Terahertz imaging reveals hidden inscription on early modern funerary cross

Terahertz imaging reveals hidden inscription on early modern funerary cross

Georgia Tech professor David Citrine (right) and Associate Professor Alexandre Luquet stand in front of the 16th-century image of a funeral cross used in their study. Credit: Georgia Tech Lauren

In an interdisciplinary project, researchers at Georgia Institute of Technology and Georgia Tech Lauren used terahertz imaging and signal processing techniques to search beneath the eroded surface of a 16th-century funeral cross. Led by David Citrine, a professor in the School of Electrical and Computer Engineering (ECE), the effort combined imaging scientists, a chemist specializing in archaeological objects, and an art historian to uncover a message that had been obscured by time: an inscription from the Lord’s Prayer.

“Our approach enabled us to read a text hidden beneath it Eat, perhaps for hundreds of years,” said Alexandre Luquet, associate professor at ECE and researcher at Georgia Tech-CNRS IRL 2958, a joint international research laboratory at the Georgia Tech-Lorraine campus in Metz, France. Obviously, it’s getting close to that reach. Such information without damaging the object is of great interest to archaeologists.”

The study was reported March 2 in the journal Scientific Reports.

The cross, cut from a piece of lead, was found in a burial plot in a convent in Remiremont, France – a two-hour drive from the Georgia Tech-Lorraine campus. known as croix حل solutiona type of funerary cross that dates back to the Middle Ages and has been found at sites in France, Germany and England.

“This type of cross usually bears inscriptions of prayers or information about the deceased,” said Aurélien Vacheret, director of the Charles-de-Bruyères Museum in Remiremont and co-author of the study. “It is believed that their aim was to seek to absolve man from sin, and to facilitate their passage to Heaven.”

The museum loaned the cross to Citrine Lab in the hope that the team could use imaging techniques to make the invisible visible. Citrine and his group specialize in non-destructive evaluation and develop techniques that allow a detailed examination of an object’s hidden layers without altering or damaging its original shape. Although their work often has industrial applications, such as detecting fuselage damage, the group took the opportunity to examine the cross – an opportunity to further explore applications of their technology for archaeological purposes.

Peering under the veil of erosion

The team used commercial terahertz Scanner To examine the junction every 500 microns (about every half a millimeter) across the body. First, the scanner sent short pulses of terahertz electromagnetic radiation — a form of light transmitted at small wavelengths — over each section of the cross. Some waves bounced back from the erosion layer, while others pierced through the erosion, reflecting the actual surface of the lead cross. This produced two distinct echoes of the same original pulse.

Next, the team used an algorithm to manipulate the time delay between the two reverberation In a two-peaked sign. These data revealed how intense the erosion was at each point scanned. Measurements of the light rays reflected from the base metal were then collected to form images of the lead surface beneath the corrosion.

multidisciplinary insights

Although critical data was collected during the scanning process, the raw images were very noisy and jumbled and the inscription remained illegible at the time. But Junliang Dong, who had obtained his Ph.D. A student in the Citrine Laboratory, has the insight to process images in a special way to eliminate the noise. By subtracting parts of the images obtained at different frequencies and grouping them together, Dong was able to recover and improve the images. What remained was a surprisingly legible image containing the text.

Terahertz imaging reveals hidden inscription on early modern funerary cross

Comparison of the etching on (a) the original junction before de-erosion, (b) the final terahertz image after post-treatment, and (c) the junction after de-corrosion. Credit: Georgia Tech Lauren

Using processed images, Vacheret was able to identify many Latin words and phrases. He has determined that they are all part of Pater Noster, better known as The Father or the Lord’s Prayer.

The team also worked with a conservationist to reverse the chemical corrosion on the cross, confirming the Butter Noster inscription. By comparing their images with the clean cross, the team found that their images revealed parts of the inscription not observable on the original cross. By revealing additional aspects of the inscriptions that were previously undocumented, their work was able to offer a deeper understanding of the cross and greater insight into Christianity in the sixteenth century in Lorraine, France.

“In this case, we were able to verify our work afterward, but not all lead objects can be processed in this way,” Citrine said. “Some things are big, some have to stay in place, and some are very sensitive. We hope our work will open up the study of other lead bodies that may also reveal secrets that lie beneath the corrosion.”

I also used citrine group terahertz imaging To look beneath the surface of seventeenth century paintings, to clarify the structure of the paint layer and to provide insight into the techniques of the master painters. They are currently investigating surface coatings on ancient Roman porcelain.

The cross project demonstrates that success requires more than just accurate measurement, but also accurate data processing and collaboration between researchers from different fields. The team’s approach opens up new avenues for analyzing terahertz images and could result in significant enhancements to the areas of digital acquisition and documentation, as well as character recognition, extraction and classification.

“Despite three decades of intense development, terahertz imaging is still a rapidly developing field,” Loquet said. “While others focus on hardware development, our efforts focus on getting the most out of the data being measured.”


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more information:
Junliang Dong et al, Reveals time-obscured inscriptions on an early modern lead funerary cross using multispectral terahertz imaging, Scientific Reports (2022). DOI: 10.1038 / s41598-022-06982-2

the quote: Terahertz imaging reveals hidden inscription on early modern funerary cross (2022, April 25) Retrieved April 25, 2022 from https://phys.org/news/2022-04-terahertz-imaging-reveals-hidden-inscription.html

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