Optical Waveguide Facet Layout for Compact Near-Eye Displays
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Solution Overview
Problem
Existing optical systems for near-eye displays face challenges in minimizing the size of optical components while maintaining a given angular field of view, particularly in shallow-angle implementations, due to inefficient coupling-in configurations and unnecessary attenuation of image illumination.
Innovation Solution
The optical system employs a light-guide optical element (LOE) with optimized deployment of partially-reflecting surfaces, including a coupling-in prism and facets, where the second partially-reflecting surface in the medial plane avoids passing through intermediate facets, and the coupling-in prism is designed to reduce unnecessary reflections, thereby enhancing illumination efficiency and reducing component size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If traditional coupling-in configurations are used in shallow-angle implementations, then the optical system can be implemented, but the size of optical components increases and image illumination is unnecessarily attenuated
Solution Approach 1:
The waveguide is divided into multiple regions (first region with first orientation facets, second region with second orientation facets) to separately handle different aspects of light propagation. This segmentation allows optimized light paths in each region, reducing unnecessary reflections and component size while maintaining illumination efficiency
Solution Approach 2:
Instead of using traditional coupling-in configurations that cause unnecessary reflections, the patent inverts the approach by using a coupling-in prism that directly interfaces with the first region's facets. This inverted configuration eliminates intermediate reflections and reduces image illumination attenuation
2Adaptability or versatility
If traditional coupling-in configurations are used, then the optical system can function, but the field of view coverage becomes less efficient
Solution Approach 1:
The patent introduces a third dimension by adding the coupling-in prism as a separate optical element that interfaces with the waveguide. This dimensional addition simplifies the overall coupling-in configuration while improving field of view coverage through optimized light injection geometry
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 design achieves a more efficient use of image illumination, minimizing component size and reducing unwanted reflections, resulting in a more compact and effective near-eye display system.
Implementation Method 1
image illumination propagating within the LOE by internal reflection at the major external surfaces
Implementation Method 2
first set of planar, mutually-parallel, partially-reflecting surfaces... second set of planar, mutually-parallel, partially-reflecting surfaces
Data Source
AI summary
An optical system employs a waveguide including a first set of partially-reflecting surfaces (“facets”) for progressively redirecting image illumination propagating from a coupling-in region towards a second region, and a second set of facets in the second region for progressively coupling-out the redirected image illumination towards the eye of a viewer. The first set of facets includes at least a first facet close to the coupling-in region, a third facet fare from the coupling-in region, and a second facet located on a medial plane between the first and the third facets. The second facet is located in a subregion of the medial plane such that image illumination propagating from the coupling-in region to the third facet passes through the medial plane without passing through the second facet.