Book lovers: Scientists have devised a way to read without cracking a volume’s spine or risking paper cuts (and no, we’re not talking about e-books). The new method uses terahertz radiation — light with wavelengths that are between microwave and infrared waves — to view the text of a closed book. The technique is not meant for your average bookworm, but for reading rare books that are too fragile to open.
Barmak Heshmat of MIT and colleagues started small, with a nine-page book of thick paper that had one letter inked on each page. By hitting the book with terahertz radiation and looking at the reflected waves, the scientists could read the letters within.
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Letters on pages 7 through 9 of a closed book are decoded using terahertz radiation. After isolating the reflected radiation from each page, the technique selects the frequency of radiation that provides the best contrast between ink and paper. An algorithm decodes the letters and then their locations inside the book.
Differences in the way the radiation interacts with ink and paper allowed the researchers to pick out shadowy outlines of the letters, and a letter-recognition algorithm automatically decoded the characters. The scientists could tell one page from another by using precise timing information: On the later pages, the waves penetrated deeper before reflecting and, therefore, took longer to return.
Historians also may be able to use the technique to find an artist’s signature hidden beneath layers of a painting. Sneaking into your sister’s locked diary is another story.