1. Articles from David Stifter

    1-24 of 31 1 2 »
    1. Full-field optical coherence tomography in a balanced detection mode

      Full-field optical coherence tomography in a balanced detection mode

      We discuss balanced time-domain full-field optical coherence tomography (FF-OCT) realized in a Mach–Zehnder configuration. The balanced detection scheme and spatial phase shifting allow single-shot acquisition and reconstruction in FF-OCT. Combined with a 2D quadrature signal-based demodulation technique applying the Riesz transform, previously illustrated for a dual-shot temporal phase shifting in FF-OCT, we demonstrate the concept for single-shot spatial phase shifting. The monitoring of dynamic processes by time-domain FF-OCT is enabled by this approach. The advantage of single-shot acquisition consists of having no failure due to phase changes over time. However, it demands an accurate registration of both spatially shifted ...

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    2. 10th International Conference on Advances in Experimental Mechanics

      10th International Conference on Advances in Experimental Mechanics

      The 10th International Conference on Advances in Experimental Mechanics will be held September 1-3, 2015 at Heriot-Watt University in Edinburgh, United Kingtom. The conference focuses on research which advances experimental techniques across the very widest range of applications in mechanics, including stress, strain and vibration analysis. In this context, investigations and studies performed by low coherence techniques, as e.g. PS-OCT, Doppler OCT or Optical Coherence Elastography, are welcomed. Key dates: 15 January 2015 Deadline for on-line submission of 2-page extended abstracts 1 March 2015 Author notification Homepage: http://www.bssm.org/conf2015

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    3. 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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    4. 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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    5. 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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    6. Special session dedictated to OCT at the 16th International Conference on Experimental Mechanics - ICEM16, July 2014, Cambridge/UK

      Special session dedictated to OCT at the 16th International Conference on Experimental Mechanics - ICEM16, July 2014, Cambridge/UK

      Special session dedictated to OCT at the 16th International Conference on Experimental Mechanics - ICEM16, 7th to 11th July 2014, Cambridge/UK. The conference brings together internationally leading researchers across a wide range of disciplines in both academia and industry to interchange ideas and discuss new research in the area of experimental mechanics. A special session is dedicated to the application of OCT, which provides access in a non-invasive/non-destructive way to the interior of materials to study their structure and mechanical properties. Contributions for both, biological as well as non-biological applications and case studies, are welcomed as well as dedicated ...

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    7. Full Field Optical Coherence Microscopy: Imaging and Image Processing for Micro-Material Research Applications

      Full Field Optical Coherence Microscopy: Imaging and Image Processing for Micro-Material Research Applications

      Non-destructive optical imaging and probing techniques have found entrance and success in material sciences favoured by their non-invasive investigation character. X-ray computer tomography (CT) applied in a different size scale (e.g. as micro-CT and nano-CT [ 1 ]) is well established as a non-destructive technique in the field of material inspection. CT imaging delivers highly contrasted images of the internal of the specimens. It includes information about inclusions or cavities, and about the size and distribution of particles and pores within the technical material. Furthermore, ultrasound and acousto-optic imaging may also provide valuable insights into internal cracks and flaws, density or ...

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    8. Full field optical coherence microscopy for material testing: contrast enhancement and dynamic process monitoring

      Full field optical coherence microscopy for material testing: contrast enhancement and dynamic process monitoring

      We illustrate the abilities of an advanced full-field optical coherence microscope (FF-OCM) setup for characterization of technical materials with internal micro-structures and present this technique also for dynamic process monitoring, as strain-stress tests. Additionally we briefly illustrate the potential of image processing in context of the chosen applications. Furthermore, contrast modification techniques based on Fourier plane filtering are discussed.

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    9. Feature Of The Week 1/6/13: Johannes Kepler University Linz Investigates Full-Filed Optical Coherence Microscopy For Dynamic Imaging

      Feature Of The Week 1/6/13: Johannes Kepler University Linz Investigates Full-Filed Optical Coherence Microscopy For Dynamic Imaging

      The observation of internal dynamic processes is a crucial task in biomedicine as well as for material sciences, with full-field optical coherence microscopy (FF-OCM) exhibiting advantageous features: the full image content is taken at once at a defined depth position with a high lateral resolution. Usually two-dimensional (2D) CCD detectors are applied or - for high speed FF-OCM imaging - complementary metal oxide semiconductor (CMOS) cameras. Besides a fast optical acquisition setup, an appropriate demodulation scheme has also to be realized: In the case of the acquisition of static scenes, phase stepping is conventionally used, with multiple phase-shifted frames being recorded. However ...

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    10. Full-field optical coherence microscopy with Riesz transform-based demodulation for dynamic imaging

      Full-field optical coherence microscopy with Riesz transform-based demodulation for dynamic imaging

      We present dynamic full-field optical coherence microscope imaging using a scientific complementary metal oxide semiconductor camera in conjunction with a demodulation scheme based on the Riesz transform and monogenic signals. The potential of our approach is verified by a comparison with conventional phase-stepping as well as with an analytic reconstruction method and finally exemplified for dynamic mechanical testing of a polymer/fiber composite structure.

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    11. Contrast modification for ultra-high resolution low-coherence interference microscopy by Fourier-plane filtering

      Contrast modification for ultra-high resolution low-coherence interference microscopy by Fourier-plane filtering

      We present a novel full-field low-coherence interference (LCI) microscope, which exhibits ultra-high axial resolution due to a broadband super continuum light source and which is at the same time capable to generate different contrast modes by using Fourier-plane filtering with a spatial light modulator. By changing the phase and spatial frequencies of the backreflected wavefront of the specimen in the sample arm of the interferometer, we are able to change the contrast in the depth-resolved LCI images. By displaying different filters on the SLM, as e.g. spiral phase, the resulting images provide particular enhancement of edges and internal structures ...

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    12. Coherence Probe Microscopy Imaging and Analysis for Fiber-Reinforced Polymers

      Coherence Probe Microscopy Imaging and Analysis for Fiber-Reinforced Polymers

      The potential of full-field low coherence interferometric techniques for imaging internal structures, such as fibers, interfaces, or inclusions in technical materials is demonstrated by our coherence probe microscopy (CPM) setup. However, the huge amount of recorded data demand for an automatized enhancement and evaluation of the image data. We propose an automatic image analysis procedure adapted for full-field coherence probe microscopy, which we tested on fiber composite materials. The performed image enhancement and orientation analysis finally allow to cluster the internal fiber structures, to detect outliers and enable an improved characterization of investigated specimens supporting a sophisticated material design for ...

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    13. Spectral domain polarization sensitive optical coherence tomography at 1.55 μm: novel developments and applications for dynamic studies in materials science

      Spectral domain polarization sensitive optical coherence tomography at 1.55 μm: novel developments and applications for dynamic studies in materials science
      In this paper it is demonstrated, how research in optical coherence tomography (OCT) for biomedical diagnostics successfully triggered new developments in the field of mechanical material testing. With the help of a specifically designed, compact and robust spectral domain polarization sensitive OCT (SD-PS-OCT) setup, which is operating at 1.55 μm, dynamic investigations of technical materials - like bulk polymers and composite samples - can be performed under various conditions. Already by evaluating the speckle pattern of the standard SD-OCT images with advanced image processing methods, valuable information on the deformation and flow characteristics of samples subjected to tensile tests can be ...
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    14. Flexible contrast for low-coherence interference microscopy by Fourier-plane filtering with a spatial light modulator

      Flexible contrast for low-coherence interference microscopy by Fourier-plane filtering with a spatial light modulator

      We propose a full-field low-coherence interference (LCI) microscope that can provide different contrast modes using Fourier-plane filtering by means of a spatial light modulator. By altering the phase and spatial frequencies of the backreflected wavefront from the sample arm of the interferometer, we are able to change the contrast in the depth-resolved LCI images. We demonstrate that different types of contrast modes, such as, e.g., spiral phase contrast, can successfully be emulated to provide specific enhancement of internal structures and edges and to reveal complementary details within the samples under investigation.

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    15. Dynamic optical studies in materials testing with spectral-domain polarization-sensitive optical coherence tomography

      Dynamic optical studies in materials testing with spectral-domain polarization-sensitive optical coherence tomography
      By combining dynamic mechanical testing with spectral-domain polarization-sensitive optical coherence tomography (SD-PS-OCT) performed at 1550 nm we are able to directly investigate for the first time changes within scattering technical materials during tensile and fracture tests. Spatially and temporally varying polarization patterns, due to defects and material inhomogeneities, were observed within bulk polymer samples and used to finally obtain – with the help of advanced image processing algorithms – quantitative maps of the evolving internal stress distribution. Furthermore, locally increased stress within fiber-reinforced composite materials was identified in situ with SD-PS-OCT to cause depolarizing sites of fiber-matrix debonding prior the onset of ...
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    16. An investigation of the accelerated thermal degradation of different epoxy resin composites using x-ray micro computed tomography and optical coherence tomography

      Epoxy resin composites reinforced with hollow glass microspheres, microlight microspheres, 3D parabeam glass, and E-Glass individually were subjected to accelerated thermal degradation conditions. X-ray micro computed tomography (XμCT) was used to evaluate density changes, reinforcement filler damage, homogeneity, cracks and microcracks in the bulk of the different epoxy resin composites. XμCT 3D images, 2D reconstructed images and voids calculations revealed microspheres damage, filler distributions and showed cracks in all composites with different shapes and volume in response to the thermal degradation conditions. In addition, expansion of air bubbles/voids was observed and recorded in the microsphere and microlight epoxy composite ...
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    17. Masmicro micro-/nano-materials processing, analysis, inspection and materials knowledge management

      Abstract  The main goals of the ‘Material Innovation and Testing’ within MASMICRO are the identification of the miniature/micro-materials which are formable, development of new materials for forming and machining, development of an integrated material-testing system and study of material properties for design/analysis applications. Examples of collaborative work and results are presented regarding the processing of functional electrospun polymer micro-/nano-fibre structures and the characterization of their interface properties with tribological testing. By means of optical coherence tomography, a non-destructive inspection approach for these micro-/nano-structured webs was developed and it is also documented in the paper. Further, an ...
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    18. Quantitative phase reconstruction for orthogonal-scanning differential phase-contrast optical coherence tomography

      Quantitative phase reconstruction for orthogonal-scanning differential phase-contrast optical coherence tomography
      We present differential phase-contrast optical-coherence tomography (DPC-OCT) with two transversally separated probing beams to sense phase gradients in various directions by employing a rotatable Wollaston prism. In combination with a two-dimensional mathematical-reconstruction algorithm based on ... [Opt. Lett. 34, 1306-1308 (2009)]
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    19. Imaging the human retina in vivo with combined spectral-domain polarization-sensitive optical coherence tomography and scanning laser ophthalmoscopy

      Polarization-sensitive (PS) optical coherence tomography (OCT) allows for depth-resolved measurement of light polarizing properties of different layers in the human retina. Since their inherent polarizing properties are different, the retinal structures can be identified using PS-OCT. We present an ... [Proc. SPIE 7163, 71630N (2009)] published Wed Feb 18, 2009.
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    20. Spatially Resolved Stress Measurements in Materials with Polarisation-Sensitive Optical Coherence Tomography: Image Acquisition and Processing Aspects

      Abstract: We demonstrate that polarisation-sensitive optical coherence tomography (PS-OCT) is suitable for mapping the stress distribution within materials in a contact-free and non-destructive way. In contrast to transmission photoelasticity measurements, the samples do not have to be transparent but can be of scattering nature. Denoising and analysis of fringe patterns in single PS-OCT retardation images are demonstrated to be the bases for a quantitative whole-field evaluation of the internal stress state of samples under investigation.
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    21. Advanced Optical Coherence Tomography techniques: novel and fast imaging tools for non-destructive testing

      Advanced Optical Coherence Tomography techniques: novel and fast imaging tools for non-destructive testing
      We demonstrate that Optical Coherence Tomography (OCT), a method which was originally developed for depth-resolved imaging of biological tissue, is suited to adequately respond to different problems posed in the field of contactless material characterisation and non-destructive testing and evaluation. In detail, the potential of advanced OCT techniques like ultrahigh-resolution OCT, polarisation-sensitive OCT or spectral-domain OCT is evaluated and exemplified for the imaging and characterisation of different polymer and ceramic materials, as well as of whole components, like polymer coated medical metal stents
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    22. Investigation of polymer and polymer/fibre composite materials with optical coherence tomography

      Optical coherence tomography (OCT), a technique originally proposed for applications in the field of biomedical diagnostics, is shown to be an efficient measurement technique for a multitude of problems posed in technical engineering and material research. Especially advanced OCT modifications, involving ultrahigh-resolution (UHR) imaging and fast Fourier-domain (FD) techniques, show promising potential, as successfully demonstrated in this paper by a variety of applications from the field of polymer materials. Thin polymer films and multilayer structures as well as polymer blends and fibre-reinforced polymer composites are successfully evaluated by means of UHR-OCT and FD-OCT performed at different wavelengths. In addition, comparative ...
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    23. Ultrahigh-Resolution Transversal Polarization-Sensitive Optical Coherence Tomography: Structural Analysis and Strain-Mapping

      Abstract Optical coherence tomography (OCT), originally developed and so far nearly exclusively used for biomedical applications (e.g., [1,2]), is a contact-free, non-destructive technique based on low-coherence interferometry to image structures within translucent and turbid materials. Commonly, cross-sectional reflectivity images with a depth-resolution determined by the coherence length of the near-infrared light source are obtained. When OCT is performed in a polarization sensitive way (PS-OCT), additional information about birefringence within a material is obtained by mapping the retardation between ordinary and extraordinary rays [3]. Because birefringence is induced when strain occurs, PS-OCT provides depth resolved information about the internal ...
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    1-24 of 31 1 2 »
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