Security Feature Pixel Correction for Micro-Optic Pitch Drift
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Solution Overview
Problem
Micro-optics in security documents suffer from pitch drift due to mismatches between printed images and optical elements, leading to inconsistent animations and visual irregularities when tilted, as precise copying of these features is difficult.
Innovation Solution
A method to correct pitch drift by adding or removing pixels in a printed image, calculating drift values, and randomly selecting locations for corrections to minimize visual discrepancies, using techniques such as segmenting rows and columns and employing virtual pixels to maintain image quality and prevent grid formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an array of optical elements is used overlying a printed image, then security features with micro-optics are achieved that are difficult to copy, but pitch drift occurs due to mismatch between pixels and optical elements causing visual irregularities
Solution Approach 1:
The patent applies preliminary action by pre-calculating drift values for each pixel position based on expected manufacturing variations, and pre-determining which pixels to add or remove before the actual printing and assembly process. This anticipatory correction ensures that even when pitch drift occurs during manufacturing, the visual irregularities are minimized because the correction pattern was already optimized in advance.
Solution Approach 2:
The patent changes the parameter of pixel density distribution across the printed image by selectively adding or removing pixels at specific locations based on calculated drift values. This parameter modification compensates for the mismatch between the printed image grid and the optical element array, reducing visual irregularities while maintaining the overall security feature functionality.
2Manufacturing precision
If pixels are added or removed to correct pitch drift, then visual consistency is improved, but the complexity of the design process increases
Solution Approach 1:
The patent segments the printed image into a grid of individual pixel locations and processes each location independently by calculating drift values and determining whether to add or remove pixels at each segment. This segmentation approach breaks down the complex global optimization problem into manageable local decisions, making the overall process more systematic and less complex.
Solution Approach 2:
The patent applies self-service by implementing an automated algorithm that automatically calculates drift values, determines correction locations, and generates the corrected pixel pattern without requiring manual intervention. This self-automating approach reduces design complexity by eliminating the need for manual pixel-by-pixel adjustment while achieving precise pitch drift correction.
3Manufacturing precision
If systematic pixel corrections are applied, then pitch drift is reduced, but grid patterns of corrections may form causing visual artifacts
Solution Approach 1:
The patent introduces asymmetry into the correction pattern by using random offset values when determining which pixels to add or remove. Instead of applying a systematic uniform correction pattern that could create visible grids, the random asymmetric adjustments distribute corrections more evenly across the image, preventing the formation of regular grid patterns that would create visual artifacts.
Solution Approach 2:
The patent inverts the conventional approach by not trying to make every pixel align perfectly with the optical element grid, but instead deliberately allowing some controlled misalignment through random offset selection. This inversion of the perfection-seeking approach actually reduces visible artifacts by creating more natural, less patterned correction distributions.
Data Source
AI summary
Methods for designing and producing a security feature are provided. In general, the present disclosure provides methods of designing a printed image in a security feature, the security feature comprising an array of optical elements overlaying the printed image, wherein the printed image comprises a two dimensional matrix of rows and columns of pixels, the method comprising; correcting for a mismatch between the pixels of the printed image and the array of optical elements by doing one or more of: adding one or more pixels; removing one or more pixels; and moving one or more pixels.