Amplitude-Modulated Halftone Printing for Authentication
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Solution Overview
Problem
Existing methods fail to effectively distinguish high-quality original prints of multicolor images from their copies without altering the image data or adding visible features.
Innovation Solution
The method involves applying amplitude-modulated halftone printing in a detection zone, where individual tone values correspond to halftone planes of a halftone mountain, and modifying these planes for specific tone values to create a unique matrix image. This results in asymmetrical halftone element distributions that can be recognized in the original print but not in copies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional halftone printing is used, then image quality is maintained, but authentication against counterfeiting is insufficient
Solution Approach 1:
The patent applies asymmetry by modifying the halftone mountain structure to create asymmetric halftone element distributions. Specifically, for certain tone values, the halftone plane is modified so that a predetermined matrix image of halftone elements is assigned, creating asymmetric patterns that are difficult to replicate. This asymmetric structure serves as an authentication indicator that distinguishes original prints from counterfeits while maintaining visual image quality.
Solution Approach 2:
The patent implements local quality by applying the asymmetric halftone modification only in specific detection zones rather than throughout the entire image. The method modifies halftone planes for predetermined tone values in localized areas where authentication is needed, while leaving other areas with conventional halftone printing. This allows authentication functionality to be integrated without affecting the overall ease of manufacture for the complete printing process.
2Reliability
If authentication features are added to distinguish originals from copies, then security is improved, but visible markings or image alterations occur
Solution Approach 1:
The authentication indicators are embedded locally within the halftone structure of specific detection zones rather than as separate visible markings. By modifying the halftone plane assignments for predetermined tone values in localized areas, the authentication features become integrated into the image itself at a microscopic level, making them invisible to the unaided eye while maintaining the overall image appearance.
Solution Approach 2:
The patent transitions the authentication information from a visible two-dimensional surface feature to a microscopic structural dimension within the halftone element arrangement. The asymmetric distribution of halftone elements creates authentication indicators in the spatial arrangement dimension that are imperceptible visually but detectable through analysis of the halftone pattern structure, effectively adding an invisible layer of authentication.
3Measurement precision
If asymmetric halftone element distributions are used for authentication, then original print identification is enabled, but device complexity increases
Solution Approach 1:
The asymmetric halftone mountain structure is prepared and defined in advance during the prepress or RIP (Raster Image Processing) stage. The modified halftone planes for predetermined tone values are calculated and assigned before actual printing occurs. This preliminary preparation of the authentication-indicating halftone structure simplifies the printing process itself, as the asymmetric pattern is already embedded in the digital printing data rather than requiring complex mechanical or chemical processes during printing.
Data Source
AI summary
A method of printing authentication indicia by applying an at least amplitude-modulated halftone print in a detection zone to an object uses adjoining halftone cells, in each of which a halftone dot is printed from a matrix of printable halftone elements, individual tone values of the halftone print corresponding in each case to a halftone plane of a halftone mountain for a halftone dot. In this process, the assigned screen plane of the screen mountain is modified in the detection zone in a predetermined manner for a plurality of tone values of screen dots to be printed, so that a predetermined matrix image of the screen elements to be printed is assigned to it while the tone value of the print remains constant.