1. Articles in category: NDE/NDT

    1-24 of 215 1 2 3 4 5 6 7 8 9 »
    1. 3D optical phase reconstruction within PMMA samples using a spectral OCT system

      3D optical phase reconstruction within PMMA samples using a spectral OCT system

      The optical coherence tomography (OCT) technique has proved to be a useful method in biomedical areas such as ophthalmology, dentistry, dermatology, among many others. In all these applications the main target is to reconstruct the internal structure of the samples from which the physician’s expertise may recognize and diagnose the existence of a disease. Nowadays OCT has been applied one step further and is used to study the mechanics of some particular type of materials, where the resulting information involves more than just their internal structure and the measurement of parameters such as displacements, stress and strain. Here we ...

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    2. Observation of drying process of multilayered paint using fOCT based on dynamic speckles

      Observation of drying process of multilayered paint using fOCT based on dynamic speckles

      Recently, a demand for the precise observation of a multilayered paint system have been increasing such as in car industry. However, conventional methods can observe only the surface condition of the paint. In this study, we propose a new method to observe a three dimensional drying process of the multilayered paint using functional Optical Coherence Tomography (fOCT). In this method, the dynamic speckles that appear in OCT signal were utilized. The temporal properties of the dynamic speckle is related to the Brownian motion of the scattering particles in the paint, and thus depends on the drying condition. Autocorrelation function of ...

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    3. Optical identification based on time domain optical coherence tomography

      Optical identification based on time domain optical coherence tomography

      We present a novel method for optical identification, i.e., authenticating valuable documents such as a passport, credit cards, and bank notes, using optical coherence tomography (OCT). An OCT system can capture three-dimensional (3D) images and visualize the internal structure of an object. In our work, as an object, we consider a multilayered optical identification tag composed of a limited number of thin layers (10–100 μm thick). The thickness, width, and location of the layers in the tag encode a unique identification information. Reading of the tag is done using a time domain OCT (TD-OCT) system. Typically, a TD-OCT ...

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    4. Optical coherence tomography complemented by hyperspectral imaging for the study of protective wood coatings

      Optical coherence tomography complemented by hyperspectral imaging for the study of protective wood coatings

      Optical coherence tomography (OCT) is a contactless and non-destructive testing (NDT) technique based on low-coherence interferometry. It has recently become a popular NDT-tool for evaluating cultural heritage. In this study, protective coatings on wood and their penetration into the wood structure were measured with a customized infrared fiber optic OCT instrument. In order to enhance the understanding of the OCT measurements of coatings on real wooden samples, an optimization of the measuring and analyzing methodology was performed by developing an averaging approach and by post-processing the data. The collected information was complemented by data obtained with hyperspectral imaging to allow ...

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    5. Quantifying pharmaceutical film coating with optical coherence tomography and terahertz pulsed imaging: an evaluation

      Quantifying pharmaceutical film coating with optical coherence tomography and terahertz pulsed imaging: an evaluation

      Spectral domain optical coherence tomography (SD-OCT) has recently attracted a lot of interest in the pharmaceutical industry as a fast and non-destructive modality for quantification of thin film coatings that cannot easily be resolved with other techniques. Due to the relative infancy of this technique, much of the research to date has focused on developing the in-line measurement technique for assessing film coating thickness. To better assess OCT for pharmaceutical coating quantification, this paper evaluates tablets with a range of film coating thickness measured using OCT and terahertz pulsed imaging (TPI) in an off-line setting. In order to facilitate automated ...

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    6. 3D nondestructive testing system with an affordable multiple reference optical-delay-based optical coherence tomography

      3D nondestructive testing system with an affordable multiple reference optical-delay-based optical coherence tomography

      Optical coherence tomography (OCT) is emerging as a powerful noncontact imaging technique, allowing high-quality cross-sectional imaging of scattering specimens nondestructively. However, the complexity and cost of current embodiments of an OCT system limit its use in various nondestructive testing (NDT) applications at resource-limited settings. In this paper, we demonstrate the feasibility of a novel low-cost OCT system for a range of nondestructive testing (NDT) applications. The proposed imaging system is based on an enhanced time-domain OCT system with a low cost and small form factor reference arm optical delay, called multiple reference OCT (MR-OCT), which uses a miniature voice coil ...

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    7. In-Line Monitoring of a Pharmaceutical Pan Coating Process by Optical Coherence Tomography

      In-Line Monitoring of a Pharmaceutical Pan Coating Process by Optical Coherence Tomography

      This work demonstrates a new in-line measurement technique for monitoring the coating growth of randomly moving tablets in a pan coating process. In-line quality control is performed by an optical coherence tomography (OCT) sensor allowing nondestructive and contact-free acquisition of cross-section images of film coatings in real time. The coating thickness can be determined directly from these OCT images and no chemometric calibration models are required for quantification. Coating thickness measurements are extracted from the images by a fully automated algorithm. Results of the in-line measurements are validated using off-line OCT images, thickness calculations from tablet dimension measurements, and weight ...

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    8. Feature Of The Week 4/26/2015: Optical Teardown of a Kindle Paperwhite Display by OCT

      Feature Of The Week 4/26/2015: Optical Teardown of a Kindle Paperwhite Display by OCT

      The Amazon Kindle Paperwhite is an advanced electronic book reader that features a black and white electrophoretic display as well as capacitive multitouch screen capability and an internal lightguide with an optical scattering layer to provide uniform, white light illumination. Teardowns, where a new electronic gadget is disassembled and photographed are commonly found on technically oriented web sites. Here we perform an “optical teardown” of the first generation Kindle Paperwhite display by Optical Coherence Tomography (OCT). All the display layers can be imaged by OCT as well as the thin film transistor array on the back side for driving the ...

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    9. Dual Modality Noncontact Photoacoustic and Spectral Domain OCT Imaging

      Dual Modality Noncontact Photoacoustic and Spectral Domain OCT Imaging

      We developed a multimodal imaging system, combining noncontact photoacoustic imaging and optical coherence tomography (OCT). Photoacoustic signals are recorded without contact to the specimens’ surface by using an interferometric technique. The interferometer is realized within a fiber-optic network using a fiber laser at 1550 nm as source. The fiber-optic network allows the integration of a fiber-based OCT system operating at a wavelength region around 1310 nm. Light from the fiber laser and the OCT source are multiplexed into one fiber using wavelength-division multiplexing. The same focusing optics is used for both modalities. Back-reflected light from the sample is demultiplexed and ...

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      Mentions: RECENDT
    10. Optical coherence tomography for nondestructive evaluation of fuel rod degradation

      Optical coherence tomography for nondestructive evaluation of fuel rod degradation

      Nuclear power plants regularly inspect fuel rods to ensure safe and reliable operation. Excessive corrosion can cause fuel failures which can have significant repercussions for the plant, including impacts on plant operation, worker exposure to radiation, and the plant's INPO rating. While plants typically inspect for fuel rod corrosion using eddy current techniques, these techniques have known issues with reliability in the presence of tenacious, ferromagnetic crud layers that can deposit during operation, and the nondestructive evaluation (NDE) inspection results can often be in error by a factor of 2 or 3. For this reason, alternative measurement techniques, such ...

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    11. Optical coherence tomography based particle image velocimetry (OCT-PIV) of polymer flows

      Optical coherence tomography based particle image velocimetry (OCT-PIV) of polymer flows

      The measurement of spatially resolved velocity distributions is crucial for modelling flow and for understanding properties of materials produced in extrusion processes. Traditional methods for flow visualization such as particle image velocimetry (PIV) rely on optically transparent media and cannot be applied to turbid polymer melts. Here we present optical coherence tomography as an imaging technique for PIV data processing that allows for measuring a sequence of time resolved images even in turbid media. Time-resolved OCT images of a glass-fibre polymer compound were acquired during an extrusion process in a slit die. The images are post-processed by ensemble cross-correlation to ...

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    12. Angular scan optical coherence tomography imaging and metrology of spherical gradient refractive index preforms

      Angular scan optical coherence tomography imaging and metrology of spherical gradient refractive index preforms

      The fabrication of high-performance spherical gradient refractive index (S-GRIN) optics requires nondestructive metrology techniques to inspect the samples. We have developed an angular-scan, swept-source-based, Fourier-domain optical coherence tomography system centered at 1318 nm with 5 mm imaging depth capable of 180̊ polar scan and 360̊ azimuthal scan to investigate polymeric S-GRIN preforms. We demonstrate a method that enables simultaneous mapping of the group optical thickness, physical thickness, the radially-averaged group refractive index, and the transmitted wavefront of the S-GRIN preforms. The angular scan OCT imaging and metrology enables direct visualization, molding uniformity characterization, and optical property evaluations of the preforms ...

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    13. Visualization of dynamic boiling processes using high-speed optical coherence tomography

      Visualization of dynamic boiling processes using high-speed optical coherence tomography

      Investigating microscale nucleate boiling processes with high heat flux requires experimental visualization and quantification with high spatial resolution in the micrometer range as well as a sufficient temporal resolution. Numerous measurement techniques are employed for providing comprehensive experimental data on microscale boiling processes and other multiphase flows. In this context, optical coherence tomography (OCT) has been introduced recently for the visualization of quasistatic growing vapor bubbles in turbid fluids with a high spatial resolution. Since OCT detects backscattered light, only one optical access is necessary and OCT is feasible for measurements in turbid media, where other imaging techniques fail. Within ...

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    14. Tomographic Inspection of Fiber Coils Using Optical Coherence Tomography

      Tomographic Inspection of Fiber Coils Using Optical Coherence Tomography

      We report the first study of using optical coherence tomography (OCT) to inspect the winding quality of fiber optical gyro coils. We use a swept-source OCT system to scan a quadrupole-wind fiber coil for obtaining its two-dimensional and three-dimensional (3D) tomographic images. The defects beneath the surface of the fiber coil, which otherwise are invisible by video inspection, can be clearly identified with such tomographic images. The winding quality of each layer can also be independently visualized with the reconstructed 3D images from different angles or in different sections. We believe that the proposed method will be useful to ensuring ...

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    15. Automated pharmaceutical tablet coating layer evaluation of optical coherence tomography images

      Automated pharmaceutical tablet coating layer evaluation of optical coherence tomography images

      Film coating of pharmaceutical tablets is often applied to influence the drug release behaviour. The coating characteristics such as thickness and uniformity are critical quality parameters, which need to be precisely controlled. Optical coherence tomography (OCT) shows not only high potential for off-line quality control of film-coated tablets but also for in-line monitoring of coating processes. However, an in-line quality control tool must be able to determine coating thickness measurements automatically and in real-time. This study proposes an automatic thickness evaluation algorithm for bi-convex tables, which provides about 1000 thickness measurements within 1 s. Beside the segmentation of the coating ...

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    16. Optical inspection of solar cells using phase-sensitive optical coherence tomography

      Optical inspection of solar cells using phase-sensitive optical coherence tomography

      The inspection and measurement of solar cells has become an important technique in evaluating the efficiency and quality of solar cell devices. Currently, surface defect detection of solar cells can be achieved by several approaches such as machine vision, photoluminescence, and electroluminescence imaging techniques. Nevertheless, it is still difficult to inspect the inner structures of solar cells. In response to this need, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) have become common techniques for investigating the nanostructures of solar cells. However, both carry the disadvantages of destructive imaging, high cost, and a small inspection area. Moreover, it is ...

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    17. High resolution Fourier domain optical coherence tomography in the 2 um wavelength range using a broadband supercontinuum source

      High resolution Fourier domain optical coherence tomography in the 2 um wavelength range using a broadband supercontinuum source

      A 220 nm bandwidth supercontinuum source in the two-micron wavelength range has been developed for use in a Fourier domain optical coherence tomography (FDOCT) system. This long wavelength source serves to enhance probing depth in highly scattering material with low water content. We present results confirming improved penetration depth in high opacity paint samples while achieving the high axial resolution needed to resolve individual paint layers. This is the first FDOCT developed in the 2 μm wavelength regime that allows fast, efficient capturing of 3D image cubes at a high axial resolution of 13 μm in air (or 9 μm ...

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    18. Hydrogel-coated feed spacers in two-phase flow cleaning in spiral wound membrane elements: A novel platform for eco-friendly biofouling mitigation

      Hydrogel-coated feed spacers in two-phase flow cleaning in spiral wound membrane elements: A novel platform for eco-friendly biofouling mitigation

      Biofouling is still a major challenge in the application of nanofiltration and reverse osmosis membranes. Here we present a platform approach for environmentally friendly biofouling control using a combination of a hydrogel-coated feed spacer and two-phase flow cleaning. Neutral (polyHEMA-co-PEG 10 MA), cationic (polyDMAEMA) and anionic (polySPMA) hydrogels have been successfully grafted onto polypropylene (PP) feed spacers via plasma-mediated UV-polymerization. These coatings maintained their chemical stability after 7 days incubation in neutral (pH 7), acidic (pH 5) and basic (pH 9) environments. Anti-biofouling properties of these coatings were evaluated by Escherichia coli attachment assay and nanofiltration experiments at a TMP ...

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    19. Quantitative assessment of touch-screen panel by nondestructive inspection with three-dimensional real-time display optical coherence tomography

      Quantitative assessment of touch-screen panel by nondestructive inspection with three-dimensional real-time display optical coherence tomography

      We investigated the use of optical coherence tomography (OCT) to measure several materials immersed in optical adhesives. The effects of variations in the concentration, physical characteristics, and thickness of the materials were studied, and these parameters were found to significantly affect the OCT measurement. The materials were selected for their distinct spectral properties in the infrared region. To ensure reliability, we acquired images using a scanning electron microscope after performing the semiconductor production process. We verified the feasibility of the application of OCT for defect inspection and product verification of touch-screen panels.

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    20. Optical coherence tomography as film thickness measurement technique

      Optical coherence tomography as film thickness measurement technique

      Optical coherence tomography (OCT) is a powerful optical method, noninvasive and noncontact diagnostic method. Although it is usually used for medical examinations, particularly in ocular exploration; it can also be used in optical metrology as measure technique. In this work, we use OCT to measure thicknesses of films. In OCT, depth profiles are constructed by measuring the time delay of back reflected light by interferometry measurements. Frequency in k-space is proportional to optical path difference. Then the reflectivity profile is obtained by a Fourier transformation, and the difference between two successive peaks of the resulting spectrum gives the film thickness ...

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    21. Feature Of The Week 01/04/2015: Zhejiang University Investigates Ultrawide-Field SD-OCT for NDE of Large Glass Surfaces

      Feature Of The Week 01/04/2015: Zhejiang University Investigates Ultrawide-Field SD-OCT for NDE of Large Glass Surfaces

      Due to its merits of nondestruction and high-resolution, the use of OCT in material industry is increased recently. Besides profilometry of metal, monitoring of printed electronics, nondestructive inspection of glass is another important application. Material defects such as bubbles, impurities, and distortion affect the quality of glass. To realize quality control of glass, a technique for nondestructive inspection of glass is required. Given the large amount of glass productions, a large field-of-view (FOV) is necessary for the system to achieve high-speed inspection. However, as the required FOV becomes large, conventional OCT system always encounters the problem of image distortion because ...

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    22. Polarization-sensitive optical coherence tomography for ceramic materials inspection

      Polarization-sensitive optical coherence tomography for ceramic materials inspection

      Ceramics production is looking for a fast, reliable and non-destructive method that can be implemented on site for defect detection and analysis. In this paper we present polarization-sensitive optical coherence tomography (PS-OCT) as a method for defect inspection. Proposed extensions to standard OCT provide additional information for complete characterization of tested object. We compare OCT and microscope imaging that can easily detect enamel layer defects. The object under test is a sample ceramic plate with several defects occurring in production process. Results of OCT imaging show those defects are only in enamel layer without any effect on potsherd layer.

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    23. Optical Coherence Tomography for Material Characterization (Thesis)

      Optical Coherence Tomography for Material Characterization (Thesis)

      Optical coherence tomography (OCT) is a non-invasive, contactless and high resolution imaging method, which allows the reconstruction of two or three dimensional depth-resolved images in turbid media. In the past 20 years, OCT has been extensively developed in the field of biomedical diagnostics, while OCT in the non-destructive testing (NDT) field is lagging far behind. The aim of this thesis is to use OCT as a novel NDT technique for material structure characterization and damage detection. Besides an overview of the OCT fundamentals and developments, the thesis is mainly driven by three tasks: instrument design, signal processing, and applications. An ...

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    24. Gravity-driven membrane filtration as pretreatment for seawater reverse osmosis: Linking biofouling layer morphology with flux stabilization

      Gravity-driven membrane filtration as pretreatment for seawater reverse osmosis: Linking biofouling layer morphology with flux stabilization

      In this study gravity-driven membrane (GDM) ultrafiltration is investigated for the pretreatment of seawater before reverse osmosis (RO). The impacts of temperature (21 ± 1 and 29 ± 1 °C) and hydrostatic pressure (40 and 100 mbar) on dynamic flux development and biofouling layer structure were studied. The data suggested pore constriction fouling was predominant at the early stage of filtration, during which the hydrostatic pressure and temperature had negligible effects on permeate flux. With extended filtration time, cake layer fouling played a major role, during which higher hydrostatic pressure and temperature improved permeate flux. The permeate flux stabilized in a range ...

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