Near-Eye Display FOV Expansion via Optically Stitched Waveguide
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Solution Overview
Problem
Conventional near-eye display systems using single in-coupling and intermediate diffractive optical elements (DOEs) provide a relatively narrow field of view (FOV) due to light leakage outside the total internal reflection (TIR) limits of the waveguide, limiting the extent of the FOV that can be effectively utilized.
Innovation Solution
The implementation of multiple DOEs in a waveguide, where light is in-coupled by left and right DOEs and propagated through intermediate DOEs to expand the pupil in two directions, allowing each FOV portion to stay within the TIR limits, and then diffracted to a single out-coupling DOE to stitch the full FOV together, enhancing the FOV beyond conventional limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single in-coupling DOE and a single intermediate DOE are used, then the system structure is simple, but the field of view (FOV) is narrow due to light leakage outside the total internal reflection (TIR) limits
Solution Approach 1:
The patent divides the single intermediate DOE into multiple intermediate DOEs (first intermediate DOE and second intermediate DOE) positioned at different locations along the waveguide. Each DOE handles a specific portion of the field of view, allowing the system to extend the FOV beyond the TIR limits while maintaining manageable structural complexity through modular segmentation.
Solution Approach 2:
The patent introduces a longitudinal dimension by positioning multiple intermediate DOEs at different locations along the waveguide length, rather than using a single DOE. This dimensional extension allows light to propagate through multiple TIR cycles, effectively increasing the field of view without proportionally increasing lateral complexity.
2Area of stationary object
If the field of view is extended beyond TIR limits, then the FOV increases, but light leakage occurs outside the waveguide
Solution Approach 1:
The patent applies preliminary action by using the first intermediate DOE to expand the pupil and steer light at an angle that pre-positions it for successful TIR propagation. This preliminary angular adjustment ensures that subsequent light propagation remains within the TIR acceptance cone, preventing leakage while achieving extended FOV.
Solution Approach 2:
The patent changes the propagation angle parameter by using the first intermediate DOE to redirect light at a specific angle that optimizes TIR conditions. This parameter adjustment allows the system to operate at steeper angles than conventional single-DOE systems while maintaining confinement within the waveguide, thereby extending FOV without significant light loss.
3Area of stationary object
If multiple intermediate DOEs are used to expand pupil in one direction, then the FOV is extended, but the system complexity increases
Solution Approach 1:
The patent merges the functionality of multiple intermediate DOEs by having them work cooperatively in sequence. The first intermediate DOE expands the pupil and steers light, while the second intermediate DOE further expands the FOV. By combining these functions in a coordinated sequence rather than using independent parallel systems, the patent reduces overall system complexity while achieving extended FOV.
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 significantly extends the FOV to 90 degrees or more without increasing system cost, enabling a wider, optically stitched field of view for users while maintaining the compactness and efficiency of the near-eye display system.
Implementation Method 1
light can leak out of the waveguide at propagation angles that are outside the total internal reflection (TIR) limits of the waveguide
Implementation Method 2
Light propagating in the left and right intermediate DOEs is diffracted (e.g., downwards) to a single out-coupling DOE
Data Source
AI summary
An extended field of view (FOV) is provided by an exit pupil expander in a near-eye display system that uses a waveguide with multiple diffractive optical elements (DOEs) for in-coupling light, expanding the pupil in two directions, and out-coupling light to a system user's eye. Left and right in-coupling DOEs in-couple pupils respectively produced by a pair of imagers—one imager provides a left portion of the FOV and the other imager provides the right portion. The left portion and right portion of the FOV respectively propagate in a left and right intermediate DOEs which expand the pupil in a first direction and diffract light to an out-coupling DOE. The out-coupling DOE expands the pupil in a second direction, stitches the extended FOV together by combining the left and right portions of the FOV produced by the imagers, and out-couples the extended FOV to the user's eye.