books were placed in a custom-built mechanical cradle that adjusted the book spine in place while an array of lights and optical instruments scanned the two open pages. Each page would have two cameras directed at it capturing the image, while a range finder LIDAR overlaid a three-dimensional laser grid on the book's surface to capture the curvature of the paper. A human operator would turn the pages by hand, using a foot pedal to take the photographs. With no need to flatten the pages or align them perfectly, Google's system not only reached a remarkable efficiency and speed but also helped protect the fragile collections from being over-handled. Afterwards, the crude images went through three levels of processing: first, de-warping algorithms used the LIDAR data fix the pages' curvature. Then, optical character recognition (OCR) software transformed the raw images into text, and, lastly, another round of algorithms extracted page numbers, footnotes, illustrations and diagrams. 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. Google decided to omit color information in favour of better spatial resolution, as most out-of-copyright books at the time did not contain colors. Each page image was passed through algorithms that distinguished the text and illustration regions. Text regions were then processed via OCR to enable full-text searching. Google expended considerable resources in coming up with optimal compression techniques, aiming for high image quality while keeping the file sizes minimal to enable access by internet users with low bandwidth. Website functionality For each work, Google Books automatically generates an overview page. This page displays information extracted from the book—its publishing details, a high frequency word map, the table of contents—as well as secondary material, such as summaries, reader reviews (not readable in the mobile version of the website), and links to other relevant texts. A