References of "Languy, Fabian"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailDetermination of vibration amplitudes from binary phase patterns obtained by phase-shifting time-averaged speckle shearing interferometry
Kirkove, Murielle ULiege; Guérit, Stéphanie; Jacques, Laurent et al

in Applied Optics (2018), 57(27), 8065-8077

Speckle shearing interferometry (shearography) is a full-field strain measurement technique that can be used in vibration analysis. In our case, we apply a method that combines the time-averaging and ... [more ▼]

Speckle shearing interferometry (shearography) is a full-field strain measurement technique that can be used in vibration analysis. In our case, we apply a method that combines the time-averaging and phase-shifting tech- niques. It produces binary phase patterns, where the phase changes are related to the zeroes of a Bessel J 0 function, typical of time-averaging. However, the contrast and resolution are better compared to traditional time-averaging. In a previous paper, we have shown that this is particularly useful in vibration testing performed under industrial conditions, because fringe patterns are noisier than in quiet laboratory environments. This paper goes a step further in proposing a processing method for estimating the vibration amplitude, for helping non-experts to identify vibration modes. Since shearography measures the spatial derivative of displacement, spatial integration is required. Prior to that, different processes like denoising, binarization, automated nodal line detection, and amplitude assignment are applied. We analyze the performance of the method on synthetic and experimental data, in the function of noise level and fringes density. Results on data acquired in an industrial environment illustrate the good performances of the proposed method. [less ▲]

Detailed reference viewed: 34 (10 ULiège)
Full Text
See detailProcessing of binary fringe patterns obtained by phase-shifting time-averaged shearography on vibrating objects
Kirkove, Murielle ULiege; Guérit, Stéphanie; Jacques, Laurent et al

in Jaroszewicz, L. R. (Ed.) Proceedings of SPIE volume 10834, 7th International Conference on Speckle Metrology, Speckle 2018 (2018, September 07)

Shearography can be used for full-field strain measurements in the field of vibration analysis. It provides the spatial derivative of the optical phase difference of the vibration modes amplitude along ... [more ▼]

Shearography can be used for full-field strain measurements in the field of vibration analysis. It provides the spatial derivative of the optical phase difference of the vibration modes amplitude along the so-called shear direction. The shearographic setup considered here is based on the phase-shifting time-averaged technique. It can easily be applied experimentally, but its drawback is that binary phase patterns are obtained. These phase changes are related to the zeroes of a Bessel function. Retrieving the corresponding displacement maps is not straightforward. Moreover, integration of shearographic results need to be performed, and this step is sensitive to noise in the patterns. In this paper, different processing stages are described, from fringe denoising to integration of the displacement maps. The application on data acquired in industrial environment illustrates the good performances of the proposed method. [less ▲]

Detailed reference viewed: 38 (14 ULiège)
Full Text
Peer Reviewed
See detailSpace mirror deformation: from thermo- mechanical measurements by speckle interferometry to optical comparison with multiphysics simulation
Languy, Fabian ULiege; Vandenrijt, Jean-François ULiege; Saint-Georges, Philippe et al

in Applied Optics (2018), 57(24), 6982

Experimental testing of space optics is a mandatory process for investigating the optical performances in conditions close to reality. With the optical requirement level increasing over years, these ... [more ▼]

Experimental testing of space optics is a mandatory process for investigating the optical performances in conditions close to reality. With the optical requirement level increasing over years, these experimental tests are increasingly expensive and time-consuming. A modeling tool would therefore be an elegant solution to avoid these drawbacks. For this purpose, a multiphysics approach has been used to predict how optics behave under thermal loads. In this paper, experimental surface deformations of a space mirror perturbed by thermal gradients are compared to multiphysics simulation results. The local displacements of the mirror surface have been measured by use of electronic speckle pattern interferometry, and the deformation itself has been calculated by subtracting the rigid body motion. After validation of the thermo-mechanical solution, experimental and numerical wavefront errors are compared. [less ▲]

Detailed reference viewed: 41 (13 ULiège)
Full Text
See detailPreliminary design of SALTO, the Belgian adaptive optics demonstrator
Orban De Xivry, Gilles ULiege; Absil, Olivier ULiege; Lismont, Marjorie et al

in Close, Laird; Schreiber, Laura; Schmidt, Dirk (Eds.) Adaptive Optics System VI (2018, July 11)

SALTO is a Belgian project aiming to build a complete 1 m telescope demonstrator including a single-conjugated adaptive optics (AO) system together with a Rayleigh laser guide star system. The underlying ... [more ▼]

SALTO is a Belgian project aiming to build a complete 1 m telescope demonstrator including a single-conjugated adaptive optics (AO) system together with a Rayleigh laser guide star system. The underlying objective of SALTO consists in developing the Belgian expertise regarding AO systems for medium size telescopes (i.e. diameter from 1 to 4m), for application in astronomy, optical communication or detection of low-Earth orbit objects. The project approach is to base the design on COTS components, in order to reduce complexity, and to favor both robustness and automation of the system over performance. The SALTO demonstrator will be located at Redu Space Services in the Belgian countryside. Therefore the major challenge of the project will be to deal with poor seeing, far worst than astronomical standards, while preserving robust and reasonable correction in the red-visible and near-infrared wavelength range. Here, we present our system baseline, the expected performance, and the preliminary design of the AO system. We conclude with the current prospects for the project. [less ▲]

Detailed reference viewed: 39 (5 ULiège)
Full Text
Peer Reviewed
See detailDigital Holographic Interferometry in the Long-Wave Infrared Range for Measuring Large Deformations of Space Components under Thermal-Vacuum Testing
Vandenrijt, Jean-François ULiege; Thizy, Cédric ULiege; Languy, Fabian ULiege et al

in Proceedings (2018, July 09), 2018(2), 534

Holographic interferometry at around 10 µm wavelengths has many advantages. It offers the possibility of large deformation measurement, while being much less sensitive to external perturbations. We ... [more ▼]

Holographic interferometry at around 10 µm wavelengths has many advantages. It offers the possibility of large deformation measurement, while being much less sensitive to external perturbations. We present the state-of-the art of this technique applied to several industrial cases of the space industry. In particular, we demonstrate that the technique is well adapted to measurement of full-field deformation maps of space structures undergoing large temperature variations typical to what they experience in space conditions. [less ▲]

Detailed reference viewed: 41 (13 ULiège)
Full Text
Peer Reviewed
See detailLaser ultrasound flexible system for non-contact inspection of medium size and complex shaped composite structures made of carbon fiber reinforced polymer
Vandenrijt, Jean-François ULiege; Languy, Fabian ULiege; Thizy, Cédric ULiege et al

in Proceedings (2018, June 22), 2018(2), 455

We present the development of a contactless laser ultrasound system for nondestructive inspection of CFRP complex structures. Ultrasound are generated by a thermoelastic effect resulting from a green ... [more ▼]

We present the development of a contactless laser ultrasound system for nondestructive inspection of CFRP complex structures. Ultrasound are generated by a thermoelastic effect resulting from a green pulsed laser insulating a point of the inspected part. The resulting displacement of the surface point is probed by a two-wave mixing based interferometer working in the near infrared. The system is flexible and completely fiber-coupled. It is able to provide C-scans on complex shaped CFRP aeronautical structures. [less ▲]

Detailed reference viewed: 41 (19 ULiège)
Full Text
See detailDeformation measurements by ESPI of the surface of a heated mirror and comparison with numerical model
Languy, Fabian ULiege; Vandenrijt, Jean-François ULiege; Saint-Georges, Philippe et al

in Proceedings of SPIE: The International Society for Optical Engineering (2017, June 26), 103291M

The manufacture of mirrors for space application is expensive and the requirements on the optical performance increase over years. To achieve higher performance, larger mirrors are manufactured but the ... [more ▼]

The manufacture of mirrors for space application is expensive and the requirements on the optical performance increase over years. To achieve higher performance, larger mirrors are manufactured but the larger the mirror the higher the sensitivity to temperature variation and therefore the higher the degradation of optical performances. To avoid the use of an expensive thermal regulation, we need to develop tools able to predict how optics behaves with thermal constraints. This paper presents the comparison between experimental surface mirror deformation and theoretical results from a multiphysics model. The local displacements of the mirror surface have been measured with the use of electronic speckle pattern interferometry (ESPI) and the deformation itself has been calculated by subtracting the rigid body motion. After validation of the mechanical model, experimental and numerical wave front errors are compared. [less ▲]

Detailed reference viewed: 34 (10 ULiège)
Full Text
See detailNondestructive inspection of aerospace composites by a fiber-coupled laser ultrasonics system
Vandenrijt, Jean-François ULiege; Languy, Fabian ULiege; Thizy, Cédric ULiege et al

in Proceedings of SPIE: The International Society for Optical Engineering (2017, June)

Laser ultrasonics is a technique currently studied for nondestructive inspection of aerospace composite structures based on carbon fibers. It combines a pulsed laser impacting the surface generates an ... [more ▼]

Laser ultrasonics is a technique currently studied for nondestructive inspection of aerospace composite structures based on carbon fibers. It combines a pulsed laser impacting the surface generates an ultrasound inside the material, through the nondestructive thermoelastic effect. Second a detection interferometer probes the impacted point in order to measure the displacement of the surface resulting from the emitted ultrasound wave and the echo coming back from the different interfaces of the structure. Laser ultrasonics is of interest for inspecting complex shaped composites. We have studied the possibility of using frequency doubled YAG laser for the generation and which is fiber-coupled, together with a fiber-coupled interferometric probe using a YAG laser in the NIR. Our final system is a lightweight probe attached to a robot arm and which is able to scan complex shapes. The performances of the system are compared for different wavelengths of generations. Also we have studied some experimental parameters of interest such as tolerance to angle and focus distance, and different geometries of generation beams. We show some examples of inspection of reference parts with known defects. In particular C-scans of curved composites structures are presented. [less ▲]

Detailed reference viewed: 40 (10 ULiège)
Full Text
See detailArtificial defects in CFRP composite structure for Thermography and Shearography nondestructive inspection
Blain, Pascal ULiege; Vandenrijt, Jean-François ULiege; Languy, Fabian ULiege et al

in Proceedings of SPIE 10449, Fifth International Conference on Optical and Photonics Engineering (2017, April)

Locating defects in CFRP composite materials is a hot topic in nondestructive inspection (NDI). Beside classical NDI technique, such as ultrasound testing (UT), contactless techniques are actively studied ... [more ▼]

Locating defects in CFRP composite materials is a hot topic in nondestructive inspection (NDI). Beside classical NDI technique, such as ultrasound testing (UT), contactless techniques are actively studied. Generally manufacturers of CFRP structure incorporate artificial defects in the bulk, with different extents and depths, in order to study the performance of a specific NDI technique to detect the defect. One of the most common defects in CFRP is delamination between two layers. This is simulated by inserting teflon sheets which, like air, acts as ultrasound blocker in UT. When such reference part is used to assess NDI performance of thermography or shearography, we only observe respectively the thermal or mechanical response of teflon with respect to external loading used with these techniques. In this work, we assess other possibilities for artificial defects in CFRP matrix. For that a CFRP structure was developed and which incorporates teflon, flat-bottom holes and delamination obtained by the pull-out method. We experimentally studied the signals and we discuss the difference between the various artificial defects methods. [less ▲]

Detailed reference viewed: 58 (22 ULiège)
Full Text
See detailUltrasons par laser pour l'inspection de matériaux composites. Comparaison entre génération à 532 nm et 10,6 µm. Effet de la géométrie du faisceau de génération
Vandenrijt, Jean-François ULiege; Languy, Fabian ULiege; Walter, Julien et al

Conference (2017, March)

Un système de contrôle non destructif basé sur la génération d'ultrasons par laser à 532 nm et de détection par laser, entièrement fibré et robotisé, est développé au CSL. Nous le comparons à un système ... [more ▼]

Un système de contrôle non destructif basé sur la génération d'ultrasons par laser à 532 nm et de détection par laser, entièrement fibré et robotisé, est développé au CSL. Nous le comparons à un système équivalent du CTA basé sur la génération plus classique avec un laser CO2 (10,6 µm). De plus nous montrons les résultats d'investigations concernant différentes géométrie du faisceau de génération. [less ▲]

Detailed reference viewed: 39 (3 ULiège)
Full Text
See detailInterférométrie de speckle à 10.6 µm et shearographie à 532 nm en temps réel temps moyenné et décalage de phase. Comparaison et application pour identification des modes de vibrations sur shaker industriel
Vandenrijt, Jean-François ULiege; Languy, Fabian ULiege; Thizy, Cédric ULiege et al

Conference (2017, March)

Deux méthodes interférométriques sont comparées pour l'identification des modes de vibration en temps réel-temps moyenné avec décalage de phase. Il s'agit d'une part de l'interférométrie de speckle (ESPI ... [more ▼]

Deux méthodes interférométriques sont comparées pour l'identification des modes de vibration en temps réel-temps moyenné avec décalage de phase. Il s'agit d'une part de l'interférométrie de speckle (ESPI) à 10,6 μm et, d'autre part, de la shearographie à 532 nm. La comparaison sur une aube de vibration en laboratoire nous a conduit à sélectionner la shearographie en lumière visible pour l'application avec un shaker en milieu industriel, où les conditions de travail ne permettent pas d'utiliser des techniques interférométriques plus conventionnelles. [less ▲]

Detailed reference viewed: 26 (4 ULiège)
Full Text
See detailMeasurements by ESPI of surface deformations of a heated mirror and comparison with multiphysics simulations
Vandenrijt, Jean-François ULiege; Languy, Fabian ULiege; Saint-Georges, P. et al

in Proceedings of SPIE: The International Society for Optical Engineering (2017), 10562

Observations from space are almost exclusively performed by means of mirrors. To achieve higher performance, larger and larger mirrors are manufacture usually in aluminum alloy in order to be cost ... [more ▼]

Observations from space are almost exclusively performed by means of mirrors. To achieve higher performance, larger and larger mirrors are manufacture usually in aluminum alloy in order to be cost-effective. However from the optical performance point of view, the coefficient of thermal expansion (CTE) of aluminum is an important drawback. © 2017 SPIE. [less ▲]

Detailed reference viewed: 23 (4 ULiège)
Full Text
Peer Reviewed
See detailWaveguide solar concentrator design with spectrally separated light
Michel, Céline ULiege; Blain, Pascal ULiege; Clermont, Lionel ULiege et al

in Solar Energy (2017), 157

In this article, we propose a new solar concentrator based on spectral splitting of sunlight. Spectral splitting has the objective to collect different spectra onto spectrally adapted solar cells for a ... [more ▼]

In this article, we propose a new solar concentrator based on spectral splitting of sunlight. Spectral splitting has the objective to collect different spectra onto spectrally adapted solar cells for a more efficient use of the Sun’s spectrum. Its combination with solar concentration makes an alternative to classical technologies. The proposed concentrator is composed of a diffractive/refractive optical element that spectrally splits and focuses the light onto a waveguide. The light is then conducted by total internal reflection towards the two specific solar cells. The optical concept and optimization of each element is presented in this paper. An adaptation for dye sensitized solar cells is performed. A geometrical factor around 5× is reached. Finally, theoretical optical efficiency, the manufacturing process and experimental testing with a collimated Sun simulator are presented. [less ▲]

Detailed reference viewed: 70 (17 ULiège)
Full Text
See detailHolographie numérique en infrarouge lointain - Applications aérospatiales
Georges, Marc ULiege; Vandenrijt, Jean-François ULiege; Languy, Fabian ULiege et al

Conference (2016, November)

L'holographie numérique en infrarouge lointain, utilisant un laser CO2 émettant vers 10 µm et des caméras thermiques à microbolomètres, permet la mesure de grandes déformations et de s'affranchir des ... [more ▼]

L'holographie numérique en infrarouge lointain, utilisant un laser CO2 émettant vers 10 µm et des caméras thermiques à microbolomètres, permet la mesure de grandes déformations et de s'affranchir des perturbations environnementales plus facilement qu'en lumière visible. Nous l'appliquons dans le cas de structures spatiales subissant des cyclages thermiques en régime cryogénique sous vide, ce qui induit des déplacements de grande ampleur. Nous passerons en revue les différentes expériences effectuées au Centre Spatial de Liège et discuterons des recherches en cours, notamment pour utiliser des longueurs d'onde plus grande (ondes Terahertz) [less ▲]

Detailed reference viewed: 46 (6 ULiège)
Full Text
See detailLaser Ultrasound for NDT: investigation of the generation beam shape
Languy, Fabian ULiege; Perrard, Aurélie; Vandenrijt, Jean-François ULiege et al

Poster (2016, July)

Usually laser ultrasonic systems use an infrared laser operating at 10 µm to generate the ultrasound in CFRP objects. However this system suffer from an important drawback: optical fiber cannot be used to ... [more ▼]

Usually laser ultrasonic systems use an infrared laser operating at 10 µm to generate the ultrasound in CFRP objects. However this system suffer from an important drawback: optical fiber cannot be used to transport the high energy beam from the laser output to the target which limits the flexibility of the system to investigated complex shaped objects. To overcome this issue, visible light can be used to generate ultrasound. In our case we use a fiber-coupled laser operating at 532 nm. The output end of the optical fiber is placed on an industrial robot arm. The investigated object remains stationary while the optical fiber mounted on the robot arm scan the object. This system offers large flexibility but laser generation at 532 nm is known to be less efficient than CO 2 system emitting at 10 µm. Increasing the visible pulse power is one of the options but optics and CRFF object will be damaged before the same echo level as CO2 generation can be obtained. An alternative solution consists in the investigation of the generation beam size and shape. We recently developed an optical design composed of an axicon lens able to generate annular beam. The diameter of the beam can be adapted. If the axicon lens is removed the optical system provides a disk whose diameter can also be adapted onto the investigated object. Ray-traycing simulations performed with ASAP and experimental beam profile investigated with a beam profiler show good agreement between theoretical and experimental optical design. An experimental comparison between ring and disk shapes will be presented. The comparisons take into account the beam diameter and the beam intensity but also the effect of the angle of incidence will be presented. [less ▲]

Detailed reference viewed: 89 (7 ULiège)
Full Text
Peer Reviewed
See detailVibration mode shapes visualization in industrial environment by real-time time-averaged phase-stepped electronic speckle pattern interferometry at 10.6  μm and shearography at 532 nm
Languy, Fabian ULiege; Vandenrijt, Jean-François ULiege; Thizy, Cédric ULiege et al

in Optical Engineering: the Journal of the Society of Photo-Optical Instrumentation Engineers (2016), 55(12), 121704

We present our investigations on two interferometric methods suitable for industrial conditions dedicated to the visualization of vibration modes of aeronautic blades. First, we consider long-wave ... [more ▼]

We present our investigations on two interferometric methods suitable for industrial conditions dedicated to the visualization of vibration modes of aeronautic blades. First, we consider long-wave infrared (LWIR) electronic speckle pattern interferometry (ESPI). The use of long wavelength allows measuring larger amplitudes of vibrations compared with what can be achieved with visible light. Also longer wavelengths allow lower sensitivity to external perturbations. Second, shearography at 532 nm is used as an alternative to LWIR ESPI. Both methods are used in time-averaged mode with the use of phase-stepping. This allows transforming Bessel fringes, typical to time averaging, into phase values that provide higher contrast and improve the visualization of vibration mode shapes. Laboratory experimental results with both techniques allowed comparison of techniques, leading to selection of shearography. Finally a vibration test on electrodynamic shaker is performed in an industrial environment and mode shapes are obtained with good quality by shearography. [less ▲]

Detailed reference viewed: 42 (14 ULiège)
Full Text
See detailMesures de déformation par ESPI de la surface d’un miroir chauffé et comparaison avec simulations numériques
Languy, Fabian ULiege; Vandenrijt, Jean-François ULiege; Saint-Georges, Philippe et al

Conference (2015, November)

Detailed reference viewed: 22 (6 ULiège)
Full Text
See detailInvestigation of spectral impacts on the performance of a concentration device using a Fresnel lens combined with a double junction cell
Loicq, Jerôme ULiege; Galante, Nicolas ULiege; Thibert, Tanguy ULiege et al

in Proceedings of SPIE: The International Society for Optical Engineering (2014, May 15)

This experimental study was carried out within the context of high concentration photovoltaics. The paper presents the results of an experimental investigation relating to the quantification of the ... [more ▼]

This experimental study was carried out within the context of high concentration photovoltaics. The paper presents the results of an experimental investigation relating to the quantification of the impacts of the chromatic effect on the performance of a double junction GaInP/GaAs solar cell. Chromatic effects are the result of material dispersion caused by the refractive optics component. This study aims to evaluate the effect of the spectral modification of the incident beam on the whole solar concentrator system performance. Such considerations are fundamental in producing a highly accurate design, with which to achieve the best possible system performance. Efficiency is evaluated within the vicinity of the focus of a Fresnel lens designed for concentration. On the optical axis, rays with different wavelengths are not focalized at the same points. The spectral content of the beam depends, therefore, upon the position of the cell along the optical axis. It is assumed that spectral content modification may have an impact on cell performance and, as a consequence, on system efficiency as a whole. Efficiency of the optical Fresnel lens and of the cell were evaluated in relation to spectral content modification. [less ▲]

Detailed reference viewed: 56 (23 ULiège)