How does dot paper work?
The camera located at the tip of the Livescribe smartpen takes a continuous series of photographs of 6 x 6 dots, spaced 0.3mm apart, creating images of 1.8 x 1.8mm grids of 36 dots. The camera takes 72 snapshots per second, sufficient to capture and recreate handwriting. Each picture of these dots is decoded by software in the smartpen to provide an (x,y) coordinate pair, telling the smartpen exactly where the smartpen tip is on any given page.
The smartpen's location, derived from the (x,y) coordinates, is interpreted by smartpen software, and mapped to an "application" in the smartpen. The camera does not see ink written by a user, nor does it see artwork on a page. Rather, the smartpen tracks and remembers where ink is written, and knows the coordinates of items such as buttons.