Emerging photonic technologies for cultural heritage studies: the examples of non-linear optical microscopy and photoacoustic imaging

Abstract

The availability of non-invasive technologies, which can be used separately or in combination for obtaining chemical composition data and structural information of Cultural Heritage (CH) materials, is of prime importance for improving the understanding the environmental or ageing impact on monuments and artefacts and defining optimal strategies for their conservation. This paper overviews and assesses the potential of two emerging photonic technologies, the Non-linear Optical Microscopy (NLOM) and Photoacoustic (PA) imaging modalities, for a variety of diagnostic applications in preservation science. These techniques, which are well-established in biomedical research, during the last few years have been also investigated as non-invasive tools for the in-depth, high-resolution analysis of various CH objects, including paintings, documents and murals. We discuss on the applicability of these diagnostic optical methods to obtain precise stratigraphic information in artefacts, evaluating additionally the presence and the extent of potential morphological or chemical changes in several CH materials due to ageing. Furthermore, we demonstrate that the contrast complementarity of NLOM and PA imaging provides invaluable insights into the structural integrity of an artwork, which can be subsequently utilized for the early and accurate detection of depth degradation effects.