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A new simulation method for laser speckle imaging to investigate hemodynamics
摘要： Speckle simulation is a powerful protocol to investigate the properties of speckle and evaluate image processing method. However, only static speckle images can be simulated by available methods without considering time-integrated effect of CCD. A time-integrated dynamic speckle simulation method based on coherent imaging was developed. Through the new simulation method, the effect of speckle size on LSCI was investigated. The smaller the speckle size is, the higher the spatial resolution become. But the one-dimensional speckle size should exceed two pixels to sample the speckle pattern. The characteristics of existing speckle contrast imaging methods were studied based on spatial statistics, and optimal parameters are given to obtain accurate and less noisy image. In general, the new simulation method for laser speckle imaging is a powerful tool to monitor blood flow in vivo and lay a solid foundation for the study of hemodynamics.
关键词： hemodynamics,speckle size,laser speckle imaging,spatial resolution,simulation method
更新于2025-09-23 15:19:57
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Development of laser speckle blood flowmeter for evaluating the physiological function of skin
摘要： Objective: We developed and demonstrated laser speckle ?owgraphy (LSFG) for two-dimensional (2D) skin blood ?ow (SBF) measurements to facilitate the noninvasive comparisons of SBF between individuals. Approach: By using morphing technology with a face mesh to compare SBF spatial distributions among individuals, we examined the practicability of SBF measurement with LSFG. Main results: (1) The uniformity of SBF measurement was demonstrated by examinations at different distances and angles for healthy subjects. (2) Mean blur rate (MBR)—a blood ?ow index of LSFG—exhibited signi?cant correlation with the thermal diffusion method (TDM)—an established blood ?ow measurement method—suggesting that MBR is an effective index of SBF. (3) Blowout time, the half-width duration/duration of one cardiac cycle, exhibited signi?cant negative correlation with age and positive correlation with stratum corneum hydration. Signi?cance: These results suggest that LSFG is useful for evaluating SBF-related skin properties, and it has signi?cant potential in medicine and cosmetology.
关键词： aging,stratum corneum hydration,skin blood ?ow,laser speckle ?owgraphy,morphing,strain-gauge plethysmography,thermal diffusion
更新于2025-09-23 15:19:57
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Laser speckle reduction utilized by lens vibration for laser projection applications
摘要： In this paper, a compact speckle reduction method utilizing vibrating lenses for laser beam scanning is proposed and demonstrated. The maximum speckle reduction ef?ciency was found to be 75.6% and 81.25% for a 532 nm diode-pumped solid-state (DPSS) laser and a 520 nm laser diode (LD), respectively. The minimum speckle contrast ratio observed using our method was 0.11 for the DPSS laser and 0.06 for the LD. The proposed method can provide speckle reduction with minimal power requirements, a low implementation cost, and no bending for the optical path of the laser beam. Additionally, this method is promising to withstand high-power lasers for use in high lumen laser projectors by optimizing the lens parameters. The demonstrated technique has a small form factor while simultaneously demonstrating a high degree of speckle reduction, which shows potential for speckle reduction in mini- and pico- laser projector applications.
关键词： pico-projectors,compact method,laser displays,vibrating lens,speckle reduction,mini-projectors,low cost
更新于2025-09-23 15:19:57
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Ocular blood flow by laser speckle flowgraphy to detect cerebral ischemia during carotid endarterectomy
摘要： Laser speckle flowgraphy (LSFG) is a noninvasive technique that can measure relative blood flow velocity in the optic fundus contributed by the ophthalmic artery, the main first branch originating from the internal carotid artery (ICA). The aim of this study was to assess the feasibility of ocular blood flow measurement by LSFG to detect ischemic stress due to carotid clamping during carotid endarterectomy (CEA). Nineteen patients undergoing CEA with ocular blood flow measurement by LSFG and intraoperative monitoring (IOM) were prospectively enrolled between August 2016 and March 2019. The mean blur rate (MBR) of ocular blood flow by LSFG, representing relative blood flow of the branch of the retinal artery originating from the optic nerve head, was compared between before and after carotid clamping during CEA. The correlation between the reduction ratio of MBR and the regional saturation oxygen (rSO2) index by near infrared spectroscopy was investigated. Ocular blood flow measurement by LSFG could not be performed in one patient with a severe cataract. In the other 18 patients, LSFG could be performed in all 106 sessions during surgery. The MBR reduction ratio between before and after carotid clamping ranged from ? 12 to 100%. The MBR reduction ratio was positively correlated with the rSO2 index (r = 0.694, 95% confidence interval: 0.336–0.877, p = 0.001). The MBR reduction ratio of ocular blood flow by LSFG after carotid clamping was significantly correlated with the rSO2 index. The ocular blood flow by LSFG could be considered an adjunct modality for evaluating cerebral ischemic tolerance during CEA.
关键词： Ocular blood flow,Laser speckle flowgraphy,Cerebral blood flow,Carotid endarterectomy
更新于2025-09-23 15:19:57
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Illumination dependency in dynamic laser speckle analysis
摘要： We analyse how the frequency bands influence the independence of speckle index values from the level of illumination in a dynamic laser speckle analysis. Specifically, we study how the temporal speckle deviation index is influenced by the use of three different frequency bands of the speckle signal. Finally, it is shown how signals with high frequency components return values with greater independence of the level of illumination.
关键词： Biospeckle signal,Biospeckle index,Biospeckle laser,Biological activity,Dynamic speckle
更新于2025-09-23 15:19:57
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Comparison of two skin temperature assessment methods after the application of topical revulsive products: Conductive iButton data logger system vs contact-free infrared thermometry
摘要： Background: Skin temperature assessments comprise conductive and contact-free techniques. Comparison between conductive data loggers and contact-free thermometry after the application of revulsive products is scarce. This study aimed to compare iButton data loggers with an infrared thermometer after the application of two revulsive products. Secondly, the relation between skin temperature kinetics with skin's perfusion of microcirculation was investigated. Materials and methods: Healthy females (n = 25) were randomly allocated to two groups, representing the products A and B. Skin temperature was measured with “iButtons” and an infrared pistol at baseline and up to 1 hour after application. Skin's perfusion of microcirculation was monitored with a laser speckle contrast imager. Results: Baseline “iButton” temperature values were significantly lower compared with infrared pistol values in both groups. After application of the products, skin temperature decreased as recorded with both devices followed by an increase to baseline values when measured with the pistol. The results obtained by the “iButtons” reached values above baseline in both products towards the end of the follow-up period. A moderate correlation was found between infrared pistol and “iButton” system in product A, with a weak negative correlation between skin's perfusion of microcirculation and temperature devices. For product B, the correlation between the devices was moderate and between skin's perfusion and temperature devices weak and positive. Conclusion: Both devices produced similar kinetics, except at baseline, where they may differ as metallic loggers have been insufficiently adapted to skin temperature. Skin's perfusion of microcirculation could not explain skin temperature changes.
关键词： thermocouples,laser speckle contrast imaging,infrared thermography,skin temperature,revulsive products
更新于2025-09-23 15:19:57
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Double-pulse speckle contrast correlations with near Fourier transform limited free-electron laser light using hard X-ray split-and-delay
摘要： the ability to deliver two coherent X-ray pulses with precise time-delays ranging from a few femtoseconds to nanoseconds enables critical capabilities of probing ultra-fast phenomena in condensed matter systems at X-ray free electron laser (feL) sources. Recent progress made in the hard X-ray split-and-delay optics developments now brings a very promising prospect for resolving atomic-scale motions that were not accessible by previous time-resolved techniques. Here, we report on characterizing the spatial and temporal coherence properties of the hard X-ray feL beam after propagating through split-and-delay optics. Speckle contrast analysis of small-angle scattering measurements from nanoparticles reveals well-preserved transverse coherence of the beam. Measuring intensity fluctuations from successive X-ray pulses also reveals that only single or double temporal modes remain in the transmitted beam, corresponding to nearly fourier transform limited pulses.
关键词： spatial coherence,split-and-delay optics,speckle contrast,temporal coherence,X-ray Free Electron Lasers
更新于2025-09-23 15:19:57
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Ghost imaging at an XUV free-electron laser
摘要： Here we present the results of a classical ghost imaging experiment accomplished at an XUV free-electron laser (FEL). To perform such experiment at an FEL source each x-ray pulse was transmitted through a moving diffuser, which created a noncorrelated speckled beam. This beam was then split in two identical branches by introducing a beam splitter in the form of a transmission grating. In one of these branches the sample was positioned. We demonstrate the possibility of image formation, a double bar in our case, in the beam that has never interacted with the sample. With this experiment we extend the quantum optics methodology to the FEL community.
关键词： XUV free-electron laser,speckle pattern,quantum optics,ghost imaging,transmission grating
更新于2025-09-23 15:19:57
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[IEEE 2019 6th International Conference on Systems and Informatics (ICSAI) - Shanghai, China (2019.11.2-2019.11.4)] 2019 6th International Conference on Systems and Informatics (ICSAI) - An electromagnetic and piezoelectric coupled energy harvester using cantilever beam for low frequency vibration
摘要： With the emergence of the Microsoft Kinect sensor, many developer communities and research groups have found countless uses and have already published a wide variety of papers that utilize the raw depth images for their specific goals. New methods and applications that use the device generally require an appropriately large ensemble of data sets with accompanying ground truth for testing purposes, as well as accurate models that account for the various systematic and stochastic contributors to Kinect errors. Current error models, however, overlook the intermediate infrared (IR) images that directly contribute to noisy depth estimates. We, therefore, propose a high fidelity Kinect IR and depth image predictor and simulator that models the physics of the transmitter/receiver system, unique IR dot pattern, disparity/depth processing technology, and random intensity speckle and IR noise in the detectors. The model accounts for important characteristics of Kinect’s stereo triangulation system, including depth shadowing, IR dot splitting, spreading, and occlusions, correlation-based disparity estimation between windows of measured and reference IR images, and subpixel refinement. Results show that the simulator accurately produces axial depth error from imaged flat surfaces with various tilt angles, as well as the bias and standard lateral error of an object’s horizontal and vertical edge.
关键词： simulation,Computer-aided design (CAD),Microsoft Kinect,infrared (IR) dot pattern,structured-light 3-D scanner,speckle noise
更新于2025-09-23 15:19:57
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Uniformity and isotropy of speckle pattern cause the doubled random error phenomenon in digital image correlation
摘要： For subset-based digital image correlation, the random error of second-order shape function roughly doubles that of first-order shape function, termed doubled random error phenomenon. In this work, we suggest that the fundamental cause of this phenomenon is the uniformity and isotropy of speckle pattern. Specially, we prove that the ratio of random error of second-order shape function to that of first-order shape function, from a view of statistic, is expected to be √7∕2 (≈1.87), which is quite close to the empirical value 2. Numerical experiments demonstrate the correctness of propose theoretical analysis.
关键词： Speckle pattern,Digital image correlation,Random error,Statistical analysis
更新于2025-09-23 15:19:57