Diffractive Security Device with Zone Plate and Off-Axis Structures
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Solution Overview
Problem
Current security devices for authenticating valuable articles, such as banknotes and passports, are vulnerable to counterfeiting due to the ability of counterfeiters to replicate existing designs, necessitating the development of new, distinctive visual effects that cannot be easily copied.
Innovation Solution
A diffractive security device combining a diffractive zone plate structure with an off-axis diffractive structure, featuring a continuously curved surface that generates distinct diffraction patterns visible from various angles, providing a dynamic and memorable visual effect that is difficult to imitate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional security devices are used, then they provide basic authentication, but they are vulnerable to counterfeiting
Solution Approach 1:
The patent combines two different diffractive structures (zone plate and off-axis grating) into a single composite security device. This composite structure creates multiple diffraction patterns that are difficult to replicate, directly addressing the counterfeiting vulnerability while maintaining authentication reliability
Solution Approach 2:
The security device is divided into distinct functional regions: a first region containing the zone plate structure and a second region containing the off-axis grating structure. This segmentation allows each structure to contribute its unique diffraction characteristics, creating a multi-layered authentication system resistant to counterfeiting
2Device complexity
If a single diffractive structure is used, then the device is relatively simple, but the visual effect is static and easier to replicate
Solution Approach 1:
The patent merges two diffractive structures with different optical properties into one device. The zone plate generates a first diffraction pattern while the off-axis grating generates a second diffraction pattern, creating a dynamic composite visual effect that changes with viewing angle and is difficult to replicate
Solution Approach 2:
The security device creates dynamic visual effects through angle-dependent diffraction patterns. As the viewing angle changes, the interaction between the two diffractive structures produces changing interference patterns, making the visual effect dynamic rather than static and significantly harder to replicate
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 combination of diffractive zone plate and off-axis diffractive structures creates a unique, dynamic visual effect that is highly resistant to replication, enhancing the security and authenticity verification of valuable documents.
Implementation Method 1
the first diffractive structure being a diffractive zone plate structure of a continuously curved surface configured such that when the device is illuminated by on-axis light a first diffraction pattern generated by the first diffractive structure can be viewed from at least a first side of the device at substantially all viewing angles
Implementation Method 2
the second diffractive structure being an off-axis diffractive structure configured such that when the device is illuminated by on-axis light a second diffraction pattern generated by the second diffractive structure can be viewed from at least the first side of the device at at least some off-axis viewing angles
Data Source
AI summary
A diffractive security device is disclosed, including first and second diffractive structures defined in a carrier layer. The first diffractive structure is a diffractive zone plate structure of a continuously curved surface configured such that when the device is illuminated by on-axis light, a first diffraction pattern generated by the first diffractive structure can be viewed from at least a first side of the device at substantially all viewing angles, the first diffraction pattern exhibiting a reference point or reference line relative to which other features of the first diffraction pattern appear to move when the viewing angle is changed. The second diffractive structure is an off-axis diffractive structure configured such that when the device is illuminated by on-axis light a second diffraction pattern generated by the second diffractive structure can be viewed from at least the first side of the device at at least some off-axis viewing angles.