Floating Image Security Laminates Multi-Focal Microlens Arrays
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Solution Overview
Problem
Current security documents with microlens sheeting are vulnerable to tampering as the focal planes of the microlenses are all produced within one layer, making it possible for counterfeiters to reuse the layer in creating fake documents.
Innovation Solution
A transparent microlens sheeting with a first microlens array having a focal plane coplanar to one broad face and a second microlens array with a focal plane beyond the sheeting, along with a microimage array on the opposite broad face, creating a composite image that appears to float above or below the sheeting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If all microlenses are produced within one layer, then the manufacturing process is simplified, but the tamper-resistance of the security document is reduced
Solution Approach 1:
The microlens array is divided into multiple segments with different focal lengths, where each segment focuses light at a different depth. This segmentation prevents counterfeiters from reusing the entire layer, as the multi-focal-plane structure cannot be replicated by simple layer removal and reapplication.
Solution Approach 2:
The patent extends the focal depth dimension by creating microlenses with varying focal lengths within the same layer. This adds a depth dimension to the optical structure, making the security feature three-dimensional in optical space rather than two-dimensional, thereby preventing simple replication.
2Reliability
If multiple microlens arrays with different focal lengths are integrated, then tamper-resistance is enhanced, but the device complexity increases
Solution Approach 1:
Multiple microlens arrays with different focal lengths are merged into a single integrated layer. This combining approach achieves the security benefit of multi-focal-plane complexity while avoiding the need for multiple separate physical layers, thus reducing overall structural complexity compared to stacked multi-layer designs.
Solution Approach 2:
A single microlens layer performs multiple functions by incorporating microlenses with different focal lengths within the same structure. This multi-functional design eliminates the need for separate layers for different focal planes, reducing device complexity while maintaining enhanced tamper-resistance.
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 solution enhances the tamper-resistance of security documents by making it difficult for counterfeiters to reuse the microlens layer, while maintaining the visual effect of floating images for authentication.
Implementation Method 1
a two-dimensional array of microlenses with well-registered high-resolution microimages located at the focal depth of the microlenses
Data Source
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AI summary
A transparent microlens sheeting, a security article including a microlens sheeting, and method for producins a security article having a transparent microlens sheeting. The microlens sheeting has a layer of microlenses, the layer having a first broad face and a second broad face, and containing a first microlens array (107) and a second microlens array (109) on the first broad face of the layer of microlenses, wherein the first microlens array has a focal plane essentially coplanar to the second broad face and the second microlens array has a focal plane that lies beyond the layer of microlenses. The microlense sheeting further contains a first microimage array comprising a plurality of individual at least partially complete images (111) located on the second broad face of the microlens layer and associated with each of a plurality of the microlenses of said first microlens array, whereby a composite image, provided by the individual images, appears to the unaided eye to be floating above or below the sheeting, or both when the first microimage array is viewed through first microlens array.