1. Articles in category: NDE/NDT

    1-24 of 208 1 2 3 4 5 6 7 8 9 »
    1. 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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    2. 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
    3. 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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    4. 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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    5. 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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    6. 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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    7. 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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    8. 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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    9. 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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    10. 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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    11. 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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    12. 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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    13. 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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    14. 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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    15. 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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    16. 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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    17. 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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    18. Ultrawide-field parallel spectral domain optical coherence tomography for nondestructive inspection of glass

      Ultrawide-field parallel spectral domain optical coherence tomography for nondestructive inspection of glass

      Aiming at the requirements of real-time inspection in material industry, an ultrawide-field parallel SD-OCT system capable of visualizing cross-sectional image of internal structures by a single shot of a 2-D CMOS camera is developed. To achieve ultrawide-field parallel detection, one meniscus lens with negative dioptric is introduced as an additional relay lens and imaging optics including sample arm, relay lenses and spectrometer are optimized as a whole for desirable imaging quality. The developed system has an ultrawide-field of 35 mm and an axial range of 8 mm in air. The maximum on-axis sensitivity and the axial resolution are experimentally determined ...

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    19. DETECTION OF SUBSURFACE DAMAGE IN OPTICAL TRANSPARENT MATERIALSS USING SHORT COHERENCE TOMOGRAPHY

      DETECTION OF SUBSURFACE DAMAGE IN OPTICAL TRANSPARENT MATERIALSS USING SHORT COHERENCE TOMOGRAPHY

      This paper describes the use of short coherence interferometry for the detection of subsurface damage (SSD) in optical transparent materials. The method is based on an interferometer using a light source with a short coherence length. A time domain (TD) and a frequency domain (FD) approach are explained. The OCT method allows a nondestructive measurement of the SSD compared to the state of the art SSD metrology, where the sample is destroyed. Compared to previous results [Ser10] a frequency domain (FD) setup is build up which allows SSD measurements under production environment conditions. The results of the FD set are ...

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    20. Optical coherence tomography in the 2um wavelength regime for paint and other high opacity materials

      Optical coherence tomography in the 2um wavelength regime for paint and other high opacity materials

      An optical coherence tomography system using a compact fiber source emitting amplified spontaneous emission at central wavelength of 1960 nm with bandwidth of 40 nm is developed to enhance the probing depth in a highly scattering material with low water content. Examples of application to paint are used to demonstrate significantly improved penetration depth in high opacity materials in the 2-μm wavelength regime.

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    21. A Novel Approach to Characterizing the Growth of a Fouling Layer during Membrane Filtration via Optical Coherence Tomography

      A Novel Approach to Characterizing the Growth of a Fouling Layer during Membrane Filtration via Optical Coherence Tomography

      Fouling control is one of the critical issues in membrane filtration and plays a very important role in water/wastewater treatment. Better understanding of the underlying fouling mechanisms entails novel characterization techniques that can realize a real-time non-invasive observation and provide high resolution images recording the formation of a fouling layer . This work presents a characterization method based on optical coherence tomography (OCT), which is able to detect the internal structures and motions by analyzing the interference signals. An OCT system was incorporated with a lab-scale membrane filtration system, and the growth of the fouling layer was observed by using ...

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    22. Machining Head For A Laser Machining Device Comprising A PATH-LENGTH Modulator In The Reference Arm; Method For Laser Machining Of A Workpiece, Comprising Corresponding Steps

      Machining Head For A Laser Machining Device Comprising A PATH-LENGTH Modulator In The Reference Arm; Method For Laser Machining Of A Workpiece, Comprising Corresponding Steps

      The invention relates to a machining head for a laser machining device, which is equipped for machining a workpiece (24) using laser radiation (30). The laser machining head comprises an adjustable focusing optical unit (34), which focuses the laser radiation (30) in a focal spot (22). The distance between the focal spot (22) and a machining head can be modified by modifying the focal length of the focusing optical unit (34). A scanning apparatus (44) deflects the laser radiation (30) in different directions. An optical coherence tomography device (48) measures a distance between the treatment head and the workpiece (24 ...

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    23. Accurate and automated image segmentation of 3D optical coherence tomography data suffering from low signal-to-noise levels

      Accurate and automated image segmentation of 3D optical coherence tomography data suffering from low signal-to-noise levels

      Optical coherence tomography (OCT) has proven to be a useful tool for investigating internal structures in ceramic tapes, and the technique is expected to be important for roll-to-roll manufacturing. However, because of high scattering in ceramic materials, noise and speckles deteriorate the image quality, which makes automated quantitative measurements of internal interfaces difficult. To overcome this difficulty we present in this paper an innovative image analysis approach based on volumetric OCT data. The engine in the analysis is a 3D image processing and analysis algorithm. It is dedicated to boundary segmentation and dimensional measurement in volumetric OCT images, and offers ...

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    24. Air etalon facilitated simultaneous measurement of group refractive index and thickness using spectral interferometry

      Air etalon facilitated simultaneous measurement of group refractive index and thickness using spectral interferometry

      A simple method based on air etalons of a transparent cavity is proposed to simultaneously measure the group refractive index and thickness of a transparent optical plate by spectral domain low coherence interferometry. In this method, only a single beam path is needed in contrast to the two beam paths, the reference and sample arms, of the conventional Michelson interferometer. An empty cavity is first constructed in the beam path by two glass plates. Then the transparent plate under test is inserted into the cavity, so that two air gaps are formed in the cavity. A beam of light of ...

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    1-24 of 208 1 2 3 4 5 6 7 8 9 »
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