Optical Variable Device Diffractive Structure for 3D Color Reconstruction
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Solution Overview
Problem
Existing optical variable devices fail to accurately reconstruct a three-dimensional image of an arbitrary object in various pre-selected colors, including non-spectral colors and black, with high resolution and sharpness, and are not suitable for mass production due to complex and costly manufacturing processes.
Innovation Solution
An optical variable device featuring a first relief diffractive structure with grooves in the form of Fresnel diffractive zones, enhanced by a second relief diffractive structure with specific depression profiles and distances to achieve accurate color representation, allowing for high-resolution and sharp three-dimensional image reconstruction across a wide range of observation angles, including non-spectral colors and black.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a relief diffractive structure with colour layers is used to reconstruct a three-dimensional image in a particular colour, then the image is completely coloured in one colour, but the device does not allow high quality reconstruction of a three-dimensional colour image of an object in more than one colour and requires expensive colour lacquers or foils
Solution Approach 1:
The invention divides the diffractive structure into multiple zones, each with different groove depths corresponding to different colors of the object. This segmentation allows each zone to reconstruct a specific color independently, enabling multi-color 3D image reconstruction without requiring color layers or foils, thus reducing manufacturing cost while maintaining color fidelity.
Solution Approach 2:
The invention applies different groove depth characteristics to different spatial zones of the diffractive structure based on the local color information of the object. Each zone is optimized with specific groove depths to reconstruct the corresponding color accurately, allowing the device to reproduce multiple colors simultaneously without using color materials.
2Manufacturing precision
If multiple relief diffractive structures are combined to reconstruct images in various colors, then color accuracy improves, but the manufacturing process becomes complex and time-consuming with multiple resist coating and exposure stages
Solution Approach 1:
The invention merges multiple diffractive structures into a single integrated relief diffractive structure where different zones have different groove depths. This consolidation achieves multi-color 3D image reconstruction in one structure, eliminating the need for multiple separate manufacturing stages including multiple resist coating and exposure processes, thereby simplifying manufacturing while maintaining color accuracy.
Solution Approach 2:
The invention varies the groove depth parameter across different zones of the diffractive structure to encode color information. By changing only the groove depth parameter rather than creating multiple separate structures, the device achieves multi-color reconstruction capability with a single manufacturing process, reducing both complexity and production time.
3Reliability
If a diffractive structure with coloured layers is used, then a three-dimensional image can be reconstructed in one particular colour, but the artistic and aesthetic characteristics are limited and the device is not suitable for mass production
Solution Approach 1:
The invention segments the diffractive structure into multiple zones with different groove depths, each corresponding to a different color of the object. This allows the device to reconstruct multi-color 3D images without requiring color layers, making it suitable for mass production while enhancing artistic and aesthetic characteristics through accurate color reproduction.
4Manufacturing precision
If colour lacquers or foils are used for reconstruction of a colour image, then the image can be coloured, but the optical device becomes more expensive and requires supplementary control in the production process
Solution Approach 1:
The invention extracts the color reconstruction function from external color materials (lacquers or foils) and integrates it directly into the relief diffractive structure through zone-dependent groove depths. This eliminates the need for separate color layers, reducing manufacturing cost and simplifying the production process while maintaining accurate color reproduction.
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 effectively reconstructs high-resolution, sharp three-dimensional color images of objects in various colors, including non-spectral colors and black, with dynamic color effects observable across a wide range of angles, making it suitable for mass production and use as a security element in authentication and decoration.
Implementation Method 1
a first relief diffractive structure with grooves in the form of Fresnel diffractive zones... reconstructing a three-dimensional image of the object
Implementation Method 2
grooves in the form of Fresnel diffractive zones
Implementation Method 3
a second relief diffractive structure with a binary profile comprising a set of depressions... allowing for high-resolution and sharp three-dimensional image reconstruction
Data Source
Figure 1a~1c
Figure 2a~2d
Figure 3a~3c
AI summary
The invention refers to an optical variable device and finds application as a decorative and security element against counterfeiting of documents, securities, goods, etc. It includes a first relief diffractive structure (1) with Fresnel structure of a arbitrary object (3). A second relief diffractive structure (4) is added over the first one. The second relief diffractive structure (4) consists of areas (7) corresponding to the areas with the same colour of the object and consisting of depressions (5), equal or different in shape, size and direction with distance d between them, where 0.150µm ≤d≤ 10µm. The profile of the depressions is made up from 2 to 7 discreet planes (6) with height hi, where 0.02µm≤ hi ≤ 1µm, and in each area (7) the number and the height hi of the planes (6) and the distance d are the same and depend on the colour of the object in the relevant area (7)'. The planes (6) can have a stepped profile. The depressions (5) can be arranged in a two-dimensional matrix М with axes X and Y, located under angle 45о≥β≥135о, wherein 0,150µm≥d≥0,50µm and for each area (7) the distance d and the angle β are the same.