Multispectral Watermark Using Metameric Inks for Document Security
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Solution Overview
Problem
Conventional security printing methods require separate infrared (IR) and ultraviolet (UV) watermarks to leverage both technologies, which occupy valuable space on documents and may conflict with aesthetics, while also necessitating expensive materials.
Innovation Solution
A multispectral watermark using a metameric pair of inks that appear as a single color/pattern under office lighting, becoming visible with IR cameras under UV light, with one ink reflecting more in the IR spectrum and allowing varying UV light exposure to fluorescing media, thereby combining IR and UV security features in a single design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate infrared (IR) and ultraviolet (UV) watermarks are used, then both IR and UV security features are provided, but valuable document space is occupied and aesthetics may be compromised
Solution Approach 1:
The patent combines separate IR and UV watermark functions into a single multispectral watermark layer. This is achieved by using spectral watermarks that can be viewed under different lighting conditions (visible light, UV, or IR) without requiring multiple separate watermark elements on the document, thus providing both IR and UV security features while conserving document space.
Solution Approach 2:
The spectral watermark is designed to serve multiple security functions simultaneously. A single watermark structure can be viewed under visible light for one type of verification, under UV light for another type of verification, and under IR for machine-readable verification, making the watermark universal and multi-functional rather than requiring separate dedicated watermarks for each verification method.
2Reliability
If separate infrared (IR) and ultraviolet (UV) watermarks are used, then both IR and UV security features are provided, but the document aesthetics may be compromised
Solution Approach 1:
The patent merges multiple security features into a single aesthetic watermark design. The spectral watermark appears as a unified visual element under visible light that maintains document aesthetics, while simultaneously encoding multiple spectral layers that can be revealed under different lighting conditions (UV, IR) for security verification, thus avoiding the aesthetic compromise of multiple separate watermarks.
3Reliability
If conventional specialty imaging techniques are used, then security marks are provided, but they conflict with overall document aesthetics
Solution Approach 1:
The patent uses spectral watermarks that utilize color and spectral properties to achieve security functionality. The watermark is designed to appear as a subtle visual element under visible light that maintains aesthetics, while containing spectral information that can be revealed or verified under different lighting conditions (UV excitation, IR reflection) without compromising the overall document appearance.
4Ease of operation
If UV watermark is used, then it is viewable with inexpensive UV flashlight, but resolution is limited compared to IR
Solution Approach 1:
The patent segments the watermark verification into different spectral channels. The UV component provides easy visual verification with inexpensive flashlights for basic authentication, while the IR component provides high-resolution machine-readable verification for precise reading. This segmentation allows each spectral channel to optimize for its specific verification method without compromising the other.
5Measurement precision
If IR watermark is used, then it provides better resolution and machine readable verification, but it requires separate infrastructure from UV
Solution Approach 1:
The patent merges UV and IR watermark functionality into a single spectral watermark structure. This allows verification systems to use either UV or IR infrastructure depending on the verification level needed, without requiring completely separate watermark elements. The combined approach reduces overall system complexity by sharing the watermark encoding structure while providing multiple verification pathways.
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 multispectral watermark enhances document security by being visible with IR cameras or UV light without increasing document size, using standard materials and maintaining aesthetics, while allowing for machine-readable verification and higher resolution encoding.
Implementation Method 1
one ink of the metameric pair of inks using more CMYK toners that reflect in the infrared spectrum as compared to the other ink
Implementation Method 2
allowing more of the ultraviolet light or less of the ultraviolet light to reach a fluorescing media upon which the multispectral watermark is rendered
Data Source
AI summary
A multispectral watermark and method for generating the multispectral watermark. A color pattern can be provided, which appears a single color/pattern under a first lighting condition. A watermark can be created based on the color pattern and under a second lighting condition comprising ultraviolet light, while the watermark is viewable with an infrared camera in an infrared spectrum. The watermark can be configured as a multispectral watermark with a metameric pair of inks with one ink of the metameric pair of inks using more CMYK toners that reflect in the infrared spectrum as compared to the other ink among the metameric pair of inks while simultaneously allowing more of the ultraviolet light or less of the ultraviolet light to reach a fluorescing media upon which the multispectral watermark is rendered.