Hologram Master Specular Reflection Element Fiducial Mark Alignment
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Solution Overview
Problem
Existing methods for producing individualized volume reflection holograms face challenges in precise positioning due to light scattering and direction variations during the reconstruction of fiducial marks, leading to inaccuracies in detecting the fiducial mark position, especially with diffusely diffracting masters like ground glass screens.
Innovation Solution
A master with a reflection element that specularly reflects coherent light for forming fiducial marks, reducing light scattering and maintaining a consistent direction of reconstruction, is used, along with a spatial light modulator for precise modulation of light to define the fiducial mark spatially and align it with individualized structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a diffusely diffracting master (ground glass screen) is used for hologram production, then the master can be easily manufactured and is simple in structure, but the light scattering and direction variations during fiducial mark reconstruction lead to poor positioning precision
Solution Approach 1:
The master is designed with spatially varying properties: the fiducial mark area has a specular reflective surface for precise light direction, while the remaining areas maintain diffuse diffraction properties for hologram formation. This local differentiation allows the fiducial marks to be reconstructed with consistent direction and high positioning precision, while the rest of the master continues to function as a diffuse diffraction element for easy manufacturing.
2Reliability
If coherent light is used to expose the volume reflection hologram, then the hologram can be formed with proper interference patterns, but the light scattering at the master causes fluctuations in diffraction efficiency and reconstruction direction
Solution Approach 1:
The master surface is differentiated into two functional zones: a specular reflective region for fiducial marks that ensures consistent light reflection direction, and diffuse diffraction regions for holographic content that enable proper interference pattern formation. This local quality differentiation resolves the contradiction by providing each area with the appropriate optical properties for its specific function.
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
This approach minimizes positional fluctuations of fiducial marks during reconstruction, allowing for more precise positioning of volume reflection holograms and reducing diffraction efficiency fluctuations, enabling accurate detection and alignment within security documents.
Implementation Method 1
A master with a reflection element that specularly reflects coherent light for forming fiducial marks, reducing light scattering and maintaining a consistent direction of reconstruction
Implementation Method 2
along with a spatial light modulator for precise modulation of light to define the fiducial mark spatially and align it with individualized structures
Implementation Method 3
a diffractive structure arranged on or formed within the substrate and covering the usable area, wherein the diffractive structure reflects coherent light of a wavelength, which strikes the diffractive structure from a predetermined direction of incidence, back into a predetermined direction of reflection
Data Source
Figure 1a~1c
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AI summary
The invention relates to a master (20) for producing a customized volume reflection hologram in a customizable region, comprising a carrier (20), at least one diffraction structure (21), which is arranged on the carrier (20) or is formed in the carrier and covers a customizable region, wherein the at least one diffraction structure (21) reflects coherent light of a wavelength incident on the diffraction structure (21) from a specified incidence direction in a specified drop-out direction, wherein the master (52) comprises a reflection element (55), which reflects directed light in a mirroring manner in accordance with the geometric optics. The invention further relates to a method for producing customized volume holograms and a method for producing a master (52).