Optical Waveguide Structure With Rotated 2D Out-Coupling Grating
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Solution Overview
Problem
Existing optical waveguides in augmented reality display devices face challenges in optimizing the morphology of gratings to improve efficiency, leading to inefficient light coupling and premature light loss.
Innovation Solution
The implementation of a two-dimensional grating with a relative rotation angle between the characteristic axis direction of the two-dimensional structural elements and the lattice period vector sum of the grating, optimizing the grating morphology to enhance diffraction efficiency and light propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If traditional grating structures are used in optical waveguides, then the device complexity is low, but the light coupling efficiency is poor and energy loss is high
Solution Approach 1:
The patent transitions from traditional one-dimensional grating structures to two-dimensional grating structures with unit cells arranged in both x and y directions. This dimensional upgrade enables control of light coupling in multiple directions simultaneously, improving energy utilization while managing structural complexity through systematic periodic arrangements.
Solution Approach 2:
The patent optimizes multiple parameters of the two-dimensional grating including unit cell geometry (rectangular, circular, triangular configurations), lattice period dimensions (dx, dy), and refractive index contrasts. By systematically adjusting these parameters, the design achieves high diffraction efficiency and reduced energy loss without excessive complexity.
2Reliability
If grating morphology is not optimized, then the manufacturing process is simple, but the diffraction efficiency is low and light propagation is inefficient
Solution Approach 1:
The complex two-dimensional grating structure is divided into repeating unit cells with standardized geometries (rectangular, circular, or triangular). Each unit cell serves as a modular building block that can be manufactured using standard lithography processes, then replicated across the waveguide surface to achieve high diffraction efficiency without requiring complex fabrication steps.
3Stability of the object's composition
If the out-coupling grating uses a two-dimensional structure with relative rotation angle, then the display uniformity improves, but the design complexity increases
Solution Approach 1:
The patent introduces a relative rotation angle θ between the characteristic axis of the two-dimensional unit cell and the lattice period vector sum direction. This asymmetric orientation optimizes the diffraction efficiency distribution across different viewing angles, achieving uniform display characteristics. The asymmetry is systematically managed through defined geometric relationships rather than arbitrary design choices.
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 approach improves the efficiency of optical waveguides by enhancing light coupling and reducing premature light loss, resulting in improved display uniformity and energy utilization.
Implementation Method 1
when the light propagates in the waveguides, it is guaranteed that the optical energy is not lost through total reflection
Implementation Method 2
an out-coupling grating configured to perform pupil expansion and out-coupling on light transmitted in the waveguide substrate
Data Source
AI summary
The application discloses an optical waveguide structure, an optical waveguide module and a head-mounted display device. The optical waveguide structure according to an implementation of the disclosure includes a waveguide substrate, an in-coupling grating and an out-coupling grating. The in-coupling grating is used to couple input light into the waveguide substrate for transmission. The out-coupling grating is used to perform pupil expansion and out-coupling on light transmitted in the waveguide substrate. The out-coupling grating is a two-dimensional grating, and the two-dimensional grating has a two-dimensional structural element(s). A characteristic axis direction of the two-dimensional structural element(s) forms a relative rotation angle with a direction of a lattice period vector sum of the two-dimensional grating to change a diffraction efficiency of the out-coupling grating in a predetermined direction.