考研阅读精选：经典发明
A classic inventionMultispectral imaging: Ascanner that sees a wider range of colours than the human eye isunlocking previously illegible manuscripts
Dec 3rd 2011 | from the print edition
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TECHNOLOGICAL spin-outs from universities are usually expected toemerge from the engineering department, the school of medicine or thefaculty of physics. At Oxford, however, they like to do thingsdifferently. The latest invention to emerge from the dreaming spires ofEngland’s oldest university is the brainchild not of any of theseacademic Johnny-come-latelies, but rather of a group who trace theirorigins to Oxford’s medieval foundation: its classicists.
Themultispectral-imaging scanner developed in the faculty of classics byDirk Obbink, a lecturer in papyrology and Greek literature, andAlexander Kovalchuk, a mathematician and physicist, is able to detecttraces of faded or hidden inks and paints in historical manuscripts,expose forged documents and art works, and highlight forensic evidencesuch as fingerprints and stains from bodily fluids. It will soon beavailable commercially from a firm called Oxford Multi Spectral.
Multispectral imaging works by scanning objects at a series of specificfrequencies both within and beyond the visible spectrum. It is able tohighlight details human eyes cannot normally see, either because theyare swamped by the signal from other visible frequencies, or becausethey are not detectable by the rod and cone cells of the retina.
Classicists at Oxford first deployed the technique in 1999, to examinepapyri discovered in a villa that was buried by the eruption of MountVesuvius in 79AD. They then applied it to previously illegiblemanuscripts called the Oxyrhynchus papyri, which were discovered in anancient rubbish dump in Egypt. Documents deciphered using it include anepic poem from the 7th century BC by Archilochos and parts of a losttragedy by Sophocles that dates to the 5th century BC.
Overthe past decade Dr Obbink, Dr Kovalchuk and their team have bothimproved the hardware of multispectral analysis (which was originallydeveloped by America’s space agency, NASA), and written moresophisticated algorithms to analyse what is seen. To start with, theyhad to rely on a high-resolution camera mounted on a frame, and a seriesof filters attached to a rotating wheel, to create a set ofsingle-frequency images from the same perspective, in order that theycould be merged as desired.
Now they have something thatworks like a flatbed document scanner, with a scanning head containingeither six or 12 light-emitting diodes, each emitting light of aspecific wavelength between 350 nanometres (ultraviolet) and 800nanometres (infra-red). Each time the head moves across the instrument adifferent diode is switched on, and the results are recorded and fedinto a computer.
Sometimes images taken at a specificfrequency provide the best contrast. For example, iron-gall ink,commonly used on ancient documents, is transparent to infra-red lightand most visible in the ultraviolet region of the spectrum. In othercases the clearest picture emerges by combining images from severalfrequencies. The iron-and-carbon-based ink used in one of the oldestHebrew commentaries on the Old Testament is an example of this. Much ofthe book, which dates from the 10th century AD, was rendered illegiblein the late 19th century by misguided academics who used shellac tovarnish it. Combining data from different frequencies has highlightedthe old ink and allowed the document to be read.
Besideslooking at ancient scrolls, the multispectral scanner can compare thingslike bank notes and passports with reference documents of knownprovenance. Alternatively, as in the case of forensic evidence when theuser does not know precisely what to expect, different combinations offrequencies can be examined to see if anything interesting emerges. Asan added bonus, the new scanner also provides a novel retort to thosewho question the value of studying the classics in the modern world.
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