Waveguide Light Shuttering Circuit for Sequential LC Cell Switching
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Solution Overview
Problem
The switching time period for pixels of a light shuttering device, particularly when switching to the relaxed state, is too long, leading to incomplete updates and potential misalignment of light propagation during frame changes, compromising performance in waveguide-based image projection systems.
Innovation Solution
A drive circuit for the light shuttering device is implemented, which sequentially updates liquid crystal cells based on their switching times, ensuring all cells are fully updated within the required time frame by prioritizing slower switches first, using a first and second drive signal to compensate for the longer relaxation time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If liquid crystal cells are used in the light shuttering device, then light blocking or transmission can be achieved, but the switching time period is too long leading to incomplete updates
Solution Approach 1:
The drive circuit performs preliminary action by updating liquid crystal cells in a specific sequence based on their switching characteristics. Slower-switching cells are updated first in the sequence, allowing them sufficient time to complete their state change before the frame ends, while faster cells are updated later. This preliminary ordering of operations ensures all cells complete their switching within the available time frame.
Solution Approach 2:
The system dynamically adapts the update sequence of liquid crystal cells based on their individual switching characteristics. Rather than using a static uniform update approach, the drive circuit adjusts the timing and sequence of updates to match the dynamic behavior of each cell type, optimizing the overall switching performance within the frame time constraint.
2Device complexity
If all liquid crystal cells are updated simultaneously, then the update process is simple, but slower cells do not complete switching leading to misalignment
Solution Approach 1:
The update process is segmented into multiple sequential phases, with each phase dedicated to updating specific groups of liquid crystal cells. Instead of a single simultaneous update, the drive circuit divides the cell array into segments that are updated in order, allowing each segment sufficient time to complete its transition. This segmentation transforms a complex timing problem into a manageable sequence of simpler operations.
Solution Approach 2:
The system changes the temporal parameters of the update process by varying the update timing for different cell groups. The drive circuit modifies when each group of cells receives its update signal, creating a staggered timing pattern that accounts for differences in switching speeds. This parameter adjustment ensures all cells complete switching before the frame concludes, maintaining proper light propagation alignment.
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
Ensures rapid and accurate light blocking or transmission, aligning with display frame rates, preventing incorrect light propagation and maintaining image clarity in waveguide-based projection systems.
Implementation Method 1
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
Data Source
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.