Complementary Use of Active Infrared Thermography and Optical Coherent Tomography in Non-destructive Testing Inspection of Ancient Marquetries

Abstract

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 3mm.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 x 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.

The use of optical coherence tomography for skin evaluation in healthy rats

“…The measurements of skin thickness were taken manually with the use of a caliper function integrated into the Topcon 3D SD‐OCT‐2000 software. The epidermis was measured using the greyscale projection and the dermis with the commonly used SD‐OCT false colour projection, in which cold colours correspond to low and warm colours to high scatter/reflection of the light 23 . Each of the observed layers differing in signal intensity was measured three times in three different places on the image at a distance of 300 μm, and the mean of these measurements was used for further analysis.…”

Active Thermography in Diagnostics of Timber Elements Covered with Polychrome

“…In the field of timber investigations, thermography has been applied to determine the technical condition of wood and growing trees, especially through detection of deteriorations and voids that compromise its structure, stability and durability [ 27 ]. In the literature, the most commonly discussed is the implementation of thermal imaging to determine the density of timber [ 23 , 28 ], the location of defects on prepared samples [ 29 ] or historical samples [ 30 , 31 , 32 ] and the determination of moisture using such technique [ 33 ]. A separate issue presented in the literature is the determination of emissivity for different wood species [ 34 ].…”

“…In general, the moisture difference visible in passive thermography images is related to the excessive moisture in fragments of the elements, e.g., the support zones of beams. In the literature, there are examples of its application both for determining the location of natural defects of wood such as cracks or knots under the primer coating [ 30 , 31 ] and for the detection of defects within the paint coating [ 35 ]. As it is known, polychromes, as a part of heritage, should be particularly protected.…”