Polarization-Converting Windshield Projection Surface for HUD Visibility
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Solution Overview
Problem
Existing field-of-view display devices in motor vehicles project images predominantly in s-polarized light, making them dim when viewed through p-polarized sunglasses, and often create double images due to preferential reflection and refraction properties of windshields.
Innovation Solution
A projection surface with a first and second reflection surface and a λ/4 or λ/2 polarizing agent between them, altering the polarization of light components to enhance reflection efficiency and visibility with polarized sunglasses, while aligning main and secondary images without offset.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the projection surface uses a windshield with reflective properties for head-up display, then the projected image can be superimposed on the real surroundings, but the image becomes very dim when viewed through polarized sunglasses
Solution Approach 1:
The patent changes the polarization parameter of the projected light from s-polarized to p-polarized light. This parameter change allows the light to pass through polarized sunglasses (which typically block s-polarized light) while maintaining visibility. The projection device is configured to emit p-polarized light onto the windshield, which then reflects toward the driver's eye through the polarized sunglasses, solving the dimness problem.
Solution Approach 2:
The patent employs a composite optical system combining the windshield (with specific reflective properties), polarizing filters, and the projection device. The windshield acts as a partial reflector and partial transmitter, while the polarizing elements control the polarization state of light. This composite arrangement enables the projected image to be visible both directly and through polarized sunglasses by managing the interaction between these different optical components.
2Reliability
If the windshield inner and outer surfaces are slightly tilted to one another, then the main image and secondary image can be superimposed, but the device complexity increases
Solution Approach 1:
The patent introduces an asymmetric tilt between the inner and outer surfaces of the windshield. Instead of keeping both surfaces parallel, one surface is tilted relative to the other by a small angle. This asymmetric configuration causes the reflection paths from the two surfaces to converge, allowing the main image and secondary image to be superimposed at the same location, thereby improving image clarity without requiring additional optical components.
3Illumination intensity
If the projection device emits s-polarized light preferentially, then the projected image is visible on the windshield, but the image becomes dim when viewed through p-polarized sunglasses
Solution Approach 1:
The patent inverts the conventional approach by projecting p-polarized light instead of s-polarized light. Conventional HUD systems project s-polarized light which reflects well from the windshield but is blocked by p-polarized sunglasses. By inverting the polarization to p-polarized light, the system ensures compatibility with polarized sunglasses while maintaining adequate reflection from the windshield, thus eliminating the harmful interference effect.
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
Increases the proportion of p-polarized light reflected, enhancing image visibility with polarized sunglasses and ensuring clear image representation by superimposing main and secondary images.
Implementation Method 1
a polarizing means arranged between the first reflection surface and the second reflection surface for changing a polarization of light transmitted to the projection surface
Implementation Method 2
a first reflection surface, in particular an inner side of the projection screen, for preferentially reflecting a light component polarized in a first polarization type from a projected image
Implementation Method 3
a second reflection surface, in particular an outer side of the projection screen, for reflecting a light component polarized in the first polarization type from a projected image
Implementation Method 4
a birefringent layer disposed in the windshield, the birefringent layer being capable of causing a change in the polarization of light emerging from a projector of the head-up display
Data Source
Figure 1
AI summary
The invention relates to a projection surface (3) for a protection pane (4), in particular for a windshield of a motor vehicle, comprising: a first reflection surface (I) for preferably reflecting a light component of a projected image polarized in a first polarization manner and for preferably transmitting a light component of a projected image polarized in a second polarization manner, a second reflection surface (A) for reflecting a light component of the projected image polarized in the first polarization manner and for preferably transmitting a light component of a projected image polarized in the second polarization manner, a polarization means (34) arranged between the first reflection surface (I) and the second reflection surface (A) for changing a polarization of light passing through the projection surface (3) such that a light component of the second polarization manner passing through the first reflection surface (I) is changed into a light component of the first polarization manner and is reflected at the second reflection surface (A) and, when passing through the polarization means (34) again, is changed into a light component of the first polarization manner, which passes through the first reflection surface (I).