Micro-optical Device Array with Non-centered Optical Axes for Security
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Solution Overview
Problem
Current security document technologies, such as banknotes, are challenging to reproduce and verify authenticity due to the ease of counterfeiting, as existing optical encoding techniques can be replicated with relative simplicity.
Innovation Solution
A complex transparency device comprising a periodic two-dimensional network of micro-optical devices with non-centered optical axes and micro-images, where each micro-image is subdivided into thumbnails, creating a multiscopic effect that requires specific viewing angles to reveal recognizable information or visual effects, making unauthorized reproduction difficult.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional optical encoding techniques are used in security documents, then the implementation is simple and cost-effective, but the documents become easy to counterfeit
Solution Approach 1:
The patent divides the optical encoding system into multiple independent components: a periodic array of micro-optical devices (lenses or gratings) and a separate micro-image array with non-periodic positioning. Each component alone appears random or meaningless, but their combination produces the encoded information, significantly increasing counterfeiting difficulty while maintaining manufacturing feasibility through modular production
Solution Approach 2:
The patent introduces asymmetry by positioning the micro-images non-periodically relative to the periodic micro-optical device array. This asymmetric arrangement creates a unique optical path configuration that is difficult to replicate, as forgers would need to precisely reproduce both the periodic structure and the specific non-periodic offsets, thereby enhancing security without requiring overly complex manufacturing processes
2Reliability
If micro-images are positioned periodically in the array, then the manufacturing process is simplified, but the security verification becomes easier to replicate
Solution Approach 1:
The patent employs preliminary action by pre-positioning the micro-images at specific non-periodic offsets relative to the periodic micro-optical device array during manufacturing. This pre-established asymmetric configuration ensures that only the authentic document will produce the correct optical encoding when viewed through the micro-optical devices, while maintaining a manageable manufacturing process through template-based alignment procedures
3Ease of manufacture
If all micro-optical devices have centered optical axes, then the device structure is simpler and easier to manufacture, but the optical encoding capability is reduced
Solution Approach 1:
The patent applies local quality by allowing the micro-optical devices to have non-centered optical axes specifically where needed to achieve the desired optical encoding, rather than requiring all devices to be identical. This enables each position in the array to be optimized for its specific encoding function while maintaining compatibility with standard manufacturing processes that can accommodate controlled variations in optical axis positioning
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 significantly enhances the difficulty of reproducing security documents and ensures effective verification of authenticity by creating a complex, multi-viewable image structure that is hard to decipher without precise alignment and observation angles, thus providing robust security against counterfeiting.
Implementation Method 1
complex transparency device, i.e. a refractive and/or diffractive device acting on the phase of light
Implementation Method 2
complex transparency device, i.e. a refractive and/or diffractive device acting on the phase of light
Implementation Method 3
devices exploiting the moiré effect are currently widely used. See EP2811470 for more information. They rely on coupling between a phase grating (such as micro-optical devices) and a micro-image grating with different spacings.
Data Source
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AI summary
The invention relates particularly to an assembly (E) consisting of a complex transparency device, i.e. a refractive and/or diffractive device acting on the light phase, and at least one array of micro-images, in which: said complex transparency device consists of a periodical two-dimensional array (RPU) formed from individual "pupils" (PU) in which each pupil (PU) comprises a micro-optical device (1), at least some of said micro-optical devices (1) having a non-centred optical axis (10), and at least some of said micro-optical devices (1) being positioned non-periodically, i.e. with variable off-setting of the optical axis thereof within said array (RPU); said array (2) of micro-images consists of as many micro-images as micro-optical devices (1); each micro-image (2) has a contour identical to that of the associated pupil (PU) and a surface which is at the most identical to that of the associated pupil (PU); and each micro-image (2) is sub-divided into at least one thumbnail image (20) such that when said transparency device is positioned facing said array of micro-images (2), and an observer observes said array through said transparency device, the observer sees, at least in a given direction of observation, an image (S) which is reconstructed by the combination of the thumbnail images associated with said direction, characterised by the fact that within the same sub-division, certain thumbnail images (20), i.e. only some thereof, which form a "first group", are distributed such that when said transparency device is positioned facing said array of micro-images (2), said thumbnail images (20) are respectively arranged according to the optical axis of said associated micro-optical device (1).