Papers by Keyword: Laser Speckle

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Authors: Christophe Pradille, Michel Bellet, Yvan Chastel
Abstract: Strain field measurement with non intrusive techniques is needed in order to characterize the behaviour of steels at high temperatures subjected to small displacements. In this work we present a technique based on laser-produced speckles coupled with a cross-correlation cross-spectrum method. This method proves more accurate than cross-correlation for small displacements. The laser wave length used (532 nm) allows to perform strain measurements, even with heat radiation.
Authors: Rong Lu Zhang, Fu Sheng Yu, Tao Li, Bin Bin Jiao, Gui Lin Du
Abstract: As a non-contract optical measurement method in solid mechanics, the digital speckle correlation method (DSCM) has already been recognized as an excellent method for determining the surface deformation field in materials because of its outstanding features. In-plane displacement fields at the surface of objects under load are abstracted by using this method in this paper. And the corresponding maps of displacement fields are drawn to show deformation. The basic principle and mathematical model of gradient-based subpixel registration are briefly introduced for measuring subpixel displacement. COM component of this method is generated by using matlab7.1 through images of laser speckles. The COM component is called by Visual C++6.0 and the stand-alone application is generated. It is becoming easier to deal with image in Visual C++ by using this method. Then more time and energy will be spent on the algorithm. The development cycle of the algorithm is speeded up and efficiency of the application is improved.
Authors: Sen Men, Lei Yan, Hua Qian, Na Li, Jian Ping Yao
Abstract: This work presents a new detection system for seed viability assessment. The theoretical of the system is based on laser speckle or dynamic speckle, an optical phenomenon produced by interference of light. In the present work, the detection of a single in a period of time is been concentrate. The various parts and working principle of the laser speckle detection system explain detailed and the feasibility of this system is experiment in this paper. The result shows that this system is available in this field, and it can support the further study.
Authors: Qin Yan, Jian Lu, Xiao Wu Ni
Abstract: Experimental equipments are designed for the zero-crossing method of dynamic laser speckles to investigate the moving nature of nanoparticles in flowing nanofluids. After the experiments the velocity of nanoparticles in flowing nanofluids is determined according to its relationship with the zero-crossing rate of speckle intensity fluctuation. The results show that the zero-crossing rate is very sensitive to the velocity of nanoparticles when the velocity of nanofluids ranges from 17.6 mm/s to 60.2 mm/s. A TEM10 mode–like laser beam is designed and taken as an incident light to detect the moving direction of nanoparticles in flowing nanofluids. The moving direction of nanoparticles is parallel to the horizontal axis of the TEM10 mode-like laser beam when the zero-crossing rate reaches maximum. Experimental results show that the moving direction of nanoparticles can also be detected by using the zero-crossing method.
Authors: Xu Zhong, Xue Zhi Wang, Peter Farrell, Nicola Cooley, Bill Moran
Abstract: t is known that dynamic speckle patterns can be used to identify the temporal evolution of an active sample and some desired properties of the sample may therefore be detected via the dynamic laser speckle analysis. Mathematically understand the structure of sample surface which gives arise to the dynamic speckle patterns is crucial to the analysis. In this paper, a simulation model of the dynamic speckle patterns for plant leaves is proposed. The developed model is derived from the principle of coherent electromagnetic wave scattering off a randomly textured and time varying surface and is demonstrated via the simulation of dynamic speckle patterns of a fresh unattached leaf surface along the true laser speckle measurements. Both simulated and true measurements of the dynamic speckle patterns of the leaf are analyzed via several statistical techniques and a consistent agreement between the results of the two is observed. The proposed statistical model is helpful to gain the insight of the relationship between speckle dynamics and the activity of the leaf surface which is supposed to be an measurement of plant water stress and water status.
Authors: Eduard Schenuit, Rainer Bolkart, Thomas Becker, Oliver Spinka
Abstract: Progresses in developments of high resolution digital cameras and processors power as well enable the use of optical systems for axial and biaxial strain measurements. The main benefit of these systems is a contact free measurement on the sample surface without any influence to the sample. The commonly used optical systems based on following markings attached to sample surface which have to be applied before testing. This paper presents an alternative optical measuring system using the speckle-correlation-technique. The laser based method does not need any special sample markings before testing. The speckle correlation in the presented extensometer measures up to two-dimensional surface strains in tensile as well as in compression tests; original gauge lengths down to 1.5 mm are supported.
Authors: Hong Wang, Jan Guo Cui, Yang Yang Liu, Guo Ming Chen, Sheng Ping Liu
Abstract: The microcirculation plays a crucial role in the interaction between blood and tissues in physiological pathophysiological pharmacological and clinical states. Despite its significant role in numerous diseases including, hypertension diabetes, sepsis or multiple organ failure, visible and near-infrared light, offer a window into human and animal tissues due to reduced scattering and absorption. We review orthogonal polarization spectral (OPS) imaging method for direct visualization and quantitative assessment of human microcirculation at the bedside are limited. OPS imaging is a relatively new noninvasive method for assessment of human microcirculation without using fluorescent dyes. Recent clinical studies using OPS imaging in various pathological states have shown a wide spectrum of different clinical applications with evident impact on the diagnosis, treatment or prognosis assessment. Thus, there is a great effort to validate OPS imaging for various clinical purposes. The principles of OPS imaging, validation studies, its advantages, limitations, methods of quantitative assessment and current experience in clinical practice are also discussed.
Authors: Wen Tao Zhang, Chuan Yang, Bao Wu Zhang, Xian Ming Xiong
Abstract: Relationship between texture characteristics of laser speckle pattern and surface roughness of turning machinery metal surface was studied in this paper. Based on Wiener filter image processing technology, curve relationship between four texture feature parameters such as energy, entropy, contrast as well as correlation and roughness Ra before and after filtering was also established. Integrated texture feature method was used to analyze the change of each characteristic parameter and roughness Ra and obtain a relatively good curve. The results show that when roughness Ra is in the range of 0.8-6.3μm, energy, entropy and correlation are most suitable to represent surface roughness of turning machinery metal sample.
Authors: Yu Tian Wang, Dong Sheng Wang, Wei Wei Pan
Abstract: When introduce the wavelet theory to filter the hologram and the reconstructed image in the digital holography, the noise of the reconstructed image is greatly reduced. In the off-axis digital holography, the zero-order wave is decreased dramatically when after a wavelet filter, at the same time, the speckle noise is also reduced, and it turns out that the resolution of the reconstruction image is improved greatly. The system launches the research thoroughly on the three-dimensional body digital holographic technology, from the theory to the application, from the simulation to the experiment, and has elaborated and analyzed each characteristic of three-dimensional body digital holographic technology. It proposes many kinds of improved effective method of three-dimensional body digital holographic restructuring information, and finally has effectively explored the three-dimensional body digital holographic technology application through the experiment.
Authors: Ji Jun Fan, Nan Hui Yu
Abstract: In this paper, the principle of measuring infinitesimal displacement by laser speckle is proposed to measure the velocities of particles in ER fluids. It is verified that speckles can be formed by illuminating laser beam on the starch ER fluids. The speckle patterns was recorded with high speed CCD camera, and the speckle patterns sequences with short time intervals was obtained by intercepting laser speckle video. Displacements parallel to the direction of electric field and that perpendicular to the direction of electric field were obtained by processing the two consecutive speckle patterns. The experimental results showed that the velocities of particles decreased oscillatorily with time. There is a critical electric field and a critical sample concentration, when lower than this critical electric field (concentration), the mean particle velocity increased; otherwise, it decreased.
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