Curved Waveguides with Spatially Modulated Gratings
Solution Overview
Problem
Current augmented reality display systems using optical waveguides face challenges such as inadvertent out-coupling of light, aberrations, and lateral color errors due to the curvature of waveguides, which affect image quality and field of view, making it difficult to achieve a wide horizontal field of view and correct for varying aberrations over different field angles.
Innovation Solution
The use of curved optical waveguides with spatially modulated grating periods and adaptive optics to ensure light remains above the critical angle, combined with polynomial surfaces to compensate for lateral color errors and distortion, and adaptive optics to correct for aberrations varying over the field of view, allowing for increased horizontal field of view and improved image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If curved optical waveguides are used to expand horizontal field of view, then field of view is improved, but light inadvertently out-couples before reaching output-grating
Solution Approach 1:
The waveguide geometry is specifically designed to keep internally reflected light below the critical angle throughout its path, preventing inadvertent out-coupling before light reaches the output-grating. This preliminary design constraint ensures light remains confined within the waveguide substrate.
Solution Approach 2:
Curved surfaces of the optical waveguide are designed with specific curvature radii to manage light propagation paths. The curved geometry enables expanded horizontal field of view while maintaining control over internal reflection angles to prevent premature light out-coupling.
2Area of stationary object
If curved waveguide surfaces are used, then field of view is expanded, but lateral color errors and distortion increase
Solution Approach 1:
Different regions of the waveguide surface are assigned different curvature radii. The curved surfaces have varying local properties (different curvature radii in different regions) to compensate for lateral color errors and distortion while maintaining expanded field of view capability.
3Productivity
If output-grating is used to out-couple light, then image is delivered to user, but rays from different locations are not collimated
Solution Approach 1:
The output-grating features a spatially modulated grating period where different regions have different grating periods. This local variation in grating properties ensures that rays out-coupled from different locations are substantially collimated, improving image quality.
4Manufacturing precision
If adaptive optics are added to correct aberrations, then image quality is improved, but device complexity increases
Solution Approach 1:
The adaptive optics system dynamically adjusts optical parameters (such as lens shape or mirror curvature) to compensate for aberrations that vary across the field of view. This parameter adjustment enables aberration correction while managing system complexity through controlled adaptability.
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 solution effectively prevents inadvertent out-coupling of light, corrects aberrations, and ensures collimated output rays, enhancing image clarity and expanding the horizontal field of view beyond 50 degrees, providing a more immersive augmented reality experience.
Implementation Method 1
the output-grating of the curved optical waveguide includes a spatially modulated grating period configured to cause, for each beam of light corresponding to an image that is coupled into a bulk-substrate of the optical waveguide by an input-grating, corresponding rays of light that are output from different locations of the output-grating to be substantially collimated
Implementation Method 2
a curved portion of the optical waveguide is specifically designed to keep internally reflected light below a critical angle, and thereby, to prevent inadvertent out-coupling of the light corresponding to the image before the light reaches the output-grating and distal portions thereof
Implementation Method 3
curved surfaces of the optical waveguide can also include polynomial surfaces to compensate for lateral color errors and distortion
Data Source
AI summary
Apparatuses and systems including curved optical waveguides, and methods for use include an output-grating of a curved waveguide that includes a spatially modulated grating period configured to cause, for each beam of light corresponding to an image coupled into a bulk-substrate of the curved waveguide by an input-grating, corresponding rays of light output from different locations of the output-grating to be substantially collimated. Adaptive optics of a display engine compensate for aberrations that vary over a field-of-view associated with light corresponding to the image out-coupled by the output-grating. Further, a curved portion of the curved waveguide is designed to keep internally reflected light below a critical angle to prevent inadvertent out-coupling thereof. Further, curved surfaces of the curved waveguide can include polynomial surfaces to compensate for lateral color errors and distortion.