Complementary use of active infrared thermography and optical coherent tomography in non-destructive testing inspection of ancient marquetries

Imaging-based inspection techniques have practical advantages in the study and/or rehabilitation of artworks. They provide in some cases internal information on the status of the sample to be inspected. On the one hand, techniques based on active infrared thermography (IRT) are advantageous to obtaining complete images of the inspected parts, although a technical interpretation performed by a team of experts in non-destructive testing (NDT) techniques is needed above all when the target is composed, as in our case, by different materials. On the other hand, optical coherence tomography (OCT) is slow when inspecting complete parts, but it has great level of structural detail in subsurface measurements up to 3 mm. The complementary use of these two techniques, and its application to a very ancient marquetry sample with an unusual tessellatum layer, is presented herein. The plan size of the sample is 208×212 mm, while the tessellatum is 1.5 mm thick. Starting from thermal imaging inspections, using step-heating (SH) and pulsed thermography (PT), a defect map has been defined. Structural details of these defects using OCT will help the restorer in charge of the restoration process to perform a satisfactory work. This work was supported in part by the Spanish Economy and Competitiveness Minister under Project TEC2016-76021-C2-2-R; Jose Castillejo Grant (CAS17/00216) by the Spanish Minister of Education, Culture and Sports and Cantabria government postdoc Grant PS-UC-2018-16.