Waveguide structure with segmented diffractive optical elements and near-eye display apparatus employing the same
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Solution Overview
Problem
Current augmented reality systems face issues with image quality due to local defects in waveguide surfaces, leading to image blur and uneven brightness, and inefficiencies in light output, particularly when using continuous DOEs that require large waveguides and result in significant light loss.
Innovation Solution
A waveguide structure with segmented diffractive optical elements (DOEs) that include expanding and output-coupling segments, where the density and diffraction efficiency of these segments vary to optimize light distribution and reduce light loss, ensuring uniform brightness and a wider eye motion box.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If continuous DOEs are used to output light over a large area, then the field of view is improved, but light loss increases significantly
Solution Approach 1:
The waveguide surface is divided into multiple discrete DOE segments arranged in an array. Each segment emits light in a specific direction toward the eye motion box, rather than continuously in all directions. This segmentation allows precise control of light distribution, improving efficiency while maintaining wide field of view coverage.
Solution Approach 2:
Different regions of the waveguide surface are assigned different DOE segments with optimized local properties. Each segment's emission characteristics are tailored to direct light efficiently into the eye motion box from its specific location, ensuring uniform brightness and minimal light loss across the entire viewing area.
2Reliability
If the waveguide thickness is increased to improve image quality, then surface defect impact is reduced, but the system thickness increases
Solution Approach 1:
The use of discrete segmented DOEs creates well-separated exit pupils that are less sensitive to surface defects. The segmentation approach inherently reduces the impact of local surface irregularities on overall image quality, allowing thinner waveguides to achieve high image quality without requiring increased thickness.
3Measurement precision
If the density of exit pupils is increased to improve image quality, then the resolution is improved, but the waveguide area required increases
Solution Approach 1:
The DOE segments are arranged in a two-dimensional array on the waveguide surface, utilizing both horizontal and vertical dimensions to create multiple exit pupils. This dimensional approach allows high-density exit pupil distribution without requiring a proportional increase in waveguide area, as the segments efficiently pack into the available surface space.
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
The solution enhances image quality by reducing light loss and ensuring uniform brightness across the viewing area, allowing for a more compact and efficient near-eye display apparatus with a wider viewing angle.
Implementation Method 1
An optical waveguide usually includes three or more diffraction optical elements (DOEs) that perform different functions
Implementation Method 2
introduction of light into the waveguide propagation mode due to total inner reflection (TIR)
Data Source
AI summary
Provided is a waveguide guiding light to a target area, the waveguide including an input-coupling diffractive optical element (DOE) inputting the light into the waveguide, an expanding DOE expanding the light input into the waveguide through the input-coupling DOE, an output-coupling DOE outputting the light expanded in the waveguide by the expanding DOE to an outside of the waveguide, wherein the expanding DOE includes a plurality of expanding segments, and the output-coupling DOE includes a plurality of output-coupling segments.