Liquid Crystal Waveguide for Uniform Brightness in Near-Eye Displays
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Solution Overview
Problem
Near-eye display systems with waveguide-based displays face issues of non-uniform brightness due to multipath interference, affecting the visual experience by causing some light intensity signals to be canceled or superimposed, leading to inconsistent image light emission.
Innovation Solution
A liquid crystal (LC) waveguide display is integrated into the near-eye display, featuring a LC layer between two glass layers that adjusts the phases of image light to average out interference patterns, ensuring uniform brightness across the output area through rapid modulation and phase control, facilitated by a controller generating emission instructions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If light propagates through a waveguide in multiple paths with approximately the same optical path length, then the waveguide-based display achieves pupil matching between human vision system and display system, but multipath interference causes non-uniform brightness of image light
Solution Approach 1:
The patent applies dynamics by modulating the liquid crystal layer at a frequency higher than the frame rate, dynamically changing the phase of light propagating through different waveguide paths. This dynamic modulation causes the interference patterns to vary over time, and when averaged over multiple frames, produces uniform brightness while maintaining pupil matching functionality
Solution Approach 2:
The patent implements periodic action through high-frequency modulation of the liquid crystal layer, where the modulation frequency exceeds the frame rate. This periodic changing of light phase creates time-varying interference patterns that, when averaged over time, eliminate brightness non-uniformity while preserving the waveguide's pupil expansion capability
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 LC waveguide display achieves substantially uniform brightness of image light directed to the user's eye, enhancing the visual experience by averaging out interference patterns and minimizing non-uniformity between neighboring pixels.
Implementation Method 1
a LC layer between the first glass layer and the second glass layer, the LC layer being configured to adjust phases of the image light
Implementation Method 2
light propagates through a waveguide in multiple paths with an approximately same optical path length. Because of that, some light intensity signals are canceled on the waveguide, whereas some other light intensity signals are superimposed on the waveguide. Due to this multipath interference effect, the brightness of image light emitted from a waveguide-based display is non-uniform
Data Source
AI summary
A near-eye display (NED) includes a source assembly that emits image light, a waveguide-based display assembly, and a controller coupled to the waveguide-based display assembly, and an optical assembly. The waveguide-based display assembly includes a liquid crystal (LC) waveguide, an input area, and an output area. The LC waveguide comprising a first glass layer, a second glass layer, and a LC layer between the first and second glass layers. The LC waveguide propagates the image light in-coupled via the input area in accordance with emission instructions toward the output area that out-couples the image light to a user's eye. The controller generates the emission instructions and provides the emission instructions to the LC waveguide for generating the image light of substantially uniform brightness.