AR Waveguide Relief Grating Refractive Index Design
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Solution Overview
Problem
Optical waveguide devices for augmented reality displays face issues with brightness and uniformity due to high reflection losses at the grating-waveguide substrate interface, exacerbated by the trend towards thinner and lighter designs.
Innovation Solution
The optical waveguide device is designed with specific refractive index configurations for the relief grating and waveguide substrate to minimize the number of reflections, using a composite synergistic layer for constructive interference, and an antireflection coating to enhance coupling efficiency and reduce reflection losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the waveguide substrate is made thinner and lighter, then the device becomes more portable and compact, but the number of reflections increases leading to higher reflection losses and reduced brightness
Solution Approach 1:
The patent changes the refractive index parameter of the waveguide substrate by introducing a composite synergistic layer with specific refractive index characteristics. This layer modifies the optical parameters of the system to reduce reflection losses while maintaining the thin substrate design, thereby resolving the contradiction between device轻薄化 and display brightness
Solution Approach 2:
The patent employs a composite synergistic layer composed of multiple materials with different refractive indices. This composite structure optimizes the optical coupling between the relief grating and the waveguide substrate, reducing reflection losses and improving light transmission efficiency, thus maintaining brightness in thin-waveguide designs
2Weight of moving object
If the waveguide substrate is made thinner and lighter, then the device becomes more portable and compact, but the uniformity of light distribution deteriorates due to increased reflection losses
Solution Approach 1:
By adjusting the refractive index parameters through the composite synergistic layer, the patent optimizes the optical path and reduces variation in reflection losses across different light paths. This ensures uniform light distribution while maintaining the thin substrate structure
Solution Approach 2:
The composite synergistic layer acts as an intermediary between the relief grating and the waveguide substrate, mediating the optical coupling process. It ensures uniform energy transfer and reduces path-dependent reflection variations, thereby improving light distribution uniformity in thin-waveguide devices
3Ease of manufacture
If conventional refractive index configurations are used, then the manufacturing process is simpler, but the coupling-in efficiency is reduced due to high reflection losses
Solution Approach 1:
The patent uses a composite synergistic layer that can be integrated into existing manufacturing processes while significantly improving coupling-in efficiency. The composite structure allows for standard fabrication techniques to be used, maintaining manufacturing simplicity while achieving superior optical performance
Solution Approach 2:
The composite synergistic layer is applied locally at the critical interface between the relief grating and the waveguide substrate. This localized optimization improves coupling-in efficiency at the most critical point without requiring complex manufacturing changes across the entire device
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 significantly improves the coupling-in comprehensive efficiency, leading to enhanced brightness and uniformity in the display, while maintaining a thin and lightweight design.
Implementation Method 1
the first relief grating has a first refractive index n1, the first waveguide substrate has a second refractive index n2, and n2>n1, so as to reduce a number of reflections, which light diffracted at a predetermined order is subjected to before leaving a region where the first relief grating lies
Implementation Method 2
the input grating couples incident light carrying image information into the waveguide substrate. The output grating makes the light carrying image information to propagate and expand, and at the same time couples the light out of the waveguide substrate
Implementation Method 3
the first subregion and the second subregion have the same thickness and have a fifth refractive index n5 and a sixth refractive index n6, respectively, such that diffracted light of the predetermined order is subjected to constructive thin-film interference in the first subregion as it passes through the composite synergistic layer
Implementation Method 4
an antireflection coating is formed on a border between the first waveguide substrate and the second waveguide substrate for enhancing transmittance of light from the first waveguide substrate to the second waveguide substrate
Data Source
AI summary
An optical waveguide device is disclosed, in which an input section comprises a first waveguide substrate and a first relief grating formed on a surface thereof, and refractive indices n1, n2 of the first relief grating and the first waveguide substrate satisfy n2<n1, such that a first maximum average number of reflections that a light beam within a predetermined FOV range is subjected to on the surface after diffraction of the predetermined order before leaving a region where the first relief grating lies, is N, and N≤2, wherein when N≤1, N≤M−0.25; when 1<N≤1.5, N≤M−0.5; and when 1.5<N≤2, N≤M−0.75, wherein M is a second maximum average number of reflections assuming the first waveguide substrate has the same refractive index as the first relief grating.