Spatial Variance in Waveguide Incoupler Grating Features
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Solution Overview
Problem
Conventional wearable head-mounted displays (HMDs) face inefficiencies in light coupling due to uniform grating features across the incoupler, leading to non-uniformity in image color and intensity across the field of view, as different wavelengths and angles of light encounter the same grating features, resulting in varied incoupling efficiency.
Innovation Solution
Introducing spatial variance in grating features along the incoupler, such as varying feature height, spacing, angles, and density, to achieve uniform incoupling efficiency across the incoupler, allowing for tailored efficiency depending on design considerations and reducing inconsistencies in image projection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If uniform grating features are used across the incoupler, then manufacturing is simplified, but image uniformity deteriorates due to non-uniform incoupling efficiency across different wavelengths and angles
Solution Approach 1:
The patent applies local quality by varying the grating features (such as groove depth, spacing, or orientation) at different locations across the incoupler surface. This allows each region of the incoupler to be optimized for specific wavelengths or angles of light incident on that region, thereby achieving uniform incoupling efficiency across the entire field of view while maintaining manufacturing feasibility through systematic variation patterns
2Manufacturing precision
If grating features are varied to optimize incoupling efficiency for different wavelengths and angles, then image uniformity improves, but device complexity increases
Solution Approach 1:
The patent segments the incoupler surface into multiple zones or regions, each with optimized grating features for specific wavelength ranges or angle ranges. This segmentation approach allows systematic optimization of different regions while maintaining overall device manageability and manufacturability through modular design principles
Solution Approach 2:
The patent utilizes parameter changes by systematically varying grating features (such as groove depth, spacing, orientation, or fill factor) across different locations of the incoupler. These controlled parameter variations enable optimization of incoupling efficiency for different wavelengths and angles without requiring fundamentally different device architectures
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 enhances the uniformity of image quality by optimizing light coupling efficiency across the incoupler, ensuring consistent brightness and color across the field of view, thereby improving the overall performance of HMDs.
Implementation Method 1
light from an image source is coupled into a light guide substrate, generally referred to as a waveguide, by an input optical coupling such as an in-coupling grating
Implementation Method 2
the light beams are 'guided' through the substrate, typically by multiple instances of total internal reflection (TIR)
Data Source
AI summary
A head-mounted display (HMD) system including a lens element supported by a support structure, the lens element having a waveguide with an incoupler configured to receive light from an optical scanner of the HMD. The incoupler is configured with multiple features varying in at least one of height, spacing, angle, or density. The features may be separated into discrete zones along the incoupler such that at least one of height, spacing, angle, or density of the plurality of features is varied over the incoupler and constant within a given zone or the features may be varied continuously across the incoupler.