erlangen-Nuremberg. Van Eldik is member of the H.E.S.S. Collaboration and the CTA Consortium and is leading the Analysis and Reconstruction Working Group of the H.E.S.S. Instrument. Besides the development of instrumentation and analysis techniques for gamma-ray telescopes, his scientific focus is on the astrophysics of the Galactic center and on the detection of dark matter with gamma-ray instruments.
Acknowledgments
The authors would like to thank the Bayerische Forschungsstiftung (Az 748/07) and the Deutsche Forschungsgemeinschaft (Az Ha 1319/11) for the funding of the Phase Measuring Deflectometry research. We want to thank as well our former colleague Roman Krobot for the design and the installation of the SWD PMD.The authors would like to thank the CTA consortium, particularly our colleagues from CEA Saclay (France), INAF Brera (Italy), ICRR Tokyo (Japan) and MPIK Heidelberg (Germany), for providing mirror samples. This work was partially supported by the German Ministry of Education and Research under grant identifier 05A11WE2.
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©2014 THOSS Media & De Gruyter Berlin/Boston
Articles in the same Issue
- Frontmatter
- Community
- News from the European Optical Society
- Conference Notes
- Conference Calendar
- Topical Issue: Optics for Astronomy / Guest Editors: Jan Burke, Andrew Rakich and Jim Burge
- Editorial
- Optics for astronomy – Editorial
- Review Articles
- Active optics with a minimum number of actuators
- Highly sensitive telescope designs for higher contrast observations
- Replicated spectrographs in astronomy
- Ultra-smooth finishing of aspheric surfaces using CAST technology
- Hydroxide catalysis bonding for astronomical instruments
- Research Articles
- Fabrication and metrology of lithium niobate narrowband optical filters for the solar orbiter
- A method for the use of ellipticities and spot diameters for the measurement of aberrations in wide-field telescopes
- Deflectometric measurement of large mirrors
- The Four-Laser Guide Star Facility: Design considerations and system implementation
Articles in the same Issue
- Frontmatter
- Community
- News from the European Optical Society
- Conference Notes
- Conference Calendar
- Topical Issue: Optics for Astronomy / Guest Editors: Jan Burke, Andrew Rakich and Jim Burge
- Editorial
- Optics for astronomy – Editorial
- Review Articles
- Active optics with a minimum number of actuators
- Highly sensitive telescope designs for higher contrast observations
- Replicated spectrographs in astronomy
- Ultra-smooth finishing of aspheric surfaces using CAST technology
- Hydroxide catalysis bonding for astronomical instruments
- Research Articles
- Fabrication and metrology of lithium niobate narrowband optical filters for the solar orbiter
- A method for the use of ellipticities and spot diameters for the measurement of aberrations in wide-field telescopes
- Deflectometric measurement of large mirrors
- The Four-Laser Guide Star Facility: Design considerations and system implementation
