Offset Aperture Waveguides for Near-Eye Display Cross-Coupling
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Solution Overview
Problem
Near-eye display technology faces challenges in projecting right- and left-eye display images into a wide eye box while preserving image quality, particularly due to issues like vignetting and cross-coupling of images in head-worn display devices.
Innovation Solution
The use of layered optical waveguides with offset entry apertures to expand and overlap images, minimizing cross-coupling and enhancing image quality by directing component images into specific apertures, thereby reducing unwanted optical effects such as 'ghost' images and display-color impurity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If layered parallel optical waveguides are used to expand images into a wide eye box, then the field of view and eye box width are improved, but cross-coupling of images occurs between adjacent waveguides
Solution Approach 1:
The patent applies asymmetry by offsetting the entry apertures of adjacent waveguides from a common alignment. Specifically, the first entry aperture is positioned at a first location on the first waveguide while the second entry aperture is positioned at a second location on the second waveguide, where these locations are asymmetrically offset rather than aligned. This asymmetric positioning prevents the optical modes from overlapping and coupling between adjacent waveguides, thereby eliminating cross-coupling while maintaining wide eye box coverage.
Solution Approach 2:
The patent addresses cross-coupling by introducing a positional offset dimension between entry apertures of adjacent waveguides. Instead of relying solely on the lateral separation between waveguides, the invention adds a longitudinal offset dimension along the waveguide propagation direction. This dimensional approach creates spatial separation in the optical mode profiles, preventing evanescent field overlap and eliminating cross-coupling between adjacent waveguides.
2Device complexity
If entry apertures are aligned across layered waveguides, then device complexity is reduced, but vignetting and ghost images occur
Solution Approach 1:
The patent eliminates vignetting and ghost images by implementing asymmetric offset positioning of entry apertures. The first entry aperture is offset from the second entry aperture along the propagation direction of the waveguides. This asymmetric positioning ensures that optical modes from different waveguides do not overlap, preventing ghost image formation and vignetting effects while maintaining relatively simple device architecture.
3Area of stationary object
If images are expanded across a wide pupil range, then field of view is improved, but image quality deteriorates due to cross-coupling and vignetting
Solution Approach 1:
The patent maintains high image quality across wide pupil range by implementing asymmetric offset positioning of entry apertures. This positioning strategy prevents cross-coupling between adjacent waveguides, eliminating the primary source of image degradation. The offset configuration ensures that each waveguide's optical mode remains spatially distinct, preserving image quality while enabling wide eye box and pupil range coverage.
Solution Approach 2:
The patent preserves image quality during wide pupil range expansion by introducing a longitudinal offset dimension between entry apertures. This dimensional separation prevents mode overlap and cross-coupling effects that would otherwise degrade image quality. The offset positioning in the propagation direction creates sufficient spatial separation to maintain high-fidelity image transmission across the expanded pupil range.
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 effectively expands images to fill the user's pupil range, reducing vignetting and cross-coupling, and maintaining high image quality across a wider field of view in near-eye display systems.
Implementation Method 1
the first optical waveguide is configured to receive a first image through a first entry aperture, to expand the first image along the first optical waveguide
Implementation Method 2
To reduce cross-coupling of the first and second images, the second entry aperture is offset from the first entry aperture
Data Source
AI summary
A near-eye display system comprises first and second optical waveguides. The first optical waveguide is configured to receive a first image through a first entry aperture, to expand the first image along the first optical waveguide, and to release an expanded first image. Layered parallel to the first optical waveguide, the second optical waveguide is configured to receive a second image through a second entry aperture, to expand the second image along the second optical waveguide, and to release an expanded second image to overlap the expanded first image. The second entry aperture is offset from the first entry aperture along the second optical waveguide.