Optical Security Device Diffractive Grating Design
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Solution Overview
Problem
Current optical security devices lack design flexibility and copy protection, and are limited in producing bright or brilliant images, with limited ability to generate multiple images that change movement patterns when the angle of incidence or observation changes.
Innovation Solution
An optical security device with a carrier and surface elements featuring first and second diffractive elements, where the diffractive elements are periodically repeated in different directions, allowing the surface elements to form groups that generate pixels which change position based on the angle of incidence or observation, and where the surface elements have overlapping diffractive structures to enhance image intensity and movement patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If surface elements with diffractive gratings are divided into groups to generate image pixels, then image generation capability is improved, but design freedom and copy protection are limited
Solution Approach 1:
The security device divides the surface into multiple independent surface elements, each containing diffractive gratings. These surface elements are further organized into groups that collectively generate image pixels. This segmentation allows flexible arrangement and configuration of surface elements to create various images and patterns, significantly enhancing design freedom while maintaining manageable structural complexity through modular organization.
Solution Approach 2:
The patent introduces angular dependency as an additional dimension for image generation. By configuring surface elements to generate different pixels based on viewing angles, the device creates a three-dimensional observation space where images appear at different positions depending on the observer's angle. This angular dimension dramatically increases design freedom without proportionally increasing structural complexity.
2Reliability
If surface elements are arranged to generate images with angle-dependent positioning, then copy protection is improved, but image brightness and brilliance are limited
Solution Approach 1:
Multiple surface elements within each group are configured to generate the same pixel, causing their diffracted light to overlap and reinforce each other. This merging of light paths from multiple surface elements significantly increases image brightness and brilliance while the angle-dependent positioning of these groups maintains strong copy protection capabilities.
Solution Approach 2:
The patent ensures continuous image generation across different viewing angles by carefully configuring the angular ranges of different surface element groups. As the viewing angle changes, different groups become active, maintaining continuous image visibility and brightness throughout the observation space while preserving angle-dependent copy protection.
3Reliability
If surface elements are configured for angle-dependent image positioning, then security is improved, but the ability to generate multiple images with different movement patterns is limited
Solution Approach 1:
Different surface element groups are assigned different local optical properties, including different grating orientations, periods, and angular ranges. This allows each group to generate images with distinct movement patterns in the observation space. The local differentiation of surface element properties enables generation of multiple images with diverse characteristics while maintaining overall security through angle-dependent positioning.
Solution Approach 2:
The patent employs asymmetric configurations of diffractive gratings in different surface element groups, with varying grating directions, periods, and orientations. This asymmetry creates images that move in different directions and patterns when viewed from different angles, significantly enhancing the ability to generate multiple distinguishable images while maintaining strong security through angle-dependent 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 provides a higher degree of design freedom, improved copy protection, and the ability to generate multiple images with distinct movement patterns, resulting in brighter and more brilliant images that appear to move continuously when the angle of incidence or observation changes.
Implementation Method 1
each element having a first diffractive element, wherein the first diffractive element has a structure that repeats periodically in a first direction
Data Source
Figure 1
Figure 2a~2b
Figure 3a~3b
AI summary
The invention relates to an optical security device (1, 1'), comprising a carrier (5) and a plurality of planar elements (8, 8a, 8b, 8c, 18a, 18b, 18c), which are distributed on a surface of the carrier (5) and which have a first diffractive element, wherein the first diffractive element has a structure that periodically repeats in a first direction, wherein the planar elements (8, 8a, 8b, 8c, 18a, 18b, 18c) having the first diffractive element form a plurality of groups each having at least two planar elements (8, 8a, 8b, 8c, 18a, 18b, 18c), wherein the planar elements (8, 8a, 8b, 8c, 18a, 18b, 18c) having the first diffractive element of each group are arranged and designed in such a way that the first diffractive elements produce a pixel of a first image (13, 14) for an observer (3) or an observation apparatus, wherein the first image (13, 14) is composed of the pixels produced by the plurality of groups, wherein the planar elements (8, 8a, 8b, 8c, 18a, 18b, 18c) are arranged and designed in such a way that, during operation of the security device (1, 1'), the number of planar elements (8, 8a, 8b, 8c, 18a, 18b, 18c) of a group that produce a pixel of the first image (13, 14) or the planar elements (8, 8a, 8b, 8c, 18a, 18b, 18c) of the group that are involved in the production of the pixel depend on an angle of incidence (α) at which light from a light source (2) hits the security device (1, 1') or on an angle of observation (β) at which the observer (3) or the observation apparatus observes the security device (1, 1'), and wherein the planar elements (8, 8a, 8b, 8c, 18a, 18b, 18c) are arranged and designed in such a way that, during the operation of the security device (1, 1'), a position of the first image (13, 14) in an observation space (15) for the observer (3) or the observation device depends on the angle of incidence (α) or the angle of observation (β). According to the invention, in order to provide an optical security device that has a higher degree of design freedom in the selection of the displayed images, at least one planar element (8, 8a, 8b, 8c, 18a, 18b, 18c) has, in addition to the first diffractive element, a second diffractive element having a structure that periodically repeats in a second direction, wherein the first direction and the second direction are different from each other.