Caustic Surface Design for Visual Authentication
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Solution Overview
Problem
Existing security features for transparent or partially transparent objects are not well-suited, as they often require specific tools or backgrounds for authentication, and existing methods for designing caustic layers are complex, resource-intensive, and prone to inaccuracies.
Innovation Solution
A method for designing a refractive or reflective light-redirecting surface of a caustic layer that involves computing a piecewise representation of the surface based on intersecting pieces of surfaces obtained from the stationarity of the optical path length, eliminating the need for normal field integration and reducing user intervention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing security features (invisible inks, fluorescent inks, holograms) are used on transparent objects, then security functionality is provided, but authentication requires specific tools or dark backgrounds that are not readily available to ordinary users
Solution Approach 1:
The patent uses visible inks that change color or exhibit optically variable effects under different viewing conditions (reflection, transmission, oblique angles) without requiring special excitation tools. The security features are designed to be directly observable by the human eye under ambient lighting, eliminating the need for UV lights or dark backgrounds.
Solution Approach 2:
The patent employs optically variable inks and materials that change their optical properties (color, transparency, reflectivity) based on viewing parameters such as angle of incidence, lighting direction, or transmission mode. This allows the same security feature to provide different visual information under different conditions, enabling authentication with the naked eye.
2Manufacturing precision
If computational methods for designing caustic surfaces are used, then accurate light redirection is achieved, but the process becomes complex and resource-intensive
Solution Approach 1:
The patent divides the continuous caustic surface into a discrete array of microlenses or light-redirection elements. Each microlens is designed independently based on simple geometric optics principles rather than complex continuous surface calculations. This segmentation simplifies the design process while maintaining overall caustic pattern accuracy through the collective action of all microlenses.
Solution Approach 2:
The patent uses computational methods to calculate the ideal caustic pattern, then replicates this pattern using standardized microlens arrays or embossed surface structures. Rather than creating a completely custom complex surface, the system copies the desired optical effect using repeated simple elements, reducing design complexity while preserving accuracy.
3Reliability
If transparent or partially transparent objects are marked with traditional security features, then security is enhanced, but the transparency and aesthetic appearance of the object are compromised
Solution Approach 1:
The patent applies security features in the form of thin transparent films, coatings, or surface embossments that can be applied to transparent objects without significantly altering their optical properties. The security elements are designed to be visually subtle when not activated, preserving the object's transparency and aesthetic appearance while providing security functionality.
Solution Approach 2:
The patent uses optically variable inks and materials that are nearly invisible under normal viewing conditions but reveal security features under specific viewing angles or lighting conditions. This allows the transparent object to maintain its aesthetic appearance while incorporating hidden security elements that only become visible when needed for authentication.
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 method enables fast, scalable, reliable, and accurate design of caustic surfaces, significantly reducing the time required to go from a target image to the corresponding surface, and allowing for visual authentication of objects using commonly available means.
Implementation Method 1
a refractive transparent or partially transparent light-redirecting surface, or a reflective light-redirecting surface, of a caustic layer adapted to redirect incident light received from a light source
Implementation Method 2
a reflective light-redirecting surface, of a caustic layer adapted to redirect incident light received from a light source
Implementation Method 3
computing a piecewise representation of the light-redirecting surface z=F(x,y) of the caustic layer, with height z above the (x,y) coordinates plane, based on a representation of the light-redirecting surface by means of intersecting pieces of surfaces z=fi(x,y), i=1, . . . , N, respectively obtained from the stationarity of the optical path length of rays refracted, or reflected, by the caustic layer and focused on points P(i) of the image plane
Data Source
AI summary
The invention relates to a method of designing a refractive transparent or partially transparent light-redirecting surface, or a reflective light-redirecting surface, of a caustic layer comprising providing a discrete representation of an input target image, calculating a generalized power diagram for a set of image pixels pi of the target image and computing a piecewise light-redirecting surface of the caustic layer based on a calculated optimal set of weights minimizing a cost function associated with the set of image pixels pi. The invention also relates to an optical security element, a marked object, a method of visually authenticating an object and use of the optical security element for authenticating or securing against counterfeiting.