Volume Hologram Security Document with Bragg Selectivity
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Solution Overview
Problem
Current paper-based security documents with embossed holograms are vulnerable to high forgery rates due to the ease of imitating their kinematic structures, even for experienced observers, as the uniform structures lack individual personalization and advanced manufacturing processes.
Innovation Solution
Implementing volume holograms that store security features, utilizing photorefractive materials to create complex, difficult-to-manipulate data storage, which can be individually personalized with the document holder's information, providing a higher level of security through Bragg selectivity and refractive index gratings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If embossed holograms are used to protect security documents, then the documents can be secured with a visual security feature, but the forgery rate increases due to ease of imitation
Solution Approach 1:
The patent transitions from embossed holograms to volume holograms, changing the fundamental optical parameter from surface-level diffraction to three-dimensional Bragg diffraction. This parameter change creates security features that are much harder to replicate while maintaining visual identification capabilities
Solution Approach 2:
The invention moves from two-dimensional embossed holograms to three-dimensional volume holograms. This dimensional transition enables complex light interference patterns stored throughout the material volume, creating security features that cannot be easily copied by conventional manufacturing methods
2Reliability
If volume holograms are implemented to increase security, then security against counterfeiting improves, but the manufacturing process becomes more complex
Solution Approach 1:
The volume hologram is pre-formed on a carrier layer before being applied to the security document. This preliminary creation of the complex holographic structure allows for controlled manufacturing using photorefractive materials, after which the completed hologram is transferred to the document, separating the complex manufacturing process from the document production
3Reliability
If volume holograms with Bragg selectivity are used, then security features become difficult to manipulate, but the manufacturing precision requirements increase
Solution Approach 1:
The patent utilizes Bragg selectivity, which changes the optical response parameters of the hologram based on angle and wavelength. This creates security features that are highly sensitive to manipulation attempts, as any deviation from the precise Bragg conditions prevents proper hologram reconstruction, thereby deterring counterfeiting
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
Volume holograms significantly enhance security by being difficult to counterfeit, allowing easy visual identification and machine-readable verification, with attempts to manipulate the hologram leading to destruction of the document, thus preventing successful forgery.
Implementation Method 1
two coherent light waves are superimposed in the holographic storage material, namely an object or data wave carrying the information and a reference wave. This creates an interference pattern in the hologram plane
Implementation Method 2
If later only the reference wave illuminates the hologram, the original object wave is created by diffraction
Implementation Method 3
Photorefractive materials, which react to bright light in a similar way to photographic layers or hologram plates, are used to store such a quantity of data in a volume material
Implementation Method 4
The smallest changes in the illumination angle, the wavelength or in the phase distribution of the wave prevent the reconstruction. The enormous potential of data storage is based on this condition, known as Bragg selectivity
Implementation Method 5
the carrier layer is bonded to the substrate layer by means of the adhesive layer
Data Source
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AI summary
The invention relates to a document (100) with a security feature, wherein the document comprises: a substrate layer (101); an adhesive layer (102); and a carrier layer (103) with a volume hologram (104), wherein the volume hologram (104) is configured to store the security feature, and wherein the carrier layer (103) is metallurgically bonded to the substrate layer (101) by means of the adhesive layer (102). The invention further relates to a method (600) for producing such a document.