Windshield HUD Projection Layer for Polarized Sunglasses
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Solution Overview
Problem
Head-up display systems using existing light reflecting films impair the functionality of polarized sunglasses by mixing polarization components, leading to reduced effectiveness in shielding glare from s-polarized light, which hinders driving safety.
Innovation Solution
A projection image display member comprising a phase difference layer, a selective reflection layer, and a polarization conversion layer with a helical alignment structure of liquid crystals, optimized in terms of pitch and thickness to maintain high visible light transmittance and suppress double images, while ensuring compatibility with polarized sunglasses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a light reflecting film is used in the head-up display system, then the projection image can be displayed on the windshield glass, but the functionality of polarized sunglasses is impaired due to mixing of polarization components
Solution Approach 1:
The light reflecting film is divided into multiple selective reflection layers, each responsible for reflecting a specific polarization component (p-polarization or s-polarization) at different wavelengths. This segmentation allows the film to selectively reflect projection light while maintaining the polarization characteristics of external light for sunglasses compatibility.
Solution Approach 2:
Different regions of the light reflecting film have different reflection characteristics tailored to specific functions: some layers are optimized for reflecting p-polarized projection light, while other layers are optimized for reflecting s-polarized external light, ensuring both head-up display visibility and sunglasses functionality are preserved.
2Ease of operation
If existing light reflecting films are used, then head-up display images can be projected, but glare shielding effectiveness is reduced due to polarization mixing
Solution Approach 1:
The film converts the potentially harmful s-polarized glare light into a beneficial reflected component by using selective reflection layers that specifically reflect s-polarized light at external light wavelengths. This allows the film to simultaneously display the head-up projection image and shield against glare, turning the polarization mixing problem into a solution where both functions are enhanced.
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 enhances the suitability of head-up display systems for use with polarized sunglasses by effectively reflecting p-polarization and reducing glare from s-polarized light, improving driving safety and visibility of projected images.
Implementation Method 1
a polarization conversion layer (11) that converts s-polarization into p-polarization, in which a helical alignment structure of a liquid crystal compound is fixed
Implementation Method 2
a selective reflection layer (12) that reflects light in a wavelength selective manner
Implementation Method 3
at least one phase difference layer (14)
Data Source
AI summary
Provided are a projection image display member having a high visible light transmittance, suppressing a double image of a display image, and having excellent suitability of polarized sunglasses for incident light reflected from external light, a windshield glass using the projection image display member, and a head-up display system. The problem is solved such that one or more phase difference layers, one or more selective reflection layers, and one or more polarization conversion layers are provided in this order, the polarization conversion layer being a layer in which a helical alignment structure of a liquid crystal compound is fixed, and the number of pitches x of the helical alignment structure and a film thickness y (μm) of the polarization conversion layer satisfying “0.3≤x≤7.0”, “0.5≤y≤6.0”, “y≤0.7x+3.2”, and “y≥0.7x−1.4”.