Metameric Ink Pair for Copy-Resistant Infrared Security
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Solution Overview
Problem
Conventional infrared security marks in printed documents are often degraded or destroyed by copying, making it difficult to distinguish originals from copies, especially in cases where both the original and copy need to be valid, such as social security cards and veteran discharge papers.
Innovation Solution
A metameric pair of pattern inks is used, where one ink reflects more in the infrared spectrum than the other, with the less reflective ink having larger and less scattered patterns, and a common color is employed to create an infrared effect that survives copying, preventing modulation transfer function filtering and allowing the effect to remain visible with an IR camera.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional infrared security marks are used in printed documents, then the security feature is visible under IR illumination, but the effect is degraded or destroyed by copying
Solution Approach 1:
The patent changes the physical parameters of the ink particles by controlling their size (0.5-5 micrometers for first ink, 5-15 micrometers for second ink) and spatial distribution (scattered vs. less scattered patterns). These parameter changes enable differential modulation transfer function responses during copying, allowing the infrared effect to be preserved through multiple copies while maintaining visibility under IR illumination.
Solution Approach 2:
The patent uses a composite approach by combining two different inks with distinct particle size ranges and scattering characteristics. The first ink (smaller particles, more scattered) and second ink (larger particles, less scattered) work together to create an infrared mark that responds differently to the modulation transfer function during copying, enabling the effect to survive reproduction while remaining detectable by IR cameras.
2Illumination intensity
If special IR inks are used to create infrared security marks, then the infrared effect is strong and visible, but the copying cost increases and the effect may still degrade
Solution Approach 1:
The patent applies local quality by creating specific spatial patterns and distribution characteristics for each ink type within the document. The first ink is distributed in a more scattered pattern while the second ink forms larger, less scattered patterns. This local differentiation in pattern quality allows standard copiers to reproduce the mark with sufficient fidelity for security verification, making copying accessible while maintaining the infrared effect's visibility and strength.
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 infrared effect remains readable and secure through multiple copying processes, enhancing data hiding and verification capabilities while maintaining the security feature's integrity.
Implementation Method 1
a first pattern ink reflects higher in an infrared spectrum as compared to a second pattern ink among the metameric pair of pattern inks
Implementation Method 2
providing a metameric pair of pattern inks, wherein a first pattern ink reflects higher in an infrared spectrum as compared to a second pattern ink
Data Source
AI summary
Methods and system for creating an infrared effect that can survives copying, can involve providing a metameric pair of pattern inks, wherein a first pattern ink reflects higher in an infrared spectrum as compared to a second pattern ink among the metameric pair of pattern inks, wherein the second pattern ink is less reflective than the first pattern ink. For the second pattern ink that is less reflective than the first pattern ink, a pattern can be created for the second pattern ink that is larger and less scattered than an existing design for a pattern ink. A color of media can be used as a common color for the metameric pair of patterns and inks to create an infrared effect from the metameric pair of pattern inks that survives copying on the media.