MIT Researchers Develop a Camera that Reads Through Closed Books

September 19, 2016 | Erica Tennenhouse

Photo credit: Courtesy of Barmak Heshmat

Terahertz radiation can penetrate stacks of paper, deciphering printed text up to nine sheets deep.

With the help of a new device being developed by researchers at MIT, soon books covers will no longer pose barriers to the content within.

A prototype of the system has already successfully peered through a stack of papers — each containing a single letter — and correctly identified the letters printed on the top nine pages. But the researchers hope that with some tweaks, the technology will eventually be able to peer right through book covers.

"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 corresponding author on a paper published in Nature Communications, in a press release.

The imaging system uses terahertz radiation, which is a wave frequency that sits between microwaves and infrared light on the electromagnetic spectrum. Because different chemicals react differently when they’re hit with terahertz radiation, the waves can relay information back to a sensor about which parts of the page are blank and where letters are printed in ink.


An advantage of terahertz radiation is that it can be emitted via very short bursts, so that the difference between its emission time and the time when its bounce-back reaches the sensor gives a precise estimate of the depth it reached.

Although the initial test was promising, the signals produced by the letters on the pages were slightly masked by radiation that got caught bouncing between pages before arriving at the sensor. Because of this noise, the device is currently limited to counting 20 sheets deep, and reading the print on the first nine pages only.

But by reducing this interference and increasing the power of the radiation source, the researchers hope to be reading through closed books in the near future.

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