1. Articles in category: NDE/NDT

    1-24 of 397 1 2 3 4 ... 15 16 17 »
    1. Dual-side view optical coherence tomography for thickness measurement on opaque materials

      Dual-side view optical coherence tomography for thickness measurement on opaque materials

      Optical coherence tomography (OCT), as an optical interferometric imaging technique, has found wide applications in various fields. In principle, OCT is well suited for imaging layered structures, and thus, one of the typical applications is thickness measurement. However, due to the limited imaging depth resulting from light attenuation, thickness measurement by OCT is limited to non-opaque materials. In this study, we developed a novel (to the best of our knowledge) dual-side view OCT (DSV-OCT) system for thickness measurement on opaque materials. The dual-side view was achieved on a conventional swept source OCT platform by creating two symmetrical sampling arms. This ...

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    2. Quasi-tomography by free space line field spectral domain optical coherence reflectometry

      Quasi-tomography by free space line field spectral domain optical coherence reflectometry

      This paper reports the development of a new technique, free space line field spectral domain optical coherence reflectometry (LF-SD-OCR), which is able to produce tomographic like (quasi) images. Furthermore, the capabilities and cost benefits of the technique are demonstrated by constructing a handheld LF-SD-OCR device. For glossy paint systems and other suitable samples, the line field format produces quasi-tomographic (cross-sectional) imaging through the layers, with axial and lateral image resolutions of 1.3 µm and 40 µm respectively. From these, the clear coat thicknesses on the bonnet of cars were measured by graph search segmentation and maximum A-scan projection. In ...

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      Mentions: Yalin Zheng
    3. Evaluation of anti-bacterial adhesion performance of polydopamine cross-linked graphene oxide RO membrane via in situ optical coherence tomography

      Evaluation of anti-bacterial adhesion performance of polydopamine cross-linked graphene oxide RO membrane via in situ optical coherence tomography

      Biofouling is a critical issue which accounts for >45% of all fouling in reverse osmosis (RO). Because fouling occurs on the surface of the membrane, surface modification has been considered an effective measure for fouling mitigation and for achieving sustainable membrane performance. Herein, we modified a RO membrane using graphene oxide (GO) crosslinked with a thin layer of polydopamine (PDA-GO) to obtain a bactericidal and antibiofouling surface. Optical coherence tomography (OCT) was used as a non-destructive, real-time, in situ monitoring tool to observe the fouling dynamics and to understand material-foulant interaction. In situ three-dimensional (3D) monitoring results showed that the ...

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    4. Compact and Mobile Full-Field Optical Coherence Tomography Sensor for Subsurface Fingerprint Imaging

      Compact and Mobile Full-Field Optical Coherence Tomography Sensor for Subsurface Fingerprint Imaging

      Conventional fingerprint sensors that are deployed in real-life applications lack the ability to peer inside a finger beyond the external surface. Subsurface information can provide complimentary biometric characteristics associated with the finger. The subsurface fingerprints can also be employed when the quality of the external/surface fingerprints is affected. One of the most promising technologies for imaging below the surface of an external fingerprint is full-field optical coherent tomography (FF-OCT). However, the FF-OCT can be expensive and cumbersome, despite its proven ability for biometric use. In this paper, we describe the design and implementation of a compact, mobile and cost-effective ...

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    5. Dimensional characterization of large opaque samples and microdeformations by low coherence interferometry

      Dimensional characterization of large opaque samples and microdeformations by low coherence interferometry

      We report on the application of an interferometric system based on the low-coherence interferometry technique to the dimensional characterization of large opaque mechanical parts as well as microdeformations experienced by them. The implemented scheme is capable of simultaneously measuring very small deformations and relatively large dimensions or thicknesses (several centimeters) of the sample. By applying the chirp Fourier transform algorithm, it was possible to measure changes in thickness with an uncertainty of 0.35  μm when a 7-cm-thick sample was measured. The measurement scheme was implemented in optical fiber, which makes it highly adaptable to industrial conditions. It employs a ...

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    6. Optical coherence elastography by ambient pressure modulation for high-resolution strain mapping applied to patterned cross-linking

      Optical coherence elastography by ambient pressure modulation for high-resolution strain mapping applied to patterned cross-linking

      The purpose of this study was to develop a novel non-contact optical coherence elastography (OCE) approach to measure laterally and axially highly resolved corneal strain distribution at different stages of patterned corneal cross-linking (CXL). Freshly enucleated rat eyes were obtained and prepared for accelerated patterned CXL treatment with distinct ultraviolet (UV) patterns (central, peripheral, bow-tie irradiation). Each cornea was measured repeatedly, in three different conditions: (i) virgin, (ii) after epithelial debridement and 0.5% hypo-osmolar riboflavin instillation for 30 min, and (iii) after patterned CXL at 9 mW cm −2 for 10 min. For biomechanical assessment, the corneal deformation response ...

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    7. Comparative study of the influence of linear and branched alkyltrichlorosilanes on the removal efficiency of polyethylene and polypropylene-based microplastic particles from water

      Comparative study of the influence of linear and branched alkyltrichlorosilanes on the removal efficiency of polyethylene and polypropylene-based microplastic particles from water

      Microplastics are a global environmental pollution. Due to this fact, new solutions are needed to reduce the amount in various aquatic environments. A new concept introduced by Herbort and Schuhen from the year 2016 describes the agglomeration of microplastics in water using silicon-based precursors. In the study presented here, alkyltrichlorosilanes with different linear and branched alkyl groups and a chain length between 1 and 18 carbon (C-) atoms are investigated for their suitability to fix microplastics (mixtures of polyethylene (PE) and polypropylene (PP)) and to form larger agglomerates. As the alkyl group has a major influence on the reaction rate ...

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    8. Mechanical test study in composites using digital holographic interferometry and optical coherence tomography simultaneously

      Mechanical test study in composites using digital holographic interferometry and optical coherence tomography simultaneously

      A dual optical configuration to inspect the internal and external mechanical response of a composite specimen is presented. The inspection simultaneously uses two equally aligned optical techniques, digital holographic interferometry and Fourier domain optical coherence tomography, to retrieve surface and internal data, respectively. The sample under study is a composite specimen of poly-methyl-methacrylate reinforced with metallic particles. Two different sets of samples are analyzed to compare their mechanical behavior. A homemade, fully controlled testing machine is used to apply a controlled compression load while each technique registers an image. In this form, the surface and internal optical phase measurements are ...

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    9. Frequency-domain optical coherence tomography system in the terahertz region

      Frequency-domain optical coherence tomography system in the terahertz region

      In this study, a frequency-domain optical coherence tomography (FD-OCT) system in the terahertz frequency range was developed. To generate tunable continuous-wave terahertz radiation, the outputs of two near-infrared external cavity diode lasers were mixed in an antenna-coupled photo-mixer. Using the FD-OCT system, tomographic profiling of the front and back surfaces of a high-resistivity silicon plate was realized.

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      Mentions: Osaka University
    10. Identification of Fungus-infected Tomato Seeds Based on Full-Field Optical Coherence Tomography

      Identification of Fungus-infected Tomato Seeds Based on Full-Field Optical Coherence Tomography

      The morphological changes of anthracnose (fungus) -infected tomato seeds have been studied to identify the infection and characterize its effect. Full-field optical coherence tomography (FF-OCT) has been utilized as a nondestructive but efficient modality for visualizing the effects of fungal infection. The cross-sectional images extracted from a stack of en face FF-OCT images showed significant changes with infection in the seed structure. First of all, the seed coat disappeared with the infection. The thickness of the seed coat of a healthy seed was measured as 28.2 µm, with a standard deviation of 1.2 µm. However, for infected seeds ...

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    11. Characterization of biofouling with 3D-printed spacers using 3D optical coherence tomography (Thesis)

      Characterization of biofouling with 3D-printed spacers using 3D optical coherence tomography (Thesis)

      Biofouling in membrane filtration is a common occurrence which impedes the efficiency of the separation process. By looking into the biofouling mechanisms via the observation of a filtration process, potential problems can be addressed and resolved. This study uses optical coherence tomography (OCT) to investigate the effects of using different 3D-printed spacers on the biofouling process. A compilation of OCT scans of a representative unit cell of each spacer was taken as a function of time to generate 3D-images showing the morphology of a foulant layer. Through the usage of various quantitative analysing methods (such as EIS, DOTM and etc ...

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    12. Investigation of sputtering target re-deposits by Optical Coherence Tomography and Grazing Incident X-ray Diffraction

      Investigation of sputtering target re-deposits by Optical Coherence Tomography and Grazing Incident X-ray Diffraction

      The sputtering target re-deposit grown by cumulative sputtering has been investigated in this work by studying both fresh and rigorously sputtered zirconium oxide target by Fourier Domain Optical Coherence Tomography (FDOCT), a depth resolved optical imaging modality. The Optical Coherence Tomography (OCT) depth profiles have further been analyzed to extract optical attenuation coefficient of sputtered target surface as well as fresh target surface. Re-deposited sputtered target surface shows larger optical attenuation coefficient in the range of 1.5-4.4 mm −1 as opposed to that of 1.1 mm −1 for fresh ZrO 2 target. The same sputtered target surfaces ...

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      Mentions: K. Divakar Rao
    13. Non-contact characterization of compound optical elements using reflectance confocal microscopy, low-coherence interferometry, and computational ray-tracing

      Non-contact characterization of compound optical elements using reflectance confocal microscopy, low-coherence interferometry, and computational ray-tracing

      Advances in microscopy have enabled us to see at unprecedented depths and resolutions, even breaking the diffraction-limit by several fold. These improvements have come at the expense of system complexity with microscopes routinely employing multiple objective lenses and custom optical relays. Optimal system design is paramount for imaging performance, but research systems are limited by the use of commercial components because optical prescriptions are often inaccessible. System performance can be further degraded when these components are implemented in nonstandard configurations outside of manufacturer specifications. Here, we describe a method for characterization of compound optical elements including curvatures, material and air-gap ...

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      Mentions: Yuankai K. Tao
    14. Investigation of cell dynamics in 3D cell spheroids and cell interaction with 3D printed scaffolds by mOCT

      Investigation of cell dynamics in 3D cell spheroids and cell interaction with 3D printed scaffolds by mOCT

      Optical coherence tomography is a non-invasive and label-free imaging modality based on the detection of backscattered light in samples. As microscopic OCT (mOCT) combines high axial and lateral resolution, an investigation of biological and printed samples at subcellular level is feasible. The additional excellent depth resolution enables mOCT to be a suitable quality control of 3D printed samples. The use of speckle variance adds information about cell viability. Here we present the feasibility of investigating cell viability within a cell spheroid and monitoring the cell interaction with bioprinted scaffolds using mOCT.

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    15. At-line Validation of Optical Coherence Tomography as In-line/At-line Coating Thickness Measurement Method

      At-line Validation of Optical Coherence Tomography as In-line/At-line Coating Thickness Measurement Method

      Optical Coherence Tomography (OCT) is a promising technology for monitoring of pharmaceutical coating processes. However, the pharmaceutical development and manufacturing require a periodic validation of the sensor’s accuracy. For this purpose, we propose polyethylene terephthalate (PET) films as a model system, which can be periodically measured during manufacturing coating monitoring via OCT. This study proposes a new approach addressing the method validation requirement in the pharmaceutical industry and presents results for complementary methods. The methods investigated include direct measurement of the layer thickness using a micrometer gauge as reference, X-ray micro computed tomography, transmission and reflectance terahertz pulsed imaging ...

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    16. Method to characterize cut gemstones using optical coherence tomography

      Method to characterize cut gemstones using optical coherence tomography

      The invention includes an improvement in a method of assessing a gemstone having at least one planar face with an internally reflecting surface including the steps of optically modifying the at least one planar face of the gemstone to return a sample beam from an internally reflecting plane corresponding to the at least one planar face to an optical coherence tomography (OCT) system; selectively directing the sample beam from an optical coherence tomography (OCT) system onto the gemstone; and generating an OCT image map of the gemstone to determine volume, gem carat weight and/or quality.

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    17. Assessing internal fouling during microfiltration optical coherence tomography and evapoporometry

      Assessing internal fouling during microfiltration optical coherence tomography and evapoporometry

      The internal fouling of membranes is typically presumed and inferred, but the direct characterization of representative samples is challenging. This study targeted to assess internal fouling using the Optical Coherence Tomography (OCT) and Evapoporometry (EP) techniques for real-time monitoring during filtration and off-line measurement of the pore size distributions (PSDs) of the fouled membranes, respectively. The results were validated by atomic force microscopy (AFM) measurements and also the three-mechanism fouling model. The foulant used was the well-studied bovine serum albumin (BSA), while the membranes were three commercially available polymeric microfiltration membranes with similar nominal pore sizes and porosities. Although the ...

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    18. 3D Fingerprint Gender Classification Using Deep Learning

      3D Fingerprint Gender Classification Using Deep Learning

      Optical Coherence Tomography (OCT) is a high resolution imaging technology, which provides a 3D representation of the fingertip skin. This paper for the first time investigates gender classification using those 3D fingerprints. Different with current fingerprint gender classification methods, the raw multiple longitudinal( X - Z ) fingertip images of one finger can be applied instead of studying features extracted from fingerprints, and the model can be trained effectively when the training data set is relatively small. Experimental results show that the best accuracy of 80.7% is achieved by classifying left fore finger on a small database with 59 persons. Meanwhile ...

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    19. Measuring light scattering and absorption in corals with Inverse Spectroscopic Optical Coherence Tomography (ISOCT): a new tool for non-invasive monitoring

      Measuring light scattering and absorption in corals with Inverse Spectroscopic Optical Coherence Tomography (ISOCT): a new tool for non-invasive monitoring

      The success of reef-building corals for >200 million years has been dependent on the mutualistic interaction between the coral host and its photosynthetic endosymbiont dinoflagellates (family Symbiodiniaceae) that supply the coral host with nutrients and energy for growth and calcification. While multiple light scattering in coral tissue and skeleton significantly enhance the light microenvironment for Symbiodiniaceae, the mechanisms of light propagation in tissue and skeleton remain largely unknown due to a lack of technologies to measure the intrinsic optical properties of both compartments in live corals. Here we introduce ISOCT (inverse spectroscopic optical coherence tomography), a non-invasive approach to measure ...

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    20. New imaging platform examines mechanisms behind coral bleaching

      New imaging platform examines mechanisms behind coral bleaching

      As coral reefs deteriorate in the face of climate change, an interdisciplinary Northwestern Engineering research team has developed an innovative method to image coral nanoscale structures and quantify pigment absorption in live corals, an indicator of coral health. The imaging platform could become a valuable tool to help marine biologists better understand coral physiology as well measure and monitor coral health. Reef building corals provide a home to more than 1 million species in our oceans. Yet increasing ocean temperatures have given rise to coral bleaching, a phenomenon where corals expel their life-providing algae, jeopardizing the health and sustainability of ...

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    21. Electromagnetic analysis for optical coherence tomography based through silicon vias metrology

      Electromagnetic analysis for optical coherence tomography based through silicon vias metrology

      This paper reports on progress in the analysis of time-domain optical coherence tomography (OCT) applied to the dimensional metrology of through-silicon vias (TSVs), which are vertical interconnect accesses in silicon, enabling three-dimensional (3D) integration in microelectronics, and estimates the deviations from earlier, simpler models. The considered TSV structures are 1D trenches and circular holes etched into silicon with a large aspect ratio. As a prerequisite for a realistic modeling, we work with spectra obtained from reference interferograms measured at a planar substrate, which fully includes the dispersion of the OCT apparatus. Applying a rigorous modal approach, we estimate the differences ...

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    22. Measurement of granule layer thickness in a spouted bed coating process via optical coherence tomography

      Measurement of granule layer thickness in a spouted bed coating process via optical coherence tomography

      In this work a recently developed in-line measurement technique for monitoring of coating thickness was applied to a spray-coating process in a three-dimensional prismatic spouted bed. The layer thickness was quantified with an optical coherence tomography (OCT) sensor positioned in front of the observation window of the process chamber. The time-dependent layer thickness was measured directly and in real-time from the OCT images, with no chemometric calibration being needed. To validate the obtained data, additional off-line OCT measurements were performed with optical particle size measurements and micro–computed tomography (micro-CT). The off-line measurements were conducted with representative samples extracted at ...

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    23. Optical properties of human milk

      Optical properties of human milk

      With human milk being the most important source of infant nutrition, the protection and support of breastfeeding are essential from a global health perspective. Nevertheless, relatively few objective methods are available to investigate human milk composition and lactation physiology when a mother experiences breastfeeding problems. We argue that optics and photonics offer promising opportunities for this purpose. Any research activity within this new application field starts with a thorough understanding on how light interacts with human milk. Therefore, the aim of this study was to investigate the full set of optical properties for human milk and the biological variability therein ...

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    24. Optical coherence tomography in forensic sciences: a review of the literature

      Optical coherence tomography in forensic sciences: a review of the literature

      Optical coherence tomography (OCT) is an interferometric imaging technique that has revolutionized clinical ophthalmology since the first half of the 1990’s. Despite this approach being successfully employed in ophthalmology and having great potential in forensic cases, its use in different forensic fields appears to be quite limited. In this review we reviewed the scientific literature regarding the application of OCT in forensic science and legal medicine from 1995 to 2019. Our research showed the usefulness of this approach for the study of coronary injuries, postmortem ocular changes, forensic entomology, and several other applications of specific forensic interest (the study ...

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    1-24 of 397 1 2 3 4 ... 15 16 17 »
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