Optical encoding
A substrate, such as a document of value, carries a design feature (F), which includes an array of repeating patterns with the patterns exhibiting discrete differences in one or more visual characteristics, for example, shape, color or optical responses, according to a predetermined pattern. The differences are, preferably, indiscernible to the unaided eye, but can be discriminated by an optical reading machine. In an alternatively preferred embodiment, the visual characteristics of each pattern represent 8- or 16-bit information.
1. An article, comprising:
a surface; and,
a design feature on said surface, said design feature having an array of patterns with a basic pattern of predetermined form repeated in identical shape and size through-out said array of patterns, said basic pattern comprising a plurality of elements with, at least, a portion of said plurality of elements comprising optically variable devices and with patterns of said array of patterns exhibiting discrete differences between one another, wherein corresponding said optically variable devices of said portion of said plurality of elements of said patterns are optical responses selected according to a predetermined code, whereby said design feature encoded with information is decodable upon reading said patterns and said plurality of elements thereof in a predetermined order.
2. The article according to claim 1 , wherein at least a portion of said optically-variable devices comprise diffraction gratings of selected grating angles.
3. The article according to claim 1 , wherein at least a portion of said optically-variable devices comprise diffraction gratings of selected spatial frequencies.
4. The article according to claim 1 , wherein at least a portion of said optically-variable devices comprise zone plates of selected focus levels.
5. The article according to claim 1 , wherein each pattern or said patterns comprise a plurality of sectors radiating from a center point.
6. The article according to claim 1 , wherein said array of patterns includes an additional pattern exhibiting at least one visual characteristic representing a key defining said predetermined code.
7. The article according to claim 1 , wherein said design feature includes a code associated with said design feature that determines said predetermined order in which said patterns are read.
8. The article according to claim 7 , wherein said code associated with said design feature further determines an order in which said plurality of elements of each said pattern are read.
9. A batch of articles, comprising:
a plurality of articles with each article of said plurality of articles comprising a surface having a design feature on said surface, said design feature comprising an array of patterns having a basic pattern of predetermined form repeated in identical shape and size throughout said array of patterns, said basic pattern of predetermined form comprising a plurality of elements with at least a portion of said plurality of elements comprising optically variable devices, and with patterns of said array of patterns exhibiting discrete differences between one another, wherein corresponding said optically variable devices of said plurality of elements of said patterns exhibit optical responses selected according to a predetermined code, whereby said design feature encoded with information is decodable upon reading said patterns and said plurality of elements thereof in a predetermined order;
a majority of said plurality of articles carrying an identical said array of patterns defining a first said predetermined code; and,
a minority of said plurality of articles carrying a corresponding said array of patterns defining a second said predetermined code.