[Technology Empowers Cultural Heritage: A Typical Case]
A robotic arm flexibly rotates as beams of invisible terahertz waves silently sweep across the mottled surface of a Sanxingdui bronze vessel, revealing secrets hidden beneath layers of corrosion… Recently, at the Terahertz Science and Technology Key Laboratory of Sichuan Province at the University of Electronic Science and Technology of China (UESTC) (hereinafter referred to as “the Laboratory”), a “dialogue” across time and space between modern scientists and ancient master craftsmen unfolded. As “terahertz fingerprint spectra” rich in molecular structural information appeared on computer screens, scientists obtained material information about corrosion products and surface attachments at different layers on this bronze artifact.
Accurately obtaining information such as an artifact’s production date and elemental composition while minimizing damage has always been the “spear” and “shield” of modern science and cultural relic conservation. With breakthroughs in conventional non-destructive testing technologies such as X-rays and infrared, researchers are now exploring new directions for in-situ, non-destructive, and holistic acquisition of surface-layer information such as pigments and coatings.
Under the leadership of Director Min Hu, the research team is collaborating with Zhejiang University, the Sichuan Provincial Institute of Cultural Relics and Archaeology, and the Sanxingdui Museum. They are using a self-developed, internationally first-of-its-kind terahertz near-field imaging system based on vacuum electronic devices to perform tomography analysis on bronze artifacts from Sanxingdui. This is also the first time globally that terahertz waves have been used for tomographic imaging of bronze cultural relics.
“Terahertz waves, or terahertz for short, refer to electromagnetic waves with frequencies ranging from 0.1 terahertz to 10 terahertz, and wavelengths between approximately 0.03 mm and 3 mm,” said Min Hu. Compared with ionizing techniques like X-rays, terahertz photons have extremely low energy and do not cause harmful ionization reactions. This allows researchers to gain insights into an artifact’s internal structure and material composition without damaging it, and it also poses no harm to the researchers. “It can penetrate most non-metallic materials, obtaining layered structural information through multiple reflections of time-domain pulses within the object, thus eliminating the need for sampling or slicing the artifact.”
Postdoctoral researcher Zhang Xiaoqiuyan from the Laboratory explained, taking the identification of corrosion layers on Sanxingdui bronzes as an example: researchers first use structured light technology to quickly construct a 3D contour of the artifact, creating a “digital map.” Based on this map, intelligent algorithms then plan a terahertz wave scanning path to ensure perpendicular incidence for precise identification of the corrosion layer thickness.
“During corrosion layer identification, the robotic arm controls the detection probe to emit terahertz waves that penetrate the corrosion layers, collecting their internal structural and material property ‘secrets.’ Finally, the detection data is combined with the bronze’s 3D contour to generate a three-dimensional imaging map of the corrosion layer, visually displaying its distribution, morphology, and thickness variations,” Zhang said. Combined with “terahertz fingerprint spectra,” conservation experts can clearly distinguish between harmful and harmless corrosion and their distribution, making restoration work more precise and efficient.
Terahertz wave scanning uses femtosecond pulse time-of-flight imaging, which can deliver preliminary surface-layer information within 10 minutes after an artifact is unearthed. It also achieves high-resolution imaging, with thickness identification accuracy reaching 10 micrometers and horizontal accuracy down to 50 nanometers. “Our laboratory will leverage its strengths in terahertz technology to provide scientific support such as non-destructive testing and disease diagnosis for artifacts from the Sanxingdui site. We have now reached a consensus with the Sanxingdui Museum to engage in in-depth collaboration on archaeological research, artifact conservation, and cultural heritage related to the Sanxingdui site,” said Zhang Xiaoqiuyan.
“In the future, the laboratory will also introduce artificial intelligence and machine learning technologies. By combining them with terahertz technology, we can enhance the efficiency and accuracy of data processing and analysis, making detection results more detailed and reliable,” Min Hu added. At the same time, they will strengthen interdisciplinary cooperation with fields such as archaeology and materials science to promote innovative applications of terahertz technology in cultural relic conservation.
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Source: University of Electronic Science and Technology of China (UESTC) News Network (reprinted from Science and Technology Daily) View original article