Many of the books are scanned using a customized Elphel 323 camera at a rate of 1,000 pages per hour. A patent awarded to Google in 2009 revealed that Google had come up with an innovative system for scanning books that uses two cameras and infrared light to automatically correct for the curvature of pages in a book. By constructing a 3D model of each page and then "de-warping" it, Google is able to present flat-looking pages without having to really make the pages flat, which requires the use of destructive methods such as unbinding or glass plates to individually flatten each page, which is inefficient for large scale scanning.