HUD Projection Device with Polarization-Selective Coating
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Solution Overview
Problem
Head-up displays (HUDs) in vehicles face issues with secondary reflections from windshields, leading to ghost images and reduced intensity due to conductive coatings and polarization limitations, making them less visible for drivers wearing polarization-selective sunglasses.
Innovation Solution
A composite pane with an electrically conductive coating optimized for p-polarized radiation is used, allowing a mixture of s- and p-polarized radiation to enhance visibility for both drivers with and without polarization-selective sunglasses, by efficiently reflecting p-polarized components and maintaining neutral color representation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If an electrically conductive coating is applied to the windshield to reduce heating and improve thermal comfort, then thermal comfort is improved, but the coating creates an additional reflective interface that generates unwanted layer ghost images and reduces HUD image intensity
Solution Approach 1:
The patent applies different optical properties to different polarization components locally. The conductive coating is designed to have high reflectivity specifically for p-polarized radiation while maintaining transparency for s-polarized radiation, creating localized optical quality differentiation that resolves the contradiction between thermal management and HUD visibility
Solution Approach 2:
The patent changes the optical parameters of the conductive coating by optimizing its thickness (5-15 nm) and material composition to achieve selective polarization-dependent reflectivity. This parameter optimization allows the coating to reflect p-polarized HUD radiation effectively while maintaining overall transmission, thus improving HUD intensity without compromising thermal comfort functionality
2Object-affected harmful factors
If the windshield surfaces are arranged at an angle to superimpose main image and ghost image, then ghost image visibility is reduced, but the image intensity is reduced due to non-optimal reflection conditions
Solution Approach 1:
The patent changes the polarization state parameter of the reflected radiation by using a conductive coating optimized for p-polarized light. This parameter change enables effective reflection at the typical HUD angle of incidence (around 65°), which is close to the Brewster angle, thereby maintaining high image intensity while the angled surface arrangement continues to superimpose ghost images
3Adaptability or versatility
If p-polarized radiation is used for HUD projection to ensure visibility with polarization-selective sunglasses, then compatibility with sunglasses is improved, but the radiation is minimally reflected by glass surfaces at Brewster angle, reducing image intensity
Solution Approach 1:
The patent introduces an electrically conductive coating as an intermediary element between the HUD projector and the glass surfaces. This intermediary layer provides the necessary p-polarized radiation reflection that glass surfaces alone cannot achieve at Brewster angle, while maintaining compatibility with polarization-selective sunglasses. The coating acts as a mediator that enables both sunglasses compatibility and sufficient image intensity
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 improves the intensity and visibility of HUD projections by superimposing reflections and ensuring compatibility with polarization-selective sunglasses, reducing ghost images and enhancing overall image quality.
Implementation Method 1
the electrically conductive coating according to the invention is optimized for the reflection of p-polarized radiation
Implementation Method 2
A driver wearing polarization-selective sunglasses, which only allow p-polarized radiation to pass through, can therefore perceive the HUD image
Implementation Method 3
S-polarized radiation components are efficiently reflected by the lens surfaces
Implementation Method 4
Since the angle of incidence is typically close to the Brewster angle and p-polarized radiation is therefore only minimally reflected by the glass surfaces
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
The present invention relates to a projection arrangement for a head-up display (HUD), the arrangement at least comprising: a composite pane (10) having an outer pane (1) and an inner pane (2), which are interconnected by a thermoplastic intermediate layer (3), and having an upper edge (O), a lower edge (U) and an HUD region (B); a transparent, electrically conductive coating (20) provided on the surface (II, III) of the outer pane (1) or inner pane (2) that faces the intermediate layer (3), or provided within the intermediate layer (3); and a projector (4), directed onto the HUD region (B); wherein the light of the projector (4) has at least a p-polarized portion and the electrically conductive coating (20), in the spectral range of 400 nm to 650 nm, has only one local reflection maximum for p-polarized light, said maximum lying in the range of 510 nm to 550 nm.