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http://hdl.handle.net/10174/37170
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Title: | Terahertz imaging super-resolution for documental heritage diagnostics |
Authors: | Antúnez-vázquez, Dánae |
Advisors: | Missori, Mauro Del Re, Eugenio |
Keywords: | Terahertz imaging Terahertz spectroscopy Optical super-resolution Documental heritage Non-invasive diagnosis |
Issue Date: | 3-Oct-2023 |
Publisher: | Universidade de Évora |
Abstract: | Electromagnetic waves are widely used in nondestructive testing of cultural heritage.
The operating frequency region determines the waves’ role because the materials’
responses depend on the frequency. For example, noninvasive material analysis is
possible using fibre optic reflectance spectroscopy (FORS) in the ultraviolet, visible,
and near-infrared frequency ranges, while Fourier transform infrared spectroscopy
(FTIR) is commonly used as a chemical analysis tool. Applying waves in the terahertz
(THz) range, also called the far-infrared range, to diagnostics began about 15 years
ago. THz spectroscopy and imaging are among the emerging technologies for cultural
heritage science.
THz time-domain spectroscopy (TDS) technology was developed in the 1990s.
A THz-TDS system uses narrow pulses with pulse widths of the order of 1 ps. By
applying a fast Fourier transform to the pulse in the time domain, spectra in the
frequency range of about 0.2-4 THz are commonly obtained. Imaging techniques
using THz pulses in the time domain can show the internal structures of opaque
objects based on the time-of-flight technique. The THz waves can penetrate more
deeply than infrared light and can obtain structural information from dielectric
materials that are relatively transparent to X-rays. The present application of THz
technology to artworks is focused on spectroscopic imaging, including the detection
of hidden graphic signs and material identification. However, the spatial resolution
of THz pulsed imaging is diffraction-limited to about the wavelength, which is of
the order of 1 mm for THz waves.
This project will focus on the development of a far-field super-resolution THz
imaging system based on a freestanding knife edge and a transmission or reflective
confocal configuration for the THz beamline, as employed in THz-TDS systems [7].
The super-resolution THz imaging system will be applied to the study of the text
in ancient documents on paper or parchment substrates, where graphic signs with
lateral sizes less than 1 mm are usually found [8]. Super-resolved THz images of
inks, pigments, and dyes used in the past were acquired. The ancient materials and
the mockups for system optimization have been obtained in collaboration with the
National Central Library (Rome, Italy). |
URI: | http://hdl.handle.net/10174/37170 |
Type: | masterThesis |
Appears in Collections: | BIB - Formação Avançada - Teses de Mestrado
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