Color Sequential LC Display Pulse Timing for Brighter High-Frame-Rate Output
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Solution Overview
Problem
Color sequential LC displays face challenges in achieving higher frame rates and brightness due to illumination gaps needed for LC relaxation and ramp times, leading to reduced illumination duty cycle, brightness, and motion artifacts.
Innovation Solution
The long-ramp control scheme overlaps relax and ramp windows, dynamically adjusts rising edge timing based on previous and current pixel intensity values, and uses a driver circuit with a lookup table to select optimal pulse start times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If illumination gaps are increased to allow LC relaxation and ramp times, then liquid crystal response time is improved, but illumination duty cycle and brightness are reduced
Solution Approach 1:
The patent applies preliminary action by initiating the ramp phase before the illumination gap ends, so that the liquid crystal pixels are already partially transitioned when illumination begins. This overlapping timing allows the system to reduce the required illumination gap duration while maintaining adequate pixel transition, thereby increasing illumination duty cycle and brightness without sacrificing response time
Solution Approach 2:
The patent implements dynamics by dynamically adjusting the timing and duration of ramp and relax phases based on the specific pixel intensity transitions required. Rather than using fixed timing, the system adapts the illumination gap characteristics to match the actual liquid crystal response needs for each frame, optimizing both response time and brightness
2Productivity
If frame rate is increased to improve motion performance, then motion artifacts are reduced, but illumination gaps consume larger percentage of frame time, reducing brightness
Solution Approach 1:
The patent applies parameter changes by modifying the temporal parameters of the drive waveform, specifically the timing of ramp and relax phases relative to the illumination window. By changing these timing parameters dynamically, the system can accommodate higher frame rates while maintaining adequate illumination duty cycle, thus preserving brightness even at elevated frame rates
3Reliability
If standard ramp and relax timing is used, then liquid crystal transitions are achieved, but color errors and motion artifacts occur due to interaction between consecutive color sub-frames
Solution Approach 1:
The patent implements feedback by monitoring the pixel intensity values of consecutive color sub-frames and using this information to adjust the timing of ramp and relax phases. The system feeds back the actual liquid crystal state from previous frames to optimize the current frame's timing, preventing color errors and motion artifacts caused by inter-frame interactions
Solution Approach 2:
The patent applies preliminary action by using the pixel intensity data from the previous color sub-frame to pre-determine the optimal timing for the current sub-frame's ramp and relax phases. This anticipatory timing adjustment prevents color bleed and motion artifacts before they occur, improving color accuracy
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 enhances brightness and reduces motion artifacts by optimizing illumination gaps, ensuring accurate color transitions and minimizing fringe field banding.
Implementation Method 1
driving the liquid crystal material of the pixel with a modulation pulse
Data Source
AI summary
A display driver drives a color sequential liquid crystal display. The display driver obtains pixel intensity data for a pixel of the display, including a first color sub frame (CSF) pixel intensity value and a second CSF pixel intensity value for a second CSF following the first CSF. Selection logic is applied to the pixel intensity data to select a start time for a modulation pulse: for a given second CSF pixel intensity value, in response to a first first CSF pixel intensity value, a first start time is selected from a plurality of predefined potential start times; and in response to a second first CSF pixel intensity value greater than the first first CSF pixel intensity value, a second start time later than the first start time is selected. The liquid crystal material of the pixel is driven with a modulation pulse starting at the selected start time.