Optical Security Device with Anisotropic Light Redirecting Elements
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Solution Overview
Problem
Conventional optical security devices rely on viewing angle for optically variable effects, making them susceptible to imitation through tilting, and require high resolution for multi-color images, which is difficult to achieve.
Innovation Solution
An optical device featuring a color layer with alternating elongate strips of different colors and a light redirecting layer with anisotropic elements that redirect light based on illumination angle, allowing the display of distinct images by rotating the device relative to the light source, without the need for high resolution in the color layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional optical security devices use viewing angle for optically variable effects, then the security effect is achieved, but the device becomes susceptible to imitation through tilting
Solution Approach 1:
The patent inverts the conventional approach by making the optically variable effect dependent on illumination angle rather than viewing angle. The light redirecting layer with anisotropic elements redirects light based on the angle of illumination, not the angle of observation. This means the security effect is controlled by how light hits the device rather than how the viewer positions themselves, making it impossible to replicate by simple tilting and fundamentally changing the interaction mechanism between observer, device, and light source.
2Manufacturing precision
If high resolution is used for multi-color images in optical security devices, then image quality is improved, but manufacturing difficulty increases
Solution Approach 1:
The patent segments the color information into separate elongate strips of different colors arranged in a periodic pattern. Instead of requiring high-resolution continuous color images, the invention uses discrete color strips that can be manufactured using standard printing processes. The light redirecting layer then selectively illuminates portions of these strips to create the desired color combinations in the displayed image, dramatically reducing manufacturing complexity while maintaining visual quality.
Solution Approach 2:
The patent applies local quality by having different regions of the light redirecting layer with different orientations of anisotropic elements. Each local region redirects light to illuminate specific color strips based on the illumination angle, creating different color combinations in different areas of the displayed image. This allows multi-color images to be formed through spatial variation in the light redirecting properties rather than through high-resolution color printing.
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 unique optically variable effect that cannot be replicated by conventional devices, enabling secure authentication and allowing for multi-colored images to be displayed with standard printing processes, enhancing security and visual impact.
Implementation Method 1
the anisotropic light redirecting elements of the first array each having a primary axis orientated along a first direction lying in the plane of the optical device and being configured such that an incident light beam lying in a plane perpendicular to the first direction and from a light source off the normal of the optical device will be redirected by the anisotropic light redirecting elements towards the normal of the optical device
Implementation Method 2
the light redirecting layer comprising at least a first array of refractive and/or reflective anisotropic light redirecting elements
Implementation Method 3
a colour layer which comprises elongate strips of at least two different colours alternating with one another periodically along a direction of colour periodicity
Data Source
Figure 1(a)~1(b)
Figure 2
Figure 3
AI summary
An optical device is disclosed, comprising: a colour layer which comprises elongate strips of at least two different colours alternating with one another periodically along a direction of colour periodicity, the elongate strips extending along the direction which is orthogonal to the direction of colour periodicity; and a light redirecting layer overlapping the colour layer, and defining at least a first image to be exhibited by the optical device. The light redirecting layer comprises at least a first array of refractive and/or reflective anisotropic light redirecting elements extending across a first region of the light redirecting layer and being absent elsewhere, the anisotropic light redirecting elements of the first array each having a primary axis orientated along a first direction lying in the plane of the optical device and being configured such that an incident light beam lying in a plane perpendicular to the first direction and from a light source off the normal of the optical device will be redirected by the anisotropic light redirecting elements towards the normal of the optical device but within the same plane, whereas an incident light beam lying in a plane which is not perpendicular to the first direction and from a light source off the normal of the optical device will either not be redirected, or will be redirected by the anisotropic light redirecting elements out of the plane of the incident light beam.