Curved Lightguide Eyepiece for See-Through AR Displays
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Solution Overview
Problem
Conventional head-mounted displays (HMDs) face limitations in cost, size, weight, field of view, and efficiency due to their optical systems, which restrict their practical and leisure applications, particularly in augmented reality where see-through eyepieces are required to overlay computer-generated imagery onto the real world.
Innovation Solution
The design incorporates a curved lightguide component with input and output couplers utilizing total internal reflections to guide display light, combining it with ambient light while maintaining a see-through capability, using a thin and lightweight structure with complementary curvatures to offset optical power and enhance the field of view.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional optical systems are used in HMDs, then the basic display function is achieved, but the cost, size, weight, field of view, and efficiency are limited
Solution Approach 1:
The patent employs a curved waveguide with non-planar geometry to expand the field of view. The curved structure allows light to propagate along a curved path, enabling a wider angular coverage compared to flat waveguides. This curvature is integrated into the eyepiece design to naturally guide light from the display element to the user's eye while expanding the visible field.
Solution Approach 2:
The patent integrates multiple optical functions within a single compact eyepiece structure. The waveguide, couplers, and optical elements are nested within each other, with the display element positioned inside or adjacent to the waveguide structure. This nesting approach reduces overall system size and complexity while maintaining multiple optical functions.
2Adaptability or versatility
If see-through eyepiece is used for augmented reality, then real-world view is visible, but optical efficiency and image quality are compromised
Solution Approach 1:
The patent implements spatially varying optical properties within the eyepiece structure. The waveguide has different refractive indices in different regions, with coupling regions designed to selectively extract or input light at specific locations. The curved structure provides different optical paths for different field angles, optimizing both see-through capability and display efficiency in their respective regions.
Solution Approach 2:
The curved waveguide structure optimizes light propagation paths to maintain high efficiency while enabling see-through capability. The curvature allows for extended optical paths within a compact form factor, improving light extraction efficiency at the display region while maintaining transparency in the optical path region for real-world view.
3Weight of moving object
If thin and lightweight structure is used, then comfort is improved, but optical power and focusing capability are reduced
Solution Approach 1:
The curved waveguide structure provides inherent optical power through its geometry. The curvature radius is designed to provide the necessary focusing capability while maintaining a thin profile. This eliminates the need for additional heavy lens elements, as the curved waveguide itself acts as the optical element providing both structural support and optical function.
Solution Approach 2:
The waveguide structure serves multiple functions simultaneously: it provides mechanical support, guides light propagation, provides coupling interfaces, and delivers optical power through its curvature. This multi-functionality eliminates the need for separate components, reducing overall weight while maintaining optical performance.
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 provides a compact, efficient, and see-through eyepiece that extends the eyebox by stitching together ray bundles, offering a larger field of view and undistorted ambient vision, suitable for augmented reality applications with improved industrial design and reduced optical distortion.
Implementation Method 1
utilizing total internal reflections to guide display light
Implementation Method 2
input and output couplers utilizing total internal reflections to guide display light
Data Source
AI summary
An eyepiece for a head wearable display includes a curved lightguide component, an input coupler, and an output coupler. The curved lightguide component guides display light received at an input region peripherally located from a viewing region and emits the display light along an eye-ward direction in the viewing region. The curved lightguide component includes an eye-ward facing surface that is concave and a world facing surface that is convex. The input coupler is disposed at the input region to couple the display light into the curved lightguide component. The output coupler is disposed at the viewing region to redirect the display light towards the eye-ward direction for output from the curved lightguide component. The output coupler is partially transmissive to ambient light incident through the world facing surface. The display light is guided between the input coupler and the output coupler entirely by total internal reflection.