Vehicle Head-Up Display Thermal Protection via Polarized Sunlight Rejection
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Solution Overview
Problem
Existing head-up displays for motor vehicles face issues with solar radiation causing excessive heating of the image generating device, which can disrupt the image generation and impair the device's function.
Innovation Solution
A reflective linear polarizer is placed in the beam path between the image generating device and the windshield, aligned with the polarization direction of the device's output, to reflect non-compatible polarized sunlight away from the device, and the image generating device and optics are housed within a hood with a translucent cover plate containing the polarizer for protection and assembly simplicity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a cold light mirror is arranged in the beam path to reduce solar radiation, then some heat reduction is achieved, but the image generating device is still heated to temperatures that disrupt the image
Solution Approach 1:
The patent applies parameter changes by introducing a polarizing filter that selectively blocks polarized sunlight based on its polarization angle. This optical parameter change allows the system to reject a specific portion of solar radiation (polarized light) while maintaining the transmission of useful light for the head-up display, thereby reducing heat without compromising image quality
Solution Approach 2:
The polarizing filter acts as an intermediary element between the sunlight and the image generating device. It selectively interacts with the polarized components of sunlight, blocking harmful polarized radiation while allowing non-polarized or differently polarized light to pass through, thus mediating the thermal load on the device
2Temperature
If a reflective linear polarizer is added to the beam path to reflect polarized sunlight, then solar radiation heating is significantly reduced, but the device complexity increases
Solution Approach 1:
The polarizing filter serves multiple functions simultaneously: it acts as a heat rejection element by blocking polarized sunlight, and it maintains optical transparency for the display beam path. This multi-functionality reduces the need for separate cooling mechanisms, thereby managing complexity while achieving thermal protection
Solution Approach 2:
The patent utilizes the polarization state of light as a controllable parameter to differentiate between useful light (display beam) and harmful light (solar radiation). By changing the optical parameter of polarization selectivity, the system achieves thermal management without requiring complex mechanical or thermal control systems
3Reliability
If the image generating device and imaging optics are arranged within a hood with a translucent cover plate, then protection against external influences is improved, but assembly complexity increases
Solution Approach 1:
The patent merges the protective hood structure with the polarizing filter assembly into a single integrated unit. The polarizing filter is incorporated into the cover plate or housing structure, eliminating the need for separate assembly steps and reducing manufacturing complexity while maintaining protective functionality
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 configuration significantly reduces solar radiation heating, ensuring high performance and preventing impairment of the image generating device, with only 30% of sunlight reaching the device, minimizing heat-induced issues.
Implementation Method 1
A reflective linear polarizer is arranged in the beam path of the beam between the image generating device and the windshield, the polarization direction of which corresponds to the polarization direction of the beam emitted by the image generating device and which reflects light of a different polarization radiating on the beam path from the windshield to the image generating device.
Implementation Method 2
If the radiation 13 of the sun 14 strikes the windshield 10 from outside at an angle close to the Brewster angle α, this sunlight is partially polarized by the windshield 10.
Implementation Method 3
a reflective linear polarizer...which reflects light of a different polarization radiating on the beam path from the windshield to the image generating device
Data Source
Figure 1
Figure 2
AI summary
The invention relates to a head-up display for a motor vehicle, comprising an image generation device from which beams of an image are linearly polarized by a polarizer 4 arranged on the light output side of the image generation device, guided via imaging optics 8 to a windshield 10, and directed from the windshield 10 towards the driver of the motor vehicle. A reflective linear polarizer 5 is arranged in the beam path 6 of the beam between the image generation device and the windshield 10. The polarization direction of the reflective linear polarizer 5 corresponds to the polarization direction of the beam emitted by the image generation device and reflects light of a different polarization radiating from the windshield 10 to the image generation device along the beam path 6.