Pupil Steering via Liquid Crystal Modulation in Waveguide Displays
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Solution Overview
Problem
Conventional near-eye displays face challenges in achieving a small form factor, large field-of-view, and wide eye box while maintaining brightness, as pupil expansion leads to light wastage due to a static and oversized exit pupil that accommodates varying inter-pupil distances and gaze angles.
Innovation Solution
Pupil steering is implemented using a liquid crystal layer in the waveguide display to modulate diffraction efficiency spatially and temporally, allowing the exit pupil to be dynamically adjusted based on eye tracking, ensuring that light is only decoupled where it will be seen by the user, thereby reducing waste and maintaining brightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a static and oversized exit pupil is used to accommodate varying inter-pupil distances and gaze angles, then adaptability is improved, but light loss increases
Solution Approach 1:
The patent implements a dynamic exit pupil that can be steered to different positions using a liquid crystal layer in the waveguide display. This allows the exit pupil to adapt to varying inter-pupil distances and gaze angles by moving its position dynamically, rather than using a static oversized pupil. The liquid crystal layer modulates the position of the exit pupil in response to eye tracking data, enabling the system to maintain adaptability while minimizing light loss by only expanding light at the needed location.
2Ease of operation
If pupil expansion is implemented to provide a large eye box, then ease of operation is improved, but light loss increases
Solution Approach 1:
The patent uses a dynamic, steerable exit pupil that moves with the user's eye position through liquid crystal modulation. This allows the system to provide a large effective eye box by tracking eye movement and repositioning the exit pupil accordingly, rather than using a static large expansion. The pupil expander only expands light at the specific location where the user's eye is positioned, maintaining ease of operation while minimizing light loss.
Solution Approach 2:
The system uses eye tracking to automatically determine the user's eye position and dynamically adjusts the exit pupil position accordingly. This self-adjusting mechanism ensures the expanded light always reaches the user's eye without requiring manual adjustment or over-expansion, thereby maintaining ease of operation while reducing light loss.
3Illumination intensity
If a larger exit pupil is used to maintain brightness across varying eye positions, then illumination intensity is improved, but device complexity increases
Solution Approach 1:
The patent implements a dynamic exit pupil steering mechanism using a liquid crystal layer that can electronically reposition the exit pupil without requiring complex mechanical adjustments to the optical system. This allows the system to maintain brightness at the user's eye position by dynamically moving the exit pupil rather than using a permanently oversized pupil, thereby achieving illumination intensity improvement with minimal increase in device complexity.
Solution Approach 2:
The patent replaces complex mechanical optical adjustment mechanisms with an electronic liquid crystal-based pupil steering system. The liquid crystal layer modulates the position of the exit pupil through electrical control based on eye tracking data, eliminating the need for complex mechanical moving parts while maintaining brightness and adaptability.
4Loss of energy
If pupil steering with liquid crystal layer is implemented, then light loss is reduced, but device complexity increases
Solution Approach 1:
The patent integrates the liquid crystal layer into the existing waveguide display structure, allowing it to serve dual functions: maintaining the display's primary function while adding pupil steering capability. This multi-functionality approach reduces the need for separate dedicated pupil steering components, thereby minimizing the increase in device complexity while achieving light loss reduction through dynamic pupil positioning.
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 allows for a smaller exit pupil that is dynamically steered to match the user's eye position, reducing light loss and maintaining image visibility while minimizing power consumption and heat generation, thus achieving a compact and efficient near-eye display.
Implementation Method 1
an optical element comprising a liquid crystal layer, wherein the liquid crystal layer is configured to modulate a position of the exit pupil
Implementation Method 2
A waveguide display comprises a grating structure to out couple light from a waveguide
Data Source
AI summary
A pupil expander spatially modulates decoupling efficiency of light for pupil steering. The pupil expander can be used in a waveguide display, such as part of an artificial-reality display, to reduce power consumption of an optical source.