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Super-resolution thermography as a tool for investigating the conservation state of cultural heritage artifacts.

Collini M., Bouzin M., Marini M., Sironi L., D'Alfonso L., Colombo R., Di Martino D., Gorini G., Chirico G.
  Giovedì 15/09   09:00 - 13:00   Aula L - Christa Mc Auliffe   VI - Fisica applicata, acceleratori e beni culturali   Presentazione
The non-destructive characterization with $40 \mu m$ resolution on mesoscopic scale is a demanding need in the field of cultural heritage conservation. We present here a novel methodology to obtain space-resolved maps of the product of the thermal conductivity times the sample thickness that can be applied to solid opaque samples (oxidized metals, pigments on different substrates, wood, clay, etc.). By localizing the temperature increments sparsely induced on the sample by a focalized laser beam, the thermal conductivity of the material can be obtained once the thickness and the absorbed power are known. This method has been applied to an XVIII century organ pipe fragment. The tin foil shows evidence of oxidation processes (tin-pest). Our analysis, developed on finite elements simulations covering a wide range of conductivity values ({0.1\mbox$--$100 ${W/mK}$), shows the possibility of correlating regions of different conductivity and thickness of the sample to its conservation state on $ {mm}^{2}$ areas with a sub-diffraction $40 \mu m$ resolution. Our approach expands the capability of state-of-the-art infrared imaging in capturing the heterogeneity and functional state of the imaged materials.