References of "Doyle, Dominic"
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See detailLong-wave infrared digital holographic interferometry with diffuser or point source illuminations for measuring deformations of aspheric mirrors
Vandenrijt, Jean-François ULg; Thizy, Cédric ULg; Queeckers, Patrick et al

in Optical Engineering : The Journal of the Society of Photo-Optical Instrumentation Engineers (2014), 53(11), 112309

Long-wave infrared digital holographic interferometry with CO2 laser and microbolometer arrays has been developed for testing the large deformations of space reflectors. The setup considered is a ... [more ▼]

Long-wave infrared digital holographic interferometry with CO2 laser and microbolometer arrays has been developed for testing the large deformations of space reflectors. The setup considered is a Mach–Zehnder, associated to the digital holography reconstruction of the wavefront in the inline configuration with phase shifting. Two possibilities exist for illuminating the tested reflector: either with a point source (similarly to classical interferometry) or an extended source (with a diffuser). This paper presents the development of a modular setup which allows comparing both in the case of a parabolic mirror [less ▲]

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See detailDigital Holographic Interferometry in the Long-Wave Infrared for the Testing of Large Aspheric Space Reflectors
Vandenrijt, Jean-François ULg; Thizy, Cédric ULg; Stockman, Yvan ULg et al

in Osten, Wolfgang (Ed.) Fringe 2013 (2014)

Digital holographic (DH) interferometry has been developed in the long-wave infrared spectral range with CO2 lasers and microbolometer arrays. This application has been driven by the European Space ... [more ▼]

Digital holographic (DH) interferometry has been developed in the long-wave infrared spectral range with CO2 lasers and microbolometer arrays. This application has been driven by the European Space Agency’s constant need of techniques for monitoring large displacements of large structures. Here the study focuses on the case of aspheric mirrors, like parabola and ellipses. Usually they are tested through interferometric wavefront error measurements which require expensive null-lenses matching each of the reflectors considered. In the case of monitoring deformation a holographic technique can be considered where the wavefront is compared with itself at different instant. Therefore the optical can be quite simple and easily reconfigurable from one reflector to another. The advantage of using long wavelength is that large deformations can be measured at once, in addition to being more immune against environmental perturbations. Another advantage of DH at such wavelengths is that the ratio between the wavelength and the pixel size allows reconstructing objects 5 to 10 times larger than with DH in the visible. In this project we considered first the case of a 1.1 meter diameter parabola for submillimeter range observations. Such specimen shows strong specular reflectivity. We have developed several set-ups with different ways to illuminate the object and to collect rays to form the object beam: either through point source or through and extended diffuser working by reflection of the laser beam. Both possibilities have been compared in terms of fringe quality as well as measurement range. We selected the diffuser illumination for applying the set-up into a large vacuum facility for measuring the deformation of the parabola between 224 and 107 K. Results of this measurement campaign are presented. A further application has been shown by observation of off-axis ellipse. In this case interferometric testing is difficult to achieve and LWIR DHI with diffuser illumination is found quite simple to implement and gives straightforward results. [less ▲]

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See detailDigital Holographic Interferometry with CO2 Lasers Applied to Aspheric Space Reflectors Testing
Georges, Marc ULg; Vandenrijt, Jean-François ULg; Thizy, Cédric ULg et al

in Digital Holography and Three-Dimensional Imaging, OSA Technical Digest (online) (2013, May)

Digital holographic interferometry at long infrared wavelengths allows monitoring large deformations of space reflectors during vacuum-thermal testing. We present different optical schemes and an ... [more ▼]

Digital holographic interferometry at long infrared wavelengths allows monitoring large deformations of space reflectors during vacuum-thermal testing. We present different optical schemes and an application to the complex case of elliptic reflector. [less ▲]

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See detailDigital holographic interferometry with CO2 lasers and diffuse illumination applied to large space reflectors metrology
Georges, Marc ULg; Vandenrijt, Jean-François ULg; Thizy, Cédric ULg et al

in Applied Optics (2013), 52(1), 102-116

Digital holographic interferometry in the long wave infrared domain has been developed by combining a CO2 laser and a microbolometer array. The long wavelength allows large deformation measurements which ... [more ▼]

Digital holographic interferometry in the long wave infrared domain has been developed by combining a CO2 laser and a microbolometer array. The long wavelength allows large deformation measurements which are of interest in the case of large space reflectors undergoing thermal changes when in orbit. We review holography at such wavelengths and present some specific aspects related to this spectral range on our measurements. For the design of our digital holographic interferometer we studied the possibility of illuminating specular objects by a reflective diffuser. We discuss the development of the interferometer and the results obtained on a representative space reflector, first in the laboratory and then during vacuum cryogenic test. [less ▲]

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See detailLong-wave infrared digital holography for the qualification of large space reflectors
Vandenrijt, Jean-François ULg; Thizy, Cédric ULg; Georges, Marc ULg et al

Conference (2012, October 09)

Deformation metrology of complex and large space reflectors is a recurrent problem addressed by ESA. The challenging tasks of on-ground qualification and verification testing are to achieve the required ... [more ▼]

Deformation metrology of complex and large space reflectors is a recurrent problem addressed by ESA. The challenging tasks of on-ground qualification and verification testing are to achieve the required accuracy in the measurement of these reflectors deformation and to verify their performance under simulated space conditions (vacuum, low temperature). A long-wave infrared digital holographic interferometer for the verification and validation of this type of reflector in a space environment is presented. It has been developed to fill the gap between holography/interferometry techniques in the visible wavelengths and methods based on structured light illumination like videogrammetry, stereocorrelation, and fringe/pattern projection. The former provide a good measurement uncertainty but the displacements are often too large to be measured and they require a very stable environment, while the latter provide large measurement range but with higher measurement uncertainty. The new instrument is based on digital holography and uses a CO2 lasers emitting at 10.6 µm combined with a commercial thermographic camera. A diffuser is illuminated by the laser beam, producing a speckle wavefront which is observed after reflection on the reflector surface. This reflected speckle wavefront behaves exactly as if the reflector was a diffusive surface, producing its own speckle, allowing the measurement of its deformation. The advantage of this configuration compared to a classical interferometer working at 10.6 µm, is that it requires no specific optics such as a null lens (in the case of parabola) or expensive illumination/collection optics (in the case of ellipse). The metrological certification of the system was performed in the laboratory by measuring the tilts of a 1.1 meter diameter parabolic reflector. The displacements are measured in parallel with a Doppler effect interferometer and the measurement uncertainty is estimated. The application of the new interferometer to the measurement of an elliptic reflector is also presented. The technique has been certified during a thermal-vacuum test. The deformation of the parabolic reflector is measured for a temperature variation from 288 K down to 113 K. The results are compared to previous results obtained on the same reflector with a high spatial resolution infrared interferometer, also developed at CSL. [less ▲]

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See detailDigital Holographic Interferometry and ESPI at Long Infrared Wavelengths with CO2 Laser (invited paper)
Georges, Marc ULg; Vandenrijt, Jean-François ULg; Thizy, Cédric ULg et al

in Digital Holography and 3D Imaging (DH2012) (2012, April 28)

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See detailDevelopment of digital holography in the long wave infrared range for assessment of space reflectors
Thizy, Cédric ULg; Vandenrijt, Jean-François ULg; Georges, Marc ULg et al

in Proceedings of ICSO 2010 - International Conference on Space Optics (2010, October)

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See detailDisplacement measurements of a parabolic reflector by holographic interferometry in the long-wavelength infrared
Vandenrijt, Jean-François ULg; Georges, Marc ULg; Thizy, Cédric ULg et al

in International Astronautical Congress 2010 (2010, September)

Deformation metrology of complex shape space structure and reflectors is a recurrent problem addressed by ESA. Consequently, suitable measurement techniques have to be developed and validated to support ... [more ▼]

Deformation metrology of complex shape space structure and reflectors is a recurrent problem addressed by ESA. Consequently, suitable measurement techniques have to be developed and validated to support relevant on-ground qualification and verification testing. Holographic techniques in the visible wavelengths are common for measuring the surface displacement of object. However the short wavelength induces high stability criteria which are so severe that they often prevent the measurement of large space structures under good conditions. We propose to use a wavelength longer than the usual visible ones to render such holographic displacement measurement techniques less sensitive to external perturbations. For this we consider CO2 laser emitting at 10.6 μm which correspond to the long-wavelength infrared (LWIR) spectrum. The most important element for performing holography is to use an adequate recording medium. However no convincing holographic recording media exists in LWIR and we decided to investigate the possibility of electronic hologram recording, such as electronic speckle pattern interferometry (ESPI). This possibility is feasible nowadays thanks to various thermal imaging technologies such has uncooled microbolometers sensors commonly found in thermographic cameras. In this study, we analyse how it is possible to measure surface displacements of specular objects, which do not produce speckle, using speckle interferometry by the mean of a scattering diffuser. We then apply the ESPI technique at LWIR for measuring displacements of a large parabolic reflector. [less ▲]

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See detailPlanck pre-launch status: The Planck mission
Tauber, Jan; Banos, Thierry; Roose, Stéphane ULg et al

in Astronomy and Astrophysics (2010), 520

The European Space Agency’s Planck satellite, launched on 14 May 2009, is the third-generation space experiment in the field of cosmic microwave background (CMB) research. It will image the anisotropies ... [more ▼]

The European Space Agency’s Planck satellite, launched on 14 May 2009, is the third-generation space experiment in the field of cosmic microwave background (CMB) research. It will image the anisotropies of the CMB over the whole sky, with unprecedented sensitivity ( ΔT T ∼ 2 × 10−6) and angular resolution (∼5 arcmin). Planck will provide a major source of information relevant to many fundamental cosmological problems and will test current theories of the early evolution of the Universe and the origin of structure. It will also address a wide range of areas of astrophysical research related to the Milky Way as well as external galaxies and clusters of galaxies. The ability of Planck to measure polarization across a wide frequency range (30−350 GHz), with high precision and accuracy, and over the whole sky, will provide unique insight, not only into specific cosmological questions, but also into the properties of the interstellar medium. This paper is part of a series which describes the technical capabilities of the Planck scientific payload. It is based on the knowledge gathered during the on-ground calibration campaigns of the major subsystems, principally its telescope and its two scientific instruments, and of tests at fully integrated satellite level. It represents the best estimate before launch of the technical performance that the satellite and its payload will achieve in flight. In this paper, we summarise the main elements of the payload performance, which is described in detail in the accompanying papers. In addition, we describe the satellite performance elements which are most relevant for science, and provide an overview of the plans for scientific operations and data analysis. [less ▲]

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See detailQualification de grands réflecteurs en environnement spatial
Thizy, Cédric ULg; Stockman, Yvan ULg; Doyle, Dominic et al

in Smigielski, P. (Ed.) Actes du Cinquième colloque francophone Méthodes et Techniques Optiques pour l'Industrie (2004, November)

Les nouvelles générations de télescopes spatiaux dans le domaine infrarouge nécessitent des réflecteurs de grandes dimensions et de haute qualité. Ceux-ci, pour des raisons de poids, sont basés sur les ... [more ▼]

Les nouvelles générations de télescopes spatiaux dans le domaine infrarouge nécessitent des réflecteurs de grandes dimensions et de haute qualité. Ceux-ci, pour des raisons de poids, sont basés sur les technologies des matériaux composites dont les comportements aux basses températures sont mal connus. Une méthode par interférométrie holographique de vérification et de validation en environnement spatial de ce type de réflecteurs est présentée. Elle est basée sur l'utilisation d'une caméra holographique dynamique observant un dépoli sur lequel est projeté le faisceau objet venant de la surface réfléchissante. Outre une augmentation de la dynamique de mesure, cette méthode offre l’avantage principal, par rapport aux techniques d’interférométrie optique, de ne pas nécessiter de système optique d’adaptation du front d’onde au réflecteur à mesurer et donc un gain de flexibilité majeur pour des formes exotiques de réflecteurs (types asphériques). Le système de mesure a été calibré avec un interféromètre ponctuel à effet Doppler. L'influence des différentes sources d’erreur du système sur la mesure a été évaluée. Cette évaluation a porté principalement sur des aspects vibratoires et thermiques. Ces réflecteurs devant être testés sous vide et à basses températures, le système de mesure a été rendu compatible à ces conditions. Des éléments de la caméra holographique (objectifs, CCD, cristal, fibre optique) ont été adaptés et testés sous vide. La certification métrologique de l’ensemble du système sera réalisée par la mesure d'une antenne parabolique, de 1.1 m de diamètre de comportement connu et placée dans un environnement spatial simulé. Le test consistera à mesurer les déplacements et déformations de l'antenne entre un état initial à la température ambiante, et un état final à une température d'environ 130K. [less ▲]

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See detailDevelopment of optical ground verification method for mu m to sub-mm reflectors
Stockman, Yvan ULg; Thizy, Cédric ULg; Lemaire, Philippe ULg et al

in Warmbein, B. (Ed.) Proceedings of the 5th International Conference on Space Optics (ICSO) (2004, April 02)

Large reflectors and antennas for the IR to mm wavelength range are being planned for many Earth observation and astronomical space missions and for commercial communication satellites as well. The ... [more ▼]

Large reflectors and antennas for the IR to mm wavelength range are being planned for many Earth observation and astronomical space missions and for commercial communication satellites as well. The challenging tasks of on-ground testing are to achieve the required accuracy in the measurement of the reflector shapes and antenna structures and to verify their performance under simulated space conditions (vacuum, low temperatures). A small number of infrared interferometers have been commercially developed over the last 10 years but their applications have also been limited due to poor dynamic range and the restricted spatial resolution of their detectors. It has therefore been considered essential, from the viewpoint of supporting future ESA exploration missions, to develop and realise suitable verification tools based on infrared interferometry and other optical techniques for testing large reflector structures, telescope configurations and their performances under simulated space conditions. Two methods and techniques are developed at CSL. The first one is an IR-phase shifting interferometer with high spatial resolution. This interferometer shall be used specifically for the verification of high precision IR, FIR and sub-mm reflector surfaces and telescopes under both ambient and thermal vacuum conditions. The second one presented hereafter is a holographic method for relative shape measurement. The holographic solution proposed makes use of a home built vacuum compatible holographic camera that allows displacement measurements from typically 20 nanometres to 25 microns in one shot. An iterative process allows the measurement of a total of up to several mm of deformation. Uniquely the system is designed to measure both specular and diffuse surfaces [less ▲]

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See detailCanister free videogrammetry system for thermal vacuum and space applications
Roose, Stéphane ULg; Stockman, Yvan ULg; Bolsee, Jean-Christophe et al

in Decker, J.; Brown, N. (Eds.) Proceedings of the Conference on Recent Developments in Traceable Dimensional Measurements, (2003, November 20)

The development of a canister-free videogrammetry system is presented. Applications in view, are coordinate measurements during thermal vacuum test and on-baord space flight metrology of mechanical ... [more ▼]

The development of a canister-free videogrammetry system is presented. Applications in view, are coordinate measurements during thermal vacuum test and on-baord space flight metrology of mechanical structures, reflectors and antenna's. The paper presents the breadboard system architecture. Two breadboards have been developed. One is based on a space-qualified micro-imager camera. Lenses and flashers are all commercial components and have been made vacuum compatible. Results of accuracy (typically 50ppm) and resolution (typically 25 ppm) tests, in ambient and in vacuum are also presented. [less ▲]

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