This site may earn affiliate commissions from the links on this page. Terms of use.

Ten years ago, MIT researchers demonstrated they could use terahertz imaging to read a letter of the alphabet inside a sealed FedEx envelope. Now a team from the MIT Media Lab has used terahertz radiation and a sophisticated epitome parsing algorithm to read the text on pages inside a stack up to nine sheets deep. Information technology has implications for historical conservationists, real-time mail screening, and doubtless a agglomeration of other things that haven't fifty-fifty been invented yet.

The new technique is like a cross between sonar and those much-maligned airport body scanners. Information technology starts out using terahertz radiations, which is a band of EM radiation that has lower energy and longer wavelength than the visible and IR bands. Terahertz waves are still less than a millimeter long, acme-to-peak.

For this projection, the researchers used terahertz-band radiation because it has several advantages over other types of waves (like X-rays or sound) that tin penetrate surfaces. Simply similar how dissimilar chemicals polarize light differently, chemicals absorb frequencies of terahertz radiation to different degrees, throwing off a distinctive frequency signature for each. This is what makes them useful for distinguishing between C4 and tissue in the airport scanners. Terahertz frequency profiles tin too distinguish betwixt ink and blank paper, where Ten-rays can't.

Image: MIT

Image: MIT

The system also exploits the principle of refraction. Trapped between the pages of a book are tiny air pockets only about xx micrometers deep (presumably, filled with that new book odor). The difference in refractive index between the air and the paper means that the boundary between the ii volition reflect terahertz radiation back to a detector.

Terahertz radiation can as well be used like sonar, because it can exist emitted in extremely brusque bursts. The time between when the wavefront is emitted and when it's reflected back to the sensor can accurately tell united states of america how far information technology has traveled. This gives information technology much better depth resolution than ultrasound.

In the researchers' setup, all these principles converge. A standard terahertz camera emits ultrashort bursts of radiations, and the camera's built-in sensor detects the time to pingback. From the pingbacks' fourth dimension of inflow, the MIT researchers' algorithm can estimate the distance to the individual pages of the book. And then, an algorithm developed by researchers from Georgia Tech interprets the oftentimes distorted or incomplete images as individual messages.

"The Metropolitan Museum in New York showed a lot of interest in this, considering they desire to, for example, wait into some antiquarian books that they don't fifty-fifty want to bear upon," said Barmak Heshmat, a corresponding author of the new paper. Crumbling antique manuscripts could exist imaged using this technology, without ever having to physically disturb the artifact.

And who knows what we might uncover, obscured beneath erasures and layers of ink and pigment? The ability of the alphabetic character-recognition algorithm is "actually kind of scary," Heshmat says. "A lot of websites have these alphabetic character certifications [captchas] to brand certain yous're not a robot, and this algorithm tin can get through a lot of them."