Single-Layer Waveguide Pupil Expansion Without Multi-Layer Haze
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Solution Overview
Problem
Existing waveguide displays require multiple layers for dual axis expansion, leading to increased thickness, weight, and haze, which is unacceptably large for practical display applications.
Innovation Solution
A compact dual axis expansion waveguide using a first waveguide with an input coupler, fold grating, and output grating, where at least one of the gratings is a rolled k-vector grating, allowing for dual interaction and pupil expansion in orthogonal directions without the need for multiple layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple layers are used for dual axis expansion, then pupil expansion capability is improved, but thickness and weight increase unacceptably
Solution Approach 1:
The patent combines multiple grating functions into a single layer structure. Specifically, it integrates the input coupler, fold grating, and output grating into one waveguide layer, eliminating the need for separate layers for each function. This merging approach maintains dual axis expansion capability while reducing overall waveguide thickness and weight.
Solution Approach 2:
The single waveguide layer performs multiple functions simultaneously: it acts as the input coupler for launching light, contains the fold grating for vertical pupil expansion, and includes the output grating for horizontal pupil expansion. This multi-functional design eliminates the need for multiple specialized layers while achieving comprehensive dual axis expansion.
2Adaptability or versatility
If multiple layers are used for dual axis expansion, then pupil expansion capability is improved, but device weight increases
Solution Approach 1:
The patent merges multiple grating structures into a single integrated waveguide layer, eliminating redundant materials and reducing overall device weight. The single layer configuration maintains all necessary expansion functions without the additive weight of multiple separate layers.
3Adaptability or versatility
If multiple layers are used for dual axis expansion, then pupil expansion capability is improved, but manufacturing complexity and haze increase
Solution Approach 1:
The patent consolidates multiple grating functions into a single manufacturable layer, reducing manufacturing steps and minimizing interface-related haze. The single layer approach eliminates alignment tolerances and bonding complexities associated with multiple layers, while still achieving comprehensive dual axis expansion through integrated grating designs.
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 provides a low-cost, efficient, and compact dual axis expansion, reducing thickness and weight while maintaining a large eyebox and field of view, suitable for near-eye displays and sensor applications.
Implementation Method 1
The input coupler is configured to receive collimated first wavelength light from an Input Image Node (IIN) and to cause the light to travel within the first waveguide via total internal reflection between the first surface and the second surface
Implementation Method 2
The fold grating is configured to provide pupil expansion in a first direction and to direct the light to the output grating via total internal reflection between the first surface and the second surface
Implementation Method 3
The output grating is configured to provide pupil expansion in a second direction different than the first direction and to cause the light to exit the first waveguide from the first surface or the second surface
Data Source
AI summary
An optical display comprises: a first waveguide comprising a first surface and a second surface, an input coupler, a fold grating, and an output grating. The input coupler receives collimated first wavelength light from an Input Image Node causes the light to travel within the first waveguide via total internal reflection between the first surface and the second surface to the fold grating. The fold grating provides pupil expansion in a first direction directs the light to the output grating via total internal reflection between the first surface and the second surface. The output grating provides pupil expansion in a second direction different than the first direction and causes the light to exit the first waveguide from the first surface or the second surface. At least one of the input coupler, fold grating and output grating is a rolled k-vector grating, and the fold grating is a dual interaction grating.