Multi-channel Waveguide Crosstalk Reduction via Offset Diffractive Optics
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Solution Overview
Problem
Conventional stacked waveguides for Head-Mounted Displays (HMDs) experience significant optical cross-talk between image-bearing channels, which degrades the quality of the output image due to the proximity and alignment of diffractive optics on planar surfaces.
Innovation Solution
The solution involves offsetting first and second in-coupling diffractive optics on parallel planar surfaces of the waveguide to prevent interaction between different subsets of image-bearing light beams, allowing them to propagate without crosstalk, with one optic operating in transmissive mode and the other in reflective mode to direct distinct subsets of image-bearing light beams along the waveguide.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple diffractive optics are stacked on a single waveguide to form multiple light channels, then the device can convey different image information (different angles or wavelengths), but optical cross-talk between channels increases due to proximity and alignment of the diffractive optics
Solution Approach 1:
The patent introduces a transverse offset dimension to separate diffractive optics that are stacked longitudinally on the waveguide. By positioning diffractive optics at different transverse locations, the system maintains multiple channels while preventing optical cross-talk through spatial separation in the transverse direction.
Solution Approach 2:
The patent segments the waveguide input region into multiple distinct zones, each containing a separate diffractive optic. This segmentation allows different light channels to be introduced at spatially separated locations, preventing interference between channels while maintaining the multi-channel capability.
2Volume of moving object
If diffractive optics are positioned close together on the waveguide surface to minimize device size, then the HMD can be more compact, but cross-talk between adjacent channels increases
Solution Approach 1:
The patent applies different transverse positioning strategies to different diffractive optics on the waveguide. Each diffractive optic is locally optimized for its specific channel while maintaining overall compactness. The offset arrangement allows close packing while preserving channel isolation through localized spatial separation.
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 reduces optical cross-talk between channels, enhancing the quality of the output image by ensuring that different subsets of image-bearing light beams do not interfere with each other, allowing for clearer and more accurate virtual image superposition over the real-world image.
Implementation Method 1
A first in-coupling diffractive optic on first planar surface directs a first subset of image-bearing light beams into the waveguide for propagation from the input region to the output region
Implementation Method 2
optical waveguide apparatus for conveying image-bearing light beams
Data Source
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AI summary
A waveguide apparatus for conveying a virtual image has first and second parallel planar surfaces. A first in-coupling diffractive optic on the first planar surface directs a first subset of image-bearing light beams into the waveguide and a second in-coupling diffractive optic on second planar surface directs a second subset of the image-bearing light beams into the waveguide. The first and second in-coupling diffractive optics are offset with respect to each other along the first and second parallel planar surfaces to independently direct the respective first and second subsets of the image-bearing light beams into the waveguide.