Waveguide Spacers for AR Display Light Leakage
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Solution Overview
Problem
Conventional augmented reality and virtual reality display systems face challenges in providing a comfortable and natural presentation of virtual image elements amidst real-world imagery due to complexities in human visual perception, including issues with light leakage and structural stability in waveguide stacks.
Innovation Solution
The use of waveguides with integral spacers and diffractive optical elements, where spacers extend beyond the height of the diffractive optical elements to create a gap and provide mechanical stability, and the incorporation of light scattering features and absorbing materials to prevent light leakage, allowing for consistent optical performance and improved image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If waveguides are stacked closely together to reduce device size, then the overall compactness is improved, but light leakage between waveguides increases and structural stability deteriorates
Solution Approach 1:
The waveguide structure is segmented into discrete units separated by spacers. Each waveguide in the stack is divided into sections by the spacers, creating isolated optical paths that prevent light leakage while maintaining structural integrity. The spacers act as physical dividers that segment the waveguide stack into stable, independent units.
Solution Approach 2:
Spacers are introduced as intermediary elements between adjacent waveguides. These spacers serve as mediator structures that maintain precise separation distances, provide mechanical support, and prevent direct contact between waveguides that would cause light leakage and structural instability.
2Object-affected harmful factors
If spacers are made taller to increase separation between waveguides, then light leakage is reduced, but the overall device height increases
Solution Approach 1:
The spacers are positioned only at specific locations where light leakage is most problematic, rather than uniformly increasing the height of the entire waveguide structure. This localized approach to light blocking maintains compact overall dimensions while effectively preventing light leakage at critical interfaces between waveguides.
Solution Approach 2:
The spacers provide more separation than the minimum theoretical requirement by extending beyond the waveguide surfaces, creating an excessive action that ensures complete light blockage. This partial excess in spacer height guarantees light leakage prevention without requiring the full possible height, optimizing the balance between light blocking and compactness.
3Adaptability or versatility
If conventional waveguide stacks are assembled with separate components, then manufacturing flexibility is improved, but assembly complexity and potential misalignment increase
Solution Approach 1:
The spacers and waveguides are merged into a single integrated structure where the spacers are formed as integral parts of the waveguide bodies. This merging eliminates the need for separate assembly steps, reduces alignment complexity, and simplifies manufacturing while maintaining the optical separation benefits. The integrated structure ensures precise positioning without requiring complex assembly procedures.
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
This solution enhances the structural stability and optical performance of waveguide stacks, reducing light leakage and improving the perceived image quality by maintaining consistent separation between waveguides and preventing unwanted reflections, thus providing a more comfortable and realistic AR/VR experience.
Implementation Method 1
diffractive optical elements comprising a plurality of protrusions and intervening recesses on a major surface of the optically transmissive body
Implementation Method 2
The spacers separate the optically transmissive body from the overlying waveguide by a gap
Data Source
AI summary
In some embodiments, a head-mounted, near-eye display system comprises a stack of waveguides having integral spacers separating the waveguides. The waveguides may each include diffractive optical elements that are formed simultaneously with the spacers by imprinting. The spacers are disposed on one major surface of each of the waveguides and indentations are provided on an opposite major surface of each of the waveguides. The indentations are sized and positioned to align with the spacers, thereby forming a self-aligned stack of waveguides. Tops of the spacers may be provided with light scattering features, anti-reflective coatings, and/or light absorbing adhesive to prevent light leakage between the waveguides. As seen in a top-down view, the spacers may be elongated along the same axis as the diffractive optical elements. The waveguides may include structures (e.g., layers of light absorbing materials, rough surfaces, light out-coupling optical elements, and/or light trapping microstructures) along their edges to mitigate reflections and improve the display contrast.