Vehicle Display Reflective Polarizer for Lower Panel Heating
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional display systems in vehicles face thermal management issues due to sunlight heating the display panel, as cold mirrors reflect a significant amount of solar energy, which is not utilized for generating virtual images.
Innovation Solution
A reflective polarizer with multiple reflection bands is used to selectively reflect and transmit light based on polarization state, allowing a significant portion of incident light outside the emission spectra to be transmitted, thereby reducing heat buildup in the display panel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a cold mirror is used to reflect sunlight, then the virtual image display function is achieved, but thermal management deteriorates due to heat buildup in the display panel
Solution Approach 1:
The reflective polarizer is segmented into multiple reflection bands (blue, green, red) with distinct FWHMs that correspond to the display panel's emission spectra. This segmentation allows selective reflection of useful wavelengths while transmitting other wavelengths, thereby resolving the thermal management issue while maintaining virtual image display functionality.
Solution Approach 2:
The reflective polarizer exhibits different optical properties at different wavelengths - it reflects light within specific wavelength bands (matching the display panel's emission spectra) while transmitting light outside these bands. This local quality variation enables the system to maintain high virtual image brightness while reducing overall heat buildup by transmitting non-useful wavelengths.
2Temperature
If a reflective polarizer with multiple reflection bands is used, then thermal management is improved by transmitting non-useful wavelengths, but device complexity increases
Solution Approach 1:
The reflective polarizer performs multiple functions simultaneously: it acts as a polarizing beam splitter, a wavelength-selective filter, and a thermal management component. By integrating these functions into a single component with multiple reflection bands, the system achieves improved thermal management without proportionally increasing device complexity.
3Illumination intensity
If the reflective polarizer reflects more light within emission spectra, then virtual image brightness is improved, but energy loss increases due to reduced transmission of useful light
Solution Approach 1:
The reflective polarizer's reflection and transmission characteristics are optimized by adjusting the FWHMs of its reflection bands to precisely match the display panel's emission spectra. This parameter optimization ensures maximum reflection of useful wavelengths (improving virtual image brightness) while minimizing energy loss by transmitting wavelengths outside the emission spectra that would not contribute to the virtual image.
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 reflective polarizer effectively mitigates thermal management issues by reflecting a substantial portion of incident light within specific bands and transmitting light outside these bands, improving the display system's thermal performance.
Implementation Method 1
The display panel is configured to emit a polarized image light having a first polarization state
Implementation Method 2
The reflective polarizer is configured to receive and reflect the polarized image light as a first reflected polarized image light
Implementation Method 3
The reflective polarizer includes a reflection spectrum having substantially distinct blue, green and red reflection bands with respective blue, green and red FWHMs
Data Source
AI summary
A display system includes a display panel configured to emit polarized light having a first polarization state and substantially distinct blue, green and red emission spectra having respective blue, green and red full widths at half maxima (FWHMs). The display system includes a reflective polarizer configured to reflect the polarized image light as a first reflected polarized image light. For substantially normally incident light and for the first polarization state, the reflective polarizer has a reflectance of greater than about 60% across each of the blue and red FWHMs, and a transmittance of at least about 50% for at least a first wavelength between the FWHMs of the blue and green emission spectra, and for at least a second wavelength between the FWHMs of the green and red emission spectra.