HUD Windshield Coating for Ghost-Free p-Polarized Projection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing head-up display (HUD) projection arrangements for vehicles require expensive wedge films to prevent ghost images, which increase production costs.
Innovation Solution
The use of p-polarized radiation and a composite pane with a thin, electrically conductive coating, such as silver layers, that effectively reflects p-polarized radiation without the need for wedge films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a wedge film is used to prevent ghost images, then ghost images are eliminated, but production costs increase significantly
Solution Approach 1:
The patent extracts the essential function of the wedge film (preventing ghost images through differential reflection) and implements it through a simpler alternative: a standard parallel-pane windshield with optimized HUD projection geometry. By removing the wedge film and using p-polarized radiation at a specific angle, the solution eliminates the expensive intermediate layer while achieving the same ghost image prevention effect.
Solution Approach 2:
The patent changes the polarization parameter of the projected radiation from unpolarized or s-polarized to p-polarized light, and optimizes the angle of incidence to approximately 45 degrees. This parameter change exploits the Brewster angle effect where p-polarized light has minimal reflection at the air-glass interface, thereby eliminating ghost images without requiring a wedge film.
2Ease of operation
If s-polarised radiation is used for HUD projection, then the projector can operate at Brewster's angle, but ghost images are reflected from both windshield surfaces
Solution Approach 1:
Instead of using s-polarized radiation as is conventional, the patent inverts the approach by using p-polarized radiation. This inversion exploits the complementary polarization properties where p-polarized light experiences minimal reflection at Brewster's angle, thereby eliminating the ghost image problem that plagues s-polarized systems.
3Object-affected harmful factors
If p-polarised radiation is used, then ghost images are eliminated, but the windshield requires an electrically conductive coating for reflection
Solution Approach 1:
The patent makes the electrically conductive coating serve multiple functions: it acts as the reflection surface for p-polarized HUD radiation, provides electrochromic control capability, and enables heating functions. By integrating these functions into a single coating layer, the solution avoids the need for separate reflective layers while achieving ghost image elimination.
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 eliminates ghost images, reduces production costs by eliminating the need for wedge films, and maintains high light transmittance and optical quality for the HUD projection.
Implementation Method 1
the electrically conductive coating... as a reflection surface for the p‑polarised radiation
Implementation Method 2
The projector irradiates the composite pane with p‑polarised radiation... at an angle of incidence of about 65°, which is near Brewster's angle for an air/glass transition
Data Source
AI summary
A projection arrangement for a head-up display (HUD), includes a composite pane, including an outer and an inner pane connected to one another via a thermoplastic intermediate layer, with an HUD region; an electrically conductive coating on the surface of the outer or inner pane facing the intermediate layer or within the intermediate layer; and a projector that is directed toward the HUD region. The radiation of the projector is p-polarised. The composite pane with the electrically conductive coating has reflectance of at least 10% relative to p-polarised radiation in the spectral range from 450 nm to 650 nm. The electrically conductive coating includes at least three electrically conductive layers, which are each arranged between two dielectric layers or layer sequences. The sum of the thicknesses of all electrically conductive layers is at most 30 nm and the electrically conductive layers have a thickness of 5 nm to 10 nm.