1. Articles in category: NDE/NDT

    1-24 of 350 1 2 3 4 ... 13 14 15 »
    1. Frustrated total internal reflection fingerprint detector

      Frustrated total internal reflection fingerprint detector

      The device provides an optical coherence tomography system; a first bank of light emitting diodes emitting light centered about a first wavelength; a second bank of light emitting diodes, emitting light centered about a second wavelength; a prism, said prism including a first surface transmissive of the wavelength of the probe beam of the optical coherence tomography system, and a second surface which is also transmissive of the wavelength of the probe beam, and where the second is surface coated from a first edge to a midpoint so to be reflective of light at the first wavelength and transmissive of ...

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    2. Focus Tracking System for Femtosecond Laser Machining using Low Coherence Interferometry

      Focus Tracking System for Femtosecond Laser Machining using Low Coherence Interferometry

      We designed a real time, single-laser focus tracking system using low coherence properties of the machining femtosecond laser itself in order to monitor and correct the sample position relative to the focal plane. Using a Michelson Interferometer, the system collects data arising from part of the beam backscattered at the ablation spot. The data is analyzed by a custom software for position correction (employing an XYZ automated translation stage). With the focus tracking enabled we were able to etch channels with a stable cross-section profile on a bovine tooth with relief amplitude tens of times greater than the Rayleigh length ...

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      Mentions: Marcus P. Raele
    3. Microscale light management and inherent optical properties of intact corals studied with optical coherence tomography

      Microscale light management and inherent optical properties of intact corals studied with optical coherence tomography

      Coral reefs are highly productive photosynthetic systems and coral optics studies suggest that such high efficiency is due to optimized light scattering by coral tissue and skeleton. Here, we characterize the inherent optical properties, i.e. the scattering coefficient, μ s , and the anisotropy of scattering, g , of eight intact coral species using optical coherence tomography (OCT). Specifically, we describe light scattering by coral skeletons, coenoarc tissues, polyp tentacles and areas covered by fluorescent pigments (FP). Our results reveal that light scattering between coral species ranges from μ s = 3 mm −1 ( Stylophora pistillata ) to μ s = 25 mm −1 ( Echinopora lamelosa ) . For ...

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    4. Distributed gas detection utilizing Fourier domain optical coherence based absorption spectroscopy

      Distributed gas detection utilizing Fourier domain optical coherence based absorption spectroscopy

      In this study, a new method called Fourier domain optical coherence based absorption spectroscopy (FD-OCAS) is proposed for distributed gas detection for the first time. Mach-Zehnder interferometer based quasi-distributed structure is developed for proof-concept demonstration and experimental verification. Optical interference happens between reference arm and sensing arms of the constructed Mach-Zehnder interferometer. Different sensing arms coded with different fiber lengths contribute different frequency components in ultimate interference signals. Fourier transform is used to separate each frequency to identify different sensing arms, realizing distributed detection. The amplitudes of Fourier transform are related to the gas absorption levels in corresponding sensing arms ...

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    5. In-situ monitoring and quantification of fouling development in membrane distillation by means of optical coherence tomography

      In-situ monitoring and quantification of fouling development in membrane distillation by means of optical coherence tomography

      Fouling formation in membrane distillation limits process stability and could cause besides wetting a rapid flux decrease making the process inefficient. Process performance is conventionally assessed by flux monitoring. Optical Coherence Tomography (OCT) enables in-situ visualization and quantification of fouling layers dominated by scaling in a fully operated direct contact membrane distillation system (DCMD). This study presents an innovative methodology for 3D dataset analysis allowing for the detection and quantification of predominant scaling on the membrane surface. Defined fouling parameters permit a correlation between process performance indicators, especially flux decrease and quantified fouling layer coverage. Additionally, structural information about the ...

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    6. Nondestructive Measurement of Conformal Coating Thickness on Printed Circuit Board with Ultra-high Resolution Optical Coherence Tomography

      Nondestructive Measurement of Conformal Coating Thickness on Printed Circuit Board with Ultra-high Resolution Optical Coherence Tomography

      Conformal coating (CC) is widely used to protect printed circuit board (PCB) from corrosion, mould growth and electrical failures. To ensure an effective protection, the thickness of the conformal coating layer needs to be well controlled. However, to date, the coating thickness is usually measured in a destructive way under microscopes. In this study, we proposed to use optical coherence tomography (OCT) to measure the CC thickness nondestructively. Specifically, to obtain a good accuracy in thickness measurement, we constructed a spectral domain OCT (SD-OCT) with ultra-high axial resolution to image the CC layer in three dimensions, and developed an image ...

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    7. Elucidation of microstructural changes in leaves during senescence using spectral domain optical coherence tomography

      Elucidation of microstructural changes in leaves during senescence using spectral domain optical coherence tomography

      Leaf senescence provides a unique window to explore the age-dependent programmed degradation at organ label in plants. Here, spectral domain optical coherence tomography (SD-OCT) has been used to study in vivo senescing leaf microstructural changes in the deciduous plant Acer serrulatum Hayata . Hayata leaves show autumn phenology and change color from green to yellow and finally red. SD-OCT image analysis shows distinctive features among different layers of the leaves; merging of upper epidermis and palisade layers form thicker layers in red leaves compared to green leaves. Moreover, A-scan analysis showed a significant (p < 0.001) decrease in the attenuation coefficient ...

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      Mentions: Wen-Chuan Kuo
    8. Cake formation of bidisperse suspensions in dead-end microfiltration

      Cake formation of bidisperse suspensions in dead-end microfiltration

      The evolution of the cake during dead-end microfiltration of different compositions of bidisperse feeds was investigated using network modeling and three-dimensional (3D) optical coherence tomography (OCT) imaging. The foulant particles were latex of two different sizes (namely, 3 and 5 μm) and the membrane was polycarbonate track-etched with nominal diameter of 2 μm. The results from the network model indicate that (i) the deposition of the smaller particles on the non-porous area was reduced by the presence of larger particles, whereas that of the larger particles was not affected by the concentration of the smaller ones; and (ii) monodisperse small ...

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    9. A Micro-Tomographic Insight into the Coating Systems of Historical Bowed String Instruments

      A Micro-Tomographic Insight into the Coating Systems of Historical Bowed String Instruments

      Musical instruments are tools for playing music, but for some of them—made by the most important historical violin makers—the myths hide the physical artwork. Ancient violin-making Masters developed peculiar construction methods and defined aesthetic canons that are still recognizable in their musical instruments. Recently, the focus of scientific investigations has been set on the characterization of materials and methods used by the ancient violin makers by means of several scientific approaches. In this work, the merits of synchrotron radiation micro-computed tomography and optical coherence tomography (OCT) for the investigation of complex coatings systems on historical bowed string musical ...

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    10. Adaptation Assessment of Three Bonded Resin Restorations at the Cavity Floor Using Cross-Polarization Optical Coherence Tomography

      Adaptation Assessment of Three Bonded Resin Restorations at the Cavity Floor Using Cross-Polarization Optical Coherence Tomography

      Objective: The aim of the study was to compare the composite adaptation of three systems by using cross-polarization optical coherence tomography (CP-OCT). Background data: Most polymer-based restorations suffer from polymerization shrinkage that affects the interfacial seal. This shrinkage cannot be detected by conventional X-ray methods. Optical coherence tomography was proved to be a reliable non-invasive imaging tool to examine biological structures and biomaterials at micron scale. Methods: Twenty-four cylindrical class-V cavities were prepared on the buccal surfaces of the extracted human molars. After cavity preparation, samples were randomly divided into three groups ( n  = 8) according to the restoration system: one-step ...

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      Mentions: Turki Bakhsh
    11. Optical Coherence Tomography for Fingerprint Presentation Attack Detection (Book Chapter)

      Optical Coherence Tomography for Fingerprint Presentation Attack Detection (Book Chapter)

      New research in fingerprint biometrics uses optical coherence tomography (OCT) technology to acquire fingerprints from where they originate below the surface of the skin. The penetrative nature of this technology means that rich information is available regarding the structure of the skin. This access, in turn, enables new techniques in detecting spoofing attacks, and therefore also introduces mitigation steps against current presentation attack methods. These techniques include the ability to detect fake fingers; fake layers applied above the skin; differentiate between fakes and surface skin conditions; and liveness detection based on, among others, the analysis of eccrine glands and capillary ...

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    12. Optical coherence tomography—A review of the opportunities and challenges for postharvest quality evaluation

      Optical coherence tomography—A review of the opportunities and challenges for postharvest quality evaluation

      Optical Coherence Tomography (OCT) is an established non-destructive and contactless photonic technique which has now been shown to be suitable for monitoring the near-surface internal structure of tissues in stored fruit and vegetables. Such real-time cross-sectional imaging allows for better visualisation and understanding of the temporal changes in internal structure. However, despite these advantages, problems persist around the trade-off between imaging resolution and penetration depth, image analysis and data processing, and the applicability of in situ studies outside of the laboratory setting. This review summarises previous postharvest OCT research and assesses resulting mechanistic outcomes, and future potential.

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      Mentions: K. U. Leuven
    13. Mid-infrared Fourier-domain optical coherence tomography with a pyroelectric linear array

      Mid-infrared Fourier-domain optical coherence tomography with a pyroelectric linear array

      Optical technology in the mid-infrared wavelength range is currently a rapidly developing field initiated by the availability of novel high-power and spatially coherent sources. Non-destructive testing techniques based on these sources are very promising for industrial and medical applications. However, there are still many engineering problems due to the technical challenges and high prices of the optical elements suitable for the mid-infrared region. In this paper, we report the development and performances of the first mid-infrared Fourier-domain optical coherence tomography based on a supercontinuum source and low-cost pyroelectric detector. The system is designed to operate in the spectral region around ...

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    14. Non-Contact Measurement of Small-Module Gears Using Optical Coherence Tomography

      Non-Contact Measurement of Small-Module Gears Using Optical Coherence Tomography

      Due to the small size and harsh transmission conditions of small-module gears, it is very difficult to measure gear characteristics with a modulus smaller than 1 mm. We proposed an optical coherence tomography (OCT) method for measuring small-module gears. Testing of a 30-tooth copper gear with a small modulus of 0.5 mm was carried out for the measurement of its modulus, tooth parameter, tooth number, pressure angle, modification coefficient, and tooth thickness by using OCT. In addition, the influencing factors on the measurement were discussed. The whole teeth profile of a 0.2 mm modulus gear was imaged by ...

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    15. Non-destructive identification of weld-boundary and porosity formation during laser transmission welding by using optical coherence tomography

      Non-destructive identification of weld-boundary and porosity formation during laser transmission welding by using optical coherence tomography

      Laser transmission welding offers significant benefits over conventional welding techniques enabling single-stage rapid plastic joining. The quality of laser transmission welded products are commonly assessed by measuring the weld penetration depth, hardened weld boundary, and inspecting the formation of porosity. However, existing methods of verification are inevitably accompanied by destruction of the specimen. Thus, non-destructive quality assessment methods for laser transmission welding have gained attention recently. Here, we demonstrated an extended industrial application of 860 nm wavelength based spectral domain optical coherence tomography for the non-destructive inspection of the aforementioned quality parameters of laser transmission welded industrial plastic materials, i ...

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    16. A marine biofilm flow cell for in situ screening marine fouling control coatings using optical coherence tomography

      A marine biofilm flow cell for in situ screening marine fouling control coatings using optical coherence tomography

      A novel fouling marine flow cell was designed and fitted with a clear plastic lid to allow real-time imaging of biofilms using optical coherence tomography (OCT). Marine biofilms were grown under controlled shear flow on coupons coated with 6 different biocidal antifouling coatings (SPC1, SPC2, SPC3, SPC4, CDP1 and CDP2, AkzoNobel) and one inert coating which contained no biocidal actives (NB-D) for 8 weeks. One set of coupons coated with NB was statically immersed in sea water during the same time period (NB-S). Biofilm removal was assessed by increasing the flow velocity while OCT simultaneously measured the biofilm cross-sectional area ...

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    17. Gravity-Driven Flows in Two-Fluid Drops

      Gravity-Driven Flows in Two-Fluid Drops

      The direction in which fluid circulates in binary drops doesn't change when the drops are tilted, implicating gravity—not surface tension—as the driver of flow in these systems. rops of spilled coffee dry and leave behind ring-shaped patterns. The shape and uniformity of these patterns are determined by fluid flows that drive particle deposition within the drops. Now, Fouzia Ouali of Nottingham Trent University in the UK and colleagues have shown that in the case of drops composed of two fluids, gravity, not surface tension, as researchers previously thought, dominates convective flows. The team says that this result ...

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    18. Density-Driven Flows in Evaporating Binary Liquid Droplets

      Density-Driven Flows in Evaporating Binary Liquid Droplets

      In the evaporation of microlitre liquid droplets, the accepted view is that surface tension dominates and the effect of gravity is negligible. We report, through the first use of rotating optical coherence tomography, that a change in the flow pattern and speed occurs when evaporating binary liquid droplets are tilted, conclusively showing that gravitational effects dominate the flow. We use gas chromatography to show that these flows are solutal in nature, and we establish a flow phase diagram demonstrating the conditions under which different flow mechanisms occur.

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    19. Biophotonic approach for the characterization of initial bitter-rot progression on apple specimens using optical coherence tomography assessments

      Biophotonic approach for the characterization of initial bitter-rot progression on apple specimens using optical coherence tomography assessments

      The tremendous advances achieved in the biophotonics technologies have intensified the necessity for non-invasive modalities that can characterize diverse biological materials with increased sensitivity and resolution. Optical coherence tomography (OCT) is one of the techniques that has been applied for biological applications in medicine and agriculture to identify structural properties. Herein, we report the successful incorporation of OCT for the identification of morphological changes that occur as a result of the bitter rot disease, through continuous detection of structural changes. Detailed inner morphological structural changes occurring in fruit specimens were precisely analyzed as a function of the disease incubation period ...

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    20. Investigation of Puccinia triticina contagion on wheat leaves using swept source optical coherence tomography

      Investigation of Puccinia triticina contagion on wheat leaves using swept source optical coherence tomography

      We present an investigation on applicability of swept-source optical coherence tomography (SSOCT) to examine the internal structures of plant leaves. This study helps to identify the growth and spread of the leaf rust disease in leaves of wheat plants, caused by Puccinia triticina . The epidermal cell layer and parenchyma cell layer of the acquired OCT images are correlated with the histological images to show distinctive leaf morphological boundaries. In the OCT images, the thickness of the parenchyma cell layer in healthy and infected samples are compared and analyzed. Accurate morphological and quantitative information are obtained with our developed system for ...

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      Mentions: Raju Poddar
    21. Visualization of Ink Fluidity in Inkjet Imaging Process Using Method of Optical Coherence Tomography

      Visualization of Ink Fluidity in Inkjet Imaging Process Using Method of Optical Coherence Tomography

      In order to enhance the performance of the inkjet printer, it is important to be able to appropriately control the ink fluidity in the imaging process. For examples, it is useful to know how the ink fluidity changes when inside the inkjet head or when adhering to the media. As a method that can be used for this judgment, it was attempted to use method of optical coherence tomography was attempted. It is clarified that the fluidity distribution and its time change inside the ink can be visualized by optical measurement and signal analysis. It will bring way to know ...

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    22. Determination of mechanical properties of biofilms by modeling the deformation measured using optical coherence tomography

      Determination of mechanical properties of biofilms by modeling the deformation measured using optical coherence tomography

      The advantage of using non-invasive imaging such as optical coherence tomography (OCT) to asses material properties from deformed biofilm geometries can be compromised by the assumptions made on fluid forces acting on the biofilm. This study developed a method for the determination of elastic properties of biofilms by modelling the biofilm deformation recorded by OCT imaging with poroelastic fluid-structure interaction computations. Two-dimensional biofilm geometries were extracted from OCT scans of non-deformed and deformed structures as a result of hydrodynamic loading. The biofilm geometries were implemented in a model coupling fluid dynamics with elastic solid mechanics and Darcy flow in the ...

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    23. Feature Of The Week 08/31/2018: Spectroscopic Characterization of Si/Mo Thin-film Stack at Extreme Ultraviolet Range

      Feature Of The Week 08/31/2018: Spectroscopic Characterization of Si/Mo Thin-film Stack at Extreme Ultraviolet Range

      Using extreme ultraviolet (EUV) radiation for nanoscale imaging has recently seen much interest. As actinic patterned mask inspection tools are not available, chipmakers have to rely on wafer inspection to identify mask defects. To fulfill the requirements of mask inspection, EUV sources with high brightness, high stability (spatial and temporal), and cost effectiveness are needed. In a laser-produced-plasma (LPP) generated EUV system, a high-intensity laser beam is focused onto a tin target to form a hot plasma, which emits ultraviolet light. In this study, a fiber-laser excitation source was used to generate stable 13.5-nm EUV for spectroscopic optical coherence ...

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    24. Characterisation of textured surfaces under a laminar flow by Optical Coherence Tomography (Thesis)

      Characterisation of textured surfaces under a laminar flow by Optical Coherence Tomography (Thesis)

      Textured surfaces are present everywhere in nature and in our daily life, interacting constantly with a flow. In this report, we focus on how a textured surface with pillars responds to a laminar flow inside a confined channel. The study is mainly focused on the measurements of the bending of the pillars and of the velocity field, using optical coherence tomography. The potential of this technique, which is not very common in microfluidics, is explored here to characterise our system and its limits are discussed. The measurements of the bending and of the velocity field allow to get the value ...

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    1-24 of 350 1 2 3 4 ... 13 14 15 »
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