Thin Optically Variable Devices Using Volume Holography
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Solution Overview
Problem
Existing optically variable devices (OVDs) are too thick for applications like banknotes and security labels due to conventional printing limitations, and there is a need for thinner, more sophisticated security features that are difficult to counterfeit.
Innovation Solution
The development of an optically variable device comprising a substrate with a volume hologram or Lippmann photograph as a data-bearing volume, combined with a focusing layer of refractive, diffractive, or reflective elements that provide magnified and dynamic optical effects when viewed from specific angles, allowing for thinner constructions and enhanced security features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional printing technology is used to create micro-objects for OVDs, then the micro-objects can be produced with sufficient visual detail, but the resulting device thickness becomes too great (250-450 microns) for applications like banknotes and security labels
Solution Approach 1:
The patent changes the fundamental parameter of how micro-objects are created by replacing conventional printing with volume holography or Lippmann photography. These techniques record three-dimensional light field information directly in a photosensitive medium, eliminating the need for physical printing layers and reducing device thickness to under 50 microns while maintaining or enhancing visual quality.
Solution Approach 2:
The invention substitutes mechanical printing processes with optical field recording. Instead of physically depositing ink or pigment layers to create micro-objects, the system uses interference patterns of coherent light to directly encode visual information in a volume holographic medium, thereby eliminating the thickness constraints of conventional printing.
2Length of stationary object
If lens diameters are reduced to 50-250 microns to achieve thinner OVDs, then the device thickness decreases, but the focal lengths must be similarly reduced which complicates the optical design and manufacturing
Solution Approach 1:
The patent extracts and eliminates the intermediate substrate layer that separates the lens array from the micro-object layer in conventional designs. By recording micro-objects directly in the volume holographic medium at the focal plane of the lenses, the design removes unnecessary structural complexity and reduces overall device thickness without compromising optical performance.
3Length of stationary object
If embossed or cast micro-objects are used instead of printed ones, then the OVD thickness can be reduced to under 50 microns, but the manufacturing process becomes more complex and costly
Solution Approach 1:
The patent uses volume holography to create a direct optical copy of the micro-object information field. The photosensitive medium records the complete three-dimensional light distribution of the object array, producing a faithful replica that can be viewed through the lens array without requiring physical embossing or casting processes.
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 solution enables the creation of very thin OVDs with sophisticated optical effects that provide clear visual differentiation, making them more difficult to counterfeit and suitable for thinner applications while maintaining effective security features.
Implementation Method 1
a data-bearing volume (e.g., a volume hologram or Lippmann photograph)
Implementation Method 2
an array of focusing elements or lenses disposed on the second surface. The optical geometry is arranged so that when the OVD is observed from a predetermined relative point, the focusing array being disposed between the observer and the object array
Implementation Method 3
focusing layer of refractive, diffractive, or reflective elements
Implementation Method 4
focusing layer of refractive, diffractive, or reflective elements
Data Source
Figure 1~2
Figure 1A
Figure 3~4
AI summary
An optically variable device ("OVD") (101a) with an integral image system that includes a focusing element (103a) and an array of micro-objects (106) which, when viewed through the focusing element (103a), changes in appearance depending on the relative location from which the OVD is observed. A security device including the OVD and methods for creating the OVD are also disclosed.