Abstract: A system for printing glyph frames around known obstructions. All frames in an area are determined to be obstructed or unobstructed, based on their location with respect to other printed areas. The unobstructed locations can be numbered and glyph data printed within. In the alternative, the good locations can be numbered modulo some number much smaller that the number of available locations to provide redundancy. The unobstructed locations can be stored in either the sync lines or in the data area of other locations known to be unobstructed. Also, the frame itself can be identified as obstructed or unobstructed to provide more redundancy.

Abstract: A specific bit pattern (or set of bit patterns) that have particular frequency and length requirements is used to remove low-frequency, visually observable structure from rendered embedded digital data. In use, the pattern is replicated enough times to be able to XOR with the data before rendering as glyphs, or the like. On decoding (reading), the read data is XOR'd again to recover the original data.

Abstract: The glyphs of self-clocking glyph codes are written on regular hexagonal or pseudo-hexagonal lattice-like patterns of centers to reduce the risk of interglyph interference during the read process while also enabling the glyphs to be packed more densely while maintaining a given center-to-center spacing between them.