Laminated HUD Pane with Hydrophobic Layer for Ghost Reduction
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Solution Overview
Problem
Head-up displays (HUDs) suffer from ghost images due to secondary reflections on windshields, which are not visible with polarization-selective sunglasses, and require high power consumption, while existing solutions are not adequately protected from environmental influences.
Innovation Solution
A laminated pane with a reflective layer on the inner side of the inner pane, protected by a hydrophobic film, which emits p-polarized light and is positioned to avoid secondary reflections, combined with an opaque background to enhance image visibility and reduce energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a reflective layer is applied to the windshield to improve image brightness and contrast, then the visibility of the HUD image is improved, but the reflective layer becomes exposed to environmental influences such as moisture and dirt
Solution Approach 1:
The reflective layer is nested within the laminated pane structure, specifically positioned on the inner side of the inner pane between the pane and the interior space. This nesting approach embeds the reflective layer within the protected environment of the laminated glass, shielding it from external environmental factors while maintaining its optical function.
Solution Approach 2:
The patent introduces an intermediate layer (adhesive layer or spacer) between the reflective layer and the inner pane surface. This intermediary element acts as a protective barrier that prevents direct exposure of the reflective layer to environmental influences while allowing the layer to maintain its reflective function for HUD image generation.
2Illumination intensity
If the projector power is increased to improve image brightness for daytime visibility, then the image can be seen in sunlight, but the power consumption increases
Solution Approach 1:
The patent employs asymmetric optical design by using p-polarized light specifically, which exploits the Brewster angle effect to minimize reflection losses at the glass-air interface. This asymmetric approach to light polarization allows for more efficient light transmission and reflection, reducing the need for high projector power while maintaining adequate image brightness.
Solution Approach 2:
The patent changes the optical parameters of the system by selecting specific incidence angles (around the Brewster angle of approximately 56 degrees for glass) and using p-polarized light. This parameter optimization maximizes the reflection efficiency of the reflective layer, allowing the projector to operate at lower power levels while still achieving sufficient image brightness for daytime visibility.
3Loss of information
If the incidence angle is optimized to reduce ghost images, then the contrast between main image and ghost image is improved, but the reflection efficiency for p-polarized light decreases
Solution Approach 1:
The patent optimizes the incidence angle parameter to be around the Brewster angle (approximately 56 degrees for typical glass), which simultaneously achieves two objectives: it minimizes ghost images by reducing unwanted reflections from the outer surface, and it maximizes the reflection efficiency for p-polarized light. This precise parameter selection resolves the contradiction between image contrast and reflection efficiency.
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 laminated pane provides high-contrast imaging compatible with polarization-selective sunglasses, reduces ghost images, and lowers energy consumption by optimizing the reflective layer's position and protecting it from external influences.
Implementation Method 1
the windshield has a reflective structure which can reflect p-polarized radiation towards the driver
Implementation Method 2
Since the incidence angle is typically close to the Brewster angle, and p-polarized radiation is therefore reflected only to a small degree by the glass surfaces
Implementation Method 3
a hydrophobic film is arranged at least on the functional layer element
Data Source
AI summary
A laminated pane includes an inner and an outer pane, a thermoplastic intermediate layer, and functional layer element. The outer pane has an outer side facing away from the thermoplastic intermediate layer and an inner side facing the thermoplastic intermediate layer, and the inner pane has an outer side facing the thermoplastic intermediate layer and an inner side facing away from the thermoplastic intermediate layer. The functional layer element is arranged on the inner side of the inner pane and is suitable for emitting light. The functional layer element is a reflective layer or an active imaging element, and is itself opaque or is arranged spatially in front of an opaque background when viewed through the laminated pane starting from the inner side of the inner pane, and wherein a hydrophobic film is arranged at least on the functional layer element.