Thin Optical Security Element with Caustic Relief Pattern

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Solution Overview

Problem

Existing security features for transparent or partially transparent objects are not well-suited for authentication by the general public, as they often require specific tools or strict spatial arrangements, and are not compatible with mass-production processes or objects of reduced dimensions.

Innovation Solution

A reflective or refractive optical security element with a thin relief pattern having abrupt variations, designed to project a caustic pattern using a calculated relief profile with discontinuities, allowing authentication with the naked eye and compatible with mass-production, using easily available illumination sources like LEDs or sunlight.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If existing security features are used for transparent objects, then security functionality is provided, but authentication requires specific tools or strict spatial arrangements that are not readily available to the general public

Engineering Contradiction:

Improveauthentication easeVSAvoiddetection tool requirement

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The optical security element is designed to be self-authenticating through its inherent optical properties. The relief pattern on the transparent substrate creates visible optical effects (caustics, light concentration patterns, or image projections) that can be observed directly with the naked eye or simple magnification, eliminating the need for specialized detection tools or complex authentication procedures.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The invention utilizes optical effects that create visible changes in light distribution and intensity. The relief pattern redirects incident light to create concentrated light patterns, caustics, or projected images that are visually distinct and easily observable, providing clear authentication signals without requiring specialized equipment.

Inventive Principle:

Principle #32Color changes

2Volume of moving object

If thin optical security elements are used for objects of reduced dimensions, then compatibility with small objects is improved, but manufacturing precision requirements increase

Engineering Contradiction:

Improveelement thicknessVSAvoidrelief pattern precision

Core Design Contradiction:

Volume of moving objectVSManufacturing precision

Solution Approach 1:

The invention changes the optical parameters by utilizing the transparent substrate property and designing relief patterns that create strong optical effects (caustics, light concentration) with minimal depth. By optimizing the relief pattern geometry and utilizing optical concentration effects, the patent achieves effective authentication with reduced thickness while maintaining manufacturability through standard precision processes.

Inventive Principle:

Principle #35Parameter changes

3Illumination intensity

If diffractive optical elements are used to project patterns, then optical effects are achieved, but laser illumination and precise spatial arrangement are required which complicates operation

Engineering Contradiction:

Improvepattern visibilityVSAvoidillumination requirement

Core Design Contradiction:

Illumination intensityVSEase of operation

Solution Approach 1:

The invention segments the optical function into two parts: the transparent substrate with relief pattern that handles light redirection, and the illumination source which can be any conventional light source. This segmentation allows the use of simple, widely available illumination sources (sunlight, LEDs, lamps) rather than requiring laser sources, while still achieving clear visible patterns through the relief pattern's light concentration and caustic effects.

Inventive Principle:

Principle #1Segmentation

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

Enables easy visual authentication of marked objects without specialized tools, suitable for transparent substrates, and compatible with objects of reduced dimensions, while maintaining the capability to project recognizable patterns with reduced thickness and manufacturing complexity.

Implementation Method 1

a reflective light-redirecting surface, or refractive transparent or partially transparent light-redirecting surface, having a relief pattern operable to redirect incident light

Methodology Applied

Scientific EffectLight redirection: Reflection

Implementation Method 2

a refractive transparent or partially transparent light-redirecting surface, having a relief pattern operable to redirect incident light

Methodology Applied

Scientific EffectRefraction: Refraction

Implementation Method 3

form a projected image on a projection surface, such that the projected image comprises a caustic pattern

Methodology Applied

Scientific EffectCaustic pattern formation: Fresnel Diffraction

Data Source

PatentUS11298966B2Thin optical security element and method of designing it

Publication Date: 2022.04.12 SICPA HOLDING SA

AI summary

The invention relates to a thin optical security element comprising a reflective or refractive light-redirecting surface having a relief pattern operable to redirect incident light from a light source and form a projected image on a projection surface, the projected image comprising a caustic pattern reproducing a reference pattern that is easily visually recognizable by a person. The invention also relates to a method for designing a relief pattern of a light-redirecting surface of a thin optical security element.