References of "Georges, Marc"
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See detailAccurate π/2-phase shifting setup for a stabilized interference pattern of light fringes
de Oliveira, Ivan; Borges Bertasso, Flavio; Georges, Marc ULiege et al

in Optik - International Journal for Light and Electron Optics (2019), 178

We report on a technique for accurately π/2-phase shifting a stabilized interference pattern of light fringes used for building up a map of phase for 2D deformation measurement. This technique is based on ... [more ▼]

We report on a technique for accurately π/2-phase shifting a stabilized interference pattern of light fringes used for building up a map of phase for 2D deformation measurement. This technique is based on the use of low amplitude phase modulation on the setup in order to generate first and second harmonics temporal terms in the pattern of light to operate an actively stabilized setup. Particular features of this stabilization setup allow one to use them for accurate π/2-phase shifting with the practical advantage of operating on an already stabilized pattern of fringes. [less ▲]

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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 ▲]

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See detailProcessing of binary fringe patterns obtained by phase-shifting time-averaged shearography on vibrating objects
Kirkove, Murielle ULiege; Guérit, Stéphanie; Jacques et al

in Proc. SPIE 10834, Speckle 2018: VII International Conference on Speckle Metrology (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 ▲]

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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 ▲]

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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 ▲]

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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 ▲]

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See detailThermography and Shearography Inspection of Composite Hybrid Sandwich Structure Made of CFRP and GFRP Core and Titanium Skins
Georges, Marc ULiege; Srajbr, Christian; Menner, Philipp et al

in Proceedings (2018, June 22), 2018(2), 484

We have investigated several full-field contactless techniques, such as thermography and shearography, with several excitation methods for inspecting hybrid composite-metal sandwich structures. The latter ... [more ▼]

We have investigated several full-field contactless techniques, such as thermography and shearography, with several excitation methods for inspecting hybrid composite-metal sandwich structures. The latter are made of a core with epoxy reinforced by carbon and glass fibers and skins of titanium. Several calibrated defects are incorporated at different places in depth and are made of air gaps and inserts. [less ▲]

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See detailFocal plane detection via holographic autofocusing criterion applied on Terahertz TDS system
Zhao, Yuchen ULiege; Nguyen, D. T.; Hermandez, Y. et al

in Imaging and Applied Optics 2018 (3D, AO, AIO, COSI, DH, IS, LACSEA, LS&C, MATH, pcAOP) (2018, June)

Holographic autofocusing technique is applied on a terahertz time-domain spectroscopy system to improve focus accuracy. We experimentally perform the focus plane detection with TDS measurement. Amplitude ... [more ▼]

Holographic autofocusing technique is applied on a terahertz time-domain spectroscopy system to improve focus accuracy. We experimentally perform the focus plane detection with TDS measurement. Amplitude and phase information at different wavelengths are extracted. [less ▲]

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See detailImagerie Terahertz pour l’inspection des composites
Georges, Marc ULiege; Zhao, Yuchen ULiege

Conference given outside the academic context (2018)

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See detailThermal infrared and terahertz digital holography and their applications
Georges, Marc ULiege

Scientific conference (2017, October 03)

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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 ▲]

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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 ▲]

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See detailAccuracy improvement in digital holographic-based speckle correlation for three-dimensional (3D) displacement measurement
Zhao, Yuchen ULiege; Zemmamouche, Redouane; Vandenrijt, Jean-François ULiege et al

in Digital Holography and Three-Dimensional Imaging (2017, June)

Combination of digital holography and speckle correlation for three-dimensional displacement measurement suffers from inaccuracy. Speckle size adjustment and phase error correction during the digital ... [more ▼]

Combination of digital holography and speckle correlation for three-dimensional displacement measurement suffers from inaccuracy. Speckle size adjustment and phase error correction during the digital holography process can improve the accuracy of in-plane displacement measurement. [less ▲]

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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 ▲]

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See detailContrôle non destructif champ complet. Techniques et applications
Georges, Marc ULiege

Learning material (2017)

Ce cours a été donné lors de la journée de formation préliminaire au Colloque Francophone CMOI-FLUVISU de la Société Française d'Optique (SFO). Il s'adresse aux étudiants et chercheurs souhaitant une mise ... [more ▼]

Ce cours a été donné lors de la journée de formation préliminaire au Colloque Francophone CMOI-FLUVISU de la Société Française d'Optique (SFO). Il s'adresse aux étudiants et chercheurs souhaitant une mise à niveau avant d'assister au colloque. Le cours traite du controle non destructif par techniques optiques sans contact et champ complet, en vue de la mesure de déformation, la détection de défauts, la caractérisation non destructive des matériaux. [less ▲]

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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 ▲]

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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 ▲]

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See detailThermo-elastic deformation measurement of the Euclid near infrared focal plane array by long wave infrared digital holography
Vandenrijt, Jean-François ULiege; Thizy, Cédric ULiege; Salvador, Lucas ULiege et al

in Proceedings of SPIE : The International Society for Optical Engineering (2017), 10563

The Near Infrared Spectrometer and Photometer (NISP) is an instrument onboard the Euclid mission from the European Space Agency. © 2017 SPIE.

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

in Proceedings of SPIE : The International Society for Optical Engineering (2017), 10564

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 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. © 2012 ESA and CNES. [less ▲]

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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 ▲]

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