1. Articles in category: NDE/NDT

    1-24 of 490 1 2 3 4 ... 19 20 21 »
    1. Real-Time Monitoring and Quantitative Evaluation of Resin In-Filtrant Repairing Enamel White Spot Lesions Based on Optical Coherence Tomography

      Real-Time Monitoring and Quantitative Evaluation of Resin In-Filtrant Repairing Enamel White Spot Lesions Based on Optical Coherence Tomography

      The aim of the present study was to explore the feasibility of real-time monitoring and quantitative guiding the repair of enamel white spot lesions (WSLs) with resin infiltration by optical coherence tomography (OCT). Seven New Zealand rabbits were treated with 37% phosphoric acid etchant for 15 min to establish the model of enamel demineralization chalk spots of upper incisors, which were repaired by Icon resin infiltrant. OCT, stereo microscope (SM) imaging, scanning electron microscope (SEM) imaging and hematoxylin eosin (HE) staining were used to image each operation step. The changes of WSLs of enamel before and in the process of ...

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    2. Metrological performance analysis of optical coherent tomography

      Metrological performance analysis of optical coherent tomography

      A spectral-domain optical coherence tomography (SD-OCT) system with 1555nm center wavelength is tested for stability and accuracy from the micron level to the sub-micron level. The energy centrobaric correction method is used to extract the sub-axial-resolution information as the optical path difference, i.e., the topographic height. We compared the used algorithm with the widely applied phase slope method. The stability of a point scanning OCT system in Michelson style is experimentally compared with that of a system in Fizeau style. Several simple and complicated samples are measured and compared. Finally, we compare the topographic performance of the OCT system ...

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    3. Use of optical coherence tomography (OCT) as a metrological tool measuring the volume of HepG2 tumor cell spheroids

      Use of optical coherence tomography (OCT) as a  metrological tool measuring the volume of HepG2 tumor  cell spheroids

      The advent of the use of cellular spheroids in biomedical research witnessed in recent years has continuously demonstrated the advantageous potential of their use in laboratory experiments . Added to such advances, the necessity to apply reliable methods of quality control of this type of cell culture grows simultaneously within this progress. In a scenario where centuries - old techniques to control quantitative parameters such as diameter and volume are still used, with emphasis on microscopy modalities, capable of providing images from unidirectinonal projections, optical coherence tomography (O C T) has been considered as an alternative so such methodologies. Indeed, in recent ...

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    4. Measurement of refractive index spectrum of optical material by phase detection with optical coherence tomography

      Measurement of refractive index spectrum of optical material by phase detection with optical coherence tomography

      Refractive index (RI) is a fundamental parameter of optical material, and RI spectrum (RIS) is essential for many fields. Current RI measurement is only for some discrete spectral lines, and has extremely high requirements on measurement operation and accuracy. A measurement method of continuous RIS distribution in a wide spectral range was proposed in this work. A swept-source optical coherence tomography using a Mach-Zehnder configuration was used to detect interference spectrum signal, which phase was obtained by using Hilbert transform. By detecting the sample-induced phase and using the proposed equations, RIS of a sample could be obtained. Five measurements on ...

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    5. Telephoto-lens-based Optical Differentiation Wavefront Sensor for freeform metrology

      Telephoto-lens-based Optical Differentiation Wavefront Sensor for freeform metrology

      We report an Optical Differentiation Wavefront Sensor based on a telephoto lens system and binary pixelated filters. It provides a five-fold reduction in the system length compared to a 4 f system with identical effective focal length. Measurements of phase plates with this system are compared to measurements performed with a commercial low-coherence interferometer. The telephoto-lens-based system can measure wavefronts with accuracy better than λ/ 10 Root Mean Squared (RMS) at λ =633 nm. Experimental investigation shows that the system has a high tolerance to components alignment errors.

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      Mentions: Thorlabs Lumetrics
    6. Interferometric microscope with a confocal focusing for inner surface defect detection of ICF capsule

      Interferometric microscope with a confocal focusing for inner surface defect detection of ICF capsule

      Inner surface defects of inertial confinement fusion (ICF) capsule are a key factor leading to ignition failure; however, there are still no effective and non-destructive detection methods available. To solve this problem, we propose the first interferometric microscope with confocal focusing (CFIM). CFIM first uses confocal technology to achieve accurate axial positioning of both capsule and the camera, thereby ensuring that the inner surface of the capsule is precisely and clearly imaged at the camera. Then, phase-shifting interferometry based on a short-coherence source and a spherical reference is applied to obtain inner defects result from null inner surface interferograms. In ...

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    7. Classification of Material Type from Optical Coherence Tomography Images Using Deep Learning

      Classification of Material Type from Optical Coherence Tomography Images Using Deep Learning

      Classification of material type is crucial in the recycling industry since good quality recycling depends on the successful sorting of various materials. In textiles, the most commonly used fiber material types are wool, cotton, and polyester. When recycling fabrics, it is critical to identify and sort various fiber types quickly and correctly. The standard method of determining fabric fiber material type is the burn test followed by a microscopic examination. This traditional method is destructive, tedious, and slow since it involves cutting, burning, and examining the yarn of the fabric. We demonstrate that the identification procedure can be done nondestructively ...

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    8. In-situ 3D fouling visualization of membrane distillation treating industrial textile wastewater by optical coherence tomography imaging

      In-situ 3D fouling visualization of membrane distillation treating industrial textile wastewater by optical coherence tomography imaging

      Membrane fouling, which is caused by the deposition of particles on the membrane surface or pores, reduces system performance in membrane distillation (MD) applications, resulting in increased operational costs, poor recovery, and system failure. Optical Coherence Tomography enables in-situ foulant monitoring in both 2D and 3D, however, the 2D images can only determine fouling layer thickness in severe fouling. Therefore, in this study, an advanced 3D imaging analysis technique using intensity range filters was proposed to quantify fouling layer formation during MD through the use of a single 3D image. This approach not only reduces computational power requirements, but also ...

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    9. Quantifying the refractive index of ferroelectric domain walls in periodically poled LiNbO3 single crystals by polarization-sensitive optical coherence tomography

      Quantifying the refractive index of ferroelectric domain walls in periodically poled LiNbO3 single crystals by polarization-sensitive optical coherence tomography

      Domain walls (DWs) in ferroelectric (FE) and multiferroic materials possess an ever-growing potential as integrated functional elements, for instance in optoelectronic nanodevices. Mandatory, however, is the profound knowledge of the local-scale electronic and optical properties, especially at DWs that are still incompletely characterized to date. Here, we quantify the refractive index of individual FE DWs in periodically-poled LiNbO 3 (PPLN) single crystals. When applying polarization-sensitive optical coherence tomography (PS-OCT) at 1300 nm using circular light polarization, we are able to probe the relevant electro-optical properties close to and at the DWs, including also their ordinary and extraordinary contributions. When comparing ...

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    10. In-situ observation of evolution of internal structure of alumina during sintering by swept-source OCT

      In-situ observation of evolution of internal structure of alumina during sintering by swept-source OCT

      In-situ observation of sintering of ceramics is important to understand the sintering behavior, including the development of internal structures, and to fabricate ceramics with superior properties. However, there has been no studies thus far on high-speed in-situ observation of the internal structure of green and sintered bodies at high temperatures with μm-scale resolution. Here, we applied swept-source optical coherence tomography (OCT) to observe the evolution of the internal structure in Al 2 O 3 green bodies during sintering. In-situ OCT observations revealed that internal structure changes during sintering, such as the development of density distribution and growth of coarser pores ...

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    11. Next Generation ASC Laser Controller Solution Is Now Available

      Next Generation ASC Laser Controller Solution Is Now Available

      ARGES, a product brand of Novanta Corporation (“Novanta”), announces the addition of its new laser controller, ASC Generation 4 to its ASC series portfolio. This new controller features powerful performance thanks to updated electronics, changeable multi-functional interface boards for added flexibility, and open platform with embedded Linux OS. This controller solution is compatible with all ARGES scan heads, lasers, and sub-systems. Packed with enhanced features and performance, this next generation controller works seamlessly with our proprietary software, InScript for a complete laser control solution. Our cross-collaborative team has worked tirelessly to develop a controller platform that enables a new level ...

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    12. In Situ Detection of Interfacial Flow Instabilities in Polymer Co-Extrusion Using Optical Coherence Tomography and Ultrasonic Techniques

      In Situ Detection of Interfacial Flow Instabilities in Polymer Co-Extrusion Using Optical Coherence Tomography and Ultrasonic Techniques

      Co-extrusion is a widely used processing technique for combining various polymers with different properties into a tailored multilayer product. Individual melt streams are combined in a die to form the desired shape. Under certain conditions, interfacial flow instabilities are observed; however, fundamental knowledge about their onset and about critical conditions in science and industry is scarce. Since reliable identification of interfacial co-extrusion flow instabilities is essential for successful operation, this work presents in situ measurement approaches using a novel co-extrusion demonstrator die, which is fed by two separate melt streams that form a well-controlled two-layer co-extrusion polymer melt flow. An ...

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    13. Research partnership develops 10 second high-throughput technology to detect counterfeit documents

      Research partnership develops 10 second high-throughput technology to detect counterfeit documents

      Fraudulent identity documents are an ever-evolving challenge, particularly at international border crossings. To increase their resilience to counterfeiting, many security features have been added to identification documents over the last decade. However, due to the efficiency of organised crime, the threat of individuals crossing the borders using fraudulent documents remains high. Now, a research partnership between foster+freeman and the University of Kent has developed a new, a non-destructive, high-throughput analysis technique to counter this threat. By repurposing a medical technology known as OCT (optical coherence tomography), the research group were able to rapidly distinguish the difference between legitimate and ...

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    14. In situ process monitoring and automated multi-parameter evaluation using optical coherence tomography during extrusion-based bioprinting

      In situ process monitoring and automated multi-parameter evaluation using optical coherence tomography during extrusion-based bioprinting

      In three-dimensional (3D) bioprinting, errors during the printing process leads to lower structural fidelity, and the desired structural and functional performances cannot be fully satisfied. Process monitoring with high-speed imaging techniques is helpful for identifying material deposition errors. 3D reconstruction of printed objects enables comprehensive evaluation of structural characteristics, with wide-field full-depth imaging being necessary for large objects. In this study, we demonstrate 3D extrusion-based bioprinter-associated optical coherence tomography (3D P-OCT) to achieve high-speed, wide-field and full-depth imaging, and provide in situ process monitoring and comprehensive evaluation for 3D bioprinting . In 3D P-OCT, a wide field was achieved with a ...

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    15. Optical coherence tomography-surveilled laser ablation using multifunctional catheter and 355-nm optical pulses

      Optical coherence tomography-surveilled laser ablation using multifunctional catheter and 355-nm optical pulses

      An optical coherence tomography (OCT)-monitored laser ablation system is presented in this study. The laser ablation subsystem is constructed using the third harmonic output of a Nd:YAG laser source operating at a 355-nm optical wavelength with a single pulse energy greater than 160 mJ and a 1–10 Hz tunable repetition rate. The imaging subsystem is a typical M-mode swept-source OCT system. Moreover, a type of all-fiber multifunctional integrated catheter is demonstrated. The ablation catheter consists of a fiber bundle including 41 multi-mode fibers with an outer diameter of 0.9 mm. A forward-viewing OCT imaging probe is ...

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    16. Laser beam welding of geometric figures using OCT seam tracking

      Laser beam welding of geometric figures using OCT seam tracking

      A measuring device for monitoring a laser welding process that is connectable to a machining device for machining a workpiece by a high-energy processing beam that is displaceable on the workpiece along a main machining path that corresponds to a contour of a closed geometric figure. The measuring device includes an optical coherence tomography unit having a measuring beam source for generating an optical measuring beam that is displaceable on the workpiece by at least one movable deflection unit. The optical measuring beam is displaceable on the workpiece along a first discrete measuring line, along a second discrete measuring line ...

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    17. Phase-sensitive optical coherence tomography for non-contact monitoring photocuring process

      Phase-sensitive optical coherence tomography for non-contact monitoring photocuring process

      A method combining phase-contrast technique and spectral-domain optical coherence tomography (OCT) has been recently proposed for visualizing curing behaviors inside polymers (2020 Appl. Phys. Lett. 116 054103). Here, based on the method, a non-contact and highly-sensitive optical sensor is further developed to monitor the photocuring process of light-cured polymers. Compared with the existing method, the proposed optical sensor features two distinct advantages: (a) the sensor uses a point-detection OCT, rather than a line-field OCT, to capture the interference signal, which significantly improves its practicability and the measuring speed; (b) the sensor can simultaneously monitor the shrinkage strains and refractive index ...

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    18. Optical Coherence Tomography Applied to Non-Destructive Seed Coat Thickness Measurement

      Optical Coherence Tomography Applied to Non-Destructive Seed Coat Thickness Measurement

      Background: Seed coat thickness is a parameter of interest in lentil breeding and processing. Methods described in the literature are destructive and time consuming, limiting the usefulness of this seed characteristic in breeding or grading. In this study, a low-cost optical coherence tomography (OCT) system (OQ Labscope 2.0 from Lumedica, Inc., Durham, NC USA) was used to non-destructively measure lentil seed coat thicknesses. These measurements were compared to destructive measurements obtained via optical microscopy of cross-sectioned seeds. Results: Measurements from the two methods were comparable with consistent trends in thickness and population separability among the five lentil accessions used ...

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      Mentions: Lumedica
    19. Full-field optical coherence tomography using tunable-path-difference source for three-dimensional multi-layered imaging with enhanced signal-to-noise ratio

      Full-field optical coherence tomography using tunable-path-difference source for three-dimensional multi-layered imaging with enhanced signal-to-noise ratio

      We demonstrate a novel scheme for a full-field optical coherence tomography (FF-OCT) system using a tunable-path-difference source (TPDS). Recently, the comb-spacing-swept source (CSWS) method, including TPDS, has been successfully applied to improve the stability of three-dimensional (3D) time-domain (TD)-FF-OCT imaging by eliminating the mechanical scanning of the reference path, which has been the main source of undesirable noise in general TD-OCT. However, CSWS-OCT has the drawback of a degraded signal-to-noise ratio (SNR) from a duplicated interferometer structure. In this study, we improve the configuration of the TPDS so that it can be connected directly to the measurement interferometer, including ...

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    20. Non-Destructive Subsurface Inspection of Marine and Protective Coatings Using Near- and Mid-Infrared Optical Coherence Tomography

      Non-Destructive Subsurface Inspection of Marine and Protective Coatings Using Near- and Mid-Infrared Optical Coherence Tomography

      Near- and mid-infrared optical coherence tomography (OCT) is evaluated as a non-destructive and non-contact reflection imaging modality for inspection of industrial and marine coatings. Near-infrared OCT was used to obtain high-resolution images (~6/2 µm lateral/axial) of hidden subsurface cracks and defects in a resin base coating, which had been exposed to high pressure and high temperature to study coating degradation in hostile environments. Mid-infrared OCT was employed for high-resolution (~15/8.5 µm lateral/axial) subsurface inspection of highly scattering marine coatings, demonstrating monitoring of wet film thickness and particle dispersion during curing of a 210 µm layer ...

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    21. Layered viscoelastic properties of granular biofilms

      Layered viscoelastic properties of granular biofilms

      Granular biofilms are dense spherical complex biological systems composed mainly of multi-microbial cells, water, and extracellular polymeric substances (EPS). They facilitate efficient purification and settling of activated sludge in wastewater treatment processes . The viscoelastic properties of these complex biofilm systems are important characteristics that control their growth and dictate how they respond to hydrodynamic forces and chemical stimuli. However, the viscoelastic properties of granular biofilms are poorly understood. In this paper, we study granular biofilms' viscoelastic properties using optical coherence elastography (OCE), a nondestructive method that integrates optical coherence tomography (OCT) with elastic wave propagation . While quantitative viscoelastic characterization of ...

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    22. The Effect of Thermocycling on Interfacial Bonding Stability of Self-Etch Adhesives: OCT Study

      The Effect of Thermocycling on Interfacial Bonding Stability of Self-Etch Adhesives: OCT Study

      Objective: The aim of this study was to monitor the behavior of interfacial gaps formed under different bonded polymeric restorations before and after thermocycling (TC), using swept-source optical coherence tomography (SS-OCT) and confirming the obtained findings with confocal laser scanning microscopy (CLSM). Materials and methods: Cylindrical class I cavities were prepared in twenty noncarious human premolar teeth (1.5 mm depth × 3.5 mm diameter) and divided randomly into two groups: TS and SN, according to the adhesive system ( n = 10). In the TS group, one-step self-etch adhesive Clearfil Tri-S Bond Plus (Kuraray Noritake Dental, Japan) was used, followed by ...

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    23. Microstructural changes in rice (Oryza sativa L.) leaves under varying low pH levels: a swept-source optical coherence tomography approach

      Microstructural changes in rice (Oryza sativa L.) leaves under varying low pH levels: a swept-source optical coherence tomography approach

      Soil acidification has shown detrimental effects on rice plants that lead to decreased rice production. In the present study, we aim to study the microstructural changes in rice leaves under acidic stress through swept-source optical coherence tomography (SS-OCT). To achieve this, rice seeds were germinated, subsequently these germinated seedlings were further grown under varying pH conditions for 14 d. Growth in root and shoot of plants and chlorophyll content of leaf samples were studied at varying pH levels. Similarly, acidic stress treated rice leaves were also subjected to SS-OCT image analysis revealing several features present in the layers of leaves ...

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    24. Biometric Identification with 3D Fingerprints Acquired Through Optical Coherence Tomography

      Biometric Identification with 3D Fingerprints Acquired Through Optical Coherence Tomography

      —A method to obtain epidermal and dermal 3D fingerprints from high-resolution images acquired using Optical Coherence Tomography (OCT) is proposed. This method addresses limitations of current 3D reconstruction techniques such as depth and resolution variations, sensitivity to low illumination and poor contrast. The availability of these fingerprints made possible the creation of new identification techniques that benefit from the rich information available in 3D. We propose a 3D fingerprint matching process based on KH maps, which are 2D representations of curvature types extracted by computing the Gaussian and mean curvatures from a region of interest around minutiae.The matching strategy ...

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