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Spatial and temporal control of thermal waves by using DMDs for interference based crack detection

  • 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 nonstationary 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, inActive 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 nonstationary 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 mmrange 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.zeige mehrzeige weniger

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  • 2016-03-15 Spatial and temporal control of thermal waves by using DMDs for interference based crack detection EThiel.pdf
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Autor*innen:Erik Thiel, M. Kreutzbruck, Mathias ZieglerORCiD
Dokumenttyp:Beitrag zu einem Tagungsband
Veröffentlichungsform:Graue Literatur
Sprache:Englisch
Titel des übergeordneten Werkes (Englisch):Emerging Digital Micromirror Device Based Systems and Applications VIII, Proc. of SPIE
Jahr der Erstveröffentlichung:2016
Herausgeber (Institution):SPIE
Jahrgang/Band:9761
Erste Seite:97610N-1
Letzte Seite:97610N-13
DDC-Klassifikation:Naturwissenschaften und Mathematik / Chemie / Analytische Chemie
Freie Schlagwörter:Active thermography; Crack detection; DMD; DMD coupled laser; Spatial light modulation; Thermal wave
Veranstaltung:Photonics West 2016, OPTO, 9761
Veranstaltungsort:San Francisco, CA, USA
Beginndatum der Veranstaltung:15.02.2016
Enddatum der Veranstaltung:18.02.2016
DOI:10.1117/12.2210918
ISSN:0277-786X
Verfügbarkeit des Dokuments:Datei im Netzwerk der BAM verfügbar ("Closed Access")
Datum der Freischaltung:29.03.2016
Referierte Publikation:Ja
Datum der Eintragung als referierte Publikation:10.11.2016
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