Digital paper

The digital pen uses this pattern to store handwriting and upload it to a computer.

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).

Other colors of ink, including non-carbon-based black, can be used to print information that will be visible to the user, and invisible to the pen.

With a typical CMYK color laser printer, it's possible use full-color text and graphics that cover the entire page by avoiding using black (i.e., under color removal is turned off) and instead use only Cyan, Magenta, Yellow, or any combination -- which are ignored by the pen -- and using the black (K component) only for the Anoto pattern.

Redundant glyph marks support recovering the correct 2D location and angular orientation, even in the presence of overprinted text and line art.

Simplified principle of the Anoto digital pen.
The camera identifies a 6×6 matrix of dots, each displaced from the blue grid (not printed) in one of 4 directions.
The combinations of relative displacements of a 6-bit de Bruijn sequence between the columns, and between the rows gives its absolute position on the digital paper.