Cascaded Pupil-Replicating Waveguides for Wearable Displays
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Solution Overview
Problem
Compact planar optical components in wearable displays, such as waveguides, face limitations in image quality, exit pupil size and uniformity, and field of view due to the challenge of maintaining high flatness and parallelism while avoiding output pupil gaps caused by lateral offsets during beam reflection.
Innovation Solution
A waveguide assembly comprising cascaded pupil-replicating waveguides, where the first waveguide expands the input beam to fill output pupil gaps of a thicker second waveguide, ensuring improved image quality by maintaining high flatness and parallelism without gaps, achieved through diffraction gratings and substrate surfaces that propagate and redirect the beam effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a thicker waveguide is used to improve stability and ease of manufacture, then manufacturing precision and structural stability are improved, but output pupil gaps appear due to lateral offsets during beam reflection
Solution Approach 1:
The patent divides the waveguide system into multiple thinner waveguides (first waveguide and second waveguide) instead of using a single thick waveguide. Each waveguide has a thickness less than half the beam width, which prevents lateral offsets and output pupil gaps. The multiple waveguides work together to achieve the desired optical function while maintaining pupil uniformity.
Solution Approach 2:
The patent implements a nested configuration where the first and second waveguides are positioned in close proximity, with the beam propagating through both sequentially. This nested arrangement allows the system to achieve the optical path length and stability of a thicker waveguide while avoiding the pupil gap problem through the segmented structure.
2Reliability
If a single thin waveguide is used to avoid output pupil gaps, then pupil uniformity is maintained, but the waveguide becomes more difficult to manufacture with required flatness and parallelism
Solution Approach 1:
Instead of manufacturing one extremely thin waveguide with high precision requirements, the patent segments the optical path into multiple slightly thicker waveguides. Each individual waveguide is easier to manufacture with standard precision tolerances, while the collective system maintains the required optical performance and avoids pupil gaps.
3Weight of moving object
If compact planar optical components are used to reduce size and weight, then weight of the optics block is reduced, but image quality and field of view are limited
Solution Approach 1:
The patent uses multiple thin planar waveguides instead of a single thick waveguide or bulky optical components. This segmentation maintains the compact and lightweight advantage of planar optics while improving image quality by eliminating output pupil gaps and maintaining uniform beam propagation through the segmented structure.
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 solution enhances image quality by eliminating output pupil gaps, allowing for a thicker, more stable second waveguide that is easier to manufacture to the required flatness and parallelism, thereby improving the overall performance and comfort of wearable displays.
Implementation Method 1
A first diffraction grating supported by the first substrate in a first optical path of the first input beam is configured for diffracting the first input beam impinging on the first diffraction grating for providing the multiple offset portions of the first input beam
Implementation Method 2
A first substrate comprising first and second surfaces for propagating the first input beam in the first substrate by reflecting the first input beam from the first and second surfaces of the first substrate
Data Source
AI summary
A waveguide assembly is provided. The waveguide assembly includes a pair of pupil-replicating waveguides. The first pupil-replicating waveguide is configured for receiving an input beam of image light and providing an intermediate beam comprising multiple offset portions of the input beam. The second pupil-replicating waveguide is configured for receiving the intermediate beam from the first pupil-replicating waveguide and providing an output beam comprising multiple offset portions of the intermediate beam. The input beam may be expanded by the waveguide assembly in such a manner that pupil gaps are reduced or eliminated.