MIT has designed a new imaging system that can see through the book while it is still closed. ‘Don’t judge a book by its cover’ they say well now you can. The tiny gaps of air between the pages and the radiation band between microwaves and infrared known as terahertz radiation come into play to achieve this milestone. The difference between ink and blank paper can be distinguished by terahertz radiation in a much better way than the x-rays and with a better depth resolution than the ultrasound.
An algorithm measures the distance between the individual pages while the standard terahertz camera fires ultra-short bursts of radiations and simultaneously measures the time it took to bounce back. This system has been developed by the Georgia Tech and MIT. To extract information about the chemical properties of the reflecting surface the system armed with that data uses two diverse measures of the reflections energy. Throughout this process, the system makes it best efforts cancel the noise in the data. To identify the distorted images as letters the system uses a different algorithm.
While testing the system prototype the researchers used a stack of papers with a single letter written in each and it recognizes the first nine sheets.