Optical Laminate Structure for Head-Up Display Visibility
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Solution Overview
Problem
Head-up display systems face challenges in achieving high transmittance and reflectance simultaneously due to the trade-off between these two properties, particularly in windshields where high reflectance is difficult to implement while maintaining legal visible light transmittance requirements, and existing light control films do not adequately address polarization conversion performance.
Innovation Solution
An optical laminate structure comprising a light control laminate with a light reflection layer, a first quarter wave plate, and a second quarter wave plate, where the light reflection layer includes a cholesteric liquid crystal layer, and the quarter wave plates are strategically positioned and angled to optimize polarization conversion, allowing for efficient conversion of incident polarized light to its original state, thereby enhancing visibility of the display image.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a light reflection film is applied to the windshield to improve display image visibility, then reflectance is improved, but visible light transmittance deteriorates and may violate legal requirements
Solution Approach 1:
The patent applies a quarter wave plate to change the polarization state of light, converting linearly polarized light to circularly polarized light. This parameter change in light polarization allows the reflection film to selectively reflect display light while maintaining high transmittance for natural light, resolving the contradiction between visibility and transmittance
Solution Approach 2:
The patent creates a composite optical system combining a light reflection film with a quarter wave plate. This composite structure enables the windshield assembly to simultaneously achieve high reflectance for display images and high visible light transmittance, complying with legal requirements while improving visibility
2Measurement precision
If the angle between the polarization axis and slow axis is optimized for polarization conversion, then polarization conversion performance is improved, but the structural configuration becomes more complex
Solution Approach 1:
The patent specifies precise angular parameters (5° ≤ angle < 45°) for the quarter wave plate configuration to optimize polarization conversion. By defining specific parameter ranges rather than exact values, the patent achieves high polarization conversion performance while maintaining manufacturing flexibility and avoiding excessive 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 optical laminate structure significantly improves polarization conversion performance, allowing for higher visibility of the display image while maintaining high transmittance and reflectance, reducing the occurrence of double images, and ensuring compliance with legal transmittance requirements.
Implementation Method 1
the light reflection layer includes a right-handed circularly polarized light reflection layer or a left-handed circularly polarized light reflection layer
Implementation Method 2
The quarter wave plate is known to have an effect of converting incident linearly polarized light to circularly polarized light or incident circularly polarized light to linearly polarized light
Data Source
AI summary
An optical laminate structure includes a light control laminate having at least one light reflection layer, a first quarter wave plate laminated on one of surfaces of the light reflection layer, and a second quarter wave plate laminated on another surface of the light reflection layer. The light reflection layer includes a right-handed circularly polarized light reflection layer or a left-handed circularly polarized light reflection layer, and an angle formed by a polarization axis of the S-polarized light or P-polarized light incident from a position inclined from an axis perpendicular to a surface of the light control laminate by 45° or more and 65° or less and a slow axis of the first quarter wave plate on a side to which the S-polarized light or P-polarized light is incident is 5° or more and less than 45°.