Judging a book by its cover might not be a wrong thing to do pretty soon, if a technology recently designed by a group of researchers from MIT becomes common. Barmak Heshmat, a research scientist at MIT Media Lab and his team have recently tested this prototype technology with a stack of papers, each having a letter printed on its surface. The machine was able to correctly identify up to 9 layers of letters.
“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,” says Barmak. He also adds that this technique can be used to analyze any kind of material that is arranged in multiple thin layers.
The team of researchers includes Ramesh Raskar, an Indian origin associate professor of media arts and sciences at MIT. Raskar is a former student of College of Engineering, Pune. Also part of the group is Albert Redo Sanchez, a research specialist in the Camera Culture group at the Media Lab.
The method uses two algorithms - one that retrieves the images from the individual layers, and another that tries to decipher those images as readable text. While excited about their progress, Heshmat also states concern about the method being used to defeat captchas on websites.
The core technology behind this method is terahertz radiation, which has multiple advantages over other surface-penetrating waves like X-Ray and sound waves. Since different material absorbs different frequencies of terahertz radiation up to different degrees, this makes it an ideal choice for differentiating between blank paper and ink printed onto it. It uses the refractive property of air trapped in between the pages of the book (about 20 micrometer thick) by shooting short bursts of terahertz radiations into the book, and reading the time it took for it to be reflected back to the sensor.
While distance information is available upto 20 pages, the weakness of the signal after 9 pages and the noise that creeps in makes it unreadable. The researchers have said that terahertz technology is still in its early days, and with increased sensor accuracy and stronger radiation, better results are definitely achievable.
"So much work has gone into terahertz technology to get the sources and detectors working, with big promises for imaging new and exciting things,” says Laura Waller, an associate professor of electrical engineering and computer science at the University of California at Berkeley. “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!".
Read the detailed explanation of the method here.