Virtual reading of a large ancient handwritten science book☆
Introduction
We applied the new x-ray tomography “virtual reading” technique to read inside a large ancient handwritten book without opening it. Positive results were obtained using a compact, laboratory-based radiology system.
This work is based on preliminary investigations that included extensive chemical analysis of ancient manuscripts over six centuries [see Fig. 2[b] and [1]]. The objective was to verify the iron content of black inks in ordinary specimens, e.g., private and administrative records. This element and its quantity are crucial for the technique: it's the x-ray absorption of the ink that provides the necessary x-ray contrast not only for radiology but also for tomographic reconstruction of the writings.
Previous tests in the similar direction also included text recognition by tomography on small fragments of ancient and modern manuscripts using synchrotron radiation [1] and laboratory based [2] x-ray sources. The investigations provided the capability of the technique to detect characters and words on small samples and also assessed the use of contrast mechanisms based on phase effects rather than on attenuation.
All these pioneering efforts aimed to address the key issue: can the technique work for real, large-size books with hundreds of pages—still using a laboratory based equipment suitable for future applications in the manuscript collections sites? This was the objective of the present investigation, and the results are positive.
The development of the virtual reading technique is primarily inspired by the Venice Time Machine (VTM) project [6]. This is an ongoing collaboration between the Ecole Polytechnique Fédérale de Lausanne (EPFL) and two institutions in Venice: the University Ca' Foscari and the “Archivio di Stato”. The Archivio is an historical collection containing almost 100 km of handwritten documents covering ten centuries of the administrative and legal life of Venice. But, as for all ancient collections, their exploitation by scholars is problematic for conservation and logistic reasons: without massive digitization, deciphering, indexing and storage, they are almost unusable. Such are the tasks targeted by the VTM project.
The project also includes the development of novel digitization techniques, since the present ones would require up to 20 years to complete the task. Among the new approaches, a leading one is virtual reading: the use of x-ray imaging to analyze specimen without opening them. The approach is based on pioneering research of other authors [10], [4], [11], [7], [15], [14], [17], [3] and on the wide experience of Swiss institutions in x-ray techniques. Virtual reading is not limited to conventional tomography based on x-ray absorption but also involves phase approaches [12], [13], [8], [18].
Section snippets
Chemical analysis of ancient inks
The book was chemically analyzed with x-ray fluorescence (XRF) spectroscopy in order to assess the chemical composition of the black ink (no color inks were present) and predict the x-ray contrast. Fig. 1 shows the head of the spectroscopy instrument during the analysis.
Fig. 2[a] presents XRF spectra of ink in text and drawings. The results emphasize the iron content fluctuations, which could be explained by the frequent use of new inks and/or by the handwriting process. These features are also
Results and discussion
Fig. 4 shows a typical example of individual x-ray projection. Clearly, the overlapping of many pages makes impossible to directly use the radiographic images for our text recognition objective. A posteriori extraction of bi-dimensional pictures from the three-dimensional tomographic reconstructed volume solves this problem.
Fig. 5 shows an example of reconstructed volume: the three-dimensional structure of the 10 × 10 × 5 cm3 portion of the book investigated. We can clearly see page side edges.
The
Conclusions
Our investigations confirm the potentiality of the non-invasive, lab-based technique to “virtually read” large ancient handwritten manuscripts. However generally positive, results also reveal some critical obstacles. In particular, to become a competitive technique, the acquisition of the tomographic dataset must be accelerated. This will require additional tests to progressively increase the source current while carefully monitoring possible signs of damage.
Moreover, the standard algorithm for
Acknowledgments
The authors are grateful to Patrick Aebischer for his leadership of the VTM project, to the Verbantiqua bookstore (www.copernicum.it) for their generous donation of antique manuscript specimens, to Ferruccio Petrucci for his assistance in the chemical analysis and for several stimulating discussion and to the staff of the Center for X-ray analytics, EMPA, for the excellent technical assistance. The research was supported by the Venice Time Machine Project and the Center for Biomedical Imaging
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Selected papers presented at TECHNART 2015 Conference, Catania (Italy), April 27–30, 2015.