Ultrawide Angle Retroreflective Articles for Autonomous Vehicle Vision
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Solution Overview
Problem
Retroreflective sheeting and materials face limitations in achieving high net retroreflectivity at larger entrance angles and across a broader electromagnetic spectrum, particularly in visible and near-infrared ranges, due to reduced performance in wet conditions and limited durability.
Innovation Solution
The development of ultrawide angle reflective articles and materials with multiple retroreflective layers, including a base layer and a mezzanine layer with tilted cube corner elements, which enable total internal reflection (TIR) over a broader range of angles and improve reflective efficiency across different environmental conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If air spaces are used behind retroreflective elements to maximize index of refraction difference, then retroreflectivity at high entrance angles is improved, but durability and resistance to foreign material infusion deteriorate
Solution Approach 1:
The patent applies different index of refraction materials in specific locations: a first material with index n1 in the retroreflective elements, a second material with index n2 in the intermediate layer (where n2 < n1), and a third material with index n3 in the backing layer. This localized differentiation of material properties optimizes TIR at each interface while maintaining structural integrity and durability.
Solution Approach 2:
The patent employs a composite multi-layer structure combining materials with different optical properties. The intermediate layer uses a material with lower index of refraction than the retroreflective elements, creating enhanced TIR conditions. This composite approach simultaneously achieves high retroreflectivity and improved durability by eliminating air spaces that compromise structural strength.
2Ease of manufacture
If conventional retroreflective sheeting is used, then manufacturing simplicity is maintained, but entrance angle performance and spectral breadth deteriorate
Solution Approach 1:
The patent divides the retroreflective structure into multiple functional layers: retroreflective elements, intermediate layer with first index of refraction material, and backing layer with second index of refraction material. This segmentation allows each layer to be optimized for its specific function while maintaining overall manufacturability through established multi-layer fabrication techniques.
Solution Approach 2:
The patent changes the index of refraction parameter by introducing an intermediate layer with a material having a lower index of refraction than the retroreflective elements. This parameter modification enables TIR to occur at higher entrance angles, expanding the angular performance range while remaining compatible with conventional manufacturing processes.
3Device complexity
If single-layer retroreflective structures are used, then device complexity is reduced, but spectral coverage and reflective efficiency deteriorate
Solution Approach 1:
The multi-layer structure serves multiple functions simultaneously: the retroreflective elements provide the primary reflective function, the intermediate layer with lower index of refraction material enhances TIR for broader angular coverage, and the backing layer provides structural support. This multi-functionality achieves superior spectral coverage and reflective efficiency without proportionally increasing complexity.
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
These materials enhance net retroreflectivity and reflective efficiency across a broader spectrum, maintaining performance in both dry and wet conditions, and are suitable for use in autonomous vehicle systems, improving visibility and safety by extending the range of angles for TIR and enhancing interaction with vehicle-based machine vision sensors.
Implementation Method 1
The retroreflective elements in retroreflective sheeting and materials enhance retroreflectivity by utilizing the phenomenon of total internal reflection (TIR)
Implementation Method 2
Articles and materials with ultrawide angle ranges of TIR also exhibit improved reflective efficiency across a broader spectrum of electromagnetic radiation
Data Source
AI summary
A two-layer retroreflective article construction is enabled that produces higher wide-entrance-angle performance for signs and pavement markings. A single-layer overlay is enabled for existing signs and pavement markers that improve their entrance angle performance. Materials used in the construction of an article or an overlay are transparent to radiation in the range of 400 to 1000 nanometers and utilize TIR (total internal reflection). Minimum performance specifications are proposed that extend sign sheeting retroreflectivity specifications to entrance angles of 60 degrees. An innovative traffic sign design is enabled that increases the positioning performance of safety systems and automated navigation systems.