Subgrid Calibration for AR Waveguide Displays
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Solution Overview
Problem
Current augmented reality systems face challenges in achieving uniform color representation across wearable display devices, particularly due to color shifts and variations caused by optical components and user positioning, which are not effectively addressed by conventional calibration methods.
Innovation Solution
The use of subgrid analysis and low-cost digital color cameras for calibration, converting RGB color space to CIE XYZ color space, and applying image tiling techniques to improve chromaticity uniformity across waveguide displays, enabling pixel-by-pixel correction and reducing the complexity and cost of grid-by-grid correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional calibration methods are used, then the calibration process is simple, but chromaticity uniformity across the display is poor
Solution Approach 1:
The patent divides the display into multiple subgrids with different pixel densities. High-density subgrids are applied to regions requiring precise chromaticity uniformity (such as central viewing areas), while low-density subgrids are used in peripheral regions. This segmentation allows the system to achieve high manufacturing precision where needed without uniformly increasing complexity across the entire display.
Solution Approach 2:
The patent implements location-dependent subgrid calibration where different correction matrices are applied to different spatial regions of the display. The calibration parameters are optimized locally for each subgrid region based on its specific chromaticity characteristics, enabling high chromaticity uniformity in critical areas while reducing overall calibration complexity through regionalization.
2Manufacturing precision
If pixel-by-pixel correction is implemented, then chromaticity uniformity is improved, but computational complexity and processing time increase
Solution Approach 1:
The patent segments the pixel correction task into subgrid-level corrections. Instead of processing every pixel individually across the entire display, the system divides pixels into groups belonging to different subgrids and applies subgrid-specific correction matrices. This reduces the computational complexity from O(N) pixel-by-pixel operations to O(M) subgrid-by-subgrid operations, where M << N, significantly reducing calibration time while maintaining chromaticity uniformity.
Solution Approach 2:
The patent applies partial correction action by focusing computational resources on correcting chromaticity issues in high-priority subgrids (such as central regions) with higher precision, while applying coarser correction to peripheral subgrids. This selective approach achieves acceptable chromaticity uniformity across the display without the excessive computational time required for uniform high-precision correction of all pixels.
3Manufacturing precision
If high-density subgrids are used across the entire display, then chromaticity uniformity is improved, but manufacturing cost and device complexity increase
Solution Approach 1:
The patent segments the display into multiple subgrid regions and assigns different subgrid densities to different regions based on their importance. High-density subgrids are deployed only in critical regions (such as the central field of view) where chromaticity uniformity is most important, while low-density subgrids are used in less critical peripheral regions. This reduces the total number of subgrids required, lowering manufacturing cost and device complexity while maintaining chromaticity uniformity where it matters most.
Solution Approach 2:
The patent implements location-dependent subgrid density optimization where the subgrid resolution is adapted to local requirements. Regions requiring high chromaticity uniformity (such as central viewing areas) receive high-density subgrids, while peripheral regions with lower uniformity requirements use low-density subgrids. This local optimization achieves high manufacturing precision in critical areas without the prohibitive cost of uniform high-density subgrids across the entire display.
Data Source
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Figure 4A
AI summary
A method for calibrating a wearable device includes displaying an image with a plurality of pixels for each of three primary colors using the wearable device, and determining RGB and XYZ values for each of the plurality of pixels. The method includes selecting a subset of the plurality of pixels to form a group of grid points, and dividing the image into a group of tile regions, with each tile region including a grid point. Grid XYZ values are determined for each grid point, based on averaging XYZ values of all pixels in a corresponding tile region, and a grid RGB-to-XYZ conversion matrix is determined for each grid point. The method also includes determining a correction matrix for each grid point by multiplying an inverse of the grid RGB-to-XYZ conversion matrix for the grid with an sRGB-to-XYZ conversion matrix.