1. Articles in category: NDE/NDT

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    1. 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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    2. Feature of the Week 10/26/14: 3D Polymer Weld Seam Characterization Based on OCT Laser Transmission Welding Applications

      Feature of the Week 10/26/14: 3D Polymer Weld Seam Characterization Based on OCT Laser Transmission Welding Applications

      Plastics have low weight but a high weight to strength ratio and a good corrosion resistance allied to a high degree of freedom on its form design. These characteristics lead plastics to be used in several technical systems with high production and application requirements. Herewith the complete production chain of these components as well as their integration in technical systems are also subjected to high standards. The joining of plastics and polymers is an important step in this process chain, as often at this stage pre-processed parts with a high added value are machined. Especially in high performance production chains ...

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    3. Optical coherence tomography for shape and radius of curvature measurements of deeply curved machined metallic surfaces: a comparison with two-beam laser interferometry

      Optical coherence tomography for shape and radius of curvature measurements of deeply curved machined metallic surfaces: a comparison with two-beam laser interferometry

      An application of optical coherence tomography (OCT) for measuring shape and the radius of curvature of deeply curved metallic surfaces in precision mechanical components is demonstrated. Measurements carried out by OCT technique on concave and convex hemispherical metallic surfaces generated by diamond turning process is presented. The technique is compared with a two-beam laser interferometric method for determinations of shape errors and radius of curvature. It is shown that OCT is a useful tool for three-dimensional shape determinations for deeply curved surfaces such as hemispheres and has advantages over two-beam laser interferometric method.

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      Mentions: K. Divakar Rao
    4. Metrology research on PDMS phantoms for evaluating resolution performance of OCT systems

      Metrology research on PDMS phantoms for evaluating resolution performance of OCT systems

      Imaging resolution, an important performance parameter of OCT systems, can be evaluated by suitable point spread function (PSF) phantoms. In this paper, we propose an innovative method to prepare PSF phantoms by mixing polystyrene microspheres of standard sizes with transparent polymer - polydimethylsiloxane (PDMS). Detailed procedures as well as specific design are described, and the produced PSF phantoms are employed to verify OCT system resolution performance by analyzing corresponding point spread functions. For comparison, images of the standard-size microspheres are provided by measuring the PSF phantoms with optical microscope.

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    5. Feature Of The Week 9/21/14: National University of Singapore Investigates OCT as a Tool for Characterization of Complex Biological Surfaces Including Morphology of Crab Shells

      Feature Of The Week 9/21/14: National University of Singapore Investigates OCT as a Tool for Characterization of Complex Biological Surfaces Including Morphology of Crab Shells

      The advent of scanning electron microscopy has facilitated our understanding of the In recent years, there has been a growing interest in the study of natural biological surfaces in the search for novel solutions in surface engineering design from nature. Most methods for surface imaging of natural biological samples are however, sacrificial and require that samples be sectioned and prepared for characterization. One example is the use of the scanning electron microscope (SEM) to obtain detailed images of microtopography, where a section of the specimen is cut and sputter coated with electrically conductive material like gold or platinum for scanning ...

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    6. 3D Polymer Weld Seam Characterization Based on Optical Coherence Tomography for Laser Transmission Welding Applications

      3D Polymer Weld Seam Characterization Based on Optical Coherence Tomography for Laser Transmission Welding Applications

      Laser transmission welding is an established single-stage plastic joining process, which enables hermetically sealed joints under the workpiece surface. The process requires joining partners with proper degrees of transmission and absorption to the processing wavelength. For reaching a stable process an in-process quality assurance is very valuable. Current monitoring systems have a limited usage, as no quantitative information of the weld itself is obtained without its destruction. In medical and pharmaceutical applications a weld with leakage is e.g. unacceptable. The main objective of this paper is the presentation of the optical coherence tomography as a tool for the quality ...

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    7. Two-dimensional optical coherence tomography for real-time structural dynamical characterization

      Two-dimensional optical coherence tomography for real-time structural dynamical characterization

      We present a two-dimensional optical coherence vibration tomography (2DOCVT) system with an ultra-precision displacement resolution of ~0.1 nm that is capable of in site real-time absolute displacement measurement of structural line vibrations. Experimental results of sinusoidal, sweep and impulse vibrations were reported. The key figures of merit such as the 2DOCVT system could obtain fast line vibration measurement without scanning and it also could be used to capture structural modal parameters in one single impulse excitation measurement without any vibration excitation input information, making it attractive for the application in low-frequency vibration measurement and response-only modal analysis.

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    8. Second International Symposium on Optical Coherence Tomography for Non-Destructive Testing March 25th, 2015

      Second International Symposium on Optical Coherence Tomography for Non-Destructive Testing March 25th, 2015

      Optical Coherence Tomography (OCT) is a well-qualified tool for contactless, structural imaging of various samples. Already well-established in medical applications, in the last years the usage of OCT has been extended to diverse fields of non-destructive testing as well. In course of this progress, various devices for industrial measurements, process monitoring and research were developed. With our invitation to the second international symposium on Optical Coherence Tomography for Non-Destructive Testing OCT4NDT we like to settle a tradition from the well-founded forum for the OCT community. The symposium is intended to serve as a platform enabling an exchange of information on ...

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      Mentions: RECENDT
    9. Utilizing Optical Coherence Tomography in the Nondestructive and Noncontact Measurement of Egg Shell Thickness

      Utilizing Optical Coherence Tomography in the Nondestructive and Noncontact Measurement of Egg Shell Thickness

      The goal of this study was to measure the thickness of egg shells without any contact and by utilizing a nondestructive method that sends infrared light beam on the egg. We obtain measurement resolutions on the order of 7  μ m up to a penetration depth of 1.7 mm from the actual surface of the egg shell. The measurement results we obtained show that optical coherence tomography can be used to accurately determine the egg shell thickness. Scanning the light beam over the surface allows for measuring the egg profile and monitoring the variations of shell thickness. Since this information ...

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    10. Optical coherence elastography for measuring the deformation within glass fiber composite

      Optical coherence elastography for measuring the deformation within glass fiber composite

      Optical coherence elastography (OCE) has been applied to the study of microscopic deformation in biological tissue under compressive stress for more than a decade. In this paper, OCE has been extended for the first time, to the best of our knowledge, to deformation measurement in a glass fiber composite in the field of nondestructive testing. A customized optical coherence tomography system, combined with a mechanical loading setup, was developed to provide pairs of prestressed and stressed structural images. The speckle tracking algorithm, based on 2D cross correlation, was used to estimate the local displacements in micrometer scale. The algorithm was ...

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    11. Postdoctoral Research Associate Opening at University of Liverpool

      Postdoctoral Research Associate Opening at University of Liverpool

      Postdoctoral Research Associate £31,644 - £36,661 pa Faculty of Science and Engineering, Institute of Electrical Engineering and Electronics, Department of Electrical Engineering and Electronics Location: University Campus Ref: R-585803/WWW Closing date for receipt of applications: Fri, 22 Aug 2014 17:00:00 BST To undertake a project “ I ntelligent Manufacturing of Pharmaceutical Film Coating Using Terahertz Pulsed Imaging, Optical Coherence Tomography and Numerical Modelling ” in collaboration with Cambridge University. You will primarily focus on the development and integration of an optical coherence tomography (OCT) sensor for online monitoring and quality control of pharmaceutical coating process. The duties include ...

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    12. Micro-structural information of porous materials by optical coherence tomography

      Micro-structural information of porous materials by optical coherence tomography

      In this study we describe the use of Optical Coherence Tomography (OCT) to reveal microstructures and damages in porous media. An approach for establishing pore size and pore size distribution based upon OCT was developed. This approach was tested with oil source rock samples. Several sedimentary rock samples from Brazilian oil fields with porosity values ranging between 15% and 28% were evaluated, and the results agreed quite well with the traditional pycnometry method. In addition, pore size distribution for the samples in three dimensional planes were obtained. Finally, the experimental results proved that the OCT images with a suited digital ...

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    13. Perspectives of mid-infrared optical coherence tomography for inspection and micrometrology of industrial ceramics

      Perspectives of mid-infrared optical coherence tomography for inspection and micrometrology of industrial ceramics

      Optical coherence tomography (OCT) is a promising tool for detecting micro channels, metal prints, defects and delaminations embedded in alumina and zirconia ceramic layers at hundreds of micrometers beneath surfaces. The effect of surface roughness and scattering of probing radiation within sample on OCT inspection is analyzed from the experimental and simulated OCT images of the ceramic samples with varying surface roughnesses and operating wavelengths. By Monte Carlo simulations of the OCT images in the mid-IR the optimal operating wavelength is found to be 4 µm for the alumina samples and 2 µm for the zirconia samples for achieving sufficient ...

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    14. Calibration-free in-line monitoring of pellet coating processes via optical coherence tomography

      Calibration-free in-line monitoring of pellet coating processes via optical coherence tomography

      The paper presents a new in-line measurement technique for determining the coating thickness and uniformity of pharmaceutical pellets during film-coating in a fluid-bed apparatus. Non-destructive and contact-free process monitoring was performed via an optical coherence tomography (OCT) sensor providing cross-section images. Through the OCT measurements, the coating thickness could be determined directly, without a chemometric calibration model required for the quantification. The direct integration of the OCT sensor head into the fluid-bed systems allowed continuous monitoring of the coating growth. Moreover, the in-line investigation of the intra- and inter-pellet coating uniformity was possible due to OCT's high acquisition rate ...

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    15. Optical Coherence Tomography for the Study of Polymer and Polymer Matrix Composites

      Optical Coherence Tomography for the Study of Polymer and Polymer Matrix Composites

      Based on low-coherence interferometry, a hybrid optical coherence tomography (OCT) system has been built. It coupled time-domain OCT (TD-OCT) and Fourier-domain OCT (FD-OCT) into one system. TD-OCT can take the advantage of a large axial scan range while FD-OCT has superior performance in fast imaging as no axial scan is needed. The two imaging modalities shared a broad bandwidth light source with a centre wavelength of 1550 nm, which is less scattering and can give better penetration depth in the polymer-based material than the shorter wavelength used for biomedical applications. 2D translation stages were incorporated in the system to make ...

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    16. Feature Of The Week 5/25/14: Exploiting Advanced Low Coherence Interferometric Imaging Techniques for Material Research Applications

      Feature Of The Week 5/25/14: Exploiting Advanced Low Coherence Interferometric Imaging Techniques for Material Research Applications

      Researchers of CDL MS-MACH, Johannes Kepler University Linz, Austria, have recently demonstrated time domain polarization-sensitive full-field optical coherence microscopy (PS-FF-OCM) and low coherence interferometric second harmonic generation microscopy (iSHGM-OCM), as two current modifications of FF-OCM and scanning OCM, for extending the application range of FF-OCM and SHG microscopy adapted for use in material sciences [1]. The first technique, PS-FF-OCM, can simultaneously deliver reflectivity, retardation and (in-plane) optical axis information of birefringent materials as depth-resolved en-face information. Both amplitude and phase information in full field configuration are exploited by the applied demodulation scheme. In particular, this PS-FF-OCM technique has been developed ...

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    17. The influence of glass fibers on elongational viscosity studied by means of optical coherence tomography and X-ray computed tomography

      The influence of glass fibers on elongational viscosity studied by means of optical coherence tomography and X-ray computed tomography

      We report on the flow characteristics of glass-fiber-reinforced polymers in elongational rheometry. Unlike polymers with geometrically isotropic fillers, glass-fiber-reinforced polymers exhibit flow behavior and rheology that depend heavily on the orientation, the length distribution and the content of the fibers. One of the primary objectives of this study was to determine the effect of fiber orientation, concentration and distribution on the entrance pressure drop by means of optical coherence tomography (OCT), full-field optical coherence microscopy (FF-OCM), and X-ray computed tomography (X-CT). Both pressure drop and melt flow were analyzed using a special elongation die (Thermo Scientific X-Die [3]) for inline ...

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    18. Real-time data processing for in-line monitoring of a pharmaceutical coating process by optical coherence tomography

      Real-time data processing for in-line monitoring of a pharmaceutical coating process by optical coherence tomography

      Coating of tablets is a widely applied unit operation in the pharmaceutical industry. Thickness and uniformity of the coating layer are crucial for efficacy as well as for compliance. Not only due to different initiatives it is thus essential to monitor and control the coating process in-line. Optical coherence tomography (OCT) was already shown in previous works to be a suitable candidate for in-line monitoring of coating processes. However, to utilize the full potential of the OCT technology an automatic evaluation of the OCT measurements is essential. The automatic evaluation is currently implemented in MATLAB and includes several steps: (1 ...

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    19. Monitoring apparatus and method for in-situ measurement of wafer thicknesses for monitoring the thinning of semiconductor wafers and thinning apparatus comprising a wet etching apparatus and a monitoring apparatus

      Monitoring apparatus and method for in-situ measurement of wafer thicknesses for monitoring the thinning of semiconductor wafers and thinning apparatus comprising a wet etching apparatus and a monitoring apparatus

      According to the invention, a monitoring device (12) is created for monitoring a thinning of at least one semiconductor wafer (4) in a wet etching unit (5), wherein the monitoring device (12) comprises a light source (14), which is designed to emit coherent light of a light wave band for which the semiconductor wafer (4) is optically transparent. The monitoring device (12) further comprises a measuring head (13), which is arranged contact-free with respect to a surface of the semiconductor wafer (4) to be etched, wherein the measuring head (13) is designed to irradiate the semiconductor wafer (4) with the ...

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    20. Improved inspection and micrometrology of embedded structures in multi-layered ceramics: Development of optical coherence tomographic methods and tools (Thesis)

      Improved inspection and micrometrology of embedded structures in multi-layered ceramics: Development of optical coherence tomographic methods and tools (Thesis)

      Roll-to-roll manufacturing of micro components based on advanced printing, structuring and lamination of ceramic tapes is rapidly progressing. This large-scale and cost-effective manufacturing process of ceramic micro devices is however prone to hide defects within the visually opaque tape stacks. To achieve a sustainable manufacturing with zero defects in the future, there is an urgent need for reliable inspection systems. The systems to be developed have to perform high-resolution in-process quality control at high speed. Optical coherence tomography (OCT) is a promising technology for detailed in-depth inspection and metrology. Combined with infrared screening of larger areas it can solve the ...

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    21. Feature Of The Week 4/27/14: TU Delft Investigates 3D Monitoring of Delamination Growth in a Wind Turbine Blade Composite using OCT

      Feature Of The Week 4/27/14: TU Delft Investigates 3D Monitoring of Delamination Growth in a Wind Turbine Blade Composite using OCT

      The aim of this work is to use OCT imaging as a novel NDT tool to investigate delamination growth inside a wind turbine blade composite. The selected specimen is a glass fiber composite used for the spar webs. For the study, a compact fiber-optical OCT system coupled with a tensile test stage was built first. Then specimens with an interlaminar crack were statically loaded and stepwise scanned by the OCT system. The cross-sectional and volumetric images clearly show the microstructure and the crack within the specimen. After applying an optimized signal processing algorithm, 3D crack growth measured using OCT were ...

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    22. 3D monitoring of delamination growth in a wind turbine blade composite using optical coherence tomography

      3D monitoring of delamination growth in a wind turbine blade composite using optical coherence tomography

      In this paper, delamination and delamination growth in a glass fiber composite used for the spar webs in wind turbine blades is investigated by optical coherence tomography (OCT). The cross-sectional and volumetric images clearly showed the microstructure and the crack within the specimen. After applying an optimized signal processing algorithm, 3D crack growth measured using OCT were demonstrated for the first time to the best of our knowledge. The crack structures inside the composite material at different stages during the delamination growth were revealed.

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    23. Low coherence interferometric second harmonic generation microscopy for non-destructive material testing using a broadband 1550 nm fs-fiber laser

      Low coherence interferometric second harmonic generation microscopy for non-destructive material testing using a broadband 1550 nm fs-fiber laser

      In this paper low coherence interferometric second harmonic generation (SHG) imaging is successfully demonstrated using a compact broadband fs-fiber laser operating around 1550 nm. In combination with linear optical coherence microscopy, this SHG technique is tailored for structural and functional investigations of surfaces and subsurface regions of non-biological samples, like corrosion sites formed on metals below organic coatings.

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    1-24 of 184 1 2 3 4 5 6 7 8 »
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