Liquid Crystal Eyebox Steering in Waveguide Displays
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Solution Overview
Problem
Conventional wearable head-mounted display (WHMD) devices face challenges in accommodating varying user head geometries, leading to reduced efficiency and color uniformity in projected light, along with fabrication difficulties and increased costs due to the need for a single outcoupler size to fit a wide range of users.
Innovation Solution
An eyebox expander for WHMDs is introduced, comprising a first liquid crystal layer and an electrode arrangement that modifies the orientation of the liquid crystals to steer light beams, with a compensation layer to counteract distortion effects, allowing for a smaller outcoupler size while maintaining efficient light distribution across a wide range of user geometries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If a larger outcoupler size is used to accommodate a wider range of user head geometries, then the eyebox width is increased, but the efficiency and color uniformity of the projected light are reduced
Solution Approach 1:
The patent applies liquid crystal layers with electrode arrangements that can dynamically change the orientation of liquid crystals to steer light beams. This dynamic control allows the system to adapt the light distribution to different user head geometries without requiring a physically larger outcoupler, thereby maintaining light efficiency while accommodating variable eyebox requirements
Solution Approach 2:
The patent changes the optical parameters of the light path by using liquid crystal orientation control to steer light beams at different angles. By modifying the orientation parameter of liquid crystals through applied voltages, the system can redirect light to accommodate different interpupillary distances and head geometries without increasing the physical size of the outcoupler
2Area of moving object
If a larger outcoupler size is used to accommodate a wider range of user head geometries, then the eyebox width is increased, but the color uniformity of the projected light is reduced
Solution Approach 1:
The dynamic liquid crystal steering mechanism allows precise control over light distribution across the eyebox. By adjusting liquid crystal orientations in real-time, the system can maintain uniform color distribution across different viewing positions and user geometries, eliminating the color non-uniformity that would result from a fixed larger outcoupler design
Solution Approach 2:
The patent implements local control of light steering by using patterned electrodes that can independently control different regions of the liquid crystal layer. This allows each local area of the eyebox to receive optimally directed light with consistent color properties, regardless of the overall eyebox size or user head geometry
3Adaptability or versatility
If a single outcoupler size is used for a wide range of user head geometries, then the device can accommodate more users, but fabrication challenges and increased costs occur
Solution Approach 1:
The liquid crystal eyebox steering mechanism serves multiple functions: it accommodates different interpupillary distances, adjusts for various head widths, and compensates for different eye positions. This single multi-functional component replaces the need for multiple outcoupler sizes, simplifying fabrication while maintaining versatility across diverse user populations
Solution Approach 2:
Instead of manufacturing different physical outcoupler sizes for different user groups, the patent uses a single outcoupler combined with liquid crystal parameter control. By changing the optical parameters (light steering angles) rather than the physical dimensions, the system achieves adaptability without increasing fabrication complexity
4Adaptability or versatility
If a single outcoupler size is used for a wide range of user head geometries, then the device can accommodate more users, but the efficiency of projected light is reduced
Solution Approach 1:
The dynamic liquid crystal steering system continuously adapts light distribution to match the specific user geometry. This ensures that light is efficiently directed to the correct eyebox position for each user, maintaining high light distribution efficiency across different users without the waste that would occur with a fixed single-size outcoupler design
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 solution enables improved projected image quality and a more realistic portrayal of the real world view, enhancing user experience by dynamically steering light beams to accommodate different user head geometries without increasing outcoupler size, thus increasing efficiency and reducing costs.
Implementation Method 1
a first liquid crystal layer, an electrode arrangement to apply a voltage to the first liquid crystal layer to modify an orientation associated with the first liquid crystal layer
Implementation Method 2
an electrode arrangement to apply a voltage to the first liquid crystal layer to modify an orientation associated with the first liquid crystal layer to steer light beams
Implementation Method 3
a compensation layer to redirect light passing through the eyebox expander based on the modification of the orientation associated with the first liquid crystal layer
Data Source
AI summary
The disclosure herein presents an eyebox expander for a wearable head mounted display. The eyebox expander includes a first liquid crystal layer: an electrode arrangement to apply a voltage to the first liquid crystal layer to modify an orientation associated with the first liquid crystal layer; and a compensation layer to redirect light passing through the eyebox expander based on the modification of the orientation associated with the first liquid crystal layer.