Variable Aperture Assembly for HUD Projector Brightness-Contrast Balance
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Solution Overview
Problem
Head-up and head-worn displays face challenges in maintaining effective image visibility across a wide range of ambient light conditions without impairing the user's vision or causing thermal issues, particularly in environments like aircraft where brightness levels can vary significantly.
Innovation Solution
A projector with a variable aperture assembly that adjusts its geometry (size and/or shape) along the optical axis, allowing it to adapt to different ambient light conditions by selecting the appropriate aperture size for optimal performance, including modes for night and day operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed aperture size is used in the projector, then the device complexity is reduced, but the adaptability to different ambient light conditions deteriorates
Solution Approach 1:
The patent applies the Dynamics principle by implementing a variable aperture assembly that can dynamically change its aperture size based on ambient light conditions. The aperture assembly includes multiple aperture plates with different aperture sizes that can be selectively positioned in the optical path, allowing the projector to adapt to varying light environments (daytime, nighttime, twilight) while maintaining optimal image quality and contrast ratio.
2Illumination intensity
If the aperture size is increased to improve light output, then the brightness is improved, but the contrast ratio deteriorates
Solution Approach 1:
The variable aperture assembly dynamically adjusts the aperture size to optimize the balance between brightness and contrast ratio. In low ambient light conditions, a smaller aperture is selected to maintain high contrast ratio, while in high ambient light conditions, a larger aperture is selected to ensure sufficient brightness. This dynamic adjustment resolves the contradiction between brightness and contrast ratio.
3Reliability
If the aperture size is decreased to improve contrast ratio, then the contrast ratio is improved, but the brightness deteriorates
Solution Approach 1:
The system uses ambient light sensors to detect lighting conditions and automatically selects the appropriate aperture size. In nighttime or low-light conditions, a smaller aperture is positioned in the optical path to maximize contrast ratio, while in daytime or high-light conditions, a larger aperture is selected to ensure adequate brightness. This dynamic selection resolves the contradiction between contrast ratio and brightness.
Data Source
AI summary
A projector for use in a head-up or head-worn display is described. The projector comprises a display source, an output screen, and a variable aperture assembly. The variable aperture assembly is positioned on an optical axis between the display source and the output screen and is adjustable to change a geometry (e.g. size and/or shape) of an aperture that is aligned with the optical axis and thereby change the efficiency of the optical train of the projector. The geometry that is changed may be a physical geometry or an effective geometry.