Windshield Head Up Display With Half-Wave Plate
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Solution Overview
Problem
Conventional head-up displays (HUDs) in vehicles are not easily viewable by drivers wearing polarized sunglasses, and they often require a wedged windshield to function effectively, which can lead to increased veiling glare and reflection issues.
Innovation Solution
Incorporating a half-wave plate sandwiched inside the windshield, oriented at about 45° from the vertical axis, to enable the HUD image to be seen by drivers wearing polarized sunglasses, and to reduce the need for a wedged windshield by reflecting light primarily from either the inside or outside surface of the windshield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional HUD projector emits linearly polarized light, then the virtual image can be formed on the windshield, but drivers wearing polarized sunglasses cannot see the image
Solution Approach 1:
The patent changes the polarization parameter of the light by introducing a half-wave plate that rotates the polarization angle by 90 degrees. This parameter transformation allows the reflected light to be transmitted through polarized sunglasses, resolving the incompatibility between HUD visibility and sunglass compatibility
Solution Approach 2:
The half-wave plate acts as an intermediary optical element between the HUD projector and the windshield. It modifies the polarization state of the light in a controlled manner, enabling the system to work harmoniously with drivers' polarized sunglasses without requiring them to remove or replace them
2Reliability
If a wedged windshield is used to reflect HUD light, then the virtual image can be formed, but veiling glare and reflection issues increase
Solution Approach 1:
The patent changes the polarization parameter of the incident light using a half-wave plate, which alters how the light interacts with the windshield surfaces. This parameter change enables effective reflection from a non-wedged windshield while minimizing the harmful veiling glare that typically results from windshield reflections
3Illumination intensity
If the windshield reflectivity to p-polarized light is increased, then the HUD image brightness is improved, but the ability to view with polarized sunglasses is reduced
Solution Approach 1:
The patent applies a parameter transformation by rotating the polarization angle of the light by 90 degrees using the half-wave plate. This transforms p-polarized light into s-polarized light (or vice versa), allowing the system to maintain high reflectivity while ensuring compatibility with polarized sunglasses that typically block one polarization direction
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 allows drivers to view the HUD image clearly with conventional polarized sunglasses and eliminates the need for a wedged windshield, reducing glare and reflection issues while maintaining visibility of the virtual image.
Implementation Method 1
The windshield includes a half-wave plate. The half-wave plate can be oriented such that the axis of the half-wave plate is at an angle of about 45 degrees relative to the vertical axis of the windshield.
Implementation Method 2
A windshield reflects the light field 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 projector including a lens with a polarizer. The head up display projector emits a linearly polarized light field via the lens. A windshield reflects the light field such that the reflected light field is visible to a human driver of the motor vehicle as a virtual image. The windshield includes an outer plastic layer sandwiched between a half-wave plate and an outer glass layer. An inner plastic layer is sandwiched between the half-wave plate and an inner glass layer.