Prismatic Retroreflective Sheeting for ALPR Halation Reduction
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Solution Overview
Problem
Prismatic retroreflective sheeting used in license plates often results in poor visibility and inability to read characters due to halation when imaged by automated license plate reader systems, especially under infra-red lighting, as existing materials do not effectively reduce infra-red retroreflectivity while maintaining visible light retroreflectivity and desired whiteness.
Innovation Solution
Incorporating infra-red non-transmissive materials, such as near infra-red absorbing or scattering agents, into the prismatic retroreflective sheeting, optionally combined with whiteness-enhancing materials, to reduce infra-red retroreflectivity while maintaining visible light retroreflectivity and desired whiteness, thereby minimizing halation and ensuring accurate reading by ALPR systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If prismatic retroreflective sheeting is used in license plates, then visible light retroreflectivity is maintained, but infra-red retroreflectivity is too high causing halation and poor readability in ALPR systems
Solution Approach 1:
The patent applies local quality by incorporating infra-red non-transmissive materials specifically in the infra-red blocking layer to reduce infra-red retroreflectivity at specific wavelengths, while maintaining visible light retroreflectivity through the prismatic structure. This targeted approach addresses halation without compromising visible light performance.
Solution Approach 2:
The patent uses composite materials by combining prismatic retroreflective structures with infra-red non-transmissive materials in a multi-layer configuration. This composite structure enables simultaneous achievement of visible light retroreflection and infra-red light blocking, resolving the contradiction between maintaining visible performance and reducing infra-red halation.
2Object-affected harmful factors
If infra-red absorbing materials are incorporated into the sheeting, then infra-red retroreflectivity is reduced, but whiteness and visible light performance may deteriorate
Solution Approach 1:
The patent applies local quality by using infra-red non-transmissive materials with specific optical properties that selectively block infra-red wavelengths while maintaining transparency or neutrality in the visible spectrum. This ensures whiteness and visible light performance are preserved while achieving infra-red retroreflectivity reduction.
Solution Approach 2:
The patent changes the optical parameters of the sheeting by selecting infra-red non-transmissive materials with specific transmittance characteristics. The materials are chosen to have low transmittance in the infra-red range while maintaining appropriate transmittance and scattering properties in the visible range to preserve whiteness and retroreflective performance.
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 effectively reduces infra-red retroreflectivity while maintaining visible light retroreflectivity and whiteness, minimizing halation and enabling accurate reading of license plates by ALPR systems, thus addressing the issue of poor visibility and readability.
Implementation Method 1
incorporating infra-red non-transmissive materials, such as near infra-red absorbing or scattering agents, into the prismatic retroreflective sheeting
Implementation Method 2
incorporating infra-red non-transmissive materials, such as near infra-red absorbing or scattering agents, into the prismatic retroreflective sheeting
Implementation Method 3
prismatic retroreflective sheeting typically comprises a thin transparent layer having a substantially planar first surface and a second structured surface comprising a plurality of geometric structures, some or all of which include three reflective faces configured as a cube corner element
Data Source
AI summary
The present application relates to retroreflective sheeting that is capable of use in a license plate and that can be accurately read and/or detected by an ALPR system. The retroreflective sheeting is a prismatic retroreflective sheeting that provides reduced retroreflectivity of infra-red light. The retroreflective sheeting can also be a prismatic retroreflective sheeting that exhibits reduced retroreflectivity of incident infra-red light and substantially unaffected retroreflectivity of incident visible light.