Full-Color Waveguide Combiner With Embedded Metagrating for 114° FoV
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Solution Overview
Problem
Existing optical waveguides in AR/VR glasses have limited field of view (FoV) due to the angular bandwidth of the glass plate, with conventional systems achieving only up to 60 degrees, which is insufficient for a truly immersive experience, and existing full RGB combiners using two-waveguide architectures face challenges in fabricating structures with higher refractive indices.
Innovation Solution
A single waveguide system utilizing a metagrating with embedded reflective and transmissive diffractive couplers, where the spacing between couplers is less than 400nm, allowing for high field of view by coupling different colors and angles of incidence efficiently, and incorporating a metagrating within the waveguide to enhance fabrication possibilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a single waveguide system with metagrating is used, then field of view is improved (exceeding 114 degrees), but device complexity increases due to embedded reflective and transmissive diffractive couplers with spacing less than 400nm
Solution Approach 1:
The patent combines reflective and transmissive diffractive couplers into a single metagrating structure embedded within the waveguide. This merging of multiple coupling mechanisms into one integrated component enables the system to achieve a field of view exceeding 114 degrees while managing the complexity through unified structural design rather than separate components.
Solution Approach 2:
The metagrating is embedded within the waveguide structure, nesting the diffractive couplers inside the waveguide material. This nesting approach allows the complex optical structures to be integrated within the existing waveguide volume, achieving extended field of view without proportionally increasing external device dimensions.
2Area of stationary object
If reflective and transmissive diffractive couplers with spacing less than 400nm are used, then field of view is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent optimizes the spacing parameter between reflective and transmissive diffractive couplers to less than 400nm, which enables the metagrating to achieve extended field of view. This parameter change represents a deliberate optimization that balances the achieved performance benefit against the manufacturing precision requirements, using sub-400nm spacing as the critical design threshold.
3Area of stationary object
If conventional two-waveguide architecture is used, then field of view is limited (up to 60 degrees), but fabrication complexity is reduced
Solution Approach 1:
The patent merges the functionality of multiple waveguides into a single waveguide system by embedding reflective and transmissive diffractive couplers within one waveguide structure. This consolidation achieves extended field of view (exceeding 114 degrees) while simplifying the overall architecture compared to conventional two-waveguide systems, addressing both field of view expansion and manufacturing ease.
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 a high field of view exceeding 114 degrees, enabling a more immersive experience by efficiently coupling and expanding the exit pupil, while being resistant to mechanical damage and degradation.
Implementation Method 1
light propagates into the optical waveguide by TIR (for total internal reflection)
Implementation Method 2
a reflective diffractive in-coupler and a transmissive diffractive in-coupler provided in the waveguide
Data Source
Figure 1A
Figure 1B~1C
Figure 1D~1E
AI summary
In example embodiments, an optical system includes a waveguide having a first surface and a second surface substantially opposite the first surface. A reflective diffractive in-coupler is provided in the waveguide between the first and second surfaces for coupling blue light. A first transmissive diffractive in- coupler is provided in the waveguide between the reflective diffractive in-coupler and the second surface for coupling red light. Some embodiments further include a second transmissive diffractive in-coupler on the first surface for coupling blue light at high incident angles. Green light may be coupled by one or more of the in-couplers. The waveguide may further be provided with corresponding diffractive out-couplers for use in a waveguide display system.