Ancient Writings Come to Light
After nearly 1000 years, the earliest known copy of Archimedes' mathematical theorems can be seen again. Physicist Roger L. Easton Jr. and archaeologist Robert Johnston of the Chester F. Carlson Center for Imaging Science at Rochester Institute of Technology have digitally restored six pages of the original Greek text of Archimedes' discoveries on optics, physics, astronomy and engineering.
Time, mold and neglect had made the writing difficult to distinguish on the document, known as the Archimedes Palimpsest. More critically, most of the original ink had been scraped off the manuscript's surface by a monk who needed the valuable parchment to make a prayer book. "To this 12th-century scribe, Archimedes' theories were not worth the parchment they were written on," commented William Noel, one of the manuscript's curators at The Walters Art Museum in Baltimore, which is responsible for the $2 million document's safekeeping.
But some original writing remained, because the ancient ink contained acids that had seeped into the characters etched in the parchment and bonded to the fibers.
Multispectral imaging revealed that beneath the Latin script of a 12th-century prayer book known as the Euchologion (above) lay older writing -- Archimedes' theorem "On Floating Bodies" in its original Greek (below). Copyright Christie's Images Ltd., 1998.
To enhance the legibility of the original 10th-century text while suppressing the overlying 12th-century script, Easton and Johnston turned to multispectral imaging. To produce a photo for Christie's auction house, they increased the original characters' legibility by using color filters, UV light and a large-format CCD sensor from Eastman Kodak Co. of Rochester, N.Y., that is sensitive to an unusually wide range of wavelengths from 200 to 1200 nm. The system captured information from regions of the electromagnetic spectrum indiscernible to the eye.
"And when illuminated with UV, the page fluoresces, giving you improved contrast for the old text," Easton added. The resulting images were digitally manipulated for maximum clarity using custom pattern recognition software at the Xerox Digital Imaging Technology Center in Webster, N.Y.
Easton said one advantage of the technique is that it leaves the original document unaltered. "We do nothing but expose the manuscript to various kinds of illumination at low light levels that generate little heat," he stated. "It's totally nondestructive."
Other imaging methods are also being considered by the art museum to image the remainder of the 164-page document. But Easton hopes to scan it in finer detail in May, using a new Kodak KAF 1602-E Blue Plus CCD chip that extends blue sensitivity, and a 12-bit Photometrics SenSys camera, made by Roper Scientific of Trenton, N.J., that provides 16 times more shades of gray.
MORE FROM PHOTONICS MEDIA