Progressive Bias Lenses for AR Waveguide Displays
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Solution Overview
Problem
Optical systems in electronic devices, such as virtual or augmented reality headsets, often face challenges in achieving desired optical performance for viewing both virtual and real-world objects, leading to focus conflicts and viewing discomfort due to the vergence-accommodation conflict and varying distances of real-world objects within the field of view.
Innovation Solution
The use of bias lenses with specific optical powers and geometries, including a first region with a first radius of curvature, a second region with a second radius of curvature, a corridor region with constant astigmatism, and blending regions with variable astigmatism, to optimize the transmission of both virtual and real-world light within the field of view, minimizing astigmatism introduction and focusing conflicts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional lenses are used in optical systems, then the structure is simple, but the optical performance for viewing both virtual and real-world objects at various distances is poor due to focus conflicts
Solution Approach 1:
The lens is divided into multiple distinct regions (first region, second region, corridor region, and blending regions) with different optical properties. Each region is optimized for specific viewing distances and angles, allowing the lens to simultaneously provide good optical performance for both virtual objects and real-world objects at various distances without requiring multiple separate lenses.
Solution Approach 2:
Different regions of the lens are assigned different local optical qualities: the first region has a first radius of curvature optimized for virtual objects, the second region has a second radius of curvature optimized for real-world objects, the corridor region provides gradient optical power with constant astigmatism, and the blending regions have variable astigmatism. This local differentiation resolves the focus conflict while maintaining a single integrated lens structure.
2Adaptability or versatility
If a single optical power is used across the lens, then the lens structure is simple, but the ability to accommodate varying distances of real-world objects within the field of view is limited
Solution Approach 1:
The lens implements spatially varying optical parameters by assigning different radii of curvature to different regions. The first region has a first radius of curvature providing a first optical power for virtual objects, while the second region has a second radius of curvature providing a second optical power for real-world objects. The corridor region provides a gradient transition between these powers, enabling the lens to accommodate varying distances of real-world objects within the field of view.
3Reliability
If blending regions are positioned within the field of view, then the transition between optical regions is smooth, but astigmatism is introduced to the image light causing viewing discomfort
Solution Approach 1:
The lens design strategically positions the blending regions with variable astigmatism outside the field of view, creating an asymmetric distribution of optical regions. The first region, second region, and corridor region (with constant astigmatism) are positioned to overlap the field of view, while the blending regions are positioned away from it. This asymmetric arrangement prevents astigmatism introduction to image light while maintaining smooth optical transitions in the visible field.
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 configuration enhances the optical performance by allowing users to comfortably view virtual and real-world objects at various distances within the field of view, reducing focus conflicts and improving visual acuity, thereby enhancing the overall display experience.
Implementation Method 1
A first lens may transmit the world light to the output coupler
Implementation Method 2
Output couplers may couple the image light out of the waveguides and towards the eye boxes. The output couplers may also pass world light from external objects to the eye boxes within the FOV
Implementation Method 3
A second lens may transmit the world light and the image light to the eye box
Implementation Method 4
Input couplers may couple the image light into the waveguides. Output couplers may couple the image light out of the waveguides
Data Source
AI summary
A display may include a waveguide that directs image light towards an eye box within a field of view (FOV). A first lens may transmit world light to the waveguide and a second lens may transmit the world light and the image light to the eye box. One or more surfaces of the first and second lenses may collectively have a first region with a first optical power, a second region with a second optical power, a corridor with gradient optical power and constant astigmatism, and blending regions with variable astigmatism. The second region may be shifted downwards in elevation angle, the corridor may be elongated, and/or the blending regions may be disposed away from the FOV to prevent the blending regions from introducing astigmatism to the image light at the eye box.