Digital paper

Digital paper, also known as interactive paper, is patterned paper used in conjunction with a digital pen to create handwritten digital documents. The printed dot pattern uniquely identifies the position coordinates on the paper. The digital pen uses this pattern to store the handwriting and upload it to a computer.

The paper

The dot pattern is a kind of two dimensional barcode; the most common is the proprietary Anoto dot pattern. In the Anoto dot pattern, the paper is divided into a grid with a spacing of about 0.3 mm, a dot is printed near each intersection offset slightly in one of four directions, a camera in the pen typically records a 6 x 6 group of dots. The full pattern is claimed to consist of 669,845,157,115,773,458,169 dots, and to encompass an area exceeding 4.6 million km² (this corresponds to 73 trillion unique sheets of letter-size paper).

The complete pattern space is divided into various domains. These domains can be used to define paper types, or to indicate the paper's purpose (for example, memo formatting, personal planners, notebook paper, Post-it notes, et cetera).