Hybrid Waveguide Combining Reflective and Diffractive Structures
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Solution Overview
Problem
Existing near-eye display (NED) systems for augmented reality (AR) face challenges in achieving a wide field of view and efficient pupil expansion with existing optical waveguides, as geometrical waveguides are limited in two-dimensional expansion and diffractive waveguides require tight assembly tolerances and compromise optical resolution.
Innovation Solution
A multi-chromatic waveguide combining reflective (geometric) optical structures with periodic diffractive grating structures, using reflective mirrors/facets for incoupling and outcoupling, and expansion gratings for pupil expansion, which compensates for grating dispersion and allows for a wide field of view (at least 90 degrees) with improved efficiency (at least 10×) using a single waveguide that works with all colors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If diffractive waveguides are used for pupil expansion, then field of view can be expanded, but assembly tolerances become tight and optical resolution is compromised
Solution Approach 1:
The patent combines reflective (geometric) optical structures with periodic diffractive grating structures in a hybrid waveguide system. The reflective structures handle incoupling and outcoupling of light, while the diffractive gratings perform pupil expansion. This merging allows the system to achieve wide field of view through the diffractive component while the reflective component maintains relaxed assembly tolerances and preserves optical resolution, thus resolving the contradiction between field of view expansion and manufacturing precision requirements
Solution Approach 2:
The hybrid waveguide structure performs multiple functions within a single integrated system: the reflective mirrors/facets handle light incoupling and outcoupling, while the expansion gratings perform pupil expansion. This multi-functional design allows the system to achieve both wide field of view and high optical resolution without requiring separate waveguides for different color components, thereby improving assembly tolerances while maintaining field of view expansion
2Manufacturing precision
If geometrical waveguides are used, then assembly tolerances are relaxed, but two-dimensional pupil expansion is limited
Solution Approach 1:
The patent merges geometrical reflective structures with diffractive grating structures to create a hybrid waveguide that achieves both relaxed assembly tolerances and two-dimensional pupil expansion. The reflective structures provide the relaxed tolerance benefits of geometrical waveguides, while the integrated diffractive gratings enable comprehensive two-dimensional pupil expansion that pure geometrical waveguides cannot achieve
3Measurement precision
If separate waveguides are used for each color component, then optical resolution can be maintained, but device complexity and size increase
Solution Approach 1:
The hybrid waveguide structure serves as a universal optical component that handles all color components (multi-chromatic light) simultaneously through a single integrated structure. The combination of reflective and diffractive elements works across the visible spectrum, maintaining optical resolution for all colors without requiring separate waveguides for each color component, thereby significantly reducing device complexity
4Area of stationary object
If diffractive waveguides are used, then field of view can be expanded, but efficiency decreases requiring multiple waveguides
Solution Approach 1:
The patent merges the advantages of reflective and diffractive waveguide structures into a hybrid system where reflective structures efficiently couple light in and out, while diffractive gratings expand the pupil in two dimensions. This combination achieves both wide field of view and high optical efficiency within a single waveguide, eliminating the need for multiple waveguides and improving overall system productivity
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 solution enables a wide field of view and substantial efficiency improvement while maintaining optical resolution, with reduced assembly tolerances and eliminating the need for separate waveguides for each color component, resulting in a more compact and effective NED system.
Implementation Method 1
a diffraction grating in the substrate... configured to convey at least a portion of the light from the optical input port to the optical output port while changing a propagation direction of the conveyed portion of the light
Implementation Method 2
The optical input port includes a reflector to receive multi-chromatic light from outside the waveguide and to change a propagation direction of the light
Implementation Method 3
The optical output port also includes a second reflector to output at least a portion of the light from the waveguide
Data Source
AI summary
A multi-chromatic optical waveguide for a near-eye display (NED) device includes reflective/refractive structures and periodic grating structures. Image incoupling and outcoupling can be done by reflective mirrors/facets, and image expansion can done by one or more even order expansion gratings. Wider field of view can be by achieved by splitting the field-of-view into multiple portions that propagate in different directions within the waveguide and then recombining those portions in the outcoupling region of the waveguide.