Terahertz frequency modulated continuous wave imaging for nondestructive evaluation of painting and multilayer parts Xue Maa,b, Kejia Wangb, Frédéric Fauqueta, Marie Rouxc, Corinna Ludovica Koch Dandoloa, Patrick Mounaixa, JeanPaul Guilleta University of Bordeaux, IMS Laboratory, UMR CNRS 5218 351 cours de la Libération 33405 TALENCE b Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074, China c L’Atelier des Renaissances, 1 allée de Gieu, 33650 SAUCATS, France a
INTRODUCTION
RESTORATION
Most of the art painting measurement using
FMCW was used before restoration to detect
terahertz were done using time domain system,
some defects in the painting. Then another
but Frequency modulated continuous wave
measurement was done after restoration
(FMCW)
system
have
some
advantages
(Synview ®)
Fig1. Basic principle of FMCW representing frequency of the signal as a function of time. Red curve corresponds to emited signal and blue to
Fig. 3 : Photography of the painting 78cm by 62cm
Fig. 6 : FMCW images helping art restorer to detect defects in the painting
received signal. Time of flight of electromagnetic wave can be calculated from frequency difference of these signals.
SETUP Fig. 7 : FMCW images after parameter extraction with fit and filtering [2] • Large scan area : 600 x 800 mm Four heads : two both emitting and receiving and two only receiving signals • Two frequency ranges, from 75 to 110 GHz and from 220 to 330 GHz
Fig. 4: On the left: 300GHz reflection image of the painting before restoration. The surrounded areas are air voids between pictorial layer and canvas On the right: 300GHz reflection image of the painting after first step of restoration. The surrounded areas have been restored
CONCLUSIONS We have demonstrated that Frequency Modulated Continuous Waves terahertz (300 GHz) can be proficiently used for
• The spatial resolution 3 mm at 100 GHz
detecting conservation problems such as
and 2 mm at 300 GHz
paint layer losses and subsurface cracks
• 50 to 60 dB dynamic range depending
in easel paintings.
topology and frequency
REFERENCES
Fig. 2: Photography of the painting in the FMCW system
Fig. 5 : Photography of the before, during and after restoration
L’atelier des renaissances
1. Guillet, J.P., Roux, M., Wang, K., Ma, X., Fauquet, F., Balacey, H., Recur, B., Darracq, F. and Mounaix, P., “Art Painting Diagnostic Before Restoration with Terahertz and Millimeter Waves,” J. Infrared, Millimeter, Terahertz Waves 38(4) (2017). 2. Koch Dandolo C, Guillet JP, Ma X, Fauquet F,Roux M., Mounaix P, "Terahertz frequency modulated continuous wave imaging advanced data processing for art painting analysis", Optics Express, Accepted, to be published