Terahertz data processing for imaging and spectroscopy of artwork
Odlyanitskiy, Evgeniy L., Olga A. Smolyanskaya, Sergei Sirro, Jean-Paul Guillet, Vincent Detalle, and Michel Menu. “Terahertz data processing for imaging and spectroscopy of artwork.” In Optics for Arts, Architecture, and Archaeology VIII, vol. 11784, p. 117840D. International Society for Optics and Photonics, 2021.
Terahertz (THz) radiation in the frequency range 0.1 – 10 THz began to be used for the analysis of artwork in 2006. Terahertz images of paintings require computer processing in order to optimize the process of detecting defects and their visualization. In this work, an algorithm for solving this problem is proposed in relation to the terahertz analysis of paintings. A program is written in Python that searches, group and highlight defects in an image. To work with images, the methods of the OpenCV library is used, designed to solve computer vision problems. They are used to binarize images and search the defect contours on them, as well as to isolate defects when visualizing the results. The grouping of defects is carried out by the method of agglomerative hierarchical clustering. Scientific analysis of the materials used in art items allows to determine the period in which they were created, how they were preserved over the centuries and how they were restored. As part of the study, in this work, a 3D-model of the crystal structure of the red pigment was created. For this, the terahertz spectrum of the pigment was modeled by the density functional method. To experimentally study the optical characteristics of the pigment, measurements are carried out on a TeraView-4000 instrument in transmission mode. The pigment is measured in powder and tableted form.
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