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.
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.
The Anoto dot pattern can be printed onto almost any paper, using a standard printing process of at least 600 dpi resolution, and carbon-based black ink. The paper can be any shape or size greater than 2 mm to a side. The ink absorbs infra red light transmitted from the digital pen; the pen contains a receiver which interprets the pattern of light reflected from the paper. Other colors of ink, including non-carbon-based black, can be used to print information which will be visible to the user, and invisible to the pen.