TY - CONF A1 - Spranger, Holger A1 - Beckmann, Jörg A1 - Boehm, Rainer T1 - THz-TOF saft & ola for the detection of inherent discontinuities in dielectric materials N2 - T-rays are electromagnetic waves with frequencies between 0.3 and 10 THz. The ability to penetrate dielectric materials makes them attractive to reveal discontinuities in polymer and ceramic materials. THz-Time Domain Spectroscopy Systems (THz-TDS) are available which operates with THz-pulses. In THz-TDS the travelling time (ToF) and shape of the pulse changes if it interacts with the basic material and its discontinuities. Several reconstruction techniques have been already demonstrated in the context of THz-ToF. Nevertheless, tomographic reconstruction procedures, developed for x-ray computed tomography (CT) ap-plications, have been preferably applied. As a result, reliable tomograms could be presented in case of existing minor refraction property differences between the defect and its surrounding material. Nevertheless geometric artefacts could be observed. The strong restriction of the CT application for the inspection of dielectric plastics that engaged us to develop a recon-struction technique that takes refraction into account. A time domain SAFT based algorithm will be presented, which is able to visualize discontinuities properly in dimension and location, if the base materials shape and its refractive index are considered. The algorithm became more challenging in case of multilayer composites. For that reason an Optical Layer algorithm was developed. Measurements on representative samples with a variety of artificially produced small and large size defects will be shown. The calculated tomograms will be demonstrated to discuss and evaluate the benefits and limits of the two different reconstruction approaches. T2 - QNDE 2016 CY - Atlanta, G.A, USA DA - 17.07.2016 KW - THz KW - Synthetic Aperture Focusing KW - Layer Reconstruction KW - FMM PY - 2016 AN - OPUS4-37246 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Spranger, Holger A1 - Beckmann, Jörg T1 - THz-ToF techniques for the detection of inherent discontinuities in dielectric materials based on SAFT N2 - The ability to penetrate dielectric materials makes T-rays attractive to reveal discontinuities in polymer and ceramic materials. Changes of travelling time (ToF) and pulse shape due to the interactions of THz pulses with the dielectric material and its inherent discontinuities can be observed. A tomogram of the object under the test can be reconstructed from time of flight diffraction (ToFD) scans if a synthetic focusing aperture (SAFT) algorithm is applied. T2 - 7th International Workshop on Terahertz Technology and Applications CY - Kaiserslautern, Germany DA - 15.03.2016 KW - Terahertz synthetic aperture dielectric materials PY - 2016 AN - OPUS4-36221 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Spranger, Holger A1 - Boehm, Rainer A1 - Beckmann, Jörg T1 - THz-ToF techniques for the detection of inherent discontinuities in dielectric materials based on a SAFT – and an Optical Layer reconstruction algorithm N2 - Electromagnetic waves with frequencies between 0.1 and 10 THz are described as THz-radiation (T-ray). The ability to penetrate dielectric materials makes T-rays attractive to reveal discontinuities in polymer and ceramic materials. THz-Time Domain Spectroscopy Systems (THz-TDS) are available on the market today which operates with THz-pulses transmitted and received by optically pumped semiconductor antennas. In THz-TDS the travelling time (ToF) and shape of the pulse is changed if it interacts with the dielectric material and its inherent disconti-nuities. A tomogram of the object under the test can be reconstructed from time of flight diffraction (ToFD) scans if a synthetic focusing aperture (SAFT) algorithm is applied. Otherwise, planar discontinuities like cracks in plastics or delaminated lay-ers in composites can be abstracted as layers located at any angle in relation to the outer sample surface direction. A tomogram from the scanned sample can then be reconstructed in case the interactions of electromagnetic pulses with the existing in-herent interfaces are detectable and a model is assumed which describes the device under the test as multilayer structure composed of thin layers with different dielec-tric properties. A short description of both the SAFT – and Optical Layer algorithm for the recon-struction of the inherent structure is initially given. Measurements on representative samples with a variety of artificially produced small and large scale. Reconstructed tomograms are presented to discuss and evaluate the benefits and limits of the two different reconstruction approaches. T2 - 19th World Conference on Non-Destructive Testing 2016 CY - Munich, Germany DA - 13.06.2016 KW - SAFT KW - ToF KW - Optical layer reconstruction KW - Dielectric materials KW - THz PY - 2016 AN - OPUS4-36591 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Spranger, Holger A1 - Beckmann, Jörg A1 - Boehm, Rainer T1 - THz-ToF techniques for the detection of inherent discontinuities in dielectric materials based on a SAFT – and an optical layer reconstruction algorithm N2 - Electromagnetic waves with frequencies between 0.1 and 10 THz are described as THz-radiation (T-ray). The ability to penetrate dielectric materials makes T-rays attractive to reveal discontinuities in polymer and ceramic materials. THz-Time Domain Spectroscopy Systems (THz-TDS) are available on the market today which operates with THz-pulses transmitted and received by optically pumped semiconductor antennas. In THz-TDS the travelling time (ToF) and shape of the pulse is changed if it interacts with the dielectric material and its inherent discontinuities. A tomogram of the object under the test can be reconstructed from time of flight diffraction (ToFD) scans if a synthetic focusing aperture (SAFT) algorithm is applied. Otherwise, planar discontinuities like cracks in plastics or delaminated layers in composites can be abstracted as layers located at any angle in relation to the outer sample surface direction. A tomogram from the scanned sample can then be reconstructed in case the interactions of electromagnetic pulses with the existing inherent interfaces are detectable and a model is assumed which describes the device under the test as multilayer structure composed of thin layers with different dielectric properties. A short description of both the SAFT – and Optical Layer algorithm for the reconstruction of the inherent structure is initially given. Measurements on representative samples with a variety of artificially produced small and large scale. Reconstructed tomograms are presented to discuss and evaluate the benefits and limits of the two different reconstruction approaches. T2 - 19th World Conference on Non-Destructive Testing 2016 CY - Munich, Germany DA - 13.06.2016 KW - THz SAFT Optical layer reconstruction PY - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-365866 SN - 978-3-940283-78-8 VL - 158 SP - 1 EP - 10 AN - OPUS4-36586 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -