Security Document Lens Reshaping for Complex Optical Effects
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Solution Overview
Problem
Current security document manufacturing methods, such as those using laser engraving through a lens pattern, are limited in the combinations of images that can be observed, making them vulnerable to counterfeiting due to restricted optical properties and limited design features.
Innovation Solution
A surface reshaping method is introduced that modifies the external surface of a security document by adding or reshaping lenses in a lens layer, using a laser to alter the profile of the lenses, creating different optical properties and enabling features like color shift, metallic shift, or secondary portraits, which are difficult to reproduce.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If laser engraving through a lens pattern is used for security features, then the security document can be manufactured with optical properties, but the combinations of images that can be observed are very limited
Solution Approach 1:
The security document is divided into multiple layers: a substrate, a coating layer with metallic particles, and a top layer with a lens pattern. This segmentation allows different functional elements to be optimized independently while combining to create complex optical effects that were not achievable with a single lens pattern approach
Solution Approach 2:
The patent embeds the coating layer with metallic particles between the substrate and the top layer with lenses. This nested structure allows the metallic particles to be positioned at specific depths within the document, creating additional optical dimensions that enable multiple image combinations through varying observation angles
2Ease of manufacture
If a lens layer with fixed lens pattern is used, then the manufacturing process is simplified, but the optical properties and design features are limited
Solution Approach 1:
The top layer is designed with lenses that have specific local optical properties, and the coating layer contains metallic particles with specific local arrangements. This local quality differentiation allows each region to contribute specific optical characteristics, enabling diverse design features like color shifts and metallic shifts while maintaining a manufacturable lens pattern structure
3Reliability
If the security document uses simple surface features, then it is easier to manufacture and observe, but it becomes vulnerable to counterfeiting
Solution Approach 1:
The security document combines multiple materials with different optical properties: a transparent or translucent top layer with lenses, a coating layer containing metallic particles suspended in a matrix, and a substrate. This composite structure creates complex optical effects including color shifts, metallic shifts, and depth-dependent image visibility that are difficult to replicate and provide strong anti-counterfeiting capabilities
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 method enhances the security document's difficulty in reproduction by modifying the optical properties and adding complex lens patterns, making it challenging to counterfeit, while allowing for designed features like color shifts and secondary portraits.
Implementation Method 1
a laser is used for reshaping the surface of the security document in the reshaping step. The laser modifies the profile of the surface
Implementation Method 2
The laser modifies the profile of the surface, or even of the lenses the case being such that at least one lens, or even each lens, has different slopes than another
Implementation Method 3
The lenses may have different radius, so the path of one incident light ray is modified, in comparison with the original surface shape. In case of addition of another lens, the laser modifies the surface so that it creates a bulge which forms a lens
Implementation Method 4
The reshaped surface, by adding a lens and/or modifying at least one lens of the lens layer, allows to obtain a designed color shift feature, or a designed metallic shift feature
Data Source
Figure 1~2
Figure 3~5
AI summary
Manufacturing method of a security document (1), comprising a personalization step (E2) which comprises a reshaping step in which a surface (32) of the security document (1) is reshaped; and security document comprising a top layer (30) comprising at least two lenses (31, 38) for providing a viewing angle dependent image and/or color changing effect, in which at least corresponding flanks (36,36', 37,37') of the at least two lenses (31, 38) of the top layer (30) have different shapes.