1. Articles in category: NDE/NDT

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    1. 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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    2. 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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    3. 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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    4. 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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    5. 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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    6. 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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    7. 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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    8. Non-destructive stress profile determination in chemically tempered glass

      Non-destructive stress profile determination in chemically tempered glass

      Apparatus, systems and methods for improving strength of thin cover glass for electronic devices are disclosed. Optical coherence tomography analysis may reveal fine details of a residual stress profile within chemically strengthened cover glass. One or more parameters of chemical strengthening treatments may be adjusted, based upon the analysis of the residual stress profile.

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    9. 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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    10. 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
    11. 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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    12. 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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    13. 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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    14. 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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    15. 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
    16. 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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    17. 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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    18. 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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    19. 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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    20. 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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    21. 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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    22. 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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    23. 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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