Edge-Apodized Waveguide Gratings for Reduced Edge Diffraction
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Solution Overview
Problem
Optical waveguides in augmented and virtual reality systems suffer from signal distortions and MTF degradation due to edge effects such as scattering, diffraction, and reflections at grating edges, leading to reduced image clarity and fidelity.
Innovation Solution
Implementing grating apodization by varying the diffraction grating fill factor and thickness to create smooth transitions at the edges of optical elements, thereby reducing diffraction efficiency and mitigating phase and amplitude discontinuities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If light propagates through the waveguide at the edges of optical gratings, then coupling and phase modulation functions are achieved, but edge effects such as scattering, diffraction, and reflections cause signal distortion and MTF degradation
Solution Approach 1:
The patent applies local quality by varying the grating fill factor specifically at the edge regions compared to the center regions. The edge gratings have a first fill factor while center gratings have a second fill factor, creating localized property changes that reduce edge effects without compromising the overall grating function for light coupling and phase modulation
Solution Approach 2:
The patent changes the fill factor parameter across the grating structure to optimize performance. By transitioning from a uniform fill factor to a variable fill factor distribution (with edge regions having different fill factors than center regions), the patent reduces edge diffraction and scattering while maintaining effective light coupling and phase modulation
2Manufacturing precision
If uniform grating structures are used in waveguides, then manufacturing is simplified, but accumulated phase and amplitude changes cause MTF degradation and image quality loss
Solution Approach 1:
The patent implements local quality by creating non-uniform grating structures where edge gratings have different fill factors than center gratings. This localized variation in grating properties compensates for edge effects and maintains MTF performance while remaining compatible with standard manufacturing processes
Solution Approach 2:
The patent modifies the fill factor parameter across different regions of the grating structure. By implementing a gradient or stepped fill factor distribution rather than a uniform value, the patent eliminates MTF degradation caused by accumulated phase and amplitude changes while maintaining manufacturing feasibility
3Use of energy by moving object
If grating fill factor is increased to improve diffraction efficiency, then light coupling is enhanced, but edge diffraction and scattering increase causing signal distortion
Solution Approach 1:
The patent applies local quality by assigning different fill factors to edge gratings versus center gratings. The center gratings can have higher fill factors for maximum diffraction efficiency, while edge gratings have optimized fill factors that reduce edge diffraction and scattering, thus locally optimizing different regions for their specific functions
Solution Approach 2:
The patent changes the fill factor parameter across the grating array to balance diffraction efficiency and edge effect reduction. By implementing a variable fill factor distribution, the patent achieves optimal light coupling in center regions while minimizing harmful edge diffraction through reduced or optimized fill factors at edge positions
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 the Modulation Transfer Function (MTF) of waveguides, improving image sharpness and clarity by minimizing signal distortions and aberrations.
Implementation Method 1
Optical gratings are periodic structures used in waveguides to couple light in or out and introduce phase and amplitude changes to light that propagates through the waveguide
Implementation Method 2
light that propagates through the waveguide
Data Source
AI summary
A diffraction grating includes a plurality of diffraction features and a plurality of grooves. Each groove of the plurality of grooves is adjacent to at least one diffraction feature of the plurality of diffraction features. One or more apodization features include apodization by a varied ratio of the filled region of one or more diffractive gratings to the total period, typically known as the grating fill factor to a gradually alter one or more edges of the plurality if diffraction features of at least one optical element of a waveguide. The one or more apodization features reduce a diffraction efficiency of at least one diffraction order of the diffraction grating.