HUD Optical Layout Using Beam Splitting and Freeform Mirror Correction
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Solution Overview
Problem
HUD systems face challenges with image rotation and ghosting due to off-center placement, leading to increased complexity, cost, and alignment issues, and require additional components to compensate for these effects.
Innovation Solution
A single heads-up display unit incorporating a projector, splitting element, and freeform mirror to correct optical issues such as ghosting and image rotation, allowing for precise alignment and versatile use across different applications without additional components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the HUD unit is placed off-center from the combiner/windshield to reduce size and accommodate other components, then the HUD unit can be made smaller and fit better in the vehicle, but the projected image appears rotated to the user
Solution Approach 1:
A freeform mirror is introduced as an intermediary optical element between the projector and combiner. This mirror corrects the image rotation caused by off-center placement, allowing the HUD unit to be positioned away from the center while maintaining proper image orientation for the user.
2Ease of operation
If the HUD unit is physically rotated to reduce image rotation effect, then the image orientation is improved, but alignment of other projection features becomes complex leading to lower resolution, brightness differences, and reduced contrast
Solution Approach 1:
Instead of rotating the entire HUD unit, a freeform mirror is used as an intermediary to correct image orientation. This approach maintains the projector's alignment with the combiner, preserving resolution, brightness uniformity, and contrast while achieving the desired image orientation.
Solution Approach 2:
The optical correction function is separated from the projector unit itself and implemented through a dedicated freeform mirror element. This segmentation allows the projector to remain properly aligned while the mirror handles the orientation correction independently.
3Ease of operation
If additional components are added to the HUD unit to compensate for rotation effects, then image orientation is corrected, but the cost and complexity of the HUD unit increases
Solution Approach 1:
The freeform mirror is integrated into the existing HUD unit structure, combining the orientation correction function with the projector assembly. This merging approach corrects image rotation without requiring separate external components, thereby limiting the increase in complexity and cost.
4Object-affected harmful factors
If the combiner/windshield is manufactured with a wedged shape to reduce ghosting, then ghosting effects are reduced, but the HUD unit must be paired with a specific windshield increasing resource burden and cost
Solution Approach 1:
A beam splitter is introduced as an intermediary element between the projector and combiner. This beam splitter corrects ghosting effects by properly managing light paths, allowing the combiner/windshield to maintain a standard non-wedged shape and enabling broader compatibility across different vehicle models.
Solution Approach 2:
The beam splitter design provides universal compatibility across different windshield types and vehicle models. By handling the ghosting correction through the beam splitter rather than requiring customized wedged windshields, the HUD unit can be paired with various standard windshields without increasing manufacturing complexity.
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 provides a compact, cost-effective, and versatile HUD unit that corrects ghosting and image rotation, improving alignment and reducing the need for additional components and adjustments, suitable for various vehicle types and placements.
Implementation Method 1
a splitting element operable to split the projected image ray into a plurality of image rays
Implementation Method 2
a freeform mirror operable to reflect the image rays
Data Source
AI summary
A heads-up display unit and a method of adjusting a projected image with the heads-up display unit comprising projecting, by a projector, an image comprising an image ray toward a combiner. The method further comprising splitting, by a splitting element, the image ray before the image ray hits the combiner. The method further comprising reflecting, by a freeform mirror, the image ray or the split image rays before the image hits the combiner. The method further comprising projecting the split and reflected image rays onto the combiner.