Anti-Reflective Coating for Vehicle Windshield Ghosting
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Solution Overview
Problem
Current head-up display systems suffer from ghosting due to secondary image reflections off windshields, which reduce image clarity, and existing solutions like wedge windshields or polarization films are either ineffective for high-resolution images or excessively costly.
Innovation Solution
A windshield with anti-reflective coatings applied to either surface, adjusting the index of refraction to optically remove or block unwanted reflections, thereby reducing ghosting and improving image clarity without the need for complex optical modeling or expensive materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional laminated windshields are used to reflect primary display images, then the head-up display system can be implemented, but secondary ghost images are reflected off the outer surface reducing image clarity
Solution Approach 1:
The patent applies an anti-reflective coating with a specific index of refraction (n=1.23) to the outer surface of the windshield. This parameter change in the optical properties of the surface selectively eliminates the secondary ghost image while maintaining the primary display image reflection, thereby improving image clarity without requiring complex wedge geometries or polarization systems.
2Object-generated harmful factors
If wedge windshields are used to superimpose images formed by two reflections, then ghosting may be reduced, but image registration is insufficient for higher resolution images
Solution Approach 1:
Instead of changing the geometric parameters of the windshield (wedge angle), the patent changes the optical parameter (index of refraction) of the anti-reflective coating. This approach maintains perfect image registration across the entire viewing pupil while eliminating ghosting, enabling support for high-resolution displays without the manufacturing precision issues associated with wedge windshields.
Solution Approach 2:
The patent replaces the mechanical/optical geometry-based solution (wedge windshield requiring precise angular alignment) with a material property-based solution (anti-reflective coating with specific index of refraction). This substitution eliminates the need for complex optical modeling and precise manufacturing tolerances while achieving the same ghost reduction effect.
3Object-generated harmful factors
If polarization-direction changing film is used to rotate S-wave into P-wave, then ghost images are reduced, but the system becomes more complex and expensive
Solution Approach 1:
The patent extracts and addresses only the specific problem of ghost image reflection from the outer windshield surface, rather than implementing a comprehensive polarization system. By applying a targeted anti-reflective coating with n=1.23 to the outer surface, the solution eliminates ghosting without requiring complex polarization-direction changing films, reducing overall system complexity while maintaining effectiveness.
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 anti-reflective coating effectively eliminates secondary images, enhancing image quality and reducing ghosting artifacts, allowing for clearer and more reliable head-up displays without the expense of specialized materials or complex designs.
Implementation Method 1
an anti-reflective coating provided on a surface of one of the first and second substrates... optically removes or blocks at least some light rays produced by an image source
Implementation Method 2
the index of refraction of such an anti-reflective coating may be adjusted so as to accomplish the selective optical removal or blocking of the undesired image
Data Source
Figure 1
Figure 2
Figure 3a~3b
AI summary
Certain example embodiments relate to a head-up display system for a vehicle having a windshield (30a). First and second substantially parallel spaced-apart substrates (2 and 4) sandwich a polymer-inclusive interlayer (6). An anti-reflective coating (32) is provided on a surface of one of the first and second substrates (2 and 4). The anti-reflective coating (32) is arranged so as to optically remove or block at least some of light rays produced by an image source (20) of the head-up display system so as to reduce the occurrence of multiple images being produced by the image source. The anti-reflective coating (32) is provided on a surface of the first or second substrate (2 or 4) opposite to the polymer-inclusive interlayer (6). In certain example embodiments, the polymer-inclusive interlayer (6) may include polyvinyl butyral and/or may have a substantially uniform thickness.