Abstract
Portable and mobile Raman spectroscopy systems are increasingly being adopted in in situ non-invasive examination of artworks given their high specificity in material identification. However, these systems typically operate within centimeter range working distances, making the examination of large architectural interiors such as wall paintings in churches challenging. We demonstrate the first standoff Raman spectroscopy system for in situ investigation of historic architectural interior at distances > 3 m. The 780 nm continuous wave laser-induced standoff Raman system was successfully deployed for the in situ examination of wall paintings, at distances of 3-15 m, under ambient light. It is able to identify most common pigments while maintaining a very low laser intensity to avoid light induced degradation. It is shown to complement our current method of standoff remote surveys of wall paintings using spectral imaging.
Highlights
The identification of materials such as pigments plays an important role in the study of wall paintings in caves, tombs and buildings since they can reveal information about art history, trade and cultural exchanges in the past, as well as monitoring signs of degradation
We present the developments of a mobile standoff Raman system for wall paintings working in the range from 3 to 15 m using a continuous wave (CW) laser at 780 nm, and its first application in remote pigment identifications of wall paintings
For a pigment of medium sensitivity to laser induced degradation such as red lead, the damage threshold of ∼106 W cm−2 [13,14] means that the detection efficiency is about an order of magnitude lower for an ns-pulsed laser compared with a 50 mW CW laser assuming a spot size of a few mm in diameter
Summary
The identification of materials such as pigments plays an important role in the study of wall paintings in caves, tombs and buildings since they can reveal information about art history, trade and cultural exchanges in the past, as well as monitoring signs of degradation. These paintings are fragile, which limits the possibilities of sampling or contact measurements, and necessitates in situ and non-invasive measurements. We present the developments of a mobile standoff Raman system for wall paintings working in the range from 3 to 15 m using a continuous wave (CW) laser at 780 nm, and its first application in remote pigment identifications of wall paintings
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