Diffractive Optical Waveguide Relay Grating for AR Eye Box Uniformity
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Solution Overview
Problem
Diffractive optical waveguides in augmented reality and mixed reality applications face challenges in achieving uniform display effects and enlarging the eye box due to issues like central bright stripes, field of view loss, and high diffraction energy loss, particularly with two-dimensional grating designs.
Innovation Solution
A diffractive optical waveguide design featuring a coupling-in region, a relay region with a two-dimensional grating, and a coupling-out region, where the relay grating changes the transmission path to ensure complete coverage of the coupling-out region, using symmetrical or asymmetrical shapes and grating configurations to enhance energy utilization and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a two-dimensional grating is used for pupil expansion, then the eye box is enlarged, but central bright stripes appear and field of view uniformity deteriorates
Solution Approach 1:
The patent divides the waveguide into multiple functional regions: a coupling-in region with a first grating, a relay region with a second grating, and a coupling-out region with a third grating. This segmentation allows each region to perform its specific function optimally, preventing the central bright stripe issue while maintaining large eye box.
Solution Approach 2:
The relay region acts as an intermediary between the coupling-in region and the coupling-out region. The second grating in the relay region redirects light paths to ensure uniform illumination across the coupling-out region, eliminating the central bright stripe problem while maintaining the enlarged eye box provided by the two-dimensional grating structure.
2Area of stationary object
If a two-dimensional grating is used for pupil expansion, then the coupling-out region is enlarged, but diffraction energy loss increases
Solution Approach 1:
Different gratings are designed with different local characteristics optimized for their specific functions. The first grating is optimized for coupling light into the waveguide, the second grating for redirecting light in the relay region, and the third grating for coupling light out. This local optimization minimizes diffraction energy loss at each stage while maintaining the enlarged coupling-out region.
3Manufacturing precision
If the relay region is made asymmetrical to improve light distribution, then manufacturing complexity increases
Solution Approach 1:
The patent allows the relay region to be either symmetrical or asymmetrical depending on the specific application requirements. When asymmetrical design is needed to improve light distribution uniformity, the manufacturing process can accommodate this variation. The grating structures can be fabricated using standard photolithography and etching processes, making the asymmetrical design feasible without excessive manufacturing complexity.
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 design eliminates field of view losses, improves energy utilization, and enhances the uniformity of image display across the eye box, reducing ineffective regions and manufacturing costs while maintaining viewing brightness and comfort.
Implementation Method 1
a coupling-in grating, arranged in the coupling-in region, the coupling-in grating is configured to couple lights into the optical waveguide substrate and transmit the lights to the relay region and the coupling-out region
Implementation Method 2
a relay grating, arranged in the relay region, the relay grating is configured to change a transmission path of the lights so that the lights cover the coupling-out region
Implementation Method 3
a coupling-out grating, arranged in the coupling-out region, the coupling-out grating is configured to couple lights out from the coupling-out region
Data Source
AI summary
A diffractive optical waveguide includes: an optical waveguide substrate, at least one coupling-in grating, at least one relay grating, and at least one coupling-out grating. The coupling-in grating is arranged in the coupling-in region. The relay grating is arranged in the relay region. The coupling-out grating is arranged in the coupling-out region. The relay grating and the coupling-out grating are both two-dimensional gratings. The coupling-in region and the coupling-out region are both symmetrical in shape, the relay grating is symmetrical or asymmetrical in shape. Thus, the relay grating can change a transmission path of part of lights, the lights coupled-in from the coupling-in grating can be transmitted to the coupling-out region through the relay grating and cover the entire coupling-out region, avoiding the problem of dark angle of fields of view in the coupling-out region and improving energy utilization efficiency of the lights.