Folded Optical System Glare Trap Mitigation
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Solution Overview
Problem
Existing optical systems, particularly in augmented reality Heads-Up Displays (HUDs), suffer from glare caused by the reflection of sunlight and other external light sources, which overlaps with the HUD optical path, making it difficult to block glare without obstructing the projected image.
Innovation Solution
The optical system incorporates an imager, a reflective polarizer, a primary mirror, and a glare trap, which is designed to transmit at least some incident light rays while trapping others, ensuring that no more than about 2% of the transmitted incident light ray exits the system, effectively mitigating glare.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a traditional optical path design is used, then the optical system is simple, but glare from external light sources cannot be effectively blocked
Solution Approach 1:
The harmful reflected light rays are extracted and redirected to a dedicated glare trap location separate from the main optical path. The glare trap is positioned at a location where reflected rays naturally converge, allowing glare removal without interfering with the primary image transmission path.
Solution Approach 2:
A reflective element (such as a mirror or beam splitter) is introduced as an intermediary to redirect reflected light rays away from the optical path. This intermediary component redirects glare to the glare trap while allowing the main optical path to remain relatively simple and uninterrupted for image transmission.
2Object-affected harmful factors
If a glare blocking element is added to block external light, then glare is reduced, but the projected image becomes obstructed
Solution Approach 1:
The optical system is segmented into distinct functional zones: a main optical path for image transmission and a separate glare trap location for capturing reflected light. This segmentation allows independent optimization of each function without mutual interference.
Solution Approach 2:
The solution moves the glare blocking function to a different spatial dimension by positioning the glare trap at a location where reflected rays naturally converge, rather than placing a blocking element in the direct path of the projected image. This dimensional separation allows both functions to coexist.
3Volume of moving object
If the optical path is folded to reduce system size, then compactness is achieved, but glare mitigation becomes more difficult
Solution Approach 1:
The glare trap functionality is merged with the existing folded optical path structure by positioning it at a location where reflected rays naturally converge within the compact arrangement. This integration allows glare mitigation without requiring additional space or complex modifications to the folded path.
Solution Approach 2:
The folded optical path's natural reflection geometry is utilized to direct glare rays to the glare trap location, allowing the system's own structure to serve the glare mitigation function without requiring external or additional components.
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 effectively reduces glare by allowing only a minimal amount of external light to interfere with the virtual image, while maintaining the clarity and visibility of the projected image for the viewer.
Implementation Method 1
a reflective polarizer disposed between a glare trap and a display
Implementation Method 2
a primary mirror... after the emitted image is reflected by the primary mirror
Data Source
AI summary
An optical system includes an imager, a reflective polarizer, a primary mirror, and a glare trap. The optical system is configured to display a virtual image of an image emitted by the imager after the emitted image is reflected by the primary mirror and transmitted by the reflective polarizer and exits the system through the glare trap. For every light ray emitted by the imager and which exits the system through the glare trap along a first direction, when a light ray is incident on the glare trap along a second direction coincident with and opposite to the first direction, the glare trap transmits at least some of the incident light ray, such that if the transmitted incident light ray attempts to exit the optical system through the glare trap, the glare trap traps the transmitted incident light, transmitting no more than about 2% of the transmitted incident light ray.