Type: (Multi/Hyper Spectral) Imaging

Overview

The stimulated Infrared thermography (SIRT) system has been developed by the LRMH and the University of Reims Champagne Ardenne. This instrumentation aims at seeking the state of conservation of different artworks, especially mural painting. It consists on a brief light excitation of the surface in order to look at the heat diffusion to detect defects of the material.

First, the analyzed sample is excited with a flux of photons that produce an increase of the temperature of the area. The variation of temperature leads to a variation of the infrared radiation that is visualized through an infrared thermography camera. The photo-thermal signal depends on parameters governing these physical phenomena: thermal conductivity, thermal emissivity, thermal diffusivity, temperature, specific heat, and density. In addition, theses parameters can be correlated with the following characteristics of the object: aspects of the surface, presence of delamination, presence of cracks, internal structure of the material, progress of a physical and chemical transformation, drying and sedimentation, etc…

For the mapping, the hotter colors reveal warmer spots, which are linked to the presence of an active interface between materials or layers with different properties, for example a void beneath the surface or an interface between two different mortars.

The system can be used as well in a passive way in order to reach the variation of temperature on a surface.

Technical details

It comprises an excitation device, a detection device, and computing instrumentation for monitoring. In order to obtain homogeneous energy deposition, the excitation source is a couple of halogen lamps (Halogen I.R. Ceramic 500 W). This excitation source is modulated, in a pulse way, by means of electronics and of a computing of monitoring. The detection system is constituted of an infrared camera of thermography working in a synchronous way with the excitation system (20 °x 15° /0,3 m Field of view, 1,1 mRad Spatial resolution, 50 mK at 30°C Thermal sensivity, 7,5 to 13 µm Spectral range). Finally, an analysis module completes the system. The measurement can be done in the range of temperature -40°C to120 °C, with 2°c or 2% of accuracy.

Further readings

1. E. Bernikola, E. Tsiranidou, V. Tornari, V. Detalle, et J. L. Bodnar, « Mapping of defect structural micro-morphology in the documentation of conservation approaches », in Progress in Cultural Heritage Preservation, Springer, 2012, p. 86–96.
2. J. L. Bodnar, K. Mouhoubi, G. Szatanik-Perrier, J. M. Vallet, et V. Detalle, « Photothermal Thermography Applied to the Non-destructive Testing of Different Types of Works of Art », International Journal of Thermophysics, vol. 33, no 10‑11, p. 1996‑2000, nov. 2012.
3. J. L. Bodnar, J. L. Nicolas, J. C. Candoré, et V. Detalle, « Non-destructive Testing by Infrared Thermography Under Random Excitation and ARMA Analysis », International Journal of Thermophysics, vol. 33, no 10‑11, p. 2011‑2015, nov. 2012.
4. Vallet, J.M, Detalle, V., De Luca, L., Bodnar, J.L., Guillon, O.et al“Development of a NDT toolbox dedicated to the conservation of wall paintings: application to the frescoes chapel in the Charterhouse of Villeneuve-lez-Avignon (France),” 2013 Digital Heritage International Congress, Oct 2013, Marseille, France (2013).
5. Giovannacci, D., Detalle, V., Martos-Levif, D., Ogien, J.,Bernikola, E.,et al.,
   ” Case study of Sainte-Marie Chapel, Fontaine Chaalis (France): complementarity of different optical techniques “, Proc. SPIE 9527, Optics for Arts, Architecture, and Archaeology V, 95270L (July 7, 2015); doi:10.1117/12.2184600; http://dx.doi.org/10.1117/12.2184600.

Providers

MOLAB France: CNRS