Waveguide Display DOE Layout to Reduce RGB Cross-Coupling
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Solution Overview
Problem
Existing waveguide displays suffer from significant cross-coupling between different color components, leading to sub-optimal display uniformity and modulation transfer function (MTF) degradation, particularly in systems utilizing multiple waveguide plates for RGB color models.
Innovation Solution
The waveguide display employs a configuration of diffractive optical elements (DOEs) that split the field of view into left and right portions, using intermediate DOEs to expand the exit pupil in two directions while minimizing direct downward coupling, and incorporates grating vectors with specific orientations to steer light towards the center, reducing cross-coupling between color components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple waveguide plates are used to support RGB color model, then color display capability is improved, but cross-coupling between color components increases leading to display uniformity degradation
Solution Approach 1:
The field of view is divided into left and right portions, with each portion being processed by separate intermediate DOEs before being recombined at the out-coupling DOE. This segmentation prevents cross-coupling between color components by isolating their propagation paths.
Solution Approach 2:
Different regions of the waveguide are assigned different functions: the in-coupling DOE region handles light input, intermediate DOE regions handle lateral propagation with specific grating vectors, and the out-coupling DOE region handles light output. This local differentiation optimizes performance in each region while minimizing cross-coupling.
2Area of stationary object
If intermediate DOEs are used to expand exit pupil, then field of view is improved, but dark areas or stripes appear in the out-coupling DOE region
Solution Approach 1:
The intermediate DOEs act as intermediary elements that laterally propagate light from the in-coupling DOE to the out-coupling DOE. By using grating vectors oriented at specific angles, they steer light back toward the center of the waveguide, ensuring uniform illumination across the out-coupling region while expanding the exit pupil.
3Device complexity
If direct downward coupling is used to simplify light propagation, then device complexity is reduced, but cross-coupling between color components increases
Solution Approach 1:
Instead of direct downward coupling in a single dimension, the system uses lateral propagation in the horizontal dimension followed by vertical out-coupling. This dimensional transition allows for better control of light paths and reduced cross-coupling between color components while maintaining manageable device complexity.
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 configuration enhances display uniformity and improves MTF by minimizing cross-coupling, resulting in an expanded field of view with reduced dark areas and improved image quality.
Implementation Method 1
An in-coupling diffractive optical element (DOE) disposed on the substrate and configured to in-couple incident image light into the waveguide; a left intermediate DOE disposed on the substrate and optically coupled to the in-coupling DOE to receive image light for a left portion of the field of view
Implementation Method 2
a substrate of optical material configured as a waveguide for guiding image light in the near-eye display system
Data Source
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AI summary
A waveguide display includes multiple diffractive optical elements (DOEs) that are configured to in-couple image light, provide expanded exit pupil in two directions, and out-couple the image light to a user. An in-coupling DOE is configured to split the full field of view (FOV) of the image light into left and right portions. The left and right FOV portions are respectively propagated laterally in left and right directions in intermediate DOEs which comprise upper and lower portions. The intermediate DOEs provide for exit pupil expansion in a horizontal direction while coupling light to an out-coupling DOE. The out-coupling DOE provides for exit pupil expansion in a vertical direction and out-couples image light with expanded exit pupil for the full FOV. The intermediate DOE portions are configured to steer image light back towards the center of the waveguide to avoid dark areas or stripes in portions of the out-coupling DOE.