Switchable Grating Waveguide for Compressed Eyebox
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Solution Overview
Problem
Near-eye displays face challenges in efficiently directing image light to the eye pupil, leading to low brightness and power inefficiency due to the large eyebox size, which results in significant light loss outside the pupil area.
Innovation Solution
The system employs a waveguide display with switchable gratings that can operate in diffraction or non-diffraction states, configuring combinations of gratings to direct image light through sub-eyeboxes, forming either an uncompressed or compressed eyebox, thereby optimizing light intensity and power efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a large eyebox is provided to accommodate eye movement, then the field of view is improved, but light intensity at the pupil decreases and power efficiency worsens due to light loss outside the pupil area
Solution Approach 1:
The patent implements dynamically switchable gratings that can change their diffraction state in real-time. The controller adjusts the grating configuration based on detected eye position, transitioning between compressed eyebox mode (when eye is centered) and expanded eyebox mode (when eye moves), thereby optimizing both power efficiency and adaptability across different viewing conditions
Solution Approach 2:
The patent changes the optical parameters of the waveguide system by switching grating states. When the eye is centered, gratings are configured to compress the eyebox to concentrate light and improve power efficiency. When the eye moves, gratings are switched to expand the eyebox to maintain field of view and adaptability, thus dynamically adjusting parameters to resolve the contradiction
2Adaptability or versatility
If a large eyebox is provided to accommodate eye movement, then the field of view is improved, but light intensity at the pupil decreases due to light loss outside the pupil area
Solution Approach 1:
The system dynamically adjusts the eyebox size by switching grating configurations based on real-time eye position detection. When the eye is centered, the compressed eyebox configuration concentrates light to maximize intensity at the pupil. When the eye moves, the expanded configuration maintains adequate light delivery while accommodating the shifted pupil position
Solution Approach 2:
The patent applies different grating configurations to different regions of the waveguide. The switchable gratings create localized optical paths that are optimized for the current eye position, concentrating light precisely where the pupil is located while maintaining the ability to expand coverage when needed
3Use of energy by moving object
If switchable gratings are used to dynamically adjust eyebox size, then power efficiency and light intensity are improved, but device complexity increases
Solution Approach 1:
The switchable gratings serve multiple functions: they act as both in-coupling and out-coupling elements, provide eyebox compression and expansion, and enable light guiding. This multi-functionality reduces the need for separate components, thereby limiting the increase in device complexity while achieving improved power efficiency
Solution Approach 2:
The patent combines the eyebox control function with the existing waveguide light guiding structure. The switchable gratings are integrated into the waveguide itself, merging the eyebox adjustment mechanism with the light transmission path, thus minimizing additional complexity while achieving dynamic eyebox control
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 approach increases light intensity at the eye pupil, reduces light loss, and enhances power efficiency by dynamically adjusting the eyebox size to match the eye pupil, while maintaining the full field of view and reducing ghosting effects.
Implementation Method 1
a diffraction grating may be configured based on a diffraction equation: mλ=d(sinθi+sinθd), where m is the diffraction order, λ is the wavelength of incident light, d is the grating period, θi is the incident angle, and θd is the diffracted angle
Data Source
AI summary
A system includes one or more waveguides, and a plurality of grating sets coupled with the one or more waveguides. A plurality of combinations of gratings from the grating sets are configurable to direct an image light to propagate through a plurality of sub-eyeboxes forming an uncompressed eyebox. The system also includes a controller configured to selectively configure one or more combinations of gratings to operate in a diffraction state to direct the image light to propagate through one or more sub-eyeboxes forming a compressed eyebox having a size smaller than a size of the uncompressed eyebox.