Integral Spacer Waveguide Stacks for AR Alignment and Light Leakage
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Solution Overview
Problem
Challenges exist in producing augmented reality (AR) technologies that provide a comfortable and natural presentation of virtual image elements amidst real-world imagery due to complexities in human visual perception, and existing waveguide stacking methods face issues with precise alignment, mechanical stability, and light leakage.
Innovation Solution
The use of integral spacers within waveguides, bonded with low- and high-viscosity adhesives, provides consistent separation and mechanical stability, while edge treatments like light-absorbing materials reduce light leakage, enhancing optical performance and image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If waveguides are stacked using conventional adhesive methods, then waveguides can be assembled, but alignment precision and mechanical stability are insufficient
Solution Approach 1:
The waveguide stack is divided into discrete waveguide layers with integral spacers that segment the structure into manageable units. Each waveguide includes its own spacers, allowing independent positioning and alignment before assembly, which improves both alignment precision and mechanical stability of the overall stack.
Solution Approach 2:
Integral spacers are pre-formed as part of each waveguide structure before assembly. This preliminary action ensures that spacing and alignment features are already in place, eliminating the need for complex alignment procedures during stacking and improving both manufacturing precision and mechanical stability.
2Reliability
If waveguides are stacked with adequate separation, then mechanical stability is improved, but light leakage between waveguides increases
Solution Approach 1:
The spacer structure is designed with varying properties: the bulk spacer material provides mechanical separation and stability, while the lateral sides are specifically configured with adhesive application surfaces. This local differentiation allows the same spacer structure to simultaneously provide mechanical stability and prevent light leakage through targeted adhesive bonding at critical interfaces.
Solution Approach 2:
Adhesive is introduced as an intermediary material between the spacer and waveguide surfaces. This adhesive mediator fills the gap between mechanical separation requirements and optical isolation needs, bonding the waveguides while maintaining the spacing structure that prevents light leakage.
3Manufacturing precision
If complex alignment procedures are used, then alignment precision is improved, but manufacturing complexity increases
Solution Approach 1:
The integral spacers are designed to self-align waveguides during assembly. The spacers protrude from each waveguide and fit into corresponding recesses or positions in adjacent waveguides, creating a self-aligning mechanism that eliminates complex external alignment procedures while maintaining high alignment precision.
Solution Approach 2:
The spacer and waveguide are merged into a single integral structure, manufactured as one piece. This combination eliminates the need for separate spacer components and their associated alignment procedures, simplifying manufacturing while maintaining precise spacing and alignment through the integrated design.
4Reliability
If adhesive with high viscosity is used, then adhesive retention is improved, but precise positioning and air bubble removal become difficult
Solution Approach 1:
The spacer structure is designed with predetermined adhesive application zones on its lateral sides. Adhesive is applied in advance to these specific zones before waveguide assembly, ensuring proper retention while maintaining the fluidity needed for precise positioning and bubble removal during the assembly process.
Solution Approach 2:
Different regions of the spacer are designed with different functions: the top surface provides spacing, while the lateral sides are specifically configured as adhesive application surfaces. This local differentiation allows adhesive to be applied in controlled amounts at precise locations, improving both retention and positioning accuracy.
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 achieves consistent optical performance and improved image quality by ensuring precise spacing and reduced light leakage, simplifying manufacturing and enhancing the functionality of AR and VR display systems.
Implementation Method 1
an adhesive provided on a top surface of the spacer, the adhesive attaching the spacer to the second major surface of the second waveguide
Implementation Method 2
The adhesive comprises a light absorber. In some embodiments, the adhesive is doped with a black colorant.
Data Source
AI summary
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 or casting. The spacers are disposed on one or more major surfaces of the waveguides and define a distance between immediately adjacent waveguides. Adjacent waveguides may be bonded using adhesives on the spacers. The spacers may fit within indentations of overlying waveguides. In some cases, the spacers may form one or more walls of material substantially around a perimeter of an associated waveguide. Vent holes may be provided in the walls to allow gas flow into and out from an interior volume defined by the spacers. Debris trapping structures may be provided between two walls of spacers to trap and prevent debris from entering into the interior volume.