Diffractive Optical Waveguide Light-Return Grating Efficiency
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Solution Overview
Problem
Current diffractive optical waveguides for augmented reality displays suffer from low optical coupling efficiency and non-uniform optical energy distribution, resulting in inadequate brightness and display quality.
Innovation Solution
The implementation of a coupling-in end light-return grating and optimized grating arrangements within the waveguide substrate to enhance optical coupling efficiency and uniformity of the optical output field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a coupling-in grating, coupling-out grating, and light-return grating are arranged on a waveguide substrate, then the optical coupling efficiency is improved, but the overall optical coupling efficiency remains very limited and the optical output field becomes non-uniform with dark central area and bright surrounding area
Solution Approach 1:
The waveguide substrate is divided into multiple functional regions: a coupling-in region with a coupling-in grating, a coupling-out region with a coupling-out grating, and a light-return region with a light-return grating. Each region performs a specific function in the optical path, allowing independent optimization of light coupling and distribution characteristics.
Solution Approach 2:
Different grating structures are designed for different regions: the coupling-in grating has a first grating vector optimized for light input, the coupling-out grating has a second grating vector optimized for light output, and the light-return grating has a third grating vector optimized for returning stray light. This local optimization ensures both high coupling efficiency and uniform optical output distribution.
2Loss of energy
If the light-return grating is arranged around the end of the coupling-out grating away from the coupling-in grating, then light returning to the coupling-out grating is improved, but the optical energy distribution becomes non-uniform with poor display effect
Solution Approach 1:
The light-return grating acts as a feedback mechanism that captures light which has propagated through the waveguide substrate and returns it to the coupling-out grating. This feedback loop ensures that optical energy is充分利用 and contributes to improving both coupling efficiency and output uniformity.
Solution Approach 2:
The grating vectors are configured in different directional dimensions: the first grating vector, second grating vector, and third grating vector are arranged at different angles and orientations. This multi-dimensional grating arrangement enables effective light manipulation in multiple directions, achieving both high efficiency and uniformity.
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
Improves the brightness and uniformity of the optical output field, enhancing the display quality of augmented reality devices.
Implementation Method 1
a coupling-in grating a, arranged on a waveguide substrate, is configured to couple an incident beam irradiated on the coupling-in grating into the waveguide substrate
Implementation Method 2
a coupling-out grating b, arranged on the waveguide substrate, is configured to expand the light carrying the image information in a plane where the waveguide substrate is located and to couple the light out of the waveguide substrate
Implementation Method 3
a light-return grating c, arranged around an end of the coupling-out grating b away from the coupling-in grating a, is configured to return the light that has left the coupling-out grating b and that continues to propagate in the waveguide substrate to the coupling-out grating b
Data Source
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AI summary
A diffractive optical waveguide (10) is provided, which comprises a waveguide substrate (10a) and a coupling-in grating (11), a coupling-out grating (13), and a coupling-in end light-return grating (12) formed on the waveguide substrate (10a), the coupling-in grating (11) couples an input beam into the waveguide substrate (10a) and forms a first beam of light propagating toward the coupling-out grating (13) and a second beam of light not propagating toward the coupling-out grating (13), the coupling-out grating (13) couples at least a part of the light propagating therein out of the waveguide substrate (10a), and the coupling-in end light-return grating (12) diffracts the second beam of light so that it propagates toward the coupling-out grating (13). A display device (200) having the above diffractive optical waveguide (211) is also disclosed. By providing the coupling-in end light-return grating (12), optical coupling efficiency of the diffractive optical waveguide (10) is improved, and the energy distribution uniformity of an output field of the diffractive optical waveguide (10) is improved.