Multiphoton microscopy: an efficient tool for in-situ study of cultural heritage artifacts

Gaël Latour; Jean-Philippe Echard; Marie Didier; Marie-Claire Schanne-Klein

doi:10.1117/12.2020221

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30 May 2013 Multiphoton microscopy: an efficient tool for in-situ study of cultural heritage artifacts

Gaël Latour, Jean-Philippe Echard, Marie Didier, Marie-Claire Schanne-Klein

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Proceedings Volume 8790, Optics for Arts, Architecture, and Archaeology IV; 87900L (2013) https://doi.org/10.1117/12.2020221
Event: SPIE Optical Metrology 2013, 2013, Munich, Germany

Abstract

We present multimodal nonlinear optical imaging of historical artifacts by combining Two-Photon Excited Fluorescence (2PEF) and Second Harmonic Generation (SHG) microscopies. Three-dimensional (3D) non-contact laser-scanning imaging with micrometer resolution is performed without any preparation of the objects under study. 2PEF signals are emitted by a wide range of fluorophores such as pigments and binder, which can be discriminated thanks to their different emission spectral bands by using suitable spectral filters in the detection channel. SHG signals are specific for dense non-centrosymmetric organizations such as the crystalline cellulose within the wood cell walls. We also show that plaster particles exhibit SHG signals. These particles are bassanite crystals with a non-centrosymmetric crystalline structure, while the other types of calcium sulphates exhibit a centrosymmetric crystalline structure with no SHG signal. In our study, we first characterize model single-layered samples: wood, gelatin-based films containing plaster or cochineal lake and sandarac film containing cochineal lake. We then study multilayered coating systems on wood and show that multimodal nonlinear microscopy successfully reveals the 3D distribution of all components within the stratified sample. We also show that the fine structure of the wood can be assessed, even through a thick multilayered varnish coating. Finally, in situ multimodal nonlinear imaging is demonstrated in a historical violin. SHG/2PEF imaging thus appears as an efficient non-destructive and contactless 3D imaging technique for in situ investigation of historical coatings and more generally for wood characterization and coating analysis at micrometer scale.

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Gaël Latour, Jean-Philippe Echard, Marie Didier, and Marie-Claire Schanne-Klein "Multiphoton microscopy: an efficient tool for in-situ study of cultural heritage artifacts", Proc. SPIE 8790, Optics for Arts, Architecture, and Archaeology IV, 87900L (30 May 2013); https://doi.org/10.1117/12.2020221

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