Micro-optical System Kinematic Effects Security
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Solution Overview
Problem
Current security threads used to protect bank notes and securities often have widths less than 5 mm, limiting the range of angles where kinematic effects of motion are observed, and are vulnerable to counterfeiting due to the availability of technologies that can replicate visual effects.
Innovation Solution
A microoptical system utilizing a flat diffractive optical element with axial Fresnel lenses and diffraction gratings, where the optical element is divided into elementary areas with specific phase functions, allowing for the creation of black and white stripes that change with tilt angles, and a different color image at larger diffraction angles, enhancing security and reducing replicable technologies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If conventional security threads with width less than 5 mm are used, then the thread can be integrated into narrower bank notes, but the range of angles where kinematic effects of motion are observed is limited
Solution Approach 1:
The optical element is divided into multiple elementary areas (Qij), each containing axial Fresnel lenses with specific phase functions. This segmentation allows different regions to contribute to kinematic effects at different viewing angles, extending the overall angular range despite the narrow thread width of less than 5 mm.
Solution Approach 2:
Different elementary areas are assigned different phase functions (φij(x,y) · ψ(y)) to optimize their contribution at specific diffraction angles. This local optimization ensures that each region of the thread contributes to the kinematic effect within its optimal angular range, collectively covering a broader spectrum of viewing angles.
2Ease of manufacture
If conventional security features are used, then existing technologies can be easily replicated, but the protection against counterfeiting is weakened
Solution Approach 1:
The patent combines multiple optical elements (axial Fresnel lenses, diffraction gratings) with specific phase functions in a composite structure. This composite approach creates a security feature that integrates several optical principles, making replication significantly more difficult while remaining manufacturable through established techniques.
Solution Approach 2:
The patent employs specific parameter relationships (Δ/Tψ ≤ 1/2, period Tφ differing from Tψ by no more than 5%) to create optimized optical effects. These precisely controlled parameters create visual effects that are difficult to replicate without exact knowledge and reproduction of the parameter relationships.
3Adaptability or versatility
If the optical element is divided into many elementary areas with complex phase functions, then the visual control capabilities are extended, but the manufacturing complexity increases
Solution Approach 1:
By dividing the optical element into discrete elementary areas Qij, the complex phase function Φ(x,y) is broken into manageable segments that can be independently calculated and manufactured. Each segment's phase function φij(x,y) · ψ(y) can be optimized without affecting others, simplifying the overall manufacturing process.
Solution Approach 2:
The patent uses a universal mathematical framework (phase functions of the form φij(x,y) · ψ(y)) that applies to all elementary areas. This unified approach allows the same manufacturing process to produce diverse optical effects across different regions, reducing overall system complexity despite the variety of functions.
4Adaptability or versatility
If axial Fresnel lenses with parabolic phase functions are used instead of off-axis lenses, then kinematic effects are observed over a wider angle range, but the image formation at small angles becomes more challenging
Solution Approach 1:
Different elementary areas are assigned different phase functions optimized for their specific angular contributions. Areas contributing to small-angle images use phase functions optimized for that range, while other areas handle larger angles, ensuring high image quality across the entire angular spectrum.
Solution Approach 2:
The patent dynamically assigns different phase functions to different spatial regions based on their angular contribution. This dynamic optimization ensures that each region of the optical element is tuned to produce the desired kinematic effects at its optimal viewing angles, maintaining image quality across the full angular range.
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 system extends the range of observable kinematic effects, improves security thread protection against counterfeiting by using electron-beam technology for high-resolution production, and allows for secure, visually controllable images over a wide range of angles.
Implementation Method 1
When the microoptical system is illuminated by a point light source then at diffraction angles smaller than 60° the observer sees over the entire area Q of the optical element an image consisting of black and white stripes
Implementation Method 2
function φ ij (x,y) has the form of the phase function of an off-axis Fresnel lens centered on point (x i ,y j )
Data Source
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AI summary
The microoptical system for the formation of visual images claimed as the invention belongs mostly to the type of devices used for authentication of products, and can be efficiently used to protect bank notes and securities. The microoptical system, according to the claims, consists of fragments of multilevel flat axial Fresnel lenses with a parabolic phase function and diffraction gratings. A special choice of parameters of multilevel Fresnel lenses and diffraction gratings makes it possible to form images with kinematic effects. When the microoptical system is illuminated by a point light source then at diffraction angles smaller than 60° the microoptical system forms an image consisting of black and white stripes, which does not change when the optical element is turned left/right. The kinematic effect consists in the motion of black and white stripes when the microoptical system is tilted up/down. At diffraction angles of more than 60°, the observer sees a different color image throughout the entire area of the microoptical system. The claimed combination of essential features of the invention ensures the achievement of the technical result, which consists in expanding the capabilities of visual control, and in the improvement of the protection of the microoptical system against counterfeit. The implementation of a microoptical visual imaging system is possible using existing standard equipment.