Optical Security Element Caustic Pattern Projection

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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 precise spatial arrangements, and are not compatible with reduced object sizes.

Innovation Solution

A reflective or refractive optical security element with a relief pattern that projects a caustic pattern, designed using a method to select and calculate a relief pattern for easy visual authentication with commonly available illumination, suitable for objects of reduced dimensions like banknotes and transparent substrates.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If semi-transparent optically variable features (e.g., liquid crystal coatings) are used, then the security element provides optical variability, but the marking must be observed against a dark/uniform background for the effect to be well visible

Engineering Contradiction:

Improveoptical variabilityVSAvoidobservation conditions

Core Design Contradiction:

Ease of manufactureVSEase of operation

Solution Approach 1:

The optical security element uses the illumination light itself as the background, eliminating the need for separate dark/uniform backgrounds. The element reflects or refracts the incident light to create visible patterns directly on the illumination source, allowing observation under normal lighting conditions without requiring controlled background environments.

Inventive Principle:

Principle #25Self-service

2Reliability

If diffractive optical elements are used to project a pattern, then the security feature provides visual authentication, but a precise relative spatial arrangement of the light source, the diffractive optical element and the user's eyes is required

Engineering Contradiction:

Improvevisual authenticationVSAvoidspatial arrangement requirements

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The optical security element is designed to work with a range of spatial arrangements rather than a fixed precise configuration. The element can be illuminated from various angles and observed from different positions, providing dynamic flexibility in usage while maintaining reliable visual authentication. This eliminates the need for strict spatial alignment between light source, element, and observer.

Inventive Principle:

Principle #15Dynamics

3Reliability

If laser engraved micro-text and or micro-codes are used, then the security feature provides authentication capability, but expensive tools are required for implementation and detection

Engineering Contradiction:

Improveauthentication capabilityVSAvoidimplementation tools

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces complex mechanical implementation tools (laser engraving equipment, magnifying detectors) with simple optical elements that create visible patterns through reflection or refraction. The authentication is achieved through macroscopic optical patterns rather than microscopic engravings, allowing detection with the naked eye or common magnifying lenses instead of expensive specialized equipment.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Reliability

If existing security features are used on transparent objects, then the security element provides authentication, but the features change the transparency or appearance of the object

Engineering Contradiction:

ImproveauthenticationVSAvoidtransparency preservation

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The optical security element introduces localized light-redirecting surfaces with relief patterns that only affect light interaction at specific locations. The rest of the transparent substrate maintains its original transparency and appearance properties. This localized approach allows authentication functionality to be added without compromising the overall optical quality and aesthetic appearance of the transparent object.

Inventive Principle:

Principle #3Local quality

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 using the naked eye or a magnifying lens, compatible with mass production, and suitable for transparent substrates, with a relief pattern depth as low as 30 μm, allowing for reliable authentication without strict spatial arrangements.

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 from a light source and form a projected image on a projection surface

Methodology Applied

Scientific EffectLight redirection: Reflection

Implementation Method 2

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

Methodology Applied

Scientific EffectRefraction: Refraction

Data Source

PatentUS11292283B2Optical security element

Publication Date: 2022.04.05 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 optical parameters of this optical security element fulfilling a specific projection criterion such that the projected image comprises 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 an optical security element.