Diffractive Security Device with On-Axis Zone Plate
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Solution Overview
Problem
Current security devices for authenticating valuable articles, such as banknotes and passports, can be replicated using available reproduction techniques, limiting their effectiveness against counterfeiters, necessitating the development of new, distinctive visual effects.
Innovation Solution
A diffractive security device featuring an on-axis diffractive zone plate structure with a continuously curved surface, generating a diffraction pattern visible from various angles, where features appear to move between regions, providing a unique visual effect that is difficult to replicate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional security devices are used, then they can be manufactured with existing techniques, but they can be replicated by counterfeiters using available reproduction techniques
Solution Approach 1:
The security device divides the diffractive structure into multiple discrete regions, each containing a portion of the overall diffraction pattern. This segmentation makes replication difficult because counterfeiters would need to replicate multiple discrete diffractive elements with precise spatial relationships, rather than copying a single continuous structure.
Solution Approach 2:
The device incorporates an optically variable effect where the diffraction pattern changes appearance based on viewing angle. The pattern appears to move or shift as the viewing angle changes, creating a dynamic visual effect that is extremely difficult to replicate with static copying techniques.
2Reliability
If a complete diffractive structure is used, then a strong visual effect is generated, but the device becomes more susceptible to replication
Solution Approach 1:
The complete diffractive structure is segmented into multiple discrete regions distributed across the device. Each region contains a portion of the diffraction pattern, and collectively they produce the full visual effect. This segmentation maintains security while allowing for more manageable manufacturing and reducing the complexity of any single replicable element.
Solution Approach 2:
Different regions of the device contain different portions of the diffractive structure, creating local variations in optical properties. Each region has specific diffractive features tailored to its position, which collectively create the overall visual effect while making replication difficult since each region must be precisely replicated in its specific location.
3Reliability
If the diffractive structure is continuous, then the visual effect is smooth and strong, but it is easier to replicate
Solution Approach 1:
The continuous diffractive structure is broken into discrete, spaced-apart regions. Each region independently contributes to the overall diffraction pattern, but the spacing between regions creates gaps that are difficult to replicate. This segmentation maintains the strength of the visual effect while significantly increasing replication difficulty.
Solution Approach 2:
The device uses a diffractive structure that creates an optically variable effect which cannot be copied through conventional reproduction techniques. The movement and transformation of the diffraction pattern based on viewing angle creates a visual effect that fundamentally cannot be replicated by photocopying or other standard reproduction methods.
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 device offers a new, distinctive visual effect that is challenging to counterfeit, enhancing security by ensuring that direct copies lack the optically variable effect, thus distinguishing genuine from fake devices.
Implementation Method 1
a first diffractive structure defined in a carrier layer, the first diffractive structure being an on-axis 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
Data Source
AI summary
A diffractive security device is disclosed including at least a first diffractive structure defined in a carrier layer. The first diffractive structure is an on-axis 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.