Wedge-Shaped Interlayer Reducing Dynamic Ghosting in HUD Windshields
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Solution Overview
Problem
Conventional polymeric interlayers in windshields for head-up display (HUD) systems suffer from dynamic ghosting, which worsens at longer virtual image distances, due to variations in wedge angle from the target angle, leading to unacceptable image quality and increased eye fatigue for drivers.
Innovation Solution
A wedge-shaped interlayer with a controlled vertical wedge angle profile and absolute wedge angle rate of change less than 3.0 μrad/mm throughout the HUD region, ensuring minimal deviation from the target wedge angle, thereby minimizing dynamic ghosting and maintaining optimal image quality at longer virtual image distances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional tapered interlayer with constant wedge angle is used, then ghost image reduction is achieved for a single driver position, but dynamic ghosting occurs when the driver moves within the eyebox
Solution Approach 1:
The patent applies the dynamics principle by transitioning from a static constant wedge angle to a dynamic variable wedge angle that changes across the HUD region. The wedge angle is designed to vary continuously to compensate for different driver eye positions, allowing the interlayer to adapt dynamically as the driver moves within the eyebox while maintaining ghost image reduction across the entire viewing area.
Solution Approach 2:
The patent applies local quality by implementing different wedge angle values in different regions of the HUD interlayer. Each local region has a specifically optimized wedge angle tailored to that area's requirements, allowing precise control of ghost image alignment for multiple driver positions simultaneously rather than using a single uniform angle.
2Ease of manufacture
If the wedge angle varies significantly from the target angle, then manufacturing is easier, but dynamic ghosting increases leading to unacceptable image quality
Solution Approach 1:
The patent applies parameter changes by establishing specific quantitative parameters for the wedge angle variation, including the rate of change limit (less than 3.0 μrad/mm) and the maximum deviation from target angle. These parameter specifications provide clear manufacturing guidelines that balance ease of production with the precision needed to minimize dynamic ghosting across the HUD region.
3Illumination intensity
If a dielectric coating is applied to reduce ghost images, then secondary image brightness is reduced, but adhesion between polymeric interlayer and glass substrates is compromised
Solution Approach 1:
The patent applies the extraction principle by removing the dielectric coating from the system and replacing it with an optimized tapered polymeric interlayer structure. This extracts the harmful adhesion-blocking effect of the coating while retaining the ghost image reduction function through the wedge angle design, eliminating the need for coatings that compromise interlayer bonding.
Data Source
AI summary
A wedge-shaped interlayer having reduced dynamic ghosting is provided, wherein the interlayer comprises at least one polymer layer comprising a poly(vinyl acetal) resin and at least one plasticizer, wherein said wedge-shaped interlayer defines a head-up display (HUD) region having a target vertical wedge angle, an actual vertical wedge angle and an absolute wedge angle rate of change, wherein the absolute wedge angle rate of change is less than 3.0 prad/mm throughout the entire HUD region.