Near Eye Display Interface Window for Waveguide Light Management
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Solution Overview
Problem
Existing near eye displays and head up displays with 2D aperture expansion face issues with light reflection back into waveguides, causing image degradation due to air-gaps between waveguides, which are difficult to seal and maintain, leading to mechanical challenges and non-uniform illumination.
Innovation Solution
A near eye display design incorporating an air gap and an intermediate interface window with a transparent optical element and light absorbent elements, where the interface window projects beyond the input aperture of the second waveguide to prevent undesired light from entering, and includes a light absorbent cover or baffle to maintain total internal reflection and prevent dirt and humidity ingress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an air-gap is used between waveguides to maintain total internal reflection, then optical performance is improved, but mechanical stability deteriorates due to sealing difficulties
Solution Approach 1:
A sealing structure is introduced as an intermediary element between the first and second waveguides. This sealing structure fills the air-gap while maintaining the optical properties needed for total internal reflection, thereby preserving both optical performance and mechanical stability. The sealing structure acts as a mediator that resolves the contradiction between needing an air-gap for optics and needing mechanical continuity for stability.
2Stability of the object's composition
If waveguides are mechanically combined firmly, then mechanical stability is improved, but optical quality deteriorates due to non-uniform illumination
Solution Approach 1:
The sealing structure is designed with specific local properties: it is positioned only at the interface between waveguides where mechanical support is needed, while maintaining optical transparency in the regions where light propagation occurs. This localized approach allows mechanical stability to be enhanced at the interface without compromising the uniformity of illumination in the optical paths.
3Object-affected harmful factors
If the interface window projects beyond the input aperture, then prevention of undesired light entry is improved, but device complexity increases
Solution Approach 1:
The interface window is designed to serve multiple functions simultaneously: it provides the sealing function to maintain the air-gap, acts as a mechanical support structure, and extends beyond the aperture to prevent undesired light entry. By making the interface window multi-functional, the patent reduces overall device complexity compared to having separate components for each function.
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 prevents image degradation by ensuring total internal reflection within the first waveguide, maintains mechanical stability, and enhances optical quality by using a light absorbent element to secure additional components, thereby improving the overall performance of near eye displays.
Implementation Method 1
an air gap configured to enable total internal reflection within the first waveguide
Implementation Method 2
the interface window including a transparent optical element with a refractive index substantially the same as a refractive index of the second optical waveguide
Implementation Method 3
undesired light exiting the first waveguide is prevented from entering the second waveguide
Data Source
AI summary
A near eye display including: a first optical waveguide having a direction of elongation, at least one pair of parallel faces, and a first coupling-out mechanism; a second optical waveguide having an input aperture, a pair of parallel faces, and a second coupling out-mechanism; an optical coupling between the first optical waveguide and the second waveguide, the optical coupling including at least an air gap configured to enable total internal reflection within the first waveguide, and an interface window, the interface window comprising a transparent optical element with a refractive index substantially the same as a refractive index of the second optical waveguide; and wherein at least a portion of the interface window projects beyond the input aperture of the second optical waveguide such that undesired light exiting the first waveguide is prevented from entering the second waveguide.