This PDF file contains the front matter associated with SPIE Proceedings Volume 8413, including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

Speckle can be modeled by analysis of the statistics of the image of a phase object such as a rough surface. The image can be calculated using the coherent transfer function of the imaging system and the angular spectrum representation. This approach gives a three-dimensional image, and includes the effects of high numerical aperture and the finite depth of the structure. Different correlation coefficients can be assumed, including fractal distributions, such as exponential correlation, as well as Gaussian correlation.

In isotropic random optical waves, each dark area may contain optical vortices or phase singularities. In this paper, we experimentally generate a speckle pattern and observe its transition along the propagation direction. Experimental results show that the vortex density changes along the propagation direction when the continuous phase part of the speckle field is removed with a spatial light modulator. The contrast ratio of the spackle field also changes due to the transition of the field. Such a transition can be interpreted to a certain extent by the self-annihilation of vortex dipoles due to the least-squares phase removal.

There have two ways to observe speckle, free space and image space. We introduced the factors impact speckle contrast in a speckle characterization system and established an equivalent relation between image space speckle characterization and free space speckle characterization, validating the equivalent relation through experiments. The experimental results show that if the equivalent relation come into existence, the speckle contrast measured in image space match well with it in free space. At last we have discussed the speckle in a projection system with a rough surface inside and given the compound speckle measuring method.

Ratio between a time spectrum of differences of phases of the scattered waves and a time spectrum of speckle brightness is theoretically established. Three experiments in which the difference of phases of waves changed by moving of a rough glass plate, by fatigue of metal, and by the activity of a monolayer of cells are considered. The good agreement of the theory and experiment is received.

The objective of this paper is to discuss the properties and a few applications of multi-spectral speckles. The paper starts with a theoretical section where the correlation properties of multi-spectral speckles are detailed for the case of reflective imaging geometry. Both a free-space geometry and an imaging geometry are detailed. As an application example effects and possibilities provided by the theory in a measurement of surface shape of a generally shaped object from a dual-wavelength holographic recording are detailed. It is showed that the same phase profile is obtained from integration of speckle movements and phase unwrapping and they are therefore exchangeable quantities.

Displacement of speckles arising from a curved surface subject to displacement or deformation is investigated by numerical simulations using a rough surface model that is represented by an assembly of point scatterers distributed around its mean surface. Speckle displacement in the diffraction field of an object illuminated by a narrow laser beam is derived from the peak position of the cross-correlation function between the 2-dimensional intensity signals recorded by a CCD before and after object deformation or displacement. The evaluated speckle displacement is compared with with those obtained from analytical approach for a flat mean surface. It has been shown that they agree well with each other. Then speckle displacement from a spherical surface is evaluated to indicate some differences in displacement sensitivities from a plane. This simulation can be applied to surface shape and roughness, and recording specifications.

The accuracy of image correlation algorithms is severely affected by errors introduced by the interpolation step. This article surveys some of the most common interpolating and approximating kernels, focusing on the various sources of error-signal attenuation, phase errors and frequency spectrum-to identify the best performing algorithms. The results of the analysis are experimentally validated by comparing the Digital Image Correlation estimated displacements with the interferometric estimated values.

One of the major accident scenarios in industrial safety deals with liquid pool evaporation consequent to a tank rupture. Numerous previous studies have been performed and several correlations are available in the literature. It appears that all of the correlations are strongly dependent on wind velocity but have nevertheless been all created under a boundary layer flow above the pool. However, industrial safety bunds do not allow such a profile because of obstacles and so cavity flows may occur. For such a configuration, is it then possible to describe the evaporation phenomena thanks to correlations in the literature? Experiments involving evaporation under this configuration have thus been performed in this work. Particular care is devoted to the wind profile measurement as the wind velocity is one of the main parameters. Digital speckle correlation insures high accuracy and good spatial resolution. We used a double pulse YAG laser (200mJ, 15Hz at 532 nm) with a high resolution double frame camera (2048 pixel x 2048 pixels, 15Hz). The experiments involve 200 liters (200L) of liquid (acetone and water) in a 58 cm diameter pool. The pool is located in the wind tunnel facility. The study presents 2 different wind velocities (2m.s^-1 and 4m.s^-1) and four different dike step heights (0 cm, 3 cm, 6 cm and 10 cm). Displacement vector maps are obtained after adaptative correlation and related processing. The final results are also crossed with IR measurements and open new fields of investigation that will be discussed.

We present novel experimental method for estimation of the light penetration depth (LPD) in turbid media based on the analysis of the cross-correlation function of speckle patterns. Under certain illumination conditions, the amplitude of the correlation function is strongly dependent on the penetration depth. Presented theoretical model based on the Bragg diffraction from the thick holograms allows LPD estimation if only one parameter of the material, namely refractive index, of the material is known. However, qualitative LPD comparison is possible without knowledge of the material properties. Feasibility of the method was checked experimentally. Experimental results were additionally verified by alternative experimental method.

High resolution spatial light modulators (SLM) have been used in many different ways during the last years. Regarding speckle interferometry, different applications can be realized by integrating SLMs in interferometric setup. In this work the influence of a liquid crystal based phase-only SLM on the measurement quality concerning deformation and shape measurement using two wavelengths is discussed.

This paper extends Digital Speckle Pattern Interferometry into three dimensions. A Wavelength Scanning Interferometry (WSI) system is proposed which provides displacement fields inside the volume of semi-transparent scattering materials with high spatial resolution and three-dimensional displacement sensitivity. The main driver to develop such a system is the need to determine constitutive parameters (mainly elastic constants) of materials such as polymers and biological tissues so that their behavior can be modeled computationally. The sample is illuminated by three non-coplanar collimated beams around the observation direction. Sequences of two-dimensional interferograms are recorded while the frequency of the laser is tuned at a constant rate. Each pixel thus records and intensity signal which temporal frequency encodes the optical path difference between the illumination and reference beams for a particular point on the sample. Fourier transformation along the time axis reconstructs the magnitude and phase of the material's microstructure. Different optical paths along each illumination direction are required in order to separate or multiplex, in the frequency domain, the signals corresponding to each sensitivity vector. In this way, all the information required to reconstruct the location and the 3D displacement vector of scattering points within the volume in the material is recorded simultaneously. A controlled validation experiment is performed, which confirms the ability of the technique to provide three dimensional displacement distributions inside semitransparent scattering materials.

Compensation or comparative measurement is a natural way to overcome the limited measuring range of TV holography or digital holography. In this case the resultant displacement field is the difference of the actual deformation and a known deformation pattern. The compensation can be digital, because these measuring techniques operate with images recorded with digital camera. Development of Spatial Light Modulators (SLM) enables the application of active holographic optical elements in coherent optical metrology. These modulators are capable to reconstruct digital holograms optically; therefore they can be used as active holographic optical elements. The goal of the project was to perform adaptive comparative measurements, where an optically reconstructed image of a recorded or simulated single or double exposure hologram is used for holographic illumination of another object. In this paper conventional TV holographic or digital holographic arrangement with holographic object illumination applied for comparative displacement measurement with adaptive features. Measurement setups were built, containing devices performing feedback, which is capable to project the real image of the master object - using its previously recorded or computer simulated digital holograms - onto the test object to calculate the difference deformation directly.

Electronic speckle pattern interferometry is a useful deformation measurement method. In this paper, new speckle interferometry that can measure the deformation with a concave shape distribution based on spatial fringe analysis method by using only two speckle patterns is proposed. The optical system that can record some spatial information into each speckle of speckle pattern is set up by using basic characteristics of speckle phenomenon that has never been used before. In experimental results, it is confirmed that the out-of-plane deformation measurement by using only two speckle patterns before and after the deformation can be precisely performed by this method.

The measurement of surface profile is a vital quality control procedure in many industries. For small objects (dimensions below ~10 mm) with rough or discontinuous surfaces, scanning white light interferometry (SWLI) is currently the method of choice. However, with a resolution of ~1 nm, vibration during the scan induces motion artifacts and prevents its routine use on the production line. We present a system that avoids temporal scanning by spectrally splitting the white light interferogram into a set of interferograms at different wavenumbers which are recorded simultaneously on an image sensor. The system essentially consists of an interferometer coupled to a single-shot hyperspectral imaging system. Fourier transformation along the wavenumber axis provides an absolute optical path difference for each point in the field of view, a procedure which is robust even on optically rough surfaces. Height maps with a spatial resolution of 19×19 pixels and a measurement accuracy of ~460 nm are demonstrated.

The idea of remote and virtual metrology has been reported already in 2000 with a conceptual illustration by use of comparative digital holography, aimed at the comparison of two nominally identical but physically different objects, e.g., master and sample, in industrial inspection processes. However, the concept of remote and virtual metrology can be extended far beyond this. For example, it does not only allow for the transmission of static holograms over the Internet, but also provides an opportunity to communicate with and eventually control the physical set-up of a remote metrology system. Furthermore, the metrology system can be modeled in the environment of a 3D virtual reality using CAD or similar technology, providing a more intuitive interface to the physical setup within the virtual world. An engineer or scientist who would like to access the remote real world system can log on to the virtual system, moving and manipulating the setup through an avatar and take the desired measurements. The real metrology system responds to the interaction between the avatar and the 3D virtual representation, providing a more intuitive interface to the physical setup within the virtual world. The measurement data are stored and interpreted automatically for appropriate display within the virtual world, providing the necessary feedback to the experimenter. Such a system opens up many novel opportunities in industrial inspection such as the remote master-sample-comparison and the virtual assembling of parts that are fabricated at different places. Moreover, a multitude of new techniques can be envisaged. To them belong modern ways for documenting, efficient methods for metadata storage, the possibility for remote reviewing of experimental results, the adding of real experiments to publications by providing remote access to the metadata and to the experimental setup via Internet, the presentation of complex experiments in classrooms and lecture halls, the sharing of expensive and complex infrastructure within international collaborations, the implementation of new ways for the remote test of new devices, for their maintenance and service, and many more. The paper describes the idea of remote laboratories and illustrates the potential of the approach on selected examples with special attention to optical metrology.

This paper proposes a theoretical and experimental analysis of the saturation effect in digital Fresnel holography and generalizes the linear image formulation to the case of the non linear pixel saturation.

Optical information of linearly polarized light recorded on a photoinduced birefringent medium was clearly expressed using an optical anisotropy matrix in the circular polarization basis. The theoretical expression was related to the principle of retardagraphy, that is, an optical recording technique for the retardance pattern of an optical anisotropic object. Furthermore, the polarization holographic characteristics were explained by the principle. As a demonstration of optical information recording, a retardance pattern displayed on a parallel aligned liquid crystal spatial light modulator was recorded on an azobenzene copolymer film, and the retardance pattern was reconstructed by imaging polarimetry. The transmission axis of a polarizer in the imaging polarimetric system was adjusted using a homogeneous pattern.

Lensless object scanning holography (LOSH) has been recently proposed as a fully lensless method, capable of improving image quality in reflective digital Fourier holography, and involving an extremely simplified experimental setup. LOSH is based on the recording and post-processing of a set of digital lensless holograms which finally yields in a synthetic image with improved resolution, field of view (FOV), signal-to-noise ratio (SNR), and depth of field (DOF). LOSH validation has been previously validated for one-dimensional (1D) objects and now it is expanded to twodimensional (2D) ones. Experimental results are presented showing an impressive image quality improvement.

Holography is a 3D imaging method. In digital holography, like classical holography, speckle noise presents in reconstruction process and reduces the image quality. Thus, speckle noise reduction has strong effect on the image quality. Because of random distribution of speckle characteristics, it is too hard to eliminate them completely. Up to now some methods have been proposed for speckle noise reduction. In this work a method has been presented which is based on statistical property of speckle noise. By averaging multiple reconstructed images with different speckle noise patterns it has been reduced. These reconstructed images have been acquired by changing the sampling size in the hologram plane.

A novel efficient variational technique for speckle imaging is discussed. It is developed with the main motivation to filter noise, to wipe out the typical diffraction artifacts and to achieve crisp imaging. A sparse modeling is used for the wave field at the object plane in order to overcome the loss of information due to the ill-posedness of forward propagation image formation operators. This flexible and data adaptive modeling relies on the recent progress in sparse imaging and compressive sensing (CS). Being in line with the general formalism of CS, we develop an original approach to wave field reconstruction.⁷ In this paper we demonstrate this technique in its application for computational amplitude ghost imaging (GI), where a spatial light modulator (SLM) is used in order to generate a speckle wave field sensing a transmitted mask object.

This paper introduces ptychography, a novel and very exciting phase retrieval technique, to the field of optical metrology. Its working principle is explained and a useful application in combination with the dual wavelength method for topography measurement is presented. Advantages of the dual wavelength method compared to other optical topography measurement techniques, the experimental procedure and the analysis of the data are discussed.

Using data sets recorded from a speckle interferometer with in-plane sensitivity, we compare the performance of a recently proposed temporal phase evaluation technique based on the three-dimensional directional wavelet transform with the one given by the one-dimensional Fourier transform method. The obtained results are compared for different phase distributions, and the advantages and limitations of both temporal phase recovery approaches are also discussed.

We present a method to recover the complex amplitude of speckle fields from measurements performed by a shear interferometer. In contrast to the state of the art, it requires only two measurements with the orientation of the shears selected to be orthogonal to each other, while the respective magnitudes correspond to a unit camera pixel. The evaluation comprises an iterative local optimization procedure using the steepest descent gradient algorithm in combination with an heuristic initial guess. The algorithm finds a local minimum least squares solution even in the presence of branch points and camera noise. To demonstrate the approach, light scattered by a diffuser is investigated. The results are shown to agree well with those obtained from a standard interferometric technique.

We present a fast and robust approach to phase shift registration from randomly phase shifted interferograms. The approach is based on a singular value decomposition followed by an iterative, projection based optimization procedure. Compared to known algorithms it is fast and shows comparable or better registration quality depending on the case of application.

In digital holography, phases carry the 3D information of objects. However, phase mapping is ambiguous, as the extracted phase turns into a form that suffers from 2π phase jumps. In this case the phase data must be unwrapped to fit for use. For this reason, we developed a new phase unwrapping algorithm that is applicable to digital hologram maps. The proposed algorithm has been evaluated and compared with past phase unwrapping methods by using simulated and real phase data. Results show that the proposed method gives satisfactory unwrapped results with low computation time.

Recent technological advances of miniaturization engineering are enabling the realization of components and systems with unprecedented capabilities. Such capabilities, which are significantly beneficial to scientific and engineering applications, are impacting the development and the application of optical metrology systems for investigations under complex boundary, loading, and operating conditions. In this paper, and overview of metrology systems that we are developing is presented. Systems are being developed and applied to high-speed and high-resolution measurements of shape and deformations under actual operating conditions for such applications as sustainability, health, medical diagnosis, security, and urban infrastructure. Systems take advantage of recent developments in light sources and modulators, detectors, microelectromechanical (MEMS) sensors and actuators, kinematic positioners, rapid prototyping fabrication technologies, as well as software engineering.

For holography and speckle interferometry the calibration of the sensitivity is a must, because illumination and observation directions vary across the field of view. A numerical estimate or a static calibration using rigid body motions is standard, and reference materials exist for static strain calibration. Recently, reference materials for the dynamic calibration of optical instruments of displacement and strain measurement were designed and prototypes were manufactured in the European FP7 project ADVISE. We review the properties of the reference material and the concept of traceability for the field of displacement values by using a calibrated single point transducer. The mode shape is assessed using out-of-plane DSPI, Finite Element Analysis as well as analytic solutions of the plate vibration. We present measurements using stroboscopic DSPI on the reference material under acoustic excitation and compare the measured mode shapes to the ones predicted by FE analysis. We apply different comparison methodologies based on point-by-point deviations and on decomposition of the mode shapes into a set of orthogonal basis functions. The latter method is well suited to assess stability and reproducibility of a mode shape. Finally, the deviations are used to estimate the reference material uncertainty which is an essential parameter for determining the calibration uncertainty. Uncertainty contributions of the DSPI set-up are taken into account. To conclude, the application area and limitations of the reference material are discussed.

This paper presents an experimental analysis so as to compare digital Fresnel holography and digital image-plane holography. Particularly, the influence of the aperture and lens in the case of image-plane holography is exhibited. Optimal filtering and image recovering conditions are thus established.

Ninety percent of the Global Movement of Goods transit by ship. The transportation of HNS (Hazardous and Noxious Substances) in bulk highly increases with the tanker traffic. The huge volume capacities induce a major risk of accident involving chemicals. Among the latest accidents, many have led to vessels sinking (Ievoli Sun, 2000 - ECE, 2006). In case of floating substances, liquid release in depth entails an ascending two phase flow. The visualization of that flow is complex. Indeed, liquid chemicals have mostly a refractive index close to water, causing difficulties for the assessment of the two phase medium behavior. Several physics aspects are points of interest: droplets characterization (shape evolution and velocity), dissolution kinetics and hydrodynamic vortices. Previous works, presented in the 2010 Speckle conference in Brazil, employed Dynamic Speckle Interferometry to study Methyl Ethyl Ketone (MEK) dissolution in a 15 cm high and 1 cm thick water column. This paper deals with experiments achieved with the Cedre Experimental Column (CEC - 5 m high and 0.8 m in diameter). As the water thickness has been increased, Dynamic Speckle Interferometry results are improved by shadowscopic measurements. A laser diode is used to generate parallel light while high speed imaging records the products rising. Two measurements systems are placed at the bottom and the top of the CEC. The chemical class of pollutant like floaters, dissolvers (plume, trails or droplets) has been then identified. Physics of the two phase flow is presented and shows up the dependence on chemicals properties such as interfacial tension, viscosity and density. Furthermore, parallel light propagation through this disturbed medium has revealed trailing edges vortices for some substances (e.g. butanol) presenting low refractive index changes.

Laser Speckle Photometry (LSP) is a newly developed contactless, fast and completely optical nondestructive testing method based on the detection and analysis of thermally or mechanically activated characteristic speckle dynamics. The heat propagation or tension process causes locally different degrees of thermal/mechanical expansion, which generates local and time-dependent strain fields, resulting in a local displacement of material surface. During this process, the normal surface slope and absolute height of the microscopic and mesoscopic surface segments, especially at rough sample surfaces, is transformed. These spatiotemporal changes include information about the material structure and conditions. Therefore, the proposed measurement technique includes a pulsed heating source for sample activation, a temperature detection of the sample at the measurement location in a distance from the heading point, a continuous wave laser for sample irradiation and activation of speckle patterns at the measurement point, and in addition, a fast CCD camera for the detection of the speckle movement during heat propagation at the measurement location. Laser Speckle Photometry can be used for evaluating material properties, such as hardness and porosity. The approach is based on the estimation of the "Speckle Thermal Diffusivity" parameter K, that can be determined using the thermal diffusion equation and the modified correlation function from the pixel intensity of the speckle image variations during thermal activation. After testing, the correlation between parameter K and hardness, and porosity respectively, was found. Furthermore, mechanical material stress changes, also at elevated operating temperatures, can be estimated by the presented technique using the calculated parameter K. In this case, the thermal excitation will be partially replaced by mechanical activation, such as the tension process. The technique of LSP and the results of calibration experiments are presented in this paper.

Digital Speckle Pattern Interferometry is applied to analyze surface corrosion processes in a metal sample immersed in a corrosive solution. This work describes the analysis process and the problems that can appear due to changes in the liquid solution. It has been performed a detailed analysis of the optical measurements to obtain a 2D visualization of the surface changes and an evaluation of the influence of the index refraction changes in the evaluation of the corrosion effects.

Pulsed TV-holography (PTVH) can be used for obtaining two-dimensional maps of instantaneous out-of-plane displacements in plates. In particular, our group has demonstrated that scattering patterns generated by the interaction of elastic waves with defects can be measured with PTVH and employed for quantitative characterization of damage in non-destructive inspection in plate structures. Recently, we have succeeded in obtaining a quantitative description of experimental scattering patterns produced by holes in harmonic regime using a finite element method (FEM) applied to a two-dimensional model based on the scalar wave equation, avoiding the standard and more complex vector approach based on the rigorous linear elasticity theory. In this work, a similar scheme is employed to characterize equivalent scattering phenomena but in transient regime. Simulated propagation and scattering patterns are tried with the scalar FEM and the corresponding experimental propagation and interaction of Rayleigh-Lamb waves with artificial defects in plates are measured using our specifically developed PTVH system. On this basis, a comparison between experimental maps and FEM simulated maps is developed.

This paper presents a portable device to essentially measure residual stress fields outside the optical bench. This system combines the hole drilling technique with Digital Speckle Pattern Interferometry (DSPI). The novel feature of this device is its high degree of compaction since only one base supports simultaneously the measurement module and the holedrilling device. A new version of the ASTM E837 standard for the measurement of residual stresses has been improved including the computation method for non-uniform residual stresses. According to this standard, a hole with depth of 1.0 mm should be introduced into the material to assess the stress distribution. The discretization of the stress distribution along the hole depth is performed in 20 equal steps of 0.05 mm, getting the deformations generated for stress relief in every drilling step. A description of the compact device showing the solution for a fast and easy interchanging process between modules is performed in this paper. The proposed system is used to evaluate the residual stress distribution into a sample with a rod welded by friction hydro pillar processing (FHPP).

This paper proposes a three-color holographic interferometer devoted to the deformation analysis of a composite material submitted to a short beam shear test. The simultaneous recording of three laser wavelengths using a triple CCD sensor results in the evaluation of shear strains at the lateral surface of the sample. Such an evaluation provides a pertinent parameter to detect premature crack in the structure, long before it becomes visible on the real time stress/strain curve, or with a classical microscope.

Risk sciences involve increasingly optics applications to perform accurate analysis of critical behavior such as failures, explosions, fires. In this particular context, different area sizes are investigated under high temporal sampling rate up to 10000fps. With the improvement of light sources and optical sensors, it is now possible to cope with high spatial resolution even for time resolved measurement. The paper deals with the study of the interaction between overpressure waves, occurring in case of explosion for example, with a liquid droplet present in the vicinity of the overpressure wave. This is a typical scenario encountered in case of industrial breakdown including liquid leakage and explosions. We designed an experimental setup for the evaluation of the interaction between the overpressure wave and falling liquid droplets. A gas chamber is filled with nitrogen until breakage of the outlet rupture disk at about 4 bar. The droplets fall is controlled by an automatic syringe injector placed in the overpressure wave. The imaging system is based on laser shadowscopy. The laser source is a double cavity 15mJ- 1000Hz Nd YLF laser emitting double pulses of about 10ns at 527nm. To record the double pulse after crossing the falling droplets, the transmitted light is captured by a lasersynchronized double frame camera. Since these measurements are time-synchronized, it is then possible to know accurately the different parameters of the phenomenon, such as overpressure wave velocity, droplets diameter, and Reynolds number. Different experiments have been carried out at about 4000 doubleframe/s. The paper presents the whole experiment, the enhancements of the setup and the results for different liquid products from water to acetone.

In this paper we propose novel method possessing high fidelity and versatility for surface defect detection based on the spatially filtered dynamic speckles. It is shown that resolution of proposed method depends on the geometrical parameters of the optical system. The feasibility of the novel method for surface defect detection is demonstrated by experimental results which are in good agreement with theoretical estimations.

The use of Electronic Speckle Pattern Interferometry (ESPI) is well documented in the literature as a non-destructive technique for structural diagnostics in the field of cultural heritage.. In the case of mural paintings the lack of adhesion between the plaster and the mural support is one of the most important risk factors that threaten their conservation. With this non-invasive method it is possible to detect detachments and cracks in the paintings before they become visible The objective of this work is the development of ESPI portable equipment based on a fibre interferometer for in situ qualitative analysis of mural paintings. The novelty of the presented set up is the use of a variable ratio coupler which makes the system more immune to vibrations and allows for better use of available light compared with the equivalent of free air guided. This configuration simplifies the arrangement and makes it possible to obtain ESPI interferograms with high contrast; moreover, the use of a ceramic heater as excitation source enables the analysis during the heating. Preliminary results obtained in laboratory conditions have shown that detachments and cracks can be successfully detected on model samples of the wall paintings.

The damage and stress conditions of large industrial components have to be tested continuously. Especially welding processes in the field of coal production demand a nondestructive monitoring of internal stresses under an external load. In a first step, a new optical method, Laser Speckle Photometry was used during laboratory welding experiments under tensile and bending loads at high strength construction steels. Laser Speckle Photometry is a fast and contactless method for measuring spatial-temporal dynamics of speckle field with high temporal resolution after local heat excitation. The thermally induced change in the material structure causes changes in the speckle-field, which is formed by a probing laser. The shift of the speckle-field is analyzed by statistical methods, using correlation functions. The result of processing is the two-dimensional distribution of thermal diffusivity coefficient correlated to porosity, materials strain or hardness [1-3]. Here, the results of the welding experiments under load are presented. It is shown, that the Laser Speckle Photometry is a suitable technique for nondestructive monitoring and characterization of internal material stresses under external load.

Today, video cameras connected to frame grabbers or video capture cards (VCCs) are used in many applications such as traffic control, surveillance, medical systems or machine vision. In this work, we present a method for determining the spatial-frequency response of VCCs. This method is based on the modulation transfer function (MTF) determination from speckle patterns using a low-cost experimental setup. We have evaluated and compared three different VCCs. The three VCCs produce an amplification (boost) in the horizontal MTF in a different spatial-frequency range, also differing in the maximum amplification value.

In recent years, the flat-panel display (FPD) technology has undergone great development. Currently, FPDs are present in many devices. A significant element in FPD manufacturing is the display front surface. Manufacturers sell FPDs with different types of front surface which can be matte (also called anti-glare) or glossy screens. Users who prefer glossy screens consider images shown in these types of displays to have more vivid colours compared with matte-screen displays. However, external light sources may cause unpleasant reflections on the glossy screens. These reflections can be reduced by a matte treatment in the front surface of FPDs. In this work, we present a method to characterize the front surface of FPDs using laser speckle patterns. We characterized three FPDs: a Samsung XL2370 LCD monitor of 23" with matte screen, a Toshiba Satellite A100 laptop of 15.4" with glossy screen, and a Papyre electronic book reader. The results show great differences in speckle contrast values for the three screens characterized and, therefore, this work shows the feasibility of this method for characterizing and comparing FPDs which have different types of front surfaces.

We present an approach to inspect carbon reinforced plastic components which is based on phase retrieval using a liquid crystal spatial light modulator (SLM). The SLM is located in the Fourier domain of a 4f-imaging system and is used to modulate the incident light with the transfer function of propagation. This configuration allows for the recording of consecutive intensity measurements, with the wave field scattered by the investigated object in various propagation states across a common recording plane. In contrast to existing phase retrieval approaches, the measuring time is considerably reduced, since the switching time of the SLM is less than 50ms. This enables non-destructive testing under thermal load. Experimental results are presented which demonstrate that the approach can be used to assess structural properties of technical components made from carbon reinforced plastics.

In this paper we present a new approach for thermal lens analysis using a two-wavelength DSPI (Digital Speckle Pattern Interferometry) setup for wavefront sensing. The employed geometry enables the sensor to detect wavefronts with small phase differences and inherent aberrations found in induced lenses. The wavefronts was reconstructed by four-stepping fringe evaluation and branch-cut unwrapping from fringes formed onto a diffusive glass. Real-time single-exposure contour interferograms could be obtained in order to get discernible and low-spacial frequency contour fringes and obtain low-noise measurements. In our experiments we studied the thermal lens effect in a 4% Er-doped CaO-Al₂O₃ glass sample. The diode lasers were tuned to have a contour interval of around 120 μm. The incident pump power was longitudinally and collinearly oriented with the probe beams. Each interferogram described a spherical-like wavefront. Using the ABCD matrix formalism we obtained the induced lens dioptric power from the thermal effect for different values of absorbed pump power.

Most of the current optical non-invasive methodologies used to characterize the tympanic membrane (TM) motion generate data in the z direction only, i.e., employ an out-of-plane sensitive configuration. In this paper, 3-D digital holographic interferometry (3-D DHI), is used to measure micrometer displacements from the TM surface. The proposed optical configuration provides information from three sensitivity vectors that separate the contributions from x, y and z displacement components. In order to achieve high accuracy of the sensitivity vector and to obtain the complete determination of the 3-D TM displacements, its surface contour is obtained by moving only two object illumination sources chosen from any pair within the DHI optical setup. Results are presented from measurements corresponding to individual displacements maps for the three orthogonal displacements components x, y and z combined with the TM shape from an ex-vivo cat. These results will no doubt contribute to enhance the understanding and determinate the mechanical properties of this complex tissue.

In this work a new application of digital holography for the study of cardio vascular diseases is proposed. The simultaneous measurement of the blood flow velocity and the vein wall deformation can be obtained by combining digital holography and endoscopy. Endoscopes are used for the illumination and recording of digital holograms inside a vein model. Two different endoscopes have been used in different vein models in order to test the technique performance. Preliminary results of flow velocity and wall deformation are presented.

The use of implants to rehabilitation of total edentulous, partial edentulous or single tooth is increasing, it is due to the high rate of success that this type of treatment present. The objective of this study was to analyze the mechanical behavior of different positions of two dental implants in a rehabilitation of 4 teeth in the region of maxilla anterior. The groups studied were divided according the positioning of the implants. The Group 1: Internal Hexagonal implant in position of lateral incisors and pontic in region of central incisors; Group 2: Internal Hexagonal implant in position of central incisors and cantilever of the lateral incisors and Group3 - : Internal Hexagonal implants alternate with suspended elements. The Electronic Speckle Pattern Interferometry (ESPI) technique was selected for the mechanical evaluation of the 3 groups performance. The results are shown in interferometric phase maps representing the displacement field of the prosthetic structure.

We are developing an experimental setup to characterize dynamic scattering in presence of static scattering. We attempt to retrieve the flow parameters like fluid concentration and velocity in presence of phantoms providing static scattering mimicking the characteristics of skin. Our measurement relies on an optimally-designed optical setup coupled to a high speed detector and the use of appropriate light sources. The flow of particles causes a time varying effect on the speckle pattern which can be measured quantitatively by the speckle contrast term. The speckle contrast is defined as the ratio of standard deviation and mean intensity of speckle variation. Depending on the concentration and velocity of moving particles, the speckle pattern will decorrelate and this results in a drop in the contrast which can also be seen in the recorded images as blurring of the speckle pattern. In literature, measured contrast is related to the velocity and the concentration of the scatterers as it plays a major role in the speckle correlation time (ιc). In our experimental setup we attempt to recover the properties of the moving scatterers in presence of static scatterers. In parallel we present experimental simulations of our experiment comparing it with theoretical studies describing dynamic speckle in presence of static scatterers.

The use of dynamic speckle laser, also called biospeckle laser (BSL), presents a series of challenges to its adoption, as it is the case for its use in real time, and when ones desires to adjust the experimental setup. The technical analysis of the BSL adopted in real time has reduced spatial resolution of the captured image, while the adjustment of preparing an experiment still demands the trial of a specialist. In this work two approaches have been proposed to improve the efficiency of BSL real-time adjustments to support the experimental setup. The use of the method known as Motion History Image (MHI) was carry out over a series of BSL images. The MHI was the basis for the implementation of a graphical interface for real-time identification of areas of activity, and then delimiting the regions of interest. The results showed that the MHI was effective in the reproduction of the activities of speckle patterns in real time without reducing image resolution, and as an instrument for delimit of regions of activity, supporting the analyst in the choice of lighting adjustments and image assembling.

Biospeckle or dynamic laser speckle is a phenomenon developed when a dynamic process occurs in a material under laser illumination. This phenomenon contains considerable information related to both biological and non-biological activity of the material under study. As a non-invasive, non-destructive and low cost technique, biospeckle laser (BSL) has been an outstanding tool for monitoring biological properties. Thus, its application in optical instrumentation has grown over the years, especially in the areas of biology, medicine and agriculture. High sensitivity of biospeckle laser (BSL) technique and variability of biological material combined with the large number of variables involved in speckle pattern formation have brought great challenges to the search for safer, more robust analysis techniques. Therefore, this study aimed to develop and refine methodologies for the BSL analysis and tested alternative protocols for the prime analysis. Particularly, we present a protocol to obtain requirements before the main analysis, in an attempt to eliminate image quality based on subjectivism or research experience. This protocol was based on the creation of requirements to achieve the best speckle patterns such as evaluating the saturation, the homogeneity and the contrast of the grains. The alternative protocol offered a testing approach before the main experiment to increase the certainty to get image and data in an accepted quality, avoiding the loose of time and samples in analysis of a row of a questionable data. The tests were performed in well-known BSL data and presented as a feasible step before the main experiments.

Our study is based on using a non-invasive technique, the bio-speckle technique, in order to follow the ripening of fruits during different stages: before and after the climacteric stage. To assess the impact of the ripening of fruits on their optical properties, speckle grain is measured and the variation of its dimensions is evaluated. In addition, and in order to correlate this observation with the degradation of chlorophylls, both a physical approach based on recording the fluorescence spectrum of chlorophylls, and a biochemical approach based on a pigmentation analysis, are used. We therefore show the efficiency of biospeckle metrology for monitoring fruit maturation.

Electrophoretic mobility and ζ-potential are important physical parameters for the characterization of micro- and nanosystems. In this communication we describe a new method for determining the ζ-potential through the assembly of two well known techniques: free electrophoresis and Dynamic Speckle. When coherent light passes through a fluid having scattering centres, the far field interference originates a speckled image. If the scattering centres are contained within the cylindrical electrophoresis cell of a ZetaMeter and are forced to move in an orderly way under the action of an external electric field, the time variation of the light intensity in the far field speckle images follows a temporal autocorrelation function g(τ). The corresponding correlation time can then be obtained and related with the velocity, from which the electrophoretic mobility and the ζ-potential of the scattering centres can be determined. We have applied this method to microparticles, like natural air-floated silica and two classes of bioceramics, hydroxyapatite and biphasic calcium phosphate. For comparison, we analysed the same samples in parallel using a commercial Zetasizer Nano from Malvern Instruments. The values of ζ-potential determined using the two techniques were the same within ~3% error. These results validate our new method as a useful and efficient alternative for ζ-potential determination of particles, at least within the micrometer scale.

The treatment of fresh fruits with different doses of ionizing radiation has been found effective for delaying ripening and, in this way, to extend shelf life. This preservation method is likely to produce some functional or constitutive changes in the cellular structure of the fruit. In this work, a test of the effectiveness of fruit irradiation with relatively low doses was performed by using dynamic speckle imaging. Bananas from a same lot were chosen, being a first series of them irradiated with different doses of 0.2, 0.4 and 0.6 kGy (Gy = J/kg) and a second series with doses of 0.2, 0.4, 0.6 and 1 kGy. Non irradiated bananas (0 kGy) were considered as the lot reference for contrast. Irradiation was carried out at the Semi-Industrial Cobalt 60 facility of the Ezeiza Atomic Center, with an activity of 6 × 10⁵ Curie and a dose rate of 28.5 Gy/min. The objective of this work is to analyze differences in the maturation process between irradiated and nonirradiated fruits by means of dynamic speckle pattern evaluation.

Switching mode intensity modulation had been applied to the illumination of a LASCA system using multiple exposure times to substitute a variable neutral filter, which allows the variation of the exposure time from frame to frame. In most cases the direct current (DC) control of the laser intensity can lead to changes in the wavelength of regular laser diodes. The use of pulsed mode operation can avoid the mode hopping of the laser light while it offers the tuning of the average intensity in a wide range. While operating the camera at a constant integration time, the length of the exposition was varied from 2 ms to 100 ms by changing the duration of the illuminating laser pulse train. The pulse train was built up of 10 pulses, each having the length of 40 μs with variable separation time. The mode stability of the light source was monitored with a spectrometer, meanwhile speckle images of a static scattering surface were recorded as well. This paper demonstrates the usefulness of this technique in a multi-exposure LASCA system for monitoring the changes in the skin perfusion.

Digital Speckle Shearing Pattern Interferometry (DSSPI) allows to directly quantify deformations in teeth that are subjected to stress. Eighteen second premolars (2PM) were studied both before and after endodontic treatment made with the ProTaper method in order to evaluate the variation of dental elasticity. We present a protocol for determination tooth Apparent Young's Modulus (AYM). Each tooth underwent different flexion loads from 50 to 300 g. DSSPI technique, makes it possible to show the deformation at each point of a line, selected by the researcher, that goes from the attachment point (Point 0) to the root area where the load is applied (Point 300-350, depending on the tooth size). The deformation of each tooth was characterized by the deformation value of point 150, located around the mid-area of tooth. This value was obtained from a linear regression applied on the deformation values of all the points in the fitted line. The correlation coefficients of these fitted regression lines were always higher than 0.972. The elasticity constant of each tooth was obtained as the slope of a new regression line, corresponding to the different loads applied on the tooth versus the corresponding deformation at point 150. This value, divided by the length of the tooth, is the apparent Young's modulus (AYM), which is expressed in arbitrary units (a.u.). Values of the AYM before (4.16 10⁴ a.u) and after endodontic treatment using the ProTaper method (4.30 10⁴ a.u.) showed no statistically significant difference in the elasticity of teeth (p>0.7).

This paper proposes a first attempt to visualize and analyze the vibrations propagating at the surface of a human face's skin induced by a bone conduction device. The proposed method allows the qualitative visualization and quantitative measurement of the surface movements illuminated by a coherent laser beam. To do this, we developed a new approach in a so-called "quasi-time-averaging regime" allowing the retrieval of the vibration amplitude and phase from a sequence of digital Fresnel holograms recorded with a high image rate. The experimental set-up is based on off-axis digital Fresnel holography and a high power continuous wave laser. The sensor is a high speed CMOS camera permitting recordings with a high spatial resolution (1024×1024 pixels) up to 2.4kHz. The set-up is able to provide full field measurements in the frequency bandwidth 100Hz-600Hz. Recording in the quasi-time-averaging regime leaded to the development of a dedicated algorithm able to extract the vibration using only three holograms from the sequence. The design of the algorithm depends on the ratio between exposure time and vibration period. Results exhibit propagation of vibrations at the skin surface, amplitudes being at most at 200nm, and speed velocity can be estimated at each frequency.

A speckle reduction apparatus is proposed by using an optical interferometer to introduce temporally changing interference fringes. With the help of the vibration of a mirror, diverse interference fringes and speckle patterns are added together in the intensity basis during the exposure time of the CCD camera, which result in a summed speckle image having lower speckle contrast. Experimentally, we have demonstrated the speckle reduction efficiency by this method, and compared with another approach by only using the modulation beam. The obtained speckle contrast is 0.66 after using both the modulation beam and the reference beam, which is lower than the 0.77 speckle contrast by only using the modulation beam. We conclude that the introduction of interference fringes helps the speckle reduction.

We investigated the speckle contrast reduction characterization of high power broad-area edge-emitting red and blue laser. The speckle contrast is measured with different pulse driving conditions. It can be observed from the measurement that the speckle contrast reduces with the increasing of pulse duration and pulse amplitude. The highest speckle contrast reduction that can be achieved with the red and the blue lasers is 27.9% and 10.4% respectively. The reduction of speckle contrast is due to the shift of emission wavelength and the incoherence of the laser beam at high driving current.

Inspection of optically rough surfaces in search of defects or other surface features with deterministic reflectance distributions is a subject well suited to optical techniques. We present a device with episcopic coaxial illumination, specifically developed for such kind of inspection tasks, which simultaneously renders both a coherent image and the spatial spectrum of a portion of the surface, precisely defined by the illuminating laser spot. It is based on the wellknown single-lens coherent image processing system, with beamsplitters added to insert the illuminating laser beam and to allow simultaneous access to the Fourier transform and the image planes. The device allows inspecting the speckle signature of surface features in both planes, thus allowing different defect recognition approaches. By selecting the size of the illuminated area of the object or the lens aperture, different speckle sizes can be obtained. If the speckle size is made large enough, identification of individual features can be made on the basis of their particular speckle signatures. Some envisaged applications are the characterization of defects or structures in rough surfaces, the evaluation of speckle statistics in precisely defined zones of surfaces or the identification of authentication marks.

We present a new method of measure of the roughness based on the analysis of the texture of speckle pattern on the surface. Images of speckle pattern over the surface are captured by means of a simple configuration using a laser, beam expander, and a camera charge coupled device (CCD). Using the properties of the normalized covariance function that we obtain from the image of the speckle through the inverse Fourier transform, we relate the values of the normalized covariance function. We compare the results obtained with the results obtained with a confocal microscope. This method can be considered as a noncontact surface profiling method and is easy to implement and can be used during the manufacturing process.

The distribution of the intensity of each speckle depends on the relative phases of modes in the multimode fiber, so they are extremely sensitive to external perturbations of the fiber. These perturbations can locally appear in the fiber without disrupting the entire optical assembly. If the refractive index of the outside medium of the fiber is changed, it can cause variations in the speckle pattern at the fiber output. Thus, by changing the refractive index of the outside medium the speckle pattern at the output fiber varies and its influence can be observed. In this paper we demonstrate the influence of the refractive index of liquids in the speckle pattern obtained by a multimode fiber. In order to obtain greater sensitivity of the experimental measurement, the fiber is bent in a U-shape and immersed in a liquid. The core and cladding are 240 microns and 250 microns, respectively. The intensity speckle field is then captured by a CCD camera in digital image format and processed by the computer with a Matlab program. The portion of fiber exposed to the disturbance of the liquid is located 2 meters before the exit of the fiber. The portion of the fiber in contact with the liquid is curved with a radius of 2 mm.

This paper proposes the characterization of speckle patterns of multimode fibers in view of sensing applications and particularly for detection of vibration or seismic activity. Plastic optical fibers are used in this work due to its excellent flexibility and adaptability to build sensor heads. We are interested in the response to vibration, for which we use a short cylindrical piezoelectric transducer (PZT) vibrating in radial direction. The multimode fiber was coiled as tightly as possible around the mandrel of the PZT and periodic stretching effect was caused by the radial oscillations of the actuator. The PZT is modulated with a frequency generator by applying a sinusoidal signal in the range of 0 to 20 Hz, so the speckle patterns can be time averaged. The fiber extreme is attached to a high speed camera with a plastic adaptor, centering the speckle pattern into the CCD. Maintaining the fiber position, a region of interest is selected to capture the video sequence and it is captured to detect the variations in the speckle pattern. Once having the video sequence, it is processed by averaging the pixel differences between two consecutive frames. This processed sequence is also filtered in order to reduce the high frequency noise component. In this work we report the results of the characterization of 3 types of multimode fibers, with core diameters of 50 μm, 240 μm and 980 μm.

This paper investigates the self-mixing interference in erbium-doped fiber ring laser (FRL) and its application for displacement and velocity sensing. Self-mixing interference in FRL with a parallel dual-channel is proposed. The characteristics of the intensities of the laser in the dual channels with optical feedback are theoretically deduced. The experimental results show a good agreement with the theory, and indicate that self-mixing interference with a parallel dual-channel is an efficient approach for simultaneous multi-channel displacement measurement. Moreover, a new method for velocity detecting based on laser speckle optical feedback injected erbium-doped FRL is presented. Random speckle feedback causes changes in both intensity and frequency of the laser. A dynamic speckled-modulated laser output is observed and processed by FFT analysis. A linear dependant relationship between the velocity of an object and the mean speckle frequency defined as the ratio of the number of fluctuations is obtained, which indicates that speckle optical feedback injected erbium-doped FRL is an effective approach for velocity detecting.

In this paper, the results of using the method of angular spectrum of plane waves as a mathematical model of the iterative algorithm for phase retrieval based on the intensity distributions formed by the radiation of THz frequency range are presented. This mathematical model is designed to calculate the wave field propagation in the near-field diffraction, and in comparison with the Fresnel transform is more effective when working with the THz radiation. The criterion for selection of registration planes which provides the best quality of wave field reconstruction was determined as a result of studying the characteristics of the longitudinal intensity distributions.

Clear coherent imaging through turbid media is a challenging task showing potentialities in the newest applications in microfluidics. If the targets of interest are dipped into turbid fluids, the medium particles act as strong scatterers, resulting in speckle noise and hindering a clear vision by conventional Optics. Conversely, Digital Holography is able to overcome this limit in case of both flowing and quasi-static media. If the liquid flows at sufficient speed into the microfluidic channel, the Doppler effect can be exploited to record the only useful information. In the quasistatic case, a method is proposed to reduce the speckle noise by processing multiple holograms. Experiments have been carried out to show that a clear amplitude and phase-contrast mapping is achievable by speckle reduction while preserving the image resolution.

Foam composites are increasingly used in sandwich structures for ship construction. Typically the foam serves as the core material for a sandwich panel whose face sheets are made of fiber composites. Such a panel is light but strong when loaded transversely. Determining the mechanical properties of a composite foam is not a simple matter in that most traditional methods such as strain gauge or moiré methods are not applicable. However in this paper we show that the mechanical property of foam is a function of the size of the specimen. We apply the digital speckle photography technique to map the deformation of foam composites at different length scales. Emphasis is placed on revealing the composite deformation at microscales. For this we need to use nanosized speckles for the mapping. Nanospeckles are created via a physical vacuum deposition process whereby a metal piece (either gold or copper) is vaporized to fall on the specimen surface. The speckle pattern is digitally recorded at different stages of loading either through a high resolution optical microscope or a scanning electron microscope. The specklegrams are then “compared” using an efficient algorithm using FFT. The result is a full field deformation vector map. We discovered a number of interesting deformation patterns that are unique to the material.