Optical Security Component with Double Waveguide Contrast
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Solution Overview
Problem
Current optical security components for banknotes lack sufficient contrast between identifiable information and peripheral areas, making it difficult to authenticate documents effectively.
Innovation Solution
An optical security component is developed with a structured layer configuration, including a support layer, identification elements printed with opaque dielectric material, and layers of high and low refractive index, creating a double waveguide structure that enhances contrast through subtractive filter effects, and optionally incorporating a reflective layer to further differentiate identifiable information from peripheral regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional optical security components are used, then the security thread is visible and provides basic authentication, but the contrast between identifiable information and peripheral areas is insufficient
Solution Approach 1:
The optical security component is segmented into multiple functional layers: a support layer, identification elements layer, and a double waveguide structure with alternating high and low refractive index layers. Each layer serves a specific function in enhancing contrast and visibility of identifiable information.
Solution Approach 2:
The identification elements are selectively positioned in specific regions of the support layer, creating local variations in optical properties. The double waveguide structure is configured to enhance contrast specifically at the locations of identifiable information, while peripheral areas maintain different optical characteristics.
2Illumination intensity
If a reflective layer is added to enhance contrast, then the visibility of identifiable information is improved, but the manufacturing process becomes more complex
Solution Approach 1:
The double waveguide structure with alternating high and low refractive index layers acts as an intermediary optical system that enhances the visibility of identification elements. This intermediate structure modifies light propagation to create strong contrast between identifiable information and peripheral areas without requiring additional reflective layers.
3Measurement precision
If the contrast ratio is increased to exceed 0.88, then authentication accuracy is improved, but the optical component requires more complex refractive index layering
Solution Approach 1:
The optical security component utilizes controlled variations in refractive index parameters across multiple layers. By carefully selecting and alternating between high and low refractive index materials, the design achieves a contrast ratio exceeding 0.88, significantly improving authentication accuracy while maintaining manufacturability.
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 significant increase in contrast between identifiable information and peripheral areas, enhancing the visibility and authenticity verification of security threads on banknotes, with a contrast ratio exceeding 0.88 in the spectral band of interest.
Implementation Method 1
layers of high and low refractive index, creating a double waveguide structure that enhances contrast through subtractive filter effects
Implementation Method 2
structured to form a sub-wavelength network... behaves like a structured waveguide making it possible to excite resonances of guided modes at different wavelengths
Implementation Method 3
optionally incorporating a reflective layer to further differentiate identifiable information from peripheral regions
Data Source
Figure 1~3
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Figure 7A~7G
AI summary
According to one aspect, the invention concerns an optical security component (10) intended to be observed by direct reflection, comprising an observation face (100) and identifiable information (22), said component comprising, successively, starting from the side opposite the observation face: a first support layer (11), identification elements (12) obtained by printing an absorbent material to reproduce at least a portion of said identifiable information, structured on one of the faces thereof that opposes the face opposite the support layer, to form a first subwavelength grating, a second layer (13) having a high refractive index, covering the first support layer and the identification elements, a third layer (14) having a low refractive index, in contact with said second layer, structured on the entire surface of same to form a second subwavelength grating, a fourth layer (15) having a high refractive index, in contact with said third structured layer (14), a fifth layer (16) having a low refractive index, in contact with said fourth layer (15).