As the computerization of documents proceeds, security of the printed documents becomes more important. Recent copiers have such high performance that an illegal copy of a confidential document or certificate, for example, may cause trouble. In order to solve this problem, we have developed embedded pattern printing technology together with copy guard technology.
With embedded pattern printing technology, when a document is printed out, an "embedded pattern" of hidden character strings is incorporated in the document. For example, warnings such as "Do Not Copy" or "Copying Prohibited" can be pre-embedded as character strings in documents and when an attempt is made to copy the document, the embedded information appears conspicuously on the document when it is output on the copier.
Figure 1: Protecting unauthorized copy with the embedded pattern printing technology
Copy guard technology is a technology that further enhances embedded pattern printing technology by automatically detecting documents with embedded patterns while they are being copied on a copying machine. Using this technology, if an attempt is made to copy documents containing the embedded pattern, the images of the document pages that are being copied are destroyed (turned to a gray plane). Therefore, leaking of confidential information is prevented.
Figure 2: Printed document security with the copy guard technology
The embedded pattern printing technology makes warning strings such as "Do Not Copy" indiscernibly embedded in the background pattern consisting of big and small dots.
Until now, special papers, such as security paper with embedded patterns, have been used for various documents and certificates as a way to prevent illegal copies. However, embedded pattern printing technology is unique in that it can be used with plain paper, thus eliminating the time and effort required for preparing pre-printed security paper. Beyond that, it also offers the advantage of allowing the character strings embedded in the documents as warning messages to be freely designed.
Consistent with copy guard technology, special patterns have been developed to distinguish the embedded patterns used for document security from the dot patterns contained in ordinary documents so as to prevent them from becoming mixed up. We can design such special patterns because we have great experience of document image processing.
In addition, a high-speed image processor is incorporated in high-speed copiers in order to detect illegal copying without slowing the processing speed of the copier. This image processor is also made by Ricoh.