Sequential Colour Matrix LCD Grey Level Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Sequential color liquid crystal displays face challenges in maintaining image quality due to insufficient time for pixels in the last rows to reach their new video set values, leading to stroboscopic effects and color break-up issues, particularly when increasing color display frequency to address response time constraints.
Innovation Solution
Implementing a system where grey levels are controlled using analogue voltages that vary monotonously based on the row and color, allowing for optimized grey scale generation as a function of the row position and color, enabling multiple colored sub-frames per primary color within each video frame.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the color display frequency is increased to reduce liquid crystal stabilization time, then the colour break-up problem is reduced, but the pixels in the last rows do not have enough time to reach their new video set values
Solution Approach 1:
The patent applies preliminary action by pre-charging pixel capacitors during the addressing phase before the actual display phase. During the addressing phase, voltage levels are transferred to pixel capacitors, and during the display phase, these pre-charged capacitors maintain the voltage levels without requiring continuous charging. This allows the system to use longer row periods (e.g., 6.4 ms) that provide sufficient time for liquid crystal stabilization while maintaining accurate voltage levels across all rows including the last rows.
Solution Approach 2:
The patent segments the frame period into distinct addressing phase and display phase intervals. The addressing phase is further divided into multiple row periods during which different rows are addressed sequentially. This segmentation allows each row to be addressed with sufficient time for voltage transfer and liquid crystal response, while the overall frame rate can be maintained at high values (e.g., 60 Hz or higher) to reduce color break-up effects.
2Productivity
If the row scanning speed is increased to reduce the time per coloured sub-frame, then the response time constraint is met, but the first and last rows have insufficient time to switch between video levels
Solution Approach 1:
The patent uses preliminary action by completing the voltage transfer to pixel capacitors during the addressing phase before the display phase begins. The liquid crystal molecules are given sufficient time to respond to these pre-applied voltage levels during the display phase, rather than attempting to switch during the brief row scanning interval. This separates the voltage application timing from the liquid crystal response timing, allowing both to occur with adequate duration.
Solution Approach 2:
The patent implements dynamic timing where the row period duration is optimized based on the specific requirements of the liquid crystal material and display configuration. For example, with TN type liquid crystals, the row period is set to 6.4 ms which provides adequate time for the 3.25 ms worst-case grey level transition. The system dynamically adjusts the balance between addressing phase and display phase durations to ensure all rows receive sufficient time for voltage stabilization and liquid crystal response.
3Speed
If the liquid crystal response time is reduced to meet the strict timing constraints, then the pixel switching speed is improved, but the image quality deteriorates due to insufficient convergence time
Solution Approach 1:
The patent applies preliminary action by transferring voltage levels to pixel capacitors during the addressing phase, allowing the liquid crystal molecules to begin their response process before the display phase starts. The addressing phase is designed with sufficient duration to allow voltage stabilization, and the display phase maintains these voltage levels without interruption. This ensures that even pixels in the last rows have adequate time to converge to their target levels without compromising image quality.
Solution Approach 2:
The patent ensures continuity of useful action by maintaining stable voltage levels on pixel capacitors throughout the display phase. Once voltage levels are established during the addressing phase, they are maintained continuously during the display phase without interruption or re-charging. This continuous voltage application allows liquid crystal molecules to complete their response process without interruption, ensuring accurate image quality while maintaining high frame rates.
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 improves display performance by reducing stroboscopic effects and maintaining image quality, ensuring that all pixels can converge to their target levels, even in the last rows, by dynamically adjusting analogue voltage levels according to row position and color, thereby optimizing brightness and energy usage.
Implementation Method 1
The liquid crystal is then oriented in a direction that depends on the applied analogue value
Implementation Method 2
The display performance depends particularly on the brightness that depends on the pixel illumination time
Data Source
AI summary
A video system including a sequential color liquid crystal display with a panel of pixels arranged in rows and columns, including a mechanism that controls unit brightness levels on each pixel in the panel called grey levels, each grey level corresponding to a video information received at the input. The grey level controlled on a pixel is achieved with an analog voltage that varies monotonously depending on the row associated with the pixel and/or a color to be displayed.