Adjustable HUD Polarizer for Windshield Reflection and Sunglasses
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Solution Overview
Problem
Conventional head up displays (HUDs) become dim or invisible when drivers wear polarized sunglasses, especially on sunny days, due to the majority of light being in one polarization state, which is not effectively reflected by the windshield.
Innovation Solution
A rotatable polarizing device is integrated in the HUD system, allowing it to switch between P-polarized and S-polarized light states, increasing the percentage of P-polarized light emitted, thus enabling the HUD image to be visible even when wearing polarized sunglasses by rotating the polarizing device when the 'Polarized Sunglasses' button is activated.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the HUD projector emits circularly polarized or elliptically polarized light, then the image can be viewed with polarized sunglasses to some extent, but the windshield reflectivity to p-polarized light is small resulting in dim image
Solution Approach 1:
The patent applies a rotatable polarizing device that can dynamically change its polarization orientation between S-polarization and P-polarization states. When the driver wears polarized sunglasses, the system rotates the polarizing device to emit S-polarized light which can pass through the sunglasses. When the driver does not wear polarized sunglasses, the system emits P-polarized light for optimal windshield reflection. This dynamic adjustment resolves the contradiction between compatibility with polarized sunglasses and image brightness.
Solution Approach 2:
The patent changes the polarization parameter of the emitted light based on driver needs. By rotating the polarizing device, the system switches between different polarization states (S-polarization and P-polarization) to optimize both visibility through polarized sunglasses and overall image brightness, directly addressing the technical contradiction.
2Illumination intensity
If the interior surface of the windshield is coated with a reflective layer, then windshield reflectance increases, but veiling glare increases
Solution Approach 1:
The patent extracts the polarization control function from the windshield coating and places it in a rotatable polarizing device within the HUD projector. This allows the system to emit light with the appropriate polarization state without modifying the windshield, thereby avoiding veiling glare while still achieving high reflectance when needed.
3Adaptability or versatility
If a plastic lens with a wave plate is clipped over polarizing sunglasses, then the image can be viewed, but this is an inconvenient workaround
Solution Approach 1:
The patent makes the HUD system self-adaptive to the driver's sunglasses. The rotatable polarizing device automatically adjusts the polarization state of the emitted light to ensure visibility through polarized sunglasses, eliminating the need for the driver to manually add auxiliary lenses or make any adjustments to their sunglasses.
4Illumination intensity
If the polarizing device rotates to emit more P-polarized light, then the image brightness increases for non-sunglasses users, but the image becomes dim or invisible for users wearing polarized sunglasses
Solution Approach 1:
The rotatable polarizing device dynamically switches between emitting S-polarized light (for drivers wearing polarized sunglasses) and P-polarized light (for drivers not wearing sunglasses). This dynamic adaptation allows the system to optimize image brightness for each specific usage condition, resolving the contradiction between the two opposing requirements.
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 ensures that the HUD image remains visible and brighter for drivers wearing polarized sunglasses by adjusting the polarization state of the light emitted, overcoming the issue of dimness and invisibility caused by polarized lenses.
Implementation Method 1
A rotatable polarizing device is disposed in front of the liquid crystal display (LCD), and may rotate over an angular distance which results in the light shifting to either P-polarized light or S-polarized light
Implementation Method 2
A windshield reflects the light field from the polarizing device such that the reflected light field is visible to a human driver of the motor vehicle as a virtual image
Data Source
AI summary
A head up display arrangement for a motor vehicle includes a head up display module having a picture generation unit emitting a light field. A polarizing device is rotatable between at least a first rotational position and a second rotational position. The polarizing device receives the light field from the picture generation unit and emits the light field regardless of whether the polarizing device is in the first rotational position or the second rotational position. More of the light is emitted by the polarizer in a P-polarization state in the second rotational position than in the first rotational position. A windshield reflects the light field from the polarizing device such that the reflected light field is visible to a human driver of the motor vehicle as a virtual image.