Variable Transmission Combiner for Head-Up Display Visibility
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Solution Overview
Problem
Head-up displays struggle to maintain visibility over very bright backgrounds, as the projected image becomes difficult to see due to high external brightness.
Innovation Solution
A see-through display system with a combiner that has variable light transmission and reflection capabilities, coupled with a light sensor assembly and controller to adjust the amount of light transmitted or reflected based on measured brightness, ensuring the image remains visible by adapting to different background conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the combiner maintains fixed light transmission properties, then the structure is simple, but the virtual image becomes invisible over bright backgrounds
Solution Approach 1:
The combiner transitions from a static structure to a dynamic one by incorporating variable light transmission properties. The combiner can adjust its light transmission level based on ambient conditions, allowing it to adapt to different background brightness levels and maintain virtual image visibility while managing the complexity through controlled variability.
Solution Approach 2:
The system changes the light transmission parameter of the combiner based on measured ambient brightness. By adjusting this physical parameter dynamically, the combiner maintains optimal contrast between the virtual image and the background across varying lighting conditions, resolving the contradiction between adaptability and structural simplicity.
2Illumination intensity
If the combiner increases light reflection to improve image visibility, then the virtual image becomes more visible, but less external light can be seen through the combiner
Solution Approach 1:
The combiner dynamically adjusts its light reflection and transmission properties based on ambient conditions. When external brightness is high, the combiner increases reflection to enhance virtual image visibility; when external brightness is low, it increases transmission to maintain viewability of the external scene. This dynamic adjustment resolves the contradiction between image visibility and external scene viewability.
Solution Approach 2:
The system changes the optical parameters of the combiner (light reflection and transmission levels) based on measured ambient brightness. This parameter adjustment allows the combiner to optimize both virtual image brightness and external scene viewability according to prevailing lighting conditions, eliminating the need to choose between the two conflicting requirements.
3Adaptability or versatility
If a light sensor assembly is added to measure brightness, then the system can adapt to background conditions, but the device complexity increases
Solution Approach 1:
The light sensor assembly provides feedback about ambient brightness conditions to the controller, which then adjusts the combiner's light transmission properties accordingly. This feedback loop enables the system to automatically adapt to different background brightness levels, maintaining optimal virtual image visibility while using a relatively simple sensor-controller-actuator architecture that minimizes the increase in device 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 system effectively maintains the visibility of the virtual image by adjusting light transmission and reflection, allowing the image to be seen clearly over various background brightness levels, including very bright environments.
Implementation Method 1
a combiner that is configured to reflect rays of the generated image in a field of view of the occupant to create a virtual image
Implementation Method 2
a light sensor configured to measure brightness
Data Source
Figure 1
Figure 2A
Figure 2B~3B
AI summary
A see-through display system includes an image generator configured to emit a generated image for viewing by a vehicle occupant. A combiner is configured to reflect the generated image in a field of view of the occupant to create a virtual image. The combiner has variable light transmission and/or reflection capability. A light sensor assembly is electrically coupled to the combiner, which includes a light sensor configured to measure brightness, preferably as viewed behind the virtual image. A controller is configured to interpret the brightness measured by the light sensor and adjust the amount of light transmitted through the combiner based on the brightness.