Curved GRIN Waveguide for Astigmatism-Corrected AR Imaging
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Solution Overview
Problem
Existing optical waveguides in head-mounted displays, such as AR headsets, suffer from significant astigmatic imaging errors and bulkiness due to the use of curved waveguides combined with refractive lenses, which cannot be compensated within the waveguide and result in thick, heavy systems.
Innovation Solution
Incorporating a Gradient Index (GRIN) element with a curved surface and a tailored refractive index distribution to correct aberrations caused by curvature, allowing for a compact and lightweight design that maintains image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a curved optical waveguide is used to support appealing product design, then the shape and aesthetics are improved, but astigmatic imaging errors increase and cannot be compensated
Solution Approach 1:
The patent applies parameter changes by modifying the refractive index distribution within the waveguide material. By creating a gradient index profile where the refractive index varies spatially (higher at edges, lower at center), the waveguide compensates for astigmatic errors introduced by curvature while maintaining the desired curved shape for aesthetic purposes.
2Reliability
If push-pull lenses are added to correct refractive errors and focus virtual images, then optical performance is improved, but system thickness and weight increase
Solution Approach 1:
The patent merges the functions of the waveguide and refractive error correction into a single integrated component. The curved waveguide with gradient index profile simultaneously guides light, corrects astigmatism from curvature, and provides refractive error correction, eliminating the need for separate push-pull lenses and reducing overall system weight.
Solution Approach 2:
The waveguide structure is designed to perform multiple functions: guiding light through total internal reflection, correcting astigmatic imaging errors through its curved geometry and gradient index, and providing refractive error correction for different user prescriptions. This multi-functionality replaces what would traditionally require multiple separate optical components.
3Adaptability or versatility
If multiple lenses are integrated with the optical waveguide, then refractive error correction is achieved, but device complexity and system volume increase
Solution Approach 1:
The patent uses parameter changes by implementing a gradient refractive index profile within the waveguide material. This continuous variation of the refractive index parameter allows the waveguide to correct refractive errors and astigmatism without requiring additional discrete lens elements, thereby reducing device complexity and system volume.
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 GRIN element reduces astigmatic errors and allows for a compact, lightweight optical waveguide that provides an aberration-free large field of view without impairing the view of the surroundings, enabling appealing product designs.
Implementation Method 1
An optical waveguide (light guide) is understood to mean a waveguide designed to guide or transmit light waves through the waveguide in the interior thereof by way of total-internal reflection at the waveguide surfaces
Implementation Method 2
The GRIN element moreover has a refractive index distribution designed to reduce the aberrations, brought about by the curvature of the GRIN element, in an imaging path of a virtual image representation
Data Source
AI summary
An optical waveguide is provided for arrangement in the beam path of an optical arrangement with a device for output coupling and/or input coupling an imaging beam path. The optical waveguide includes a GRIN element having at least one curved surface. The GRIN element has a refractive index distribution designed to reduce the aberrations, arising due to the curvature of the GRIN element, in an imaging path of a virtual image created by light waves guided in the optical waveguide by total-internal reflection.