Looking Through Paintings by Combining Hyper-Spectral Imaging and Pulse-Compression Thermography

Abstract

The use of different spectral bands in the inspection of artworks is highly recommended to identify the maximum number of defects/anomalies (i.e., the targets), whose presence ought to be known before any possible restoration action. Although an artwork cannot be considered as a composite material in which the zero-defect theory is usually followed by scientists, it is possible to state that the preservation of a multi-layered structure fabricated by the artist’s hands is based on a methodological analysis, where the use of non-destructive testing methods is highly desirable. In this paper, the infrared thermography and hyperspectral imaging methods were applied to identify both fabricated and non-fabricated targets in a canvas painting mocking up the famous character “Venus” by Botticelli. The pulse-compression thermography technique was used to retrieve info about the inner structure of the sample and low power light-emitting diode (LED) chips, whose emission was modulated via a pseudo-noise sequence, were exploited as the heat source for minimizing the heat radiated on the sample surface. Hyper-spectral imaging was employed to detect surface and subsurface features such as pentimenti and facial contours. The results demonstrate how the application of statistical algorithms (i.e., principal component and independent component analyses) maximized the number of targets retrieved during the post-acquisition steps for both the employed techniques. Finally, the best results obtained by both techniques and post-processing methods were fused together, resulting in a clear targets map, in which both the surface, subsurface and deeper information are all shown at a glance.

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

“…Heat can be generated by flashes, LEDs (Light-Emitting Diodes) and halogen lamps, resulting in short pulses of thermal waves (Pulse Thermography, PT), long pulses or steps (SHT), waves in lock-in mode (Lock-in Thermography, LT) or coded-waveforms. Pulse-compression thermography has recently been combined with coded-waveforms by obtaining very low T increments in cultural heritage items [2], [7][8]. The thermographic tests presented here have been carried out with PT using 3300W flashes, and six halogen lamps of 300W each for SHT.…”

A Deep Learning Method for the Impact Damage Segmentation of Curve-Shaped CFRP Specimens Inspected by Infrared Thermography

“…Among the most valuable NDT&E methods for the inspection of CM, infrared thermography (IRT) [ 14 ] holds a prominent position by providing fast surface inspection, easy deployment, safety, and relatively low cost. Thermal methods for NDT&E are based on the principle that heat flow in a material is altered by the presence of some types of anomalies [ 15 ]. Usually a heat pulse is used to start this heat flow.…”

Multi-spectral and Thermography Imaging Techniques for the Investigation of a 15th Century Wall Painting

“…When dealing with paintings, a thorough diagnostic approach relies on (i) the integration of data collected from different imaging techniques, (ii) the exploitation of their complementarities in terms of spectral range and/or physical principles, and (iii) the potential combination of the relative outputs via digital imaging processing tools. It is important to note that data integration and fusion can strongly support traditional analytical methods, yielding a comprehensive diagnosis of the painting state of conservation and reducing any ambiguities due to the use of a single diagnostic method [2,[9][10][11]14,[16][17].…”