Lenticular Security Image Structure for Ghosting-Free Tone Switching
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Solution Overview
Problem
Lenticular security devices suffer from ghosting and cross-talk due to limitations in resolution and lateral dimensions, making it difficult for users to distinguish authentic from counterfeit documents and easier for counterfeits to be mistaken as genuine.
Innovation Solution
A security device with a static zone adjacent to the active zone, where the static zone matches the tone of the optically variable image in its 'on' or 'off' state, reducing ghosting effects by ensuring the image appears to disappear at the correct viewing angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If lenticular devices use thin focusing features to maintain document thickness, then the device can be incorporated into documents, but the lateral dimensions are limited causing ghosting and cross-talk
Solution Approach 1:
The patent transitions from conventional 2D lenticular structures to a 3D configuration by positioning image elements at different depths within the substrate. This vertical dimension allows larger image elements to be accommodated without increasing lateral dimensions, thereby reducing ghosting and cross-talk while maintaining thin profile.
Solution Approach 2:
The patent embeds multiple image elements at different depths and positions within the substrate, creating a nested structure. This allows the focusing features to access larger image areas without increasing the overall device thickness, improving resolution while maintaining thin form factor.
2Manufacturing precision
If image elements are made smaller to reduce ghosting, then image resolution improves, but the visual effect becomes harder to distinguish
Solution Approach 1:
By utilizing the vertical dimension to position image elements at different depths, the patent allows larger image elements to be used without increasing lateral density. This maintains visual distinguishability while reducing ghosting effects through proper spatial separation.
3Reliability
If the pitch between image elements matches the pitch between focusing features, then optical alignment is optimized, but ghosting increases due to limited resolution
Solution Approach 1:
The patent decouples the pitch relationship by utilizing vertical positioning. Image elements can be vertically offset from the focusing feature plane, allowing optimal optical alignment without being constrained by lateral pitch matching. This reduces ghosting while maintaining alignment reliability.
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 enhances the visual clarity and security level of the lenticular device by eliminating ghosting and ensuring clear image switching, making it harder to counterfeit and easier to authenticate.
Implementation Method 1
an array of focusing features disposed on the first or second side of the substrate and arranged periodically along at least a first direction, each focusing feature having a respective optical footprint of which different parts will be directed to the viewer in dependence on the viewing angle
Implementation Method 2
the array of micro-focusing features cooperates with the array of microimage elements to generate a magnified version of the microimage elements due to the moiré effect
Data Source
Figure 1~2(b)
Figure 2(c)
Figure 3~4(b)
AI summary
A security device comprising: a substrate (107) having an array of focusing features (101) such as lenses disposed on the substrate and arranged periodically, and a structure of a colour which comprises: an active zone (113) overlapping the array of focusing features and disposed in the focal plane thereof, the active zone having a periphery which defines an image, within which image extends an array of image elements (105) spaced from one another, wherein the pitch between the image elements is equal to the pitch between the focusing features. When the viewing angle varies, the tone of the image varies between a minimum tone and a maximum tone. The structure comprises a static zone (111) laterally adjacent the active zone and having a uniform tone that appears to the naked eye the same as the tone of the image at one of the maximum tone and the minimum tone.