Vanessa Rosso

Almost-common path interferometer using the separation of polarization states for digital phase-shifting shearography

An original experimental setup for shearography with metrological applications is presented. The simplicity and the efficiency of the setup are provided by a shearing device, a prism that separates the TE and TM polarization modes with a coating and a thin glass plate placed on its face. The use of this shearing device enables an in-line and almost-common path configuration for the shearing interferometer, a path that leads to high stability and a low sensitivity to external disturbances. Moreover, the sensitivity of the interferometer can be easily adjusted for different applications by varying the shearing amount with glass plates of different thicknesses or by moving the shearing device between two lenses along the optical axis. The temporal phase-shifting method is applied through the use of a liquid crystal variable retarder.

Out-of-plane displacement derivative measurement: comparison of results obtained by a shearographic interferometer using the separation of the polarization states and the finite element method

An original experimental setup for shearography with metrological applications is presented herein. The simplicity and the efficiency of the setup are provided by a shearing device, a prism that separates the TE and TM polarization modes with a coating and a thin glass plate attached on its face. The temporal phase shifting method is applied through the use of a liquid crystal variable retarder. The use of this shearing device enables an in-line and almostcommon path configuration for the shearing interferometer, a path that leads to high stability of the interferometer and a low sensitivity to external disturbances. In order to prove the efficiency and the accuracy of this speckle shearing interferometer, the out-of-plane displacement derivative relative to the shearing interferometry direction of a centrally loaded steel plate has been measured by the shearographic interferometer and then compared with the out-of-plane displacement derivative computed from the displacement field provided by the finite element method. The results are in good agreement.

Highlighting properties of filters for their application in temporal phase shifting interferometry

The goal of this work is to develop a simple and systematic method to highlight the properties of filters for their application in temporal phase shifting interferometry. In this study, the effects of elementary filters (mean, gaussian and median masks) are analyzed. In order to compare those filters, correlation fringes were numerically synthesized and a Gaussian noise has been added. The advantages and the failures of each studied filtering mask have been enhanced thanks to the comparison of different profiles and fidelity functions. Finally, this study is applied to the filtering of a shearogram recorded in our laboratory.

Simultaneous coherent imaging and strain measurement using coupled photorefractive holography and shearography.

By coupling photorefractive holography with speckle shearography, it is possible to simultaneously perform both coherent imaging and strain measurement. Use of the photorefractive effect, which is insensitive to incoherently scattered light, is a significant advantage in coherent imaging as described. Experimental results obtained from a centrally loaded steel plate are presented.

Simultaneous strain and coherent imaging using coupled photorefractive holography and shearography through scattering media

The direct simultaneous acquisition of coherent imaging and strain information is of particular importance in the biomechanical characterization of biological tissue. This type of simultaneous information acquisition can be accomplished using a coupled photorefractive holography and shearography system for imaging and strain measurements, respectively. Optical scattering in a conventional speckle shearing interferometer rapidly reduces the contrast of the shearing fringes, thereby limiting the use of such interferometers with opaque surfaces. By coupling photorefractive holography with speckle shearing interferometry, properties of the photorefractive effect (spatial high-pass filtering and temporal low-pass filtering) combine to restore the shearing fringe contrast and enable strain imaging in diffusing media. This effect is demonstrated using synthetic scattering phantoms built from suspensions of silica spheres in water.

Quantification of defect size in shearing direction by shearography and wavelet transform

Shearography is a recognized interferometric technique in non-destructive testing to detect defects. Defects are detectable in wrapped phase maps because they are characterized in their neighborhood by singular fringes. They are detectable in unwrapped phase maps, because they induce unexpected phase values. By analyzing the length of unexpected phase values area in shearing direction, and by taking into consideration shearing amount, defect size can be locally estimated. To examine this length, we propose to locally determine borders of unexpected phase values region by analyzing wavelet transform of unwrapped phase map profiles. The borders of defect area are found by examining the convergence at fine scales of lines of wavelet modulus maxima. To have a physical interpretation of this convergence, second derivate of a Gaussian is employed as mother wavelet: estimated borders of defect region are some maximal curvature points of unwrapped phase map profile. To finish, we show that shearing amount does not affect estimated defect size with our methodology. So, shearography is adapted to quantify defects in shearing direction. Currently, in any other direction, an ambiguity exists on the position where the local estimation of defect width is performed. The methodoly cannot be employed.

An almost-common path shearographic interferometer using the separation of the polarization states

An original experimental setup for shearography with metrological applications is presented herein. The simplicity and the efficiency of the setup are provided by a shearing device, a prism that separates the TE and TM polarization modes with a coating and a thin glass plate attached on its face. The use of this shearing device enables an in-line and almost-common path configuration for the shearing interferometer, a path that leads to high stability of the interferometer and a low sensitivity to external disturbances. Moreover the sensitivity of the interferometer can be easily adjusted for different applications. The temporal phase shifting method is applied through the use of a liquid crystal variable retarder.

Size-dependent third order optical nonlinearity of InP nanoparticles colloidal solution

The third order nonlinear optical effect called the optical Kerr effect was studied in InP nanoparticles solutions. The synthesized InP nanoparticles have sizes ranging from 1.5 to 3.5 nm and each sample is characterized by its sizes distribution. The Z-scan technique was used to study nonlinear absorption and refraction. Different lasers were used, hence different nonlinear refraction effects were observed at different wavelengths (532, 633 and 1550 nm) and at different time scales (continuous and femtosecond).