Parallelogram Microlens Grid for Anti-Forgery Security Elements
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Solution Overview
Problem
Current security elements for data carriers, such as ID cards and banknotes, face challenges in providing high security against forgery while maintaining an attractive visual appearance and design flexibility, particularly in ensuring the accuracy of optically variable features that are robust to deviations in the subject image plane from the focal plane.
Innovation Solution
A security element featuring a lenticular image with a parallelogram lattice of non-cylindrical microlenses and a motif image composed of elementary cells broken down into sub-areas, where each sub-area is assigned to a target image, allowing for unscaled representation and robustness against deviations in the subject image plane, with the relative position of microlenses and sub-areas defining specific viewing angle ranges for image visibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a lenticular grid with cylindrical lenses is used for security features, then optically variable effects are achieved, but image sharpness deteriorates when the subject image plane deviates from the focal plane
Solution Approach 1:
The patent replaces conventional cylindrical lenses with conical lenses, representing a fundamental geometric asymmetry change. This conical geometry creates a different optical path that maintains image sharpness across varying distances from the focal plane, directly resolving the contradiction between security reliability and manufacturing precision.
Solution Approach 2:
The invention changes the optical parameters by using conical lenses with specific aperture angles and focal lengths that are optimized to maintain a extended depth of field. This parameter optimization ensures that images remain sharp even when the subject plane deviates from the focal plane, while maintaining the optically variable security effects.
2Adaptability or versatility
If the carrier film thickness is reduced to improve flexibility, then design freedom increases, but image sharpness and focal plane accuracy deteriorate
Solution Approach 1:
The conical lens geometry inherently provides a larger depth of field compared to cylindrical lenses, which compensates for variations in carrier film thickness. This allows the use of thinner, more flexible carrier films without sacrificing focal plane accuracy, thus resolving the contradiction between adaptability and manufacturing precision.
3Ease of manufacture
If conventional cylindrical lenses are used, then the structure is simple and easy to manufacture, but the visual appearance and security robustness are limited
Solution Approach 1:
The conical lenses can be manufactured using standard embossing or molding techniques similar to cylindrical lenses, maintaining ease of production. However, the conical geometry provides superior optical performance with a larger depth of field and enhanced image sharpness, improving security robustness without significantly increasing manufacturing complexity.
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 provides a robust and visually appealing security feature that maintains image sharpness and visibility ranges, even with deviations from the focal plane, enhancing security against forgery and reducing the thickness of the carrier film, thus improving the overall security element's effectiveness.
Implementation Method 1
a lenticular array and a motif image spaced apart from the lenticular array, which when viewed with the lenticular array shows the predetermined target images
Data Source
Figure 1~2
Figure 3~5
Figure 6a~7b
AI summary
The security element (20) has a lenticular image for unscaling representation of two or more predetermined target images. The lenticular image has a lens grid (25) and a motive image (26) arranged at a distance by the lens grid. The motive image displays the predetermined target images when viewed. The lens grid is formed by multiple non-cylindrical micro-lenses (24), which are arranged in a grid with the symmetry of a parallelogram grid. An independent claim is included for a method for manufacturing security element.