pierre jacquot - Academia.edu (original) (raw)

Papers by pierre jacquot

Springer eBooks, 2007

In many respects, speckle interferometry (SI) techniques are being considered as mature tools in ... more In many respects, speckle interferometry (SI) techniques are being considered as mature tools in the experimental mechanics circles. These techniques have enlarged considerably the field of optical metrology, featuring nanometric sensitivities in whole-field measurements of profile, shape and deformation of mechanical rough surfaces. Nonetheless, when we consider classical fringe processing techniques, e.g. phase-shifting methods, the deformation range is intrinsically limited to the correlation volume of the speckle field. In addition, the phase evaluation from such patterns is still computationally intensive, especially in the characterisation of dynamic regimes, for which there is a growing interest in a wide range of research and engineering activities. A promising approach lies in the pixel history analysis. We propose in this paper to implement the empirical mode decomposition (EMD) algorithm in a fast way, to put the pixel signal in an appropriate shape for accurate phase computation with the Hilbert transform.

Fringe 2009, 2009

A new application of the Delaunay triangulation: The processing of speckle interferometry signals... more A new application of the Delaunay triangulation: The processing of speckle interferometry signals Sébastien Equis and Pierre Jacquot STI-NAM, Ecole Polytechnique Fédérale de Lausanne 1015 Lausanne Switzerland 1 Introduction It is now more than thirty years that speckle ...

Optics Express, 2009

In a wider and wider range of research and engineering activities, there is a growing interest fo... more In a wider and wider range of research and engineering activities, there is a growing interest for full-field techniques, featuring nanometric sensitivities, and able to be addressed to dynamic behaviors characterization. Speckle interferometry (SI) techniques are acknowledged as good candidates to tackle this challenge. To get rid of the intrinsic correlation length limitation and simplify the unwrapping step, a straightforward approach lies in the pixel history analysis. The need of increasing performances in terms of accuracy and computation speed is permanently demanding new efficient processing techniques. We propose in this paper a fast implementation of the Empirical Mode Decomposition (EMD) to put the SI pixel signal in an appropriate shape for accurate phase computation. As one of the best way to perform it, the analytic method based on the Hilbert transform (HT) of the so-transformed signal will then be reviewed. For short evaluation, a zero-crossing technique which exploits directly the extrema finding step of the EMD will be presented. We propose moreover a technique to discard the under-modulated pixels which yield wrong phase evaluation. This work is actually an attempt to elaborate a phase extraction procedure which exploits all the reliable information in 3D,-two space and one time coordinates-, to endeavor to make the most of SI raw data.

Strain, Jan 10, 2008

With its nearly 40 years of existence, speckle interferometry (SI) has become a complete techniqu... more With its nearly 40 years of existence, speckle interferometry (SI) has become a complete technique, widely used in many branches of experimental mechanics. It is thus a challenging task to try to summarise in a couple of pages its principal characteristics from both theoretical and practical points of view. Admittedly, even though this goal is not met here, it appeared worth attempting to provide the photomechanics community with a discussion of the ins and outs of the technique. The necessity of a vocabulary free of ambiguity was a prerequisite, and hence the first section is a plea for a clearer definition of the discipline. Moreover, this section offers the opportunity to reexamine the basic aspects of SI. Then, the main features of the method are briefly considered following a strengths, weaknesses, opportunities and threats (SWOT) analysis. Endowed with a lot of specific advantages, compared with other whole-field methods, SI can play an increasing role in photomechanics.

Graphite-epoxy laminates are subjected to the "incremental hole-drilling" technique in ... more Graphite-epoxy laminates are subjected to the "incremental hole-drilling" technique in order to investigate the residual stresses acting within each layer of the composite samples. In-plane speckle interferometry is used to measure the displacement field created by each drilling increment around the hole. Our approach features two particularities i) we rely on the precise repositioning of the samples in the optical set-up after each new boring step, performed by means of a high precision, numerically controlled milling machine in the workshop; ii) for each increment, we acquire three displacement fields, along the length, the width of the samples, and at 45°, using a single symmetrical double beam illumination and a rotary stage holding the specimens. The experimental protocol is described in detail and the experimental results are presented, including a comparison with strain gages. Speckle interferometry appears as a

Keywords: 435/ICOM Reference ICOM-CONF-2001-007 Record created on 2008-01-24, modified on 2016-08-08

SPIE Proceedings, 2006

In biological investigations, many protocols using optical trapping call for the possibility to t... more In biological investigations, many protocols using optical trapping call for the possibility to trap a large number of particles simultaneously. Interference fringes provide a solution for massively parallel micro-manipulation of mesoscopic objects. Concurrently, the strength of traps can be improved by raising the slope of fringe profiles, such as to create intensity gradients much higher than the ones formed by sinusoidal fringes (Young's fringes). We use a multiple-beam interference system, derived from the classical Fizeau configuration, with semitransparent interfaces to generate walls of light with a very high intensity gradient (Tolansky fringes). These fringes are formed into a trapping set-up to produce new types of trapping templates. The possibility to build multiple trap arrays of various geometries is examined; a high number of particles can be trapped in those potential wells. The period of the fringes can easily be changed in order to fit traps sizes to the dimensions of the confined objects. This is achieved by modifying several parameters of the interferometer, such as the angle and/or the distance between the beam-splitter and the mirror. It is well known that optical trapping presents a great potential when used in conjunction with microfluidics for lab-on-a-chip applications. We present an original solution for multiple trapping integrated in a microfluidic device. This solution does not require high numerical aperture objectives.

Grédiac/Full-Field Measurements and Identification in Solid Mechanics, 2012

International audienc

SPIE Proceedings, 1999

ABSTRACT Speckle interferometry is an interesting tool for the measurement of micro-deformations ... more ABSTRACT Speckle interferometry is an interesting tool for the measurement of micro-deformations and has found application in many different fields ranging from material testing to structural assessment. This kind of applications, however, has often been confined inside optical laboratories where operational conditions are optimal. This paper is devoted to the extension of speckle interferometry to various measurements--performed not inside well protected rooms but in testing halls dedicated to experimentation in civil engineering--where the environmental conditions are severe for an interferometric method.

Revue de l'Electricité et de l'Electronique, 2004

SPIE Proceedings, 2010

Interferometric signals involving speckle waves invariably exhibit phase indeterminations. These ... more Interferometric signals involving speckle waves invariably exhibit phase indeterminations. These indeterminations arise at the zero-intensities of the speckle fields, or singularities, and show themselves as a net loss of modulation depth of the interferometric signals. To bypass the difficulty associated with the processing of low modulated parts of speckle interferometry signals, we propose a novel approach based on the Delaunay triangulation (DT). The method applies in both situations of static and dynamic regimes, and is designated respectively by "sine-cosine DT filter" and "3D piecewise processing" or 3DPP-3D denoting the temporal and the two spatial coordinates of the recording. The task consists in discarding purely and simply the under-modulated parts of the signal according to a user-defined binary criterion, and filling the missing parts by interpolation. This first step provides a grid with nodes randomly occupied by reliable phase values or empty. At the empty nodes, the computed phase values result from a DT ensuring that the interpolation relies on the three closest well-behaved neighbors, followed by spline-fitting a smooth surface over them. In a dynamic regime-where the benefits of the temporal approach are unanimously acknowledged-the empirical mode decomposition is used to select the valid intervals and the Hilbert transform to compute phase data therein. We give a detailed description of the DT filtering techniques, show their ability to offer the optimal compromise between spatial and measurement resolutions depending on the user-chosen binary criterion and highlight some definite advantages over classical filtering methods in terms of phase error reduction and algorithmic complexity.

SPIE Proceedings, 2006

The basic convolution integral, h Uo Uf ⊗ = , where Uo is a random object complex amplitude and h... more The basic convolution integral, h Uo Uf ⊗ = , where Uo is a random object complex amplitude and h the impulse response of the system under consideration, serves to model the observed speckle field Uf. Depending on the choice of h, the simulated field is an objective or a subjective speckle pattern. The computation makes use of two consecutive Fast Fourier Transforms. In the reported examples, the object function represents a pure phase diffuser ruled by a uniform distribution. The probability density functions (PDF) of the simulated intensity and phase patterns fit very well with their analytical counterparts obtained under the classical Gaussian hypotheses. Phase maps exhibit the awaited singularities. Moreover, elements of second order statistics, as the autocorrelation functions, are in very good agreement too. Furthermore, subtle effects, as the dip of contrast in the focused image plane of partially developed speckle patterns, are also suitably disclosed. The linear model thus appears, all together, as conceptually easy, very flexible, computationally simple, very accurate for a wide range of experiments, and endowed with excellent predictive and speculative potentials.

SPIE Proceedings, 2005

Shaping optical fields is the key issue in the control of optical forces that pilot the manipulat... more Shaping optical fields is the key issue in the control of optical forces that pilot the manipulation of mesoscopic polarizable dielectric particles. The latter can be positioned according to endless configurations. The scope of this paper is to review and discuss several unusual designs which produce what we think are among some of the most interesting arrangements. The simplest schemes result from interference between two or several coherent light beams, leading to periodic as well as pseudo-periodic arrays of optical traps. Complex assemblages of traps can be created with holographic-type set-ups; this case is widely used by the trapping community. Clusters of traps can also be configured through interferometric-type set-ups or by generating external standing waves by diffractive elements. The particularly remarkable possibilities of the Talbot effect to generate three-dimensional optical lattices and several schemes of self-organization represent further very interesting means for trapping. They will also be described and discussed. in this paper. The mechanisms involved in those trapping schemes do not require the use of high numerical aperture optics; by avoiding the need for bulky microscope objectives, they allow for more physical space around the trapping area to perform experiments. Moreover, very large regular arrays of traps can be manufactured, opening numerous possibilities for new applications.

In a two-beam interference experiment involving at least one speckle wave, intensity and phase ar... more In a two-beam interference experiment involving at least one speckle wave, intensity and phase are rapidly fluctuating distributions. There is no way to make a prediction of the evolution of the interference pattern over distances greater than the correlation volume-as small as 3x3x100 µm 3 for visible wavelengths and usual apertures. Most of the difficulties associated with a correct understanding and a good practice of speckle interferometry (SI) arise from this observation. It also explains why a technique simply ruled by the elementary two-beam interference or triangle formula raises nonetheless many problems. This contribution reviews some of the fundamentals of SI, mainly those concerned with the consequences of the random nature of the speckle phenomenon. It discusses what is thought to be the most interesting optical arrangements, modi operandi and phase extraction schemes, and finally presents selected applications. Constantly kept in mind is the idea to try to cope with the apparent disorder of the analyzed speckle distributions.

Speckle 2010: Optical Metrology, 2010

The dynamics of liquid-liquid mixing is a difficult problem, encountered in many scientific and e... more The dynamics of liquid-liquid mixing is a difficult problem, encountered in many scientific and engineering branches. Experiments in this field are mandatory to help building sound mathematical models, finding out the best fit parameters, evaluating the degree of confidence of these models, or detecting traces of unwanted dangerous substances. The investigations reported here are driven by water pollution concerns. For analyzing the water-pollutant blending behavior, dynamic speckle interferometry has been preferred to more standard optical full field methods, like deflectometry, or classical and holographic interferometry. The choice of this technique is vindicated. The opto-fluidic system is described. A first series of results is presented, demonstrating the effectiveness of the technique and showing qualitatively how two liquids blend in controlled conditions. In the last part of the paper, recently appeared processing schemes, including empirical mode decomposition, Hilbert transform and piecewise treatment, give access to the numerical values of the phase maps computed for each frame of the recorded sequence. These phase maps represent the refractive index distributions integrated along the line of sight. They provide a better visualization of the dynamics of the blending behavior and therefore an improved understanding of the phenomena. These encouraging preliminary results should open the door to a full characterization of the method and to further flow investigations and diagnostics.

We present a combination of topography measurements based on digital fringe projection and blood ... more We present a combination of topography measurements based on digital fringe projection and blood flow imaging based on Laser Doppler Imaging (LDI). Both techniques are optical, non-contact and high-speed whole-field methods well suited for in-vivo measurements on the skin. Laser Doppler perfusion imaging is an interferometric technique used for visualization of two-dimensional (2D) maps of blood flow. Typically the measured sample has a surface with a specific 3D relief. In many cases the sample relief can be of importance for correct interpretation of the obtained perfusion data. We combined the topography and the blood flow data obtained from the same object. The structural information provided by the topography is completed by the functional images provided by LDI.

Sensors Set

Figure 23-3. Reconstructing a hologram of a threedimensional object.

Strain, 2010

In many respects, speckle interferometry (SI) techniques are being considered as mature tools in ... more In many respects, speckle interferometry (SI) techniques are being considered as mature tools in the experimental mechanics circles. These techniques have enlarged considerably the field of optical metrology, featuring nanometric sensitivities in whole-field measurements of profile, shape and deformation of mechanical rough surfaces. Nonetheless, when we consider classical fringe processing techniques, e.g. phase-shifting methods, the deformation range is intrinsically limited to the correlation volume of the speckle field. In addition, the phase evaluation from such patterns is still computationally intensive, especially in the characterisation of dynamic regimes, for which there is a growing interest in a wide range of research and engineering activities. A promising approach lies in the pixel history analysis. We propose in this paper to implement the empirical mode decomposition (EMD) algorithm in a fast way, to put the pixel signal in an appropriate shape for accurate phase computation with the Hilbert transform.

Optics Letters, 2011

In speckle interferometry (SI), temporal signals are amplitude-and frequency-modulated signals an... more In speckle interferometry (SI), temporal signals are amplitude-and frequency-modulated signals and exhibit a fluctuating background. Prior to phase computation, this background intensity must be eliminated. Here our approach is to build a complex signal from the raw one and to fit a circle through the points cloud representing its sampled values in the complex plane. The circle fit is computed from a set of points whose length is locally adapted to the signal. This procedure-new to our knowledge in SI-yields the background and the modulation depth and leads to the determination of the instantaneous frequency. The method, applied to simulated and experimental signals, is compared to empirical mode decomposition (EMD). It shows great robustness in the computation of the sought quantities in SI, especially with signals close to the critical sampling or, on the contrary, highly oversampled, situations where the background elimination by EMD is the most prone to errors.

Springer eBooks, 2007

In many respects, speckle interferometry (SI) techniques are being considered as mature tools in ... more In many respects, speckle interferometry (SI) techniques are being considered as mature tools in the experimental mechanics circles. These techniques have enlarged considerably the field of optical metrology, featuring nanometric sensitivities in whole-field measurements of profile, shape and deformation of mechanical rough surfaces. Nonetheless, when we consider classical fringe processing techniques, e.g. phase-shifting methods, the deformation range is intrinsically limited to the correlation volume of the speckle field. In addition, the phase evaluation from such patterns is still computationally intensive, especially in the characterisation of dynamic regimes, for which there is a growing interest in a wide range of research and engineering activities. A promising approach lies in the pixel history analysis. We propose in this paper to implement the empirical mode decomposition (EMD) algorithm in a fast way, to put the pixel signal in an appropriate shape for accurate phase computation with the Hilbert transform.

Fringe 2009, 2009

A new application of the Delaunay triangulation: The processing of speckle interferometry signals... more A new application of the Delaunay triangulation: The processing of speckle interferometry signals Sébastien Equis and Pierre Jacquot STI-NAM, Ecole Polytechnique Fédérale de Lausanne 1015 Lausanne Switzerland 1 Introduction It is now more than thirty years that speckle ...

Optics Express, 2009

In a wider and wider range of research and engineering activities, there is a growing interest fo... more In a wider and wider range of research and engineering activities, there is a growing interest for full-field techniques, featuring nanometric sensitivities, and able to be addressed to dynamic behaviors characterization. Speckle interferometry (SI) techniques are acknowledged as good candidates to tackle this challenge. To get rid of the intrinsic correlation length limitation and simplify the unwrapping step, a straightforward approach lies in the pixel history analysis. The need of increasing performances in terms of accuracy and computation speed is permanently demanding new efficient processing techniques. We propose in this paper a fast implementation of the Empirical Mode Decomposition (EMD) to put the SI pixel signal in an appropriate shape for accurate phase computation. As one of the best way to perform it, the analytic method based on the Hilbert transform (HT) of the so-transformed signal will then be reviewed. For short evaluation, a zero-crossing technique which exploits directly the extrema finding step of the EMD will be presented. We propose moreover a technique to discard the under-modulated pixels which yield wrong phase evaluation. This work is actually an attempt to elaborate a phase extraction procedure which exploits all the reliable information in 3D,-two space and one time coordinates-, to endeavor to make the most of SI raw data.

Strain, Jan 10, 2008

With its nearly 40 years of existence, speckle interferometry (SI) has become a complete techniqu... more With its nearly 40 years of existence, speckle interferometry (SI) has become a complete technique, widely used in many branches of experimental mechanics. It is thus a challenging task to try to summarise in a couple of pages its principal characteristics from both theoretical and practical points of view. Admittedly, even though this goal is not met here, it appeared worth attempting to provide the photomechanics community with a discussion of the ins and outs of the technique. The necessity of a vocabulary free of ambiguity was a prerequisite, and hence the first section is a plea for a clearer definition of the discipline. Moreover, this section offers the opportunity to reexamine the basic aspects of SI. Then, the main features of the method are briefly considered following a strengths, weaknesses, opportunities and threats (SWOT) analysis. Endowed with a lot of specific advantages, compared with other whole-field methods, SI can play an increasing role in photomechanics.

Graphite-epoxy laminates are subjected to the "incremental hole-drilling" technique in ... more Graphite-epoxy laminates are subjected to the "incremental hole-drilling" technique in order to investigate the residual stresses acting within each layer of the composite samples. In-plane speckle interferometry is used to measure the displacement field created by each drilling increment around the hole. Our approach features two particularities i) we rely on the precise repositioning of the samples in the optical set-up after each new boring step, performed by means of a high precision, numerically controlled milling machine in the workshop; ii) for each increment, we acquire three displacement fields, along the length, the width of the samples, and at 45°, using a single symmetrical double beam illumination and a rotary stage holding the specimens. The experimental protocol is described in detail and the experimental results are presented, including a comparison with strain gages. Speckle interferometry appears as a

Keywords: 435/ICOM Reference ICOM-CONF-2001-007 Record created on 2008-01-24, modified on 2016-08-08

SPIE Proceedings, 2006

In biological investigations, many protocols using optical trapping call for the possibility to t... more In biological investigations, many protocols using optical trapping call for the possibility to trap a large number of particles simultaneously. Interference fringes provide a solution for massively parallel micro-manipulation of mesoscopic objects. Concurrently, the strength of traps can be improved by raising the slope of fringe profiles, such as to create intensity gradients much higher than the ones formed by sinusoidal fringes (Young's fringes). We use a multiple-beam interference system, derived from the classical Fizeau configuration, with semitransparent interfaces to generate walls of light with a very high intensity gradient (Tolansky fringes). These fringes are formed into a trapping set-up to produce new types of trapping templates. The possibility to build multiple trap arrays of various geometries is examined; a high number of particles can be trapped in those potential wells. The period of the fringes can easily be changed in order to fit traps sizes to the dimensions of the confined objects. This is achieved by modifying several parameters of the interferometer, such as the angle and/or the distance between the beam-splitter and the mirror. It is well known that optical trapping presents a great potential when used in conjunction with microfluidics for lab-on-a-chip applications. We present an original solution for multiple trapping integrated in a microfluidic device. This solution does not require high numerical aperture objectives.

Grédiac/Full-Field Measurements and Identification in Solid Mechanics, 2012

International audienc

SPIE Proceedings, 1999

ABSTRACT Speckle interferometry is an interesting tool for the measurement of micro-deformations ... more ABSTRACT Speckle interferometry is an interesting tool for the measurement of micro-deformations and has found application in many different fields ranging from material testing to structural assessment. This kind of applications, however, has often been confined inside optical laboratories where operational conditions are optimal. This paper is devoted to the extension of speckle interferometry to various measurements--performed not inside well protected rooms but in testing halls dedicated to experimentation in civil engineering--where the environmental conditions are severe for an interferometric method.

Revue de l'Electricité et de l'Electronique, 2004

SPIE Proceedings, 2010

Interferometric signals involving speckle waves invariably exhibit phase indeterminations. These ... more Interferometric signals involving speckle waves invariably exhibit phase indeterminations. These indeterminations arise at the zero-intensities of the speckle fields, or singularities, and show themselves as a net loss of modulation depth of the interferometric signals. To bypass the difficulty associated with the processing of low modulated parts of speckle interferometry signals, we propose a novel approach based on the Delaunay triangulation (DT). The method applies in both situations of static and dynamic regimes, and is designated respectively by "sine-cosine DT filter" and "3D piecewise processing" or 3DPP-3D denoting the temporal and the two spatial coordinates of the recording. The task consists in discarding purely and simply the under-modulated parts of the signal according to a user-defined binary criterion, and filling the missing parts by interpolation. This first step provides a grid with nodes randomly occupied by reliable phase values or empty. At the empty nodes, the computed phase values result from a DT ensuring that the interpolation relies on the three closest well-behaved neighbors, followed by spline-fitting a smooth surface over them. In a dynamic regime-where the benefits of the temporal approach are unanimously acknowledged-the empirical mode decomposition is used to select the valid intervals and the Hilbert transform to compute phase data therein. We give a detailed description of the DT filtering techniques, show their ability to offer the optimal compromise between spatial and measurement resolutions depending on the user-chosen binary criterion and highlight some definite advantages over classical filtering methods in terms of phase error reduction and algorithmic complexity.

SPIE Proceedings, 2006

The basic convolution integral, h Uo Uf ⊗ = , where Uo is a random object complex amplitude and h... more The basic convolution integral, h Uo Uf ⊗ = , where Uo is a random object complex amplitude and h the impulse response of the system under consideration, serves to model the observed speckle field Uf. Depending on the choice of h, the simulated field is an objective or a subjective speckle pattern. The computation makes use of two consecutive Fast Fourier Transforms. In the reported examples, the object function represents a pure phase diffuser ruled by a uniform distribution. The probability density functions (PDF) of the simulated intensity and phase patterns fit very well with their analytical counterparts obtained under the classical Gaussian hypotheses. Phase maps exhibit the awaited singularities. Moreover, elements of second order statistics, as the autocorrelation functions, are in very good agreement too. Furthermore, subtle effects, as the dip of contrast in the focused image plane of partially developed speckle patterns, are also suitably disclosed. The linear model thus appears, all together, as conceptually easy, very flexible, computationally simple, very accurate for a wide range of experiments, and endowed with excellent predictive and speculative potentials.

SPIE Proceedings, 2005

Shaping optical fields is the key issue in the control of optical forces that pilot the manipulat... more Shaping optical fields is the key issue in the control of optical forces that pilot the manipulation of mesoscopic polarizable dielectric particles. The latter can be positioned according to endless configurations. The scope of this paper is to review and discuss several unusual designs which produce what we think are among some of the most interesting arrangements. The simplest schemes result from interference between two or several coherent light beams, leading to periodic as well as pseudo-periodic arrays of optical traps. Complex assemblages of traps can be created with holographic-type set-ups; this case is widely used by the trapping community. Clusters of traps can also be configured through interferometric-type set-ups or by generating external standing waves by diffractive elements. The particularly remarkable possibilities of the Talbot effect to generate three-dimensional optical lattices and several schemes of self-organization represent further very interesting means for trapping. They will also be described and discussed. in this paper. The mechanisms involved in those trapping schemes do not require the use of high numerical aperture optics; by avoiding the need for bulky microscope objectives, they allow for more physical space around the trapping area to perform experiments. Moreover, very large regular arrays of traps can be manufactured, opening numerous possibilities for new applications.

In a two-beam interference experiment involving at least one speckle wave, intensity and phase ar... more In a two-beam interference experiment involving at least one speckle wave, intensity and phase are rapidly fluctuating distributions. There is no way to make a prediction of the evolution of the interference pattern over distances greater than the correlation volume-as small as 3x3x100 µm 3 for visible wavelengths and usual apertures. Most of the difficulties associated with a correct understanding and a good practice of speckle interferometry (SI) arise from this observation. It also explains why a technique simply ruled by the elementary two-beam interference or triangle formula raises nonetheless many problems. This contribution reviews some of the fundamentals of SI, mainly those concerned with the consequences of the random nature of the speckle phenomenon. It discusses what is thought to be the most interesting optical arrangements, modi operandi and phase extraction schemes, and finally presents selected applications. Constantly kept in mind is the idea to try to cope with the apparent disorder of the analyzed speckle distributions.

Speckle 2010: Optical Metrology, 2010

The dynamics of liquid-liquid mixing is a difficult problem, encountered in many scientific and e... more The dynamics of liquid-liquid mixing is a difficult problem, encountered in many scientific and engineering branches. Experiments in this field are mandatory to help building sound mathematical models, finding out the best fit parameters, evaluating the degree of confidence of these models, or detecting traces of unwanted dangerous substances. The investigations reported here are driven by water pollution concerns. For analyzing the water-pollutant blending behavior, dynamic speckle interferometry has been preferred to more standard optical full field methods, like deflectometry, or classical and holographic interferometry. The choice of this technique is vindicated. The opto-fluidic system is described. A first series of results is presented, demonstrating the effectiveness of the technique and showing qualitatively how two liquids blend in controlled conditions. In the last part of the paper, recently appeared processing schemes, including empirical mode decomposition, Hilbert transform and piecewise treatment, give access to the numerical values of the phase maps computed for each frame of the recorded sequence. These phase maps represent the refractive index distributions integrated along the line of sight. They provide a better visualization of the dynamics of the blending behavior and therefore an improved understanding of the phenomena. These encouraging preliminary results should open the door to a full characterization of the method and to further flow investigations and diagnostics.

We present a combination of topography measurements based on digital fringe projection and blood ... more We present a combination of topography measurements based on digital fringe projection and blood flow imaging based on Laser Doppler Imaging (LDI). Both techniques are optical, non-contact and high-speed whole-field methods well suited for in-vivo measurements on the skin. Laser Doppler perfusion imaging is an interferometric technique used for visualization of two-dimensional (2D) maps of blood flow. Typically the measured sample has a surface with a specific 3D relief. In many cases the sample relief can be of importance for correct interpretation of the obtained perfusion data. We combined the topography and the blood flow data obtained from the same object. The structural information provided by the topography is completed by the functional images provided by LDI.

Sensors Set

Figure 23-3. Reconstructing a hologram of a threedimensional object.

Strain, 2010

In many respects, speckle interferometry (SI) techniques are being considered as mature tools in ... more In many respects, speckle interferometry (SI) techniques are being considered as mature tools in the experimental mechanics circles. These techniques have enlarged considerably the field of optical metrology, featuring nanometric sensitivities in whole-field measurements of profile, shape and deformation of mechanical rough surfaces. Nonetheless, when we consider classical fringe processing techniques, e.g. phase-shifting methods, the deformation range is intrinsically limited to the correlation volume of the speckle field. In addition, the phase evaluation from such patterns is still computationally intensive, especially in the characterisation of dynamic regimes, for which there is a growing interest in a wide range of research and engineering activities. A promising approach lies in the pixel history analysis. We propose in this paper to implement the empirical mode decomposition (EMD) algorithm in a fast way, to put the pixel signal in an appropriate shape for accurate phase computation with the Hilbert transform.

Optics Letters, 2011

In speckle interferometry (SI), temporal signals are amplitude-and frequency-modulated signals an... more In speckle interferometry (SI), temporal signals are amplitude-and frequency-modulated signals and exhibit a fluctuating background. Prior to phase computation, this background intensity must be eliminated. Here our approach is to build a complex signal from the raw one and to fit a circle through the points cloud representing its sampled values in the complex plane. The circle fit is computed from a set of points whose length is locally adapted to the signal. This procedure-new to our knowledge in SI-yields the background and the modulation depth and leads to the determination of the instantaneous frequency. The method, applied to simulated and experimental signals, is compared to empirical mode decomposition (EMD). It shows great robustness in the computation of the sought quantities in SI, especially with signals close to the critical sampling or, on the contrary, highly oversampled, situations where the background elimination by EMD is the most prone to errors.