Photothermal image reconstruction in opaque media with virtual wave backpropagation

G. Thummerer, G. Mayr, P. D. Hirsch, M. Ziegler, P. Burgholzer

Research output: Contribution to journalArticlepeer-review

13 Citations (Scopus)


Thermographic reconstruction of defects that lie in the bulk of a sample is a difficult task because entropy production during heat diffusion leads to information loss. To reconstruct defects one has to solve an inverse heat conduction problem. The quality of the reconstruction is closely related to the information content of the observed data set that is reflected by the decreasing ability to spatially resolve a defect with growing defect depth. In this work we show a 2D reconstruction of rectangular slots with different width-to-depth ratios in a metallic sample. For this purpose, we apply the virtual wave concept and incorporate positivity and sparsity as prior information to overcome the diffusion-based information loss partially. The reconstruction is based on simulated and experimental pulse thermography data. In the first reconstruction step, we compute a virtual wave field from the surface temperature data. This allows us, in the second step, to use ultrasonic backpropagation methods for image reconstruction.

Original languageEnglish
Article number102239
JournalNDT and E International
Publication statusPublished - Jun 2020


  • Image reconstruction
  • Photothermal Technique
  • Thermography
  • Virtual wave concept


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