Light-Guide Optical Elements for Two-Dimensional Aperture Expansion
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Solution Overview
Problem
Existing near-eye display systems face challenges in efficiently expanding the optical aperture to provide a wide field of view while maintaining image quality and reducing device dimensions.
Innovation Solution
The optical system includes a light-guide optical element with a first region containing a first set of planar, partially-reflecting surfaces and a second set of planar, partially-reflecting surfaces oriented non-parallel to the first, and a second region with a third set of partially-reflecting surfaces oblique to the major external surfaces, to direct image illumination for viewing by an eye-motion box.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a single set of partially-reflecting surfaces is used in the light-guide optical element, then the device structure is simpler, but the field of view is limited and aperture expansion is insufficient
Solution Approach 1:
The light-guide optical element is divided into multiple regions (first region with first and second sets of partially-reflecting surfaces, and second region with third set of partially-reflecting surfaces). Each set of surfaces is oriented at different angles to deflect light into different directions, collectively providing a wide combined field of view while maintaining manageable structural complexity through modular regional design.
Solution Approach 2:
The patent employs multiple sets of partially-reflecting surfaces with different orientations (first orientation, second orientation non-parallel to first, third orientation non-parallel to both) to expand the optical aperture in multiple dimensional directions simultaneously, achieving wide field of view coverage by utilizing angular and spatial dimensionality.
2Area of stationary object
If multiple sets of partially-reflecting surfaces with different orientations are used, then the aperture is expanded and field of view is widened, but the device dimensions increase
Solution Approach 1:
Multiple sets of partially-reflecting surfaces are nested within the light-guide optical element structure, with each set positioned in specific regions. The first and second sets are in the first region, while the third set is in the second region, allowing compact integration of multiple optical functions within a constrained device volume without excessive dimensional growth.
Solution Approach 2:
Instead of expanding device length linearly to accommodate multiple reflection surfaces, the patent utilizes angular orientation differences and three-dimensional spatial arrangement of surfaces at different orientations, achieving aperture expansion through angular dimensionality rather than linear dimensional growth.
3Ease of operation
If the third set of partially-reflecting surfaces is positioned at an oblique angle to the major external surfaces, then image illumination is effectively coupled out towards the eye-motion box, but manufacturing precision requirements increase
Solution Approach 1:
The third set of partially-reflecting surfaces is specifically positioned at an oblique angle to the major external surfaces in the second region of the light-guide optical element, creating a localized optical coupling interface optimized for directing image illumination toward the eye-motion box while maintaining standard manufacturing tolerances for the remaining planar surfaces.
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 system achieves a continuous combined field of view larger than each part, providing a wide field of view with improved image uniformity and reduced device dimensions by using two sets of partially-reflecting surfaces to expand the aperture.
Implementation Method 1
a first set of planar, mutually-parallel, partially-reflecting surfaces having a first orientation; (b) the first region further containing a second set of planar, mutually-parallel, partially-reflecting surfaces having a second orientation
Implementation Method 2
image illumination propagating within the LOE by internal reflection at the major external surfaces
Data Source
AI summary
An optical system provides two-stage expansion of an input optical aperture for a display based on a light-guide optical element. A first expansion is achieved using two distinct sets of mutually-parallel partially-reflecting surfaces, each set handing a different part of an overall field-of-view presented to the eye. In some cases, a single image projector provides image illumination to two sets of facets that are integrated into the LOE. In other cases, two separate projectors deliver image illumination corresponding to two different parts of the field-of-view to their respective sets of facets.