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- 2018
- railway track
- kinematic characteristics
- stereo vision
- image blur
- distance estimation
- control system
- depth of field
- video monitoring
- hollows classification
- RGB-D camera
- Optoelectronic Information Science and Engineering
- Chongqing University of Posts and Telecommunications
- Bauman Moscow State Technical University
- Moscow State University of Railway Engineering
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Inline weld depth measurement for high brilliance laser beam sources using optical coherence tomography
摘要： As a result of the rapidly growing importance of applications in electro mobility that require a precisely defined laser weld depth, the demand for inline process monitoring and control is increasing. To overcome the challenges in process data acquisition, this paper proposes the application of a novel sensor concept for deep penetration laser beam welding with high brilliance laser sources. The experiments show that optical coherence tomography (OCT) can be used to measure the weld depth by comparing the distance to the material surface with the distance to the keyhole bottom measured by the sensor. Within the presented work, the measuring principle was used for the first time to observe a welding process with a highly focused laser beam source. First, a preliminary experimental study was carried out to evaluate the influence of the angle of incidence, the material, and the weld joint geometry on the quality of the sensor signal. When using a multimode fiber laser with a focus diameter of 320 μm, the measurements showed a distinct behavior for aluminum and copper. The findings about the measurement signal properties were then applied to laser beam welding with a single-mode fiber laser with a spot diameter of only 55 μm. The spot diameter of the OCT measuring beam was about 50 μm and thus only slightly smaller than that of the single-mode processing beam. A wide variety of tests were carried out to determine the limits of the measurement procedure. The results show that the application of OCT allows inline monitoring of the weld depth using both a multimode and a highly focused single-mode laser beam. In addition, various influences on the signal were identified, e.g., the material-specific melt pool dynamics as well as several characteristic reflection and absorption properties.
关键词： high brilliance laser beam sources,weld depth measurement,optical coherence tomography,laser beam welding
更新于2025-11-28 14:24:20
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Optical Fiber Sensor Performance Evaluation in Soft Polyimide Film with Different Thickness Ratios
摘要： To meet the application requirements of curvature measurement for soft biomedical robotics and flexible morphing wings of aircraft, the optical fiber Bragg grating (FBG) shape sensor for soft robots and flexible morphing wing was implemented. This optical FBG is embedded in polyimide film and then fixed in the body of a soft robot and morphing wing. However, a lack of analysis on the embedded depth of FBG sensors in polyimide film and its sensitivity greatly limits their application potential. Herein, the relationship between the embedded depth of the FBG sensor in polyimide film and its sensitivity and stability are investigated. The sensing principle and structural design of the FBG sensor embedded in polyimide film are introduced; the bending curvatures of the FBG sensor and its wavelength shift in polyimide film are studied; and the relationship between the sensitivity, stability, and embedded depth of these sensors are verified experimentally. The results showed that wavelength shift and curvature have a linear relationship. With the sensor’s curvature ranging from 0 m?1 to 30 m?1, their maximum sensitivity is 50.65 pm/m?1, and their minimum sensitivity is 1.96 pm/m?1. The designed FBG sensor embedded in polyimide films shows good consistency in repeated experiments for soft actuator and morphing wing measurement; the FBG sensing method therefore has potential for real applications in shape monitoring in the fields of soft robotics and the flexible morphing wings of aircraft.
关键词： polyimide film,sensitivity,micro curvature sensor,soft robotics sensor,embedded depth
更新于2025-11-28 14:24:03
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CO2 laser interactions with wood tissues during single pulse laser-incision
摘要： Incising is a technique used to improve fluid flow in impermeable woods during wood treatment processes. Previous studies relating to the laser-incision of wood have neglected many aspects such as detailed analysis of the anatomy of the wood, including consideration of tangential/radial faces and earlywood/latewood interactions with the laser beam. By considering wood anatomy, a complete investigation of the CO2 laser-incision processes is presented that yields new knowledge of laser beam interaction with growth rings when incising into tangential/radial faces, and the low-density earlywood and higher density latewood within the growth ring. Southern Yellow Pine, Radiata Pine, European Redwood and Beech, each having different bulk densities, were laser-incised using a 2 kW ROFIN CO2 laser with radiation in the far-infrared regime (10.6 μm). Microstructural characterisations were carried out to better understand the effect of CO2 laser-incision and its parameters on the depth, diameter and quality of the incised holes. The laser-incised hole shapes were found to be uniform in depth, however, the hole circularity was significantly affected by the presence of earlywood and latewood tissues. Maximum and minimum diameters of incised holes were measured in the Radiata Pine (~1.3 mm) and in the Beech (~0.7 mm), respectively. Similarly, for equal laser powers used, the maximum and minimum depths of laser-incised holes were measured in the European Redwood (~33 mm) and in the Beech (~25 mm), respectively, with the laser incident on the radial face of the samples. CO2 laser pulse duration had a greater effect on diameter and depth of incised holes when compared to laser power and showed that the CO2 laser pulse duration is a dominant parameter when designing CO2 laser-incision processes.
关键词： Laser-incision,Wood,Circularity,Depth,Diameter,CO2 laser
更新于2025-11-21 11:24:58
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Three-dimensional Nanoscale Mapping of Porosity in Solution-Processed ITO Multilayer Thin Films for Patternable Transparent Electrodes
摘要： Indium tin oxide (ITO) films constitute components of many layered heterostructures used for emergent technologies beyond conventional optoelectronics. Compositional and morphological changes have a direct impact on the device’s performance. Hence control over the morphology with advanced multimodal characterization approaches are required to evaluate the devices. Herein multilayer ITO films deposited by spin coating were quantified in nanoscale detail in three dimensions by combining results from depth-sensitive neutron reflectometry (NR), non-contact topographic AFM images and cross-sectional SEM images. Films with different number of deposited layers were visually transparent even though the topmost layer was as high as 60% porous, with porosity gradually decreasing as the number of the underneath sublayers increased. Surface and interfacial roughness through the total film and individual layer thickness were obtained. NR data also furnished quantitative depth information on the films chemical composition and layer-by-layer bulk density, which has never been obtained before, providing a way to monitor and ultimately control the sheet resistivity via the pore network. When the same formulation is used for inkjet printing patterns, the larger pores disappear and the optical properties are improved to >90% transmittance at all visible wavelengths. All 5L films achieved sheet resistivities as low as 10-2 ?-cm and can therefore be used as patternable transparent electrodes for many devices including liquid crystal displays.
关键词： thin multilayer film,neutron reflectometry,depth density distribution,neutron absorption reflectometry,Indium tin oxide,porosity,structure chemical depth profile,off-specular neutron scattering,layer by layer deposition
更新于2025-11-19 16:56:35
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Single process CVD growth of hBN/Graphene heterostructures on copper thin films
摘要： In this study, we have successfully grown hBN/graphene heterostructures on copper thin films using chemical vapor deposition in a single process. The first and most surprising result is that graphene grows underneath hBN and adjacent to the Cu film even though it is deposited second. This was determined from cross-sectional TEM analysis and XPS depth profiling, which chemically identified the relative positions of hBN and graphene. The effect of various growth conditions on graphene/hBN heterostructures was also studied. It was found that a pressure of 200 torr and a hydrogen flow rate of 200 sccm (;1 H2/N2) yielded the highest quality of graphene, with full surface coverage occurring after a growth time of 120 min. The resulting graphene films were found to be approximately 6–8 layers thick. The grain size of the nanocrystalline graphene was found to be 15–50 nm varying based on growth conditions.
关键词： XPS depth profiling,copper thin films,TEM analysis,hBN/graphene heterostructures,chemical vapor deposition
更新于2025-11-14 14:32:36
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Illumination conditions in microsphere-assisted microscopy
摘要： White-light microsphere-assisted microscopy is a full-field and label-free imaging promising technique making it possible to achieve a sub-diffraction lateral resolution. However, performance of this technique depends not only on the geometrical parameters but also on the illumination conditions of the optical system. In the present work, experimental measurements and computer simulations have been performed in air in order to determine the influence of the two diaphragm apertures of the K?hler arrangement and the spectral width of the light source on both the depth-of-focus of the microsphere and the optimisation of the imaging contrast. Furthermore, the super-resolution phenomenon is demonstrated and the cumulated optical aberrations are shown through the measurement of the optical transfer function for the different arrangements of the illumination part.
关键词： Super-resolution microscopy,Illumination,Microsphere,Optical transfer function,Imaging depth
更新于2025-10-24 16:39:32
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Choroidal thickness in healthy eyes using enhanced depth imaging optical coherence tomography and comparison with cases of retinitis pigmentosa
摘要： Introduction. — The goal of this study was to measure by spectral domain optical coherence tomography (SD-OCT) with EDI the choroidal thickness in healthy subjects and to compare these parameters with those of patients with retinitis pigmentosa (RP). Methods. — Data were obtained from 60 healthy patients without history or family history of retinal or choroidal disease or glaucoma. A case-control study was also conducted on 40 eyes of 20 patients with RP and 40 eyes of 20 healthy refraction- and age-matched controls, selected from among the 60 healthy patients. OCT was used with the EDI protocol. The primary outcome measure was choroidal thickness. Results. — Among healthy patients, the overall choroidal thickness was 287.7 μm. Mean choroidal thickness was lower on the nasal side (236.6 μm from the fovea) compared with the temporal side (262.3 μm, P = 0.002). It also varied according to age, being highest among 20—29-year-old patients and decreasing thereafter with increasing age. Choroidal thickness was significantly higher in healthy patients than in RP patients, regardless of the location (P < 0.001). Conclusion. — This observational study confirms that choroidal thickness varies with age and location. It decreases in subjects with RP and is related to worsening of retinal damage, independently of age-related thinning. Further studies are needed to understand whether choroidal vascular alteration is a cause or a consequence of the degenerative pathology.
关键词： Photoreceptor degeneration,Choroidal thickness,Case-control study,Retinitis pigmentosa,Enhanced depth imaging optical coherence tomography
更新于2025-09-23 15:23:52
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Geometric parameters effect of the atomic force microscopy smart piezoelectric cantilever on the different rough surface topography quality by considering the capillary force
摘要： Nowadays, the atomic force microscopy (AFM) is widely used in the nanotechnology as a powerful nano-robot. The surface topography in Nanoscale is by far one of the most important usages of the AFM device. Hence, in this article, the vibration motion of a piezoelectric rectangular cross-section micro-cantilever (MC) which oscillates in the moist environment has been examined based on the Timoshenko beam theory. After extracting the MC governing equations according to Hamilton's principle, the finite element method has been used to discretize the motion equations. The surface topography has been simulated for various roughness forms in the tapping and non-contact modes by considering the effects of the Van der Waals, capillary and contact forces. Also, the experimental results obtained from the glass surface topography have been simulated. The results illustrate that the time delay in higher natural frequencies in the tapping mode is shorter in comparison with the non-contact mode, especially, for the lower natural frequencies. The sensitivity analysis of the natural frequencies, topography depth and time delay have been simulated. Results indicate that the most effective parameter is the MC length. In the first mode, the first section length has the highest effect on the surface topography time delay, also, in the second vibration mode; the most effective parameter on the time delay is the MC tip length based on the simulation results.
关键词： AFM piezoelectric micro-cantilever,Timoshenko beam,sensitivity analysis,finite element method,topography depth
更新于2025-09-23 15:23:52
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Multi-step approach for automated scaling of photogrammetric micro-measurements
摘要： Photogrammetry can be used for the measurement of small objects with micro-features, with good results, low costs, and the possible addition of texture information to the 3D models. The performance of this technique is strongly affected by the scaling method, since it retrieves a model that must be scaled after its elaboration. In this paper, a fully automated multi-step scaling system is presented, which is based on machine vision algorithms for retrieving blurred areas. This method allows researchers to find the correct scale factor for a photogrammetric micro model and is experimentally compared to the existing manual method basing on the German guideline VDI/VDE 2634, Part 3. The experimental tests are performed on millimeter-sized certified workpieces, finding micrometric errors, when referred to reference measurements. As a consequence, the method is candidate to be used for measurements of micro-features. The proposed tool improves the performance of the manual method by eliminating operator-dependent procedures. The software tool is available online as supplementary material and represents a powerful tool to face scaling issues of micro-photogrammetric activities.
关键词： Depth from focus,Photogrammetry,Micro-features,Measurement,International standards,Image analysis,Scale
更新于2025-09-23 15:23:52
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Thermoluminescent behavior of UV and γ rays irradiated Eu2+ and Er3+doped silicate phosphors
摘要： This paper reports the structural, morphological and thermoluminescent studies of Eu2+ and Er3+ ions activated ASiO3 (A= Ca, Ba, Sr) phosphors synthesized via conventional solid state reaction method. The impurity ions concentration of both Eu2+ and Er3+ ions varies from 0 mol% to 1 mol%. The study of crystallographic traits of the synthesized phosphors is done by Powder X-Ray Diffraction (PXRD) analysis. The crystalline nature, phase purity and appreciable homogeneity of the synthesized phosphors were confirmed by this study. The distinct morphological and topographical features were studied through Field Emission Scanning Electron Microscopy (FESEM) and Transmission Electron Microscopy (TEM). The thermoluminescent (TL) behavior of ultraviolet (UV) irradiated and gamma irradiated ASiO3:Eu2+, Er3+ (A= Ca, Ba, Sr) phosphors were studied here and the various kinetic parameters were estimated by Computerised glow curve deconvolution (CGCD) technique and peak shape method. The UV and gamma irradiated phosphors exhibit second order kinetics. The high values of activation energy (~ 3 eV) confirm the trapping of electrons in deep trap centers. The incorporation of doping ions into the host lattice causes non-valence substitutions at the substitutional sites. This increases the number of defects and vacancies in the phosphors and more trap centers were generated. The increased TL intensity and high temperature glow peaks confirm the same. The synthesized phosphors show enhanced TL characteristics, efficient trapping mechanism and low fading effects. These characteristics confirm the suitability of the synthesized phosphors for TL mapping and sensing applications.
关键词： Alkaline earth silicates,Thermoluminscence,Activation energy,Trap depth,Order of kinetics.
更新于2025-09-23 15:23:52