Windshield Laminate Coating for Ghost-Free Large-Area HUD
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Solution Overview
Problem
Current Head-Up Display (HUD) systems in vehicles face challenges such as image distortion due to curved windshields, ghost images caused by refractive index mismatches, and the limitations of wedge interlayers and HUD films in correcting these issues, particularly with the increasing size and complexity of HUD displays, as well as the need for efficient defrosting capabilities without adding weight or cost.
Innovation Solution
A coated laminate with a multi-layer stack coating that is optimized for p-polarized reflectivity, combined with a HUD projector emitting primarily p-polarized light at the Brewster angle, eliminates ghost images and enables efficient defrosting using a standard 12V electrical system, while maintaining high visible light transmission and solar control properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a standard windshield with multiple glass layers and plastic interlayer is used, then the windshield provides structural strength and safety, but ghost images are generated due to refractive index mismatches at interfaces
Solution Approach 1:
The patent changes the refractive index parameter of the plastic interlayer by adding titanium dioxide pigment, increasing it from approximately 1.48 to 1.9. This parameter change eliminates the refractive index mismatch at the glass-plastic interfaces, preventing internal reflections and ghost image formation while maintaining the windshield's structural strength and safety properties
Solution Approach 2:
The patent creates a composite plastic interlayer material by combining polyvinyl butyral (PVB) with titanium dioxide (TiO2) pigment. This composite material achieves both the structural bonding function of the plastic interlayer and the high refractive index needed to eliminate ghost images, integrating multiple functions into a single material layer
2Temperature
If solar control coatings with low sheet resistance are applied to enable defrosting, then defrosting capability is improved, but ghost images are generated due to index of refraction mismatch
Solution Approach 1:
The patent modifies the refractive index parameter of the solar control coating by incorporating titanium dioxide, increasing it from approximately 1.48 to 1.9 to match the glass refractive index. This eliminates internal reflections and ghost images while maintaining the coating's low sheet resistance (0.8-5.0 ohms per square) for effective defrosting capability
Solution Approach 2:
The patent creates a composite solar control coating by combining transparent conductive materials with titanium dioxide pigment. This composite achieves both the electrical conductivity needed for defrosting and the high refractive index needed to eliminate ghost images, integrating thermal and optical functions in a single coating layer
3Ease of manufacture
If the HUD image is projected onto a curved windshield surface, then the windshield can be manufactured with standard curvature, but image distortion occurs because the projected image is not perpendicular to the surface
Solution Approach 1:
The patent changes the refractive index parameter of the plastic interlayer to 1.9, which alters the optical path and reflection characteristics at the glass-plastic interfaces. This parameter change eliminates internal reflections that cause ghost images, allowing standard curved windshields to display HUD images without distortion or ghosting artifacts
4Object-generated harmful factors
If wedge interlayer or HUD film is used to correct ghost images, then ghost image separation is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts and eliminates the root cause of ghost images by modifying the refractive index of the existing plastic interlayer through titanium dioxide addition. This eliminates the need for additional corrective components like wedge interlayers or HUD films, simplifying the overall laminate structure while effectively preventing ghost image formation
Solution Approach 2:
The patent makes the plastic interlayer material multi-functional by adding titanium dioxide, which simultaneously provides high refractive index for ghost image elimination, structural bonding between glass layers, and UV protection. This eliminates the need for separate corrective components, reducing device complexity
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 provides a clear, sharp, and bright HUD image across the entire windshield, eliminates ghost images, and allows for effective defrosting with reduced material and production costs, making it suitable for larger fields of view and integrating solar control and heating functions.
Implementation Method 1
The HUD projector is mounted such that the image is projected at or near the Brewster angle
Implementation Method 2
The coating is optimized for p-polarized reflectivity, combined with a HUD projector emitting primarily p-polarized light
Implementation Method 3
maintaining high visible light transmission and solar control properties
Implementation Method 4
The coating comprises a complex, multi-layer stack... tuned to transmit in the visible light range while reflecting in the infrared range
Implementation Method 5
The coating has a sheet resistance of under 1 ohm per square... allows for effective defrosting with reduced material and production costs
Implementation Method 6
The coating utilizes conductive and dielectric layers to achieve a sheet resistance of under 1 ohm per square
Data Source
AI summary
The invention provides for a coating which when used in conjunction with a p-polarization projector (26) and a windshield mounted such that the angle between projector is at or near the Brewster angle, a sharp image is produced with no ghost image. Further, the coating is suitable for use over the entire area of the windshield, has excellent solar control properties and has a low sheet resistance allowing it to be electrically defrosted at common automotive voltages.