Application of terahertz spectroscopy for character recognition in a medieval manuscript

Abstract

Terahertz (THz) technology is a focus of attention in research on applied optics. We have applied THz spectroscopy and THzimaging method to text recognition of a medieval manuscript made from sheepskin. Based on the database which contains more than 200 spectra of art materials, the red ink on the manuscript was estimated as Cinnabar. The red ink text and stains on the text were successfully distinguished by the THz-Time Domain Spectroscopy (TDS) imaging with a component spatial pattern analysis. THz spectroscopy can be used as a non-invasive analysis method for conservation science of cultural properties.

Review of Terahertz Tomography Techniques

“…A similar study was presented by Fukunaga and coworkers [127] to quantify the transmittance of several pigments. Recently, they extended their work to a medieval manuscript [128] and even mummies have been studied by THz imaging [129]. All this clearly demonstrates the potential of THz imaging for Art and Archeological science (Fig.5).…”

“…The first implementation of this method was reported by Ferguson et al who imaged a simple polyethylene cylinder and proposed a reconstruction method based on the Born linearization of the wave equation [138]. Figure 5 Images of a part of a medieval parchment with visible and terahertz light [128] Wang et al performed THz diffraction tomography by using a mode-locked femtosecond laser, generating THz radiation by optical rectification in a ZnTe crystal and detecting the signal with a CCD camera [132] as illustrated in fig.6. They proposed a reconstruction method based on the electromagnetic wave scattering theory.…”

Terahertz and Cultural Heritage Science: Examination of Art and Archaeology

“…THz tomography has been applied to resolve text on both sides of a single papyrus sheet [70,71]. THz was tested also for those cases where writing is obscured by stains and other inks in old purchament manuscripts [72] and it seems successful to characterize and evaluate conservation of iron gall inks [73] and parchment [74].…”

A Continuous Millimeter-Wave Imaging Scanner for Art Conservation Science

“…In cultural heritage science, two main aspects of THz technology can be profitably explored: spectroscopy for the analysis of various artistic materials and noninvasive THz imaging. These 2 Advances in Optical Technologies abilities of THz radiation has been demonstrated in variety of research works reported for the analysis of cultural heritage materials [8], such as evaluation of mural paintings [9] or for character recognition in medieval manuscripts [10]. THz radiation is widely applied for the investigation of paintings and spectroscopic analysis of pigments [11,12].…”