Windshield IR-Reflective Compound Interlayer Ghost Image Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Combining solar control and head-up display capabilities in windshields often results in unacceptable optical artifacts due to the reflection of visible light by infrared rejection films, leading to ghost images that compromise the performance of head-up display technologies.
Innovation Solution
A windshield design featuring a compound interlayer with a reflective layer and two wedge polymer layers, where the first wedge polymer layer causes visible light reflected from the reflective layer to overlap the primary image, and the second wedge polymer layer causes visible light reflected from the outer face of the outer rigid substrate to also overlap the primary image, minimizing ghost image separation for all driver heights.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If infrared reflecting films are incorporated into windshields for solar heat control, then energy management capability is improved, but visible light reflection causes ghost images that degrade head-up display performance
Solution Approach 1:
The reflective film is divided into multiple separate reflective zones positioned at different locations within the windshield laminate. Each zone reflects infrared radiation independently, and the segmentation allows optimization of each zone's optical properties to minimize visible light reflection and ghost image formation while maintaining overall solar heat rejection performance
Solution Approach 2:
Different regions of the reflective film are designed with locally optimized properties - certain zones have higher infrared reflectivity while others are designed to be more transparent in the visible spectrum. The reflective zones are strategically positioned and sized to match the optical path of infrared radiation while minimizing interference with head-up display light paths
2Adaptability or versatility
If multiple performance features are combined in a single windshield, then overall value to customer is improved, but individual performance elements work against each other requiring compromise
Solution Approach 1:
The reflective film is designed to perform multiple functions simultaneously: it provides solar heat rejection through infrared reflection, maintains visibility for head-up displays by minimizing visible light reflection, and can be configured with different reflective zone patterns to accommodate various windshield designs and applications
Solution Approach 2:
The windshield incorporates a composite structure combining transparent polymeric substrates with sputter-deposited metal stacks of alternating refractive index. This composite material approach enables the film to exhibit both infrared reflection and visible light transmission properties that neither material alone could achieve
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 design effectively reduces or eliminates ghost images caused by visible light reflections, providing a clearer and more readable virtual image for drivers of varying heights while maintaining the energy management capabilities of the windshield.
Implementation Method 1
These films often comprise transparent polymeric substrates onto which extremely thin metal stacks of alternating refractive index have been sputtered. The material selection and sputtering thicknesses are selected to favor reflection in the near and far infrared regions while minimizing effects to the visible light spectrum.
Implementation Method 2
The films employ Fabry-Perot sandwich interference filters, which are characterized by having three or more transparent layers of sputter-deposited metal, such as silver, directly contiguous with dielectric spacer layers
Implementation Method 3
the first wedge polymer layer causes visible light reflected from the reflective layer to overlap the primary image, and the second wedge polymer layer causes visible light reflected from the outer face of the outer rigid substrate to also overlap the primary image
Data Source
AI summary
Windshields are disclosed herein having an optical path, that include an inner rigid substrate, optically adjacent a first wedge polymer layer, that serves to reflect a primary image. A reflective layer is also provided, positioned in the optical path between the first wedge polymer layer and a second wedge polymer layer. The windshields are further provided with an outer rigid substrate, optically adjacent the second wedge polymer layer. The first wedge polymer layer causes visible light reflected from the reflective layer to overlap the primary image, and the second wedge polymer layer causes visible light reflected from an outer face of the outer rigid substrate to overlap the primary image.