Well, not quite. As per a report in the latest issue of Nature Communications, the MIT team described a prototype of their invention. To test the device, they stacked several sheets of paper, each of which had a single letter printed upon it. The system correctly identified the letters printed upon the top nine sheets. So while the machine might not be able to see through an actual cover quite yet, the hope is that one day, this will be the end result.
“The Metropolitan Museum in New York showed a lot of interest in this, because they want to, for example, look into some antique books that they don’t even want to touch,” said Barmak Heshmat, a research scientist at the MIT Media Lab and author on the new paper.
So how does the system work? It all comes down to terahertz radiation, described as “the band of electromagnetic radiation between microwaves and infrared light.” This sort of radiation is often used in security screening as “different chemicals absorb different frequencies of terahertz radiation to different degrees, yielding a distinctive frequency signature for each.” That means that terahertz frequency profiles are capable of making the distinction between, say, ink and paper, whereas other penetrating radiation like X-rays cannot.
And to deal with the tiny air pockets that exist between pages, the MIT system uses short bursts of this radiation to measure the difference in refractive index (the degree to which they bend light) between the air and the paper. This ultimately lets the device create an image of the letters they “see.”
“So much work has gone into terahertz technology to get the sources and detectors working, with big promises for imaging new and exciting things,” Laura Waller, an associate professor of electrical engineering and computer science at the University of California at Berkeley, told MIT News. “This work is one of the first to use these new tools along with advances in computational imaging to get at pictures of things we could never see with optical technologies. Now we can judge a book through its cover!”