A group of researchers from MIT have discovered a new method for reading through the pages of a closed book. Using terahertz (THz) imaging and a number of complex and carefully developed algorithms – judging a book by its cover is now possible.
Barmak Heshmat, contributing researcher, shares that the idea was originally inspired by research from another team at MIT where terahertz waves were used to detect and identify letters through an envelope. Taking this concept one step further, the group set out to see if they could push the detection capabilities and read through closed books in a non-invasive manner. To do so, three primary issues had to be addressed: spacial resolution, spacial contrast, and occlusion.
The team developed the new method, using terahertz radiation, to overcome these common bottlenecks to current imaging technologies. Terahertz radiation exists in between the microwave and infrared frequencies, and is unique in that it reacts differently to various chemical substrates such as ink. Using a standard THz camera with built in sensor (to detect reflections), short bursts of radiation are pulsed through the book, the frequency signatures of each letter are emitted by the ink and then processed using complex algorithms developed by the team to identify the letters on the page.
The result is a successful, non-invasive penetration allowing the team to view nine pages deep. At present, there is not enough power and signal to noise ratio to see beyond that. However, with further development of the young terahertz imaging technology the team anticipates that a deeper penetration of more than nine pages should be possible.
“So much work has gone into terahertz technology to get the sources and detectors working, with big promises for imaging new and exciting things. 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!”
This new technology may prove useful in applications such as analyzing historic items such as antique books or doctrines. The system also shows potential for analyzing materials that are comprised of thin layers such as coatings on machine parts. For more information, the research paper, ‘Terahertz time-gated spectral imaging for content extraction through layered structures’, was recently published in the journal Nature Communications online on September 9, 2016.
