Security Paper with Invisible Raster Marking
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Solution Overview
Problem
Current methods for distinguishing original documents from copies are inadequate, as they often rely on visible security features that can be reproduced by copiers, making it difficult to prevent misuse and forgery.
Innovation Solution
A paper design featuring a marking printed with raster dots that is invisible on the original but becomes visible on copies, using grid dots of different sizes and distances for the marking and surrounding area, ensuring the marking is not visible to the human eye but can be resolved by copiers, and potentially incorporating a watermark or additional optical elements to enhance security.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a visible security feature is printed on the original document, then it can be seen by the human eye, but it can also be reproduced by copiers making it ineffective
Solution Approach 1:
The patent applies different dot sizes and spacings in different regions of the document. The identification marking uses larger dots with greater spacing that are invisible on the original but resolve clearly on copies, while the surrounding area uses smaller dots that remain invisible on both original and copy. This local differentiation creates the security effect without requiring visible features on the original document.
Solution Approach 2:
Instead of making the security feature visible on the original and hidden on the copy (traditional approach), the patent inverts this by making the security feature invisible on the original and visible on the copy. This is achieved by using dot patterns that are too small to be seen on the original but are enlarged and resolved by the copier's scanning and printing process.
2Measurement precision
If raster dots are used for the security feature, then it can be resolved by copiers, but it may become visible to the human eye on the original
Solution Approach 1:
The patent uses different dot characteristics for the identification marking versus the surrounding area. The identification marking uses larger dots (0.2-0.5mm) with greater spacing that can be resolved by copiers, while the surrounding area uses smaller dots (0.1-0.3mm) with tighter spacing that remain invisible to the human eye. This local quality differentiation allows the security feature to be copier-visible while remaining human-invisible on the original.
3Reliability
If different grid angles are used for marking and background, then security can be enhanced, but device complexity increases
Solution Approach 1:
The patent extracts the security function from complex multi-angle grid patterns and implements it through a simpler single-angle dot size differentiation system. By removing the need for multiple grid angles and using only dot size and spacing variations, the patent achieves security differentiation while significantly reducing printing and design complexity.
Data Source
AI summary
The paper (1) comprises an imprinted marking (2), which is invisible for the human eye and is visible on a copy of the paper produced on a photocopying apparatus, and a water-mark (5). The marking is imprinted on both sides of the paper by raster points (3). An area (4) surrounding the marking is printed on with raster points that is smaller than the raster points of the marking. The entire paper is printed on one side with raster points. The ratio of the raster point size to the distance between two raster points is identical. The both raster points have same optical brightness. The paper (1) comprises an imprinted marking (2), which is invisible for the human eye and is visible on a copy of the paper produced on a photocopying apparatus, and a water-mark (5). The marking is imprinted on both sides of the paper by raster points (3). An area (4) surrounding the marking is printed on with raster points that is smaller than the raster points of the marking. The entire paper is printed on one side with raster points. The ratio of the raster point size to the distance between two raster points is identical. The both raster points have same optical brightness. The water-mark is brought into the paper after the paper production. A pattern is intended, which is recognized by a copier or a scanner.