1. Articles in category: NDE/NDT

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    1. 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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    2. 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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    3. 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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    4. 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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    5. 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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    6. 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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    7. 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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    8. 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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    9. 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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    10. 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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    11. 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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    12. 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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    13. 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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    14. Simultaneous detection of optical retardation and axis orientation by polarization-sensitive full-field optical coherence microscopy for material testing

      Simultaneous detection of optical retardation and axis orientation by polarization-sensitive full-field optical coherence microscopy for material testing

      We present a polarization-sensitive full-field optical coherence microscopy modality which is capable of simultaneously delivering depth resolved information on the reflectivity, optical retardation and optical axis orientation. In this way local birefringence, inherent stress–strain fields and optical anisotropies can be visualized with high resolution, as exemplified for various technical material applications.

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    15. In-Situ Optical Coherence Tomography (OCT) for the Time-Resolved Investigation of Crystallization Processes in Polymers

      In-Situ Optical Coherence Tomography (OCT) for the Time-Resolved Investigation of Crystallization Processes in Polymers

      Optical coherence tomography (OCT) is a low-coherence interferometric imaging method which was developed in the 1990s prevalently in the area of biomedical diagnostics. (1) It generates depth scans of samples in a contact-free, nondestructive manner. Having become a standard method for ophthalmologic examinations, (2, 3) within the past decade also applications outside the medical field were found, as summarized in a recent review (4) and with a special focus put on polymer science: in contrast to biological tissues, polymers usually do not contain water and therefore also light in the near-infrared (NIR) region, which otherwise would be absorbed, can be ...

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    16. Non-destructive evaluation of delamination growth in glass fiber composites using optical coherence tomography

      Non-destructive evaluation of delamination growth in glass fiber composites using optical coherence tomography

      Based on low coherence interferometry, a robust optical coherence tomography (OCT) system has been built. The system was used to monitor the growth of a delamination between the middle layers of a glass fiber composite under a static loading. Firstly specimens of the material used for the spar webs in wind turbines were prepared with an interlaminar crack from free edges. Then they were statically loaded by a customized tensile test stage to extend the delamination length and simultaneously scanned by the OCT system. To process the acquired data, an optimized signal processing algorithm was developed. The cross-sectional images clearly ...

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    17. Spectroscopic measurement of absorptive thin films by Spectral-Domain Optical Coherence Tomography

      Spectroscopic measurement of absorptive thin films by Spectral-Domain Optical Coherence Tomography

      A non-invasive method for measuring the refractive index, extinction coefficient and film thickness of absorptive thin films using spectral-domain optical coherent tomography is proposed, analyzed and experimentally demonstrated. Such an optical system employing a normal-incident beam of light exhibits a high spatial resolution. There are no mechanical moving parts involved for the measurement except the transversal scanning module for the measurement at various transversal locations. The method was experimentally demonstrated on two absorptive thin-film samples coated on transparent glass substrates. The refractive index and extinction coefficient spectra from 510 to 580 nm wavelength range and film thickness were simultaneously measured ...

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    18. Cost-effective optical coherence tomography spectrometer based on a tilted fiber Bragg grating

      Cost-effective optical coherence tomography spectrometer based on a tilted fiber Bragg grating

      A compact, fiber-based spectrometer for biomedical application utilizing a tilted fiber Bragg grating (TFBG) as integrated dispersive element is demonstrated. Based on a 45° UV-written PS750 TFBG a refractive spectrometer with 2.06 radiant/μm dispersion and a numerical aperture of 0.1 was set up and tested as integrated detector for an optical coherence tomography (OCT) system. Featuring a 23 mm long active region at the fiber the spectrum is projected via a cylindrical lens for vertical beam collimation and focused by an achromatic doublet onto the detector array. Covering 740 nm to 860 nm the spectrometer was optically ...

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    19. Optical Coherence Tomography as a Novel Tool for In-Line Monitoring of a Pharmaceutical Film-Coating Process

      Optical Coherence Tomography as a Novel Tool for In-Line Monitoring of a Pharmaceutical Film-Coating Process

      Optical coherence tomography (OCT) is a contact-free non-destructive high-resolution imaging technique based on low-coherence interferometry. This study investigates the application of spectral-domain OCT as an in-line quality control tool for monitoring pharmaceutical film-coated tablets. OCT images of several commercially-available film-coated tablets of different shapes, formulations and coating thicknesses were captured off-line using two OCT systems with centre wavelengths of 830 nm and 1325 nm. Based on the off-line image evaluation, another OCT system operating at a shorter wavelength was selected to study the feasibility of OCT as an in-line monitoring method. Since in spectral-domain OCT motion artefacts can occur as ...

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    20. Non-Contact Creep Measurement Based on Fourier Domain Optical Coherence Tomography

      Non-Contact Creep Measurement Based on Fourier Domain Optical Coherence Tomography

      A non-contact Fourier-domain optical coherence creep tomography (OCCT) is developed and employed in real-time non-contact creep measurement. Experiments on thermal deformation were carried out by using the self-developed OCCT to measure a high-temperature structure. In the OCCT system, a high-performance spectrometer, and a thermal light are, respectively, employed as the detector and the light source. Due to the broadband of the spectrometer and light source, the system provided high robust performance with an excellent deformation measurement resolution of sub-millimeter scale. Due to the energy leakage effect of FFT, a spectrum correction technique was employed to enhance the resolution of the ...

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    21. Optical characterization of ultra-short Bragg grating on lithium niobate ridge waveguide

      Optical characterization of ultra-short Bragg grating on lithium niobate ridge waveguide

      In this Letter, we report a technique to etch giant aspect ratio nanostructures in lithium niobate. An 8 μm long Bragg grating on a Ti : LiNbO 3 ridge waveguide was fabricated by combining optical-grade dicing and focused ion beam milling. The reflectivity was evaluated using an optical coherence tomography system: it is measured to be 53% for the TM wave and 47% for the TE wave. We study by 2D-FDTD the modeled behavior of the electromagnetic field when an angle exists between two consecutive sidewalls of the grating in order to understand the difference between ideal Bragg grating and experimental ...

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    22. Real-time critical dimension measurement of thin film transistor liquid crystal display patterns using optical coherence tomography

      Real-time critical dimension measurement of thin film transistor liquid crystal display patterns using optical coherence tomography

      A coherence scanning tomographic imaging system with an innovative signal correction method is presented for a critical dimension (CD) measurement of thin film transistor liquid crystal display patterns having multiple focus positions within a single field of view. To facilitate the analyzing of coherence signals, a simulation model based on fast Fourier transform method is proposed, and its simulated result is compared with the coherence signals from the actual experiments. The comparison shows that the majority of frequency characteristics from simulation modeling results are matched with the experimental results. However, in many edge regions, discrepancies in frequency characteristics between the ...

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    23. Optical Coherence Tomography (OCT) for Industrial NDT (Non-Destructive

      Optical Coherence Tomography (OCT) for Industrial NDT (Non-Destructive

      Optical coherence tomography (OCT) has evolved to a non-invasive standard biomedical analysis technique yielding a detail-rich cross-sectional image of living tissue. As a high frequency analog to and as a possible replacement of ultrasound examination techniques, optical coherence tomography delivers images of a much higher resolution well into the micrometer realm. The penetration depth possible with OCT is determined by the type of material under test and the wavelength used as shown in Figure 1. In medical applications, for human tissue investigations, and when using light sources in the short wave infrared, OCT penetration can reach 6mm and more (much ...

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