Non-destructive imaging of ancient marquetries using active thermography and photothermal coherence tomography

Abstract Active thermography has proven successful for non-destructive evaluation of art objects. The aim of this work was to detect the defects of a genuine ancient marquetry sample with both enhanced truncated correlation photothermal coherence tomography (eTC-PCT) and the well-known lock-in thermography (LIT) and compare the two modalities. Quantitative analysis of eTC-PCT images for depth measurements was also performed. Both methods revealed worn-off and glue starved areas, cracks and detachments in the sample, all of which are common defects of these types of art objects. In comparison, the eTC-PCT method was proven to be able to provide 3D images of the interrogated sample and more information about deep sub-surface defects with better contrast than LIT. Moreover, the eTC-PCT results of the marquetry sample containing natural defects were analyzed to determine the location of defects, a task that is not possible with LIT. The experiments showed that both methods are safe for non-destructive evaluation of art samples with temperature rise of less than 0.8 °C using eTC-PCT, and less than 1.5 °C using the LIT method.