From medical to art diagnostics OCT: a novel tool for varnish ablation control

Abstract

Since many medical diagnostic methods are non-invasive and even non-contact, they are well suited for inspection of fragile and unique objects of art. In art conservation it is a need for convenient and non-invasive method for monitoring of removal of the varnish layer from paintings -one of the most crucial operations in their restoration. In this study we present application of the Spectral Optical Coherence Tomography (SOCT) for in-situ monitoring of the laser ablation of the varnish layer. The examination of the ablation craters made with Er:YAG laser permits for the optimization of the laser emission parameters like fluency and working regime, with respect to efficiency and safety of the ablation process. Frames from the SOCT movies obtained during real time monitoring of the burning of the ablation crater are shown for the first time.

Characterization of Laser Cleaning of Artworks

“…It enables fast and convenient calibration of ablation conditions for the particular laser-varnish combination [20]. Moreover, the technique provides information on the volume of removed material and the thickness, structure, and quality of the remaining varnish layer [21]. This is essential to control the ablation depth.…”

Picosecond laser ablation system with process control by optical coherence tomography

“…Since the varnish ablation process is obviously irreversible its effective monitoring is very important to make it safe and trusted. As we showed previously [2][3][4][5][6] optical coherence tomography (OCT) originated from medicine diagnostic method for examination and imaging of cross-sections of weakly absorbing objects can be used for this task. OCT utilises infrared light for non-invasive structure examination and has been under consideration for the examining of objects of art since 2004 [7][8][9][10].…”

A swept source OCT at 1300 nm with angular compounding for art and archaeological conservation

“…This includes art & archaeological conservation, where there is currently no effective, non-invasive, high-resolution optical method. Many applications in this field have been suggested including viewing of under-drawings 1,2,3 viewing of sub-surface features 4 , monitoring of varnish ablation 5 , and detection of defects in ceramics 6 .…”