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Optical Fiber Specklegram Sensors for Mechanical Measurements: a Review
摘要： This paper presents a review of FSS technology. The operation principle and main characteristics of specklegram are presented and the applications of FSSs are thoroughly discussed. In addition, advances in microelectronics, machine learning, material processing for new optical fibers and their relation with FSS are also discussed. These new developments on correlated areas can give rise for a new generation of sensors with advantageous features such as lower cost, easy connectivity, higher degree of customization and better performance.
关键词： Optical fiber sensors,Fiber specklegram sensors,Speckle metrology,Machine learning
更新于2025-09-11 14:15:04
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Oxygen delivery therapy with Epiflo reduceswound hyperperfusionin patient with chronic leg ulcers: a laser speckle contrast analysis.
摘要： BACKGROUND: Transdermal continuous oxygen therapy (TCOT)is today employed in wound careto promote healing by improving local hypoxia and preventing infection, and it has been described to reduce local inflammation over 1 month of administration. The present study aims to investigate the effects of this treatment on wound microcirculation through laser speckle contrast analysis. (LASCA) METHODS: 20 adult patients (mean age: 76 ± 11.5) were prospectively enrolled. Inclusion criteria were: presence of venous or mixed lower limb ulcers from three or more months without dimension reduction, without indication to surgery, weekly treated by our outpatient clinic with silver dressings. Subjects underwent 1 month of TCOT (Epiflo?)in addition to foam dressing. The primary endpoint was the comparisonof ulcer and healthy skin perfusion through LASCA, performed before and after the treatment period. Secondary considered endpoints were wound area, WASI and PUSH Tools 3.0 ulcer severity scales and pain assessment (NRS). RESULTS:Before treatment,the wound area was significantly more perfused than healthy skin(+45%p=.005), at the end of the study this difference was not significant anymore (+20,5% p=.11). Ulcer perfusion decreased, (- 12.5%, p .047), while healthy skin perfusion did not vary significantly. A reduction of the wound dimension (median difference: 2cm , p=.009). and pain (median difference:2 NRS point, p<.001) after therapy were assessed. CONCLUSION: Laser speckle contrast analysis shows that 1 month of transdermal continuous oxygen therapy can help to reduce hyperperfusion of ulcer bed in patients with chronic lower limb ulcers, strengthening the hypothesis that this treatment effectively contrast inflammation. This could correlate with the area and pain reduction assessed, however the absence of control group in this study does not allow a generalization of thishypothesis. Larger, controlled trials are needed to properly assess the relationshipbetween TCOT effects on wound microenvironment and effective healing process.
关键词： TCOT,Oxygen therapy,LASCA,Ulcer,speckle contrast analysis,Chronic wound
更新于2025-09-11 14:15:04
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Microvascular Effects of Pulsed Dye Laser in Combination With Oxymetazoline
摘要： Background and Objective: Oxymetazoline, an α‐1A agonist, is approved by the United States Food and Drug Administration (FDA) for treatment of persistent facial erythema associated with rosacea and induces vasoconstriction by interacting with α receptors. The objective of our study was to study the microvascular effects of oxymetazoline and pulsed dye laser (PDL). Materials and Methods: A dorsal window chamber was surgically installed on 20 mice. Each animal was assigned to one of four experimental groups: saline alone, oxymetazoline alone (10 μl applied once daily × 7 days), saline + PDL (saline applied 5 minutes before PDL irradiation [10 mm spot, 1.5 ms pulse duration, 7 J/cm2 delivered to epidermis]), or oxymetazoline + PDL (10 μl oxymetazoline applied 5 minutes before PDL and then once daily × 7 days). Brightfield and laser speckle imaging were performed for 7 days to monitor vascular architectural and functional changes. Results: We observed persistent blood flow in all of the saline‐only and oxymetazoline‐only experiments. A higher rate of vascular shutdown was observed with oxymetazoline + PDL (66.7%) compared with saline + PDL alone (16.7%). Oxymetazoline application increased venule diameter at 5 minutes post‐application and decreased both arteriole and venule diameters at 60 minutes post‐application. Conclusion: The combination protocol of oxymetazoline + PDL induces persistent vascular shutdown observed 7 days after irradiation. This result may be associated with the acute vascular effects of oxymetazoline. Oxymetazoline + PDL should be evaluated as a treatment for cutaneous vascular disease, including rosacea and port wine birthmarks.
关键词： oxymetazoline,dorsal skinfold,laser speckle contrast,phototherapy
更新于2025-09-11 14:15:04
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Optimierter Laserspeckle-basierter Rauheitsmessprozess für bewegte, spiegelnde Oberfl?chen
摘要： This article describes the upcoming development of a parametric-optical laser measurement system for characterization of surfaces inline some production process. The measurement system is based on previously known approaches for characterization of specular surfaces using coherent light and auto-correlation on the resulting speckle intensity distribution. In order to apply these methods inline, a significantly increased measurement rate has to be reached, compared to existing solutions. This shall be achieved by modifications of the measurement process, use of hardware acceleration for image capturing and processing, and optimization of the processing algorithms.
关键词： speckle,Surface,hardware acceleration,FPGA,scattered light,roughness,laser,metrology
更新于2025-09-11 14:15:04
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Space division multiplexing in standard multi-mode optical fibers based on speckle pattern classification
摘要： In optical communications the transmission bandwidth of single mode optical fibers is almost fully exploited. To further increase the capacity of a telecommunication link, multiplexing techniques can be applied across 5 physical dimensions: amplitude, quadrature, polarization, frequency and space, with all but the latter being nearly exhausted. We experimentally demonstrate the feasibility of an original space division multiplexing technique based on the classification of speckle patterns measured at the fiber’s output. By coupling multiple optical signals into a standard multimode optical fiber, speckle patterns arise at the fiber’s end facet. This is due to quasi-random interference between the excited modes of propagation. We show how these patterns depend on the parameters of the optical signal beams and the fiber length. Classification of the speckle patterns allows the detection of the independent signals: we can detect the state (i.e. on or off) of different beams that are multiplexed in the fiber. Our results show that the proposed space division multiplexing on standard multimode fibers is robust to mode-mixing and polarization scrambling effects.
关键词： space division multiplexing,mode-mixing,speckle patterns,polarization scrambling,optical communications,multimode optical fibers
更新于2025-09-11 14:15:04
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Wavelet Analysis of the Temporal Dynamics of the Laser Speckle Contrast in Human Skin
摘要： Objective: Spectral analysis of laser Doppler ?owmetry (LDF) signals has been widely used in studies of physiological vascular function regulation. An alternative to LDF is the laser speckle contrast imaging method (LSCI), which is based on the same physical principle. In contrast to LDF, LSCI provides non-scanning full-?eld imaging of a relatively wide skin area and offers high spatial and temporal resolutions, which allows visualization of microvascular structure. This circumstance, together with a large number of works which had shown the effectiveness of temporal LSCI analysis, gave impetus to experimental studies of the relation between LDF and LSCI used to monitor the temporal dynamics of blood ?ow. Methods: Continuous wavelet transform was applied to construct a time-frequency representation of a signal. Results: Analysis of 10 minute LDF and LSCI output signals recorded simultaneously revealed rather high correlation between oscillating components. It was demonstrated for the ?rst time that the spectral energy of oscillations in the 0.01-2 Hz frequency range of temporal LSCI recordings carries the same information as the conventional LDF recordings and hence it re?ects the same physiological vascular tone regulation mechanisms. Conclusion: The approach proposed can be used to investigate speckle pattern dynamics by LSCI in both normal and pathological conditions. Signi?cance: The results of research on the in?uence of spatial binning and averaging on the spectral characteristics of perfusion monitored by LSCI are of considerable interest for the development of LSCI systems optimized to evaluate temporal dynamics.
关键词： laser Doppler ?owmetry,oscillations,blood microcirculation,wavelets,laser speckle contrast imaging
更新于2025-09-11 14:15:04
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Revascularization of Free Skin Grafts Overlying Modified Hughes Tarsoconjunctival Flaps Monitored Using Laser-Based Techniques
摘要： Purpose: It has recently been shown that the flap pedicle does not supply blood to a tarsoconjunctival graft in the modified Hughes procedure in patients. This raises questions concerning the rate of revascularization of the free skin graft commonly used to reconstruct the anterior lamella. The aim of this study was, thus, to monitor the course of revascularization in free skin grafts overlying modified Hughes tarsoconjunctival flaps, using laser-based techniques. Methods: Free skin grafts from the upper eyelid or upper arm in 9 patients were used to cover a tarsoconjunctival flap according to the modified Hughes procedure. Blood perfusion was monitored using laser speckle contrast imaging, and vascular reactivity was studied with laser Doppler velocimetry after heating the tissue to 44°C. Measurements were made at the time of surgery (baseline) and at 1, 3, 8, and 16 weeks postoperatively. Results: The gradual increase in perfusion of the free skin grafts during the healing process indicates revascularization. A slight increase in perfusion was seen already after 1 week. Perfusion reached 50% of the baseline after 3 weeks, and complete restoration of perfusion was seen after 8 weeks. The vascular function monitored with heat-induced hyperemia increased in a similar fashion. Conclusions: Full-thickness skin grafts revascularize within 3 to 8 weeks, despite overlying a tarsoconjunctival flap, which has recently been reported to be avascular. This provides further evidence that it should be possible to repair large eyelid defects using free full-thickness eyelid grafts.
关键词： laser Doppler velocimetry,revascularization,laser speckle contrast imaging,free skin grafts,modified Hughes tarsoconjunctival flaps
更新于2025-09-11 14:15:04
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Laser-based Techniques for Microcirculatory Assessment in Orthopedics and Trauma Surgery
摘要： Microcirculatory integrity and proper function are the cornerstones to tissue nourishment and viability. In the clinical environment extended immobility, injuries, and inflammatory reactions demand local microcirculatory adaption to provide adequate supply. Assessment of endothelial adjustment capability and microcirculatory perfusion status, as direct or surrogate markers of disease, are therefore of uttermost interest to the treating physician. Given the simple, noninvasive, nonradiating nature of laser-based techniques for bedside or intraoperative microcirculatory perfusion assessment, this article’s objective is to present a comprehensive overview of available techniques, their technological aspects, and current application. Advantages of individual methods are pointed out and compared with each other. The areas of medical utilization relevant to orthopedics and trauma surgery are exemplified and their available evidence elaborated. A particular focus is put on laser speckle contrast imaging, with its current and future influence on medical practice.
关键词： noninvasive cutaneous microcirculatory perfusion assessment,laser Doppler flowmetry,laser Doppler imaging,Laser speckle contrast imaging
更新于2025-09-11 14:15:04
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Laser Spatial Coherence Suppression With Refractive Optical Elements Toward the Improvement of Speckle Reduction by Light Pipes
摘要： We study laser speckle reduction by light pipes, and we propose a new method to improve its efficiency. Proof-of-concept refractive optical elements (ROEs) with a staircase-like structure are introduced before a holographic diffuser to split a laser beam into laser sub-beams. Optical paths of the laser sub-beams after transmitting through the ROEs are different, and these partially correlated (or uncorrelated) laser sub-beams are added in intensity basis because of the folded mirror reflections by the light pipe. Thus, laser spatial coherence is suppressed, which helps to reduce speckle. We demonstrate this method in a simplified laser projection system, where subjective speckle contrast is reduced from 0.33 to 0.24 before and after introducing a two-dimensional ROE, respectively. Comparing with other improved speckle reduction methods by light pipes, the proposed method is motionless and simpler.
关键词： Speckle reduction,refractive optical element,light pipe
更新于2025-09-11 14:15:04
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[IEEE 2018 IEEE 13th International Scientific and Technical Conference on Computer Sciences and Information Technologies (CSIT) - Lviv, Ukraine (2018.9.11-2018.9.14)] 2018 IEEE 13th International Scientific and Technical Conference on Computer Sciences and Information Technologies (CSIT) - The Methods for Evaluating the Quality of Images with Different Types of Noise
摘要： In the context of evaluating the quality of image recognition systems, it's worth noting that noise is not the only type of interference. Performing such actions on the image as, for example, purposeful modification, rotation or zooming of the image will also have a negative effect on the image resolution. It has been established that one of the reasons for the complication of the decision-making process is the deterioration of the quality of the input information obtained on the basis of various images due to overlaying noise on them, which may have different origin and characteristics. Studying a certain class of noise in the context of considering it as a function allows you to focus on determining its parameters, the degree of influence of these parameters and the artificial noise generation. An overview of the noise of different types and their effects was performed for further evaluation of recognition systems. Noises that arise in this case, are subject to classification in order to study, formalize and further eliminate or minimize their harmful effects. Studying a certain class of noise in the context of considering it as a function allows you to focus on determining its parameters, the degree of influence of these parameters and the artificial noise generation.
关键词： recognition systems quality evaluation,speckle noise,Perlin noise,Gaussian noise,Poisson noise,noise overlaying methods,photographic film grains noise
更新于2025-09-11 14:15:04