Show-through watermarking of duplex printed documents
US7286682B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Aug 31, 2000 |
| Grant date | Oct 23, 2007 |
| Priority date | — |
| Expiry date | Feb 6, 2023 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N1/32352
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A printing apparatus and method for duplex printing a document having a show-through watermark wherein the watermark is comprised of first and second images on both sides of the document. The images comprise stoclustic halftone screens having a substantially common registration wherein the second image is relatively shifted from the first image for forming an associated overlay pattern between the first and second images resulting in a recognizable pattern comprising the watermark upon illumination by a show-through light source. The watermark is unrecognizable from either image alone upon illumination from a front light source. The relative shifting can be implemented by either phase, frequency or angle shifting between the front and back side images.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.