Micro-refractive Image for Forgery-Resistant Certificates
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Solution Overview
Problem
Conventional refraction images used in certificates of authenticity lack forgery-proofness due to their coarse structure, which can be easily replicated, and existing manufacturing methods limit the fineness of lens structures to a few 1/10 mm, resulting in inadequate security features.
Innovation Solution
A micro-refractive image is created using a substrate with a periodic line pattern and a lens structure made of cylindrical lenses, produced through advanced offset printing and intaglio processes, achieving a high-resolution, fine structure that is difficult to replicate, with lenses aligned to match the line pattern and having heights that are at least half the period width, allowing for complex optical effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional refraction images are used with extruded transparent plastic or mechanical deformation, then the manufacturing process is simple, but the lens structure fineness is limited to a few 1/10 mm resulting in coarse structure that is easy to replicate
Solution Approach 1:
The patent changes the manufacturing parameters by transitioning from conventional extrusion or mechanical deformation methods to laser beam writing technology. This enables the creation of lens structures with fineness in the micrometer range (e.g., 5-50 μm), dramatically improving the precision and forgery-proofness of the refraction image while maintaining manufacturing feasibility through automated laser processes
Solution Approach 2:
The patent replaces mechanical manufacturing methods (extrusion, mechanical deformation) with a laser-based optical system. The laser beam writes the lens pattern directly onto the transparent substrate, eliminating the need for mechanical contact tools and enabling much finer feature sizes that were previously unachievable with mechanical methods
2Manufacturing precision
If lens structures are made by extruding transparent plastic or mechanical deformation, then the manufacturing method is conventional and simple, but the lens width cannot be smaller than a few 1/10 mm limiting the line pattern fineness
Solution Approach 1:
The patent substitutes mechanical manufacturing processes with laser beam writing technology. The laser directly writes the lens pattern onto the transparent substrate with precision in the micrometer range, eliminating the constraints of mechanical tool sizes and enabling lens widths of 5-50 μm that were previously unachievable
Solution Approach 2:
The patent fundamentally changes the manufacturing parameters by using laser energy to locally modify the transparent substrate's refractive index or create physical structures. This enables precise control of lens dimensions at the micrometer scale, transforming the achievable feature size parameter from millimeter-range (conventional) to micrometer-range (laser-based)
3Reliability
If a fine line pattern with many tracks of elementary printing dots is used, then the security against forgery is improved, but the manufacturing complexity increases due to the need for high precision offset printing and intaglio processes
Solution Approach 1:
The patent replaces complex multi-step printing processes (offset printing combined with intaglio) with a single-step laser beam writing process. The laser directly creates the fine line pattern and lens structure in one operation, achieving micrometer-scale precision without requiring the coordination of multiple printing systems or intermediate steps
Solution Approach 2:
The patent merges the functions of creating the line pattern and forming the lens structure into a single laser writing process. Instead of separately printing the line pattern and then applying the lens structure through intaglio, the laser simultaneously creates both features in one pass, simplifying the manufacturing process while maintaining high security
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 micro-refractive image provides a high level of security against forgery, as the fine structure and precise alignment of lenses make it nearly impossible to replicate, and the combination of offset and intaglio printing techniques allows for a wide range of optical effects at low cost, enhancing the security features of certificates of authenticity.
Implementation Method 1
Refraction images consist of a periodic line pattern applied to a substrate and a lens structure covering the line pattern made of cylindrical lenses parallel to the lines of the lens pattern. Depending on the viewing angle at which the periodic line pattern is seen through the lens structure, different lines are visible in each period of the line pattern
Data Source
Figure 1~2a
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AI summary
4 µm A substrate comprises a periodic line pattern covered by a periodic line structure consisting of cylindrical lenses parallel to a line pattern lenses. The period of the line structure corresponds to the period of the line pattern. The lenses are preferably aligned with the lines of the line pattern. The lines consist of elementary printing points or image points (pixels). The number of elementary printing points in a period is equal to or greater than 4 and equal to or less than 16. The height of the cylindrical lenses on apex corresponds to at least a half width of a period and at most to the width of the line pattern width. A modern offset printing method, for example used for security printing (for example, for banknotes) makes it possible to attain the impression accuracy about 4 µm. The elementary printing points are selected such that they are slightly greater than an attainable printing accuracy. The realistic quadriform elementary printing points have a lateral length of 4 to 8 µm. For minimum requirements with regard to possibilities of the line pattern embodiment, two lines per period are sufficient. Each line must consist of at lest two elementary printing points, thereby corresponding to a period width of about 40 µm. In the corresponding line structure, individual cylindrical lenses have a height on apex slightly greater than the half width of the period. The inventive fine lens structures can be produced by printing a transparent mass by means of an intaglio printing method or by stamping of the transparent mass by an intaglio-engraving plate. The thus produced micro-refraction image is particularly suitable for an authenticity certificate.