Diffractive Waveguide Combiner with Compensated-Wrap for Rainbow Mitigation
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Solution Overview
Problem
Typical diffractive near-eye display systems suffer from external light source diffraction, resulting in rainbow artifacts that distract from the user experience in augmented reality displays.
Innovation Solution
The implementation of a waveguide display system with a waveguide combiner and coupling gratings, where the waveguide combiner is oriented at a wrap angle relative to the waveguide plane, and the grating architecture is configured with increased grating vectors to minimize the range of angles and wavelengths of external light that can diffract into the user's eye.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a diffractive waveguide combiner is used to couple light into the waveguide, then light coupling efficiency is improved, but rainbow artifacts appear due to external light source diffraction
Solution Approach 1:
The waveguide combiner is wrapped at an asymmetric angle (e.g., 15 degrees) relative to the waveguide plane, breaking the symmetric diffraction pattern. This asymmetric wrapping configuration causes external light to diffract at angles that fall outside the user's field of view, while maintaining efficient coupling of projected light into the waveguide
Solution Approach 2:
The grating pitch and wrapping angle are optimized to specific parameter ranges. By adjusting these parameters, the diffraction angles for external light are controlled to fall outside the visible field of view, while the coupling efficiency for projected light remains high
2Object-generated harmful factors
If the waveguide combiner is wrapped at an angle to reduce rainbow artifacts, then visibility of rainbow artifacts is reduced, but the optical path and light coupling geometry become more complex
Solution Approach 1:
Instead of attempting to control diffraction in the traditional planar geometry, the solution introduces a wrapping angle dimension. This dimensional change allows the system to deflect diffracted light outside the field of view while maintaining a relatively simple waveguide structure
3Object-generated harmful factors
If the grating vector is increased to reduce the range of diffracted angles, then rainbow artifact mitigation is improved, but the grating pitch must be reduced which may affect manufacturing precision
Solution Approach 1:
The waveguide combiner integrates multiple functional elements: the wrapped waveguide structure, input coupling gratings, and output coupling gratings. This composite configuration allows the system to achieve rainbow artifact mitigation through the combination of wrapping geometry and optimized grating structures, balancing manufacturing feasibility with performance
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 reduces the occurrence and visibility of rainbow artifacts within a 30-degree field of view, enhancing the user experience by minimizing unwanted distractions from external light sources.
Implementation Method 1
an input coupling grating for coupling light from the light engine into the waveguide combiner
Implementation Method 2
a waveguide combiner configured to extend across a user's eye at a wrap angle θwrap(xy) relative to a waveguide plane
Implementation Method 3
an out-coupler grating having a pitch (Δx, Δy)... all angles of incidence θin of light from an external light source results in a diffracted angle θout
Data Source
AI summary
Embodiments herein are generally directed to a waveguide display assembly and a near-eye display system incorporating the waveguide display assembly. In an embodiment, the waveguide display includes a light engine, a waveguide combiner, an input coupling grating, and one or more coupling gratings exposed to an ambient environment of the waveguide display assembly. The waveguide combiner extends across a user's eye at a wrap angle θwrap(xy) relative to a waveguide plane, and the light engine is configured to project light toward the input coupling grating at a compensation angle θCl so as to increase the grating vector of the exposed gratings and reduce the angles and wavelengths at which light can be diffracted and coupled by the exposed grating into the waveguide combiner to the user's eye.