Light Shuttering for Waveguide Pupil Expansion Through Ordered Cell Updates
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Solution Overview
Problem
The existing light shuttering devices in waveguide pupil expansion systems suffer from slow switching times, particularly when liquid crystal cells relax to their new state, leading to incomplete updates and incorrect blocking or transmission of light, causing image distortion and confusion in multi-entrance pupil viewing systems.
Innovation Solution
A drive circuit is employed to control a light shuttering device with a plurality of liquid crystal cells, using specific drive signals and an ordered update sequence to compensate for slower switching times, ensuring rapid and complete configuration changes, preventing simultaneous light propagation to multiple viewing apertures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If liquid crystal cells are used in the light shuttering device, then the device can be manufactured with available technology and acceptable cost, but the switching time becomes too slow causing incomplete updates and image distortion
Solution Approach 1:
The system performs preliminary actions by pre-calculating the required shuttering configuration and preparing the drive signals before the liquid crystal cells need to switch. The ordered update sequence pre-positions the system state so that cells requiring longer relaxation times are updated first, ensuring complete switching before the next frame begins.
Solution Approach 2:
The system dynamically adjusts the update sequence based on the current state of each liquid crystal cell. Rather than updating all cells simultaneously or in a fixed sequence, the system adapts the update order to account for varying switching characteristics of individual cells, optimizing the overall response time while maintaining manufacturability with standard liquid crystal technology.
2Manufacturing precision
If the light shuttering device updates configuration quickly, then image clarity is improved, but the complexity of the drive circuit and control logic increases
Solution Approach 1:
The drive circuit is segmented into multiple independent update channels, each capable of controlling specific groups of liquid crystal cells. This segmentation allows parallel processing of different cell groups, achieving fast overall update without requiring a monolithic complex control unit. Each segment operates with simpler logic, reducing the complexity burden on any single control element.
Solution Approach 2:
The system replaces complex mechanical switching mechanisms with electronically controlled liquid crystal cells that can be driven through software-defined update sequences. The control complexity is shifted from hardware circuitry to programmable logic, allowing flexible adjustment of update sequences without physical reconfiguration and enabling precise timing control through digital signal processing.
3Speed
If liquid crystal cells are updated in parallel, then the update speed is improved, but the relaxation time limitation causes incomplete switching and light control errors
Solution Approach 1:
The system performs preliminary classification of liquid crystal cells based on their switching characteristics before the update cycle begins. Cells are pre-grouped into sequences that account for their individual relaxation times, ensuring that cells requiring longer switching times are addressed first in the update sequence. This preliminary organization enables reliable complete switching while maintaining high overall update speed.
Solution Approach 2:
The system dynamically changes the update parameters for different groups of liquid crystal cells, applying different timing sequences and drive signal characteristics to cells based on their specific switching behavior. This parameter adaptation allows each cell to be updated at the optimal moment in the sequence, ensuring complete switching for all cells while maintaining high overall update throughput through coordinated parallel processing of cell groups.
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 quick and accurate light control, preventing overlap of image content between viewing apertures, enhancing image clarity and reducing viewer confusion in multi-entrance pupil systems.
Implementation Method 1
Each pixel of the light shuttering device is directly driven by one of: a first drive signal and a second drive signal. Each liquid crystal cell is operable in a first optical state or a second optical state in response to a respective first or second drive signal.
Implementation Method 2
EP0136085A1 discloses an electro-optical device for influencing the presentation of visual information when placed before the eyes of an observer, comprising one or more cholesteric liquid crystal cells which, under the control of an electric driving signal, can be rapidly switched, by means of the cholesteric-nematic phase change effect, between a clear transparent texture and a cloudy, scattering texture.
Implementation Method 3
the liquid crystal cell takes longer to switch from the second optical state to the first optical state than from the first optical state to the second optical state
Data Source
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AI summary
A light shuttering device comprises a plurality of liquid crystal cells, wherein each liquid crystal cell is operable in a first optical state or a second optical state in response to a respective first or second drive signal. A drive circuit comprises a plurality of switches and a drive controller. Each switch is arranged to output the respective first or second drive signal to a respective liquid crystal cell. The drive controller is arranged to sequentially update the output of each switch during an update cycle. The drive circuit is arranged to determine the order in which the switches are sequentially updated during an update cycle based on any changes to the respective drive signals that will be made during the update.