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  <doc>
    <id>50897</id>
    <completedYear/>
    <publishedYear>2020</publishedYear>
    <thesisYearAccepted/>
    <language>eng</language>
    <pageFirst>179</pageFirst>
    <pageLast>180</pageLast>
    <pageNumber/>
    <edition/>
    <issue/>
    <volume/>
    <type>conferenceobject</type>
    <publisherName/>
    <publisherPlace/>
    <creatingCorporation/>
    <contributingCorporation/>
    <belongsToBibliography>0</belongsToBibliography>
    <completedDate>--</completedDate>
    <publishedDate>--</publishedDate>
    <thesisDateAccepted>--</thesisDateAccepted>
    <title language="eng">Using spatial and temporal shaping of laser-induced diffuse thermal wave fields in thermography</title>
    <abstract language="eng">The diffuse nature of thermal waves is a fun-damental limitation in thermographic nonde-structive testing. In our studies we investigated different approaches by shaping the thermal wave fields which result from heating. We have used high-power laser sources to heat metallic samples. Using these spatial and temporal shaping techniques leads to a higher detection sensitivity in our measurements with the infra-red camera. In this contribution we show our implementation of shaping laser-induced diffuse thermal wave fields and the effect on the defect reconstruction quality.</abstract>
    <parentTitle language="eng">SMSI 2020 Proceedings</parentTitle>
    <identifier type="doi">10.5162/SMSI2020/C5.1</identifier>
    <enrichment key="eventName">SMSI 2020 Conference</enrichment>
    <enrichment key="eventPlace">Online meeting</enrichment>
    <enrichment key="eventStart">22.06.2020</enrichment>
    <enrichment key="eventEnd">25.06.2020</enrichment>
    <author>Mathias Ziegler</author>
    <author>Samim Ahmadi</author>
    <author>Philipp Daniel Hirsch</author>
    <author>Julien Lecompagnon</author>
    <author>Christian Hassenstein</author>
    <author>Erik Thiel</author>
    <author>Nelson Wilbur Pech May</author>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Thermal wave</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Diffusion</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>High-power laser</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Thermography</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Spatiotemporal shaping</value>
    </subject>
    <collection role="ddc" number="543">Analytische Chemie</collection>
    <collection role="institutes" number="">8 Zerstörungsfreie Prüfung</collection>
    <collection role="institutes" number="">8.3 Thermografische Verfahren</collection>
    <collection role="themenfelder" number="">Chemie und Prozesstechnik</collection>
    <collection role="fulltextaccess" number="">Datei im Netzwerk der BAM verfügbar ("Closed Access")</collection>
    <collection role="literaturgattung" number="">Graue Literatur</collection>
  </doc>
  <doc>
    <id>35586</id>
    <completedYear/>
    <publishedYear>2016</publishedYear>
    <thesisYearAccepted/>
    <language>eng</language>
    <pageFirst/>
    <pageLast/>
    <pageNumber/>
    <edition/>
    <issue/>
    <volume/>
    <type>lecture</type>
    <publisherName/>
    <publisherPlace/>
    <creatingCorporation/>
    <contributingCorporation/>
    <belongsToBibliography>0</belongsToBibliography>
    <completedDate>--</completedDate>
    <publishedDate>--</publishedDate>
    <thesisDateAccepted>--</thesisDateAccepted>
    <title language="eng">Spatial and temporal control of thermal waves by using DMDs for interference based crack detection</title>
    <abstract language="eng">Active Thermography is a well-established non-destructive testing method and used to detect cracks, voids or material inhomogeneities. It is based on applying thermal energy to a samples’ surface whereas inner defects alter the non-stationary heat flow. Conventional excitation of a sample is hereby done spatially, either planar (e.g. using a lamp) or local (e.g. using a focused laser) and temporally, either pulsed or periodical. In this work we combine a high power laser with a Digital Micromirror Device (DMD) allowing us to merge all degrees of freedom to a spatially and temporally controlled heat source. This enables us to exploit the possibilities of coherent thermal wave shaping. Exciting periodically while controlling at the same time phase and amplitude of the illumination source induces – via absorption at the sample’s surface - a defined thermal wave propagation through a sample. That means thermal waves can be controlled almost like acoustical or optical waves. However, in contrast to optical or acoustical waves, thermal waves are highly damped due to the diffusive character of the thermal heat flow and therefore limited in penetration depth in relation to the achievable resolution. Nevertheless, the coherence length of thermal waves can be chosen in the mm-range for modulation frequencies below 10 Hz which is perfectly met by DMD technology. This approach gives us the opportunity to transfer known technologies from wave shaping techniques to thermography methods. We will present experiments on spatial and temporal wave shaping, demonstrating interference based crack detection.</abstract>
    <enrichment key="eventName">Photonics West 2016, OPTO, 9761</enrichment>
    <enrichment key="eventPlace">San Francisco, Cal, USA</enrichment>
    <enrichment key="eventStart">15.02.2016</enrichment>
    <enrichment key="eventEnd">18.02.2016</enrichment>
    <enrichment key="InvitedTalks">0</enrichment>
    <author>Erik Thiel</author>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Thermal Waves</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Laser</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>DMD</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Active Thermography</value>
    </subject>
    <collection role="ddc" number="543">Analytische Chemie</collection>
    <collection role="fulltextaccess" number="">Datei im Netzwerk der BAM verfügbar ("Closed Access")</collection>
    <collection role="literaturgattung" number="">Präsentation</collection>
  </doc>
  <doc>
    <id>34291</id>
    <completedYear/>
    <publishedYear>2015</publishedYear>
    <thesisYearAccepted/>
    <language>deu</language>
    <pageFirst/>
    <pageLast/>
    <pageNumber/>
    <edition/>
    <issue/>
    <volume/>
    <type>lecture</type>
    <publisherName/>
    <publisherPlace/>
    <creatingCorporation/>
    <contributingCorporation/>
    <belongsToBibliography>0</belongsToBibliography>
    <completedDate>--</completedDate>
    <publishedDate>--</publishedDate>
    <thesisDateAccepted>--</thesisDateAccepted>
    <title language="deu">Wärmebehandlung und zerstörungsfreie Prüfung: Oberflächenrisse mit der Laser-Thermografie finden</title>
    <parentTitle language="deu">Institutskolloqium der TU Dresden am Institut für Oberflächen- und Fertigungstechnik IOF und Fraunhofer IWS</parentTitle>
    <identifier type="old">37420</identifier>
    <enrichment key="eventName">Institutskolloqium der TU Dresden am Institut für Oberflächen- und Fertigungstechnik IOF und Fraunhofer IWS</enrichment>
    <enrichment key="eventPlace">Dresden</enrichment>
    <enrichment key="eventStart">2015-03-23</enrichment>
    <enrichment key="eventEnd">2015-03-23</enrichment>
    <enrichment key="InvitedTalks">0</enrichment>
    <author>Erik Thiel</author>
    <collection role="fulltextaccess" number="">Weder Datei noch physisches Exemplar vorhanden ("No Access")</collection>
    <collection role="literaturgattung" number="">Präsentation</collection>
  </doc>
  <doc>
    <id>34625</id>
    <completedYear/>
    <publishedYear>2015</publishedYear>
    <thesisYearAccepted/>
    <language>deu</language>
    <pageFirst/>
    <pageLast/>
    <pageNumber/>
    <edition/>
    <issue/>
    <volume/>
    <type>lecture</type>
    <publisherName/>
    <publisherPlace/>
    <creatingCorporation/>
    <contributingCorporation/>
    <belongsToBibliography>0</belongsToBibliography>
    <completedDate>--</completedDate>
    <publishedDate>--</publishedDate>
    <thesisDateAccepted>--</thesisDateAccepted>
    <title language="deu">Advanced thermographic testing using DLP Technology</title>
    <parentTitle language="deu">10th International Symposium on Emerging on Emerging and Idustrial DLP Technology Applications</parentTitle>
    <identifier type="old">37761</identifier>
    <enrichment key="eventName">10th International Symposium on Emerging on Emerging and Idustrial DLP Technology Applications</enrichment>
    <enrichment key="eventPlace">Mainz</enrichment>
    <enrichment key="eventStart">2015-10-07</enrichment>
    <enrichment key="eventEnd">2015-10-08</enrichment>
    <enrichment key="InvitedTalks">0</enrichment>
    <author>Erik Thiel</author>
    <collection role="fulltextaccess" number="">Weder Datei noch physisches Exemplar vorhanden ("No Access")</collection>
    <collection role="literaturgattung" number="">Präsentation</collection>
  </doc>
  <doc>
    <id>35247</id>
    <completedYear/>
    <publishedYear>2015</publishedYear>
    <thesisYearAccepted/>
    <language>eng</language>
    <pageFirst>29</pageFirst>
    <pageLast>42</pageLast>
    <pageNumber/>
    <edition/>
    <issue>5</issue>
    <volume>10</volume>
    <type>article</type>
    <publisherName>Wiley-VCH Verl.</publisherName>
    <publisherPlace>Weinheim</publisherPlace>
    <creatingCorporation/>
    <contributingCorporation/>
    <belongsToBibliography>0</belongsToBibliography>
    <completedDate>--</completedDate>
    <publishedDate>--</publishedDate>
    <thesisDateAccepted>--</thesisDateAccepted>
    <title language="eng">Wide-field two photon microscopy - transcending technology limitations</title>
    <abstract language="eng">Two Photon Microscopy (2PM) generates microscopic images out of depth of biological samples. Up to now the method is restricted by narrow limitations of the field of view, the imaging depth and the orientation of the image field. A new approach overcomes these boundaries and delivers high resolution images revealing very specific information on clinically and biologically relevant tissue and cell structures. The status of the 2PM technology is critically reviewed and the options are discussed. The advantages of the new approach demonstrated by excellent tissue images.</abstract>
    <parentTitle language="eng">Optik &amp; Photonik</parentTitle>
    <identifier type="doi">10.1002/opph.201500035</identifier>
    <identifier type="issn">1863-1460</identifier>
    <author>N. Döge</author>
    <author>Erik Thiel</author>
    <author>G. Seewald</author>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Two photon microscopy</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Cell imaging</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Tissue imaging</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Optical biopsy</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Immunology</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Oncology</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Cosmetics</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Collagen</value>
    </subject>
    <collection role="literaturgattung" number="">Verlagsliteratur</collection>
    <collection role="fulltextaccess" number="">Datei im Netzwerk der BAM verfügbar ("Closed Access")</collection>
  </doc>
  <doc>
    <id>36577</id>
    <completedYear/>
    <publishedYear>2016</publishedYear>
    <thesisYearAccepted/>
    <language>eng</language>
    <pageFirst/>
    <pageLast/>
    <pageNumber/>
    <edition/>
    <issue/>
    <volume/>
    <type>lecture</type>
    <publisherName/>
    <publisherPlace/>
    <creatingCorporation/>
    <contributingCorporation/>
    <belongsToBibliography>0</belongsToBibliography>
    <completedDate>--</completedDate>
    <publishedDate>--</publishedDate>
    <thesisDateAccepted>--</thesisDateAccepted>
    <title language="eng">Laser projected photothermal thermography for characterizing hidden defects</title>
    <abstract language="eng">For the last 20 years active thermography has developed into a standard method in non-destructive material testing. It has become possible to detect defects such as cracks, voids, or even material inhomogeneities. Until now, it is still difficult to quantify subsurface or hidden defects in size due to the diffusive nature of heat flow within a solid. Facing this issue, lockin thermography and other photothermal techniques have been established. They are based on exciting a sample periodically (e.g. with a halogen lamp), causing a controlled periodical heat flow and thereby representing strongly damped thermal waves. These techniques make use of interference and reflection of thermal waves which allow enhancing depth resolution.&#13;
So far, only the temporal component of the light source was modified to achieve a defined vertical heat flow – In contrast, we propose a novel technique in which we are able to control both: time and space. This technique enables us to exploit the possibilities of coherent thermal wave shaping. We achieve that by combining a spatial light modulator (SLM) with a high power laser. This approach allows us to launch a set of individually controlled and fully coherent high energy thermal waves into the sample volume. That means, we intentionally use wave propagation throughout the sample’s material in both - vertical and lateral direction.&#13;
As one possible application, we use a thermal waves’ interference effect of two phase shifted wave patterns to detect the position of hidden defects. The wave patterns are positioned with a certain distance and a 180° phase shift to each other creating an amplitude depletion zone right in the middle of the two patterns. When a defect is brought unsymmetrically into the depletion zone, the lateral heat flow is disturbed. If the sample is now moved through the depletion zone, a defect can be easily characterized. Exciting periodically while controlling simultaneously phase and amplitude enables us to have a defined thermal wave propagation throughout the sample which means thermal waves can be controlled almost like acoustical or optical waves. This offers the opportunity to transfer known technologies from wave shaping techniques to thermography methods.</abstract>
    <enrichment key="eventName">19th World Conference of Non-Destructive Testing 2016</enrichment>
    <enrichment key="eventPlace">München, Germany</enrichment>
    <enrichment key="eventStart">13.06.2016</enrichment>
    <enrichment key="eventEnd">17.06.2016</enrichment>
    <enrichment key="InvitedTalks">0</enrichment>
    <author>Erik Thiel</author>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Thermal waves</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>DMD</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Active thermography</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>SLM</value>
    </subject>
    <collection role="ddc" number="543">Analytische Chemie</collection>
    <collection role="fulltextaccess" number="">Datei im Netzwerk der BAM verfügbar ("Closed Access")</collection>
    <collection role="literaturgattung" number="">Präsentation</collection>
  </doc>
  <doc>
    <id>37952</id>
    <completedYear/>
    <publishedYear>2016</publishedYear>
    <thesisYearAccepted/>
    <language>eng</language>
    <pageFirst/>
    <pageLast/>
    <pageNumber/>
    <edition/>
    <issue/>
    <volume/>
    <type>poster</type>
    <publisherName/>
    <publisherPlace/>
    <creatingCorporation/>
    <contributingCorporation/>
    <belongsToBibliography>0</belongsToBibliography>
    <completedDate>--</completedDate>
    <publishedDate>--</publishedDate>
    <thesisDateAccepted>--</thesisDateAccepted>
    <title language="eng">The VCSEL-Array - a Novel High-Power Light Source for (Photo) Thermal Imaging</title>
    <abstract language="eng">Within the field of optically excited thermography, full-field thermal imaging is used to characterize materials, to determine thicknesses of layers or to find inhomogeneities such as voids or cracks. Classical light sources, such as flash lamps (impulse heating) or halogen lamps (modulated heating), are hereby specifically used. This has led to the different testing methods lock-in and flash thermography. The VCSEL array promises to merge these excitation methods. &#13;
Vertical Cavity Surface Emitting Lasers (VCSELs) are laser diodes emitting light perpendicular to their surface. Due to the vertical structure they can be arranged in large arrays of many thousand individual lasers and still be controlled like ordinary diode lasers. Recently a high-power albeit very compact version of such a VCSEL-array became available which offers both the fast timing behavior of lasers and large illumination areas. Moreover, it allows a spatial and temporal control of the heating because individual parts of the VCSEL-array can be controlled arbitrarily in frequency, amplitude, and phase.&#13;
Although the VCSEL-array has a high potential for a new range of applications, it is too early to proclaim them. As one out of very few labs, we already adopted to this new VCSEL technology and show a thorough characterization and first results obtained with a 2.4 kW device. Specifically, we will discuss &#13;
- the linearity between control voltage and optical output&#13;
- the minimal pulse duration&#13;
- the maximal applicable modulation frequency&#13;
- optical projection and its influence on the optical output&#13;
- spatial control of the illumination and thermal wave shaping&#13;
Our results indicate that a VCSEL-array can be used for conventional impulse (aka flash) thermography whereas pulse duration and power are instantaneously accessible compared to flash lamp excitation. In case of lock-in thermography, we can apply frequencies in excess of 200 Hz without a loss in amplitude or an after glowing of the source, making it attractive for photo thermal applications. Consequently, this means that the VCSEL-array is able to merge the two main excitation methods lock-in and impulse thermography.</abstract>
    <enrichment key="eventName">57th Course on Photoacoustic &amp; Photothermal Phenomena</enrichment>
    <enrichment key="eventPlace">Erice, Italy</enrichment>
    <enrichment key="eventStart">19.10.2016</enrichment>
    <enrichment key="eventEnd">26.10.2016</enrichment>
    <author>Erik Thiel</author>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>VCSEL</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Thermal Wave</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Active Thermography</value>
    </subject>
    <collection role="ddc" number="543">Analytische Chemie</collection>
    <collection role="fulltextaccess" number="">Datei im Netzwerk der BAM verfügbar ("Closed Access")</collection>
    <collection role="literaturgattung" number="">Präsentation</collection>
  </doc>
  <doc>
    <id>37954</id>
    <completedYear/>
    <publishedYear>2016</publishedYear>
    <thesisYearAccepted/>
    <language>eng</language>
    <pageFirst/>
    <pageLast/>
    <pageNumber/>
    <edition/>
    <issue/>
    <volume/>
    <type>lecture</type>
    <publisherName/>
    <publisherPlace/>
    <creatingCorporation/>
    <contributingCorporation/>
    <belongsToBibliography>0</belongsToBibliography>
    <completedDate>--</completedDate>
    <publishedDate>--</publishedDate>
    <thesisDateAccepted>--</thesisDateAccepted>
    <title language="eng">Spatial and temporal control of thermal waves using spatial light modulators</title>
    <abstract language="eng">Active thermography has been developed into a well-established non-destructive testing method and is used to detect cracks, voids, or material properties. The spatial-temporal structure of the external heating: spatially: planar (e.g., halogen lamp) or local (e.g., focused laser), and temporally: pulsed (e.g., flash lamp) or periodical (e.g., halogen lamp), has led to different testing modalities, as for instance flash and lock-in thermography. In this work, we combine a high-power laser with a spatial light modulator (SLM) allowing us to merge all degrees of freedom into a spatially and temporally controlled heat source. This approach allows us to launch a set of individually controlled and fully coherent high-energy thermal waves into the sample volume. As one possible application, we demonstrate the interference of two phase shifted thermal wave patterns in order to detect the position and depth of hidden defects, which is still a challenging task in thermographic and photothermal techniques. The patterns are positioned with a certain distance and a phase shift of pi to each other, creating an amplitude depletion zone that is centered between them. Now, when a defect is brought into the depletion zone, the destructive interference is disturbed and the defect can be recognized. This approach means that we intentionally exploit the vertical and lateral propagation directions of the thermal waves. In a more general view, controlling simultaneously control of phase and amplitude of a set of thermal waves enables us to have a defined propagation of the thermal wave field within the sample, which means that thermal waves can be controlled almost like acoustical or optical waves. However, in contrast to optical or acoustical waves, thermal waves are highly damped due to the diffusive character of the thermal heat flow and therefore limited in penetration depth in relation to the achievable spatial resolution. Nevertheless, the coherence length of thermal waves can be chosen in the mm-range for modulation frequencies below 10 Hz which is perfectly met by present SLM technology. Eventually, this offers the opportunity to transfer known technologies from wave shaping techniques to thermography methods and to exploit the possibilities of coherent thermal wave shaping.</abstract>
    <enrichment key="eventName">57th Course on Photoacoustic &amp; Photothermal Phenomena</enrichment>
    <enrichment key="eventPlace">Erice, Italy</enrichment>
    <enrichment key="eventStart">19.10.2016</enrichment>
    <enrichment key="InvitedTalks">0</enrichment>
    <author>Erik Thiel</author>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Infrared thermography</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Thermal Wave</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>DMD</value>
    </subject>
    <collection role="ddc" number="543">Analytische Chemie</collection>
    <collection role="fulltextaccess" number="">Datei im Netzwerk der BAM verfügbar ("Closed Access")</collection>
    <collection role="literaturgattung" number="">Präsentation</collection>
  </doc>
  <doc>
    <id>42835</id>
    <completedYear/>
    <publishedYear>2017</publishedYear>
    <thesisYearAccepted/>
    <language>eng</language>
    <pageFirst/>
    <pageLast/>
    <pageNumber/>
    <edition/>
    <issue/>
    <volume/>
    <type>poster</type>
    <publisherName/>
    <publisherPlace/>
    <creatingCorporation/>
    <contributingCorporation/>
    <belongsToBibliography>0</belongsToBibliography>
    <completedDate>--</completedDate>
    <publishedDate>--</publishedDate>
    <thesisDateAccepted>--</thesisDateAccepted>
    <title language="eng">Novel thermographic methods for non-destructive testing using structured illumination</title>
    <abstract language="eng">Photothermal imaging is commonly used for the characterization of material properties, the determination of layer thicknesses or the detection of inhomogeneities such as voids or cracks. For this purpose, the solid specimen is externally heated, e.g. by using a light source. The resulting transient heat flows interact with the inner structures of the specimen, which in turn is measured as a transient temperature distribution at the surface.&#13;
Novel array-shaped, high-power laser light sources allow to control the heating of the surface arbitrarily, both temporally and spatially. This enables us to shape the heat flows within the material in a very specific way. In a first application, we demonstrate how to apply destructively interfering thermal wave fields in order to detect subsurface defects with a very high sensitivity. A similar technique, although originating from a very different physical domain, is already in use for medical 3D imaging showing the high potential of this approach.</abstract>
    <enrichment key="eventName">Adlershofer For­schungs­forum 2017</enrichment>
    <enrichment key="eventPlace">Berlin, Germany</enrichment>
    <enrichment key="eventStart">10.11.2017</enrichment>
    <author>Erik Thiel</author>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Active thermography</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Photothermal</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Crack detection</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Thermal wave</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Structured heating</value>
    </subject>
    <collection role="ddc" number="543">Analytische Chemie</collection>
    <collection role="fulltextaccess" number="">Datei im Netzwerk der BAM verfügbar ("Closed Access")</collection>
    <collection role="literaturgattung" number="">Präsentation</collection>
  </doc>
  <doc>
    <id>45621</id>
    <completedYear/>
    <publishedYear>2018</publishedYear>
    <thesisYearAccepted/>
    <language>eng</language>
    <pageFirst/>
    <pageLast/>
    <pageNumber/>
    <edition/>
    <issue/>
    <volume/>
    <type>lecture</type>
    <publisherName/>
    <publisherPlace/>
    <creatingCorporation/>
    <contributingCorporation/>
    <belongsToBibliography>0</belongsToBibliography>
    <completedDate>--</completedDate>
    <publishedDate>--</publishedDate>
    <thesisDateAccepted>--</thesisDateAccepted>
    <title language="eng">Two-dimensional interference of photothermally generated moving thermal waves</title>
    <abstract language="eng">Structured illumination using high-power diode lasers generates a two-dimensional interference of thermal waves. In addition, the sources and the sample are moving relative to each other. Using different configurations, we investigate the validity of the temporal and spatial superposition principle of the heat diffusion equation for these cases both experimentally and by numerical-analytical modelling. Furthermore, we investigate the potential of this approach for non-destructive testing.</abstract>
    <enrichment key="eventName">14th Quantitative Infrared Thermography Conference</enrichment>
    <enrichment key="eventPlace">Berlin, Germany</enrichment>
    <enrichment key="eventStart">24.05.2018</enrichment>
    <enrichment key="eventEnd">29.05.2018</enrichment>
    <enrichment key="InvitedTalks">0</enrichment>
    <author>Erik Thiel</author>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Thermography</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Thermal Wave</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>VCSEL</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Laser</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Thermal diffusion</value>
    </subject>
    <collection role="ddc" number="543">Analytische Chemie</collection>
    <collection role="fulltextaccess" number="">Datei im Netzwerk der BAM verfügbar ("Closed Access")</collection>
    <collection role="literaturgattung" number="">Präsentation</collection>
  </doc>
  <doc>
    <id>45851</id>
    <completedYear/>
    <publishedYear>2018</publishedYear>
    <thesisYearAccepted/>
    <language>eng</language>
    <pageFirst/>
    <pageLast/>
    <pageNumber/>
    <edition/>
    <issue/>
    <volume/>
    <type>lecture</type>
    <publisherName/>
    <publisherPlace/>
    <creatingCorporation/>
    <contributingCorporation/>
    <belongsToBibliography>0</belongsToBibliography>
    <completedDate>--</completedDate>
    <publishedDate>--</publishedDate>
    <thesisDateAccepted>--</thesisDateAccepted>
    <title language="eng">Structured heating in active thermography by using laser arrays</title>
    <abstract language="eng">Lock-in- and flash thermography are standard methods in active thermography. They are widely used in industrial inspection tasks e.g. for the detection of delaminations, cracks or pores. The requirements for the light sources of these two methods are substantially different. While lock-in thermography requires sources that can be easily and above all fast modulated, the use of flash thermography requires sources that release a very high optical energy in the very short time.&#13;
By introducing high-power vertical cavity surface emitting lasers (VCSELs) arrays to the field of thermography a source is now available that covers these two areas. VCSEL arrays combine the fast temporal behavior of a diode laser with the high optical irradiance and the wide illumination range of flash lamps or LEDs and can thus potentially replace all conventional light sources of thermography.&#13;
However, the main advantage of this laser technology lies in the independent control of individual array areas. It is therefore possible to heat not only in terms of time, but also in terms of space. This new degree of freedom allows the development of new NDT methods. We demonstrate this approach using a test problem that can only be solved to a limited extent in active thermography, namely the detection of very thin, hidden defects in metallic materials that are aligned vertically to the surface. For this purpose, we generate destructively interfering thermal wave fields, which make it possible to detect defects within the range of the thermal wave field high sensitivity. This is done without pre-treatment of the surface and without using a reference area to depths beyond the usual thermographic rule of thumb.</abstract>
    <enrichment key="eventName">ConaEnd&amp;Iev 2018</enrichment>
    <enrichment key="eventPlace">Sao Paulo, Brazil</enrichment>
    <enrichment key="eventStart">27.08.2018</enrichment>
    <enrichment key="eventEnd">29.08.2018</enrichment>
    <enrichment key="InvitedTalks">0</enrichment>
    <author>Erik Thiel</author>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>VCSEL</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Active thermography</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Laser</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Structured heating</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Subsurface defects</value>
    </subject>
    <collection role="ddc" number="543">Analytische Chemie</collection>
    <collection role="fulltextaccess" number="">Datei im Netzwerk der BAM verfügbar ("Closed Access")</collection>
    <collection role="literaturgattung" number="">Präsentation</collection>
  </doc>
  <doc>
    <id>45446</id>
    <completedYear/>
    <publishedYear>2018</publishedYear>
    <thesisYearAccepted/>
    <language>eng</language>
    <pageFirst>ECNDT-0139-2018,1</pageFirst>
    <pageLast>7</pageLast>
    <pageNumber/>
    <edition/>
    <issue/>
    <volume/>
    <type>conferenceobject</type>
    <publisherName/>
    <publisherPlace/>
    <creatingCorporation/>
    <contributingCorporation/>
    <belongsToBibliography>0</belongsToBibliography>
    <completedDate>--</completedDate>
    <publishedDate>--</publishedDate>
    <thesisDateAccepted>--</thesisDateAccepted>
    <title language="eng">Lock-in Thermography using High-Power Laser Sources</title>
    <abstract language="eng">Optical lock-in thermography is a completely contactless and very sensitive NDT technique. As an optical source of energy, incandescent lamps are most commonly used because they are relatively inexpensive and offer high irradiances at the test specimen. However, they are strongly restricted by their low modulation bandwidth with a maximum modulation frequency of only about 1 Hz. The use of high-power kilowattclass laser sources, e.g. diode laser arrays, pushes this constraint beyond 100 Hz. This allows for the exploration of the near-surface region of metals and layer systems with better and more accurate penetration depth and depth resolution. Moreover, these lasers are virtually free of any additional thermal radiation that could interfere with the “true” thermal response emitted from the heated sample. In turn, they can be easily used in a one-sided test configuration. We present current activities with kilowatt-class highpower laser sources for advanced lock-in thermography and focus on the application of laser arrays that offer a very high irradiation strength over a large sample area beyond the mentioned advantages.</abstract>
    <parentTitle language="eng">Proceedings of the 12th European Conference on Non-destructive Testing 2018</parentTitle>
    <identifier type="isbn">978-91-639-6217-2</identifier>
    <identifier type="url">http://cdn.ecndt2018.com/wp-content/uploads/2018/05/ecndt-0139-2018.pdf</identifier>
    <identifier type="urn">urn:nbn:de:kobv:b43-454466</identifier>
    <enrichment key="eventName">12th European Conference on Non-destructive Testing</enrichment>
    <enrichment key="eventPlace">Gothenburg, Sweden</enrichment>
    <enrichment key="eventStart">11.06.2018</enrichment>
    <enrichment key="eventEnd">15.06.2018</enrichment>
    <licence>Creative Commons - CC BY-NC - Namensnennung - Nicht kommerziell 4.0 International</licence>
    <author>Mathias Ziegler</author>
    <author>Erik Thiel</author>
    <author>Samim Ahmadi</author>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Thermography</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Laser Thermography</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Lock-in Thermography</value>
    </subject>
    <collection role="fulltextaccess" number="">Datei für die Öffentlichkeit verfügbar ("Open Access")</collection>
    <collection role="literaturgattung" number="">Graue Literatur</collection>
    <collection role="unnumberedseries" number="">Wissenschaftliche Artikel der BAM</collection>
    <thesisPublisher>Bundesanstalt für Materialforschung und -prüfung (BAM)</thesisPublisher>
    <file>https://opus4.kobv.de/opus4-bam/files/45446/ecndt-0139-2018.pdf</file>
  </doc>
  <doc>
    <id>46630</id>
    <completedYear/>
    <publishedYear>2018</publishedYear>
    <thesisYearAccepted/>
    <language>deu</language>
    <pageFirst>296</pageFirst>
    <pageLast>303</pageLast>
    <pageNumber/>
    <edition/>
    <issue>6</issue>
    <volume>49</volume>
    <type>article</type>
    <publisherName>Wiley-VCH Verlag GmbH &amp; Co. KGaA</publisherName>
    <publisherPlace>Weinheim</publisherPlace>
    <creatingCorporation/>
    <contributingCorporation/>
    <belongsToBibliography>0</belongsToBibliography>
    <completedDate>--</completedDate>
    <publishedDate>--</publishedDate>
    <thesisDateAccepted>--</thesisDateAccepted>
    <title language="deu">Wenn die Wärme Wellen schlägt</title>
    <abstract language="deu">Mit Laserlicht kann man eine Materialoberfläche berührungslos und schnell moduliert aufheizen. Dabei entsteht eine stark gedämpfte Wärmewelle, die tief ins Material eindringen kann. Erzeugt und überlagert man solche thermischen Wellen auf kohärente Weise, dann kann man damit versteckte Materialfehler zerstörungsfrei und sehr präzise aufspüren. Sogar eine bildgebende Tomografie ist denkbar.</abstract>
    <parentTitle language="deu">Physik in unserer Zeit</parentTitle>
    <identifier type="doi">10.1002/piuz.201801512</identifier>
    <identifier type="issn">0031-9252</identifier>
    <author>Mathias Ziegler</author>
    <author>Erik Thiel</author>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Thermography</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Laser thermography</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Lock-in thermography</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>NDT</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Thermal waves</value>
    </subject>
    <collection role="ddc" number="543">Analytische Chemie</collection>
    <collection role="literaturgattung" number="">Verlagsliteratur</collection>
    <collection role="fulltextaccess" number="">Datei im Netzwerk der BAM verfügbar ("Closed Access")</collection>
  </doc>
  <doc>
    <id>41078</id>
    <completedYear/>
    <publishedYear>2017</publishedYear>
    <thesisYearAccepted/>
    <language>eng</language>
    <pageFirst/>
    <pageLast/>
    <pageNumber/>
    <edition/>
    <issue/>
    <volume/>
    <type>lecture</type>
    <publisherName/>
    <publisherPlace/>
    <creatingCorporation/>
    <contributingCorporation/>
    <belongsToBibliography>0</belongsToBibliography>
    <completedDate>--</completedDate>
    <publishedDate>--</publishedDate>
    <thesisDateAccepted>--</thesisDateAccepted>
    <title language="eng">Thermal Wave Interference with High-Power VCSEL Arrays For Locating Vertically Oriented Subsurface Defects</title>
    <abstract language="eng">Among the photothermal methods, full-field thermal imaging is used to characterize materials, to determine thicknesses of layers, or to find inhomogeneities such as voids or cracks. The use of classical light sources such as flash lamps (impulse heating) or halogen lamps (modulated heating) led to a variety of nondestructive testing methods, in particular lock-in and flash-thermography.&#13;
In vertical cavity surface emitting lasers (VCSELs), laser light is emitted perpendicular to the surface with a symmetrical beam profile. Due to the vertical structure, they can be arranged in large arrays of many thousands of individual lasers, which allows power scaling into the kilowatt range. Recently, a high-power yet very compact version of such a VCSEL-array became available that offers both the fast timing behavior of a laser as well as the large illumination area of a lamp. &#13;
Moreover, it allows a spatial and temporal control of the heating because individual parts of the array can be controlled arbitrarily in frequency, amplitude, and phase. In conjunction with a fast infrared camera, such structured heating opens up a field of novel thermal imaging and testing methods. As a first demonstration of this approach, we chose a testing problem very challenging to conventional thermal infrared testing: The detection of very thin subsurface defects perpendicularly oriented to the surface of metallic samples. First, we generate destructively interfering thermal wave fields which are then affected by the presence of defects within their reach. It turned out that this technique allows highly sensitive detection of subsurface defects down to depths in excess of the usual thermographic rule of thumb, with no need for a reference or surface preparation</abstract>
    <enrichment key="eventName">QNDE 2017</enrichment>
    <enrichment key="eventPlace">Provo, Utah, USA</enrichment>
    <enrichment key="eventStart">17.07.2017</enrichment>
    <enrichment key="eventEnd">20.07.2017</enrichment>
    <enrichment key="InvitedTalks">0</enrichment>
    <author>Erik Thiel</author>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Thermal Wave</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Photothermal</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Active Thermography</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>VCSEL</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Subsurface Defect</value>
    </subject>
    <collection role="ddc" number="543">Analytische Chemie</collection>
    <collection role="fulltextaccess" number="">Datei im Netzwerk der BAM verfügbar ("Closed Access")</collection>
    <collection role="literaturgattung" number="">Präsentation</collection>
  </doc>
  <doc>
    <id>45619</id>
    <completedYear/>
    <publishedYear>2018</publishedYear>
    <thesisYearAccepted/>
    <language>eng</language>
    <pageFirst/>
    <pageLast/>
    <pageNumber/>
    <edition/>
    <issue/>
    <volume/>
    <type>poster</type>
    <publisherName/>
    <publisherPlace/>
    <creatingCorporation/>
    <contributingCorporation/>
    <belongsToBibliography>0</belongsToBibliography>
    <completedDate>--</completedDate>
    <publishedDate>--</publishedDate>
    <thesisDateAccepted>--</thesisDateAccepted>
    <title language="eng">Crack detection in metal additive manufacturing with laser thermography</title>
    <abstract language="eng">BAM ensures and represents high standards for safety in technology and chemistry. Additive manufacturing (AM) changes the requirements for conventional non-destructive testing (NDT) as new processes of defect creation occur. Especially in safety critical areas, such as aerospace and automotive, new manufacturing processes and materials always require reliability tests and new standards which is a big challenge for NDT.</abstract>
    <enrichment key="eventName">Internationales Laser- und Fügesymposium</enrichment>
    <enrichment key="eventPlace">Dresden, Germany</enrichment>
    <enrichment key="eventStart">27.02.2018</enrichment>
    <enrichment key="eventEnd">28.02.2018</enrichment>
    <author>Erik Thiel</author>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Laser Beam Melting</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Laser Metal Deposition</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Thermography</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>In-situ monitoring</value>
    </subject>
    <collection role="ddc" number="620">Ingenieurwissenschaften und zugeordnete Tätigkeiten</collection>
    <collection role="fulltextaccess" number="">Datei im Netzwerk der BAM verfügbar ("Closed Access")</collection>
    <collection role="literaturgattung" number="">Präsentation</collection>
  </doc>
  <doc>
    <id>46072</id>
    <completedYear/>
    <publishedYear>2018</publishedYear>
    <thesisYearAccepted/>
    <language>eng</language>
    <pageFirst/>
    <pageLast/>
    <pageNumber/>
    <edition/>
    <issue/>
    <volume/>
    <type>lecture</type>
    <publisherName/>
    <publisherPlace/>
    <creatingCorporation/>
    <contributingCorporation/>
    <belongsToBibliography>0</belongsToBibliography>
    <completedDate>--</completedDate>
    <publishedDate>--</publishedDate>
    <thesisDateAccepted>--</thesisDateAccepted>
    <title language="eng">Quality control in additive manufacturing via in-situ monitoring and non-destructive testing</title>
    <abstract language="eng">More than 80 representatives of SMEs, industrial companies and research institutes met on September 12 at the workshop "Challenges in Additive Manufacturing: Innovative Materials and Quality Control" at BAM in Adlershof to discuss the latest developments in materials and quality control in additive manufacturing. &#13;
&#13;
In special lectures, researchers, users and equipment manufacturers reported on the latest and future developments in additive manufacturing. Furthermore, funding opportunities for projects between SMEs and research institutions on a national and European level were presented.</abstract>
    <enrichment key="eventName">Challenges in Additive Manufacturing: Innovative Materials and Quality Control</enrichment>
    <enrichment key="eventPlace">Berlin, Germany</enrichment>
    <enrichment key="eventStart">12.09.2018</enrichment>
    <enrichment key="eventEnd">12.09.2018</enrichment>
    <enrichment key="InvitedTalks">0</enrichment>
    <author>Christiane Maierhofer</author>
    <author>Erik Thiel</author>
    <author>Simon Altenburg</author>
    <author>Gunther Mohr</author>
    <author>Tobias Thiede</author>
    <author>Tatiana Mishurova</author>
    <author>Andrea Paul</author>
    <author>Axel Kranzmann</author>
    <author>Kai Hilgenberg</author>
    <author>Andreas Pittner</author>
    <author>Giovanni Bruno</author>
    <author>Konstantin Sommer</author>
    <author>Andrey Gumenyuk</author>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Additive manufacturing</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Quality control</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Non-destructive testing</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>In-situ monitoring</value>
    </subject>
    <collection role="ddc" number="543">Analytische Chemie</collection>
    <collection role="fulltextaccess" number="">Datei im Netzwerk der BAM verfügbar ("Closed Access")</collection>
    <collection role="literaturgattung" number="">Präsentation</collection>
  </doc>
  <doc>
    <id>50924</id>
    <completedYear/>
    <publishedYear>2019</publishedYear>
    <thesisYearAccepted/>
    <language>eng</language>
    <pageFirst>Paper 8593, 1</pageFirst>
    <pageLast/>
    <pageNumber/>
    <edition/>
    <issue/>
    <volume/>
    <type>conferenceobject</type>
    <publisherName>ASME</publisherName>
    <publisherPlace/>
    <creatingCorporation/>
    <contributingCorporation/>
    <belongsToBibliography>0</belongsToBibliography>
    <completedDate>--</completedDate>
    <publishedDate>--</publishedDate>
    <thesisDateAccepted>--</thesisDateAccepted>
    <title language="eng">Photothermal super resolution image reconstruction using structured 1D laser illumination</title>
    <abstract language="eng">The separation of two closely spaced defects in fields of Thermographic NDE is very challenging. The diffusive nature of thermal waves leads to a fundamental limitation in spatial resolution. Therefore, super resolution image reconstruction can be used. A new concerted ansatz based on spatially structured heating and joint sparsity of the signal ensemble allows for an improved reconstruction of closely spaced defects. This new technique has been studied using a 1D laser array with randomly chosen illumination pattern.&#13;
This paper presents the results after applying super resolution algorithms, such as the iterative joint sparsity (IJOSP) algorithm, to our processed measurement data. Different data processing techniques before applying the IJOSP algorithm as well as the influence of regularization parameters in the data processing techniques are discussed. Moreover, the degradation of super resolution reconstruction goodness by the choice of experimental parameters such as laser line width or number of measurements is shown.&#13;
The application of the super resolution results in a spatial resolution enhancement of approximately a factor of four which leads to a better separation of two closely spaced defects.</abstract>
    <parentTitle language="eng">Review of Progress in Quantitative Nondestructive Evaluation</parentTitle>
    <enrichment key="eventName">Quantitative Nondestructive Evaluation Conference 2019</enrichment>
    <enrichment key="eventPlace">Portland, OR, USA</enrichment>
    <enrichment key="eventStart">14.07.2019</enrichment>
    <enrichment key="opus.doi.autoCreate">false</enrichment>
    <enrichment key="opus.urn.autoCreate">true</enrichment>
    <author>Samim Ahmadi</author>
    <author>Erik Thiel</author>
    <author>Christina Karagianni</author>
    <author>Philipp Daniel Hirsch</author>
    <author>P. Burgholzer</author>
    <author>G. Mayr</author>
    <author>P. Jung</author>
    <author>G. Caire</author>
    <author>Mathias Ziegler</author>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Super resolution</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Photothermal</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Thermography</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Laser</value>
    </subject>
    <collection role="ddc" number="543">Analytische Chemie</collection>
    <collection role="fulltextaccess" number="">Datei im Netzwerk der BAM verfügbar ("Closed Access")</collection>
    <collection role="literaturgattung" number="">Graue Literatur</collection>
  </doc>
  <doc>
    <id>45620</id>
    <completedYear/>
    <publishedYear>2018</publishedYear>
    <thesisYearAccepted/>
    <language>eng</language>
    <pageFirst/>
    <pageLast/>
    <pageNumber/>
    <edition/>
    <issue/>
    <volume/>
    <type>lecture</type>
    <publisherName/>
    <publisherPlace/>
    <creatingCorporation/>
    <contributingCorporation/>
    <belongsToBibliography>0</belongsToBibliography>
    <completedDate>--</completedDate>
    <publishedDate>--</publishedDate>
    <thesisDateAccepted>--</thesisDateAccepted>
    <title language="eng">AM activities at BAM with focus on process monitoring</title>
    <abstract language="eng">The presentation gives an overview of current projects in additive manufacturing at BAM. In particular, the results of the ProMoAm project were presented.</abstract>
    <enrichment key="eventName">VAMAS - Materials Issues in Additive Manufacturing</enrichment>
    <enrichment key="eventPlace">Berlin, Germany</enrichment>
    <enrichment key="eventStart">25.06.2018</enrichment>
    <enrichment key="eventEnd">26.06.2018</enrichment>
    <enrichment key="InvitedTalks">0</enrichment>
    <author>Erik Thiel</author>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Additive Manufacturing</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Laser Metal Deposition</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Thermography</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Data Fusion</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>In-situ monitoring</value>
    </subject>
    <collection role="ddc" number="620">Ingenieurwissenschaften und zugeordnete Tätigkeiten</collection>
    <collection role="fulltextaccess" number="">Datei im Netzwerk der BAM verfügbar ("Closed Access")</collection>
    <collection role="literaturgattung" number="">Präsentation</collection>
  </doc>
  <doc>
    <id>36570</id>
    <completedYear/>
    <publishedYear>2016</publishedYear>
    <thesisYearAccepted/>
    <language>eng</language>
    <pageFirst>Th.4.I.2 - 1</pageFirst>
    <pageLast>Th.4.I.2 - 6</pageLast>
    <pageNumber/>
    <edition/>
    <issue/>
    <volume/>
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    <publisherName/>
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    <contributingCorporation/>
    <belongsToBibliography>0</belongsToBibliography>
    <completedDate>--</completedDate>
    <publishedDate>--</publishedDate>
    <thesisDateAccepted>--</thesisDateAccepted>
    <title language="eng">Laser projected photothermal thermography for characterizing hidden defects</title>
    <abstract language="eng">For the last 20 years active thermography has developed into a standard method in non-destructive material testing. It has become possible to detect defects such as cracks, voids, or even material inhomogeneities. Until now, it is still difficult to quantify subsurface or hidden defects in size due to the diffusive nature of heat flow within a solid. Facing this issue, lockin thermography and other photothermal techniques have been established. They are based on exciting a sample periodically (e.g. with a halogen lamp), causing a controlled periodical heat flow and thereby representing strongly damped thermal waves. These techniques make use of interference and reflection of thermal waves which allow enhancing depth resolution.&#13;
So far, only the temporal component of the light source was modified to achieve a defined vertical heat flow – In contrast, we propose a novel technique in which we are able to control both: time and space. This technique enables us to exploit the possibilities of coherent thermal wave shaping. We achieve that by combining a spatial light modulator (SLM) with a high power laser. This approach allows us to launch a set of individually controlled and fully coherent high energy thermal waves into the sample volume. That means, we intentionally use wave propagation throughout the sample’s material in both - vertical and lateral direction. As one possible application, we use a thermal waves’ interference effect of two phase shifted wave patterns to detect the position of hidden defects. The wave patterns are positioned with a certain distance and a 180° phase shift to each other creating an amplitude depletion zone right in the middle of the two patterns. When a defect is brought unsymmetrically into the depletion zone, the lateral heat flow is disturbed. If the sample is now moved through the depletion zone, a defect can be easily characterized. Exciting periodically while controlling simultaneously phase and amplitude enables us to have a defined thermal wave propagation throughout the sample which means thermal waves can be controlled almost like acoustical or optical waves. This offers the opportunity to transfer known technologies from wave shaping techniques to thermography methods.</abstract>
    <parentTitle language="eng">WCNDT 2016 Proceedings</parentTitle>
    <identifier type="urn">urn:nbn:de:kobv:b43-365702</identifier>
    <enrichment key="eventName">19th World Conference of Non-Destructive Testing 2016</enrichment>
    <enrichment key="eventPlace">München, Germany</enrichment>
    <enrichment key="eventStart">13.06.2016</enrichment>
    <enrichment key="eventEnd">17.06.2016</enrichment>
    <licence>Creative Commons - Namensnennung - Keine Bearbeitung 3.0</licence>
    <author>Erik Thiel</author>
    <author>M. Kreutzbruck</author>
    <author>Mathias Ziegler</author>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Thermal waves</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>DMD</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Active thermography</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>SLM</value>
    </subject>
    <collection role="ddc" number="543">Analytische Chemie</collection>
    <collection role="fulltextaccess" number="">Datei für die Öffentlichkeit verfügbar ("Open Access")</collection>
    <collection role="literaturgattung" number="">Graue Literatur</collection>
    <thesisPublisher>Bundesanstalt für Materialforschung und -prüfung (BAM)</thesisPublisher>
    <file>https://opus4.kobv.de/opus4-bam/files/36570/Thiel_et_al - Laser projected photothermal thermography for characterizing hidden defects.pdf</file>
  </doc>
  <doc>
    <id>43117</id>
    <completedYear/>
    <publishedYear>2017</publishedYear>
    <thesisYearAccepted/>
    <language>deu</language>
    <pageFirst>1</pageFirst>
    <pageLast>15</pageLast>
    <pageNumber/>
    <edition/>
    <issue/>
    <volume>163</volume>
    <type>conferenceobject</type>
    <publisherName>Deutsche Gesellschaft für Zerstörungsfreie Prüfung (DGZfP)</publisherName>
    <publisherPlace>Berlin</publisherPlace>
    <creatingCorporation/>
    <contributingCorporation/>
    <belongsToBibliography>0</belongsToBibliography>
    <completedDate>--</completedDate>
    <publishedDate>--</publishedDate>
    <thesisDateAccepted>--</thesisDateAccepted>
    <title language="deu">Laser-Thermografie – Von der flächigen zur  strukturierten Anregung</title>
    <abstract language="deu">Im Bereich der optisch angeregten Thermografie haben sich Blitzlampen (impulsförmig-flächige Erwärmung) und Halogenlampen (moduliert-flächige Erwärmung) für die spezifischen Regime Impuls- und Lockin-Thermografie etabliert.&#13;
Mittels eines rasternden fokussierten Lasers wird die Flying-spot Laserthermografie z.B. zur Risserkennung (Dauerstrichbetrieb) und die photothermische Materialcharakterisierung (hochfrequent  moduliert)implementiert. Durch die Verfügbarkeit neuer Technologien (schnelle und hochauflösende IR-Kameras, brillante innovativer Lichtquellen und performante Datenakquisitions- und Verarbeitungstechnik) wird ein Paradigmenwechsel von den getrennt voneinander stehenden photothermischen und &#13;
thermografischen Techniken hin zu einer einheitlichen quantitativen Mess-und Prüftechnik ermöglicht, die schneller und präziser ist. Ähnlich wie ein LED-Array, jedoch mit einer um zwei Größenordnungen höheren Bestrahlungsstärke, steht jetzt eine neuartige brillante Laserquelle, das VCSEL-Array (vertical-cavity surface-emitting laser) zur Verfügung, welches die starke Beschränkung der zeitlichen Dynamik der etablierten Lichtquellen aufhebt und gleichzeitig spektral sauber von der Detektionswellenlänge getrennt ist. Es vereint somit das schnelle zeitliche Verhalten eines Diodenlasers mit der hohen optischen Bestrahlungsstärke und dem großen Beleuchtungsbereich von Blitzlampen. Darüber hinaus kann die Erwärmung auch strukturiert vorgenommen werden, da einzelne Bereiche des VCSEL-Arrays unabhängig voneinander angesteuert werden können. Dieser neue Freiheitsgrad ermöglicht die Entwicklung ganz neuer thermografischer ZfP-Verfahren.</abstract>
    <parentTitle language="deu">DGZfP-Berichtsband</parentTitle>
    <identifier type="isbn">978-3-940283-88-7</identifier>
    <identifier type="url">https://www.dgzfp.de/Portals/thermo2017/BB/6.pdf</identifier>
    <identifier type="urn">urn:nbn:de:kobv:b43-431170</identifier>
    <enrichment key="eventName">Thermographie-Kolloquium 2017</enrichment>
    <enrichment key="eventPlace">Berlin, Germany</enrichment>
    <enrichment key="eventStart">28.09.2017</enrichment>
    <enrichment key="eventEnd">29.09.2017</enrichment>
    <licence>Creative Commons - Namensnennung - Keine Bearbeitung 3.0</licence>
    <author>Mathias Ziegler</author>
    <author>Erik Thiel</author>
    <author>Taarna Studemund</author>
    <subject>
      <language>deu</language>
      <type>uncontrolled</type>
      <value>Thermografie</value>
    </subject>
    <subject>
      <language>deu</language>
      <type>uncontrolled</type>
      <value>Laser</value>
    </subject>
    <subject>
      <language>deu</language>
      <type>uncontrolled</type>
      <value>Zerstörungsfreie Prüfung</value>
    </subject>
    <subject>
      <language>deu</language>
      <type>uncontrolled</type>
      <value>Lock-in</value>
    </subject>
    <subject>
      <language>deu</language>
      <type>uncontrolled</type>
      <value>VCSEL</value>
    </subject>
    <subject>
      <language>deu</language>
      <type>uncontrolled</type>
      <value>Photothermisch</value>
    </subject>
    <collection role="ddc" number="543">Analytische Chemie</collection>
    <collection role="ddc" number="620">Ingenieurwissenschaften und zugeordnete Tätigkeiten</collection>
    <collection role="fulltextaccess" number="">Datei für die Öffentlichkeit verfügbar ("Open Access")</collection>
    <collection role="literaturgattung" number="">Graue Literatur</collection>
    <collection role="unnumberedseries" number="">Wissenschaftliche Artikel der BAM</collection>
    <thesisPublisher>Bundesanstalt für Materialforschung und -prüfung (BAM)</thesisPublisher>
    <file>https://opus4.kobv.de/opus4-bam/files/43117/6_Ziegler final.pdf</file>
  </doc>
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