HUD Windshield Coating for p-Polarized Ghost Image Elimination
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Solution Overview
Problem
Current head-up display (HUD) projection assemblies face challenges with ghost images due to reflection on windshield surfaces, which are costly to mitigate using wedge films, and require high transmittance and reflectivity for p-polarized radiation to ensure a clear, color-neutral display.
Innovation Solution
A projection assembly using a windshield with a reflective coating comprising a single electrically conductive layer and alternating dielectric layers, optimized for high reflectivity and transmittance, primarily reflecting p-polarized radiation to eliminate ghost images and ensure visibility with polarized sunglasses, while maintaining a color-neutral display.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a wedge-like intermediate layer is used to eliminate ghost images, then the ghost image problem is resolved, but the production cost increases significantly
Solution Approach 1:
The patent changes the parameter of the intermediate layer from wedge-like (variable thickness) to parallel (constant thickness). This parameter change eliminates the need for complex wedge-shaped lamination while still preventing ghost images through the p-polarised radiation reflection mechanism, significantly reducing production costs
Solution Approach 2:
The patent converts the harmful effect of p-polarised radiation reflection (which normally causes ghost images) into a beneficial effect by using it to eliminate ghost images entirely. The electrically conductive layer reflects p-polarised radiation before it can cause unwanted reflections from the windshield surfaces, turning a potential problem into a solution
2Object-affected harmful factors
If the reflective coating is optimized for high reflectivity of p-polarised radiation, then ghost images are eliminated, but the color neutrality of the display may be affected
Solution Approach 1:
The patent uses composite material structures with alternating dielectric layers of different refractive indices (such as SiO2 with n=1.46 and Si3N4 with n=2.0) combined with an electrically conductive layer. This composite structure creates constructive interference for p-polarised radiation in the visible spectral range (450-650 nm), ensuring both high reflectivity and color-neutral display through controlled optical interference
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 eliminates ghost images and ensures high-intensity, color-neutral HUD images without the need for expensive wedge films, maintaining high transmittance and reflectivity, thus reducing production costs and enhancing user experience.
Implementation Method 1
the reflective coating causes high reflectivity relative to p-polarised radiation
Implementation Method 2
operated with p-polarised radiation, which is not significantly reflected by the pane surfaces
Implementation Method 3
The reflective coating has dielectric layer sequences above and below an electrically conductive layer. In embodiments, the dielectric layer sequences are formed from n high-optical-refraction layers and (n+1) low-optical-refraction layers that are arranged alternatingly
Implementation Method 4
irradiate the windshield with an angle of incidence of about 65%, which is near Brewster's angle for an air/glass transition (57.2° for soda lime glass)
Data Source
AI summary
A projection assembly for a head-up display (HUD) includes a windshield, including an outer and inner pane joined to one another via a thermoplastic intermediate layer, and having an HUD region; and a projector directed at the HUD region. The radiation of the projector is predominantly p-polarised, and the windshield is provided with a reflective coating, which is suitable for reflecting p-polarised radiation. The reflective coating has exactly one electrically conductive layer and arranged one above and one below the electrically conductive layer are two dielectric layer sequences, each including n low-optical-refraction layers having an index of refraction less than 1.8 and (n+1) high-optical-refraction layers having an index of refraction greater than 1.8, arranged alternatingly in each case, wherein n is an integer greater than or equal to 1.