New device can read the pages of a book without opening it
Researchers from MIT and Georgia Tech in the US have figured out a way to read the pages of a book without actually opening it.
The team from the two institutions pulled it off with a system they developed that looks like a cross between a camera and a microscope.
They said it could someday be used by museums to scan the contents of old books too fragile to handle or to examine paintings to confirm their authenticity or understand the artist's creative process.
Writing in the latest issue of the journal Nature Communications, the scientists explained how they used terahertz waves - a type of radiation situated on the electromagnetic spectrum between microwaves and infrared light - to read a stack of papers with a single letter handwritten on each page.
The device, called a terahertz spectrometer, managed to clearly read only nine pages, though it could see writing on up to 20.
"We were very excited because we didn't think we would be able to see as deep as we did," said Barmak Heshmat, a research scientist at the MIT Media Lab.
While the device is still a long way from actually scanning an entire book, Mr Heshmat said the team is already talking with the Metropolitan Museum of Art in New York about using it to inspect some of its artworks and antique volumes.
He said it could also be used in industry - for example, to see whether there are cracks or other defects beneath the paint on an aircraft part.
Mr Heshmat said that for now, broader uses would be limited by the cost of the device, which runs about 100,000 US dollars (£75,000).
The device works by directing ultrashort bursts of terahertz radiation at stacks of paper. Some of it is absorbed by the paper, and the remainder is reflected back. The signals that bounce back are then analysed with algorithms that can discern individual letters.
In the study, the stack of paper had no cover, but Mr Heshmat said he is confident the system could see through one.
Mr Heshmat said the system works much better than X-rays, which are currently used to scan documents and paintings but entail harmful levels of radiation.
With X-rays "you won't be able to read the pages unless the ink is written by some metal like silver or gold", he said.
"But with our system, because it uses a different part of the electromagnetic spectrum, it can identify many other chemicals, so it can contrast between the blank paper and the part that has ink."