1. Articles in category: NDE/NDT

    1-24 of 416 1 2 3 4 ... 16 17 18 »
    1. Ultrafast-laser ablation of polymer multicore fibers enhances biomedical sensing

      Ultrafast-laser ablation of polymer multicore fibers enhances biomedical sensing

      The next step is to integrate the multipoint-emission fiber, with optimization, in devices to perform a range of biomedical applications such as fluorescence, 2 confocal imaging, 3 photobiomodulation, 4 optical tomography, 5 medical device location, 6 and 3D optical coherence tomography (OCT). 7 The discrete emission of light has potential in medical diagnostics, enabling spectroscopic investigation at many points along a medical device throughout an organ or extended tissue structures. During medical-device placement—for instance, central venous catheter placement—multipoint light emission along the device length could be viewed through the skin. An immediate application of such a fiber is ...

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    2. A Method for the Assessment of Textile Pilling Tendency Using Optical Coherence Tomography

      A Method for the Assessment of Textile Pilling Tendency Using Optical Coherence Tomography

      Pilling is caused by friction pulling and fuzzing the fibers of a material. Pilling is normally evaluated by visually counting the pills on a flat fabric surface. Here, we propose an objective method of pilling assessment, based on the textural characteristics of the fabric shown in optical coherence tomography (OCT) images. The pilling layer is first identified above the fabric surface. The percentage of protruding fiber pixels and Haralick’s textural features are then used as pilling descriptors. Principal component analysis (PCA) is employed to select strongly correlated features and then reduce the feature space dimensionality. The first principal component ...

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    3. Optical coherence tomography with balanced signal strength across the depth for pearl inspection

      Optical coherence tomography with balanced signal strength across the depth for pearl inspection

      Optical coherence tomography (OCT) relies on the reflection of light from structures in different layers to interferometrically reconstruct the volumetric image of the sample. However, light returned from multiple layers suffers from imbalanced attenuation owing to the optical path difference and inhomogeneous tissue absorption. We report an optimization algorithm to improve signal strength in deep tissue for swept-source (SS)-OCT imaging. This algorithm utilizes the attenuation coefficient of consecutive layers within the sample and combines them to compensate for the signal intensity loss from deep tissue. We stacked 170-µm thick cover slides as a standard sample for benchmark testing ...

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    4. Keyhole mapping to enable closed-loop weld penetration depth control for remote laser welding of aluminum components using optical coherence tomography

      Keyhole mapping to enable closed-loop weld penetration depth control for remote laser welding of aluminum components using optical coherence tomography

      Remote laser welding (RLW) combines the positive features of tactile laser welding with additional benefits such as increased processing speed, reduced operational cost and service, and higher process flexibility. A leading challenge preventing the full uptake of RLW technology in industry is the lack of efficient closed loop in-process (CLIP) monitoring and weld quality control solutions. This underpins the need to fuse multiple sensor technologies and data analytics with predictive engineering simulations. Although the development and integration of a variety of sensors covers the radiation spectrum from ultraviolet to far-infrared, the flawless deployment of CLIP solutions is still challenged by ...

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    5. Optical Coherence Tomography and Its Non-medical Applications (Textbook)

      Optical Coherence Tomography and Its Non-medical Applications (Textbook)

      Optical coherence tomography (OCT) is a promising non-invasive non-contact 3D imaging technique that can be used to evaluate and inspect material surfaces, multilayer polymer films, fiber coils, and coatings. OCT can be used for the examination of cultural heritage objects and 3D imaging of microstructures. With subsurface 3D fingerprint imaging capability, OCT could be a valuable tool for enhanci...

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    6. Complementary Use of Active Infrared Thermography and Optical Coherent Tomography in Non-destructive Testing Inspection of Ancient Marquetries

      Complementary Use of Active Infrared Thermography and Optical Coherent Tomography in Non-destructive Testing Inspection of Ancient Marquetries

      Imaging-based inspection techniques have practical advantages in the study and/or rehabilitation of artworks. They provide in some cases internal information on the status of the sample to be inspected. On the one hand, techniques based on active infrared thermography (IRT) are advantageous to obtaining complete images of the inspected parts, although a technical interpretation performed by a team of experts in non-destructive testing (NDT) techniques is needed above all when the target is composed, as in our case, by different materials. On the other hand, optical coherence tomography (OCT) is slow when inspecting complete parts, but it has great ...

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    7. Extended sub-surface imaging in industrial OCT using ‘non-diffracting’ Bessel beams

      Extended sub-surface imaging in industrial OCT using ‘non-diffracting’ Bessel beams

      Optical coherence tomography (OCT) is an imaging technique which can provide sub-surface evaluation of defects in optically compliant components such as those manufactured by polymeric selective laser sintering. In OCT systems, achieving lateral imaging resolutions of <10 µm means that full-depth imaging requires multiple scans due to the limited depth of focus (DOF). We present a study on the application of ‘non-diffracting’ Bessel beams to extend system DOF and enable deeper imaging with a single scan. Such capability expands the potential for OCT as a rapid tool for sub-surface assessment, either in-line or in-process, by greatly reducing acquisition times.

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    8. Improvement of the depth resolution of swept-source THz-OCT for non-destructive inspection

      Improvement of the depth resolution of swept-source THz-OCT for non-destructive inspection

      We construct a terahertz swept source optical coherence tomography system using a continuous-wave diode multiplier source in the 600-GHz band for defect inspection in multilayer objects and evaluate its performance. Using this system, we image a multilayer plastic sample to demonstrate the effectiveness of nondestructive three-dimensional imaging. To enhance the depth resolution, we apply an annihilating filter to the analysis and confirm that two surfaces of a 1-mm-thick plastic plate can be resolved. In addition, the repeatability of measured thicknesses is 0.22 mm. These values are approximately one-half and one-tenth of the resolution achievable by conventional Fourier analysis, respectively.

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    9. Robust and high-security fingerprint recognition system using optical coherence tomography

      Robust and high-security fingerprint recognition system using optical coherence tomography

      Traditional fingerprint recognition systems are vulnerable to attacks, such as the use of artificial fingerprints, and poor performance will be achieved if the captured surface fingerprints are of low-quality. Developing high-security and robust fingerprint recognition systems is of increasing concern in modern society. The introduction of optical coherence tomography (OCT) for fingerprint imaging opens up a new research domain for fingerprint recognition due to its ability to capture the depth information of skin layers. This paper proposes a fingerprint recognition system based on OCT. The research first establishes a database with normal, worn-out, artificial and degraded fingerprints imaged by our ...

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    10. 3D-printed corals could improve bioenergy and help coral reefs

      3D-printed corals could improve bioenergy and help coral reefs

      Researchers from Cambridge University and University of California San Diego have 3D printed coral-inspired structures that are capable of growing dense populations of microscopic algae. Their results, reported in the journal Nature Communications , open the door to new bio-inspired materials and their applications for coral conservation. In the ocean, corals and algae have an intricate symbiotic relationship. The coral provides a host for the algae, while the algae produce sugars to the coral through photosynthesis. This relationship is responsible for one of the most diverse and productive ecosystems on Earth, the coral reef. "Corals are highly efficient at collecting and ...

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    11. An open-source robotic platform that enables automated monitoring of replicate biofilm cultivations using optical coherence tomography

      An open-source robotic platform that enables automated monitoring of replicate biofilm cultivations using optical coherence tomography

      The paper introduces a fully automated cultivation and monitoring tool to study biofilm development in replicate experiments operated in parallel. To gain a fundamental understanding of the relation between cultivation conditions and biofilm characteristics (e.g., structural, mechanical) a monitoring setup allowing for the standardization of methods is required. Optical coherence tomography (OCT) is an imaging modality ideal for biofilms since it allows for the monitoring of structure in real time. By integrating an OCT device into the open-source robotic platform EvoBot, a fully automated monitoring platform for investigating biofilm development in several flow cells at once was realized. Different ...

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    12. Position sensing of ultrashort pulsed laser-welded seams in glass by optical coherence tomography

      Position sensing of ultrashort pulsed laser-welded seams in glass by optical coherence tomography

      Today's methods for the inspection of the position of weld seams in glass, which has a decisive effect on the strength and thus on the quality of the permanent bond, are costly and often carried out manually in a destructive manner. The present paper proposes the application of optical coherence tomography to determine the position of the weld seam by evaluation of the signals caused by the voids within weld seams. Blind welds of fused silica and alkali-aluminosilicate glass were investigated, and a method for data evaluation is presented. The method is predominantly suitable for glass that exhibits the ...

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    13. Dual-band infrared optical coherence tomography using a single supercontinuum source

      Dual-band infrared optical coherence tomography using a single supercontinuum source

      Recent developments and commercial availability of low-noise and bright infrared (IR) supercontinuum sources initiated intensive applied research in the last few years. Covering a significant part of near- and mid-infrared spectral ranges, supercontinuum radiation opened up unique possibilities and alternatives for the well-established imaging technique of optical coherence tomography (OCT). In this contribution, we demonstrate the development, performance, and maturity of a cost-efficient dual-band Fourier-domain IR OCT system (2 µm and 4 µm central wavelengths). The proposed OCT setup is elegantly employing a single supercontinuum source and a pyroelectric linear array. We discuss adapted application-oriented approaches to signal acquisition and ...

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    14. Monitoring and quantification of bioelectrochemical Kyrpidia spormannii biofilm development in a novel flow cell setup

      Monitoring and quantification of bioelectrochemical Kyrpidia spormannii biofilm development in a novel flow cell setup

      Spatially resolved data for biofilm structure can often not be assessed easily in bioelectrochemical setups due to the orientation and placement of anode and cathode. However, understanding the interplay of biofilm (structure) development and electrochemical parameters is crucial for optimizing bioelectrochemical biofilm systems. For example, to produce value added products. This study thus, presents a versatile flow cell setup allowing for control of hydrodynamic, substrate (liquid and gaseous), and nutritional conditions as well as physical parameters. Here, a versatile lab-scale flow cell system equipped with a cathode and an anode is presented to monitor the growth of Kyrpidia spormannii biofilm ...

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    15. Method for optically measuring the weld penetration depth

      Method for optically measuring the weld penetration depth

      Embodiments pertain measuring the weld penetration depth, particularly in welding, drilling or machining processes carried out by means of a working laser beam, wherein a measurement light beam of a sensor system is coupled into a processing beam path of the working laser beam in a laser machining head and bundled or focused into a measurement light spot on the surface of a workpiece by means of focusing optics of the processing beam path. The measurement light beam reflected on the surface of the workpiece is then returned to a measurement and evaluation unit of the sensor system in order ...

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    16. Optical coherence tomography imaging of plant root growth in soil

      Optical coherence tomography imaging of plant root growth in soil

      Complex interactions between roots and soil provide the nutrients and physical support required for robust plant growth. Yet, visualizing the root–soil interface is challenged by soil’s opaque scattering characteristics. Herein, we describe methods for using optical coherence tomography (OCT) to provide non-destructive 3D and cross-sectional root imaging not available with traditional bright-field microscopy. OCT is regularly used for bioimaging, especially in ophthalmology, where it can detect retinal abnormalities. Prior use of OCT in plant biology has focused on surface defects of above-ground tissues, predominantly in food crops. Our results show OCT is also viable for detailed, in situ ...

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    17. Membrane fouling by clay suspensions during NF-like forward osmosis: Characterization via optical coherence tomography

      Membrane fouling by clay suspensions during NF-like forward osmosis: Characterization via optical coherence tomography

      The use of a membrane with a relatively loose ‘active layer’ opened a new paradigm for the application of osmotically driven processes. An effective way of imparting the osmotic pressure difference across the ‘active layer’ is to employ divalent salts as the draw solute, whose negative effects on the organic fouling have been documented in the literature. This study was targeted on investigating the fouling by clay suspensions when performing the forward osmosis (FO) with a nanofiltration (NF)-like membrane. Optical coherence tomography (OCT) was exploited to analyze the fouling phenomena in a way of determining the critical point of ...

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    18. Three-dimensional detection and quantification of defects in SiC by optical coherence tomography

      Three-dimensional detection and quantification of defects in SiC by optical coherence tomography

      Silicon carbide (SiC) is widely used in high power electronic devices. However, defects on the SiC significantly reduce the yield and decrease the performance of SiC. Accurate detection of the defects is essential in the process control. We demonstrated a noninvasive three-dimensional (3D) defect detection method for SiC using optical coherence tomography (OCT). Defects including the triangular defects, hexagonal voids, grain boundaries, and carrot defects were inspected and analyzed on SiC wafers. The 3D images of defects acquired with OCT provided detailed information on the 3D structures and dimensions of defects, and the locations and orientations of the defects inside ...

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      Mentions: Pei Ma
    19. 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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    20. 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
    21. 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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    22. 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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    23. 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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    1-24 of 416 1 2 3 4 ... 16 17 18 »
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