HUD Windshield Coating for p-Polarized Ghost Image Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current head-up display (HUD) projection arrangements face challenges with ghost images due to reflection on windshield surfaces, which are typically alleviated by using expensive wedge films, and there is a need for solutions that ensure high transmission and color neutrality with p-polarized radiation.
Innovation Solution
A HUD projection arrangement using a windshield with a reflective coating comprising a single electrically conductive layer and alternating dielectric layers, optimized for p-polarized radiation reflection, eliminating the need for wedge films and ensuring high-intensity, color-neutral displays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If s-polarized radiation is used for HUD projection, then the projector can operate with standard windshields, but ghost images appear due to reflection from both external surfaces of the windshield
Solution Approach 1:
The patent changes the polarization parameter of the radiation from s-polarized to p-polarized. This parameter change exploits the Brewster angle phenomenon where p-polarized light experiences minimal reflection at the air-to-glass interface, thereby eliminating ghost images while maintaining ease of manufacture with standard windshield materials
Solution Approach 2:
The patent converts the potentially harmful reflection effect into a beneficial one by using the Brewster angle property. At this specific angle of incidence, p-polarized radiation is transmitted through the windshield surfaces with minimal reflection, transforming the reflection phenomenon from a source of ghost images to a mechanism that enhances transmission and reduces unwanted reflections
2Object-generated harmful factors
If p-polarized radiation is used for HUD projection, then ghost images are eliminated, but the windshield requires a reflective coating which increases manufacturing complexity
Solution Approach 1:
The patent employs a composite coating structure consisting of multiple layers with different optical properties: a first dielectric layer with high refractive index, a metallic layer with intermediate refractive index, and a second dielectric layer with low refractive index. This composite structure optimizes the reflection of p-polarized radiation while maintaining transmission characteristics, achieving the desired effect without excessive manufacturing complexity
Solution Approach 2:
The patent applies the reflective coating only to specific regions of the windshield where HUD projection occurs, rather than covering the entire windshield surface. This localized application reduces the overall manufacturing complexity and material requirements while still achieving the ghost image elimination effect in the critical projection area
3Object-generated harmful factors
If a reflective coating is applied to the windshield for p-polarized radiation, then ghost images are reduced, but transmission in the visible spectral range may be reduced
Solution Approach 1:
The patent optimizes the thickness parameters of each coating layer to achieve the desired balance between reflection and transmission. By carefully controlling the thickness of the dielectric and metallic layers, the coating reflects p-polarized radiation at the Brewster angle while maintaining high transmission for other wavelengths and angles, minimizing energy loss
Solution Approach 2:
The coating structure is designed to have directionally selective optical properties. The layers are engineered to provide high reflectivity specifically for p-polarized radiation at the Brewster angle (where HUD projection occurs), while maintaining high transmission for other polarization states and angles, thereby preserving overall visible light transmission
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 effectively reduces ghost images and maintains high transmission and color neutrality, providing a cost-effective and intense HUD image without the need for wedge films, while being compatible with polarization-selective sunglasses.
Implementation Method 1
a projector (HUD projector) directed onto a HUD area of the windshield with radiation in the visible range to generate a HUD projection
Implementation Method 2
The dielectric layer sequences comprise n optically low-refractive-index layers with a refractive index of less than 1.8 and (n+1) optically high-refractive-index layers with a refractive index of more than 1.8, each of which are arranged alternately
Implementation Method 3
The reflective coating has precisely one electrically conductive layer
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
The present invention relates to a projection assembly for a head-up display (HUD), at least comprising: a windshield (10), which comprises an outer pane (1) and an inner pane (2), which are interconnected by means of a thermoplastic intermediate layer (3), the windshield having a HUD region (B); and a projector (4), which is directed at the HUD region (B); wherein: the radiation of the projector (4) is predominantly p-polarized and the windshield (10) is provided with a reflective coating (20) suitable for reflecting p-polarized radiation; the reflective coating (20) has exactly one electrically conductive layer (21); two dielectric layer sequences, each comprising n low-optical-refraction layers (22) having an index of refraction of less than 1.8 and (n+1) high-optical-refraction layers (21) having an index of refraction of greater than 1.8, are provided, one of said dielectric layer sequences being arranged above and the other below the electrically conductive layer (21), the dielectric layer sequences each being alternatingly arranged, n being an integer greater than or equal to 1.