Unidirectional Opacity Watermark for ID Card Authentication
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Solution Overview
Problem
Existing watermark technologies in identification cards face challenges in achieving edge definition and detail while being difficult to distinguish from other visible markings, requiring large areas and being prone to interference from other markings on the card.
Innovation Solution
A unidirectional opacity watermark is created by forming a laminar assembly with a first optically opaque layer, an optically transparent inner layer, and a second optically opaque layer, where through-holes are filled with material from the transparent layer, allowing light transmission in a single direction, enabling visibility from one side but not the other, thus providing clear authentication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If dark text or image is printed in opaque white core with large area, then watermark visibility is improved, but edge definition and detail are worsened
Solution Approach 1:
The patent applies local quality by creating regions of different optical properties within the watermark layer. The watermark consists of opaque regions (for the mark itself) and transparent regions (for background detail), allowing both visibility and fine detail to coexist in different local areas of the same layer.
Solution Approach 2:
The patent employs asymmetry by making the watermark visible in only one direction (unidirectional visibility). The watermark layer is positioned and configured so that it is visible when viewing from the front side but invisible when viewing from the back side, creating an asymmetric optical property that enhances visibility without requiring large area marks.
2Illumination intensity
If watermark uses large area to be distinguished from other markings, then visibility is improved, but interference from other visible markings is worsened
Solution Approach 1:
The patent resolves interference issues by assigning different optical qualities to different regions. The watermark area has opaque characteristics for distinguishability, while surrounding areas maintain transparency, allowing the watermark to be clearly distinguished without the need for large area coverage that would cause interference with other card markings.
Solution Approach 2:
The patent uses optical property changes (from transparent to opaque) to differentiate the watermark from other markings. By controlling the optical density and transparency characteristics of the watermark layer, the watermark becomes visually distinct from other markings on the card without requiring it to occupy a large area.
3Illumination intensity
If traditional bidirectional watermark is used, then visibility from both sides is improved, but anti-counterfeiting capability is worsened
Solution Approach 1:
The patent fundamentally improves anti-counterfeiting capability by creating asymmetric visibility - the watermark is visible from the front side but invisible from the back side. This unidirectional optical property makes the watermark much harder to replicate than traditional bidirectional watermarks, as counterfeiters cannot easily reproduce the direction-dependent optical characteristics without sophisticated manufacturing processes.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The unidirectional opacity watermark offers enhanced anti-counterfeiting measures with crisp detail and easy authentication, while being difficult to simulate, as it is visible under specific lighting conditions but not others, improving the visibility and authenticity verification of identification cards.
Implementation Method 1
light is visibly transmitted in a single direction through the plurality of through-holes
Implementation Method 2
heating the stack of layers to fuse the optically transparent core layer between the first optically opaque layer and the second optically opaque layer
Data Source
AI summary
A laminar assembly including a first optically opaque layer defining a plurality of through-holes, a second optically opaque layer, an optically transparent inner layer between the inner surface of the first optically opaque layer and the inner surface of the second optically opaque layer, and a preprinted layer proximate the outer surface of at least one of the first and second optically opaque layers. The plurality of through-holes is at least partially filled with material from the optically transparent inner layer, and light is visibly transmitted in a single direction through the plurality of through-holes. Unidirectional opacity watermarks defined by the plurality of through-holes in the laminar assembly provide advantageous anti-counterfeiting measures, and are easy to view and authenticate, yet difficult to simulate.