Confocal Terahertz Imaging of Ancient Manuscripts

Terahertz imaging has the potential to identify and decipher portions of ancient manuscripts, which may be unreadable at infrared and visible wavelengths. We use a scanning confocal terahertz microscope to scan a medieval parchment with music notes and pentagrams written with different inks. The mic...

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Bibliographic Details
Published in:Journal of infrared, millimeter and terahertz waves millimeter and terahertz waves, 2017-04, Vol.38 (4), p.435-442
Main Authors: Flammini, Mariano, Bonsi, Claudia, Ciano, Chiara, Giliberti, Valeria, Pontecorvo, Emanuele, Italia, Paola, DelRe, Eugenio, Ortolani, Michele
Format: Article
Language:English
Subjects:
Classical Electrodynamics
Continuous radiation
Electrical Engineering
Electronics and Microelectronics
Engineering
Historic artifacts
Horn antennas
Infrared photography
Inks
Instrumentation
Numerical aperture
Parchment
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Summary:Terahertz imaging has the potential to identify and decipher portions of ancient manuscripts, which may be unreadable at infrared and visible wavelengths. We use a scanning confocal terahertz microscope to scan a medieval parchment with music notes and pentagrams written with different inks. The microscope is based on a continuous-wave solid-state source at 0.3 THz, emitting in the free space with a horn antenna, and a high numerical-aperture ellipsoidal reflector. We present terahertz images with diffraction-limited lateral resolution of approximately 0.5 mm, where the different inks all give similar high contrast. Symbols written on the “verso” side of the parchment, barely glimpsed in the near-infrared photograph, leave a clear imprint in the terahertz images. Artifacts due to imperfect flatness of the parchment are also briefly discussed.
ISSN:1866-6892
1866-6906
DOI:10.1007/s10762-016-0338-x