Multilayer Microlens Element for Color Gradation Security
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Solution Overview
Problem
Current multilayer bodies with microlenses and microimages are limited to simple, monochrome motifs due to difficulties in producing high-resolution images with gray value or color gradations, restricting their use in security documents to basic alphanumeric characters and simplistic logos.
Innovation Solution
A multilayer body comprising a transparent first layer with shaped microlenses and a second layer containing microimage regions, where the microlenses and microimages are arranged in specific rasters with varying spacings, allowing for the creation of optically variable effects with gray value or color gradations without requiring high-resolution images in the second layer, thereby simplifying production and enhancing security features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If microimages with gray value or color gradations are produced in the second layer, then the optical representation becomes more brilliant and complex, but the manufacturing precision requirements become excessively high and production becomes restricted to simple monochrome motifs
Solution Approach 1:
The invention divides the image formation task into two separate layers: the first layer contains microlenses that perform optical segmentation and enlargement, while the second layer contains simplified microimages arranged in a raster pattern. This segmentation allows the complex optical effects to be achieved through the microlens array rather than requiring high-resolution microimages, thereby reducing manufacturing precision requirements while maintaining optical brilliance.
Solution Approach 2:
The microlens layer acts as an intermediary between the simple microimage raster and the final optical representation. The microlenses enlarge and optically process the simple microimages to create the brilliant, complex visual effect. This intermediary approach allows the second layer to maintain low manufacturing complexity while achieving high optical quality through the mediating action of the microlens array.
2Reliability
If identical microimages are arranged in a microlens raster to produce optically variable effects, then security against forgery is increased, but moiré effects occur that reduce image brilliance
Solution Approach 1:
The invention introduces asymmetry by using non-identical microimages within the microimage regions, or by varying the microlens parameters (focal length, diameter, shape) across the array. This asymmetry disrupts the regular periodic patterns that cause moiré effects, thereby eliminating the harmful interference patterns while preserving the optically variable security effects that rely on the overall raster arrangement.
Solution Approach 2:
The invention applies local quality variations by allowing different microimage regions to have different characteristics - such as different microimage content, different microlens focal lengths, or different raster spacings. This local differentiation prevents the formation of large-scale moiré patterns while maintaining the security functionality through localized optically variable effects.
3Measurement precision
If high-resolution gray value images are provided in the second layer to achieve gray value gradations, then the representation quality improves, but the device complexity and production difficulty increase significantly
Solution Approach 1:
The invention uses simple, easily manufacturable microimages as copies that are then optically enlarged and transformed by the microlens array. Instead of directly creating high-resolution gray value images in the second layer, the system uses simplified microimage copies that are processed optically to achieve the desired gray value gradations and high representation quality, thereby avoiding the complexity of direct high-resolution printing.
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
This approach enables the creation of brilliant, complex optical effects with gray value or color gradations, increasing the security against forgery and making the representation more brilliant by suppressing moiré effects, while allowing for flexible design and concealment of security features.
Implementation Method 1
a transparent first layer (13), in which a plurality of microlenses (13m) are shaped
Implementation Method 2
The microlenses arranged in a microlens array produce a copy of the microimages, that is enlarged in pixel fashion
Data Source
AI summary
Described is a multilayer body for representing microimages provided with gray value gradations or color gradations. The multilayer body has a transparent first layer in which a plurality of microlenses are shaped, and a second layer (61) which is arranged beneath the first layer and has a plurality of microimages. The microlenses are arranged in accordance with a microlens raster. The second layer has a plurality of microimage regions (61b) arranged in accordance with a microimage region raster whose raster width is <300 μm. Within each microimage region two or more of the microimages (61ma through 61mc) arranged in a microimage raster respectively differ from each other, wherein the raster spacings of the microlens raster and the microimage raster differ from each other by less than 10%. The microimages have regions with a gray value or a color value. Also disclosed is a process for the production of the multilayer body.