Layered Diffraction Waveguide for Uniform Near-Eye Light Coupling
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Solution Overview
Problem
Existing optical waveguides face limitations in modulating the uniformity of light coupling-out due to the degree of freedom of the grating, leading to reduced grating efficiency and uniformity.
Innovation Solution
A diffraction optical waveguide with a layered waveguide substrate having variable refractive indices and catadioptric interfaces, combined with a partitioned coupling-out grating, to regulate light energy distribution and improve coupling-out efficiency and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If partition gratings are used to modulate the uniformity of waveguide coupling-out, then the uniformity is improved, but the grating efficiency is reduced
Solution Approach 1:
The waveguide is divided into multiple layers with different refractive indexes, and the coupling-out grating is segmented into multiple zones with different diffraction efficiencies. This segmentation allows independent optimization of uniformity and efficiency in different regions, resolving the contradiction between overall uniformity and local grating efficiency.
Solution Approach 2:
Different zones of the coupling-out grating are assigned different local properties (diffraction efficiencies) to achieve optimal performance. The first zone has higher diffraction efficiency while the second zone has lower diffraction efficiency, creating local quality variations that balance overall uniformity with efficient light extraction.
2Device complexity
If the degree of freedom of the grating is limited, then the grating structure is simple, but the modulation capability for uniformity is limited
Solution Approach 1:
The design transitions from a single-layer grating to a multi-layer waveguide structure with multiple grating zones, adding dimensional complexity that enables enhanced modulation capability. The multiple layers and zones provide additional degrees of freedom for controlling light propagation and achieving uniform coupling-out.
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
Enhances light coupling-out efficiency and uniformity by allowing greater freedom in regulating waveguide properties, resulting in improved luminance and uniformity of the coupled-out light.
Implementation Method 1
a coupling-in grating disposed in the coupling-in zone of the waveguide substrate and configured to couple image light into the waveguide substrate through diffraction
Implementation Method 2
a coupling-out grating disposed in the coupling-out zone of the waveguide substrate and configured to couple at least a part of diffracted light propagating thereinto out of the waveguide substrate through diffraction
Implementation Method 3
a catadioptric interface is formed between adjacent waveguide media, the diffracted light coupled-in from the coupling-in zone passes through the M layers of waveguide media in sequence and is split by the catadioptric interface
Implementation Method 4
beams after light splitting propagate towards the coupling-out zone along different transmission paths in the M layers of waveguide media
Data Source
AI summary
The disclosure provides a diffraction optical waveguide, a design method thereof and a near-eye display device. The diffraction optical waveguide includes: a waveguide substrate; a coupling-in grating configured to couple image light into the waveguide substrate through diffraction; and a coupling-out grating configured to couple at least a part of diffracted light propagating thereinto out of the waveguide substrate through diffraction, wherein the waveguide substrate includes M layers of waveguide media, a catadioptric interface is formed between adjacent waveguide media, the diffracted light passes through the M layers of waveguide media in sequence and is split by the catadioptric interface, beams after light splitting propagate towards a coupling-out zone along different transmission paths in the M layers of waveguide media, each layer of waveguide medium has a different refractive index, a refractive index of an ith layer of waveguide medium being ni, an air refractive index being n0, and |ni−ni−1|≥0.05.