| 摘要 |
Disclosed is a machine readable cord of a set of printed markings, wherein each printed marking of the set has a predetermined height on a substrate and represents a predetermined date value, wherein printed markings having a same predetermined height represent a same data value, and wherein printed markings representing different data values have different heights. Also disclosed is a system for embedding and recovering information on a substrate, including an image forming device containing at least one marking material, wherein the image forming device receives data, corresponding to the information, for forming machine readable code in accordance with claim 1 on an image receiving substrate, and forms an image including the machine readable code on the image receiving substrate with the at least one marking material, and a document reading device comprising a reader that detects the differences in height among the different printed markings of the machine readable code.
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