Researchers from the Massachusetts Institute of Technology (MIT) and their colleagues over at the Georgia Institute of Technology are devising an imaging system that will allow the reading of closed books.
In a study published in the journal Nature Communications, the researchers detailed the prototype system they have designed, which has so far been tested on a stack of papers. Though still in the prototype stage, New York's Metropolitan Museum has shown interest in the technology, which can be used to examine the contents of antique books without damaging the object. Some artifacts, after all, are so old that just lifting the cover a bit will result in disintegration.
According to the researchers, the imaging system can also be used for analyzing materials in thin layers, like coatings on pharmaceuticals or machine parts.
For the imaging system, MIT researchers were in charge of developing algorithms for acquiring images from the individual sheets while their Georgia Tech colleagues created the algorithm that interpreted incomplete or distorted images as individual letters.
Barmak Heshmat, corresponding author for the study, said the imaging system they devised is "actually kind of scary" because it can be used to get through letter certification on websites like captchas.
The imaging system relies on terahertz radiation, an electromagnetic radiation band between infrared and microwave light. It's commonly used for security screening as different chemicals absorb different terahertz radiation frequencies at varying degrees, resulting in distinct frequency signatures. For the purposes of imaging, terahertz radiation is preferred over X-rays, for instance, because it features frequency profiles that can differentiate between blank paper and ink.
The prototype imaging system features a standard terahertz camera emitting ultrashort bursts of radiation. The camera also has built-in sensors so it's able to detect the reflections of the radiation. From the time the reflections arrive, the algorithms kick in to assess the distance between the pages of the book being imaged.
Most of the radiation either gets reflected or absorbed by the book, but some do bounce around, resulting in false signals. To address this, the MIT algorithm has also been designed to filter out the "noise."
So far, the prototype can work with up to 20 pages of paper. However, distortions are far too great after page nine, so that's the current threshold for the researchers.
Terahertz imaging is a relatively new technology, but it holds a lot of promise. Heshmat and colleagues are working on fine-tuning their prototype, aiming for deeper penetration by improving the power of radiation sources and accuracy in the sensors.