Wedge-Shaped Windshield Interlayer for HUD Ghosting Reduction
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Solution Overview
Problem
Conventional polymeric interlayers in windshields with head-up display (HUD) systems suffer from dynamic ghosting and reflected double image separation, particularly at longer virtual image distances, leading to reduced image quality and increased eye fatigue for drivers.
Innovation Solution
The development of polymeric interlayers with a wedged profile that includes a HUD region and a non-HUD region, featuring a controlled absolute wedge angle rate of change less than 3.0 μrad/mm, which minimizes dynamic ghosting and reflected double image separation by optimizing the wedge angle variation across the windshield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional polymeric interlayer is used in a windshield with a head-up display system, then the windshield provides basic optical transmission and safety functions, but dynamic ghosting and reflected double image separation occur at longer virtual image distances, reducing image quality and increasing driver eye fatigue
Solution Approach 1:
The patent applies parameter changes by precisely controlling the wedge angle variation across the interlayer thickness. The interlayer is designed with a specific wedge angle range (0.5-2.0 degrees) and a controlled rate of change (less than 3.0 μrad/mm) to optimize optical performance. This parameter optimization minimizes dynamic ghosting and reflected double image separation while maintaining safety and transmission properties, directly resolving the contradiction between image quality and harmful optical effects.
2Object-affected harmful factors
If the wedge angle rate of change is increased to reduce ghosting, then reflected double image separation is minimized, but optical distortion and adhesion issues may occur
Solution Approach 1:
The patent establishes precise parameter boundaries to resolve this contradiction. The wedge angle is controlled within 0.5-2.0 degrees and the rate of change is limited to less than 3.0 μrad/mm. These optimized parameters simultaneously minimize reflected double image separation while preventing optical distortion and adhesion problems, achieving a balanced solution that addresses both concerns.
Solution Approach 2:
The patent uses dielectric coatings as an alternative approach to wedge-shaped interlayers. By applying dielectric coatings with specific optical properties, the system can reduce ghosting effects without introducing the manufacturing complexity and potential adhesion issues associated with precise wedge angle control, providing a complementary solution that copies the functional benefit while avoiding the manufacturing precision challenges.
3Object-affected harmful factors
If a dielectric coating is applied to minimize ghost images, then the secondary image brightness is reduced, but the coating may interfere with polymeric interlayer adhesion to glass substrates
Solution Approach 1:
The patent uses the polymeric interlayer itself as an intermediary element between the glass substrates and the HUD system. Rather than applying dielectric coatings that may interfere with adhesion, the interlayer is designed with optimized wedge angle parameters (0.5-2.0 degrees, rate of change less than 3.0 μrad/mm) that provide ghosting reduction while maintaining excellent adhesion to glass substrates. This intermediary approach resolves the contradiction by achieving optical performance without compromising bonding strength.
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
This solution effectively reduces dynamic ghosting and reflected double image separation, providing a clearer and more readable virtual image for drivers, especially at longer virtual image distances, thereby enhancing the overall HUD system performance and driver comfort.
Implementation Method 1
The wedge angle required to minimize the appearance of a ghost image depends on a variety of factors... Most conventional tapered interlayers include a constant wedge angle over the entire HUD region... the absolute wedge angle rate of change is less than 3.0 μrad/mm throughout at least a portion of both the HUD and non-HUD regions
Data Source
AI summary
A wedge-shaped interlayer having reduced dynamic ghosting and reduced dynamic transmitted imagery variations 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, and less than 3.0 prad/mm outside the HUD region.