4,215 results on '"Speckle imaging"'
Search Results
2. Industrial Application of Surface Crack Detection in Sheet Metal Stamping Using Shift-and-Add Speckle Imaging
- Author
-
Sławomir Świłło and Robert Cacko
- Subjects
machine vision ,shift-and-add method ,crack detection ,speckle imaging ,sheet metal forming ,Engineering (General). Civil engineering (General) ,TA1-2040 - Abstract
The sheet metal surface crack detection during manufacturing is an essential issue because of both the product quality and process productivity. Development of solutions to eliminate defective products during the metal forming process is crucial for the smooth production and for developing an appropriate tool geometry in the initial phase of the process. Currently, the methods of surface crack detection used in the industry are mostly related to visual inspection. These are methods that require operators of industrial facilities considerable attention and effort to capture emerging discontinuities on the sheet metal surface. Also, this situation results increase in the duration of the specific operations of stamping and significantly reduces productivity. Therefore, an industrial application of a non-contact laser technique that simultaneously provides the results of the speckle imaging is presented. The authors demonstrate a specially designed machine vision system along with experimental tools for the stamping operation. Proposed solution uses the phenomenon of speckle pattern that appears in the image of the investigated sheet surface produced by the laser beam emission. In this method, coherent laser light is emitted to the surface, where a speckle pattern is generated due to scatter reflection from the sheet metal surface and then, shift-and-add technique and image processing is applied. The proposed measurement technique consists, initially, of making a sequence of images of the tested object for the moving surface of the sheet. Secondly, the object's displacement quantity in each image is determined, and the position is corrected. The test object in each image is moved to the starting position, and all images are superimposed. It allows to obtain a high-quality image with visible surface defects. Finally, the dynamically changing speckle pattern intensity is evaluated using Gaussian-of-Laplacian edge detection to investigate a surface crack location due to the surface discontinues and light scattering. This process is recommended for machine vision imaging of distant objects, which works well in industrial conditions as well as online analysis. Also, from the speckle size measurement, an experimental procedure is employed to verify the best condition for vision system resolution.
- Published
- 2023
- Full Text
- View/download PDF
3. Employing optoelectronic laser speckle imaging to reveal molecular dynamics followed by the thermal expansion of liquid water.
- Author
-
Ansari, Mohammad Zaheer
- Subjects
- *
EXPANSION of liquids , *MOLECULAR dynamics , *THERMAL expansion measurement , *THERMAL expansion , *COHERENCE (Optics) , *SPECKLE interferometry , *SPECKLE interference - Abstract
We presented a low-cost electronic speckle imaging method for quantifying and monitoring the moderate expansion and contraction of fluids. The system comprises the steps of recording a stack of electronic speckle patterns of the liquid under coherent light illumination, generating velocity vector fields of the temporal dynamic speckle sequence, calculating profile velocity at different temperatures of the liquid, evaluating the inertia moment (IM) of the temporal history of speckle patterns followed by the computation of the co-occurrence matrices. The results show that profile velocity at different temperatures may be used to determine the liquid's thermal state. The test evaluated speckle grain size as a potential criterion for monitoring the liquid's moderate thermal expansion and allowed for the measurement of thermal exchange between the system and its surroundings even at very low temperatures (4 °C). The experiment demonstrates the effectiveness of the laser speckle imaging technique at the macro- and micro-scale molecular dynamics levels. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
4. Hybrid Imaging Detectors in X-Ray Phase-Contrast Applications
- Author
-
Brombal, Luca, Rigon, Luigi, and Iniewski, Krzysztof (Kris), editor
- Published
- 2023
- Full Text
- View/download PDF
5. Industrial Application of Surface Crack Detection in Sheet Metal Stamping Using Shift-and-Add Speckle Imaging.
- Author
-
Świłło, Sławomir and Cacko, Robert
- Subjects
SPECKLE interferometry ,SURFACE cracks ,SHEET metal ,METAL stamping ,SPECKLE interference - Abstract
The sheet metal surface crack detection during manufacturing is an essential issue because of both the product quality and process productivity. Development of solutions to eliminate defective products during the metal forming process is crucial for the smooth production and for developing an appropriate tool geometry in the initial phase of the process. Currently, the methods of surface crack detection used in the industry are mostly related to visual inspection. These are methods that require operators of industrial facilities considerable attention and effort to capture emerging discontinuities on the sheet metal surface. Also, this situation results increase in the duration of the specific operations of stamping and significantly reduces productivity. Therefore, an industrial application of a non-contact laser technique that simultaneously provides the results of the speckle imaging is presented. The authors demonstrate a specially designed machine vision system along with experimental tools for the stamping operation. Proposed solution uses the phenomenon of speckle pattern that appears in the image of the investigated sheet surface produced by the laser beam emission. In this method, coherent laser light is emitted to the surface, where a speckle pattern is generated due to scatter reflection from the sheet metal surface and then, shift-and-add technique and image processing is applied. The proposed measurement technique consists, initially, of making a sequence of images of the tested object for the moving surface of the sheet. Secondly, the object's displacement quantity in each image is determined, and the position is corrected. The test object in each image is moved to the starting position, and all images are superimposed. It allows to obtain a high-quality image with visible surface defects. Finally, the dynamically changing speckle pattern intensity is evaluated using Gaussian-of-Laplacian edge detection to investigate a surface crack location due to the surface discontinues and light scattering. This process is recommended for machine vision imaging of distant objects, which works well in industrial conditions as well as online analysis. Also, from the speckle size measurement, an experimental procedure is employed to verify the best condition for vision system resolution. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
6. 基于光散射斑图成像特征的微细颗粒原位粒径 检测方法.
- Author
-
孙毅, 李长杨, 毛亚郎, and 叶伟伟
- Subjects
PARTICULATE matter ,IMAGE analysis ,MANUFACTURING processes ,BALL mills ,SPECKLE interferometry ,LIGHT scattering - Abstract
Copyright of China Mechanical Engineering is the property of Editorial Board of China Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2023
- Full Text
- View/download PDF
7. A Single-Shot Scattering Medium Imaging Method via Bispectrum Truncation
- Author
-
Yuting Han, Honghai Shen, Fang Yuan, Tianxiang Ma, Pengzhang Dai, Yang Sun, and Hairong Chu
- Subjects
speckle imaging ,speckle autocorrelation ,phase recovery algorithm ,bispectrum truncation ,Chemical technology ,TP1-1185 - Abstract
Imaging using scattering media is a very important yet challenging technology. As one of the most widely used scattering imaging methods, speckle autocorrelation technology has important applications in several fields. However, traditional speckle autocorrelation imaging methods usually use iterative phase recovery algorithms to obtain the Fourier phase of hidden objects, posing issues such as large data calculation volumes and uncertain reconstruction results. Here, we propose a single-shot scattering imaging method based on the bispectrum truncation method. The bispectrum analysis is utilized for hidden object phase recovery, the truncation method is used to avoid the computation of redundant data when calculating the bispectrum data, and the method is experimentally verified. The experimental results show that our method does not require uncertain iterative calculations and can reduce the bispectrum data computation by more than 80% by adjusting the truncation factor without damaging the imaging quality, which greatly improves imaging efficiency. This method paves the way for rapid imaging through scattering media and brings benefits for imaging in dynamic situations.
- Published
- 2024
- Full Text
- View/download PDF
8. Visualization of skin layer formation process on the aqueous colloidal solutions surface in the inkjet nozzle by using dynamic light scattering method
- Author
-
Yoshihiro HARADA, Norika OKOCHI, and Kazuyoshi FUSHINOBU
- Subjects
visualization ,light scattering ,evaporation ,speckle imaging ,optical coherence tomography ,Engineering machinery, tools, and implements ,TA213-215 ,Mechanical engineering and machinery ,TJ1-1570 - Abstract
The objective of this paper is to develop a method for visualizing the onset of skin layer formation at the gas-liquid interface during the evaporation of a water-based pigment ink filled in a narrow space such as the nozzle of an inkjet printhead. We developed two methods to visualize the surface and depth-wise distributions of the diffusion coefficient near the edge of a glass capillary filled with aqueous colloidal solution by using measurements based on the dynamic light scattering method. One method generates laser speckles at the gas-liquid interface of the ink, which are analyzed to determine the temporal changes in the surface distribution of particle diffusion coefficients. Another method uses an optical coherence tomography method to acquire cross-sectional images of the ink in the depth-wise direction, and analyzes the speckles that appear on the images to determine the temporal change in the depth distribution of the particle diffusion coefficient. It was observed that, depending on the type of hardly volatile solvent in ink, there are cases where the diffusion coefficient changes while remaining spatially uniform, and other cases where the diffusion coefficient differs remarkably near the gas-liquid interface. Since the motion of particles in the ink can be visualized in three dimensions, although pseudo-lightly, it has been possible to detect signs of skin layer formation.
- Published
- 2023
- Full Text
- View/download PDF
9. Label-free optical interferometric microscopy to characterize morphodynamics in living plants.
- Author
-
Ebrahimi, Samira, Moreno-Pescador, Guillermo, Persson, Staffan, Jauffred, Liselotte, and Bendix, Poul Martin
- Subjects
MICROSCOPY ,OPTICAL coherence tomography ,PLANT cells & tissues ,SEED viability ,FLUORESCENCE microscopy ,CELL morphology - Abstract
During the last century, fluorescence microscopy has played a pivotal role in a range of scientific discoveries. The success of fluorescence microscopy has prevailed despite several shortcomings like measurement time, photobleaching, temporal resolution, and specific sample preparation. To bypass these obstacles, label-free interferometric methods have been developed. Interferometry exploits the full wavefront information of laser light after interaction with biological material to yield interference patterns that contain information about structure and activity. Here, we review recent studies in interferometric imaging of plant cells and tissues, using techniques such as biospeckle imaging, optical coherence tomography, and digital holography. These methods enable quantification of cell morphology and dynamic intracellular measurements over extended periods of time. Recent investigations have showcased the potential of interferometric techniques for precise identification of seed viability and germination, plant diseases, plant growth and cell texture, intracellular activity and cytoplasmic transport. We envision that further developments of these labelfree approaches, will allow for high-resolution, dynamic imaging of plants and their organelles, ranging in scales from sub-cellular to tissue and from milliseconds to hours. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
10. 透过薄散射介质的目标事件分类方法.
- Author
-
杨泊钰 and 柯钧
- Subjects
SPECKLE interferometry ,SPECKLE interference ,CAMERAS ,LIGHTING ,CLASSIFICATION - Abstract
Copyright of Chinese Journal of Liquid Crystal & Displays is the property of Chinese Journal of Liquid Crystal & Displays and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2023
- Full Text
- View/download PDF
11. Investigation of a new modulated aperture using speckle techniques
- Author
-
A. M. Hamed
- Subjects
Modulated apertures ,Point spread function ,Speckle imaging ,Medicine (General) ,R5-920 ,Science - Abstract
Abstract Background A design of equally spaced eight-circles placed at equal distances from the origin is suggested. Three models corresponding to the eight-circle design considering conic, linear, and quadratic distributions are investigated. This arrangement is considered for the sake of improving both microscope resolution and image contrast as compared with the pure annular aperture. This design is different compared with other recent work on aperture modulation. Results and discussions The point spread function (PSF) is computed in all the models using the fast Fourier transform (FFT) algorithm that computes the discrete Fourier transform (DFT) corresponding to the models and compared with the corresponding PSF in the case of uniform circular aperture. In addition, the autocorrelation images for the apertures are shown differently. It is shown smooth pattern for the circular arrangement as compared with the deformation and shrinking appeared in the central peak in case of conic model. Finally, the speckle images corresponding to the considered apertures are investigated. Reconstructed apertures are obtained from the speckle images using the FFT algorithm. Conclusions The PSF is computed for the described models, and the autocorrelation corresponding to the apertures showed difference. The reconstructed apertures from the speckle images can be improved using filtering techniques. It is noted that MATLAB codes are constructed in the computations of all images and plots.
- Published
- 2022
- Full Text
- View/download PDF
12. Perspective Compensation of 2D-DIC Measurements by Combination with Speckle Imaging
- Author
-
Heikkinen, Juuso, Schajer, Gary S., Zimmerman, Kristin B., Series Editor, Lin, Ming-Tzer, editor, Furlong, Cosme, editor, and Hwang, Chi-Hung, editor
- Published
- 2021
- Full Text
- View/download PDF
13. Dynamic piecewise speckle temporal contrast imaging of microcirculation.
- Author
-
Qin, Jia and An, Lin
- Abstract
A dynamic functional piecewise laser speckle temporal contrast imaging (PW-LSTCI) modality is proposed to show the dynamic blood flow in the macro and micro circulations. Research shows that there is always a transition point related to contact time, which separates the positive growth trend of high velocity from the negative growth trend of small velocity. It can be found that the series of transition points with the corresponding exposure time follow an exponential pattern, indicating that the increase in the exposure time is accompanied by the decrease in the value of transition point. The changes of earflap blood flow in root artery circulation induced by occlusion and reperfusion in mice are imaged to observe the existence of transition points and their effects on slow and fast dynamic blood flow imaging. The study is valuable for noninvasive imaging of microcirculation and plays an important role in dynamic functional imaging of vascular system. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
14. Compressive Imaging Through Optical Fiber with Partial Speckle Scanning.
- Author
-
Guérit, Stéphanie, Sivankutty, Siddharth, Lee, John, Rigneault, Hervé, and Jacques, Laurent
- Subjects
OPTICAL images ,OPTICAL fibers ,SPECKLE interference ,SPATIAL light modulators ,WAVEFRONTS (Optics) ,RANDOM fields ,ELECTRONIC speckle pattern interferometry ,HIGH-intensity focused ultrasound - Abstract
Fluorescence imaging through ultrathin fibers is a promising approach to obtain high-resolution imaging with molecular specificity at depths much larger than the scattering mean-free paths of biological tissues. Such imaging techniques, generally termed lensless endoscopy, rely upon the wavefront control at the distal end of a fiber to coherently combine multiple spatial modes of a multicore (MCF) or multimode fiber (MMF). Typically, a spatial light modulator (SLM) is employed to combine hundreds of modes by phase-matching to generate a high-intensity focal spot. This spot is subsequently scanned across the sample to obtain an image. We propose here a novel scanning scheme, partial speckle scanning (PSS), inspired by compressive sensing theory, that avoids the use of an SLM to perform fluorescent imaging with optical fibers with reduced acquisition time. Such a strategy avoids photo-bleaching while keeping high reconstruction quality. We develop our approach on two key properties of the MCF: (i) the ability to easily generate speckles, and (ii) the memory effect that allows one to use fast scan mirrors to shift light patterns. First, we show that speckles are subexponential random fields. Despite their granular structure, an appropriate choice of the reconstruction parameters makes them good candidates to build efficient sensing matrices. Then, we numerically validate our approach and apply it on experimental data. The proposed sensing technique outperforms conventional raster scanning: higher reconstruction quality is achieved with far fewer observations. For a fixed reconstruction quality, our speckle scanning approach is faster than compressive sensing schemes which require changing the speckle pattern for each observation. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
15. Speckle Interferometric Observations With the Gemini 8-m Telescopes: Signal-to-Noise Calculations and Observational Results
- Author
-
Steve B. Howell and Elise Furlan
- Subjects
instrumentation–telescopes ,speckle imaging ,Gemini telescope ,techniques ,high resolution imaging ,Astronomy ,QB1-991 ,Geophysics. Cosmic physics ,QC801-809 - Abstract
Using 3 years of observations with the Zorro and ’Alopeke speckle interferometric instruments at Gemini South and North, respectively, we present an analysis of the sensitivity of the data taken in two narrow-band optical filters centered at 562 and 832 nm (widths of 54 and 40 nm, respectively). In this paper we focus on model calculations of the predicted signal-to-noise values achievable and the results of over 2500 actual observations. We find that S/N values of several 100 are easily achieved, but that the sky background during full moon is a very limiting factor in the observations, especially those performed in the short-wavelength (blue) optical spectral range and for targets fainter than R ∼14. A comparison of our Gemini speckle observations over six observing semesters reveals that red band-pass observations provide more robust results in general, likely due to better atmospheric performance at these wavelengths. Using the identical instruments on Gemini North and South, we find that similar results are obtained, yielding typical contrast limits of 5-9 magnitudes from the diffraction limit out to 1.2″ for a range of target brightness (optical magnitudes from ∼ 3 to >16). Using our S/N model along with the observational results, an estimation of the contrast limits achievable for a given observation can be predicted based on the target brightness, sky illumination and seeing conditions, and the total integration time.
- Published
- 2022
- Full Text
- View/download PDF
16. Spatio-temporal feature analysis of laser speckle images for simultaneous quantification of skin thickness and perfusion demonstrated using in-vitro scleroderma phantoms.
- Author
-
Krishnamurthy, Priya, Unni, Sujatha Narayanan, and Jayasankar, Subitcha
- Subjects
- *
PERFUSION , *SPECKLE interference , *SPECKLE interferometry , *AUTOIMMUNE diseases , *IMAGE analysis , *BIOLOGICAL models , *IMAGING phantoms , *SYNTHETIC aperture radar - Abstract
• Simultaneous quantification of skin thickness and microcirculatory flow rate is reported for the first-time using laser speckle image analysis. • The experiments were carried out on a flow phantom with physiologically relevant measures for skin thickness, scatterer concentration and flow rate, specific to healthy and scleroderma tissue. • A multiparametric model is devised for classifying tissue status after a comprehensive analysis of the extracted speckle parameters. • This approach can be extended to other physical / biological models as well where the extracted speckle parameters are interlinked with structural and functional sample properties. Scleroderma is an autoimmune disorder caused by increased collagen deposition in the dermal layer of skin, which alters the dermal layer's thickness, affecting the local perfusion. In this article, we aim to build an experimental model to simultaneously quantify the dermal thickness and perfusion changes during scleroderma progression through a comprehensive analysis of various static and dynamic laser speckle image parameters. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
17. Enhancement in sensitivity of a blood perfusion parameter for frame-rate analysis of bio-speckle image.
- Author
-
Yokoi, Naomichi and Aizu, Yoshihisa
- Subjects
- *
IMAGE analysis , *SPECKLE interference , *IMAGE processing , *PERFUSION , *SPECKLE interferometry , *BLOOD vessels - Abstract
We have previously presented a blood perfusion parameter by means of the spatial contrast of speckle patterns observed for blood perfusion in skin tissue and a blood vessel. This parameter permits us to visualize a relative blood perfusion distribution from a single speckle pattern. Therefore, it can estimate the blood perfusion with a frame rate of an imaging device employed. This parameter is, however, dependent on the speckle size and the condition of image processing of speckle patterns. In the present study, we estimated this condition with relation to the speckle size for obtaining high sensitivity and good linearity of the parameter to the blood perfusion. Experiments were conducted for ground-glass model, flow model and human wrist to investigate perfusion sensing characteristics of the present parameter. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
18. Self-calibrated defocused speckle imaging for remote surface motion measurements.
- Author
-
Heikkinen, Juuso and Schajer, Gary S
- Subjects
- *
SPECKLE interferometry , *SPECKLE interference , *TRAFFIC signs & signals , *ROTATIONAL motion , *LASER beams , *ARTIFICIAL satellite tracking - Abstract
• The laser speckle pattern scattered from a diffuse surface is used to track object surface motions and to extract object distance and orientation for system calibration. • The proposed system can track speckle motions resulting from microscopic in-plane displacements and out-of-plane rotations at a high accuracy (6.0 %) and repeatability (2.8 %) from a 30.7-m distance. • The system has high demonstrated tilt sensitivity down to 0.0006° and can simultaneously measure absolute macroscopic surface angles beyond 10°. • The proposed approach is suitable for measuring retroreflective surfaces, like traffic signs and number plates. Defocused Speckle Imaging (DSI) is a non-contact optical method that can measure multiaxial object motions at microscopic sensitivity using a simple and mechanically robust optical setup. The object surface is illuminated by a laser beam, and the scattered interference speckle pattern is tracked with a defocused camera. DSI measurement sensitivity increases with distance, and the sensitivity can be tuned by simple camera defocus adjustment. These characteristics make DSI an attractive choice for tracking remote objects in field conditions. However, the use of DSI for practical measurements is limited because the speckle signals due to linear and rotational surface motions mix together, and because the instrument calibration requires accurate object range and surface orientation parameters. To address these issues, the work described here combines two recently presented concepts: 1) a defocused camera pair, and 2) a diffraction-based self-calibration principle. The proposed approach was demonstrated by a series of self-calibrated multiaxial motion measurements performed at an extended (30.7-m) distance. The studied motions included in-plane displacements and out-of-plane rotations (tilts), whereas out-of-plane displacements and in-plane rotations were excluded. The experiments showed DSI's capability for high tilt sensitivity down to 0.0006°, standalone remote angle measurements, and suitability for retroreflective surfaces. The diffraction-based self-calibration approach could monitor sampling distances at a 6.4 % accuracy and the relative surface angles of 2.5–7.4° at a 0.2° accuracy. The defocused camera pair tracked microscopic in-plane displacements (400 µm) and very fine out-of-plane tilts (0.003°) at a high accuracy, with a maximum uncertainty of 6.0 %. The proposed DSI approach is particularly suited for monitoring large objects and for operating in hazardous environments. The findings pave a way for interesting new applications, like high-range remote angle measurements, high-sensitivity straightness measurements, and 3D-positioning utilizing retroreflective markers that already exist in the built infrastructure. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
19. Moving Target Tracking and Imaging Through Scattering Media via Speckle-Difference-Combined Bispectrum Analysis
- Author
-
Yingbo Wang, Jie Cao, Chengqiang Xu, Yang Cheng, Xuemin Cheng, and Qun Hao
- Subjects
Imaging through turbid media ,speckle imaging ,computation imaging ,turbid media. ,Applied optics. Photonics ,TA1501-1820 ,Optics. Light ,QC350-467 - Abstract
Target tracking and imaging through scattering media are challenges that must be overcome for important applications in various fields. The fundamental problem is the randomly diffused light in scattering media that prevents the formation of diffraction-limited images. In recent years, speckle correlation has emerged as a powerful approach for restoring targets through scattering media and tracking targets with high scattering. However, this method fails to achieve high-accuracy target tracking in multidimensional motion. Furthermore, retrieving the deterministic phase of a target in a low-resolution speckle pattern is limited. Here, a method based on speckle-difference-combined bispectrum analysis (SDCBA) is presented to simultaneously track and image targets. The proposed SDCBA requires no high-resolution pattern, randomly assigned initial values, nor numerous iterations. The target is tracked simultaneously in multidimension by using speckle difference autocorrelation and restored with the deterministic phase via bispectrum analysis of the low-resolution speckle pattern. This work carries out simulations and experiments to demonstrate simultaneous multidimensional target tracking and imaging in low-resolution speckle pattern through scattering media via the SDCBA. This work will benefit various fields, including biomedical applications, materials science, and military security.
- Published
- 2019
- Full Text
- View/download PDF
20. Label-free optical interferometric microscopy to characterize morphodynamics in living plants
- Abstract
During the last century, fluorescence microscopy has played a pivotal role in a range of scientific discoveries. The success of fluorescence microscopy has prevailed despite several shortcomings like measurement time, photobleaching, temporal resolution, and specific sample preparation. To bypass these obstacles, label-free interferometric methods have been developed. Interferometry exploits the full wavefront information of laser light after interaction with biological material to yield interference patterns that contain information about structure and activity. Here, we review recent studies in interferometric imaging of plant cells and tissues, using techniques such as biospeckle imaging, optical coherence tomography, and digital holography. These methods enable quantification of cell morphology and dynamic intracellular measurements over extended periods of time. Recent investigations have showcased the potential of interferometric techniques for precise identification of seed viability and germination, plant diseases, plant growth and cell texture, intracellular activity and cytoplasmic transport. We envision that further developments of these label-free approaches, will allow for high-resolution, dynamic imaging of plants and their organelles, ranging in scales from sub-cellular to tissue and from milliseconds to hours.
- Published
- 2023
21. Label-free optical interferometric microscopy to characterize morphodynamics in living plants
- Abstract
During the last century, fluorescence microscopy has played a pivotal role in a range of scientific discoveries. The success of fluorescence microscopy has prevailed despite several shortcomings like measurement time, photobleaching, temporal resolution, and specific sample preparation. To bypass these obstacles, label-free interferometric methods have been developed. Interferometry exploits the full wavefront information of laser light after interaction with biological material to yield interference patterns that contain information about structure and activity. Here, we review recent studies in interferometric imaging of plant cells and tissues, using techniques such as biospeckle imaging, optical coherence tomography, and digital holography. These methods enable quantification of cell morphology and dynamic intracellular measurements over extended periods of time. Recent investigations have showcased the potential of interferometric techniques for precise identification of seed viability and germination, plant diseases, plant growth and cell texture, intracellular activity and cytoplasmic transport. We envision that further developments of these label-free approaches, will allow for high-resolution, dynamic imaging of plants and their organelles, ranging in scales from sub-cellular to tissue and from milliseconds to hours.
- Published
- 2023
22. A Single-Shot Scattering Medium Imaging Method via Bispectrum Truncation.
- Author
-
Han Y, Shen H, Yuan F, Ma T, Dai P, Sun Y, and Chu H
- Abstract
Imaging using scattering media is a very important yet challenging technology. As one of the most widely used scattering imaging methods, speckle autocorrelation technology has important applications in several fields. However, traditional speckle autocorrelation imaging methods usually use iterative phase recovery algorithms to obtain the Fourier phase of hidden objects, posing issues such as large data calculation volumes and uncertain reconstruction results. Here, we propose a single-shot scattering imaging method based on the bispectrum truncation method. The bispectrum analysis is utilized for hidden object phase recovery, the truncation method is used to avoid the computation of redundant data when calculating the bispectrum data, and the method is experimentally verified. The experimental results show that our method does not require uncertain iterative calculations and can reduce the bispectrum data computation by more than 80% by adjusting the truncation factor without damaging the imaging quality, which greatly improves imaging efficiency. This method paves the way for rapid imaging through scattering media and brings benefits for imaging in dynamic situations.
- Published
- 2024
- Full Text
- View/download PDF
23. Three-dimensional speckle suppression in optical coherence tomography based on the curvelet transform
- Author
-
Yu, L, Jian, Z, Rao, B, Tromberg, BJ, and Chen, Z
- Subjects
Optical Coherence Tomography ,Speckle Imaging ,Image Enhancement - Abstract
Optical coherence tomography is an emerging non-invasive technology that provides high resolution, cross-sectional tomographic images of internal structures of specimens. It holds great potentials for a wide variety of applications, especially in the field of biomedical imaging. OCT images, however, are usually degraded by significant speckle noise. Here we report a 3D approach to attenuating speckle noise in OCT images. This approach is based on the 3D curvelet transform, and is conveniently controlled by a single parameter that determines the threshold in the curvelet domain. Unlike 2D approaches which only consider information in individual images, 3D processing, by analyzing all images in a volume simultaneously, has the advantage of also taking the information between images into account. This, coupled with the curvelet transform's nearly optimal sparse representation of curved edges that are common in OCT images, provides a simple yet powerful platform for speckle attenuation. We show the approach suppresses a significant amount of speckle noise, and in the mean time preserves and thus reveals many subtle features that could get attenuated in other approaches. © 2010 Copyright SPIE - The International Society for Optical Engineering.
- Published
- 2010
24. Three-dimensional speckle suppression in optical coherence tomography based on the curvelet transform
- Author
-
Yu, Lingfeng, Jian, Zhongping, Rao, Bin, Tromberg, Bruce J, and Chen, Zhongping
- Subjects
Optical Coherence Tomography ,Speckle Imaging ,Image Enhancement - Abstract
Optical coherence tomography is an emerging non-invasive technology that provides high resolution, cross-sectional tomographic images of internal structures of specimens. It holds great potentials for a wide variety of applications, especially in the field of biomedical imaging. OCT images, however, are usually degraded by significant speckle noise. Here we report a 3D approach to attenuating speckle noise in OCT images. This approach is based on the 3D curvelet transform, and is conveniently controlled by a single parameter that determines the threshold in the curvelet domain. Unlike 2D approaches which only consider information in individual images, 3D processing, by analyzing all images in a volume simultaneously, has the advantage of also taking the information between images into account. This, coupled with the curvelet transform's nearly optimal sparse representation of curved edges that are common in OCT images, provides a simple yet powerful platform for speckle attenuation. We show the approach suppresses a significant amount of speckle noise, and in the mean time preserves and thus reveals many subtle features that could get attenuated in other approaches. © 2010 Copyright SPIE - The International Society for Optical Engineering.
- Published
- 2010
25. Moving Target Tracking and Imaging Through Scattering Media via Speckle-Difference-Combined Bispectrum Analysis.
- Author
-
Wang, Yingbo, Cao, Jie, Xu, Chengqiang, Cheng, Yang, Cheng, Xuemin, and Hao, Qun
- Abstract
Target tracking and imaging through scattering media are challenges that must be overcome for important applications in various fields. The fundamental problem is the randomly diffused light in scattering media that prevents the formation of diffraction-limited images. In recent years, speckle correlation has emerged as a powerful approach for restoring targets through scattering media and tracking targets with high scattering. However, this method fails to achieve high-accuracy target tracking in multidimensional motion. Furthermore, retrieving the deterministic phase of a target in a low-resolution speckle pattern is limited. Here, a method based on speckle-difference-combined bispectrum analysis (SDCBA) is presented to simultaneously track and image targets. The proposed SDCBA requires no high-resolution pattern, randomly assigned initial values, nor numerous iterations. The target is tracked simultaneously in multidimension by using speckle difference autocorrelation and restored with the deterministic phase via bispectrum analysis of the low-resolution speckle pattern. This work carries out simulations and experiments to demonstrate simultaneous multidimensional target tracking and imaging in low-resolution speckle pattern through scattering media via the SDCBA. This work will benefit various fields, including biomedical applications, materials science, and military security. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
26. Investigation of a new modulated aperture using speckle techniques
- Author
-
Hamed, A. M.
- Published
- 2022
- Full Text
- View/download PDF
27. Evaluation of vascular effects of photodynamic and photothermal therapies using benzoporphyrin derivative monoacid ring a on a rodent dorsal skinfold model
- Author
-
Smith, TK, Choi, B, Ramirez-San-Juan, J, Nelson, JS, and Kelly, KM
- Subjects
dermatology ,flow dynamics ,photosensitizer ,speckle imaging ,vascular perftision - Abstract
Background and Objectives: Pulsed dye laser (PDL) irradiation is the standard clinical treatment for vascular lesions. However, PDL treatment of port wine stain birthmarks (PWS) is variable and unpredictable. Photodynamic therapy (PDT) using benzoporphyrin derivative monoacid ring A (BPD) and yellow light may induce substantial vascular effects and potentially offer a more effective treatment. In this study, we utilize a rodent dorsal skinfold model to evaluate the vascular effects of BPD-PDT at 576 nm as compared to PDL. Study Design/Materials and Methods: A dorsal skinfold window was created on the backs of female Sprague-Dawley rats, allowing epidermal and subdermal irradiation and subdermal imaging. One mg/kg BPD was administered intravenously via a jugular venous catheter. Study groups were: control (no BPD, no light), PDL (585 nm, τ p 1.5 ms, 10 J/cm 2), and PDT (BPD + continuous wave irradiation (CW) at 576nm, τ p 16 min, 96 J/cm 2). Vessels were imaged and assessed for damage using laser speckle imaging (LSI) before, immediately after, and 18 hours post-intervention. Results: Epidermal irradiation was accomplished without blistering, scabbing or ulceration. PDL and PDT resulted in similar reductions in vascular perfusion 18 hours post-intervention (34.6% and 33.4%, respectively). Conclusions: BPD-PDT can achieve safe and selective vascular effects and may offer an alternative therapeutic option for treatment of hypervascular skin lesions including PWS birthmarks.
- Published
- 2005
28. Evaluation of vascular effects after photodynamic and photothermal therapies using benzoporphyrin derivative monoacid ring A on a rodent dorsal skinfold model
- Author
-
Smith, Tia K, Choi, Bernard, Ramirez-San-Juan, Julio C, Nelson, John S, and Kelly, Kristen M
- Subjects
dermatology ,flow dynamics ,photosensitizer ,speckle imaging ,vascular perftision - Abstract
Background and Objectives: Pulsed dye laser (PDL) irradiation is the standard clinical treatment for vascular lesions. However, PDL treatment of port wine stain birthmarks (PWS) is variable and unpredictable. Photodynamic therapy (PDT) using benzoporphyrin derivative monoacid ring A (BPD) and yellow light may induce substantial vascular effects and potentially offer a more effective treatment. In this study, we utilize a rodent dorsal skinfold model to evaluate the vascular effects of BPD-PDT at 576 nm as compared to PDL. Study Design/Materials and Methods: A dorsal skinfold window was created on the backs of female Sprague-Dawley rats, allowing epidermal and subdermal irradiation and subdermal imaging. One mg/kg BPD was administered intravenously via a jugular venous catheter. Study groups were: control (no BPD, no light), PDL (585 nm, τ p 1.5 ms, 10 J/cm 2), and PDT (BPD + continuous wave irradiation (CW) at 576nm, τ p 16 min, 96 J/cm 2). Vessels were imaged and assessed for damage using laser speckle imaging (LSI) before, immediately after, and 18 hours post-intervention. Results: Epidermal irradiation was accomplished without blistering, scabbing or ulceration. PDL and PDT resulted in similar reductions in vascular perfusion 18 hours post-intervention (34.6% and 33.4%, respectively). Conclusions: BPD-PDT can achieve safe and selective vascular effects and may offer an alternative therapeutic option for treatment of hypervascular skin lesions including PWS birthmarks.
- Published
- 2005
29. Quantitative Phase Imaging Camera With a Weak Diffuser
- Author
-
Linpeng Lu, Jiasong Sun, Jialin Zhang, Yao Fan, Qian Chen, and Chao Zuo
- Subjects
transport of intensity equation ,quantitative phase imaging ,microscopic imaging ,speckle imaging ,phase space ,Physics ,QC1-999 - Abstract
We introduce the quantitative phase imaging camera with a weak diffuser (QPICWD) as an effective scheme of quantitative phase imaging (QPI) based on normal microscope platforms. The QPICWD is an independent compact camera measuring object induced phase delay under low-coherence quasi-monochromatic illumination by examining the deformation of the speckle intensity pattern. By interpreting the speckle deformation with an ensemble average of the geometric flow, we can obtain the high-resolution distortion field via the transport of intensity equation (TIE). Since the phase measured by TIE is the generalized phase of the partially coherent image, rather than the phase of the measured object, we analyze the effect of illumination coherence and imaging numerical aperture (NA) on the accuracy of phase retrieval, revealing that the sample's phase can be reliably reconstructed under the conditions that the coherence parameter (the ratio of illumination NA to objective NA) of the Köhler illumination is between 0.3 and 0.5. We present some applications for the proposed design involving nondestructive optical testing of microlens array with nanometric thickness and imaging of fixed and live unstained HeLa cells. Since the designed QPI camera does not require any modification of the widely available bright-field microscope or additional accessories for its use, it is expected to be applied by the broader communities of biology and medicine.
- Published
- 2019
- Full Text
- View/download PDF
30. Ghost imaging of the low or high frequency based on the corresponding spatial-frequency of the reference pattern.
- Author
-
Guo, Kai-xian, Bai, Yan-feng, and Fu, Xi-quan
- Subjects
- *
SIGNAL-to-noise ratio , *SPECKLE interferometry - Abstract
We discuss the possibility that the contours or details of images can be obtained by using the low-spatial-frequency or high-spatial-frequency parts of the reference beam in ghost imaging. The influence of the threshold selection which is used to divide the reference pattern into low-frequency and high-frequency parts is quite different. With the increase of the threshold, the signal-to-noise ratio (SNR) of low-frequency ghost imaging increases firstly and then decreases, while SNR of high-frequency ghost imaging decreases gradually. Under a suitable threshold, the results are compared with those by directly filtering ghost-image from the traditional ghost imaging. It is shown that better imaging quality can be obtained by using our scheme. To further improve imaging quality, the method of subtracting background before correlation calculation is also presented. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
31. High-Fidelity Imaging Using Compact Multi-Frame Blind Deconvolution.
- Author
-
Hope, Douglas A., Jefferies, Stuart M., and Smith, Cody
- Subjects
DECONVOLUTION (Mathematics) ,SITUATIONAL awareness ,BLIND people ,ATMOSPHERIC turbulence ,SPECKLE interferometry - Abstract
Multi-frame blind deconvolution (MFBD) has been a cornerstone for ground-based space situational awareness of near-Earth satellites since the early 2000's. In 2011 a variation of the classic MFBD algorithm was introduced that required solving for fewer variables than in the classic algorithm, but which still used all the available data to constrain the solution. The initial application of the new approach, referred to as compact multi-frame blind deconvolution (CMFBD), was found to be significantly faster than MFBD, and showed an indication that it may be able to provide restorations of higher quality, i.e. fewer artifacts. Since its introduction, the CMFBD approach has become the foundation of several MFBD-based algorithms that have been developed for applications such as high-accuracy wave front sensing from image plane data, and imaging through strong turbulence: both of which contribute to space situational awareness by increasing the area of sky available for surveillance. Here we show that the performance of the CMFBD approach can be improved through the addition of a new "internal consistency" constraint on the estimated point-spread functions. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
32. Analysis of blood coagulation process based on fractality and dynamic characteristic of laser speckle pattern.
- Author
-
Naomichi Yokoi, Yoshihisa Aizu, and Jun Uozumi
- Subjects
- *
BLOOD coagulation , *SPECKLE interference , *BLOOD testing , *FIBRIN , *BLOOD platelet aggregation - Abstract
The reflection and transmission of coherent light from a biological system can yield information about its condition. In the case of blood exposed to the air, there is a change in the properties of the speckle patterns observed in the coagulation process. This can be studied by means of the rate of temporal variation, the contrast, and also the fractality of patterns. The fractality of the speckle pattern can be investigated by a fractal dimension, which can quantify a level of the complexity of platelet aggregation structure and a fibrin network formed in the process of blood coagulation. In addition, dynamic characteristics of a movement in blood also contain information on the progress of the coagulation process. Fractality and dynamic characteristics are investigated simultaneously for speckle patterns observed in the coagulation process of stored horse blood. Experimental results show the feasibility of the proposed method for detecting hemolysis and formation of platelet aggregation structure and the fibrin network during the coagulation process. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
33. Imaging through scattering layers exceeding memory effect range by exploiting prior information.
- Author
-
Guo, Chengfei, Liu, Jietao, Li, Wei, Wu, Tengfei, Zhu, Lei, Wang, Jiannan, Wang, Gang, and Shao, Xiaopeng
- Subjects
- *
ECHO scattering layers , *OPTICAL imaging sensors , *TRANSVERSAL lines , *SPECKLE interference , *DIFFRACTION patterns - Abstract
Abstract Optical imaging through scattering layers based on the 'memory effect' (ME) always suffers from a limited field of view. Here, we present a method that employs prior information to provide indispensable support for imaging behind a scattering medium, in which case the transversal distance between the targets is beyond the limited range determined by the ME. We experimentally demonstrate that given a known target, or even a light point-source, the other unknown object beyond the ME can be determined with only a single-shot camera image, even if the information of targets are mixed in the speckle pattern. Based on the same concept, we show that our technique is also capable of imaging extended object, whose size is larger than the limited range of ME. This work may have potential in practical applications such as imaging through turbulent medium or the biomedical imaging. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
34. NONINVASIVE IMAGING THROUGH RANDOM MEDIA.
- Author
-
GARNIER, JOSSELIN and SØLNA, KNUT
- Subjects
- *
ENERGY transfer , *THEORY of wave motion , *SPECKLE interferometry , *WAVELENGTHS , *DATA mining - Abstract
When waves propagate through a strongly scattering medium the energy is transferred to the incoherent wave part by scattering. The wave intensity then forms a random speckle pattern seemingly without much useful information. However, a number of recent physical experiments show how one can extract useful information from this speckle pattern. Here we present the mathematical analysis that explains the quite stunning performance of such a scheme for speckle imaging. Our analysis is based on the white-noise paraxial model, in which the wave amplitude is described by the Itô{Schrödinger equation. We identify a scaling regime where the scheme works well, which we refer to as the scintillation regime. In this regime the wavelength is smaller than the correlation radius of the medium, which in turn is smaller than the beam radius; moreover, the propagation distance is longest scale. The results presented in this paper conform with the sophisticated physical intuition that has motivated these schemes, but give a more detailed characterization of the performance. The analysis gives a description of (i) the information that can be extracted and with what resolution and (ii) the statistical stability or signal-to-noise ratio with which the information can be extracted. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
35. Multiexposure laser speckle contrast analysis system calibration limited by perfusion-dependent scattering on the skin.
- Author
-
Smausz, Tamás and Kondász, Bence
- Subjects
- *
SPECKLE interference , *LIGHT scattering , *CALIBRATION , *SPECKLE interferometry , *LASERS , *FOREARM , *PERFUSION , *EVALUATION methodology , *SKIN - Abstract
Application of multiexposure speckle contrast imaging (MESI) methods for perfusion measurements can correct for the contribution of static scattering of the skin, at the expense of reduced temporal resolution as compared to classical single-exposure methods. Persistence of tissue scattering properties during the measurements could allow for an initial calibration and enhancement of the temporal resolution of the measurements. We aim to study the influence of the perfusion on the light scattering of the forearm skin and to use the obtained data for the enhancement of the temporal resolution. A wide range of skin perfusion states was induced while monitoring the changes in the dynamic range of the exposure-dependent contrast. Different measurement and evaluation methods were tested based on an initial MESI calibration followed by image recording with reduced number of exposure time values. The changes in the skin perfusion can alter not only the contribution of the static scattering to the speckle images but also the short-exposure time contrast limit. The perfusion-dependent scattering of the skin can invalidate the precalibrations (e.g., β calibration) characterizing the combination of the given tissue and the measurement system. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
36. Dynamics of laser speckle imaging of blood flow in the tissues at partial temporary pancreatic ischemia of hungry, fed and alcoholized rats
- Author
-
Alexandrov D.A., Timoshina P.A., Tuchin V.V., Maslyakova G.N., Palatova T.V., Sedov D.S., and Izmailov R.R.
- Subjects
intravital microscopy ,pancreas ,reperfusion ,speckle imaging ,Medicine (General) ,R5-920 - Abstract
The aim of the study is to determine the influence of a partial temporary ischemia and reperfusion on the development of pancreatitis in laboratory rats. Material and Methods. The experiments were performed on 73 white rats. Occluded blood vessels and blood flow were recorded by digital biomicroscopy and laser speckle contrast imaging. Statistical data processing was carried out the program Statistica for Windows 6.0 using the Student's criterion. Results. Laser speckle imaging and digital microscopes provide the monitoring of blood flow in the vessels of the pancreas. After a five-minute partial ischemia reactive hyperemia occurs, changes are invertible. After a twenty-minute partial ischemic reactive hyperemia does not occur, without developing pancreatitis necrosis. Pancreas of alcoholized rats has been found out to be more sensitive to ischemia. Conclusion. The method of laser speckle imaging and intravital microscopy after digital five- and twenty-minute partial ischemia of the pancreas revealed phase opposite directed changes in its tissue perfusion and varying severity of postischemic pancreatitis.
- Published
- 2016
37. КОМП’ЮТЕРНА ОБРОБКА СПЕКЛ-ІНТЕРФЕРОГРАМ ДЛЯ ОПТИЧНОГО ДІАГНОСТУВАННЯ БІОЛОГІЧНИХ МІКРООБ’ЄКТІВ
- Subjects
Correlation coefficient ,Computer science ,business.industry ,Image processing ,computer.file_format ,Laser ,JPEG ,law.invention ,Speckle pattern ,Optics ,law ,Speckle imaging ,business ,MATLAB ,computer ,Radiant intensity ,computer.programming_language - Abstract
Problems. Computer processing of speckle interferograms for optical diagnostics of biological micro-objects makes it possible to determine the optical and physical parameters of the components of a biological object. An important characteristic of the developed model is its versatility in its application, which makes it possible to provide the necessary adequacy and uniqueness of optical relationships with the original. During computer processing, the distribution of radiation in the environment of temperature fields is calculated. Purpose. The purpose of modelling is to study the interactions of laser radiation with biological micro-objects to improve and increase the efficiency of laser diagnostics. Implementation technique. For study the interaction of electromagnetic radiation with human erythrocytes, the speckle interferometry method was used, which was taken as the basis for constructing a laboratory bench. The developed laboratory bench made it possible to obtain speckle interferograms for four pathological samples of human erythrocytes. To process speckle interferograms of samples, a computer model was created in the Matlab environment, which allows examining images in JPEG format with a resolution of 72x72 dots per inch. Research results. As a result of computer processing and modelling, the surfaces of the normalized cross-correlation between the two investigated speckle-interferogram samples are calculated. The obtained dependences showed that the largest peak of the correlation coefficient falls on the central part of speckle interferograms of blood samples. The average radiation intensity for the samples does not diverge significantly, but it is shown that the radiation intensity of one of the samples is 12% higher than the radiation intensity for the reference sample. The results presented make it possible to determine the pathology in blood samples based on the study of speckle interferograms in the optical diagnosis of biological objects. Conclusions. The method for determining pathology in human blood samples by studying speckle interferograms of biological objects and computer processing of optical images of samples based on a model in the Matlab environment is proposed. Key words: speckle-interferograms, erythrocytes of blood, diagnostics of biological micro-objects, image processing, model, Matlab
- Published
- 2021
38. A Range and Performance Optimized Version of the Computer-Aided Speckle Interferometry Algorithm for Real-Time Displacement-Strain Field Monitoring
- Author
-
L. Keene
- Subjects
Physics ,Strain (chemistry) ,Mechanics of Materials ,Mechanical Engineering ,Acoustics ,Time displacement ,ComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISION ,Range (statistics) ,Computer-aided ,Speckle imaging ,Field monitoring - Abstract
This work presents an optimized implementation of the Computer-Aided Speckle Interferometry algorithm which enables full-field determination of displacements and strains on commodity Graphics Processing Units at high resolution and frame rates. By combining careful control of the average speckle size in a laser speckle pattern with a simple sampling rate conversion scheme, a compact representation of the optical speckle is achieved. This allows for optimal use of Graphics Processing Unit architecture with robust range extension. The optimal mapping of the Computer-Aided Speckle Interferometry algorithm to Graphics Processing Unit architecture is shown in detail, and a straightforward method for disambiguating large displacements is illustrated. Lastly, this paper demonstrates a two-step subimage-tapering modification to the original algorithm that enables robust range enhancement while maintaining resolution. Results from numerical simulations on synthetic speckle patterns are shown, and runtime performance metrics are provided, with performance ranging up to 60 frames per second in some cases. The method is suitable for interactive experimental mechanics research, process and testing or any application where real-time high-resolution displacement-strain monitoring is needed. A .NET Framework class library enabling the incorporation of the algorithm into 3rd -party applications is available for download.
- Published
- 2021
39. Determining Residual Stresses in Weld Joints of DN 850 Pipes by Spot Drilling Combined with Electronic Speckle Pattern Interferometry
- Author
-
Igor N. Odintsev, Taras P. Plugatar, and Andrey A. Apalkov
- Subjects
Radiation ,Materials science ,business.industry ,Drilling ,Welding ,Condensed Matter Physics ,law.invention ,Optics ,law ,Residual stress ,Electronic speckle pattern interferometry ,General Materials Science ,Speckle imaging ,business - Abstract
Residual welding stresses affect significantly the strength, durability, and performance of structures. Therefore, there is an urgent need for developing and implementing techniques and equipment that allow reliably estimating stresses in experiments. This paper considers some aspects of the joint implementation of electronic speckle pattern interferometry and the spot drilling technique to determine these characteristics under the field conditions. The results of determining the distribution of residual stresses in the weld joint areas of DN 850 pipes are given for various welding modes. The study results are of independent significance and herewith, demonstrate the efficiency of the equipment developed to solve similar problems.
- Published
- 2021
40. Numerical study using finite element method for the thermal response of fiber specklegram sensors with changes in the length of the sensing zone
- Author
-
F. J. Velez, J.D. Arango, Y.A. Vélez, Victor H. Aristizabal, Jorge Herrera-Ramírez, Jairo C. Quijano, and Jorge A. Gómez
- Subjects
Materials science ,Information theory ,numerical approximation and analysis ,business.industry ,010401 analytical chemistry ,fiber optics sensors ,QC350-467 ,Optics. Light ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Finite element method ,0104 chemical sciences ,Computer Science Applications ,010309 optics ,speckle interferometry ,Optics ,0103 physical sciences ,Thermal ,optical sensing and sensors ,Fiber ,Speckle imaging ,Electrical and Electronic Engineering ,Q350-390 ,business ,computational electromagnetic methods - Abstract
The response of fiber specklegram sensors (FSSs) is given as function of variations in the intensity distribution of the modal interference pattern or speckle pattern induced by external disturbances. In the present work, the behavior of a FSS sensing scheme under thermal perturbations is studied by means of computational simulations of the speckle patterns. These simulations are generated by applying the finite element method (FEM) to the modal interference in optical fibers as a function of the thermal disturbance and the length of the sensing zone. A correlation analysis is performed on the images generated in the simulations to evaluate the dependence between the changes in the speckle pattern grains and the intensity of the applied disturbance. The numerical simulation shows how the building characteristic of the length of sensing zone, combined with image processing, can be manipulated to control the metrological performance of the sensors.
- Published
- 2021
41. Dynamics of laser speckle imaging of blood flow and morphological changes in tissues with a full time local ischemia of pancreas
- Author
-
Alexandrov D.A., Timoshina P.A., Tuchin V.V., Maslyakova G.N., Palatova T.V., Skorokhod A.A., Lukashevich K.A., and Yarovoy A.S..
- Subjects
pancreas ,reperfusion ,speckle imaging ,Medicine (General) ,R5-920 - Abstract
The purpose: to establish influence of a full ischemia of different duration and the subsequent reperfusionon pathology development in pancreas of rats by means of laser speckle-visualization and lifetime digital microscopy. Materials and Methods. The work has been performed on 42 white rats of line Wistar in weight of 200-250 Research of properties of a blood-groove was made by means of methods laser Doppler flowmetry, digital biomicroscopy and a method of laser speckle-contrast visualization. Results. After the termination of a 5-minute full ischemia the speed of bloodflow has been increased in 2-3 times, clinic pancreatic necrosis is marked does not develop. After the termination of 20-minute full ischemia the increase in speed of a bloodflow did not occur, there were morphological and clinical signs of pancreatic necrosis. Conclusion, the efficiency of monitoring of microhemodynamics of pancreas in rats by the method of speckle-capillary of full field has been shown. Multidirectional phase of perfusion changes in pancreas have been revealed after reversible infringement of blood supply of different duration.
- Published
- 2014
42. 63‐1: Speckle Reduction for Laser Pico‐projector with Dynamic Deformable Mirrors.
- Author
-
Tsao, Che-Wei, Chen, Hsuan-An, Pan, Jui-Wen, and Yang, Zu-Po
- Subjects
SPECKLE interference ,DIFFUSERS (Fluid dynamics) ,DIFFRACTION patterns - Abstract
This research focuses on speckle noise suppression by changing the angle of divergence of the diffuser. Three types of diffuser designs are compared in the experiments. For all three types, the speckle contrast value is lower than 0.027, and the speckle phenomenon is invisible to the human eye. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
43. Tunable output-frequency filter algorithm for imaging through scattering media under LED illumination.
- Author
-
Zhou, Meiling, Singh, Alok Kumar, Pedrini, Giancarlo, Osten, Wolfgang, Min, Junwei, and Yao, Baoli
- Subjects
- *
LIGHT propagation , *SPECKLE interferometry , *GAUSSIAN function , *FOURIER transforms , *BANDWIDTHS , *MANAGEMENT - Abstract
We present a tunable output-frequency filter (TOF) algorithm to reconstruct the object from noisy experimental data under low-power partially coherent illumination, such as LED, when imaging through scattering media. In the iterative algorithm, we employ Gaussian functions with different filter windows at different stages of iteration process to reduce corruption from experimental noise to search for a global minimum in the reconstruction. In comparison with the conventional iterative phase retrieval algorithm, we demonstrate that the proposed TOF algorithm achieves consistent and reliable reconstruction in the presence of experimental noise. Moreover, the spatial resolution and distinctive features are retained in the reconstruction since the filter is applied only to the region outside the object. The feasibility of the proposed method is proved by experimental results. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
44. Optical Hole-Drilling Residual Stress Calculations Using Strain Gauge Formalism
- Author
-
Gary S. Schajer
- Subjects
Physics ,3D optical data storage ,Digital image correlation ,genetic structures ,Mechanical Engineering ,Computation ,Aerospace Engineering ,Mechanics ,Stress (mechanics) ,Mechanics of Materials ,Residual stress ,Sensitivity (control systems) ,Speckle imaging ,Strain gauge - Abstract
Optical measurement techniques such as digital image correlation and speckle interferometry have been applied to hole-drilling evaluations of residual stress for some decades. These full-field non-contact measurements can have significant advantages over the traditional strain gauge method. However, optical measurements are still only rarely used for practical measurements outside the research environment. A significant barrier to such use is the mathematical challenge of analyzing the large quantity of optical data to evaluate the residual stresses. The objective here is to provide a residual stress computation scheme that can be implemented straightforwardly and efficiently, also to provide the needed calibration data. The approach taken is to recast the optical data into a compact arrangement that parallels the established format used for strain gauge style calculations. Several computation variants are explored, some show high stress sensitivity, while others give resistance to common measurement artifacts. Surface displacement data taken from near the hole edge give the highest stress sensitivity, while more distant data give greater ability to identify interior stresses. The proposed residual stress computation method is shown to be an effective and practical way to compute residual stresses from optical hole-drilling measurements.
- Published
- 2021
45. High-resolution imaging for advances in astronomy
- Author
-
S. K. Saha
- Subjects
Physics ,Wavefront ,business.industry ,Astrophysics::Instrumentation and Methods for Astrophysics ,Atomic and Molecular Physics, and Optics ,law.invention ,Telescope ,Wavelength ,Optics ,law ,Distortion ,Light beam ,Speckle imaging ,Adaptive optics ,business ,Refractive index - Abstract
Two physical phenomena, (i) diameter of the collecting area of a telescope and (ii) turbulence in the atmosphere which introduces fluctuations in the index of refraction along the light beam, limit the minimum resolvable angle at optical and infrared wavelengths. Sharpness of astronomical images thus obtained can be significantly enhanced by using a back end adaptive optics system which reduces the incoming wavefront distortion by suitably deforming a mirror in real-time, and speckle interferometry which is a post-processing technique. The Nobel prize-2020 in physics award to astronomers has recognised the efforts of using these techniques. After a short description of the black hole, this article elucidates the methodology employed to identify such an object having a mass of about 4 million solar masses.
- Published
- 2021
46. Velocity measurement of MEMS with temporal heterodyne microscopic speckle interferometry
- Author
-
Lin Deng, Xu Wang, Chenjia Gao, Yuhao Niu, Jieming Zhao, and Zhan Gao
- Subjects
Heterodyne ,Microelectromechanical systems ,Materials science ,Scale (ratio) ,business.industry ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,010309 optics ,Optics ,Hardware_GENERAL ,0103 physical sciences ,Speckle imaging ,010306 general physics ,business ,Velocity measurement - Abstract
With the rapid development of micro electro mechanical systems (MEMS), the high-precision measurement technology applied to MEMS devices becomes increasingly important. Traditional micro scale meas...
- Published
- 2021
47. SPECKLE INTERFEROMETRY AT THE OBSERVATORIO ASTRONÓMICO NACIONAL. VII
- Author
-
Carlos Guerrero, V. V. Voitsekhovich, Valeri G. Orlov, F. Ortiz, and J. L. Rivera
- Subjects
Physics ,Astronomy ,Astronomy and Astrophysics ,Astrophysics ,Position angle ,01 natural sciences ,law.invention ,Telescope ,Interferometry ,Stars ,Speckle pattern ,Space and Planetary Science ,Limiting magnitude ,law ,0103 physical sciences ,Binary star ,Speckle imaging ,010303 astronomy & astrophysics - Abstract
The results of speckle interferometric measurements of binary stars performed during June, 2016 with the 2.1 m telescope at the Observatorio Astronómico Nacional at SPM (México) are given. We report 480 astrometric measurements of 468 double stars systems. The measured angular separations ρ range from 0’’.091 to 5’’.93. Most of the observed pairs (414 out of 468) are close double stars having separations of ρ ≤ 1’’. We confirm as double stars 59 targets and we found 3 new pairs with separation of less than 1’’. Finally, we show that the high resolution autocorrelation function in polar coordinates allows to easily recover astrometric parameters even in the presence of strong telescope aberrations.
- Published
- 2021
48. Spatial Poincaré Plots as Descriptors of Speckle Pattern Second-Order Statistics
- Author
-
Anindya Majumdar and Sean J. Kirkpatrick
- Subjects
coherence optics ,statistical optics ,speckle ,Fourier optics ,signal processing ,speckle imaging ,Applied optics. Photonics ,TA1501-1820 ,Medical technology ,R855-855.5 - Abstract
It is demonstrated herein that the use of spatial Poincaré plots provides an efficient means to describe short and long-range correlations in the spatial structure of the measured intensity distribution of scattered coherent fields. The intensity distribution over a row of pixels in single frames of speckle fields with varying speckle sizes was considered. Statistical descriptors from the spatial Poincaré plots for these intensity data with variable lags were used to estimate the short and long-term variations in the measured intensities, and from these descriptors, the minimum speckle size in the speckle patterns was estimated. This approach yielded similar results for speckle size estimates as the more standard method of calculating the power spectral density of the intensity pattern and simultaneously provided information on the relative contributions of short-term and long-term variations in the measured intensity to the spatial structure of the scattered fields.
- Published
- 2017
- Full Text
- View/download PDF
49. Instrumental Non-Invasive Diagnostics of the Depth of Skin Burn: Current Opportunities and Unsolved Problems
- Author
-
Ksenia Sergeevna Petrova, Artem Andreevich Karpenko, Svetlana Vladimirovna Nemirova, M. G. Ryabkov, and Igor Evgenievich Pogodin
- Subjects
Dermatoscopy ,medicine.diagnostic_test ,Computer science ,030208 emergency & critical care medicine ,Video microscopy ,Gold standard (test) ,Optical Biopsy ,030207 dermatology & venereal diseases ,03 medical and health sciences ,Speckle pattern ,0302 clinical medicine ,Optical coherence tomography ,medicine ,Medical imaging ,Speckle imaging ,Biomedical engineering - Abstract
Introduction. Burns of various etiologies are on the 3-4 place in frequency among all injuries, they are associated with a high percentage of complications, disability and mortality. Currently, a single algorithm for objective verification of the depth of skin damage has not been developed. Numerous diagnostic technologies used to solve this problem require systemic analysis.The aim of study was to analyze current literature data on technologies for instrumental diagnostics of the depth of thermal damage to the skin.Materials and methods. A search for literary sources in databases was conducted using eLIBRARY.RU, PubMed, Cyberleninka databases. The period of publications was limited to 2011-2020.Results. The method of objective "gold standard" verification of thermal damage to the skin remains a biopsy followed by morphological examination, but the method's traumaticity does not allow it to be used for monitoring the course of the process in dynamics, for multi-focal studies. Among non-invasive methods, dermatoscopy and video microscopy are noted, but the small imaging area and the need for direct contact of the device with the skin surface limit the use of these methods. Laser Doppler flowmetry and imaging are fairly accurate non-contact methods that allow assessing the condition of a burn wound in real time. The method is not applicable to wounds with blisters, insufficient sanitation. Laser speckle contrast imaging is used to evaluate blood flow and is based on the analysis of speckle structure fluctuations. The method allows determining the degree of burn damage depending on changes in the blood flow. However, the method is difficult to apply with a vessel diameter sized 40 microns. The method is sensitive to movement and internal factors. Infrared and Raman spectroscopy are technique for evaluating vibrational patterns in a particular spectrum, these can be used to identify a molecule or determine its structure. Simultaneous use of spatial frequency visualization and speckle imaging demonstrated a high level of correlation with the results of histological research, which makes the use of these methods promising. Ultrasound also provides a proper correlation with histological data, but it is an imperfect method due to inaccuracies in determining the thickness of the epidermis, dermis, and scar condition. Optical coherence tomography (OCT) is a non-invasive optical method that allows obtaining high-resolution images of skin architecture in real time. The high level of compliance of the visualized structures, in particular, layers, appendages and vessels of the skin, with histological findings, gave this method a name "optical biopsy". Anatomical congruence of normal and damaged skin was established in an experiment between histology and OCT.Conclusion. Early assessment of the depth of thermal damage to the skin is crucial for choosing a personalized treatment strategy for the burned. None of the modern diagnostic methods is universal. Multimodal approaches to diagnostics are the most effective.
- Published
- 2021
50. Multi‐wavelength, handheld laser speckle imaging for skin evaluation
- Author
-
Marco De Gregorio, Andreas Wuttig, Sarmiza Elena Stanca, Martin Sattler, Carina Reble, Rainer Riesenberg, Michael Zieger, Robin Sieg, Georg Khazaka, Frank Fischer, Steffen Springer, Mario Kanka, and Martin Kaatz
- Subjects
Skin ageing ,Materials science ,Lasers ,Human skin ,Multi wavelength ,Laser Speckle Imaging ,Dermatology ,Laser ,01 natural sciences ,Skin Aging ,law.invention ,010309 optics ,Laser Speckle Contrast Imaging ,030207 dermatology & venereal diseases ,03 medical and health sciences ,Speckle pattern ,0302 clinical medicine ,Methyl nicotinate ,law ,0103 physical sciences ,Humans ,Speckle imaging ,Skin ,Biomedical engineering - Abstract
Objective A handheld device was developed and qualified for in vivo human skin evaluation using laser speckle imaging technology. Methods Each laser speckle device prototype allows the choice of up to three different laser wavelengths in the range of 400 nm to 800 nm in total. Speckle pattern analysis gives various speckle parameters, for example, speckle contrast, speckle size, speckle modulation or fractal dimension. The developed laser speckle device prototypes were evaluated investigating three skin issues. Results We receive reproducible results from the speckle imaging device. For skin ageing, we found significant changes within three age groups. The effect of a methyl nicotinate treatment was clearly visible and quantifiable using a moorFLPI device as well as our speckle imaging device. In terms of basal cell carcinoma diagnosis, we found significant differences between normal and diseased skin, even though the number of samples was limited. Conclusion As shown with first application examples, it was possible to demonstrate the potential of the method for skin evaluation in vivo.
- Published
- 2020
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.