Overcoming the Spatial Resolution Limits imposed by the Thermal MTF with Thermographic Photothermal Super Resolution Reconstruction
- The achievable spatial resolution of active thermographic testing is inherently limited by the diffusive nature of heat conduction in solids. This degradation of the achievable spatial resolution for a semi-infinite body acting on a defect signal can be approximated by spatial convolution with the Greenâs function of the heat PDE. As the degradation in spatial resolution is dependent on the depth đż, a common rule of thumb specifies that for proper detection, any defect should feature a spatial extension greater or equal to the depth it is located at. However, as the exact shape of a defect can have a large impact on its severity, at best a proper reconstruction of the defect shape should be performed, which therefore must also deal with the aforementioned adverse effects of heat conduction. One recent method to overcome the spatial resolution limit of thermographic testing is the photothermal super resolution reconstruction method. It is based on performing multiple activeThe achievable spatial resolution of active thermographic testing is inherently limited by the diffusive nature of heat conduction in solids. This degradation of the achievable spatial resolution for a semi-infinite body acting on a defect signal can be approximated by spatial convolution with the Greenâs function of the heat PDE. As the degradation in spatial resolution is dependent on the depth đż, a common rule of thumb specifies that for proper detection, any defect should feature a spatial extension greater or equal to the depth it is located at. However, as the exact shape of a defect can have a large impact on its severity, at best a proper reconstruction of the defect shape should be performed, which therefore must also deal with the aforementioned adverse effects of heat conduction. One recent method to overcome the spatial resolution limit of thermographic testing is the photothermal super resolution reconstruction method. It is based on performing multiple active thermographic measurements on the same region of interest (ROI) with varying spatially structured heating and subsequent numerical reconstruction of the measured defect signals by solving a severely ill-posed inverse reconstruction problem relying on heavy regularization. By extending the experimental implementation of the method to make use of random-pixel patterns projected onto the ROI using a laser-coupled DLP-projector, defect reconstructions can now be performed within a reasonable time frame (~15 min per ROI) at high accuracy. Compared to conventional thermographic testing methods, the photothermal super resolution reconstruction stands out by resulting in a sparse representation of the defect structure of the ROI, making it especially well-suited to further automatic defect classification and quality assurance measures in an Industry 4.0 context.âŠ
Autor*innen: | Julien LecompagnonORCiD |
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Koautor*innen: | Philipp Daniel Hirsch, C. Rupprecht, Mathias Ziegler |
Dokumenttyp: | Vortrag |
Veröffentlichungsform: | PrÀsentation |
Sprache: | Englisch |
Jahr der Erstveröffentlichung: | 2023 |
Organisationseinheit der BAM: | 8 Zerstörungsfreie PrĂŒfung |
8 Zerstörungsfreie PrĂŒfung / 8.0 Abteilungsleitung und andere | |
DDC-Klassifikation: | Naturwissenschaften und Mathematik / Chemie / Analytische Chemie |
Freie Schlagwörter: | DLP; Internal defects; NDT; Super resolution; Thermography |
Themenfelder/AktivitÀtsfelder der BAM: | Chemie und Prozesstechnik |
Veranstaltung: | INTERNATIONAL SCHOOL OF QUANTUM ELECTRONICS: 67th Course: Progress in Photoacoustic & Photothermal Phenomena |
Veranstaltungsort: | Erice, Italy |
Beginndatum der Veranstaltung: | 24.09.2023 |
Enddatum der Veranstaltung: | 01.10.2023 |
VerfĂŒgbarkeit des Dokuments: | Datei im Netzwerk der BAM verfĂŒgbar ("Closed Access") |
Datum der Freischaltung: | 04.10.2023 |
Referierte Publikation: | Nein |
Eingeladener Vortrag: | Nein |