How to Read a Closed Book

By Carl Engelking | September 9, 2016 4:27 pm

A researcher tests out the new terahertz imaging system. (Credit: Courtesy Barmak Heshmat)

You still can’t judge a book by its cover, but it’s possible to read one without ever opening it.

That certainly adds a new wrinkle to an age-old idiom.

But it’s true; researchers at MIT and Georgia Tech built a prototype — key word prototype — imaging system that can read individual pages in a stack of papers. It’s an early demonstration, so we’re talking a stack of only nine pages, but it’s a start.

And as the technology improves, it could someday give, say, museum curators, another tool to study ancient, fragile books they wouldn’t dare open.

Today’s T-Ray

To peer through stacks of paper, the system relies on terahertz radiation, which is a frequency band of electromagnetic radiation that falls between microwaves and infrared light. Terahertz imaging systems emit short bursts of radiation that can penetrate a variety of materials. Substances such as water, plastics, gases and biofuels absorb specific terahertz frequencies, which makes it easy to identify them.

NASA used the technique to inspect foam insulation structures on its shuttle fleet, and it’s the same technology used in full body scanners at the airport. You know, those scans that produced quasi-pornographic images of airplane passengers.

Page Penetration

Researchers used a standard terahertz camera to blast radiation at a stack of 20 papers with a single letter printed on each, and a sensor detected the reflected radiation. The paper and ink each absorb their signature frequencies, revealing the letters. There are also tiny pockets of air between each sheet of paper, and this boundary affects when of the reflected signal hits the sensor.

The resulting images aren’t exactly pretty — the device’s electronics produce a background hum, and some of the radiation bounces between pages before returning to the sensor. So Georgia Tech and MIT designed algorithms that clean these images up and interpret each page’s contents. Those algorithms, which can decipher contents of tightly stacked pages, are the big improvement here.

Researchers published details about their new technique Friday in the journal Nature Communications.

Seeing Without Touching

Peeking at documents without opening them isn’t a new trick. Using the European Synchrotron Radiation Facility, for example, researchers from France bombarded ancient Herculaneum scrolls with extremely high-intensity X-rays, in a process called scanning X-ray fluorescence. This caused the metallic inks inside to emit photons, and “light up.”

Terahertz imaging has also been used to see inside an ancient Egyptian jar at the Museum of Aquitaine in France. Terahertz radiation revealed previously unknown, organic contents that X-rays wouldn’t have.

So far, the system can penetrate and interpret the top nine pages in a stack of 20 — the signal looses energy the deeper it goes, resulting to too much noise. But as the relatively young technology improves, it’ll be able to dive deeper.

CATEGORIZED UNDER: Technology, top posts
MORE ABOUT: computers, physics
  • OWilson

    NSA can read your unopened mail already.

    I hear smart operators can use similar technology to scan Lotto “scratch and win” tickets too, but the technology is very expensive

    • Uncle Al

      NSA reads everything not for Homeland Severity but for political connivance. I am bursting proud of

      1) Being big data threaded into immortality for being in Hillarity Ramrod Clitler’s “basket of deplorables,” and
      2) Terahertz radiation being remarkably disruptive of living tissue and DNA. Hire the diverse to do all the Social Justice dirty work. doi: 10.1364/OE.22.011465, 10.1016/j.physleta.2009.12.077, 10.1364/BOE.4.000559

      • Erik Bosma

        By changing her last name are you identifying her with a 1./ female body part?
        2./ dead psychopath?

        • OWilson

          There’s very little on her curriculum vitae of value, other than her gender.

          If diversity was an important consideration for CIC, we should vote for succession of LGTB candidates, to prove we are not simply deplorable multi-phobics.

          One Orwellian day, your “voluntarily obtained” day pass will reveal the record who you voted for, and publicly affirm your standing in the social order!

          • Uncle Al

            Terahertz radiation mail reading saves us all by ending secrecy. What in a voting booth or mailbox requires secrecy other than treason? Terahertz radiation will empty the “basket of deplorables.”

          • OWilson

            “What in a voting booth or mailbox requires secrecy other than treason?”

            Very profound, and very prescient!

            (Wish I had come up with that one! :)

        • Uncle Al

          Yes, as a troika portmanteau word. Science and technology must be harnessed to support the State. Fit blinders, apply the whip.

          A psychopath is a sociopath with goals. The Social Justice solution is to make all society insane so that there is neither reward nor penalty to be gained from deviant behavior. Then, be in charge and collect commission.

          • Paul

            That really is all that it is about.
            Nice job of boiling it down succinctly.

          • Erik Bosma

            You sir, have this talent to be able to turn nonsense into a complicated message or to turn a complicated message into nonsense. Perhaps a bit of both? But you always leave me guessing. Kind of an intellectual Kurt Vonnegut Jr.
            Anyways, our session is over. That’ll be a $300 bill. This is when I tweak your nose and woo-hoo-hoo off into the distance like Daffy Duck.

          • Uncle Al

            “Best efforts will not substitute for knowledge.” W. Edwards Deming. Social Justice and the Sciences, Youtube v=pLFIxt2cK_0

    • Mehmet Arkın Gürbüz

      Good point if coming this message als o

  • Rixware

    Dear Discover,

    Please moderate your comments. Most of the comments in this thread have nothing to do with the subject of this post.

    Thank you.

    • OWilson

      You may have a point, but you set no example :)

    • Erik Bosma

      Perhaps you need understanding.

  • Mehmet Arkın Gürbüz

    We can goto Mars if that is possible. :)



Briefing you on the must-know news and trending topics in science and technology today.

See More


Discover's Newsletter

Sign up to get the latest science news delivered weekly right to your inbox!

Collapse bottom bar