Curved Waveguide Virtual Image Display for Compact AR
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Solution Overview
Problem
Wearable electronic devices face challenges in providing a wide field of view and suitable resolution for virtual images while maintaining a compact, non-bulky design, especially when using projectors to produce images that need to be seen over a wide field of view and in conjunction with the outside world.
Innovation Solution
The use of a curved waveguide and separate display systems for foveal and peripheral vision, where the foveal vision system employs a holographic projector for high-resolution central images and the peripheral vision system uses an LCD with structured illumination for a wider, lower-resolution view, combined with a combiner that allows external light to pass through, enabling a 120-degree by 90-degree field of view with minimal power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a projector is used to produce virtual images for wide field of view, then the field of view is improved, but the device becomes bulky and power consumption increases
Solution Approach 1:
The patent embeds the projector within the temple of the eyeglass frame, nesting the projection system in an unused spatial region. This allows the projector to be positioned away from the main device body, achieving wide field of view without increasing the bulk of the primary device structure.
Solution Approach 2:
The patent transitions from a direct-view display plane to a three-dimensional virtual image space. By projecting images that appear to float in 3D space rather than being confined to a flat screen, the system achieves expanded field of view without proportionally increasing device volume.
2Area of stationary object
If a projector is used to produce virtual images, then the field of view is improved, but power consumption increases
Solution Approach 1:
The patent employs switchable gratings that can be selectively activated to direct light only to the foveal vision region when high resolution is needed, rather than continuously illuminating the entire field of view. This partial action reduces overall power consumption while maintaining wide field of view capability.
Solution Approach 2:
The patent implements time-multiplexed scanning of the virtual image across different regions of the field of view. By periodically updating and scanning the projected image rather than maintaining continuous illumination across the entire field, the system reduces average power consumption while preserving the perceived wide field of view.
3Measurement precision
If switchable gratings are used to direct light, then resolution is improved, but efficiency decreases and device complexity increases
Solution Approach 1:
The patent divides the field of view into distinct regions: a high-resolution foveal region served by switchable gratings and a lower-resolution peripheral region. This segmentation allows the complex, less efficient switchable grating system to be used only where high resolution is critical, while simpler optics handle the periphery, improving overall light efficiency.
Solution Approach 2:
The patent applies different optical qualities to different regions of the field of view. The foveal region receives directed, high-resolution light through switchable gratings, while the peripheral region receives broader, lower-resolution illumination. This local differentiation optimizes the balance between resolution and light efficiency across the entire visual 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 allows for a wide field of view and suitable resolution in a compact form factor, reducing power usage and enabling variable focal depth, while avoiding the inefficiencies of switchable gratings and maintaining image clarity for both central and peripheral vision.
Implementation Method 1
The waveguide constrains the light of the virtual image through total internal reflection along a curved path for the light between the projector and the combiner
Implementation Method 2
a holographic projector configured to provide light of a virtual image
Implementation Method 3
a combiner disposed along the waveguide and configured to redirect the light of the virtual image
Data Source
AI summary
A display includes a projector configured to provide light of a virtual image, a waveguide into which the light of the virtual image is injected at an injection angle by the projector, and a combiner disposed along the waveguide and configured to redirect the light of the virtual image. The waveguide is configured to emit the light at a point established by the injection angle. The combiner is further configured to allow ambient light from beyond the waveguide to pass through the combiner. The waveguide constrains the light of the virtual image through total internal reflection along a curved path for the light between the projector and the combiner.