This PDF file contains the Front Matter associated with SPIE Proceedings volume 7387, including the Title page, Copyright information, Table of Contents, Conference Committee listing, and Introduction.

An authentication method using dynamic laser speckle has been investigated to identify scattering objects such as papers or plastic cards. The effects of sampling and quantization of speckle signals on identification performance are examined by using the equal error rate (EER) as a measure of the accuracy of object identification. It is found that a sampling interval of more than the correlation length of speckle fluctuations and a quantization of two or three bits give the lowest EER for data sizes ranging from 100 to 500 bytes.

Optical image encryption technology has attracted a lot of attentions due to its large capacitance and fast speed. In conventional image encryption methods, the random phase masks are used as encryption keys to encode the images into white noise distribution. Therefore, this kind of methods requires interference technology to record complex amplitude and is vulnerable to attack techniques. The image hiding methods which employ the phase retrieve algorithm to encode the images into two or more phase masks are proposed, the hiding process is carried out within a computer using iterative algorithm. But the iterative algorithms are time consumed. All method mentioned above are based on the optical diffraction of the phase masks. In this presentation, a new optical image hiding method based on optical interference is proposed. The coherence lights which pass through two phase masks are combined by a beam splitter. Two beams interfere with each other and the desired image appears at the pre-designed plane. Two phase distribution masks are design analytically; therefore, the hiding speed can be obviously improved. Simulation results are carried out to demonstrate the novelty of the new proposed methods. This method can be expanded for double images hiding.

Phase evaluation based on the spatial Fourier transform of speckle interferograms usually assumes that the side lobes corresponding to the interferential terms in the Fourier spectrum of each interferogram do not overlap the terms related to the intensity of the object and reference beams. If this is not the case, a part the autocorrelation of the object beam is taken along with the selected interference term in the subsequent filtering process and induces an error in the resultant phase map. We present a technique for the acquisition and processing of speckle interferogram sequences that separates the interference lobes from the other spectral terms, even if the aforementioned assumption does not apply. A digital camera records a sequence of temporally phase-shifted interferograms with spatial carrier, and a 3D Fourier transform is applied to this set of spatiotemporal data. In the resultant three-dimensional spectrum, the temporal carrier shifts the central temporal frequency of the interferential terms to high frequencies. This minimizes their overlap with the autocorrelation of the object and reference beams, which are essentially located at low temporal frequencies. The spatial carrier prevents a possible overlap of broadband interferential terms along the temporal frequency axis. A filter that rejects the low temporal frequencies is applied to one of the lobes, and a sequence of complex-valued maps containing the optical phases of the interferograms is obtained. The measurement of surface acoustic waves propagating in a metallic plate, obtained with a double-pulsed TV holography setup, is presented to illustrate the method.

We compare the performance of various recently-developed phase recovery approaches when they are applied in temporal speckle pattern interferometry. The phase retrieval methods to be evaluated are based on the 1D continuous wavelet, the Hilbert-Huang and the S-transforms, and the smooth time-frequency distribution. It is shown that the 3D directional wavelet transform approach outperforms the use of these 1D phase recovery techniques when sets of adjacent non-modulating pixels, modulation loss and noise effects are present in the recorded data.

In Digital holography (DH), an in-line optical setup is commonly employed due to relatively low spatial resolution of CCD camera. In DH, a phase shifting method is commonly employed to determine the complex amplitude on the recording plane. In this study, we propose a phase shift error compensation method based on the statistics of the diffraction field of object. In most cases of the measurement using the digital holography, the object has an optically rough surface, and a fully developed speckle field is produced in the diffraction field, i.e., the recording plane. It is well known that the speckle phase takes a uniform probability density function (PDF). This statistical property is very stable and can be used as a constrain in the determination of actual phase shifts. The experiments were performed, and it was demonstrated that the phase shift error is well compensated over a fairly large amount of phase shift error. This method has a great advantage that any modification on ordinary digital holographic system with the phase shifting method is not required since the method utilizes information that was discarded in the conventional method.

New double FFT convolution algorithms based on the use of spatial spectrum scanning or numerical spherical reconstruction wave allow the full complex amplitude of large objects to be reconstructed. Experimental results in color holography and contact less metrology validate the proposed methods.

In this article we present a novel optical sensor allowing simultaneous measurements of axial displacement and tangential velocity of moving rough solid state objects. The laser Doppler distance sensor with phase coding (P-LDDS) features multiple interference fringe systems which are superposed slightly tilted. The axial displacement of fast laterally moving rough solid state surfaces as well as of purely axial moving objects is determined via phase evaluation. Within a measurement range of 200 μm, the measured maximum systematic displacement error at a laterally moving rough solid state object is 1.4 μm and the displacement resolution is 240 nm. In contrast to conventional measurement techniques, such as triangulation, the displacement uncertainty is independent of the lateral object velocity. This unique feature can be utilized for precise displacement and vibration measurements of high speed objects.

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

We present a simple set-up for digital color holography in which the reference beam has a unique way and the recording uses a stacked photodiode sensor. A dedicated algorithm allows the color object to be reconstructed along each channel. Experimental results confirm the proposed approach.

This paper presents the optical setup of a radial in-plane digital speckle pattern interferometer (DSPI) which uses an axissymmetrical diffractive optical element to obtain double illumination. The application of the DOE gives true in-plane sensitivity that is independent on the wavelength of the laser used as illumination source. Furthermore, it only depends on the grating period of the DOE. A new optical layout was introduced in order to obtain a circular measurement area of about 5 mm in diameter. A brief description of the DOE and the portable strain sensor are presented. A detailed explanation of the clamping system is presented showing its ability to deal with rigid body displacements. Finally, some experimental results are shown enlightening that it is able to measure mechanical stress fields from only one difference phase map.

We have developed a simple digital speckle pattern interferometry (DSPI) and shearography setup to measure the displacement and the corresponding strains of small complex bony structures. We choose both optical techniques because we want to obtain very small deformations (± 20 μm) of small objects (± 1cm). Furthermore full field and in situ measurements are preferred. We first use a Michelson DSPI arrangement with phase shifting. In this way we can obtain the out-of-plane displacements precisely. Second, shearography is introduced to measure the derivative of the out-ofplane displacement. In this way some intrinsic disadvantages of DSPI can be overcome. We have developed these setups to measure the out-of-plane deformations of (small) bird beaks when realistic external forces are applied. In this way, we have a full field validation measurement to which we can compare the outcome of realistic finite element models. The aim is to determine whether the shape, and not only the size, of the bird beaks are optimized to deal with the biting forces that a species encounters. This quantitative analysis will help biologists to investigate if beak morphology is adapted to feeding habits. Applying the method to the famous evolution model of the Darwin's finches will provide scientific proof of functional evolution. In this paper we will present both the DSPI and shearography setup, a comparison of the performance of both techniques on a simple deflection of a cantilever beam and the first results obtained on loaded bird beaks.

New trends in dental prosthodontic interventions tend to preserve the maximum of "body" structure. With the evolution of CAD-CAM techniques, it is now possible to measure "in mouth" the remaining dental tissues. The prosthetic crown is then designed using this shape on which it will be glued on, and also by taking into account the contact surface of the opposite jaw tooth. Several theories discuss on the glue thickness and formulation, but also on the way to evolve to a more biocompatible crown and also new biomechanical concepts. In order to validate these new concepts and materials, and to study the mechanical properties and mechanical integrity of the prosthesis, high resolution optical measurements of the deformations of the glue and the crown are needed. Samples are two intact premolars extracted for orthodontics reasons. The reference sample has no modifications on the tooth while the second sample tooth is shaped to receive a feldspathic ceramic monoblock crown which will be glued. This crown was manufactured with a chairside CAD-CAM system from an intra-oral optical print. The software allows to realize a nearly perfect clone of the reference sample. The necessary space for the glue is also entered with ideal values. This duplication process yields to obtain two samples with identical anatomy for further processing. The glue joint thickness can also be modified if required. The purpose is to compare the behaviour of a natural tooth and its prosthetic clone manufactured with "biomechanical" concepts. Vertical cut samples have been used to deal with planar object observation, and also to look "inside" the tooth. We have developed a complete apparatus enabling the study of the compressive mechanical behaviour of the concerned tooth by speckle interferometry. Because in plane displacements are of great interest for orthodontic measurements¹, an optical fiber in-plane sensitive interferometer has been designed. The fibers are wrapped around piezoelectric transducers to perform "4-buckets" phase shifting leading to phase variations during the compression test. In-plane displacement fields from speckle interferometry already showed very interesting data concerning the mechanical behaviour of teeth: the dentine-enamel junction (DEJ) and the glue junction have been shown including their interfacing function. Mechanical action of the tooth surrounding medium will also be discussed.

The application of an out-of-plane sensitive electronic speckle pattern interferometer (ESPI) using holographic optical element (HOE) to vibration amplitude and phase mapping is reported. The novelty of the proposed system is the use of a speckle reference wave stored in a reflection holographic optical element (HOE). The incorporation of a HOE minimizes the alignment difficulties. The HOE based ESPI system is compact containing only a diode laser, HOE and a digital CMOS camera. The measurement technique is a combination of time averaged ESPI and reference beam phase modulation in an unbalanced interferometer. The reference beam phase modulation is implemented by modulating the drive current of the diode laser. The presented HOE based ESPI system is easy to align and compact and thus suitable for industrial non-destructive testing and vibration analysis.

In the paper the authors present an experimental equipment for elasto-plastic characterization of engineering materials by tensile tests. The stress state is imposed to a dog bone shaped specimen by a testing machine fixed on the optical table and designed for optimizing the performance of a speckle interferometer. All three displacement components are measured by a portable speckle interferometer fed by three laser diodes of 50 mW, by which the deformations of a surface of about 6×8 mm² can be fully analyzed in details. All the equipment is driven by control electronics designed and realized on purpose, by which it is possible to accurately modify the intensity of the illumination sources, the position of a PZT actuator necessary for applying phase-shifting procedure, and the overall displacement applied to the specimen. The experiments were carried out in National Instrument LabVIEW environment, while the processing of the experimental data in Wolfram Mathematica environment. The paper reports the results of the elasto-plastic characterization of a high strength steel specimen.

We have measured the growth of vegetable leaves in real-time by means of digital speckle correlation to detect speckle displacement caused by the growth. We employed two optical configurations, the first for detecting strain component by a pair of CCDs and the second for detecting in-plane translation by a single CCD. We could clearly observe the influence of white light irradiation on the growth rate.

In this contribution we show experimental results for combined thermal and DSPI measurements on several fiber reinforced polymer test samples that have been impacted in a drop tower. Active thermography can give complementary information with regard to the type and size of the damage, but DSPI is used for assessing the effect of the damage, i.e. the difference in the displacement or strain field of a damaged and undamaged specimen.

Phase-shifting shearography is a well-known speckle-interferometric method for remote non-destructive testing. Conventionally, a short, static loading is applied to the test object, and the shearography sensor monitors the displacement field of the object in order to find flaws. However, this method has some limitations: The depth of defects cannot be determined, and in some cases, the signal of a flaw is superposed by a large deformation of the sample itself which makes defect detection difficult. To overcome these drawbacks, the excitation can be performed modulatedly. This generates a thermal wave at the object surface, going along with a modulated object displacement, which can be monitored by a shearography sensor. After the measurement, the local phase and amplitude of the periodical object displacement can be retrieved by a pixelwise discrete Fourier transformation of the recorded stack of fringe images. Since all images are used for evaluation, the signal-to-noise ratio is substantially increased. The displacement of the test object itself is reduced since only the sine-coded object response is extracted by the Fourier transformation. Depth range is adjustable via the modulation frequency. This paper discusses the performance of this technique on model samples and demonstrates the advantages of this approach on modern automotive and aerospace structures.

Composite materials tubes are being used in various industrial segments, including the oil and gas industry¹. The union between adjacent composite tubes is often accomplished through adhesives, and thus the inspection for flaws in adhesive-bonded joints becomes crucial. In this context, tubes and elbows made of epoxy resin reinforced with glass fiber were assembled with adhesive in the Quick-Lock® ¹ configuration forming loops (spools). During the assemblage of these loops, artificial defects (areas without adhesive or disbondings) were inserted in its joints to evaluate the capability of failure detection by shearography. This paper presents and discusses results obtained with shearography. Shearography demonstrated great potential for application in the adhesive-bonded joints inspection, as it detected all defects artificially inserted and also real defects present in the loops joints.

Early detection of defects in concrete structures, such as bridges or dams, is essential to optimize the maintenance of civil engineering facilities. Optical methods constitute non-destructive means of control and measurement but they are generally confined in laboratories where both the setup and environnement are controlled. The method of shearography is especially well adapted to detect damages due to both its capacity to distinctly visualize strain concentration zones and its robustness. The experimental set-up is relatively compact, which enables to examine an extensive surface area by simply moving the shearographic head. In this paper, the application of this methodology for the detection of cracks is presented on concrete samples and circulated outside concrete structures. Due to its sensitivity to strain concentration, shearography is able to detect structural cracks, even when they were not through-cracks. Operational implementation is made on two circulated structures with experts in manual cracks detection. No stimulation device is used. In the first structure, cracks are detected on the bridge deck and on the bridge abutment. In the second structure, cracks on the intrados of the bridge deck are detected and also beginning of cracks which have not been detected by the visual inspection. Different areas are scanned and the results are in agreement with the visual inspection. This technique enables detecting cracks on structures subjected to traffic load. The natural loading of an engineering structure, i.e. the rolling traffic it bears, proves well suited for cracks detection by means of shearography, provided traffic patterns are regular enough.

My memory goes back to my early collage studies that were almost entirely on the scale of "macroworld", as we practiced/perceived it some four decades ago. Since that time things have changed a lot constantly decreasing the scales of interest, at times at rather rapid pace, with monumental advances leading to the scales we work with today and plan for tomorrow. During that change/transition there were "meso" and "micro" developments characterized by changes in scales/sizes of things of interest. Today's scale of interest is "nano" and we are already not only working with "picotechnology", but are even reaching beyond while constantly "planning and projecting" the scales/worlds of the future. Advancement of any technology, especially new emerging ones as we witness/experience them today, is facilitated by the use of all available solution strategies. One of the emerging strategies that affect almost anything currently being developed and/or used, in the today's nanoworld, is based on recent advances of microelectromechanical systems (MEMS). Today MEMS affect almost everything we do from household appliances, via cars we drive and planes that whisk us from continent to continent, to spaceships used for search of/and exploration of other worlds. The modern microsensors are also used to explore for and produce petroleum products that are used in multitude of today's applications. To facilitate these advances a great majority of MEMS is used in the form of sensors. However development of MEMS in general and sensors in particular poses one of the greatest challenges in today's experimental mechanics. Among MEMS, the greatest contemporary interest is in the area of inertial sensors because they have numerous uses ranging from everyday applications to highly specialized ones, including many industrial platforms. As such they have tremendous potential to affect future of humanity. However, advances in MEMS, such as pressure and temperature sensors as well as gyroscopes and accelerometers, require the use of computational modeling and simulation coupled/combined with physical measurements. This author believes that successful combination of computer aided design (CAD) and multiphysics as well as multiscale simulation tools with the state-of-the-art (SOTA) measurement methodology will contribute to reduction of high prototyping costs, long product development cycles, and time-tomarket pressures while developing new sensors with nanoscale characteristics for various applications we use now and those that we will need in the future. In our approach we combine/hybridize a unique, fully integrated, software environment for multiscale, multiphysics, high fidelity analysis of the contemporary sensors with the SOTA optoelectronic laser interferometric microscope (OELIM) methodology, which is based on recent developments in speckle. The speckle-based OELIM methodology allows remote, noninvasive, full-field-of-view (FFV) measurements of deformations with high spatial resolution, nanometer accuracy, and in near real-time. In this paper, both, the software environment and the OELIM methodology are described and their applications are illustrated with representative examples demonstrating viability of the completely autonomous computer-based procedures for the development of contemporary sensors with nanocharacteristics suitable for the advancement of new evolving technologies that will shape our future. This process is demonstrated using devices of contemporary interest. The preliminary examples demonstrate capability of our approach to quantitatively determine effects of static and dynamic loads on the performance of sensors. In addition, potential economic rewards of the technology, projected into near future, will also be discussed.

The paper presents the electro-optical design of an interferometric inspection system for massive parallel inspection of Micro(Opto)ElectroMechanicalSystems (M(O)EMS). The basic idea is to adapt a micro-optical probing wafer to the M(O)EMS wafer under test. The probing wafer is exchangeable and contains a micro-optical interferometer array: a low coherent interferometer (LCI) array based on a Mirau configuration and a laser interferometer (LI) array based on a Twyman-Green configuration. The interference signals are generated in the micro-optical interferometers and are applied for M(O)EMS shape and deformation measurements by means of LCI and for M(O)EMS vibration analysis (the resonance frequency and spatial mode distribution) by means of LI. Distributed array of 5×5 smart pixel imagers detects the interferometric signals. The signal processing is based on the "on pixel" processing capacity of the smart pixel camera array, which can be utilised for phase shifting, signal demodulation or envelope maximum determination. Each micro-interferometer image is detected by the 140 × 146 pixels sub-array distributed in the imaging plane. In the paper the architecture of cameras with smart-pixel approach are described and their application for massive parallel electrooptical detection and data reduction is discussed. The full data processing paths for laser interferometer and low coherent interferometer are presented.

The low-coherence interferometry is already an established technique for the high-resolution characterization of surface profiles. Its application in many industrial areas is however partially limited due to undesired effects in the interference pattern caused by different surface's roughness and form properties. The appearance of speckles in rough surfaces or the batwing-effect in high-precision topographies are examples of undesired influences. Another important limiting factor is the size and robustness of the metrological set-ups. The measurement of small cavities or the integration in production machines are therefore still a challenge. In this work the application of a fiber-optical low-coherence interferometer for the characterization of different surface profiles, as well as miniaturized and / or hard accessible features is presented. Focus will be given on the measurement of optical "uncooperative" surfaces, as rough and / or curved surfaces, for example in small cavities, using the analysis of the speckle phenomena.

In this contribution we show how spatially incoherent emission from a broad-area vertical-cavity surface-emitting laser (BAVCSEL) can be used for low-speckle laser projection. In our projection setup, we use a microlens beam homogenizer in order to homogenize the intensity distribution and to exploit the low spatial coherence of the VCSEL. In order to investigate the speckle in a projection setup using a BA-VCSEL as light source, we compare speckle values in case of modal and nonmodal emission of the BA-VCSEL. Furthermore, the microlens beam homogenizer can either be illuminated with the laser's near field or far field, leading to comparable results. Speckle contrast values as low as 3.5% in case of nearfield illumination, and 2.5% in case of farfield illumination, are measured without using any additional or mechanically moving components to destroy the coherence of the laser beam. The microlens array in the setup is essential in order to obtain speckle reduction, since it generates an overlap of mutually independent speckle patterns, thus reducing the overall speckle in the projected image. We successfully model the speckle contrast reduction, taking into account all contributing speckle reducing factors.

Multiple-wavelength holographic interferometry is an effective technique to generate a contour map of a diffusely reflecting object surface in the speckle field. A synthetic wavelength can be well generated by changing the current of laser diodes. A small synthetic wavelength needs a wide tunable external-cavity laser diode. A step object profile with discontinuous structure can be measured by using a synthetic wavelength to be sufficiently large that is derived from a known step height measured by vernier calipers but not wavelength measurements. The tunable laser-diode holographic interferometry is verified by experimental results.

Digital holography utilizing optical Doppler effect is proposed, and the surface shapes of objects are measured in an environment with a disturbance. In this method, the time variation of interference fringes are recorded using a high speed CMOS camera. The complex amplitude of the object beam included in the recorded images are extracted by time-domain Fourier analysis. Light propagation is calculated using the complex amplitude, and the surface shape of the concave mirror is obtained. We also apply the Doppler phase-shift digital holography to two-wavelength interferometry. The phase distribution for the effective wavelength with two different wavalenghes of light sources is obtained. The experimental results show our proposed method is very useful in industrial sensing and experimental mechanics.

The paper presents the analysis and enhancements of interferometric methods which may provide better quality projections for tomographic, in-line determination of geometry and refractive index distribution changes along classical as well as photonic crystal fiber tapering structure. The method and system provides high optical resolution and sensitivity for determination of refractive index changes. It also provides the possibility of investigation of structures with and without circular symmetry of refractive index distribution. In the paper the interferometric tomography method in Mach-Zehnder interferometer configuration is applied and the measurements of classical and photonics crystal fibers are presented. The analysis of future use of in-line digital holographic method coupled with a variety of techniques for enhanced phase reconstruction is performed.

This paper presents work and results performed with LAUM collaboration in digital three-color holographic interferometry applied to Fluid Mechanics. In this method, three different wavelengths are used as luminous light source of the interferometer and the optical setup generates three micro interferences fringes which constitute three spatial carrier frequencies. When these images are recorded with a color sensor, the resolution of reconstructed hologram depends on the pixel size and pixel number of the sensor used for recording and also, the shape and the overlapping of three filters of color sensor influence strongly the three reconstructed images. This problem can be directly visualized in 2D Fourier planes on red, green and blue channels. To better understand this problem and to avoid parasitic images generated at the reconstruction, three different sensors have been tested : a CCD sensor equipped with a Bayer filter, a Foveon sensor and a 3CCD sensor. The best results have been obtained with the last one. In the recording principle, interference micro fringes produced by the superimposition of three reference waves and three measurement waves can be simultaneously recorded on the three spectral bands (red, green, and blue). Phase and amplitude images are computed using 2D Fourier transform in delayed time. Spectral filtering is applied on each Fourier plane in order to eliminate the parasitic diffraction orders. Then, phase differences are obtained by subtracting the reference phase to the probe phase. Several optical setups were tested and the best configuration allows the visualization of field about 70mm and increases the sensitivity since the measurement wave crosses twice the test section. Interferences induced by the wake flow have been recorded and intensities have been computed from the phase differences. Finally, one shows that fringes obtained with this process are those found with real-time color holographic interferometry using classical holographic plates.

We present a measurement system based on digital holography and two light sources, which is suitable for high speed three-dimensional deformation measurements. Circular in-plane sensitivity is achieved using a diffractive optical element (DOE) for illumination in combination with two laser sources creating two holograms on one camera frame. Both holograms are separated using two different spatial carrier frequencies. As the two lasers are illuminating the object under a different angle it is possible to calculate in-plane and out-of-plane deformation out of two camera frames and the resulting four holograms. The system may be applied e.g. for high speed deformation measurements or the measurement of residual stress. Besides first measurement results obtained with the holographic device and a comparison to results of an already existing measurement system based on digital speckle pattern interferometry (DSPI) are presented.

The evaluation of the Rayleigh-Sommerfeld diffraction formula by means of numerical convolution and angular spectrum filtering are two of the most usual reconstruction methods in digital holography. Both of them are normally implemented by using a discrete Fourier transform and a sample of, respectively, the free space impulse response function and the corresponding transfer function. In this communication we propose a modified formulation of the sampled free space impulse response and transfer functions in terms of five dimensionless parameters: the wavelength to horizontal pixel size ratio, the reconstruction distance to horizontal field size ratio, the field and pixel aspect ratios and the number of pixels in the horizontal direction. This formulation simplifies the task of comparing and finding equivalences between holographic reconstruction situations with different distance, wavelength, field and pixel sizes. The reconstruction range for each of the methods is expressed in terms of the aforementioned dimensionless parameters by analyzing the resolution limits for the impulse response and the transfer function, respectively. This notation makes very simple to decide which of the two methods should be used for given conditions as well as to tailor range extension strategies based on the effects of hologram manipulations such as zero padding or pixel splitting. The details of the implementation of the convolution and angular spectrum algorithms with the proposed formulation are disclosed paying particular attention to the consequences of the sacrificial zero-padding required to avoid aliasing in Fourier-transform based cyclic convolution.

We review some of the statistical properties of polarization-related speckle phenomena, with an introduction of a less known concept of polarization speckles and their spatial degree of polarization. As a useful means to characterize twopoint vector field correlations, we review the generalized Stokes parameters proposed by Korotkova and Wolf, and introduce its time-domain representation to describe the space-time evolution of the correlation between random electric vector fields at two different space-time points. This time-domain generalized Stokes vector, with components similar to those of the beam coherence polarization matrix proposed by Gori, is shown to obey the wave equation in exact analogy to a coherence function of scalar fields. Because of this wave nature, the time-domain generalized Stokes vector is referred to as generalized Stokes vector wave in this paper.

The possibility to "dress up" the speckles and thereby providing them with a fine structure will be discussed. As these speckles arise from scattering off solid targets, the dynamics of the speckles and their inherent fine structure might vary, providing information on different aspects of the surface displacement. This is achieved by illuminating the object with structured light, and observing the speckle field as it passes an optical system. In this way, simultaneous measurement of displacement (e.g. 2-D) and rotation can be performed. The application of this concept with a system based on spatial filtering velocimetry and ordinary speckle correlation will be discussed.

Two-wavelength speckle interferometry (SI) is widely used for shape measurements of rough surfaces. A surface under test arranged in an interferometer is illuminated with laser light having two different wavelengths. In the most simplified case the two interferograms are intensity-subtracted where the fringe distance in the detected pattern provides the information about the difference in height of the corresponding positions of the test surface. The distance between two fringes can be associated with the synthetic wavelength Λ, equivalent to the envelope of a beat frequency. In interferometry the use of the synthetic wavelength Λ is valid as long as the wavelengths of the two interfering waves are approximately equal. Since the height resolution is directly linked to the synthetic wavelength, a decrease of Λ will lead to an increased resolution of height. This statement, however, is only valid if the employed wavelengths are similar. We present how the choice of wavelengths of a Mach-Zehnder setup affects the resolution of the interferometer. On the one hand the term of synthetic wavelength is reviewed analytically concerning wavelengths with increasing Λλ. On the other hand we verified these results with a numeric simulation. In addition to the analytic model, the numeric simulation includes a more advanced surface model including roughness. As a result we provide a recommendation under what circumstances the decrease of Λ leads to an increased height resolution.

Tilt Scanning Interferometry (TSI) has been recently developed as an experimental method to measure multi-component displacement fields inside the volume of semitransparent scattering materials. It can be considered as an extension of speckle interferometry in 3D, in which the illumination angle is tilted to provide depth information, or as an optical diffraction tomography technique with phase detection. It relies on phase measurements to extract the displacement information, as in the usual 2D counterparts. A numerical model to simulate the speckle fields recorded in TSI has been recently developed to enable the study on how the phase and amplitude are affected by factors such as refraction, absorption, scattering, dispersion, stress-optic coupling and spatial variations of the refractive index, all of which may lead to spurious displacements. In order to extract depth-resolved structure and phase information from TSI data, the approach had been to use Fourier Transformation of the intensity modulation signal along the illumination angle axis. However, it turns out that a more complete description of the imaging properties of the system for tomographic optical diffraction can be achieved using a 3D representation of the transfer function in k-space. According to this formalism, TSI is presented as a linear filtering operation. In this paper we describe the transfer function of TSI in 3D k-space, evaluate the 3D point spread function and present simulated results.

The main limitation to imaging of planets outside the Solar System is the contrast ratio and small separation between the star and its companion. Quasi-static speckles produced by the telescope optics constitute the main impediment for detection of close-in sources. We propose a complete framework for the detection and first-order characterization of extrasolar planets from a sequence of compensated images. The new methods rely on the observation that statistics of intensity inside the core of a high-quality point spread function differ from the off-axis (speckle) statistics. To calculate the efficiency of our methods we derive analytical expressions for mean and standard deviation of intensity. For photometry, the difference in statistics between the on-axis and off-axis intensity is used to constrain a one-dimensional, "blind," iterative deconvolution at the position of the companion.

Dynamic deformation measurement with a large in-plane deformation is performed by using virtual speckle patterns. The virtual speckle pattern has been generally produced by using Fourier technology. However, it takes a long calculating time to produce a virtual speckle pattern under Fourier technology, because the method requires Fourier transform operation at each pixel of CCD. In the proposed method, virtual speckle patterns are produced by Carré algorithm without any operation by Fourier transform. As the results, it is confirmed that the calculating cost of virtual speckle patterns is improved remarkably, and that the new method also is almost equal to the ordinary methods in measurement accuracy.

Measuring the coefficient of thermal diffusion (CTD) of materials is a relatively complex problem. In this report novel optical method for determining CTD is proposed which is based on an analysis of the spatial-temporal dynamics of the speckle field. The proposed method for measuring the coefficient of thermal diffusion is based on the measurement of an average speed of the speckle-field movement along the specimen surface. Due to statistical nature of speckles, their movement must be also described statistically. Our approach consists in the use of correlation functions describing the degree of change in a speckle-image of some element of the surface in the process of heating or cooling. The advantages of the proposed method are: the technology is fully optical and thermal sensors are not needed, universal and can be customized for specific applications, fast, non-contact and non-invasive; remote measurements from distances of up to several meters or in hard-to-reach positions are possible. Optical measurement of CTD has been carried out for investigation of thin multilayer and nanoporous structures, particularly, those of nanoporous anodic alumina. CTD has been measured for nanoporous anodic alumina structures both modified and not modified with nano-diamonds. Modified films have been established to have larger values of CTD. High resolution allows one to measure spatial inhomogeneities of thermophysical properties of materials. The CTD has been measured along the surface of thin film as well as perpendicular to it.

Despite of the fact that primary purpose of universities is to disseminate knowledge, university research happens to be extremely important for industry development. More than 70 % of most important patents are originated from university studies. This paper addresses specifics of university intellectual property (IP) and provides strategies for successful implementation of university inventions. Practical aspects of inventing such as the patent ownership and monetary rewards for the inventors, working at the university, are discussed. We paid special attention to certain distinctions in IP laws in various countries, which is important to know due to the growth of international collaboration between universities, multi-national character of companies and their cooperation with the universities. We show IP managements in industry - academia research on a fair basis within two different models: cooperation research paid by third party such as government and contract research paid by industry.

A setup for an NIR-LCSI instrument is introduced. It is based on a Superluminescence diode (SLD) (wavelength = 1280nm, FWHM = 50nm) and an InGaAs camera with VGA resolution. The paper presents a work in progress. The aim of the research work is to measure the chipping process in a Si wafer saw with high spatial resolution. Hereby the sawing channel inside the silicon block is investigated. The chipping generates a change of the interface topography of the sawing channel. NIR-LCSI will be applied to measure this topography change and contributes thus to determine the size and volume of the silicon chips and thus the cutting rate of the sawing process. This paper presents a novel concept to increase the spatial resolution of the imaging system. With the use of a new type of "immersion" optics the numerical aperture can be significantly increased and a spatial resolution close to, or even below, the nominal illumination wavelength can be obtained. The speckle size and the resulting spatial and depth resolution of the LCSI measurements are investigated.

Although low coherence interferometers are commercially available (e.g., white light interferometers), they are generally quite bulky, expensive, and offer limited flexibility. In the paper the new portable profilometer based on low coherence interferometry is presented. In the device the white light diode with controlled spectrum shape is used in order to increase the zero order fringe contrast, what allows for its better and quicker localization. For image analysis the special type of CMOS matrix (called smart pixel camera), synchronized with reference mirror transducer, is applied. Due to hardware realization of the fringe contrast analysis, independently in each pixel, the time of measurement decreases significantly. High speed processing together with compact design allows that profilometer to be used as the portable device for both in and out door measurements. The capabilities of the designed profilometer are well illustrated by a few application examples.

In this communication we introduce a low or reduced coherence interferometry technique that can be used to retrieve surface topology on samples with high roughness. Moreover, we will show that the approach enables surface topology measurement also at the interface of so-called turbid media, where multiple scattering inside tissues can be a major issue, preventing accurate measurements.

We consider the dynamical properties of speckles observed through a second static diffuser arising from a linear or angularly displaced first diffuser. Analytical expressions are obtained for general situations where both the space between the displaced and the static diffuser and the space between the static diffuser and the plane of observation consist of an optical system that can be characterized by a complex-valued ABCD-matrix (e.g. simple and complex imaging systems, free space propagation in both the near- and far-field, and Fourier transform systems). The use of the complex ABCD-method means that diffraction due to inherent apertures is included. One of the diffusers is assumed to give rise to fully developed speckle, i.e. the scattered phase is assumed to be delta-correlated, whereas the second and dynamic diffuser has a finite lateral scale. The illumination of the displaced diffuser is assumed to be Gaussian but the derived expressions are not restricted to a plane incident beam. The results are applicable for speckle-based systems for determining mechanical displacements, especially for long-range systems, and for analyzing systems for measuring biological activity beyond a diffuse layer, e.g. blood flow measurements through human skin.

This paper proposes the design of decision models with Computational Intelligence techniques using image sequences of dynamic laser speckle. These models aim to characterize the dynamic of the process evaluated through Temporal History Speckle Patterns (THSP) using a set of available descriptors. The models use those sets selected to improve its effectiveness, depending on the specific application. The techniques of computational intelligence field include using Artificial Neural Networks, Fuzzy Granular Computation, Evolutionary Computation elements such as Genetic Algorithms, among others. The results obtained in experiments such as the evaluation of bacterial chemotaxis, and the estimation of the drying time of coatings are encouraging and significantly improve those obtained using a single descriptor.

The biospeckle laser (BSL) has been applied in many areas of knowledge and a variety of approaches has been presented to address the best results in biological and non-biological samples, in fast or slow activities, or else in defined flow of materials or in random activities. The methodologies accounted in the literature consider the apparatus used in the image assembling and the way the collected data is processed. The image processing steps presents in turn a variety of procedures with first or second order statistics analysis, and as well with different sizes of data collected. One way to access the biospeckle in defined flow, such as in capillary blood flow in alive animals, was the adoption of the image contrast technique which uses only one image from the illuminated sample. That approach presents some problems related to the resolution of the image, which is reduced during the image contrast processing. In order to help the visualization of the low resolution image formed by the contrast technique, this work presents the three-dimensional procedure as a reliable alternative to enhance the final image. The work based on a parallel processing, with the generation of a virtual map of amplitudes, and maintaining the quasi-online characteristic of the contrast technique. Therefore, it was possible to generate in the same display the observed material, the image contrast result and in addiction the three-dimensional image with adjustable options of rotation. The platform also offers to the user the possibility to access the 3D image offline.

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

The dynamic laser speckle or biospeckle laser has been used to analyze the activity of biological and non-biological material by means of various statistical techniques and image processing. However, a challenge to adopt this technique is the ability to identify, in the same material, an area of low activity immersed in an environment of a higher activity. This work was carried out to evaluate the spectral approach associated to biospeckle laser technique as an alternative to identify distinct activities areas in the same material. Biofilm samples, which present well known protocols to be prepared, and a simpler structure than vegetal and animal tissues, were prepared with potato starch and corn starch with areas of different levels of moisture and were analyzed using the biospeckle laser associated with the wavelets transform in order to evaluate the data in the spectral domain. The effect of a black or white background below the samples was also tested. The image analysis was conducted using Generalized Difference and Fujii techniques before and after the implementation of the wavelets transform producing the filtration of the data. The results allowed the visualization of different activities areas in different frequency bands. The areas of activity were presented clearer than the traditional procedures without filtering. A new way to present the results of the biospeckle and the frequency domain information was proposed to enhance the visualization of a whole picture. It was also noted that the greatest contrast between areas of different activity were promoted by materials of different compositions. In some experimental configurations there were possible to tag the relationship between the frequency and depth of the active or inactive material. The influence of the color, black or white, of the background was also noticed in the results, but with white background better in some configurations and with the black better in others.

Using the electronic speckle pattern interferometry (ESPI) technique in the in-plane arrangement, the coefficient of thermal expansion (CTE) of a composite material that will be used in a passive focusing mechanism of an aerospace mission was measured. This measurement with ESPI was compared with another interferometric method (Differential Interferometer), whose principal characteristic is its high accuracy, but the measurement is only local. As a final step, the results have been used to provide feedback with the finite element analysis (FEA). Before the composite material measurements, a quality assessment of the technique was carried out measuring the CTE of Aluminum 6061-T6. Both techniques were compared with the datasheet delivered by the supplier. A review of the basic concepts was done, especially with regards to ESPI, and the considerations to predict the quality in the fringes formation were explained. Also, a review of the basic concepts for the mechanical calculation in composite materials was done. The CTE of the composite material found was 4.69X10^-6 ± 3X10^-6K^-1. The most important advantage between ESPI and differential interferometry is that ESPI provides more information due to its intrinsic extended area, surface deformation reconstruction, in comparison with the strictly local measurement of differential interferometry

The study of the tympanic membrane is fundamental because it is one of the most important components of the middle ear. By finding the membrane's vibration patterns and quantifying the induced displacement, it is possible to characterize and determine its physiological state. Digital Holographic Interferometry (DHI) has proved to be a promising optical non-invasive and quasi-real time method for the investigation of different mechanical parameters of biological tissues. In this paper, we present a digital holographic interferometry setup used to measure the frequency response of the tympanic membrane in post-mortem cats subject to acoustic stimuli in the range of 485 Hz up to 10 kHz. We show the resonant vibration patterns found for this range of frequencies and the corresponding displacement amplitudes induced by the acoustic waves. The results show the potential that this method has to help improve the understanding of the tympanic membrane's working mechanisms.

The incidence of malignant melanoma (MM), the most aggressive and deadly form of skin cancer, has been increasing rapidly since the last few decades. Clinical differentiation between MM and pigmented benign skin lesions based on visual assessment can be challenging because some of benign lesions such as melanocytic lesions (ML) and seborrheic keratoses (SK) resemble MM. In this paper we introduce a novel, non-invasive, "optical biopsy" method based on laser speckle. Propagating inside the skin tissues, photons undergo optical path dispersion due to scattering. Therefore the emerging light loses the initial state of coherence, which influences the backscattered speckle pattern if the light optical path deviation in a tissue is comparable with the length of coherence. Speckle contrast is a measure of this decorrelation process. Histology shows that MM, ML, and SK have diverse morphology. We hypothesized that the morphological differences can be detected by polychromatic speckle, and the technique can be used to differentiate these lesions in vivo. In a study with 12 MMs, 24 MLs, and 37 SKs, we computed the speckle contrast related to their superficial skin region. The mean contrast of MM, ML and SK were 0.78 (standard error (SE) = 0.02, 0.63 (SE = 0.01), and 0.67 (SE = 0.01), respectively. Statistical test showed that there was a significant difference among the contrast of the three types of lesions (p < 0.001, Kruskal-Wallis), and intergroup pair-wise tests showed significant differences in distribution between all three groups. Potentially, speckle imaging can differentiate these lesions.

When measuring 3D-shape with triangulation and projected interference fringes it is of interest to reduce the phase error in the fringe pattern. A study has been carried out concerning parameters that will affect the phase error and an analytical expression has been derived. It is concluded that the phase error depends on the speckle contrast, C, and the modulation, M, of the fringes and since the phase in this investigation is determined using the spatial carrier method the phase error also depends on the filtering of the Fourier spectrum. To reduce the phase error this work has been focusing on suppressing the speckle contrast. For this the method with a moving aperture is used; a disk with several apertures is rotated in the aperture plane of the camera lens. To verify the derived expression for the phase error and the method to suppress speckles both numerical simulations and experiments have been performed. In the measurements made it was concluded that after an aperture movement of three aperture diameters the speckle contrast and hence the phase error was reduced by 60 %. A phase error of 0.15 radians was obtained in the experiments, thus approximately 1/40 of a fringe period.

We report a polymer based multiple diffraction modulator, in which PDMS (polydimethylsiloxane) is utilized as the actuation material, for speckle reduction. The properties of the PDMS are characterized based on its response time and deformability, which are the key properties concerned in this work. The structure dependent properties of PDMS are discussed. Using the described technique, the PDMS satisfy the system demand. The modulator is used to create real-time diffraction patterns by dynamic gratings formed by flexible PDMS. The diffracted light passes through a diffuser, which is placed after the modulator, and induces speckle patterns on the screen. Speckle-reduction is achieved by adding the time-varying speckle patterns in the integration time of the detector. It is observed that using the modulator which has two gratings, the speckle contrast ratio reaches to 50%, which shows fair agreement with the simulation.

Optical metrology has shown to be a versatile tool for the solution of many inspection problems. The main advantages of optical methods are the noncontact nature, the non-destructive and fieldwise working principle, the fast response, high sensitivity, resolution and accuracy. Consequently, optical principles are increasingly being considered in all steps of the evolution of modern products. However, the step out of the laboratory into the harsh environment of the factory floor was and is a big challenge for optical metrology. The advantages mentioned above must be paid often with strict requirements concerning the measurement conditions and the object under test. For instance, the request for interferometric precision in general needs an environment where high stability is guaranteed. If this cannot be satisfied to a great extent special measures have to be taken or compromises have to be accepted. But the rapid technological development of the components that are used for creating modern optical measurement systems, the unrestrained growth of the computing power and the implementation of new measurement and inspection strategies give cause for optimism and show that the high potential of optical metrology is far from being fully utilized. In this article current challenges to optical metrology are discussed and new technical improvements that help to overcome existing restrictions are treated. On example of selected applications the progress in bringing optical metrology to the real world is shown.

Numerical experiments are carried out for a plane wave propagating in atmospheric turbulence and reflected from a rough surface under weak to strong fluctuation condition. The statistical characteristics of the scintillation index and the number density of the phase singularity (or the optical vortex) are analyzed. The density of the phase singularity is evaluated as a function of the Rytov index, the Fresnel length, the correlation scale and roughness of the surface. Correlation and interaction between both types of phase singularity caused by rough surface and turbulence are analyzed. Results could provide a theoretical basis for measurement of surface roughness under known turbulence condition or measurement of atmospheric turbulence under known surface roughness condition.

Pulsed TV-holography (PTVH) can be used for obtaining two-dimensional maps of instantaneous out-of-plane displacements in plates. In particular, scattering patterns generated by the interaction of elastic waves with defects can be measured with PTVH and employed for non-destructive inspection and damage detection in plate structures. For quantitative characterization of damage (position, dimensions, orientation, etc.) on this basis, modeling of elastic wave scattering is usually performed in terms of full-vector three-dimensional formulations based on elasticity theory. In this work, a finite element method (FEM) applied to a two-dimensional scalar model based on Helmholtz equation is employed for obtaining a quantitative description of the scattering patterns, avoiding the aforementioned more complex and rigorous standard approach. Simulated scattering patterns are obtained with the scalar FEM assuming harmonic regime and free-stress boundary conditions. The corresponding experimental interaction of narrowband Rayleigh-Lamb waves with artificial defects in plates are measured using our specifically developed PTVH system. In our case, the raw optical phase-difference values are processed by employing a specially developed procedure, based on a two step spatial Fourier transform method, to derive a high quality two-dimensional acoustic field map from which an important part of the noise component has been filtered out. A comparison between filtered experimental maps and FEM simulated maps is developed, considering defects with different sizes in relation to the acoustic wavelength.

This paper is concerned with the development of a calibrated 3D shearography strain measurement instrument, calibrated iteratively, using a combined mechanical-optical model and specially designed test objects. The test objects are a cylinder loaded by internal pressure and a flat plate under axial load. Finite element models of the samples, combined with optical models of the shearography system, allow phase maps to be simulated for subsequent comparison with experimental phase maps from the shearography instrument. The algorithm to extract the strain maps from the phase maps includes an error compensation for in-plane strains on curved surfaces, measurement channel redundancy, variations in the shear magnitude due to object shape and the optical characteristics of the imaging system. The improvement introduced by the error compensation techniques is verified by the opto-mechanical simulation and its effect is demonstrated experimentally on maps of displacement gradient.

Biospeckle patterns are named also "boiling" speckles due to its dynamic appearance. This activity takes place when the sample changes its properties due to diverse causes. This phenomenon is characteristic of biological samples and of the some industrial process. There are many descriptors that have been developed to characterize biospeckle patterns. This paper presents some approaches to compare and evaluate a set of time domain descriptors using a controlled experiment.

Water is a noble natural resource and its monitoring and control are key to an efficient and responsible use concerning with the impacts in the ambient. Particularly in irrigation processes there are many approaches to monitor the water consumption, nevertheless the access of water demand in an irrigated crop presents some challenges to the routine methods. The effort to develop a non-destructive methodology associated with the ability to be handle, unfolds the way to the adoption of optical techniques. The biospeckle laser phenomenon can be elected as one of the potential instruments to access the water content in a leaf and to associate this information to the water demand. The sensitiveness of the biospeckle patterns related to biological activities is the basis of the hypothesis which concerns the monitoring of water activity in a leaf. This work evaluated the feasibility to implement the biospeckle laser as a tool to measure the water content in a leaf and to relate it with the demand of water in a perennial crop, such as coffee trees. Complementary it was tested the ability and the robustness of the proposed protocol in a portable assembly. Plants of coffee crop, coffee arabica trees, were prepared to be monitored during water stress. The proposed monitoring were carried out in leaves without detach them from the plant, within 5 consecutive days. The results presented a significant relation between the water content reduction and the biospeckle values.

A new approach for decoding displacements from surfaces encoded with random patterns has been developed and validated. The procedure is based on phase analysis of little zones of interest. Resolution in standard conditions (32×32 pixels²) is 2/100th pixel, for a spatial resolution of 9 pixels. Here we adapt new concepts proposed by Badulescu¹³ on the grid method to random patterns for the direct measurement of strains. First metrological results are encouraging: resolution is proportional to strain level, being 1/10th of the nominal value, for a spatial resolution of 9 pixels (ZOI 64×64 pixels²). Random noise have to be carefully controlled. A numerical example shows the relevance of the approach. Then, first application on a carbon fibre reinforced composite is developed. Fabric intertwining is studied using a tensile test. Over-strain are clearly visible, and results connect well with previous ones¹⁶.

Publisher's Note: This paper, originally published on 13 September 2010, was withdrawn on 9 July 2020 per author request.

Barker and Barker-like binary phase codes have previously been used for speckle reduction in line-scan laser projectors, and a speckle contrast factor decreased down to 6% has been theoretically achieved assuming ideal imaging conditions. In this article, it is shown by theoretical simulations that the speckle reduction performance of the the binary phase codes is adversely affected by the finite numerical aperture and the aberrations of the projections lens. A minimum numerical aperture of the projection lens is needed to faithfully reproduce the binary phase code placed at an intermediate image plane onto the final display screen. The effects of the cell dimension of the binary phase code are also considerd in simulations.

Barker binary phase code of maximum length 13 has previously been used for speckle reduction in line-scan laser projectors, and a speckle contrast factor decreased down to 13% has been achieved. In this article, Barker-like binary phase codes of length longer than 13 are used at an intermediate image plane. It is shown by theoretical calculation that much better speckle reduction with speckle contrast factor up to 6% can be achieved by using longer binary phase codes other than the Barker code. Preliminary experimental results are also presented indictaing good speckle reduction.

Speckle suppression in projection displays with the laser light source can be achieved by imaging a changing diffuser with random phase cells onto the screen. Theoretical expressions for the speckle contrast in this method have been earlier obtained in the case when different realizations of the phase diffuser produce statistically independent patterns of the light field on the screen [J. W. Goodman]. In the present paper, these expressions are generalized in the case when different realizations of the phase diffuser produce partly correlated speckle patterns. Both cases when the diffuser just fills or overfills the projection optics are considered. Possible structure of a motionless changing diffuser is presented. It includes the dynamic diffractive optical element (DDOE) and a light homogenizer. The DDOE can be based on the electrically controlled spatial light modulator with a deformable polymer layer (SLMDPL). The SLMDPL can handle high light power and therefore, can be used in projection displays with powerful laser beams.

It has been suggested to use Hadamard matrices H(M) of order M for speckle reduction in laser based projection displays by creating a set of M two-dimensional phase masks from rows or columns of the H(M) and introducing them sequentially into the intermediate image plane of the laser projector. The speckle contrast reduction can reach M^-1/2. In this paper, we have analyzed the contrast reduction. The result presents that any matrices can be used to form phase mask as long as its columns are orthogonal to each other, such as the parts of columns of Hadamard matrix. The speckle contrast reduction is determined by the number of projection resolution elements lying in single camera resolution element. To get high quality image with low speckle contrast reduction by Hadamard matrix, its order should be as high as possible. However, it is impossible to implement by vibrating diffuser with high order due to the large vibration amplitude. The motionless time-vary diffuser with Hadamard matrix phase pattern based on MEMS technology and Electro-optical effect can be a good choice.

An array of diffraction gratings and a Random Phase Plate (RPP) are used to suppress laser speckle effect. Dynamic diffraction spots are generated on the surface of the RPP, after which the scattering lights are perceived by a detector. Speckle Contrast Ratio (CR) and Number of Independent Speckle Patterns (NISP) with different gratings rotation orientations (θ), gratings frequencies (grooves per millimeter: f), diameters of laser beam (D), and distances between the array of diffraction gratings and the RPP (Z) are calculated based on ZEMAX simulations, and an optimized model is proposed.

We present a wavefront retrieval method for radiation comprising several wavelengths. Both numerical models and experimental results are presented. Numerical modeling implies iterative phase retrieval procedure for all wavelengths in spectrum. For reconstruction we can use two different algorithms, one inherits from one proposed by Osten, Pedrini and Almoro, the second one implies expansion by Hermite-Gauss or Laguerre-Gauss basis set which allows to decrease calculation time consumption. In experiment, speckle patterns can be formed either by spectral supercontinuum radiation from photonic-crystal fiber (PCF) or by Stokes components of stimulated Raman scattering (SRS) from second harmonic of pulse Nd:YAG laser radiation in barium nitrate crystal.

Recent revitalization of interests in applying speckle techniques gives rise to the concern of measurement accuracy. In particular, speckle contrast, an important metric in numerous optical techniques, is affected by many factors related to light sources, propagation media, and receivers. As a result, proper experimental design is required to minimize measurement errors. This article considers errors introduced by the discrepancy of incidence and observation angles, by the limited number of available speckles, and by intensity saturation.

Optical coherence tomography (OCT) is an imaging technique based on the low coherence interferometry, in which signals are obtained based on the coherent addition of the back reflected light from the sample. Applying computational methods and automated algorithms towards the classification of OCT images allows a further step towards enhancing the clinical applications of OCT. One attempt towards classification could be achieved by statistically analyzing the texture of the noisy granular patterns - speckles that make the OCT images. An attempt has been made to quantify the scattering effects based on the speckle texture patterns the scatterers produce. Statistical inference is drawn from the textural analysis of the features based on the spatial intensity distribution on the agar phantoms with different concentration of Intralipid solutions. This preliminary study conducted on agar-Intralipid solution has showed us that it is possible to differentiate between different types of scatterers based on the speckle texture studies. The texture analysis has also been extended in an attempt to identify the invasion of melanoma cell into tissue engineered skin. However using the same approach of texture analysis, we have not obtained satisfactory results for carrying on with the computer-based identification of the invasion of the melanoma in the tissue engineered skin, the reason for which has to be further studied and investigated upon.

Roughness of paper surface is an important parameter in paper manufacturing. Surface roughness measurement is one of the central measurement problems in paper industry. Surfaces are often coated and the amount of coating and method of application used depends on the roughness of the base paper [1], [2]. At the moment, air leak methods are standardized and employed in paper industry as roughness rating methods. Air leak rate between measured paper surface and a specified flat land is recorded by using specialized pneumatic devices under laboratory conditions. Such a measurement closely corresponds to the roughness of a surface, the greater the air leak the rougher the surface. Air leak methods are rather easy to apply to paper and give stable results, although they measure roughness indirectly, need laboratory conditions, and thus unsuitable for on-line use. To measure real topography of paper surface, it is scanned with mechanical or optical profilometers. These methods provide accurate information on surface topography, but also demand laboratory conditions. In our work, present a method of measure based in the analysis of the texture of speckle pattern on the surface. The image formed by speckle in the paper surface is considered as a texture, and therefore texture analysis methods are suitable for the characterization of paper surface. The results are contrasted to air leak methods, optical profilometers (confocal microscopy), and fringe projection.

Photo-electromotive-force effect induced by an oscillating speckle pattern of light onto photorefractive CdTe: V and Bi₁₂TiO₂₀ is studied. The light pattern is produced by the reflected laser beam on a vibrating surface. As a result of the photo-emf effect, a photocurrent signal in the material arises that is related to the vibrating surface amplitude and frequency. This electric signal is first pre-amplified by an op-amp in transimpedance regime and then the first temporal harmonic component is measured using a phase selective frequency tuned lock-in amplifier. This harmonic shows a maximum value occurring for certain value of the normalized vibration amplitude. This technique is been developed to be used for the measurement of transverse mechanical vibrations.

Carbon fiber reinforced polymers have become thicker due to its use in aircraft manufacturers. Their manufacturing processes implies the generation of important residual stresses. In this work, a L-shaped thick composite shell is analyzed under moderate temperature changes. A stacking sequence error is voluntarily added in order to simulate possible manufacturing failure. Displacements are measured on the shell front and on its side using a mixed inplane and out-of-plane DSPI set-up, limiting the zone of interest to region of maximum curvature. Variations of the Lshape with temperature are recorded and typical flexure strain effects are outlined. Several parameters of interest can be deduced from the experiment.

This paper presents an investigation on the applicability of shearography to characterize the location and depth of defects in composite materials. Sets of specimens with artificial square flaws between the layers of a composite material have been used for the experiments. Flaws with different sizes were placed at different depths along the thickness of the material. Time-Average and Stroboscopic laser illumination have been applied together with vibrational loading. The resonance frequencies were related to the depths of the different faults sizes. Frequency x depth results showed good behavior for different defect sizes. These results encourages to further studies with other types of faults and composite materials.

This paper presents a novel technique to investigate coating adhesion using a radial speckle interferometer and a microindentation test. The proposed technique is based on the measurement of the radial in-plane displacement field produced by a microindentation introduced on the coated surface of the specimen. The advantages and limitations of the proposed technique are shown.

In this paper a distributed intelligent system for civil engineering structures on-line measurement, remote monitoring, and data archiving is presented. The system consists of a set of full-field optical displacement sensors connected to a controlling server. The server conducts measurements according to a list of scheduled tasks and stores the primary data or initial results in a remote centralized database. The description of an exemplary set of full-field sensors including IP and thermovision camera, 2D and 3D digital image correlation systems, and grating interferometry based extensometers is provided. Three different measurement tasks performed by means of this systems are presented in details.