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Mosayebi, Mahshad. "Digital Laser Speckle Image Correlation." OpenSIUC, 2017. https://opensiuc.lib.siu.edu/theses/2131.
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This thesis examines the feasibility of combining Digital Image Correlation (DIC) with laser speckle based methods to form a new hybrid deformation measurement method called Digital Laser Speckle Image Correlation (DilSIC). Consequently, this method does not require any sample preparation and allows for the measurement of displacement of micro structures in addition to large displacements. In this technique, a coherent 30mW-632nm laser beam is expanded with 40X lens and then illuminated on the target surface to produce a fine, homogenous laser speckle pattern. Images were captured before and after deformation due to external load and the whole field displacement and strain were determined by the DIC method. This technique could measure displacement less than 30-μm with high accuracy when a 120mm × 80mm area of the surface was inspected. Up to 10% strain was measured by this technique with high accuracy during the whole range. Eventually the sub-surface crack was located successfully, which is a revolutionary achievement in NDT optical methods. This method was tested in different material, with different roughness. Aluminum sheet and rubber material were used mostly. This method could broaden the capability of displacement measurement and subsurface crack detection in wide range of materials.
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Newberry, Shawn. "Laser Speckle Patterns with Digital Image Correlation." OpenSIUC, 2021. https://opensiuc.lib.siu.edu/theses/2885.
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Digital Laser Speckle Image Correlation (DiLSIC) is a technique that utilizes a laser generated speckle pattern with Digital Image Correlation (DIC). This technology eliminates the need to apply an artifact speckle pattern to the surface of the material of interest, and produces a finer speckle pattern resulting in a more sensitive analysis. This investigation explores the parameters effecting laser speckle patterns for DIC and studies DiLSIC as a tool to measure surface strain and detect subsurface defects on pressure vessels. In this study a 632.8 nm 30 mW neon-helium laser generated the speckle pattern by passing through the objective end of an objective lens. All experiments took place in a lab setting on a high performance laminar flow stabilizer optical table.This investigation began with a deeper look at the camera settings that effect the effectiveness of using laser speckles with DIC. The first studies were concentrated on the aperture size (f-stop), shutter speed, and gain (ISO) of the camera. Through a series of zero-correlation studies, translation tests, and settings studies, it was discovered that, much like white light DIC, an increased gain allowed for more noise and less reliable measurements when using DiLSIC. It was shown that the aperture size and shutter speed will largely depend on the surface composition of the material, and that these factors should be investigated with each new sample of different surface finish.To determine the feasibility of using DiLSIC on pressure vessels two samples were acquired. The first was a standard ASTM filament wound composite pressure vessel (CPV) which had an upper load limit of 40 psi. The second was a plastic vessel that had internal subsurface defects added with the use of an air pencil grinder. Both vessels were put under a pressure load with the use of a modified air compressor that allowed for multiple loading cycles through the use of a pressure relief valve. The CPV was mapped out in 10-degree increments between the 90° and 180° markings that were on the pressure vessel, occurring in three areas, each one inch apart. The CPV had a pressure load applied to at 10, 20, 30,and 40 psi. DiLSIC was able to measure increasing displacement with increased loading on the surface of the CPV, however with a load limit of 40 psi no strains were detected. The plastic vessel had known subsurface defects, and these areas were the focus of the investigation. The plastic vessel was loaded with a pressure load at 5, 10, 12, 15, 17, and 20 psi. The 5 psi loaded image was used as a reference image for the correlation and decorrelation consistently occurred at 20 psi. This investigation proved that DiLSIC can detect and locate subsurface defects through strain measurement. The results were verified with traditional white light DIC, which also showed that the subsurface defects on pressure vessels were detectable. The DIC and DiLSIC results did not agree on maximum strain measurement, with the DiLSIC prediciting much larger strains than traditional DIC. This is due to the larger effect out-of-plane displacement has on DiLSIC. DiLSIC was able to detect subsurface defects on a pressure vessel. The median measured hoop strain was in agreement for DiLSIC, DIC and the predicted hoop strain for a wall thickness of 0.1 inches. However, DiLSIC also produced unreliable maximum strain measurements. This technique shows potential for future applications, but more investigations will be needed to implement it for industrial use. A full investigation into the parameters surrounding this technique, and the factors that contribute the most to added noise and unreliability should be conducted. This technology is being developed by multiple entities and shows promising results, and once further advanced could be a useful tool for rapid surface strain measurement and subsurface defect detection in nondestructive evaluation applications. Therefore, it is recommended to continue further investigations into this technology and its applications.
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Shih, YiChang. "Laser speckle photography for surface tampering detection." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/75686.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 59-61).
It is often desirable to detect whether a surface has been touched, even when the changes made to that surface are too subtle to see in a pair of before and after images. To address this challenge, we introduce a new imaging technique that combines computational photography and laser speckle imaging. Without requiring controlled laboratory conditions, our method is able to detect surface changes that would be indistinguishable in regular photographs. It is also mobile and does not need to be present at the time of contact with the surface, making it well suited for applications where the surface of interest cannot be constantly monitored. Our approach takes advantage of the fact that tiny surface deformations cause phase changes in reflected coherent light which alter the speckle pattern visible under laser illumination. We take before and after images of the surface under laser light and can detect subtle contact by correlating the speckle patterns in these images. A key challenge we address is that speckle imaging is very sensitive to the location of the camera, so removing and reintroducing the camera requires high-accuracy viewpoint alignment. To this end, we use a combination of computational rephotography and correlation analysis of the speckle pattern as a function of camera translation. Our technique provides a reliable way of detecting subtle surface contact at a level that was previously only possible under laboratory conditions. With our system, the detection of these subtle surface changes can now be brought into the wild.
by YiChang Shih.
S.M.
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Binder, Bradley Thomas 1960. "Laser radar tomography--the effects of speckle." Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/34312.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1991.Vita.
Includes bibliographical references (leaves 165-169).
by Bradley Thomas Binder.
Ph.D.
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Shilpiekandula, Vijay 1979. "A laser speckle based position sensing technique." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/27131.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.Includes bibliographical references (p. 129-131).
This thesis presents the design and development of a novel laser-speckle-based position sensing technique. In our prototype implementation, a He-Ne laser beam is directed at the surface of an air-bearing spindle. An imaging system is set up to capture speckle patterns scattered from the spindle surface. These patterns are highly correlated over small angular displacements of the spindle. We use correlation-based image-processing algorithms to measure offsets between the speckle patterns. These offsets are calibrated against the counts of a commercial incremental optical encoder. A custom-built bicell photointerrupter unit is used as a reference sensor for the incremental optical encoder. To test for the control performance of this speckle-based sensor, we have constructed a transmission drive to run the air-bearing spindle. Our speckle-based metrology system is able to run at update rates of 10 Hz with a measured closed loop -3 dB bandwidth of about 2 Hz. Using a real-time processor interfaced with a desktop PC, we have implemented a novel algorithm that interpolates position estimates with respect to two pre-stored global images. We predict that this technique can potentially achieve resolutions of 0.1 [mu]m for translational and 5 [mu]rad for rotational motion. The limitation of our current implementation is the low update rates resulting from the time-intensive nature of correlation-based methods. Possible methods to overcome this limitation are addressed and ideas for follow-on work are presented.
by Vijay Shilpiekandula.
S.M.
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Riechert, Falko. "Speckle reduction in projection systems." Karlsruhe Univ.-Verl. Karlsruhe, 2009. http://d-nb.info/997279346/04.
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Johansson, Louise. "Analysis of cartilage surfaces using laser speckle imaging." Thesis, Linköping University, Department of Biomedical Engineering, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-5830.
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An arthroscope is a diagnostic instrument for visualisation of the interior of a joint. By adding a laser to an arthroscope and feeding the images to a computer, one gets an method to measure the structure of the cartilage covering the joint. This gives an added diagnostic value. The laser will create laser speckles and this report covers the basic theories behind this. The anatomy of the joints, the properties of cartilage and the background on the disease arthritis are also covered, as well as the field of surface topography and image processing.
Experiments were performed on three different materials - metals of different definite surface roughness, polymerised collagen and bovine articular cartilage.
The conclusion is that the technique would work, providing that some obstacles could be overcome. The technique itself is very precise and detects nanometric differences in the surface structure, making it extremely interesting for research purposes, such as follow-ups on treatments and studies of arthritis and cartilage repair.
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Mo, Ning. "Mechanical characterisation of bone with laser speckle photography." Thesis, Queen Mary, University of London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339170.
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Martin, Peter. "Uncertainty due to speckle noise in laser vibrometry." Thesis, Loughborough University, 2010. https://dspace.lboro.ac.uk/2134/7139.
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This thesis presents fundamental research in the field of laser vibrometry for the application to vibration measurements. A key concern for laser vibrometry is the effect of laser speckle which appears when a coherent laser beam scatters from an optically rough surface. The laser vibrometer is sensitive to changes in laser speckle which result from surface motions not in the direction of the incident beam. This adds speckle noise to the vibrometer output which can be indistinguishable from the genuine surface vibrations. This has been termed ‘pseudo-vibration' and requires careful data interpretation by the vibration engineer. This research has discovered that measurements from smooth surfaces, even when no identifiable speckle pattern is generated, can produce noise and therefore reference to speckle noise, in such circumstances, is inappropriate. This thesis has, therefore, adopted the more general term of pseudo-vibration to include noise generated from any surface roughness or treatment, i.e. including but not limited to speckle noise. This thesis develops and implements novel experimental methods to quantify pseudovibration sensitivities (transverse, tilt and rotation sensitivity) with attention focussed on commercially available laser vibrometers and consideration is given to a range of surface roughnesses and treatments. It investigates, experimentally, the fundamental behaviour of speckles and attempts to formulate, for the first time, a relationship between changes in intensity to pseudo-vibration sensitivity levels. The thesis also develops and implements models for computational simulation of pseudo-vibrations using the fundamental behaviour of speckles. The combination of experimentation and simulation improves current understanding of the pseudo-vibration mechanisms and provides the vibration engineer with a valuable resource to improve data interpretation. Two experimental methods of quantifying pseudo-vibration sensitivity are developed and successfully applied in the evaluation of transverse, tilt and rotation sensitivity for two models of commercial laser vibrometer. These evaluations cover both single beam (translational vibration measurement) and parallel beam (for angular vibration measurement) modes. The first method presented requires correction of the vibrometer measurement with an independent measurement of genuine velocity to produce an iii apparent velocity dominated by the required noise components. The second method requires a differential measurement using two vibrometers to cancel common components such as genuine velocity, leaving only uncorrelated noise from each measurement in the resulting apparent velocity. In each case, a third measurement is required of the surface motion component causing pseudo-vibration and this is used to normalise the apparent velocity. Pseudo-vibration sensitivity is then presented as a map showing the spectral shape of the noise, as a mean and standard deviation of harmonic peaks in the map and as a total rms level across a defined bandwidth. The simulations employ a novel and effective approach to modelling speckle evolution. Transverse and tilt sensitivity are predicted for the first time and are verified by the experimental study. They provide the vibration engineer with the potential to estimate pseudo-vibrations using a simple piece of software. The laser beam spot diameter has a large influence on the pseudo-vibration sensitivity. Transverse sensitivity has been quantified as around 0.03% and 0.01% (per order) of the transverse velocity of the surface for beam spot diameters of 100 μm and 600 μm respectively. Larger beam spots have been shown to significantly reduce transverse sensitivity and measurements from smoother surfaces have also shown a reduced level of transverse sensitivity. Tilt sensitivity has been quantified at about 0.1 μms-1/degs-1 and 0.3 μms-1/degs-1 (per order) of angular velocity of the surface for beam spot diameters of 100 μm and 600 μm respectively. Smaller beam spot diameters significantly reduce tilt sensitivity. The surface roughness or treatment has been shown to have little effect on the level of tilt sensitivity. Rotation sensitivity has been quantified at approximately 0.6 μms- 1/rads-1 and 1.9μms-1/rads-1 (per order) of rotation velocity of the rotor for 90 μm and 520 μm. Smaller beam spot diameters have shown a significant reduction in rotation sensitivity and measurements on smoother surfaces have shown a reduced rotation sensitivity. Focussing the laser beam approximately on the rotation axis has also shown a significant reduction in rotation sensitivity. Parallel beam rotation sensitivity has been quantified at 0.016 degs-1/rads-1 and it is demonstrated that this can adequately be estimated using the single beam rotation sensitivity.
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Rothberg, Steven Joseph. "Laser speckle studies for vibration and torque measurement." Thesis, University of Southampton, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241481.
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Song, Lipei. "Endoscopic laser speckle contrast analysis for tissue perfusion." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/10923.
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Laser speckle contrast analysis (LASCA), as a method of measuring blood flow speed and tissue perfusion, is a full field imaging technique requiring simple configurations and data processing, which is important for the application in real time in vivo. But LASCA is sensitive to changes in environmental factors. The application in vivo is also limited to superficial detection due to the limitation of the light penetration depth. Therefore this thesis aims to develop an endoscopic LASCA system to extend the access to internal detection and explore the relationship between the contrast and experimental parameters. Firstly the relationship between the contrast and speckle size, flow mode, quantity of stationary scatterers and the signal intensity were investigated. Theoretical models for the relationship between the contrast and the mean intensity of the speckle pattern were deduced and the correction methods were introduced to correct the contrast bias due to the intensity difference. Then a flexible single wavelength endoscopic laser speckle contrast analysis system (ELASCA) was developed using a leached fibre image guide (LFIG). A Butterworth filter and defocus were used to remove the fibre pattern to retrieve the contrast images. This system and the data processing methods were used on a customized phantom demonstrating that this ELASCA system can detect the flow speed changes in an imaging domain. Afterwards a dual-wavelength ELASCA was developed for functional imaging of the blood circulation. The test on a human fingertip and rabbit uterine blood vessels show that this system can monitor the change of blood flow speed and the oxygen saturation introduced by occlusion, in addition to the cardiac pulse and respiration rate. Then a novel application of LASCA to visualize the ultrasound pressure field and the propagation of the shear wave is presented for the application of locating area of interest (AOI) and detecting tissue variation.
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Sun, Shen. "Laser Doppler imaging and laser speckle contrast imaging for blood flow measurement." Thesis, University of Nottingham, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.604304.
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The two blood flow imaging techniques, laser Doppler blood flow imaging (LDI) and laser speckle contrast blood flow imaging (LSCI), are well established and broadly applied in medical research. They are similar as both detect and process a fluctuating interference (speckle) pattem. However, the difference between processing algorithms provides different imaging characteristics. LDI can provide accurate, quantitative blood flow measurement which is seldom achieved by LSCI. Nevertheless, the fast imaging speed and simple instrumental setup provided by LSCI overcome some of the limitations ofLDI. With the development of high frame rate cameras full field LDI is now feasible and with the development of new processing algorithms LSCI is now providing more accurate quantitative information. It is therefore important to compare the performance of these two techniques. A full-field LDI system based on an FPGA (Field Programmable Gate Array) coupled with a high-speed CMOS (Complementary Metal-Oxide-Semiconductor) camera chip has been developed which provides blood flow images with flexible frame rates and spatial resolution. When a high spatial resolution is required, 1280xl024-pixel blood flow images were obtained by processing up to 2048 samples at O.2fps (frame per second). Altematively, a maximum of 15.5fps was achieved by reducing the resolution and sampling points to 256x256 pixels and 128 samples respectively. As a generic full-field LDI system, several parts of the system (memory unit, processing unit) can be simply updated or transplanted to another platform. The resource usage is optimized by utilizing a mixture of fixed and floating-pointing implementations, and the imaging speed is maximised because of the design of streamline structure which enables continuous input of data. Images were obtained of rotating diffusers at different rotation velocities and the system provides a linear relationship with velocity. Human blood flow images are also demonstrated both of the finger and of a healing wound. The author-designed LDI system was then applied to a high-spatial resolution flow imaging application in which the mixture of water and polystyrene micro spheres was pumped through a micropipette (diameter = 250llm) with controlled velocities, and the resulting flow was imaged and processed. The accurate, high-spatial resolution flow measurement was demonstrated by the resulting flow images which are of size 1280x 1 024 pixels and obtained by processing 2048 samples at each pixel. Besides the LDI system, a novel LSCI system has been developed on the same platform, establishing a unique LDI and LSCI hybrid system. By developing the LSCI method with equivalent exposures, the LDI data can be analysed using LSCl processing, enabling a truly fair comparison of these two methodologies. For comparison, measurements were carried out on a rotating diffuser that simulates the human tissue with controlled parameters. Although LDI and LSCI are qualitatively similar, the lack of quantitative blood flow measurement ofLSCI was recognized from the comparison since LSCI is exposure time dependent and unable to linearly detect the velocity changes. 11 To improve the linearity and accuracy ofLSCI measurement, multi-exposure laser speckle contrast imaging (MLSCI) has been introduced. However this increases image acquisition time as consecutive images at different exposure times need to be acquired. On the basis of the novel LSCI method, a new MLSCI scheme has been invented. The advantage of the MLSCI is that each frame is exposed with a fixed duration and various exposure times are alternatively achieved by accumulating several successive frames. In this way, the requirement to obtain a wide range of exposure times from consecutive images is overcome. This reduces image acquisition time as it depends on the longest exposure time rather than the sum of all exposures. From measurements of a rotating diffuser, the MLSCI was demonstrated to be capable of quantitatively measuring flow changes as in LDI. III
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Apeland, Knut Øyvind. "Reduction of speckle contrast in HDTV laser projection display." Thesis, Norwegian University of Science and Technology, Department of Electronics and Telecommunications, 2008. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-8943.
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Abstract In this thesis the focus has been on laser speckle. It is done in collaboration with poLight. They are developing a projector, where laser light is the source of illumination. In such projectors, laser speckle degrades the image quality. The aim of this project is to construct a speckle reduction device to be used in the laser projector. The theory covers a description of laser speckle, how to reduce the speckle contrast, and five methods to so. We explain why speckle arises and which parameters we can manipulate to reduce the speckle contrast. The five speckle reduction methods included in this thesis are; vibrating diffuser, slowly moving diffuser, Hadamard matrices, scattering tube, and vibrating mirror. Large vibrational motions are unwanted, considering the size of the device, generation of noise, and problems with alignment of the optical components in the projector that this would lead to. The quality of the laser beam is prominent in order to produce a sharp image, thus the use of diffusers with large scattering angles is not a good solution. The scattering tubes, designed by poLight, are tubes filled with micro pearls in a polymer gel. The size of the pearls decides the nature of the scattering. Larger pearls will give less back scattering and more light transmitted in the forward direction. If the tubes are rotated in a well balanced device we can avoid generating vibrations. The Hadamard matrices is the only one of the five methods which is not based on a motion. The challenge is to find a SLM to implement the matrices. It requires a low response time in order to present enough matrices during the exposure time of the eye. The laboratory setup we use to measure the speckle contrast is an improved version of the setup constructed in the specialisation project. A screen was removed from the old setup, and the speckle is now imaged directly from the speckle reduction device. The measured speckle reduction is thus due to the device alone, and not affected by the screen. The results were reproducible and in agreement with what we expected. We implemented a vibrating diffuser, both the single and the slowly moving. A piece cut from a plastic bag and some Scotch Magic tape were used as diffusers. The tape is the strongest diffuser and gives the lowest speckle contrast, however, it also has the largest scattering angle. The single tape diffuser reduced the speckle contrast to $C = 0.112$. With two tape difusers in series the intensity in the images becomes too low to exploit the dynamic range of the CCD sensor. The result is a higher calcualted speckle contrast with two diffusers, $C=0.131$, even though it ought to be smaller. We tested five prototypes of the scattering tube with different concentrations. The tube with the highest concentration has the highest speckle reduction abilities. It also has the strongest scattering effect. The scattering is less than with the tape diffuser, and so is the speckle reduction. The speckle contrast is reduced to $C=0.320$ when the tube is rotated, and to $C=0.389$ when it is vibrated. The tubes was also tested in series with a ground glass. The ground glass acted as a second diffuser. In this setting, vibration and rotation of the tubes reduced the speckle contrast equally, $C approx 0.283$ From the measured speckle contrast of the diffusers and tubes in stationary conditions, a polarization analysis should show a depolarization of the laser beam. This were the case only for the plastic diffuser. It is assumed that the error lays with the polarization analysis. There should be a depolarization in the tape and a partial depolarization in the tubes. A calculation of the speckle size was performed as well. Based on the theory we expected the size of the speckle grains to be $sigma_s = 37.77~mu m$. From the Fourier analysis of a speckle image from the setup we calculated the speckle size to be $sigma_s = 5.35$~mm, which is approximately 140 times bigger. The expected speckle size is too small, because we did not take into account a small magnification in the setup. The Fourier analysis of discrete and limited sets of data points is probably the main explanation of the difference, but a more thorough study is needed.
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Li, Sinan. "Laser speckle contrast detection of acoustic radiation force response." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/34931.
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Light and ultrasound are both non-ionizing radiations, ideal for biomedical applications. Recent studies on combining ultrasound and light for biomedical imaging show new promises in improving imaging quality and/or providing complementary imaging contrast. Among a variety of the imaging modalities that simultaneously use ultrasound and light, this work focuses on optical detection of tissue responses to acoustic radiation force (ARF). The applications include optical shear wave elastography and ultrasound modulated optical tomography. The first half of the thesis provides a systematic study on tracking shear waves in optical turbid media using CCD-based laser speckle contrast analysis. The theory, simulation and experiment are developed and cross-validated. The simulation quantitatively relates CCD speckle contrast signal with shear waves, providing useful information to understand the underlying physics. In addition, multiple shear waves are tracked using laser speckle contrast detection. Results show that two counter-propagating shear waves produce a modulation pattern in the optical signal, and the modulation pattern was suggested by simulation as a result of the dual shear wave interference. Shear wave speed measurements in phantoms suggest that the dual shear wave approach is more accurate than the single shear wave approach as that the standard deviation of the speed measurement is reduced by a factor of at least 2. The the dual shear wave approach also provides a reduced boundary effect. Both factors suggest that the dual shear wave approach should improve the accuracy of elasticity measurements. In the second half of the thesis, instead of detecting ARF response in the late phase, the study is motivated by detecting ARF response in the early stage for enhancement of ultrasound modulation of light. A pilot study on incorporating perfluorocarbon-based phase change contrast agent with ultrasound modulated optical tomography is explored. To understand the phase transition process, a quantitative measurement of acoustic nanodroplet vapourisation is developed. A preliminary result also showed that a single ultrasound burst can simultaneously vaporise the nanodroplets and sonify the converted microbubbles to provide additional ultrasound modulation of light. This additional light modulation was shown to increase the laser speckle contrast signal detected on a CCD camera.
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Miroshnikova, Natalia. "Investigation of laser drilling processing using Speckle Correlation techniques." Licentiate thesis, Luleå, 2004. http://epubl.luth.se/1402-1757/2004/030.
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Jiang, Shihong. "Non-scanning fluorescence confocal microscopy using laser speckle illumination." Thesis, University of Nottingham, 2005. http://eprints.nottingham.ac.uk/10139/.
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Confocal scanning microscopy (CSM) is a much used and advantageous form of microscopy. Although CSM is superior to conventional microscopy in many respects, a major disadvantage is the complexity of the scanning process and the sometimes long time to perform the scan. In this thesis a novel non-scanning fluorescence confocal microscopy is investigated. The method uses a random time-varying speckle pattern to illuminate the specimen, recording a large number of independent full-field frames without the need for a scanning system. The recorded frames are then processed in a suitable way to give a confocal image. The goal of this research project is to confirm the effectiveness and practicality of speckle-illumination microscopy and to develop this proposal into a functioning microscope system. The issues to be addressed include modelling of the system performance, setting up experiments, computer control and image processing. This work makes the following contributions to knowledge: * The development of criteria for system performance evaluation * The development of methods for speckle processing, whereby the number of frames required for an image of acceptable quality can be reduced * The implementation of non-scanning fluorescence confocal microscopy based upon separate recording of the speckle patterns and the fluorescence frames, demonstrating the practicality and effectiveness of this method * The realisation of real-time image processing by optically addressed spatial light modulator, showing how this new form of optical arrangement may be used in practice The thesis is organised into three main segments. Chapters 1-2 review related work and introduce the concepts of fluorescence confocal microscopy. Chapters 3-5 discuss system modelling and present results of performance evaluation. Chapters 6-8 present experimental results based upon the separate recording scheme and the spatial light modulation scheme, draw conclusions and offer some speculative suggestions for future research.
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Dunmeyer, David Richard 1978. "Laser speckle modeling for three-dimensional metrology and LADAR." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/16763.
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Thesis (M.Eng. and S.B.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2001.Includes bibliographical references (leaves 103-111).
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
In this thesis, I developed three-dimensional laser-speckle models to help in the development process of three-dimensional optical-metrology imaging systems. These models were developed to aid in the proof of concept for various three-dimensional metrology techniques. These models were then compared to real-world imaging systems, developed by both the author and other staff at the MIT Lincoln Laboratory, to determine their ability to accurately model said imaging systems. I also looked at the laser speckle statistics associated with mid-field systems in an exo-atmospheric environment as they relate to LADAR.
by David Richard Dunmeyer.
M.Eng.and S.B.
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Young, Anthony M. "Investigation of Laser Speckle Contrast Imaging's Sensitivity to Flow." Miami University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=miami153256524246362.
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Hinsdale, Taylor A. "Laser Speckle Imaging: A Quantitative Tool for Flow Analysis." DigitalCommons@CalPoly, 2014. https://digitalcommons.calpoly.edu/theses/1251.
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Laser speckle imaging, often referred to as laser speckle contrast analysis (LASCA), has been sought after as a quasi-real-time, full-field, flow visualization method. It has been proven to be a valid and reliable qualitative method, but there has yet to be any definitive consensus on its ability to be used as a quantitative tool. The biggest impediment to the process of quantifying speckle measurements is the introduction of additional non dynamic speckle patterns from the surroundings. The dynamic speckle pattern under investigation is often obscured by noise caused by background static speckle patterns. One proposed solution to this problem is known as dynamic laser speckle imaging (dLSI). dLSI attempts to isolate the dynamic speckle signal from the previously mentioned background and provide a consistent dynamic measurement. This paper will investigate the use of this method over a range of experimental and simulated conditions. While it is believable that dLSI could be used quantitatively, there were inconsistencies that arose during analysis. Simulated data showed that if the mixed dynamic and static speckle patterns were modeled as the sum of two independent speckle patterns, increasing static contributions led to decreasing dynamic contrast contributions, something not expected by theory. Experimentation also showed that there were scenarios where scattering from the dynamic media obscured scattering from the static medium, resulting in poor estimates of the velocities causing the dynamic scattering. In light of these observations, steps were proposed and outlined to further investigate into this method. With more research it should be possible to create a set of conditions where dLSI is known be accurate and quantitative.
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Draper, Douglas C. "Prediction and measurement of the unwrapped phase for speckle propagating in turbulence /." Full text open access at:, 1992. http://content.ohsu.edu/u?/etd,638.
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Saito, Edson Hiroshi. "Medição de tensões em componentes mecânicos utilizando a técnica ESPI." [s.n.], 2010. http://repositorio.unicamp.br/jspui/handle/REPOSIP/263913.
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Orientador: Auteliano Antunes dos Santos JuniorDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
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Resumo: A técnica ESPI, sigla em inglês - Electronic Speckle Pattern Interferometry -, ou ainda, Interferometria Eletrônica por Padrão de Speckle, surgiu em conseqüência do desenvolvimento da metrologia a laser, que possui como característica o chamado efeito speckle. Este efeito é o fenômeno óptico de interferência de ondas eletromagnéticas coerentes - que é o caso do Laser - que possibilita a geração de padrões de franjas de interferência, a partir das quais é possível medir o deslocamento de superfícies e posteriormente calcular as tensões e deformações. Por se tratar de uma metodologia não destrutiva e sensível a pequenos deslocamentos, essa metodologia tem se difundido na indústria para medição de Tensões em componentes mecânicos de formas complexas e como aplicação de apoio para outras técnicas como análise por Elementos Finitos. O objetivo deste trabalho é a aplicação da técnica ESPI em componentes mecânicos fazendo uso de uma metodologia através da qual seja possível estabelecer um procedimento de medição da tensão com confiabilidade. O desafio é estabelecer a adequada aplicação da ferramenta em ambiente industrial, onde há a interferência de ruídos, temperatura, vibração, além de uma adequação de equipamentos de ensaio que pode influenciar diretamente nos resultados de medições. A correta medição das tensões e deformações através de um ensaio não destrutivo e de rápido diagnóstico pode trazer diversos benefício, dentre os quais as cifras gastas em peças destruídas, tempo de medição e economia de mão-de-obra. Os resultados do presente trabalho são a determinação das variáveis influentes na aplicação do ESPI, levantamento das causas raízes dos problemas de medição e, a partir dessas informações, consolidar um procedimento padrão para aplicação em medição de tensões em componentes utilizando a técnica ESPI
Abstract: The ESPI technique - Electronic Speckle Pattern Interferometry - has emerged as a result of the development of laser metrology, which is characterized as the so-called speckle effect. This effect is an optical phenomenon of coherent electromagnetic waves interference - as Laser. It allows the generation of fringes interference from which it can be measured the displacement of surfaces and therefore calculated the stresses and strains. As a no-destructive methodology and being sensible to small displacements, it has being spread out in the industry by measuring Stress and Displacements in complex mechanical components and as a support to Finite Elements Analysis (FEA) and others techniques. The objective of this work is the application of the ESPI technique testing mechanical components making use of a systematic methodology by which it will be able to establish a procedure for measuring stress with reliability. The challenge is to establish the application procedure in the industrial environment, where there are a lot of interferences like noises, temperature variation, vibration etc., besides the fact that the testing equipment to be adapted to static tests can influences in the results. The stress and displacements measurement in a nodestructive test and fast result diagnose can bring a lot of benefits in financial terms serving as a support tool for other testing procedures. The results from this project are the determination of main variables for ESPI application, establishment of root causes in measurements problems using ESPI, and hence consolidate a standard procedure for ESPI application in strain /stress measurement in mechanical components
Mestrado
Mecanica dos Sólidos e Projeto Mecanico
Mestre em Engenharia Mecânica
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Jakobi, Martin. "Laser speckle based surface measurement techniques relevant to fusion devices." [S.l. : s.n.], 2000. http://deposit.ddb.de/cgi-bin/dokserv?idn=960674144.
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Lifjeld, Anders. "Reduction of speckle contrast in laser based HDTV projection displays." Thesis, Norwegian University of Science and Technology, Department of Electronics and Telecommunications, 2007. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-9636.
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In this assignment the theoretical background for the nature of speckle is presented and practical work was done to reduce the speckle effect in a display system based on a laser source. This was done without any picture modulators, or any kind of line scan or flying spot scanning. Work was done to find the right setup to be able to as easy as possible characterize the statistics of the speckle in an image. A still image of an expanded laser spot worked as an image. A series of test sets were carried out to address the different factors which could make a difference on the speckle contrast and their role in such systems.
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LYLES, ALBERT Anthony. "AN ADVANCED APPROACH VERIFICATION TO DIGITAL LASER SPECKLE IMAGE CORRELATION." OpenSIUC, 2018. https://opensiuc.lib.siu.edu/theses/2458.
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This research project on the campus of Southern Illinois University Carbondale is an extension to the inquiry into the feasibility and reliability of the technology known as Digital Laser Speckle Image Correlation (DiLSIC). This is a hybrid approach of combining two existing technologies. The first being Digital Image Correlation (DIC) which is a nondestructive evaluation commonly used to find displacement, in-plane strain, as well as deformation. The second being the of laser speckle patterns. This hybrid has achieved level of resolution measured to be 3.4μ. DiLSIC increases the application ability of the DIC technique to situations that generally would not be an option to use. DiLSIC needs no artifact speckle patterns to be applied to the specimen as a preparation for nondestructive testing. In DIC testing, the surface of a specimen must artifact speckles applied to the subject surface. Often the application of artifact speckles is not desirable or possible. DiLSIC is an acceptable alternative to the previously discussed industry-wide practice. This method broadens the usage of the DIC technique to situations which previously were not possible. This technology can identify, quantify, and detect the distribution of strain and stress concentrations in composite structures. For this study, a honeycomb-backed glass fiber reinforced polymer (GFRP) panel from a Cessna aircraft exterior luggage door was obtained and a defect panel is created. The panel is constructed with one area containing a repair compliant with manufacturer standardized methods and a repair area is not compliant and consists of multiple incorrect repair steps. An area with no repair is also tested to act as a control for comparison and quantification. The results for the inspected areas showed a linear strain increase in the noncompliant repair. The data plot for the compliant repair showed a trend of following the same basic curve as the no repair area. A verification process follows the DiLSIC testing consisting of using Infrared Thermography, Air-coupled ultrasonic, and white light artifact speckle DIC. These tests show DiLSIC is a viable alternative to the testing that is available in the industry. DiLSIC can detect defect location, size, geometry and map strain to determine the difference between compliant and noncompliant repairs when compared to a base level non-repair area
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Montgomery, Paul C. "Forward looking innovations in electronic speckle pattern interferometry (ESPI)." Thesis, Loughborough University, 1987. https://dspace.lboro.ac.uk/2134/11756.
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Electronic Speckle Pattern Interferometry (ESPI) dates from 1971. Attempts at commercial exploitation were unsuccessful; at the beginning of this decade it remained essentially a laboratory technique. Problems arose from the practical operation of the instrument and the nature of the output. Correlation fringes are intrinsically noisy and their quality depends on many interrelated factors. It is shown that by simplifying the optical design and improving the quality of the optical components, the fringe contrast is greatly improved and the instrument is made easier to use. Extensions and improvements to the system are discussed: analogue image processing techniques as a low cost means of improving the appearance of the output; time invariant noise subtraction in time averaged fringes gives similar quality results as that of the subtraction mode; ensemble averaging of time variant noise is a new technique for producing holographic quality results. Electronic speckle contouring (ESC) gives a selection of methods for producing programmable contour spacings and orientations for shape measurement. ESPI is compared with other optical measurement techniques and is shown to have fundamental advantages.
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Huntley, J. M. "Laser speckle and its application to strength measurement and crack propagation." Thesis, University of Cambridge, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233260.
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The technique of laser speckle photography has been developed with the aim of measuring the strain field around the tip of a fast crack. An image processing system to allow automatic point-by-point analysis of a speckle photograph is described. The Young's fringes diffraction pattern, produced by directing a narrow laser beam through the photograph, is digitised and processed by computer. Two algorithms have been developed based on Fourier and Walsh spectral analysis. The system can measure speckle displacements with an accuracy of better than 0.1 μm. A new technique for measuring time-varying displacement fields by multiple exposure of a single photograph is presented. Results are shown from a five-exposure speckle photograph of a cantilever deformed under quasi-static conditions. Extension of the technique to dynamic problems requires a stroboscopic laser light source; one chapter deals with the development of a Q-switched ruby laser for this purpose. Modulation of the cavity losses with a Pockels cell at up to 1 MHz results in a train of short (~50 ns) light pulses at the modulation frequency. Results are presented from the analysis of speckle photographs of cracks in polymethylmethacrylate (PMMA) under quasi-static loading. Three different data analysis methods for estimating the stress intensity factor from the displacement field are proposed and evaluated. Preliminary results from dynamic crack propagation studies are described. The dynamic stress intensity factor is estimated from double exposure speckle photographs of fast cracks in PMMA, recorded with the ruby laser in double pulse mode. The application of the techniques of moire and high speed photography to the study of dynamic fracture is also discussed; results are presented from a sequence of moire photographs recorded at 5 x 105 frames s-1 . Further topics covered in the dissertation include a theoretical analysis of viscoelastic losses as a function of crack velocity, and strain-to-failure measurements on plastic bonded explosives in the Brazilian test using laser speckle photography.
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Iverson, Thomas Z. "Signature Stability in Laser Doppler Vibrometry." University of Dayton / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1497386740815576.
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Borbely, Luiz Alberto. "Medida de rugosidade por correlação angular de speckle." Universidade de São Paulo, 2005. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-14052014-160405/.
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Esse trabalho apresenta o método de correlação angular de speckle. Esse método foi melhorado para ser aplicado na medição de rugosidade na faixa de 30 m a 0,1 m. Um programa de computador foi desenvolvido para processar imagens e calcular a correlação angular, e novas fórmulas matemáticas foram deduzidas.This work presents the speckle pattem angular correlation method. This method was improving to be applicable in the roughness measuring in the range of 0,1 m to 30 m. A software was developed to process image and to calculate the angular correlation, and new mathematical equations were formulating.
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Tullis, Iain David Charles. "The laser torquemeter and implications of speckle decorrelation on torque measurement." Thesis, Loughborough University, 2000. https://dspace.lboro.ac.uk/2134/12168.
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Torque measurement of a rotating shaft is a method of monitoring machine performance. Steady transmission of mechanical power from the prime mover to the load is vital to avoid gear and bearing wear, shaft fatigue failure, bearing and coupling failure and noise. Mean and fluctuating torque are fundamental quantities of interest. The laser torquemeter is capable of providing a non-contact measurement of time-resolved torque through a driven system. The laser torquemeter depends upon laser speckle produced from coherent light illuminating a diffuse object and the speckle pattern may be used in determining the angular position of a rotating object. When the object rotates the backscattered speckle pattern, which changes continuously but repeats exactly with every revolution, is sampled by a suitably positioned photo detector. The photo detector output signal is periodic and one period is recorded in memory as a reference and the angular position of a shaft can then be determined by a comparison of this recorded reference signal with the current photo detector output signal. The speckle pattern from two axially separated points on the shaft are monitored and under low or, ideally, zero torque the photo detector outputs are recorded into the laser torquemeter electronics. The laser torquemeter then tracks the live photo detector output and determines the angle at the two points on the shaft. Relative angular displacement in the two angle outputs appears when torque is applied and the shaft twists. When the shaft is displaced, for example by vibration, the backscattered speckle pattern changes on the photo detector and the similarity between the recorded, reference signal and the live, current signal is reduced. In this thesis, the cross-correlation of the real-time photodetector output signal and the recorded reference signal as a function of shaft position is examined. The effects of various shaft motions - rotation, axial translation, pitch and yaw, and radial translation are theoretically and experimentally examined and the results can then be used in the design of an optical head for the laser torquemeter. A review of the current torquemeter technology allows for discussion of the broad spectrum of typical torquemeter operating conditions. The optical head of the laser torquemeter may vary significantly for various torque measurement scenarios. A design procedure for the optical head of the laser torquemeter is summarised. The holy grail of torquemeter manufacturers is to produce a cheap, easy to use, robust, accurate, reliable and non-contacting torquemeter. The laser torque meter has great potential to meet these requirements.
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Mermelstein, Michael Stephen. "A large-scale three-dimensional imaging system based on laser speckle." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/38057.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1995.Includes bibliographical references (leaves 61-62).
by Michael Stephen Mermelstein.
M.S.
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Bergoënd, Isabelle. "Étude numérique des transitions statistiques circulaire et gaussienne du speckle laser." Toulouse, ISAE, 2008. http://www.theses.fr/2008ESAE0004.
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Le speckle est un phénomène interférentiel issu de l'interaction d'une onde cohérente avec une surface rugueuse. Dans un plan d'observation, il se présente comme un ensemble de tavelures. Devenu incontournable depuis l'invention du laser dans les années 1960 mais souvent considéré comme un bruit pour l'imagerie ou la métrologie en lumière cohérente, le speckle optique est néanmoins à l'origine de plusieurs techniques de mesure de déplacements ou de déformations par exemple. Le speckle peut être caractérisé par un ensemble de paramètres statistiques, le plus utilisé étant le contraste. Ces paramètres sont correctement modélisés dans le cas où les rugosités, supérieures à la longueur d'onde qui les éclaire, entraînent des déphasages complètement aléatoires et lorsqu'elles sont présentes en grand nombre de façon à permettre l'application du théorème de limite centrale. Le modèle de Goodman est alors applicable et le champ complexe est décrit comme une variable aléatoire circulaire et gaussienne. En-dehors de ce cas limite, les paramètres généralement utilisés pour décrire le speckle sont mal connus. Il existe en particulier des lacunes en ce qui concerne la transition vers les statistiques non gaussiennes dans le cas de rugosités moyennes à l'échelle de la longueur d'onde. La connaissance complète de ces données pourrait notamment permettre de prévoir l'impact du speckle dans les différentes configurations rencontrées expérimentalement. Cette thèse propose le calcul des paramètres statistiques du speckle par simulation numérique, en s'appuyant sur la génération de surfaces aléatoires et la propagation de Fresnel, sans hypothèse a priori si ce n'est la condition paraxiale. Le travail a abouti à la description complète des transitions circulaire et gaussienne et à l'étude du couplage de ces deux transitions. D'une part, les résultats permettent d'affiner la compréhension des propriétés du champ diffusé et de sa dépendance à la rugosité et à la configuration d'éclairage, d'un point de vue purement géométrique, à partir d'une surface modélisée à l'aide de deux paramètres: l'écart-type des hauteurs et la longueur de corrélation. D'autre part, ils complètent les données disponibles sur les statistiques du speckle et permettent d'envisager une méthode de caractérisation statistique des surfaces rugueuses. Ce travail pourrait également ouvrir des perspectives d'optimisation de l'imagerie active par laser.
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Valdés, Escobar Claudia Patricia. "New laser speckle methods for in vivo blood flow imaging and monitoring." Doctoral thesis, Universitat Politècnica de Catalunya, 2014. http://hdl.handle.net/10803/285015.
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Blood flow and its regulation, as well as hemodynamics in general, are important for the health of tissues and hence the measurement of these quantities has many applications in research and clinical environments. Various optical techniques are attractive for the measurement of blood flow since they are often non- or minimally-invasive, continuous and are relatively inexpensive. During my PhD I have contributed to the monitoring of blood flow in experimental animal models with the construction of a multimodal device, based on laser speckle flowmetry and optical intrinsic signals, capable of measuring superficial microvascular cerebral blood flow, blood oxygenation and blood volume for translational research. This
device was applied in animal models of ischemic stroke and is flexible to be modified and used for other purposes. In doing so, I have developed new experimental methods and image processing protocols that allowed us to perform longitudinal studies where the animal can be removed from the device several times. Furthermore, this device has been used as a tool in a multi-disciplinary study to understand the role of the Mannose-binding lectin protein in reperfusion injury after an ischemic stroke in animal models. This then led to the main contribution of this work which is the development of the speckle contrast optical spectroscopy and tomography, a new non-invasive, optical technique for deep blood flow measurement that paves the way for deeper and three dimensional imaging of blood flow. This new method was first developed from a theoretical perspective. Then it was validated in tissue simulating phantoms and demonstrated to be feasible in measurements on the human arm muscle. Overall, these contributions will allow the development of cost-effective, non-invasive tomographic methods for the measurement of blood flow even in humans.El flujo sanguíneo y su regulación, así como la hemodinámica en general, son parámetros importantes para determinar el estado de salud de los tejidos; por esto, su medición tiene numerosas aplicaciones en los ámbitos clínico y de investigación. Varias técnicas ópticas resultan atractivas para la medición del flujo sanguíneo dado su carácter no invasivo o mínimamente invasivo, continuo y relativamente económico. Durante mi trabajo doctoral he contribuido a la monitorización del flujo sanguíneo, en modelos de experimentación animal, con la construcción de un dispositivo multimodo, basado en la flujometría de speckle láser (laser speckle flowmetry, LSF) y las señales ópticas intrínsicas (optical intrinsic signals, OIS), capaz de medir flujo sanguíneo de la microvasculatura superficial en el cerebro, oxigenación sanguínea y volumen sanguíneo en investigación traslacional. Este dispositivo fue aplicado en modelos animales de infarto cerebral; sin embargo, es flexible y puede ser modificado y utilizado para otros propósitos. Así pues, he desarrollado nuevos métodos experimentales y protocolos de procesamiento de imágenes que nos permitieron llevar a cabo estudios longitudinales, donde los animales pueden ser removidos del dispositivo en repetidas ocasiones. Adicionalmente, este dispositivo fue utilizado como herramienta en un estudio multidisciplinario para entender el papel de la proteína lectina de unión a la manosa (MBL) en las lesiones por isquemia-reperfusión después de un infarto cerebral en modelos animales. Este estudio, dio origen a la mayor contribución de este trabajo, siendo esta el desarrollo de la espectroscopía y tomografía óptica de contraste de speckle; una novedosa técnica óptica, no invasiva para medición de flujo sanguíneo profundo que allana el camino para la obtención de imágenes tridimensionales de flujo sanguíneo más profundo. Este nuevo método, se desarrolló primero desde una perspectiva teórica, y posteriormente se validó en phantoms de tejido biológico, demostrando su factibilidad en mediciones realizadas en el músculo del antebrazo de un paciente. En general, estas contribuciones permitirán el desarrollo de métodos tomográficos, no invasivos y rentables para la medición de flujo sanguíneo, extensibles incluso a seres humanos
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Harvey, David. "Automatically phase-locked fibre optic electronic speckle pattern interferometry using laser vibrometry." Thesis, Heriot-Watt University, 1996. http://hdl.handle.net/10399/715.
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Karlin, Joseph H. (Joseph Howard). "3D imaging methods for manufacturing, with emphasis on the laser speckle technique." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/38074.
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Hecht, Nils Nicholas [Verfasser]. "Untersuchungen zum zerebralen Kollateralgefäßwachstum und intraoperativen Laser Speckle Imaging / Nils Nicholas Hecht." Berlin : Medizinische Fakultät Charité - Universitätsmedizin Berlin, 2016. http://d-nb.info/1112553061/34.
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Valdés, Escobar Claudia Patricia. "New laser speckle methods for in vivo blood flow imaging and monitoring." Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM4367/document.
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Le débit sanguin et sa régulation sont des indicateurs importants de la santé des tissus. Leur mesure a de nombreuses applications en recherche fondamentale et clinique. Certaines techniques optiques constituent un moyen intéressant pour la mesure du débit sanguin, car en général elles sont peu invasives et relativement abordables car elles utilisent des systèmes d'illumination continus. Pendant ma thèse, j'ai contribué au développement de techniques de suivi de la circulation sanguine dans des modèles animaux avec la construction d'un dispositif multimodal basé sur la fluxmétrie laser et sur l'imagerie des signaux optiques intrinsèques, capable de mesurer les paramètre hémodynamiques microvasculaire au niveau superficiel du cerveau. Ce dispositif, testé sur des modèles animaux d'accident vasculaire cérébral, est adaptable et peut être utilisé à d'autres fins. En parallèle, j'ai mis au point des nouvelles méthodes expérimentales et des protocoles de traitement d'images qui ont permis de réaliser des études longitudinales. En outre, ce dispositif a été utilisé dans une étude multidisciplinaire pour comprendre le rôle d'une protéine impliquée dans le cas de lésions de reperfusion après un accident vasculaire cérébral ischémique dans des modèles animaux. Ma contribution majeure réside dans le développement de l'imagerie de contraste de speckle spectroscopique et tomographique, nouvelle technique d'imagerie 3D non invasive pour la mesure du débit sanguin en profondeur. Dans l'ensemble, ces contributions permettront le développement de méthodes tomographiques non invasives rentables pour la mesure du débit sanguin chez l'hommeBlood flow and its regulation are important for the health of tissues and its measurement has many applications in research and clinical environments. Optical techniques are often attractive for the non- or minimally-invasive, continuous and relatively inexpensive measurement of blood flow. This work contributes to the monitoring of blood flow in translational research with the construction of a multimodal device, based on laser speckle flowmetry and optical intrinsic signals, capable of measuring superficial microvascular cerebral blood flow, blood oxygenation and blood volume. This device was applied in animal models of ischemic stroke and is flexible to be modified and used for other purposes. In doing so, I have developed new experimental methods and image processing protocols that allowed us to perform longitudinal studies where the animal can be removed from the device several times. This device has also been used to elucidate the role of the Mannose-binding lectin protein in reperfusion injury after an ischemic stroke in animal models. This led to the main contribution of this work: the development of the speckle contrast optical spectroscopy and tomography, a new non-invasive, optical technique for deep blood flow measurement that paves the way for deeper and three dimensional imaging of blood flow. This new method was first developed from a theoretical perspective. Then it was validated in tissue simulating phantoms and demonstrated to be feasible in measurements on the human arm muscle. Overall, these contributions will allow the development of cost-effective, non-invasive tomographic methods for the measurement of blood flow even in humans
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Silva, Danilo Mariano da. "Desenvolvimento de métodos para a geração e controle da emissão em lasers aleatórios e speckle." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/85/85134/tde-22082016-151450/.
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Neste trabalho serão apresentados novos métodos baseados na geração e controle de comprimento de onda em lasers aleatórios e lasers de diodo. Na primeira parte do trabalho será demonstrado um laser aleatório com realimentação localizada em filmes em biopolímeros dopado com corante. O filme é constituído por um ácido desoxirribonucleico e cloreto de cetiltrimetilamônio (DNA-CTMA) dopado com DCM. No dispositivo proposto, a realimentação óptica para o laser aleatório é dada por centros de dispersão posicionados aleatoriamente ao longo das bordas da área ativa. Os elementos de dispersão são nanopartículas de dióxido de titânio (TiO2) ou defeitos aleatórios na interface entre o polímero ativo e ar. Diferentes espectros de emissão são observados, dependendo da geometria da área excitada. Um único ressonador aleatório com dimensões de 2.6 x 0.65 mm2 foi fabricado com emissão aleatória com realimentação obtida pela excitação do dispositivo por completo. A segunda parte deste trabalho apresenta um novo método para a geração e manipulação de franjas de contorno por meio de interferometria speckle com comprimento de onda sintética, usando um único laser de diodo com cavidade externa. A cavidade externa permite sintonizar duas emissões simultaneamente, o que por sua vez muda o intervalo entre as franjas de contorno do interferômetro, além de aumentar a estabilidade do laser. Uma análise de Fourier é proposta como alternativa para medir o comprimento de onda sintético resultante das duas emissões do laser.In this work, a new method is presented based on generating and controlling the wavelengths emitted by diode lasers and random lasers. In the first part of this work, resonant feedback random lasing from dye-doped biopolymer films is reported, consisting of a deoxyribonucleic acid and cetyltrimethylammonium (DNA-CTMA) complex doped with DCM dye. In the device, the optical feedback for random lasing is given by scattering centers randomly positioned along the edges of the active area. Scattering elements are either titanium dioxide nanoparticles or random defects at the interface between active polymer and air. Different emission spectra are observed, depending on the geometry of the excited area. A single random resonator with dimensions of 2.6 mm x 0.65 mm is fabricated and random emission with resonant feedback is obtained by uniformly pumping the full device. The second part of this work presents a new method for generating and manipulating contour fringes produced with a single external cavity diode laser in a multi-wavelength speckle interferometer. The external cavity allows tuning two simultaneous emissions, which in turn changes the contour interval of interference fringes and also improves laser stability. A Fourier analysis is applied as an alternative method for acquiring the resulting synthetic wavelength from both emissions.
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Koshoji, Nelson Hideyoshi. "Detecção de erosão dental utilizando análise de espalhamento de luz coerente - speckle." Universidade Nove de Julho, 2014. http://bibliotecadigital.uninove.br/handle/tede/1315.
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Dental erosion is a non-carious cervical lesion that is related to progressive tooth loss through its contact with chemicals that dissolve the enamel hydroxyapatite crystals. Currently, it is a highly prevalent condition among individuals of all ages. The loss of the structure of this tissue causes changes in the roughness of the surface. The objective of this work is to develop a methodology to identify and quantify this injury, in a non-invasively and non-destructive way, with low cost and executed in real time by analyzing the coherent light scattering patterns, called speckle. It was used 32 samples of bovine incisors and they were divided into 4 groups with different times of acid etching. Half of each sample was protected and then immersed in Coke (pH ≅ 2.5) for 10, 20, 30 and 40 min, twice daily and for 7 consecutive days. Each sample has two areas: half healthy and half eroded. After the challenge, the samples were submitted to speckle analysis to find the relative differences between the two regions in each group. It was found 10 min with 18% 20 min with 24% 30 min with 38% and 40 min with 44% of relative difference. After this analysis, we performed also a Knoop hardness test in order to compare methods. There was a linear trend between the methods with coefficient r = 0.80. The speckle image is proportional to the attack time, has a strong correlation and a good agreement with the Knoop hardness test.
A erosão dental é uma lesão cervical não cariosa que está relacionada a perda progressiva do dente através do seu contato com substâncias químicas que dissolvem os cristais de hidroxiapatita do esmalte. Atualmente, é uma condição altamente prevalente entre indivíduos de todas as idades. A perda da estrutura deste tecido provoca alterações na rugosidade de sua superfície. O objetivo deste trabalho é desenvolver uma metodologia que identifique e quantifique essa lesão de forma não invasiva, não destrutiva, com baixo custo e executado em tempo real através da análise dos padrões de espalhamento da luz coerente, denominado speckle. Foram utilizadas 32 amostras de incisivos bovinos e dividida em 4 grupos com diferentes tempos de ataque ácido. Metade de cada amostra foi protegida e, em seguida, imersas em coca-cola (pH ≅ 2,5) durante 10, 20, 30 e 40 min, duas vezes ao dia e 7 dias consecutivos. Cada amostra possui duas áreas: metade saudável e metade erodida. Após o desafio, as amostras foram submetidas à análise speckle para encontrar as diferenças relativas entre as duas regiões de cada grupo. Foi encontrado 10 min com 18%, 20 min com 24%, 30 min com 38% e 40 min com 44% de diferença relativa. Após esta análise, foram realizados, também, o teste de dureza Knoop afim de comparar os métodos. Houve uma tendência linear entre os métodos com coeficiente r = 0.80. A imagem speckle é proporcional ao tempo de ataque, possui uma forte correlação e uma boa concordância com o teste de dureza Knoop.
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Müller, Marc Michael [Verfasser]. "Laser Speckle Imaging zur kontinuierlichen intraoperativen Messung des zerebralen Blutflusses / Marc Michael Müller." Berlin : Medizinische Fakultät Charité - Universitätsmedizin Berlin, 2014. http://d-nb.info/1052020585/34.
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Hariri, Karim [Verfasser]. "Bruchmechanisches Verhalten jungen Betons : Laser-Speckle-Interferometrie und Modellierung der Rißprozeßzone / Karim Hariri." Braunschweig : Technische Universität Braunschweig, 2019. http://d-nb.info/1231992328/34.
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Silva, Danilo Mariano da. "Interferometria speckle com lasers de diodo multimodo para análise de materiais e dispositivos." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/85/85134/tde-26082011-100013/.
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Neste trabalho foi desenvolvido um novo método voltado para a caracterização de lentes térmicas em materiais fotônicos, utilizados como meios ativos no desenvolvimento de lasers. Este método baseia-se em interferometria por padrão de speckle eletrônico (ESPI), utilizando dois lasers de diodo multímodo sintonizados a diferentes freqüências. Com o ajuste desta diferença, foi possível escolher uma resolução apropriada para medirmos as variações geradas no raio de curvatura da frente de onda, relacionados ao efeito térmico. Para os nossos experimentos escolhemos uma amostra vítrea de aluminato de cálcio dopado com 4% de érbio; e potências de bombeio incidentes de até 1,76 mW do laser de bombeio. Os lasers de diodo foram sintonizados para ter um intervalo de contorno por volta de 120 m. Com o aumento da potência absorvida pela amostra, observamos a diminuição da curvatura da frente de onda incidente na CCD, devido ao aumento da potência da lente térmica gerada. Através de uma análise paraxial dos feixes, foi feita uma aproximação para obtermos os valores das lentes para cada configuração, apresentando comprimentos focais de 131,39 mm a 42,76 mm.In this work we will develop a new method focused on the caracterization of thermal lenses effect in photonic materials used as active media in lasers design. This method is based on electronic speckle pattern interferometry (ESPI) using two multimode diode lasers tuned to different frequencies. Adjusting this difference we can achieve an appropriate resolution to measure the variability generated within the curvature radius of the wavefront due to thermal lens effect. For our experiments we chose a vitreous sample of calcium aluminate doped with 4% erbium and incident pump powers ranging to 1.76mW. The diode lasers were tuned to have a contour interval of around 120m. With addition in power absorbed by the sample, we observed a decrease in the curvature radius incident on the camera due to increased power of the thermal lens generated. Through a paraxial of the wavefront, an approach was made to obtain the values of the lenses for each configuration, with focal lengths ranging from 131.39 mm to 42.76 mm.
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Enes, Adilson Machado. "Análise de frequência do biospeckle laser aplicada ao mapeamento de fenômenos em sementes de feijão (Phaseolus vulgaris l.)." [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/256881.
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Orientadores: Inacio Maria Dal Fabbro, Roberto Alves Braga JúniorTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Agrícola
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Resumo: O biospeckle laser é um fenômeno óptico de interferência que ocorre quando há incidência de luz coerente em um material biológico que exibe algum tipo de atividade. Essa atividade pode ser decorrente de processos biológicos ou de fatores puramente físicos, como a evaporação e a vibração ambiental. O conjunto de elementos físicos e biológicos que alteram o padrão de interferência do biospeckle laser é constituído por diversos elementos. Atualmente, diversas técnicas de processamento de imagens tem sido empregadas para quantificar o nível de atividade de materiais biológicos e correlacionar esses níveis com padrões de qualidade. No entanto, as técnicas empregadas até o momento para analisar sementes por meio do biospeckle laser não conseguem diferenciar os diversos elementos de forma satisfatória. A diferenciação desses elementos é de fundamental importância para o aproveitamento do fenômeno em aplicações reais, tais como a análise de viabilidade e vigor de sementes. Essa diferenciação possibilitaria a elaboração de procedimentos de análise rápidos, automáticos, objetivos e não destrutivos. Entre os elementos de grande relevância para a análise de sementes estão os danos físicos, que podem ser decorrentes de impacto durante o manejo, de ataques de insetos, entre outros e, normalmente, provocam na semente áreas com atividade biológica reduzida. Por outro lado, uma semente pode conter áreas infestadas por fungos e microrganismos diversos, sendo que essas áreas, no geral, constituem áreas de alta atividade biológica. A fundamentação teórica do biospeckle laser permite supor que seja possível identificar e mapear os fenômenos decorrentes da atividade biológica em sementes, inserindo no processamento das imagens, técnicas de análise de frequência como a Transformada de Wavelets (TW). Desta forma, este trabalho teve como objetivo principal verificar a potencialidade da TW aplicada ao sinal do biospeckle laser, para identificar e mapear fenômenos de atividades em sementes de feijão (Phaseolus vulgaris L.). Para a aquisição dos dados foram utilizados uma câmera monocromática, uma câmera digital, um emissor laser HeNe vermelho de 632 nm e 10 mW de potência e um emissor laser de diodo de 632 nm e 5 mW de potência. Para aferir os resultados foi utilizado o teste padrão de Tetrazólio (TZ). Utilizando as técnicas mencionadas, foram gerados mapas digitais de atividade, sendo esses comparados com os resultados do TZ. Os resultados mostraram que o mapeamento pela TW são capazes de identificar danos naturais e mecânicos em sementes de feijão. Os danos térmicos provocados artificialmente também são identificados, bem como as atividades decorrentes de reações químicas superficiais. A técnica de filtragem por TW apresenta grande potencialidade na identificação de fenômenos de baixa e alta atividade nas sementes de feijão (Phaseolus vulgaris L.) e, seus resultados, podem ser correlacionados com danos e contaminações
Abstract: The laser biospeckle is an optical interferometric phenomena that occurs when an incident light insides on an active biological material surface. The material activity can be originated from biological processes or even from some isolated physical phenomena. It does exist a group of components in a biological material which can change the biospeckle interference pattern. Many images processing techniques have been employed to quantify the activity level of a biological material and to correlate it with quality patterns. However, the techniques employed at this time for to quantify activity level and to evaluate seed quality, can not be employed to identify the components with acceptable accuracy. However, the identification and differentiation of these components is of fundamental importance to technique development applicable to a variety of situations as seed viability analysis, seed vigor, generating quick and non destructive, as well as capable of automation methods. Physical damages occurring by impact during product handling, insect attack and others do generate zones of low biological activities. By other side, seeds can exhibited zones attacked by fungi and other microorganisms holding high biological activities. Theoretical considerations support the possibility of identifying as well as mapping the phenomena originated from biological activities in seeds by inserting Wavelets Transform (TW) and Frequency Analysis in the image processing. Based on what it has been exposed before, the objectives of this research work can be summarized as to verify the potentiality of the Wavelets Transform (TW) applied to the laser biospeckle signal in indentifying and mapping phenomena associated to activities in seeds of Phaseolus vulgaris, L. The experimental setup included a monochromatic camera, a digital camera, a 632 red and 10 mW powered HeNe laser and a diode 632 nm and 5 mW powered. A tetrazolium (TZ) test was employed as a pattern test. The above described procedure generated digital maps of activity which were compared with the TZ. Results showed that the technique are able of identifying natural and mechanical bruising beans seeds. Artificialy generated thermal and chemical damages were identified as well. TW filtering techniques exhibits significant potentiality in indentifying high and low activities in beans seeds (Phaseolus vulgaris, L.) that can be correlated to damages and contaminations
Doutorado
Maquinas Agricolas
Doutor em Engenharia Agrícola
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Guedes, Guelton Hirano. "Estudo experimental do processo de oxidação utilizando a técnica de correlação óptica Speckle." Universidade de São Paulo, 1990. http://www.teses.usp.br/teses/disponiveis/43/43133/tde-29042014-121858/.
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Quando um objeto, capaz de difundir luz, e iluminado por uma frente de onda coerente, por exemplo, um feixe laser, da origem a uma estrutura granular que recebe o nome de granulado óptico ou padrão de speckle. Este padrão está diretamente ligado a estrutura microscópica do objeto espalhador. Neste trabalho e descrito o estudo experimental do fenômeno de oxidação metálica utilizando a técnica de correlação óptica de speckle em tempo real. Este trabalho apresenta as seguintes partes: - descrição do fenômeno de speckle. Um objeto difusor, ao ser iluminado por uma luz coerente, gera ondas secundarias de fases aleatórias em sua superfície. Estas ondas interferem entre si, produzindo um aspecto granular no espaço livre, com propriedades estatísticas bem definidas. Faz-se uma descrição do fenômeno de granulado óptico e de suas propriedades estatísticas. - Técnica de correlação óptica de speckle. Variações físicas de uma amostra resultam em alterações no seu padrão de speckle. Ao comparar os padrões em instantes distintos, pode-se detectar tais variações e quantifica-las. Descreve-se o método de correlação óptica utilizando o registro de um padrão em uma placa fotográfica de alta resolução, e discute-se a técnica de digitalização de imagens como um sistema eletrônico, alternativo, para registro e comparação de imagens em tempo real. -o fenômeno de oxidação à temperatura ambiente. A corrosão metálica é, à temperatura ambiente, um processo espontâneo, que varia de acordo com o material e com as condições ambientais. E discutido teoricamente o fenômeno de formação de camadas de óxidos sobre superfícies metálicas e são citadas algumas técnicas, com as quais são medidas determinadas variáveis envolvidas neste processo. -Verificação do fenômeno de oxidação utilizando a técnica de correlação óptica. Como o padrão de \"speckle\" está diretamente ligado às características superficiais da amostra, e sendo a oxidação um fenômeno superficial, torna-se possível detectar a formação de camadas de óxidos, em tempo real, utilizando a técnica de correlação óptica de \"speckle\". Descreve-se o método experimental utilizado, mostrando os dados obtidos com diversos tipos de metais, tratados ou não com substâncias inibidoras e corrosivas. Os resultados são comparados com aqueles obtidos através de outras técnicas cujos resultados são apresentados na literatura.When a diffusing object is illuminated by a coherent wavefront like a cw laser, it is created a granular phenomenon called \"speckle pattern\", which carries information about the microscopic structure of the scattering object. In this work the experimental study of the metallic oxidation phenomenon is described using the real time measurements by speckle optical correlation technique. This work is divided in: -The description of the speckle phenomenon. When a diffusing object is illuminated by coherent light it generates secundary random phase wavefronts in its surface. These wavefronts interfere creating a granular appearance in the space with well known statistical properties. The speckle phenomenon and its statistical properties are presented. -The speckle optical correlation technique. Physical variations of a sample result in changes in its speckle pattern. These variations can be detect by comparing the speckle patterns in distinct instants. The optical correlation method is described using register of a pattern in a high resolution photographic plate. Besides the image digitalization technique is presented as an alternativa electronic real time registering and comparing system. -The oxidation phenomenon at low temperatures. Metalic corrosion is a spontaneous process at low temperatures, and varies according to the material and surrounding conditions. The formation of oxide layers on metalic surfaces is theoretically described, and some techniques for measuring its parameters are presented. -The study of the oxidation phenomenon by optical correlation technique. As speckle pattern is related to the surface characteristics of the sample and since oxidation is a surface phenomenon, i t is therefore possible to detect the real time formation of oxide layers using the speckle optical correlation technique. The experimental method is described and obtained data are presented for several kinds of metals and alloys, using or not inhibitory or corrosive substances. The results are compared with those obtained from other techniques presented in the references.
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Vaz, Pedro Guilherme. "Étude de signaux laser speckle : méthodes pour la mesure de paramètres hémodynamiques de la microcirculation et de la macrocirculation." Thesis, Angers, 2016. http://www.theses.fr/2016ANGE0041/document.
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Le speckle laser est un effet d'interférence longtemps considéré comme néfaste lors de l'utilisation de sources de lumière cohérente. Cependant, pour certaines applications, cet effet peut être bénéfique et utilisé comme source d'information. C’est le cas du domaine biomédical.Ainsi, le speckle laser est utilisé depuis des décennies pour la surveillance du flux sanguin microvasculaire. Il commence à être considéré aussi pour l'extraction de paramètres de la macrocirculation sanguine. Ce travail vise donc tout d’abord à démontrer que le speckle laser permet d'évaluer les paramètres hémodynamiques de la macrocirculation avec fiabilité et à partir d’une technique identique à celle employée dans l’étude de la microcirculation. Ceci conduira à une intégration rapide du dispositif dans les instruments existants. Par ailleurs, l'un des problèmes les plus importants du speckle laser,empêchant l’obtention d’une analyse totalement quantitative, est l'effet des diffuseurs statiques. Ce type de diffuseurs influence fortement le contraste de speckle, conduisant à une mauvaise interprétation des données. Le second objectif de ce travail est donc d'étudier l'effet des diffuseurs statiques sur la corrélation et le contraste du speckle laser. Nos résultats montrent tout d’abord que le speckle laser est un phénomène intéressant pour extraire les paramètres hémodynamiques de la macrocirculation. Par ailleurs, nos études révèlent que le calcul de la corrélation du speckle laser permet d'estimer le rapport entre diffuseurs statiques / dynamiques avec une bonne fiabilité. En outre, le contraste temporel permet de déterminer les diffuseurs dynamiques possédant des vitesses différentesThe laser speckle is an interference effect that has been considered as a main drawback in the use of coherent light sources. However, for a specific set of applications, this effect can become a source of information. Among these applications there are the biomedical ones. The laser speckle has been used for decades to monitor microvascular blood flow but only now starts to be considered as a method that can also be used for macrocirculation parameters extraction. This work first aims at demonstrating that laser speckle can be used for macrocirculation assessment with good reliability, using the same technique as the one employed in microcirculation assessment. The use of the same methods could lead to a rapid inclusion of this new evaluation in the existing devices. Furthermore, one of the most important laser speckle issues, that prevents a fully quantitative analysis, is the effect of static scatterers. This type of scatterers strongly influences the speckle contrast, leading to a wrong interpretation of the data. The second objective of this work is to study the effect of statics catterers on the laser speckle correlation and contrast. Our results show that the laser speckle is an interesting phenomenon to extract hemodynamic parameters in the macrocirculation. This work also demonstrates that the laser speckle correlation is able to estimate the ratio between static/dynamic scatterers with good reliability. Moreover, the temporal speckle contrast achieved a very good performance in discerning dynamic scatterers with different velocities
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Sriram, P. "Whole field optical methods for structural mechanics : digital speckle correlation and laser Doppler velocimetry." Diss., Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/11751.
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Pickering, Christopher James Derwent. "The development of laser speckle metrology for the study of vibration and fluid flow." Thesis, University of Southampton, 1987. https://eprints.soton.ac.uk/52266/.
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Two original applications of laser speckle metrology are presented. First, a portable Laser Speckle Interferometer is described which allows the Engineer to simply point a laser beam at target surface in order to measure its vibration velocity amplitude and phase. This non-contacting capability complements an accelerometer where use of the latter is precluded; i.e. hot, light or rotating surfaces. The mechanisms which determine the noise floor of the interferometer are examined and minimisation procedures are defined. A prototype instrument is described which has a dynamic range of 60 dB over a frequency range of d.c. - 20 kHz which is adequate for general purpose use. Three applications are reported which exploit the non-contact capability of the instrument. Second, the application of Laser Speckle Photography to fluid flows is described and the development of an entirely new technique is introduced which is more appropriately named Particle Image Velocimetry (PIV). In PIV, the instantaneous two-dimensional velocity of a fluid flow is measured by taking a double-exposure photograph of a thin sheet of light within a seeded flow. Pointwise processing of the resulting transparency with a laser beam produces Young's fringes in the far field diffraction pattern whose spacing and orientation are measured to find the local fluid velocity within the illuminated region. It is shown both theoretically and by experiment, that the signal to noise ratio of these fringes and hence measurement accuracy, is significantly improved by using a two-step photographic process. In addition, it is shown that this process allows the use of more sensitive photographic films which reduce the laser power requirement and hence the cost of a PIV system. Two methods of fringe analysis are examined and it is shown that, by preprocessing the fringe pattern to remove the low frequency pedestal component, fringe spacing errors of less than 1% are achieved. It is also shown that this method significantly decreases the time required to measure fringe spacing when compared with conventional Fourier methods. In addition, a method of decreasing the overall time required to analyse an entire PIV transparency based on detection of the presence of particle images within the illuminated region is described.
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Sun, Libo. "The effect of optical spatial filtering on the statistics of laser radiation propagating through the turbulent atmosphere /." Full text open access at:, 1988. http://content.ohsu.edu/u?/etd,178.
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Eliès, Philippe. "Etude expérimentale de la dépolarisation en imagerie laser : classification d'échantillons, analyse du champ de speckle." Brest, 1996. http://www.theses.fr/1996BRES2046.
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Notre travail a permis de mettre au point une classification optique basee sur l'etude des transformations de polarisation apres reflexion sur les echantillons en imagerie active par laser. En effet lorsqu'une onde polarisee se reflechit sur une surface, elle peut subir des transformations polarimetriques diverses: un changement de polarisation par rapport a l'onde incidente, ou une depolarisation, ou encore une combinaison de ces deux phenomenes qui sont dependants de l'etat de surface et de la nature de l'echantillon. Nous avons donc etudie ces effets sur des echantillons de natures differentes, en utilisant le formalisme de stokes mueller. Nous avons utilise dans un premier temps un systeme imageur dit global en detection directe. Ce systeme prend en compte une image numerique et permet d'obtenir des informations a haute resolution spatiale, dans ce cas chaque pixel de la camera ccd integre un nombre important de grains de speckle etant donne l'ouverture importante du diaphragme de l'objectif. Cela revient a traiter le probleme comme en imagerie incoherente. Cette etude aboutissant a une classification de tous nos echantillons, nous nous sommes alors interesses a l'evolution de la depolarisation en detection directe sans systeme imageur devant le capteur ccd, chaque grain de speckle illuminant dans ce cas plusieurs pixels. Nous avons donc analyse la polarisation des grains de speckle, statistiquement puis grain par grain. Cette approche nous a permis d'analyser experimentalement les processus engendrant de la depolarisation
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Upadhyay, Debajyoti. "Imagerie polarimétrique adaptée en lumière cohérente." Thesis, Toulouse, ISAE, 2014. http://www.theses.fr/2014ESAE0007/document.
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Nous proposons dans cette thèse d’étudier une méthode d’imagerie qui s’adapte à la scène étudiée en utilisant des états polarimétriques choisis sur critères physiques pour optimiser le contraste polarimétrique en 2 zones aux propriétés polarimétriques différentes. En prenant en compte le bruit de Grenaille du détecteur, cette nouvelle technique d’imagerie à 2 canaux nommée APSCI montre un gain en contraste quantifié par la distance de Bhattacharyya pouvant atteindre un facteur 10 par rapport à l’imagerie de Mueller. D’autre part, elle utilise la totalité de l’information polarimétrique de la scène pour générer une seule image au contraste optimum ce qui la rend particulièrement performante pour distinguer deux zones aux propriétés polarimétriques légèrement différentes. La solution analytique complète de ce problème est proposée au chapitre suivant avec des illustrations associées. Le modèle proposé permet, en plus d’une interprétation physique, de quantifier les performances limites de la méthode APSCI en fonction des matrices de Mueller des 2 objets à discerner. Le chapitre suivant est consacré à l’étude des performances de cette méthode soumise au bruit optique de tavelure de cible. Les simulations numériques montrent que les performances de cette méthode en terme de contraste polarimétrique restent relativement robustes et souvent très supérieures à celles obtenues par l’imagerie de Mueller classique. Le dernier chapitre consiste à décrire l’implémentation expérimentale nécessaire à l’adaptation d’un imageur de Mueller en imageur APSCI en vue d’obtenir un imageur hybride Mueller/APSCI. La méthode APSCI nécessite de pouvoir utiliser en émission et en projection lors de la détectionWe propose in this thesis to study and imaging method which is adapted to the scene under investigation by the use of specific polarimetric excitations. The scenes under inversigation have two separate regions with different polarimetric properties. The specific fully polarized state of illumination is found by the physical criteria for oprimizing the polarimetric constrat in two aereas with different polarization properties. Taking into account the Shot noise of the detector, this new 2 channel imaging technique named APSCI, shows a gain in contrast quantified by the Bhattacharyya distance of up to a factor of 10 compared to what is achievable from classical Mueller imagnin. On the other hand, it uses the full polarimetric information of the scene to generate a single image at optimum contrast which makes it particularly effective to distinguish two distinct areas with slightly different polarization properties. The complete analytical solution of this problem is proposed in the next chapter with associated illustrations. The proposed model allows, in addition to a physical interpretation of the imaging problem, to quantify the limits of APSCI method based on evaluated Mueller matrices of the scene. Furthermore the relative performance of APSCI vs Classical Mueller Imaging (CMI) associated to polar decomposition has been studied numerically. Finally we have setup an hybrid CMI-APSCI imaging setup by indigenous calibration technique with a polarimetric precession of approximately 1% when room temperature varies around 1 degree C
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Brissonneau, Vincent. "Contrôle de la lumière par éléments de surface désordonnés." Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM4313.
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La diffusion électromagnétique par des surfaces rugueuses concerne un ensemble très vaste de problèmes actuels en optronique (maîtrise des signatures/cloaking, analyse des signatures laser et infrarouge, imagerie active, localisation de la lumière, imagerie optique haute résolution, modélisation des interactions lumière matière et des signatures optiques, applications photovoltaïques et détecteurs infrarouges, biotechnologie). Les travaux réalisés dans le cadre de la thèse "Contrôle de la lumière par des éléments de surface désordonnés'' consistent à réaliser expérimentalement des surfaces rugueuses dont les propriétés statistiques sont contrôlées. Pour cela, un banc expérimental de photofabrication a été développé, utilisant sles propriétés statistiques des figures de speckle issues d'un faisceau laser mis en forme spatialement.Les surfaces réalisées présentent ainsi des propriétés statistiques qui n'existent pas à l'état naturel (fonction d'autocorrélation non gaussienne). Au delà de ces surfaces photofabriquées, le travaux de cette thèse s'intéressent également aux propriétés de surfaces de silicium fortement rugueuses caractérisées de Black SiliconScattering of electromagnetic waves from rough surfaces is involved in a wide area of research in optronics (cloaking, laser and infrared signature analysis, active imaging, light localisation, high resolution optical imaging, laser-matter interaction and optical signature modelling, photovoltaics, infrared sensors, biotechnologies). Studies performed during the thesis ``Ligth control by random surface elements'' consist in the experimental fabrication of rough surfaces which statistical properties are controled. An experimental setup has been implemented, using the properties of a spatially shaped laser speckle pattern. The photofabricated surfaces show statistical properties that do not exist in nature such as non Gaussian autocorrelation function. Beyond these photofabricated surfaces, we also studied very rough surfaces of semi-conductor known as Black Silicon