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A Strain Distribution Sensing System for Bone-Implant Interfaces Based on Digital Speckle Pattern Interferometry
摘要： This paper aims to provide an effective measurement method for the distribution of deformations and strains focusing on the response to external loading of bone-implant interfaces. To achieve this target, a novel speckle interference imaging method is proposed by introducing phosphate buffer saline medium, in which the samples were completely placed into a phosphate buffer saline solution medium to stable the water molecules. The stability of interferometry imaging is analyzed by using the concepts of co-occurrence matrix and moment of inertia. A series of experiments to measure load-driven deformation and strain in the bone-implant interface was carried out, and the experiments results were analyzed and discussed. It shows that the proposed method is feasible and effective for the no-contact strain measurements of biomaterials in a physiological condition. The proposed strain distribution sensing system will contribute to evaluating computational simulations and improving selection of implant designs and materials.
关键词： digital speckle pattern interferometry,speckle interference imaging,phosphate buffer saline solution,strain distribution detection,bone-implant interface
更新于2025-09-19 17:15:36
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Experimental demonstration of imaging hidden objects in opaque liquid-based media by fusion of single-shot multiview polarized and unpolarized speckle images
摘要： Turbid water-based liquids are common scattering media within which imaging objects is challenging, since scattering particles of various origins and sizes may cause severe image degradation, resulting in poor object recovery and resolution. Therefore, counteracting the nontrivial effects of light scattering is a primary challenge, limiting the utility of optical imaging within liquid media. In this work, we sought to circumvent the optical degradation in turbid liquid media and to recover high-quality images of hidden objects by averaging polarized speckle images projected from several directions through a lens array. Inspired by astronomy imaging techniques, the averaging process utilized a Shift-and-Add (SAA) algorithm developed to reconstruct atmospherically-degraded solar images. Both linear and circular polarization strategies were then applied to further improve image reconstruction. Experiments were carried out using two targets, each having a distinct geometrical shape, embedded within turbid liquid media comprising a range of dilutions of commercially available cow’s milk in seawater. The media were irradiated with a polarized laser beam, after which multiple polarized speckled images were captured with a CCD camera. Offline, images were first shifted to a common center and then fused, using the SAA algorithm, to yield reconstructed images of each hidden object. Quantitative image quality metrics, including SNR, entropy, and sharpness were applied to evaluate quality of the reconstructed images. The reconstructed images obtained demonstrate successful adaptation of our methodology for the identification of hidden objects within turbid media. To the best of our knowledge, this is the first report to demonstrate successful imaging of hidden object images within turbid liquid media by averaging multiple polarized speckle projections.
关键词： Linear and circular polarization,Imaging through turbid water,Lens array,Multiple polarized speckle projections,Image processing
更新于2025-09-19 17:15:36
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Optofluidic laser speckle image decorrelation analysis for the assessment of red blood cell storage
摘要： Red blood cells (RBCs) undergo irreversible biochemical and morphological changes during storage, contributing to the hemorheological changes of stored RBCs, which causes deterioration of microvascular perfusion in vivo. In this study, a home-built optofluidic system for laser speckle imaging of flowing stored RBCs through a transparent microfluidic channel was employed. The speckle decorrelation time (SDT) provides a quantitative measure of RBC changes, including aggregation in the microchannel. The SDT and relative light transmission intensity of the stored RBCs were monitored for 42 days. In addition, correlations between the decorrelation time, RBC flow speed through the channel, and relative light transmission intensity were obtained. The SDT of stored RBCs increased as the storage duration increased. The SDTs of the RBCs stored for 21 days did not significantly change. However, for the RBCs stored for over 35 days, the SDT increased significantly from 1.26 ± 0.27 ms to 6.12 ± 1.98 ms. In addition, we measured the relative light transmission intensity and RBC flow speed. As the RBC storage time increased, the relative light transmission intensity increased, whereas the RBC flow speed decreased in the microchannel. The optofluidic laser speckle image decorrelation time provides a quantitative measure of assessing the RBC condition during storage. Laser speckle image decorrelation analysis may serve as a convenient assay to monitor the property changes of stored RBCs.
关键词： laser speckle,image decorrelation,microfluidic channel,Optofluidic,RBC aggregation,speckle decorrelation time,red blood cell storage
更新于2025-09-19 17:13:59
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Development of a non-contact and non-destructive laser speckle imaging system for remote sensing of anisotropic deformation around fastener holes
摘要： Strain sensing around the fastener holes is fundamentally significant in structural health monitoring and failure detections. Conventional non-destructive testing (NDT) techniques typically have limitations in performing reliable and efficient inspections. Here, a laser speckle imaging system (LSIS) has been developed to achieve non-contact, non-destructive and remote strain sensing. Methods for determining optimal laser speckle patterns have been investigated to achieve remote sensing of strain up to a working distance of 5 m. This LSIS was applied to study the anisotropic properties of un-notched and circular notched specimens in cold-rolled aluminium sheet, an important material for the construction of lightweight aircraft structures. The results showed that strain distributions determined by LSIS are consistent with finite element (FE) predictions in which the evolution of strain concentrations not only depends on the notch size but also on material anisotropy. This study demonstrates the potential application of LSIS as an effective NDT technique for full-field, non-contact and remote sensing of anisotropic deformation around fastener holes.
关键词： Non-destructive testing,Digital image correlation,Laser speckle imaging,Remote strain sensing
更新于2025-09-19 17:13:59
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Comparison of Neurovascular Coupling between Normal Tension Glaucoma Patients and Healthy Individuals with Laser Speckle Flowgraphy
摘要： Background The purpose of this pilot study was to investigate the differences in neurovascular coupling between Caucasian patients with normal tension glaucoma (NTG) and healthy subjects (HS) with Laser Speckle Flowgraphy (LSFG). Methods Measurement of optic nerve head blood flow was performed with LSFG. Mean blur rate of the whole optic nerve head (MA), of the big retinal vessels (MV) and of the microvasculature (MT) was analysed during continuous flicker light stimulation for four minutes. Results We included 12 eyes from 12 Caucasian patients with diagnosis of normal tension glaucoma and 12 eyes from 12 age- and sex-matched healthy individuals. MA, MV and MT all increased significantly in both groups during the observation period with no difference between the groups. Conclusion Neurovascular coupling is detectable in NTG patients. Flicker light stimulation leads to a comparable increase in ocular blood flow in glaucoma patients and healthy individuals.
关键词： flicker,laser speckle flowgraphy,ocular perfusion,normal tension glaucoma,neurovascular coupling
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Integration of Photovoltaic Systems into Smart Grids Demonstration of Solar-, Storage and E-Mobility Applications within a Secure Energy Information Network in Germany
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2025-09-19 17:13:59
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Color speckle measurement of white laser beam emitted from fiber output of RGB laser modules
摘要： Color speckle metrics of an RGB-combined white laser beam emitted from an optical fiber output of two types of RGB laser module are measured. A new method for eliminating the effects of a fiber far field pattern from the measured 2D speckle data is employed to calculate the speckle metrics with a statistical accuracy. In this method, unspeckled 2D data of the far field pattern can be directly measured by opening the iris of the speckle measurement equipment. As a result, white photometric speckle contrast and color speckle distribution in CIE1931 chromaticity diagram are, for the first time, successfully obtained by eliminating the far field pattern effects.
关键词： Optical fiber,Color speckle,Far field pattern,Laser module,Speckle
更新于2025-09-16 10:30:52
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Polychromatic speckle reduction in laser pico-projectors using stationary dual Hadamard diffusers
摘要： Speckle from coherent light sources continues to be a limiting factor in the design and manufacturing of laser projectors. Utilizing diffractive diffusers has been an effective method for reducing monochromatic speckle contrast. Color laser projection devices require the use of red, green, and blue laser sources therefore; using a monochromatic diffractive diffuser may not be optimal for color speckle contrast reduction. A new static dual-diffuser system utilizing Hadamard matrices has been designed to reduce full color speckle. This paper analyzes the effectiveness of the new Hadamard diffusers in reducing speckle using three separate RGB laser diodes. A simulation of the Hadamard diffusers is conducted to determine the optimum spacing between the two diffusers for polychromatic speckle reduction. Experimental measured results are presented using the optimal spacing of Hadamard diffusers for RGB color speckle reduction showing 60% reduction in contrast.
关键词： speckle contrast reduction,Hadamard matrix,diffractive diffusers,Polychromatic speckle,laser pico-projectors
更新于2025-09-16 10:30:52
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Laser speckle imaging of flowing blood: A numerical study
摘要： Laser speckle imaging (LSI) can be used to study dynamic processes in turbid media, such as blood flow. However, it is presently still challenging to obtain meaningful quantitative information from speckle, mainly because speckle is the interferometric summation of multiply scattered light. Consequently, speckle represents a convolution of the local dynamics of the medium. In this paper, we present a computational model for simulating the LSI process, which we aim to use for improving our understanding of the underlying physics. Thereby reliable methods for extracting meaningful information from speckle can be developed. To validate our code, we apply it to a case study resembling blood flow: a cylindrical fluid flow geometry seeded with small spherical particles and modulated with a heartbeat signal. From the simulated speckle pattern, we successfully retrieve the main frequency modes of the original heartbeat signal. By comparing Poiseuille flow to plug flow, we show that speckle boiling causes a small amount of uniform spectral noise. Our results indicate that our computational model is capable of simulating LSI and will therefore be useful in future studies for further developing LSI as a quantitative imaging tool.
关键词： speckle boiling,Laser speckle imaging,computational model,quantitative imaging,blood flow
更新于2025-09-16 10:30:52
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Sharp Small-Scale Perturbations of Fringes at the Interference of Dispersed Broad-Spectrum Laser Beams
摘要： The interference of two dispersed laser speckle-?elds with a great spectrum width has been studied by numerical modeling. Local small-scale perturbations of interference fringes with an abrupt drop of contrast in the interference picture have been revealed. It has been shown that these perturbations occur in the region of a large phase gradient and a small module of the mutual coherence function of coinciding interfering ?elds. The analytical description of small-scale perturbations is given, and the probability of their appearance is estimated.
关键词： dispersed beams,phase singularity,broadband laser radiation,interference,speckle ?elds
更新于2025-09-16 10:30:52