Since it was first observed in the early 1960s, speckle has become important in many different applications. In this paper we biefly discuss its role in holography, coherence tomography, projection TV, fiber-optic communications, lithography, optical radar detection, and metrology.

The statistical properties of three-dimensional fractal speckle fields produced by three speckle waves crossed orthogonally are studied theoretically. The analytical expressions are derived for the intensity correlation of the superposed speckle fields, and the theoretical results are verified by means of computer simulations. It is shown that the spatial anisotropy of intensity distributions, which exists in each speckle field, remains even when three speckle waves are interfered with one another. The spatial anisotropy affects the power law distribution of intensity correlations for fractal speckle fields, and leads to speckle patterns that are not self-similar in two or three dimensions. As an application of the superposed speckle field, we propose a method to fabricate a disordered medium by illuminating photopolymer with multiple laser speckle waves.

Millimeter waves are able to penetrate materials that are usually opaque to both visible and infrared radiation. We used this advantage to design a free-space active millimeter-wave imaging set up for security applications. Because all existing mm-wave sources are coherent - speckle is one of the ultimate limiting factors of the imaging techniques. This problem is of special importance for mm-wave imaging, because surface roughness is closer to the object dimension as in optical imaging. The reduction of speckle is highly desirable and we propose here a Hadamard matrix solution, which is one of the most efficient ways to reduce speckle noise. By illuminating the object with a series of orthogonal phase patterns corresponding to permutations of Hadamard matrices, one can convert the sum of electrical fields (coherent) in the image pixel into a sum of intensities (non-coherent). We report a 50% speckle reduction. The effect of speckle reduction was measured using both a vector network analyzer and a W-band free-space scalar calibrated measurement setup. We processed 2 different Hadamard diffusers and present here measurement data discussing speckle contrast as a function of frequency.

Active polarimetric imagery is a powerful tool for accessing the information present in a scene. The polarimetric images obtained can indeed reveal polarizing properties of the objects that could not appear using conventional imaging systems.^1,2 The degree of polarization is a key quantity to define the way the scene polarizes or depolarizes the light. Its estimation³ from images obtained with illumination by coherent light is perturbed by speckle noise. Using the definition developed by Goodman,⁴ we propose in this paper to perform both a theoretical and a numerical experimental study on the estimation of the degree of polarization. We first present that one can estimate the degree of polarization with only two intensity measures, whereas four measures are used in classical studies. This method may have interesting practical applications. Indeed, the use of only two images could reduce the costs and could improve the acquisition time. The quantification of the loss of precision in the estimation of the degree of polarization is analyzed when one uses two images instead of four. This analysis is based on statistical studies considering the speckle noise in the data. The precision on the estimation of the degree of polarization is compared using either the electric field (that needs four measurements) or only two intensity measures. The theorical results are validated on simulated polarimetric data considering different situations described by different polarization matrices.

We address the problem of defining degrees of coherence for partially polarized light. We discuss a new theoretical approach that introduces intrinsic degrees of coherence. These parameters make it possible to separate partial polarization and partial coherence and are measurable quantities. We analyze their physical meaning and propose a method to measure them with a finite number of measurement.

The investigation of the speckle fields obtained from biological fluids or tissues, can be used in medical applications, as an experimental non invasive method to get informations using low cost and low energy lasers. We give a few examples concerning the application of speckle and polarization analysis in the investigation of blood coagulation, platelets aggregation and deterioration of skin by gamma radiation.

The article is devoted to investigation of the statistical polarization parameters of biological tissues histological section images with different morphological structure. The paper consists of the results of polarization coordinate mapping and analysis of the statistics of the first-fourth orders of biological tissues images polarization azimuth and ellipticities.

Identification of mechanical properties of materials is a complicated reverse engineering problem which can be solved by minimizing the difference between displacements measured experimentally and their counterpart predicted by FEM analysis. Non-linearity entailed by identification problem leads to combine global optimization techniques with full-field experimental techniques. This paper presents an example of application of a hybrid identification procedure to cortical bone specimens cut from bovine long bones. Specimens can be modeled in fashion of a transversely orthotropic material. In-plane displacements are measured by means of Phase Shifting Electronic Speckle Pattern Interferometry while stiffness parameters are determined by means of Simulated Annealing. Results show that material properties are in good agreement with data recently published in literature.

In order to understand complex-hierarchical biomaterials such as bones and teeth, it is necessary to relate their structure and mechanical-properties. We have adapted electronic speckle pattern-correlation interferometry (ESPI) to make measurements of deformation of small water-immersed specimens of teeth and bones. By combining full-field ESPI with precision mechanical loading we mapped sub-micron displacements and determined material-properties of the samples. By gradually and elastically compressing the samples, we compensate for poor S/N-ratios and displacement differences of about 100nm were reliably determined along samples just 2~3mm long. We produced stress-strain curves well within the elastic performance range of these materials under biologically relevant conditions. For human tooth-dentin, Young's modulus in inter-dental areas of the root is 40% higher than on the outer sides. For cubic equine bone samples the compression modulus of axial orientations is about double the modulus of radial and tangential orientations (20 GPa versus 10 GPa respectively). Furthermore, we measured and reproduced a surprisingly low Poisson's ratio, which averaged about 0.1. Thus the non-contact and non-destructive measurements by ESPI produce high sensitivity analyses of mechanical properties of mineralized tissues. This paves the way for mapping deformation-differences of various regions of bones, teeth and other biomaterials.

This paper presents an overview about some possibilities to use electronic speckle pattern interferometry for measuring in cylindrical or in-plane polar coordinates. Out-of-plane deformation measurement of cylindrical surfaces can be done for either internal or external cylinders using conical mirrors. A special configuration for measuring long internal cylinders is also discussed and a practical application is presented. Another configuration uses conical mirror for double illuminate a flat area to measure the in-plane radial displacement component. This configuration has been successfully used for 2D translations, stress and residual stresses measurements.

Ultrasonic Lamb waves provide a useful means for the nondestructive determination of the material elastic constants of shell structures such as plates, pipes, cans and many others. A new optical technique is described for the measurement of the dispersion curves of Lamb wave modes. The experimental system employs the wedge method for the excitation of Lamb modes in aluminum plates of thickness in the range of a few millimetres. Long tone-bursts are used in order to ensure the generation of narrowband ultrasonic waves. Furthermore, an appropriate selection of the wedge angle allows one to generate only the desired individual Lamb mode. The detection of the surface out-of-plane displacements is performed by our self-developed pulsed TV holography system, which evaluates the optical phase by the Spatial Fourier Transform Method. Inasmuch as a whole-field measurement is realized, the wavelength of the excited mode can be precisely measured from the TV holography displacement maps. On the other hand, the wave frequency is measured by a pointwise method, namely a Michelson speckle interferometer. The phase velocity is directly obtained as the product of these two values. Measurements are done for several frequencies and several Lamb modes, thus yielding a collection of experimental points. By fitting these results to the theoretical Rayleigh-Lamb frequency spectrum, values of the shear wave velocity and the Poisson's ratio of the plate material are obtained. For a better accuracy in the measurements, the longitudinal phase velocity was directly determined by the pulse-echo method. The additional knowledge of the mass density allows one to calculate the Young's modulus.

Liquid nematic crystals are nowadays more often used to change the polarization and/or phase and amplitude of impinging light wave. Nematic liquid crystals valves (LCLV) are also called SLM (Spatial Light Modulator) or LCVR (Liquid Crystal Variable Retarder). This paper will show the different steps required to get a procedure (optical mounting and computing software) enabling the use of LCLV in the output beam of the laser coupled with a 3D speckle interferometry set-up. This LCLV generates the phase shifts between the reference and object beams. The calibration set-up is made of a Mach Zender interferometer with the LCLV in one arm. Interference fringes are obtained and recorded with a CCD camera as LCLV voltage is increased. The fringe processing is achieved with a slice analysis in the Fourier domain. Required phase shifts are then implemented in the phase shifting software. The existing set-up already uses a phase shifter composed by a moving mirror driven by a piezoelectric transducer (PZT). Results of the calibration are compared between piezoelectric device and LCVR. The phase shifting rate and resulting phase error shows the main advantages of the LCVR. The whole set-up, with LCVR replacing the PZT, is finally applied to the determination of 3D displacement fields of Compact Tension Notch sample.

This paper describes noncontacting material testing that detects displacement of laser speckle patterns by a digital speckle correlation technique. It tracks displacement of two separated positions on a specimen by separate movable heads having a laser diode and a CCD camera. Each head is driven under the feedback control that cancels the speckle displacement detected by a real-time correlator. The position of each head is monitored by an electronic encoder to derive elongation of the specimen. Strain is evaluated from the ratio of the elongation to the original interval of the measured positions. Stress-strain curve obtained from this method agreed well with a conventional method using line markings mechanically attached on the specimen. The measurement could be carried out under the same conditions and speed as the conventional material test at 500 mm/min.

Digital Image Correlation (DIC) - also referred to as white light speckle technique - is an optical-numerical full-field measuring technique, which offers the possibility to determine in-plane displacement fields at the surface of objects under any kind of loading. For an optimal use of the method, the object of interest has to be covered with a speckle pattern. The present paper studies the efficiency of a random speckle pattern and its influence on the measured in-plane displacements with respect to the subset size. First a randomly sprayed speckle pattern is photographed three times. Each picture is taken with a different zoom, yielding three speckle patterns, which are different by the size of the speckles. Secondly a number of speckle patterns are generated numerically using a given speckle size and image coverage. Subsequently, each speckle pattern image undergoes a numerically controlled deformation, which is measured with digital image correlation software. Both imposed and measured displacements are compared and it is shown that the size of the speckles combined with the size of the used pixel subset, clearly influences the accuracy of the measured displacements. Furthermore it is shown that it is possible to create an optimal speckle pattern when a given subset size is chosen.

Systematical errors of digital image correlation (DIC) measurements build a limiting factor for the accuracy of the resulting quantities. A major source for introducing systematical errors is the system calibration. We present a 3D digital image correlation system, which provides error information not only of diverse error sources but even more the propagation of errors throughout the calculations to the resulting contours, displacements and strains. On the basis of this system we discuss error sources, error propagation and the impact on correlation results. Performance tests for studying the impact of calibration errors on the resulting data are shown.

The continued miniaturization and the increased demands on the quality of industrial products stimulate the search for new inspection technologies with enhanced resolution, faster response and improved reliability. However, optical inspection systems often reach their limits in terms of resolution, dynamic range or speed. A promising approach consists in the implementation of model based active measurement strategies. These strategies provide a new degree of flexibility with respect to the solution of challenging measurement and identification problems such as the testing of aspheres, the recognition of material faults, the measurement of dimensional quantities and the non-contact manipulation of tiny particles. But an effective implementation of appropriate algorithms requires also a new degree of freedom in wavefront control. Consequently, sophisticated light switches, light valves and spatial light modulators have become meanwhile key components with respect to an active control of all relevant parameters of the wavefront. This contribution describes several types of modern SLMs, methods for their characterization and some recent applications implemented at ITO.

We propose a framework for obtaining synthetic speckle-pattern images based on successive transformations of Perlin's coherent noise function. In addition we show how a given displacement function can be used to produce deformed images, making this framework suitable for performance analysis of speckle-based displacement/strain measurement techniques, such as Digital Image Correlation, widely used in experimental mechanics.

The use of complex amplitude correlation to determine the deformation field for in-plane motions in digital speckle pattern interferometry (DSPI) is investigated. The result is compared to experiments where only DSPI-algorithms, as well as where combined DSPI-intensity correlation are used. Experiments with and without large rigid body motions are studied. An advantage of using complex amplitude correlation instead of intensity correlation is that the phase change describing the deformation is retrieved directly from the correlation peak and there is no need to compensate for the large movement and then use interferometric algorithms to obtain the phase information. A discovered drawback of this method is that the correlation values drops very quick if there is a phase gradient larger than π across the sub image used for the cross correlation. This means that in order to use the complex amplitude correlation the size of the subimages must be proportional to the magnitude of the present deformation gradient. Or, a third parameter in the cross-correlation algorithm that compensates for the phase variation is needed.

The present paper describes a hybrid method which combines finite element analyses and genetic algorithms (GAs) for determining the elastic properties of isotropic and anisotropic materials from the full-field measurement of the displacements of plates under flexural loads. An optimized procedure based on GAs updates iteratively the elastic constants in a numerical model until the displacements obtained by numerical analysis fit the experimental data. The unknown parameters are identified simultaneously by a single test and without damaging the structure. The procedure was applied to both isotropic (aluminum) and anisotropic (Graphite/PEEK unidirectional laminate) specimens.

A novel optical system for speckle interferometry is proposed in this paper. The optical system required only 2 cameras by combining the temporal and the spatial fringe scanning methods instead of ordinary optical system which required 3 cameras at least. As results, the interferometry using multi-camera method can be realized with just 2 cameras. In the experimental results, it is confirmed that measurement for out of plane displacement that includes a large deformation in measured object can be precisely performed by the new optical system. Then, the measurement with large deformation is performed as the accumulation of the continuous measurement results with the small deformation measurement.

Subtraction correlation fringes in Digital Speckle Pattern Interferometry are described as a smoothly varying intensity distribution multiplied with high-frequency noise that is due to the random distribution of speckle intensity and speckle phase across the image plane. Although intensity modulation and speckle phase can be eliminated by phase stepping or other phase retrieval methods, noise is not eliminated completely due to the limited dynamic range of image processing, given by the saturation level of the camera, the digitisation depth and the electronic noise. Digital image processing techniques have been developed to reduce the speckle noise from the fringe pattern, but in most cases the fringes are not restored completely. In this paper the speckle noise is reduced before image digitisation by reducing the range of either the modulation intensity values or the speckle phase values, or both, in the interference pattern. This is done adaptively by using programmable twisted nematic LCDs. Since the manipulation is performed for each pixel independently in the reference beam, the imaging quality is retained and no blurring occurs. We quantitatively discuss the improvement and limitation of the method. The experimental verification is performed using an amplitude-only or phase-only spatial light modulator in a conventional ESPI setup.

The measurement of ultrasonic surface acoustic waves of nanometric amplitude by TV holography (TVH) was demonstrated some years ago. The spatial periodicity of the wavefield across the optical phase difference maps was exploited to yield the mechanical amplitude and phase of the propagating wave. Now we present a refinement of the technique where we also profit from the temporal periodicity, at each point of the surface, of the displacement induced by the wave. We record a series of sets of primary correlograms, which are processed to yield optical phase-difference maps. We change slightly the delay between the excitation of the wave and the measurement from one recording to the next, so that the position of the wavefield on the resultant images is shifted accordingly. Every point on the surface, which oscillates at the frequency of the wave, is thus recorded at several instants of its oscillation cycle in consecutive optical phase difference maps of the sequence. We have then spatial periodicity at a given instant across each image and temporal periodicity at a given point on the surface across the series of images. This feature is exploited to calculate a three-dimensional Fourier transform of the data. As we employ narrowband ultrasonic waves, the spatial content of the spectrum is contained in a small region of the spatial frequency plane and within a thin slice of temporal frequencies, and can be easily filtered and inverse Fourier transformed to obtain the mechanical amplitude and phase of the wave. This method intends to extend the detection capability of the TVH technique to ultrasonic waves of lower amplitude.

The aim of this paper concerns the phase demodulation of a fringes pattern in dynamic regime. During a dynamic loading, we can not use a phase shifting technique because the mechanical parameters involve according to the time. This problem can be avoided with the development of algorithms which can extract the information with the help of only one fringes pattern. In this way, we present two algorithms, the MPC [1] (Modulated Phase Correlation) and the pMPC [2] (polynomial Modulated Phase Correlation). These algorithms allow us to extract the phase from a single fringes pattern obtained, for example, by shadow moire, photoelasticity or interferometry. These processes are based on the use of the virtual fringes pattern which locally approaches the real fringes morphology. The similarity degree between real and virtual fringes pattern is estimated by digital correlation technique. When the best similarity is obtained, we suppose that the virtual phase function is very near of the real phase function. One particularity of these algorithms is theirs few sensitivity to noises. So, we propose to use the MPC or the pMPC algorithms in order to extract the relief in dynamic from a single interferogram obtained by digital speckle pattern interferometry. In this paper we present an experimental test of impact loading on textile specimen. The frame rate is equal to 6000 frames per second. The figure 1 shows one of the fringes patterns recorded in dynamic and the result of wrapped phase demodulated with one of ours algorithms.

The analog reconstruction of a wave front and its application in comparative measurement is well known from comparative holography. Thanks to the rapid development of high quality spatial light modulators (SLM), different methods applying the analog reconstruction of digital holograms has been developed in digital holography too. In these methods the recorded wave fronts of an object are generated by the spatial modulator. The SLM is also capable to generate computer calculated wave fronts (not belonging to an existing object), and multiple such projections can be performed during the measurement time. Using this feature an effective adaptive measuring system can be built. The application of such wave front projections is also possible in TV holography. The wave front projection can be virtually too, when the wave front exists only in the computer memory. Methods both for digital holography and TV holography are developed too.

A single-shot fringe projection profilometry system based on simultaneous projection of four phase-shifted sinusoidal fringe patterns generated at four different wavelengths is described. The system includes a fringe pattern generation module containing four blocks with four near-infrared diode lasers and a registration module with four CCD cameras. In order to simplify the technical solution and to avoid the stringent requirement for stability in the case of interferometric fringe generation, we study both theoretically and experimentally realization of the proposed system by using of a phase grating as well as a holographic optical element for reconstruction of two point sources. The results of the measurement of the relative and absolute coordinates of test objects for both types of diffraction gratings are presented.

There are no international standards or norms for the use of optical techniques for full-field strain measurement. In the paper the rationale and design of a reference material and a set of standarized materials for the calibration and evaluation of optical systems for full-field measurements of strain are outlined. A classification system for the steps in the measurement process is also proposed and allows the development of a unified approach to diagnostic testing of components in an optical system for strain measurement based on any optical technique. The results described arise from a European study known as SPOTS whose objectives were to begin to fill the gap caused by a lack of standards.

Electronic Speckle Pattern Interferometry with a light source of short coherence length allows depth-resolved deformation analysis below the surface of light-scattering objects (Low Coherence Speckle Interferometry - LCSI). Interference is tuned to a thin layer - called the coherence layer - by appropriate adjustment of the length of the reference path. The quality of the results is degraded by background light from outside the coherence layer and by de-correlations due to the passage of the useful light through regions that have been altered by the overall deformation field. Basic experimental studies are conducted on a simple two-interface object (two roughened surfaces of glass slides) to determine the effects that one interface (and its deformation) exerts on the quality of the deformation measurement in the other interface. Analytical theoretical calculations of speckle de-correlation on the basis of Fresnel diffraction provide comparative data.

In this paper the basic principles of LCSI are briefly described. Furthermore, we investigate the interference signal coming from a semitransparent, multilayer object theoretically and experimentally. The interference signal is modelled using a one-dimensional transmission line approach. The theory for this model is well known from the exact matrix theory of multilayered systems. We have extended the model for phase investigations and simulated the effect of a delamination when measuring through a semitransparent layer. The model is verified by experimental results from LCSI measurements.

An overview of the activities in low-coherence interferometry (LCI) and optical coherence tomography (OCT) at the Industrial Materials Institute are presented. An innovative optical delay line using rhombic prisms is described. A few industrial applications are described: volume loss in a wear test, combination of LCI with laser-induced breakdown spectroscopy, and modification of an existing rheometer to increase its precision. Preliminary results related to the use of speckle to differentiate tissues and materials in OCT are presented. The speckle dimension is shown to be sensitive to low density of scatterers. An additional parameter extracted from the autocorrelation of speckle is also presented.

We describe a system for measuring sub-surface displacement fields within a scattering medium using a broadband super-luminescent light emitting diode (SLED) source and spectral imaging. The use of phase information in the backscattered speckle pattern offers displacement sensitivity in the range of a few tens of nm, some two to three orders of magnitude better than the depth resolution of state-of-the-art Optical Coherence Tomography systems. The system is based on low cost components and has no moving parts. It provides displacement maps within a 2-D slice extending into the sample, and the fact that all the data for a given deformation state are acquired in a single shot is a highly attractive feature for in-vivo investigations in the biological sciences. The theoretical basis for the system is presented along with experimental results from a simple well-controlled geometry consisting of independently-tilting glass sheets. Results are validated using standard two-beam interferometry. Scattering samples were also studied and we show a wrapped phase map through the thickness of a pig ex-vivo cornea. The phase change was due to viscoelastic creep in the cornea after a change in the intraocular pressure.

In white-light interferometry at rough surfaces ("Coherence radar") the measuring uncertainty is physically limited by the arbitrary phase of the individual speckle interferograms. As a consequence, the standard deviation of the measured shape data is inevitably given by the (optically unresolved) roughness of the surface. The statistical error in each measuring point depends on the brightness of the corresponding speckle; a dark speckle yields a more uncertain measurement than a bright one. If the brightness is below the noise threshold of the camera, the measurement fails completely and an outlier occurs. We present a new method to significantly reduce the measuring uncertainty and the number of outliers. We achieve this by generating several statistically independent speckle patterns, by use of different directions of the illumination. We evaluate the different measurements and select the best measurement or assign more weight to brighter speckles

The application of multi-wavelength holography for surface shape measurement is presented. In our holographic setup a Bi₁₂TiO₂₀ (BTO) photorefractive crystal was the holographic recording medium and a multimode diode laser emitting in the red region was the light source in a two-wave mixing scheme. The holographic imaging with multimode lasers results in multiple holograms in the BTO. By employing such lasers the resulting holographic image appears covered of interference fringes corresponding to the object relief and the interferogram spatial frequency is proportional to the diode laser free spectral range (FSR). We used a Fabry-Perot etalon at the laser output for laser mode selection. Thus, larger effective values of the laser FSR were achieved, leading to higher-spatial frequency interferograms and therefore to more sensitive and accurate measurements. The quantitative evaluation of the interferograms was performed through the phase stepping technique (PST) and the phase map unwrapping was carried out through the Cellular-Automata method. For a given surface, shape measurements with different interferogram spatial frequencies were performed and compared, concerning measurement noise and visual inspection.

The principles and the practical conditions for registration of phase singularities, such as optical vortices in the spectral components of white light, are discussed. Interference diagnostics of white light vortices in a polychromatic speckle-field is reported for the first time.

A comparative digital holography system suitable for shape and deformation comparisons between master and sample objects with rough surfaces is described. The innovative aspect of comparative digital holography is the illumination of the sample by the conjugated wavefront of the master, as a type of coherent mask, using a liquid crystal display (LCD). The resulting interferogram indicates directly the shape or the deformation differences between the master and sample. As it is not necessary that both objects to be compared are located at the same place for this technique, remote shape or deformation comparison between a master and a sample is possible. A current research topic is the precise alignment of the sample and the reconstructed master wavefront so that the resulting phase map only contains information of the differences in shape or deformation. The reconstructed master wavefront can be adjusted digitally to correctly illuminate the sample object, by introducing an artificial phase-shift. This phase-shift is induced by the LCD, and offers also the possibility of calibrating precisely the set-up. The value for the phase-shift is obtained by a comparison of the resulting interferogram with a database containing fringes from simulations of misalignments between master and sample objects. Using the iterative algorithm described here, the correction of the sample position can be controlled by an automatic adaptation of the coherent mask.

We present a novel hybrid digital holographic camera which shares most of the advantages of image-plane Fourier transform TV holography (TVH) and quasi-Fourier transform digital holography (QFTDH), whilst avoiding many of the drawbacks of both of them. As in TVH, it has a compact head where an objective lens is attached to accommodate objects of different sizes or placed at different distances; it is also free from aliasing artifacts produced by objects out of the field of view. As in QFTDH, the reconstruction of the object field (amplitude and phase) is accomplished by calculating just one fast Fourier transform (FFT) per hologram; light is spread over the sensor rather than being focused to produce an image, thus enabling the measurement in objects with very large radiance ranges. An optical imaging system (typically a zoom lens) selects the field of view and the working distance by projecting a reduced image of the object on the plane of a rectangular aperture. This image becomes the object for a lensless quasi-Fourier transform digital hologram, which is formed by making the light passing through the aperture to interfere with a reference beam diverging from its edge. This hologram is recorded with a video camera, digitized and numerically reconstructed by means of a single FFT. The function of the aperture is to crop the field of view to make the effective object size suitable to be recorded without aliasing on a sensor with a given pixel spacing; therefore, its size is determined by this spacing, the distance between the aperture and the sensor as well as by the wavelength of light.

Digital In-line Holography is widely used to visualize fluid flows seeded with small particles. Such holograms record directly the far-field diffraction patterns of particles on a CCD camera. From the successive reconstruction planes, the three-dimensional location of the particles can be determined. This imaging system doesn't need focusing. The principle is based on the direct analysis of the diffraction patterns by mean of space-frequency operators such as Wavelet Transformation or Fractional Fourier Transformation. This method, already tested in our laboratory, leads to a better resolution than classical holography for the estimation of 3D particle locations (50μm instead of 0.5mm in depth). In the case of moving particles, it is interesting to illuminate the sample volume by several laser pulses. This can be easily realized by controlling the input current of a modulated laser diode. Then, the CCD camera cumulates the sum of in-line particle holograms recorded at different times. By searching for the best focus plane of each particle image, the 3D coordinate of each particle can be extracted at a given time. This technique is applied to determine trajectories of small particles in a well-controlled 2D Benard-von Karman street allowing a Lagrangian approach. Preliminary results are presented.

The problem of environmental disturbances in Digital Holographic Interferometry has been addressed in this investigation. Disturbances may be caused by vibrations, air turbulence or the presence of scattering particles and the effect of them might significantly prevent spread of the technique into a wider area of application. To handle the problem with air turbulence a temporal sequence of an event is analysed and the effect on the motion and phase of the speckles is analysed and described using statistical measures. The effect of the medium will be fed back to the sequence using an adaptive filter and the undisturbed phase evolution estimated. The principle is demonstrated using a heat source placed in between the object and the CCD camera as the disturbance on a simple tilt experiment. The presence of scattering particles is more intriguing and has to be dealt with separately. In this investigation we adopt the technique of low-coherence interferometry to depth-code the holographic images acquired. The seeding of the pulsed Nd:YAG laser source used is shut off that results in a coherence length of about one cm. The paper shows a few preliminary results from a simple wavepropagation experiment.

We review the principle and the applications of unconventional holography, called coherence holography^1,2, which we recently proposed as a general technique for the synthesis and the control of 3-D spatial coherence function. An object recorded in a hologram is reconstructed as the three-dimensional distribution of a complex spatial coherence function, rather than as the complex amplitude distribution of the optical field itself that usually represents the reconstructed image in conventional holography. We introduce a newly proposed simple optical geometry for the direct visualization of the reconstructed coherence image, along with the experimental results validating the proposed principle. We also show that coherence holography has potential applications in optical coherence tomography and profilometry³ as well as in basic science of coherence vortices⁴.

This paper aims to present the different opportunities using digital wave front reconstruction in vibration analysis. The paper deals with off axis digital holography for which the wave front reconstruction is performed by fast Fourier transform methods. According to this way for the object plane reconstruction, we discuss about image formation by considering the exposure time of the detector. For the case of a long exposure time compared to the vibration period, that is the time-averaging regime, applications are presented, examples of which include vibrations of a clarinet reed and detection of defaults in a dome mode. For the case of a short exposure time compared to the vibration period, algorithm for the full field bidimensional amplitude and phase retrieving is presented. Applications of the method are presented, example of which include modal characterization of loudspeakers and bidimensional vibrometry of elastomer components.

Digital holography is an interferometric technique directly derived from its analog counterpart. In fact the only difference with classical holography lies in the recording medium, which in the case of the digital technique, is the charged-couple device (CCD) camera sensor. Though this solution does offer several advantages, such as simpler experimental procedure, ability to numerically modify the recorded data and new analysis algorithms, it does have some drawbacks. In fact, the numerical reconstruction relies on the theoretically determined wave front shape and the small number of lines of the camera sensor restricts the viewing angle to 2-4 degrees. However, by acquiring several, slightly shifted, low resolution holograms and combining them using super-resolution techniques, it is possible to construct a higher resolution digital hologram which allows a broader viewing angle. Several approaches to super-resolution imaging have been proposed, with different requirements in terms of memory, execution speed, sensitivity to displacement and acquisition errors, One important aspect of their application to digital holography is the identification of the best "working parameters". In this paper some reconstruction algorithms are compared in order to identify the most suitable super-resolution technique and its limitations.

By combining the concept of Lateral Shear Interferometry (LSI) with Digital Holography we demonstrate that quantitative phase microscopy (QPM) can be used for investigation in different field of applications. The proposed approach gives some important advantages compared to other methods used for QPM. The method is a true single image QPM approach. In fact by using the digital shear of the reconstructed phase map in the image plane the defocus aberration introduced by the microscope objective can efficiently removed. In addition in most cases the unwrapping procedure can be avoided greatly simplifying the phase-map recovery for quantitative measurement. Numerical lateral shear of the reconstructed wave front in the image plane makes it possible to retrieve the derivative of the wave front. In analogy with the standard procedure usually applied in optical testing by means of LSI, the wave front can be reconstructed.

We describe a novel technique that we call Tilt Scanning Interferometry (TSI) to measure depth-resolved structure and displacement fields within semitransparent scattering materials. The method differs significantly from conventional optical coherence tomography in that only one wavelength is used throughout the whole measurement process. Temporal sequences of speckle interferograms are recorded whilst the illumination angle is tilted at a constant rate. Fourier transformation of the resulting three-dimensional (3-D) intensity distribution along the time axis reconstructs the scattering potential within the medium. Repeating the measurements with the object wave at equal and opposite angles about the observation direction results in two 3-D phase-change volumes, the sum of which gives the out-of-plane-sensitive phase volume and the difference between which gives the in-plane phase volume. From these phase-change volumes the in-plane and out-of-plane depth-resolved displacement fields are obtained. The theoretical framework for the technique is outlined and results from proof-of-principle experiments involving a semitransparent beam undergoing bending are presented.

As an alternative to correlation-based techniques widely used in conventional speckle metrology, we propose a new technique that makes use of phase singularities in the complex analytic signal of a speckle pattern as indicators of local speckle displacements. The complex analytic signal is generated by vortex filtering the speckle pattern. Experimental results are presented that demonstrate the validity and the performance of the proposed optical vortex metrology with nano-scale resolution.

Based on the fringe formation in the k-vector space, we proposed an angular spectrum scanning technique for absolute interferometry. Instead of sweeping the optical frequency over a wide range of spectrum, we tune the angular spectrum by changing the incident angle of a monochromatic plane wave with a spatial light modulator (SLM). In the experiment, we built an equivalent spatially incoherent "ring source" to realize the angular spectrum scanning, and applied an algorithm to compensate the offset fluctuation of the fringe intensity.

In this study, a novel optical interferometric technique called 'statistical interferometry'^1-3 has been developed. In contrast to the conventional interferometry where the phase is determined in a completely deterministic way, we consider the interference of completely random wave fronts, i.e., speckle fields, and it has been proved that the complete randomness of the speckle field can play the role of a standard phase in a statistical sense. The advantage of the method is that since the phase of the object under testing can be derived in a statistical way, the accuracy of the measurement depends only on the number of data taken to calculate a probability density distribution of speckle phase. This feature permits a simple optical system to achieve measurements with an extremely high accuracy. According to a computer simulation, the accuracy of λ/1000 can be achieved using 40,000 data of the speckle intensity. Statistical interferometry was applied to monitor biological activity or growth rate of plant, aiming to investigate the influence of the environmental pollutions. In the experiments, the plants were exposed to Ozone that is the main substance of photochemical smog, and the growth rates were measured before and after the exposure. It was clearly observed that the fluctuation of growth rate as well as its mean rate was dramatically affected by the exposure of ozone. By the observation of growth rate of plant with the accuracy of sub-nanometer scale and a time scale of second, it was newly revealed that the fluctuation of the growth rate reflects the biological activity of the plant.

Transient and asymmetric density distributions have been investigated by a digital speckle tomography with a novel integration method. Multiple CCD images captured movements of speckles in three angles of view simultaneously because the flows were asymmetric and unsteady. The speckle movements which have been formed by a ground glass between no flow and downward butane flow from an elliptical nozzle have been calculated by a cross-correlation tracking method so that those distances can be transferred to deflection angles of laser rays for density gradients. A novel integration method has been developed to obtain projection data from the deflection angles for the speckle tomography. The unsteady density fields have been reconstructed from the accurate projection values by a real-time multiplicative algebraic reconstruction technique (MART) with the developed integration method.

In conventional imaging systems, resolution and depth of field cannot be increased independently. In such systems increased resolution decreases the depth of field (DOF). Hereby we present a novel approach that combines super resolution beyond the classical limit, while extending the DOF simultaneously. It is based on a novel approach proposed by Garcia et al¹⁰, shown to increase the resolution significantly. In their method, the object is multiplied by a moving speckle pattern, and then imaged by a low resolution imaging system. The acquired low resolution image is then electronically multiplied by a spatially synchronized perfect image of the same speckle to provide a high resolution image. In our approach, an object illuminated by a fine speckle pattern may be located anywhere along an extended DOF region. The imaging system cannot resolve the object's finest details, nor the fine speckle pattern. The acquired low resolution image obtained with a moving speckle pattern is electronically multiplied by the same high resolution synchronized moving speckle to finally produce a high resolution image insensitive to aberrations as well as DOF variations. Simulation results are presented.

The recording of the volume speckle field from an object at different planes, combined with the wave propagation equation allows the reconstruction of the wave front phase and amplitude without requiring a reference wave. The main advantage of this single-beam multiple-intensity reconstruction (SBMIR) technique is the simple experimental setup due to the fact that no reference wave is required as it is in the case of holography. In this study the method is applied to the investigations of diffusely transmitting and reflecting objects. The effects of different parameters on the quality of reconstructions were investigated by simulation and experiment. Significant improvements are observed when the number of intensity measurements is 15 or more and the sequential measurement distance is 0.5 mm or larger. Performing two iterations during the reconstruction process using the calculated phase also leads to better reconstructions. The results from simulation and experiments agreed well. Subsequent work has shown that super image methods like shifting the camera a distance of half-pixel in the lateral directions enhance the sampling of speckle patterns and lead to better reconstructions. This allows to the possibility of recording wave fields from larger test objects.

Nowadays, multidimensional Synthetic Aperture Radars are a very promising remote sensing tool, able to retrieve Earth surface information in a quantitative way. Nevertheless, the presence of speckle noise makes this task extremely complex as it prevents a correct estimation of the useful information. This paper presents and validates a noise model permitting to describe the behavior of speckle noise in correlated measurements. Since the model is derived only on the statistical description of the data, it may be exported to other domains apart from Synthetic Aperture Radars.

We explore the specific nature of wave propagation in multiple scattering media and examine how this is revealed in various aspects of the speckle pattern measured at the output surface of an ensemble of disordered media. We present near-field measurements of the speckle pattern transmitted through random samples in a quasi-one dimensional geometry. The microwave field -amplitude and phase- is measured as a function of frequency on a grid of points on the output surface of samples composed of randomly positioned dielectric spheres. The field and intensity correlation functions versus displacement and frequency shift are measured and reveal non-Gaussian behavior, namely long range correlation. The widest fluctuations of the phase derivative with frequency are found at low intensity values near a phase singularity in the transmitted speckle pattern. The position of these phase singularities at which the intensity vanishes is reconstructed for the entire speckle pattern and followed in space while frequency is shifted.

When the speckle pattern is displaced, the displacement vector can be obtained by performing a correlation comparison between the two patterns, either optically or numerically. The so-called speckle photography technique has become an important metrological, strain analysis and fluid mechanics tool. The resolution of speckle technique depends on the size of the speckles employed. For an optical recording system, it is essentially limited to the wavelength of the light used and is about 0.5μm within the visible spectrum. In 1982 Chiang introduced the electron speckle photography concept whereby sub-micron and nanometer speckles were created via a process of physical vapor deposition and recording was made by an electron microscope, either a SEM or a TEM. As a result the resolution of speckle photography was increased by several orders of magnitude. With the advancement of digital speckle techniques the method is now fully automated. This paper discusses the current state art of this technique, and its application to the determination of differential thermal strains in electronic packaging, shear band formation in the lamellar interfaces of TiAl and prediction of the crack growth, the size effect of MEMS material SU-8, the micro-mechanical properties of artificial tissues, and the mechanical properties of metal oxide nanofibers. Also discussed in the paper are potential applications of this technique to nanotechnology and bio mechanics.

When the speckle pattern produced by a scattering surface shows some type of activity, the speckle distribution changes in time. This paper presents a method to locally estimate the spatial variance of the temporal variation of the phase as an activity descriptor in a sequence of dynamic speckle. This method is based on the computation of the spatial autocorrelation of the speckle intensity using a sliding window. The image obtained from the resulting spatial variance matrix reveals areas of the sample with different speckle activity. Results obtained for both simulated and experimental data are also shown.

Results of the researches directed on the further development of dynamic speckle - interfeometry are considered. Application of the spectral analysis of speckle dynamics for investigation of irreversible processes in metals and in models of cells of living systems is discussed. Use of an interference of two speckle - fields for contactless measurement of velocity of ultrasonic waves in metals is analyzed. The compact speckle - holographic installation created for demonstration of methods of dynamic speckle - interfeometry and training of students is discussed.

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.

Electronic speckle pattern shearing interferometry (ESPSI), also known as digital shearography, is a hole-field non-destructive, optical technique used to measure approximately the field of displacement derivatives. The accurate measurements of these derivatives have several problems one of them is that of ESPSI results are approximately equal to the derivatives, they are equal to the derivatives only if the shear distance tends to zero, hence, if experimental data rendered by ESPSI are taken directly as equal to the derivatives, the measurements may carry an important shearing error. Other error, ESPSI yields values relative to a reference value at a specific location of the field that can be very difficult to determine accurately. In this paper, we propose a general procedure to compensate the shearing error and to introduce the reference by adding two quantities to the values rendered by ESPSI. As an example, we measured a displacement derivative field induced on a metallic sheet specimen by applying tensile load.

Phase stepping algorithms are mostly based on three or more interferograms that can either be acquired sequentially, involving some temporal phase stepping mechanism, or in parallel. When a phase step is applied between acquisitions, object phase changes may cause phase errors when calculating phase. A new system that allows the object to change in between arbitrary temporal phase steps is proposed. It comprises a relatively simple polarization based two-channel speckle interferometer that acquires two π/2 phase stepped interferograms simultaneously with a single camera. This quadrature pair is phase stepped with a temporal phase stepping system that is also polarization based. Simulations and experimental results are presented that illustrate the improvements achieved with quadrature phase stepping compared to results obtained with the two-channel speckle interferometer operated without additional temporal phase stepping.

Shearography is a double-exposure speckle interferometry technique that is sensitive to the displacement gradient, a parameter closely related to the surface strain. For a statically loaded object double-exposure may be extended by phase-stepping to yield a wrapped phase map, which after further processing gives the displacement gradient field. For a dynamically loaded object this technique is not suitable because the phase is not stationary during the phase-stepping process. The other commonly used technique for phase analysis is based on the introduction of either a spatial or temporal carrier frequency. A temporal carrier is more suited to shearography as a spatial carrier is both difficult to implement experimentally and the optical differentiation can amplify distortions in the carrier fringes. Temporal phase unwrapping and Fourier transform based approaches have previously been used to process sequences of temporal interferograms in speckle interferometry. In this work an out-of-plane displacement gradient sensitive shearography configuration is used. The temporal phase-stepping is performed by moving the reference mirror in the interferometer and Fourier transform based methods are used to analyse the sequence of interferograms. The instrument was applied to the analysis of the displacement gradient variation during a heating and cooling cycle of a composite panel over a time of approximately 10 seconds.

In the first part some principles of the large deformation analysis in holographic Interferometry are briefly outlined. This may also give a link to the second part here. Modifications of the set-up at the reconstruction should recover the previously invisible fringes. The spacing and the contrast of them are characterized by the fringe and visibility vectors. The relevant derivative of the path difference involves the polar decomposition of the deformation gradient into strain and rotation and the image aberration implies further changes of geodesic curvature and of surface curvatures. In the second part these considerations lead then to similar aspects for hypersurfaces, before all to an interpretation by two virtual deformations for the Schwarzschild-solution of the gravitation. That is further usefull for non-spherical gravitational fields, for the invariants there and for the TOV-relation between pressure and density. The null-geodesics or light rays can also be interpreted by these virtual deformations. An approach towards the Kerr-solution for rotating stars is added. As for the linearisation a connection is outlined which confirms the non-existence of gravitational waves.

High-resolution time-averaged interferograms are obtained, in speckle interferometry or in digital holography, by using the orthogonal components of the hologram of the vibrating object and those of the object in a reference position. By using a procedure equivalent to the synchronous detection, one may obtain not only a high-resolution time-averaged fringe pattern but also a quasi-binary interferogram. The two fields are closely related to each other and present the interest of a significant phase noise reduction. In high-resolution time-averaged fringe patterns the center of dark fringes may be obtained with subpixel accuracy. Among the possible applications one is particularly interesting: the estimation of the complete vibration-related phase field, a result equivalent to phase unwrapping. The phase estimation is done solely on the basis of a single fringe pattern, whos fringe locus is the usual Bessel function. It is based on the local inversion of the Bessel function inside each of the different regions where this function is invertible, regions delimited by known phase values, corresponding to the successive extrema and zeros of the Bessel function. The implementation of the method is illustrated with a practical example. The results are discussed and compared with those obtained by stroboscopic digital holography and by reference phase modulation in speckle interferometry. A discussion tries to show the advantages and limitations of the method, as well as possible future developments.

A current problem encountered in holographic interferometry systems is the phase variations that arise from vibrations, from the use of optical fiber in one arm, by air convection or by unwanted movement between the object and the measurement device. The holographic device developed by CSL based on photorefractive BSO crystals has the advantage of high resolution fringes with the capability of self-processing and indefinite reusability. The weakness of the technique is a response time that is often slow compared to external perturbations. For applications outside the laboratory, we decided to find solutions adapted to the holographic camera and which tend to limit or to eliminate the effect of such phase variations. An error signal is measured from one or another technique which measure the phase variations and which counteracts on an active element in the interferometer to stabilize the phase during recording. Different solutions have been analysed and are presented here. Interferograms were obtained with and without implementation of the phase control system that show the interest of such approach. Some of the system presented are only adapted to photorefractive holographic interferometry, making use of some crystal diffraction properties. Other systems can be used with other kind of interferometers.

The feasibility of Real-time Colour Holographic Interferometry (RCHI) has been shown for several years at ONERA to analyze high speed two-dimensional flows. The light source of the interferometer is made of three different wavelengths (one red, one green and one blue) and panchromatic holograms are recorded by transmission. The method has been successfully applied in the ONERA wind tunnel to analyze the two dimensional wake flow around a circular cylinder. High speed interferograms of the unsteady wake flow have been obtained at a high framing rate of 35,000 frames per second. The authors propose to extend this method for analyzing three dimensional flows. In order make that, Real-time Colour Denisyuk Holographic Interferometry (RCDHI) has been developed. The feasibility of the optical setup is shown in one direction sight, the aim being to reproduce the same optical setup along several sight directions, each shifted by a given angle. Contrary to the optical setup developed for the analysis of the 2D flows, in the one proposed for 3D flows, reflection holograms are used. In the case of reflection holograms, the diffraction efficiency is strongly influenced by the variations in the gelatine thickness produced during the holograms treatment. Solutions are proposed to control the gelatine shrinkage and the first results obtained in wind tunnel are shown in one sight of view. High speed interferograms of unsteady wake flow around a circular cylinder have been obtained in narrowed fringes and uniform background at Mach 0.45.

This paper presents the second generation LISE-LI of the fibre-optics Low coherence Interferometric Sensor (LISE), recently developed by FOGALE nanotech. Based on the proven concept of low coherence interferometry, the LISE system works as a comparator of optical group delays. The group delay along the optical axis in the probe interferometer arm containing the object to be measured is compared with the group delay along the optical axis of the reference interferometer arm containing a delay line. The latter consists of a mirror that can be linearly displaced on a translation stage. The light source is a super luminescent diode emitting at a near infrared wavelength (typically 1.31 μm) with a spectral bandwidth of a few tens of nm. Thanks to the limited temporal coherence of the source, multiple surfaces of the object can be detected during a single scan of the delay line. Measurement ranges are between a few mm up to 600 mm (optical thickness). The measurement zone can be placed at a working distance of up to several meters away from the instrument's exit. Applications in industry and in research laboratories include thickness measurements of individual optical elements (e.g. lenses), technical multi-layer glasses, display cover glasses, semiconductor wafers, and position measurements of multiple elements of an optical system (e.g. a photographic lens). Compared to the first generation of the system, the absolute accuracy of the second generation system is about ten times better, reaching a level of ±100 nm for thickness measurements over the full measurement range. Following an introductory description of the measurement principle, the first part of the paper focuses on the key elements in the system design, both in hardware and detection algorithm, that ensure the high accuracy level. The second part of the paper presents an experimental validation of the achieved accuracy level. We present results of thickness measurements on distance pieces made of Zerodur. The measured results demonstrate the absolute accuracy over the measurement range as well as the excellent long-term stability of the system.

We report about a novel optical method based on laser Doppler velocimetry for position and shape measurements of moved solid state surfaces with approximately one micrometer position resolution. 3D shape measurements of a rotating cylinder inside a turning machine as well as tip clearance measurements at a transonic centrifugal compressor performed during operation at 50,000 rpm and 586 m/s blade tip velocity are presented. All results are in good agreement with conventional reference probes. The measurement accuracy of the laser Doppler position sensor is investigated in dependence of the speckle pattern. Furthermore, it is shown that this sensor offers high temporal resolution and high position resolution simultaneously and that shading can be reduced compared to triangulation. Consequently, the presented laser Doppler position sensor opens up new perspectives in the field of real-time manufacturing metrology and process control, for example controlling the turning and the grinding process or for future developments of turbo machines.

The statistical analysis and experimental results of self-mixing speckle interference in the distributed feedback (DFB) laser are presented in this paper. Dynamics solution of output gain variation in the DFB cavity is deduced on the basis of speckle theory and self-mixing interference in the DFB laser, when external optical feedback comes from a moving rough surface. By numeric simulations and experiments, the dynamic output variations of the DFB laser as well as their probability density functions (PDFs) are analyzed. Both results of simulations and experiments are in agreement with each other. The experimental results show that this speckle signal processing can be used to measure velocity of target.

Digital Holographic Microscopy (DHM) is an optical interferometric technique for not destructive testing of micro-electro-mechanical systems (MEMS). A characterization process based on a no-contact technique allows us to analyze deformations, warping, residual stress, cracks and more other defects of MEMS, without destroy them. The flexibility of this technique allows us to improve novel numerical reconstruction algorithm for the recovery of more information. The post processing of the acquired holograms allows to reduce noise, optical aberrations, defocusing. In particular, the hologram reconstruction process has been modified to obtain Extended Focus Images (EFI). In Digital holographic microscopy, the use of microscopy objectives with high magnifications, reduces the focus depth. This means that for extended object a single reconstructed image with all the details in focus is not possible to obtain. Using a multiple reconstruction process and opportune resizing algorithms a full focused reconstructed images of extended object has been obtained without any mechanical movement. In particular, the advantages of the EFI technique are unique for dynamical characterization by DHM of extended objects, where the techniques based on multiple acquisitions fail. The EFI technique has been applied to obtain a best focused reconstructed image and profile of some micromechanical systems. It is demonstrated that this new approach allows to improve the accuracy in the EFI image when compared to the previous experimental results. Focusing of zones at different quote has been obtained evidencing, shape, crack and deformation impossible to observe otherwise at the same time. Moreover, these technique of reconstruction and analysis can be advantageous in many other fields of application.

A miniaturized optical system based on spatial filtering for measuring speckle displacement will be discussed with special emphasis on shaping the speckle spectrum in order to enhance the signal. Applications for measuring linear object velocity - being it in one or two dimensions - and for probing angular velocities will be discussed. A miniaturized system has been developed for implementation in a single chip for measuring speckle displacement in two directions. The system is dedicated for cursor control and is in order to reduce cost based on the use of a single Vertical Cavity Surface Emitting Laser (VCSEL), a dedicated single-chip detector and signal processor and a molded polymer optical element performing the necessary optical processing.

Speckle contrast is widely used in various applications. In this work we develop a simple model to examine the influence of optical geometry on contrast reduction for polychromatic speckle the Fresnel diffraction zone. The model is based on the known fact that the sum of N independent speckle patterns decreases the contrast of the resultant pattern. The model shows how to construct zones in such a way that each zone creates an independent speckle. Theoretical grounds and experimental validation are presented. Practical applications of the derived formulae are discussed. The contrast reduction due to geometry is found to be significant for broad light low-coherent beams.

Now, many methods of measuring the external force which acts on a structure have been devised. We developed the method that a stress and a strain could be analyzed in automatic, non-contact, and real time by combining digital image correlation and the intelligent hybrid method. However, it is not easy to evaluate the sub-pixel order displacement with high accuracy in digital image correlation. On the other hand, the displacement in a crack problem is a sub-pixel in many cases. Hence, we examined the algorithm for measuring the infinitesimal deformation and discussed which method raises accuracy. The Newton-Raphson method that takes deformation of the image itself into consideration in deformation analyses was adopted, and the deformation gradient was extended to higher order by Taylor expansion. In order to extend the flexibility of this system, we used steel and an aluminum alloy specimens in the experiment. Then, a stress intensity factor was able to be evaluated less than 1% of the error as compared with FEM.

There have been theoretically analyzed the ways of the formation of the polarization singularities of the biological tissues images of various morphological structures. There have been also experimentally examined the coordinate distributions of a single and doubly degenerated polarization singularities of the physiologically normal and pathologically changed biological tissues.

The methods of increase the protective properties of holographic elements by using hidden image are discussed. The extension of the new method of wave equation solution is useful for providing analytical studying and numerical modeling of diffraction on amplitude-phase discrete mask. Possibilities of its practical application for structured light beam generation and wavefront reconstruction is considered. Conclusions regarding the possibilities of the representation of the arbitrary fields by using the discrete matrix of elementary diffractive aperture cells for an enhancement of the iteration algorithm of hologram synthesis are obtained. The method proposed of computer-generated holograms (CGH) synthesis enables one to synthesize CGH's and to simulate the digital image processing techniques for hidden image coding. The further improvement of this approach of coding amplitude-phase masks for both recording and reading of hidden image by holographic security devices is proposed. By using coding phase mask with quasi-stochastic distribution for diffraction pattern writing as additional structure on the protective hologram are explained. It is shown that computer generated hologram (CGH) can restore spatial structure represented by optical singularities. The conditions of reconstruction of the hidden image are discussed in case of encoding and decoding masks are not coinciding. A structure of a system that looks promising to produce a like hologram and method of operation directly images a pattern, which is previously calculated by computer and displayed on the amplitude-phase mask is explained. The results obtained by numerical and experimental means are accompanied with a discussion about extents of this method.

Many studies to determine the parameters of rough surfaces by optical methods were made. Some of them are related to the problem of surfaces immersed in a liquid, making the assumption of the equivalence between the surface immersed and other surface with an "apparent roughness". This paper deal with this kind of problems making a theoretical study of the light scattered by a very rough reflecting surface, σ >> λ, and the light scattered by the same surface immersed in a liquid of refractive index n. The general Kirchhoff solution for scattering from a rough surface is used. This work shows that under certain conditions the mean scattered intensity from a surface immersed in a liquid can be quasi-indistinguishable from another surface not immersed, called "apparent surface".

A theoretical model describing speckle correlation as a decreasing quadratic exponential function of roughness changes was published in a previous paper. In this work, the theoretical model in a real situation is analyzed: paint drying over rough surfaces with a roughness larger than the wavelength of the He-Ne laser beam used to illuminate it. Speckle correlation of the scattered light is applied to study changes in the system surface-drying paint. A digital algorithm is used to evaluate the correlation of speckles taken while the paint dries. The speckle patterns are captured at different moments of the process, i.e., a first set of pictures when the paint is fresh (first 30 minutes) and another set in a period of several hours. The speckle patterns in the early group were stored every one or two minutes. The speckle correlation is evaluated between the first picture and the others. A graph of correlation vs. time is analyzed using the model and considering that the solvent evaporation follows a decreasing exponential function. The other group is formed by speckle patterns stored every twenty minutes. The speckle patterns are studied as mentioned above and the correlation between one picture and the next is performed as well. That is, the speckle correlation is now evaluated between consecutive patterns. These experimental changes are compared with the theoretical model. Good agreement between the theoretical and experimental results is found.

We present a study of the performance of an incremental optical encoder that works using speckle pattern illumination and a phase grating. The operational principle of the encoder lies in measuring the variations of a speckle pattern passing through the phase grating that can be displaced. This study is described theoretically by a model based on the scalar diffraction theory in the Fresnel zone. The intensity correlation of the modified speckle as a function of the grating displacement is obtained and compared with experimental results. Likewise, the mounting tolerances of the proposed system are analyzed.

It has been recently shown that application of Michelson interferometry, is suitable for monitoring of oxide layers growing in metallic structures during preliminary states of oxidation processes in aqueous solutions, without any physical contact with the sample. The qualitative and quantitative interpretation of the observed interferograms allows evaluation of important physical parameters related to specific corrosion processes [1]. Although the using of aluminum samples with surfaces polished to certain optical quality is a necessary requirement to obtain well-built interferograms, it complicates further applications for diffused surfaces typical of industrial conditions. In this work we present preliminary qualitative results obtained by using a simple experimental setup based on Digital Speckle Pattern Interferometry (DSPI) [2], as a proposal to solve this difficulty and on the other hand, to use the benefits of certain powerful tools like low-coherence optical techniques for further applications on monitoring of corrosion through turbid media.

A new self-mixing interferometer based on sinusoidal phase-modulating technique for micro-displacement reconstruction is presented in this paper. Phase modulation of the laser beam is obtained by an electro-optic modulator (EOM) in the external cavity. Fourier analysis method is proposed to demodulate the phase. The optimum values of the modulation frequency and modulation depth are discussed. Theoretical analysis and simulation results are given. Experimentally, the micro-movement of a high precision commercial PZT has been reconstructed, which can obtain a displacement measurement accuracy of a few nanometers.

Holographical measurement of structures immersed in water may bring a useful contribution to the study of fluid-structures interaction and also to the numerical models of such mechanical components. Among several cases of particular interest, this paper focuses on turbomachinery and plates which are basical elements of transducers and underwater machinery. The paper presents two series of measurements. One concerns a uniform plate, for which eigenfrequencies and eigenmodes are strongly affected by the level of immersion. Experimental results are correlated with those obtained for the numerical model, and allow updating of the model. The second example is that of a propeller. The experimental results made possible the validation of a method for the vibroacoustic analysis of structures having symmetry properties. It represents an extension of the method of the linear representations of finite symmetry groups to problems of coupling fluid-structure. This approach, while keeping the quality of the approximations, leads to a significant reduction of the number of degrees of freedom, with a maximal reduction for the so-called repetitive structures. For the propeller, this approach will allow to model its vibration in immersed state and improve the model by using the interferometric measurements.

The noise of phase distributions is an important parameter for the optimization of holographic and speckle interferometric setups as well as to quantify the measurement accuracy for the determination of optical path length changes. An algorithm for noise quantification of wrapped phase distributions is presented that is based on an enhanced sine-cosine filter with subsequent triangle function transformation. Compared to methods that calculate the standard deviation of raw phase data modulo 2π to smoothed data obtained by spatial filtering with a sine-cosine filter, an enhanced accuracy for noise quantification is achieved that is independent of fringe number and fringe orientation.

Electronic speckle pattern interferometry (ESPI) can provide accurate contour measurements in the micron range and short measurement times far below one second. Typical surfaces in industrial applications, however, often show discontinuities, like steps or holes. An unambiguous measurement of such surfaces is possible, if the synthetic wavelength is chosen larger than the largest surface step. A long synthetic wavelength, however, introduces a high noise level such that an unambiguous measurement combined with a high accuracy is not possible in any case. Our preferred solution for this problem is the combination of two or more synthetic wavelengths. In contrast to other publications (hierarchical, pixel-wise approach) our area-based approach uses only two synthetic wavelengths minimizing measurement time and device complexity. In this paper we present different methods for merging the phase images of the two synthetic wavelengths into one measurement result combining accuracy and unambiguousness.

In paint and ink industries, no commercial instruments can perform non-intrusive monitoring of the drying process. We propose here an optical instrument, called HORUS(R), that monitors the drying process of any product deposited on any substrate by analyzing micro-structure movement of the product. Most of drying processes have in common that this movement becomes slower with time. On the basis of the "multi-speckle diffusing wave spectroscopy" (MSDWS) technique, we propose here a simple and robust algorithm called ASII for "adaptive speckle imaging interferometry", able to detect in real time the micro-structure agitation by plotting what we call "speckle rate" (SR) as a function of time. We show the hardware configuration and 3 typical experiments made with HORUS(R) film formation analyser.

We propose novel technique for z-distance measurement to an optically rough surface using dynamic speckles. The technique is based on the continuous frequency measurements of the power modulation of the spatially filtered scattered light. The dynamic speckle pattern is created when the laser beam scans the surface under study. We use an acousto-optical deflector to perform scanning the surface. Acousto-optical deflector provides the surface scanning at very high speed up to 500 m/s. Therefore, by using spatial filtering technique of dynamic speckle, the distance to the object surface can be measured within extremely small time window, less than 100 ns. The proposed technique can be very useful for monitoring the surface profile and/or vibrations of the fast moving or fast rotating surfaces in various industrial applications.

For erosion/redeposition measurement in tokamaks, an optical method based on digital speckle pattern interferometry is in development at CEA Cadarache. In order to preserve high spatial resolution, the temporal phase shifting method is used. However, this technique is sensitive to vibrations, which decreases the phase map quality. In this paper, we propose two techniques of phase calculation in presence of vibrations.

As an alternative to profilometry, speckle techniques are investigated to characterize pavement microtexture in case of a subjective speckle whose grains are not resolved by the recording system. In view of the lack of information available regarding the application of speckle techniques to multi-scale surfaces and considering the particular experimental configuration we selected, some simulations of the speckle contrast are carried out using the scalar diffraction theory of Kirchhoff in case of a two-scale surface texture. We study the relative influence of each scale characteristics. Subsequently, specklegram recording and processing are designed to take into account the characteristics of pavement surfaces. Tests are carried out with some reference surfaces without macrotexture and with some models of pavement surfaces. We show that we can achieve to discriminate the reference surfaces and, under some conditions, the models of pavement surfaces by recording several specklegrams and by analyzing the contrast value distribution.

There are several algorithms for quantitative and qualitative characterization of dynamic speckle. In this paper, the statistical method named R.O.C (Receiver Operating Characteristic) is used to compare some speckle algorithms. We estimate the capacity of these descriptors in the discrimination of different activities.

We report on the errors obtained by comparing the in- and out-of-plane displacements calculated from the sensitivity matrix with all its components and when it is considered only the component of the largest contributing of each one of the three interferometers. Divergent illumination is considered in the sensitivity vectors evaluation to measure displacement vector components. This analysis is made for a flat elastic target by using of Electronic Speckle Pattern Interferometry (ESPI).

Dynamic speckle images are useful tools to characterize the activity of biological tissues. In this paper, this technique was applied to determine chemotaxis responses of Pseudomonas aeruginosa towards attractants. Generalized weighted differences, wavelet entropy and spectral bands decomposition algorithms were used to characterize the speckle activity. Experimental results show regions with different bacterial activity. Dynamic speckle method exhibits a good performance for this application.

The results of experimental study of fluctuations of a coherent field intensity during hardening of concrete are presented. It has been shown that square time derivative of fluctuations of a scattered field intensity are connected with base stages of cement hydratation.

This paper represents the results of investigating the Lyapunov's a maximal index and the autocorrelation function half-width of optical radiation intensity scattered by nematic liquid crystal during phase transition liquid - liquid crystal and liquid crystal - liquid from crystal thickness. It has been shown that chaos in the scattered field increases with the growth of plate thickness of liquid crystal.

Dynamic speckle or biospeckle is a phenomenon generated by laser light scattering in biological tissues. It is also present in some industrial processes where the surfaces exhibit some kind of activity. There are several methods to characterize the dynamic speckle pattern activity. For quantitative measurements, the Inertia Moment of the co occurrence matrix of the temporal history of the speckle pattern (THSP) is usually used. In this work we propose the use of average dimensions (AD) for quantitative classifications of textures of THSP images corresponding to different stages of the sample. The AD method was tested in an experiment with the drying of paint, a non biological phenomenon that we usually use as dynamic speckle initial test. We have chosen this phenomenon because its activity can be followed in a relatively simple way by gravimetric measures and because its behaviour is rather predictable. Also, the AD was applied to numerically simulated THSP images and the performance was compared with other quantitative method. Experiments with biological samples are currently under development.

We describe a dual-interferometric setup for simultaneous and independent measurement of the thermal expansion coefficient and thermo-optic coefficients in ferroelectric crystals (LiNbO₃ and KTiOPO₄). The crystal temperature varies from room temperature up to 200°C by an actively stabilized oven. The thermal expansion coefficient is determined using a moire interferometer and monitoring, as a function of the temperature, the period of a grating written on one side of the crystal sample. The thermo-optic coefficients of the ordinary and extraordinary axes of LiNbO₃ crystal are estimated by measuring the optical path variation measured using a Mach-Zehnder interferometer.

The aim of this paper is to investigate the mechanical properties of a PVC foam core and especially the Young modulus profile along a commercialised 50 mm beam thickness. The identification of the Young modulus gradient is realized through the uniaxial compression test of a 50 mm cube sample. The in-plane strain fields of one cube face under loading in both directions (longitudinal and transversal) are achieved using a diffuse light interferometric technique, the speckle interferometry. Next to that, a numerical model is built using finite elements code CAST3M. We choose a multilayer model in order to introduce spatial variation of the mechanical properties. The boundaries conditions are very close to those prescribed in the experimental tests. Finally, the present work shows that the non uniform profile of the Young modulus can be estimated by using a simple inverse method and the finite elements analysis to reproduce the experimental strain field.

In recent years, the fractal theory has been applied to a wide variety of scientific problems. However, this approach has not been used to study dynamic processes through the analysis of temporal sequences of speckle patterns. In this work we present a study of the dynamic speckle phenomenon based on the multifractal theory. This study is carried out by calculating the Hausdorff dimension of the set of singularities of the Holder exponent. These parameters are determined from the maxima of the wavelet transform modulus of the scattered light intensity along the time axis, for each pixel of the sequence of speckle images. Calculations conducted on experimental data evidence a multifractal structure in the case of a fast drying paint and a bruised fruit. We extend this result by using a synthetic model, which reproduces quite well the first and second spatial statistics of the speckle intensity as well as the correlation coefficient evaluated from a temporal sequence of speckle patterns.

Localization of plastic strain has been studied by measuring strain and strain rate during tensile test¹. Pictures were continuously recorded during the experiment and in-plane Electronic Speckle Pattern Interferometry (ESPI) pictures were generated afterwards, by subtracting couples of images. A square grid of 3 mm separation was drawn on the specimen to determine the true stress-true strain curve, while fringe patterns gave an access to relative displacements. Strain, average strain and strain rate were deduced. An uncertainty evaluation on these parameters was carried out applying the so-called law of propagation of uncertainties (ISO 07-020²).

Strain measurement techniques should be valid, accurate and reliable in order for the results obtained to be used. Digital Speckle Photogrammetry (DSP) is proving to be a very useful technique for examining, in laboratory conditions, the distribution of strain about cracks and other faults in stressed specimens. The DSP method has good potential for use in monitoring parts of electrical power station plants, blades of wind turbine power generators and for other monitoring requirements. On the other hand, there are many installation problems to be overcome. For example, there is the need to have regard for the hostile environment in steam generating plants and the demanding weather conditions to which wind turbine blades are subjected. A significant advantage of the Digital Speckle Photogrammetry technique is the fact that the collection of outputs from individual DSP sensors for continuous remote monitoring is possible. However, DSP measurements can also be useful each time a plant is shut down. This is to complement data from existing monitoring methods that are used at present time.

This paper revisits defocused speckle correlation as a tool for measuring the response in metal sheets during percussion laser drilling processing. For the processing the 4th harmonic Nd:YAG wavelength (266 nm) was used in pulsed mode. It is shown that the method provides a cost efficient and robust alternative to speckle interferometry for the study of the small deformations that appear during laser processing. The accuracy was shown to be in the order of a few tens of μrads for the tilt component being measured which translates to a few nm in deflection when being spatially integrated. In the measurements deflections up to 50 nm was detected on the backside of silver and a copper sheet, respectively.

Knowledge of how osseous structures and implants behave under deforming stress is an interesting point when evaluating the response of an implanted prosthesis. The failure of an implant is not always due to the great stress a structure may be subjected to at a particular moment, but rather to the effects of deterioration associated with lesser stress but which is continuously applied. Therefore it is helpful to know how bones and implants respond to this lesser stress. Digital speckle interferometry (DSPI) is suitable for this type of determination, as it is a highly sensitive, non-invasive optical technique. In this study we present the results we obtained when determining the elasticity of a sample of a macerated human radius, a titanium implant and a titanium screw used to treat the fractures of this bone. The correlation ratios we obtained in determining Young's modulus were in the order of r=0.994. Models were made of these structures using the finite elements method (FEM) with the aid of the ANSYS 10.0 program, applying Young's modulus values determined by DSPI. With a view to monitoring the accuracy of the FEM models of the bone and the implant elements we designed a flexion experiment to obtain the DSPI values in and out of plane. The high degree of concordance between the results of both methods makes it possible to continue studying osseous samples with a fixed implant, and also other implants made of different alloys.

The detailed theoretical and experimental investigations of the self-reconstruction of the structure of Bessel beams in various scattering media, including biological tissue, have been carried out. Also the self- reconstruction of Bessel beam after shadowing with single obstacle is studied. Using conical beams, the peculiarities of speckle contrast imaging of subsurface targets embedded into highly scattering media have been investigated.

In this paper, we present a new approach of the speckle phenomenon. This method is based on the fractal Brownian motion theory and allows the extraction of three stochastic parameters to characterize the speckle pattern. For the first time, we present the results of this method applied to the discrimination of the healthy vs. pathologic skin. We also demonstrate, in case of the scleroderma, than this method is more accurate than the classical frequential approach.

We present an evaluation method of the hologram multiplexed recording using 3-dimensional computer simulation analysis. The collinear and off-axis type speckle-shift hologram recording are studied from the view point of SNR and bit error rate.

The present study is based on the use of electronical speckle pattern shearing interferometry (ESPSI) on a double lap joint, the joined parts being two steel blocks and two composite plates. ESPSI is used to investigate de strain maps close to the end of the bonding in the center part of the specimen. The ESPSI set-up allows to get the full field strain and slope maps of a given surface. Its architecture is based on optical fibres which gives a portable assembly that can be used in a civil/mechanical engineering laboratory. This presentation emphases the advantages of such a method and its performances. Last some results are given and compared to an analytical approach.

Self-mixing interference in DFB-LD for fiber sensing application has been analyzed in this paper. Due to the characteristics of good model and narrow spectrum, the DFB-LD has the application potentiality in the filed of self-mixing interference, and optical communication technique has rapidly driven the development of optical fiber sensing technique. The combination of self-mixing interference technique and optical fiber sensing technique can satisfy the request of microminiaturized sensing device and the demand of interrogation of optical fiber. It is possible to form a novel optical fiber sensing measurement network, and the combination is helpful to the application at the aspects of avigation, industrial automation, medical examination, etc. In this work, based on the theory of coupled wave, the variation of laser output caused by self-mixing interference has been presented. For optical fiber sensing application, the self-mixing interference under the condition of transmitting the external optical signal by fiber has been analyzed. The influence from the variation of attenuation caused by the increment of fiber length and the reflectivity of the remote target to the output signal of self-mixing interference has been discussed in numerical simulation.

We analyze the relation between the coherence properties of scattered light fields and various geometric parameters of the scattering objects. It is shown that if the coherence time τ_c of the probing radiation exceeds 3/ω₀, with ω₀ being the central frequency of the radiation spectrum, then the correlation properties of the scattered, field speckle pattern averaged over a time T>10τ_c determine the homogeneity domains and the coherence properties of the scattered fields. These domains and coherence properties are determined by the following parameters: the coherence length of the probing radiation L_c=τ_cc, where c is the speed of light; the transverse size d and the depth L_s of the backscattering domain; the distance r_c between the receiving aperture and the scattering surface, the size d_p of the receiving aperture, the central wavelength of the probing radiation λ=c/ω₀, and the mean square deviation σ of the surface roughness height distribution. The obtained results enable one to find the relations between the parameters L_s, L_c, and σ corresponding to various intervals of the coherence length variation, where the scattered field manifests itself as coherent, partially coherent, and incoherent. The smallest possible coherence length of the probing optical radiation is estimated to be 8λ.

In this work, a new micro-extensometric technique to study the local heterogeneities of strain fields in metallic alloys is introduced. It is based on the optical full-field measurement method called the grid method adapted to the micrometric scale. In the first part of the paper, the making of a periodic grating at the surface of the sample by direct interferometric photolithography is explained. The optimization of the grids in terms of phase noise is then addressed.

Far field light scattering from rough surfaces and inhomogeneous bulks has extensively been studied these last decades, with a major application in random media characterization. Angular Resolved measurements are performed and investigated thanks to the development of electromagnetic models. The studies are extended to the case of high angular resolution, that's mean to the speckle pattern. We show that the analysis of the polarization state of the scattered field permits to complete this study and to identify signatures of the different polarization sources which are surfaces or bulks. An application will then be to annul each scattering source in order to select the characterized element.

This paper addresses the interferometric measurements performed on PLANCK Secondary reflector-Flight Model (SRFM) during the cryo-optical test at the Centre Spatial de Liege in Belgium. It was requested to measure the changes of the surface figure error (SFE) with respect to the best ellipsoid, between 293 K and 50 K, with a 1 μm RMS accuracy. To achieve this, Infra Red interferometry has been selected and a dedicated thermo mechanical set-up has been constructed. One emphasizes on the solutions adopted to cope with high surface slopes appearing at cryogenic temperature. Indeed, detector resolution has been exploited to resolve high density fringes at the expense of the aperture. A stitching procedure has been implemented to reconstruct the full aperture measurement with success. Test results are presented.

The use of a pulsed twin-cavity laser allows to study transient events and fast phenomena, like the ultrasonic surface acoustic waves that are the object of our interest. However, slight differences between the output beams can lead to a systematic phase mismatch that yields a broad fringe pattern (even in the absence of any phase change due to the measurand) which can hinder the detection and measurement of waves of very low amplitude. We profit from the fact that this mismatch changes slowly to propose an enhancement of the original TV holography technique to remove most of this undesired effect. For each measurement we record in fast sequence four primary correlograms. The first two (one with each cavity) are taken with the object at rest; the other couple records two mechanical states of the excited surface. Each primary correlogram is recorded with an off-axis configuration of the reference beam, which allows to recover its phase by applying the spatial Fourier transform method. The optical phase-difference calculated from the first pair of primary correlograms represents the phase mismatch between laser beams, and can be subtracted from the optical phase-difference map that carries the information of interest. The whole process is implemented in a single step by using complex arithmetic.

It is reported for the first time the use of a high speed camera in digital holography with an out of plane sensitivity. The camera takes the image plane holograms of a cw laser illuminated rectangular framed polyester material at a rate of 5000 per second, that is a spacing of 200 microseconds between holograms, and 512 by 500 pixels at 10 bit resolution. The freely standing object has a random movement due to non controlled environmental air currents. As is usual with this technique each digital hologram is Fourier processed in order to obtain upon comparison with a consecutive digital hologram the phase map of the displacement. High quality results showing the amplitude and direction of the random movement are presented.

Laser speckle based methods for measuring strain within specimen have been devised by several authors using a wide variety of optical arrangements.^1-3 Almost all of the proposed methods aim at measuring strain over an extended baselength given, in case of the laser speckle strain gauge⁴ by the distance at the specimens surface of two impinging beams of laser light that is usually on the order of 5 mm to 50 mm. Others reported on encouraging results using a set-up employing a single illuminated spot at the specimens surface.^{1, 5} Still the extend the mechanical strain is averaged over is given by the beam diameter which using HeNe lasers is somewhat limited to approximately 1 mm. In this proposed paper we report on the development and application of a laser speckle shift strain sensor that employs a laser beam focussed down to only several tens of micrometers thus allowing a very localized strain reading.⁵ Although as is known from the fourier optical analysis the average speckle size is inversely proportional to the spot diameter and directly proportional to the projection distance by miniaturizing the sensor a true microscopic strain gauge can be devised. Thus some problems in material physics can by addressed, like measuring strain - mostly caused by thermal imbalance - within an extended micro chip, or measuring mechanical strain within thin fibres or foils, or determining strain caused by the mismatch of thermal expansion coefficients between a copper substrate and AgSn solder in electronic circuits, where averaging the strain reading over extended strain fields would definitely underestimate true mechanical (over-) loads that could lead to catastrophic failures.

In the present paper efficiency of adaptive correction is analyzed in the turbulent atmosphere and under the conditions of thermal blooming. A numerical model of a typical adaptive optics system was developed to carry out the investigations. As it is known, phase conjugation and multidither, i.e., the algorithms commonly employed to correct for thermal and turbulent distortions of laser beams are unstable in nonlinear medium. We demonstrated that stability of phase control is possible to increase introducing the modifications of the algorithms. Also we demonstrated that phase compensation does not insure complete correction for thermal or turbulent aberrations induced by an atmospheric layer. To correct for aberrations under these conditions it is possible to employ amplitude-phase control over the beam, for example, to use the wavefront reversal algorithm. Realization of the algorithm is possible in a two-mirror adaptive system in which the control over beam phase is performed in two planes at the access to the medium. In numerical experiments it was shown that the two-mirror system insures the absolute compensation for a thin turbulent layer placed at arbitrary distance from the aperture of a laser source and high effectiveness of compensation for distributed lens comparing with phase-only algorithms.

This paper describes the use of a speckle correlation method for measurement of object velocity. A basic concept of the measurement method is presented briefly. Relations valid for propagation of speckle fields in the image field between the speckle motion and the object displacement are mentioned. An experimental arrangement for the measurement of in plane object velocity including its possible measurement resolution and accuracy is analyzed. Obtained experimental results are shown, too.

Diffusing Wave Spectroscopy (DWS) consists in the measurement of temporal correlation of the electromagnetic field in the diffusion regime, allowing a scan of dynamical properties deep inside a medium. DWS is of special interest in biomedical optics, as it is sensitive to blood circulation in capillaries inside the tissue. However one main difficulty of this technique concerns data extraction which implies to perform an inverse problem taking into account the geometry and the optical coefficients of the medium. The use of time-resolved detection has been proved to be an efficient tool to discriminate the DWS information, but the photon path lengths were up to now limited to a few tens mean free paths. In order to perform time-resolved DWS for much longer photon paths, we used a new method, based on the use of an interferometer and a wavelength modulated source. We have already demonstrated that this method, in addition to its lower cost, was very efficient to perform time-resolved measurements of the light scattered by a thick scattering medium. We will show in this poster some measurements performed by transillumination through a thick medium (4cm), opening the possibility of Time-Resolved DWS measurements in the human breast.

In the present report the possibility of singular points detections using a Shack-Hartmann sensor is described and the precision of the developed detection algorithm is estimated. Also the algorithms of a singular wave front reconstruction are analyzed. Two algorithms are considered and their properties compared. One of them was developed by D. Fried, its description was found in literature. The second algorithm was developed by authors of the report. The both algorithms were introduced into the software of the sensor and insured satisfactory quality of singular phase reconstruction. The precision of algorithms compared in numerical investigations as well in real laboratory experiments.

NIMO is a new measurement tool based on the Phase-Shifting Schlieren technique [1]. The technique combines the Schlieren principle with the phase-shifting technique generally used in interferometry. By an adequate Schlieren filter and an adapted set-up, some Schlieren Fringes coding light beam deviation angles are generated. After the application of the phase shift technique, the Schlieren phase is calculated and converted in beam deviation values. The technique has been validated on conventional optical element ranging from millimetre to decimetre scales. NIMO opens a new step in metrology in a wide industrial range in both reflection and transmission (e.g. optical manufacturing, glass industry, ophthalmic industry,...). In [2],we focused on fluid physics applications and the implementation of the technique in a microscope for MEMS measurements. In [3], we described an adapted setup in which all the phase shifted images are acquired simultaneously opening the possibility to measure dynamic phenomena with NIMO. This paper is focused on the instrument recently developed for ophthalmic industry. The performances of the instrument are given and industrial applications in free-form and aspherical surfaces metrology are demonstrated.

The characterisation of composite plates used in structural work in the field of aeronautics is approached by associating ultrasound and speckle interferometry measurements. The reduced thickness of the specimens does not allow for gauge instrumentation to measure out-of plane deformation. A system was therefore used which makes it possible to obtain the cartography of the deformations in and out of-plane. This paper describes an application of electronic speckle interferometry in the measurement through thickness deformation in composites.

Project MegaJoule is a large facility devoted to laser fusion, for the assessment of nuclear physics simulations. It is now under construction by CEA/DAM and is planned to be operative around 2008. In this facility, 240 laser beams of square cross-section (400 mm x 400 mm) will deliver 1.8 MJ on a deuterium-tritium target within a 2.5 ns pulse. The requirements on the optical elements in the laser path are very stringent: the controls of flat elements need to detect the best fit sphere with a resolution equivalent to a deviation to flatness of 10 nm at the center of the 400 mm x 400 mm area. Also, the deviation of slopes should be evaluated with a resolution of 0.1 mrad and a spatial resolution of 10 mm. The components are to be tested in vertical position, and the measurements should be absolute (i.e. no reference plane of ideal flatness is available). We propose a non interferometric technique that should be able to meet this requirement. The idea is to control the magnifying effect of the component using deflectometry and spatial phase-shifting. We present here the basic theory and first measurements showing the feasability of the system.

Biomineralization is intensively studied at present due to its importance in the formation of bones, teeth, cartilage, etc. Hydroxyapatite is one of the most common natural biomaterials and the primary structural component of bones and teeth. We have grown bio-like hydroxyapatite layers in-vitro on stainless steel, silicon and silica glass by using a biomimetic approach (immersion in a supersaturated aqueous solution resembling the ion composition of human blood plasma). Using classical techniques such as stylus profiling, AFM or SEM, it was found difficult, destructive or time-consuming to measure the topography, thickness and profile of the heterogeneous, thick and rough hydroxyapatite layers. White light scanning interferometry, on the other hand, has been found to be particularly useful for analyzing such bio-like layers, requiring no sample preparation and being rapid and non-destructive. The results have shown a typical layer thickness of up to 20 μm and a rms roughness of 4 μm. The hydroxyapatite presents nonetheless a challenge for this technique because of its semi-translucence, high roughness and the presence of cavities within its volume. This results in varying qualities of fringe pattern depending on the area, ranging from classical fringes on smooth surfaces, to complex speckle-like fringes on rough surfaces, to multiple fringe signals along the optical axis in the presence of buried layers. In certain configurations this can affect the measurement precision. In this paper we present the latest results for optimizing the measurement conditions in order to reduce such errors and to provide additional useful information concerning the layer.

The basic convolution integral, Uf = Uo crossed circle h 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.

The holographic camera developed by CSL was aimed at observing of medium to large opaque scattering objects. In the recent times, we received an increasing demand of measurement on small objects (a few centimetres wide) or micrometric systems (MEMS). In the last case, most of them are specular objects ranging to a few microns. The imaging and illumination systems of our holographic device was naturally not adapted to such new objects. Therefore we decided to study a new optical extension to the current system which matches these new needs. Nevertheless the type of displacement that can be measured remain similar to the ones covered by the previous system. We present various examples of applications brought by industrial partners.