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Remote sensing finds more and more applications from industrial control to face recognition not forgetting terrain surveying. This trend is well exemplified by fringe projection techniques which enjoyed a considerable development in the recent years. In addition of high requirement in terms of measurement accuracy and spatial resolution the end users of full field techniques show a growing interest for dynamic regimes. We report here what we believe to be the use for the first time of a CMOS 3 layer color sensor (Foveon X3) as the key element of a RGB fringe projection system together with the processing specifically elaborated for this sensor. The 3 layer architecture allows the simultaneous recording of three phase shifted fringe patterns and features the precious asset of an unambiguous relationship between the physical sensor pixel and the picture pixel and this for each color layer on the contrary of common color sensor arrays (Bayer mosaic and tri CCD). Due to the overlapping of the spectral responses of the layers color transformation is mandatory to achieve the separation of the three phase shifted RGB projected fringe patterns. In addition we propose the use of the Empirical Mode Decomposition to equalize the non uniform responses of the three layers. Although the conversion of the phase into a height is of primary importance in an actual measurement it is not treated here the literature being profuse on the central projection model.

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.

Testing of materials and structures is more and more frequently carried out by means of optical full field measurement methods. The main reasons of this trend are well recognized. They are in the easiness for optical methods to achieve a very wide range of spatial and temporal resolutions to adapt themselves to the size of the investigated objects to interrogate simultaneously all the points of the object surface and to imply only vanishing small interactions between light and investigated objects. Their immunity to electromagnetic interferences is also highly appreciated. In the tool box of optical methods of measurement two sets of techniques have been lately developed: digital image correlation and speckle interferometry. Here we will concentrate on speckle interferometry (SI) techniques and more specifically on the processing of the signals they produce in dynamic stress regimes. Though a well established body of knowledge describes the SI techniques themselves the processing steps are by contrast still quite open to new developments. If the standard and unsurpassed processing method in static regimes is undoubtedly phase shifting the situation is not as clear for dynamic regimes. We choose to select and present three groups of processing methods: i) dynamic phase shifting ii) Morlet wavelet analysis and iii) a combination abbreviated “Hilbert approach” made actually of Empirical Mode Decomposition (EMD) Hilbert transform (HT) and piecewise processing based on the Delaunay triangulation.

In many instances experimental mechanics requires measuring the shape of material samples or structural members in stressed or un stressed conditions statically or dynamically. Numerous optical methods are good candidates to carry out these measurements including fringe projection stereo photogrammetry moiré methods interferometry deflectometry tacheometry ... Fringe projection techniques are a priori attractive because the distortion of the projected pattern by the object surface heights can be readily observed and recorded providing a first and immediate visual evaluation of its topography. In addition at least four decades of steady advances have brought the technique to a very high level of performances . In the recent years the most noticeable progress has been the recourse to multiplexing schemes involving simultaneous acquisitions of several spatial or spectral information channels. In particular three color fringe projection having the potential to gather in a single shot three times as much data as a standard black and white acquisition is likely to significantly improve the technique and opens the way to real time operation. In this contribution we report what we believe to be the use for the first time of a 3 layer color sensor as the key element of a RGB fringe projection system.

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.

This project investigates skin anatomy and physiology by three optical, non-invasive techniques: Fringe projection topography mainly for the investigation of tissue topography Parallel laser Doppler blood flow imaging for the investigation of tissue micro circulation , and Optical Coherence Tomography (OCT) assessing the anatomy and tissue morphology The different methods are compared and contrasted with respect to their ability to analyse the microstructure of healthy human skin.

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 re-examine 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.