Secure Image Generation via Multi-Color Rasterization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for generating trichromatic fluorescent images in security documents, such as passports and ID cards, lack security due to reliance on publicly available halftone rasterization techniques, resulting in reduced spatial resolution and inability to meet security requirements.
Innovation Solution
A method involving the separation of a multi-color input image into mono-color base images, each subjected to a rasterization process using non-identical two-dimensional threshold functions, which are then combined to create a secure image with complex rasterization patterns, making it difficult to reproduce.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard halftone rasterization is used for trichromatic fluorescent images, then the images have beautiful appearance, but they lack security because the technology is publicly available
Solution Approach 1:
The patent segments the standard halftone rasterization process into multiple distinct threshold functions (first, second, third threshold functions) with different characteristics. Each function processes different aspects of the image data, creating a multi-layered rasterization approach that increases complexity and security while maintaining visual quality.
Solution Approach 2:
The patent combines multiple rasterization results from different threshold functions to create a composite secure image. This composite approach integrates the outputs of several processing stages, making the final image secure against reproduction while maintaining the desired visual appearance.
2Manufacturing precision
If juxtaposed halftoning is used to avoid quenching effects, then colorants can be printed side by side, but spatial resolution is reduced and image details are lost
Solution Approach 1:
The patent introduces dynamic element selection where the choice of which threshold function to apply varies based on local image characteristics and position. This dynamic approach allows the system to optimize between colorant placement accuracy and spatial resolution preservation depending on the specific region being processed.
Solution Approach 2:
The patent changes multiple parameters including threshold values, function types, and processing conditions across different stages. By varying these parameters strategically, the system achieves both accurate colorant placement and preserved spatial resolution that would be impossible with a single fixed approach.
3Ease of manufacture
If a uniform rasterization matrix is used across the entire image, then the process is simple and automated, but the image lacks complexity required for secure documents
Solution Approach 1:
The patent applies the principle of local quality by using different threshold functions for different regions or aspects of the image processing. Each local region can be processed with the most appropriate function, creating overall complexity and security while maintaining automated operation through systematic local decisions.
Solution Approach 2:
The patent employs periodic action by cycling through multiple threshold functions in a systematic sequence. This periodic application of different processing stages creates complex patterns that are secure while the systematic nature maintains ease of automated manufacture.
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A secure image for a security document is generated by performing a rasterization process for each of a plurality of mono-color base images using a plurality of different threshold functions. For each base image, the plurality of threshold functions cover different intensity regions and result in a complex rasterization pattern depending on the intensity of the input image. The resulting binary images obtained by the rasterization process are combined using offset printing with fluorescent inks of different colors, to result in a multi-color fluorescent output image including a plurality of different complex rasterization patterns.