| 摘要 |
The present application discloses a system, method and device for placing substantially invisible marks comprising alphanumeric characters, symbols, or bar codes, on a page using clear ink or toner, which may then be read by a spectrophotometer. Such substantially invisible marks are not viewable to the unaided eye of a human observer, do not distract a viewer, and allow the viewer to focus their attention on the printed matter and text of interest to the viewer. |
