Backlight Control for LCD Trail-Leaving Reduction
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Solution Overview
Problem
Liquid crystal display devices face issues with contrast degradation and trail-leaving phenomena when displaying moving images due to varying liquid crystal response times and backlight timing inconsistencies, especially at different gray levels.
Innovation Solution
A liquid crystal display device with a driving control unit that adjusts backlight timing and duty cycle based on the response of the liquid crystal to applied gray level voltages, ensuring the backlight is turned off until the liquid crystal responds and then turned on at the brightest gray level, with flashing duty corresponding to the gray level ratio, to synchronize the backlight with the video signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the backlight is turned ON in every frame period to improve contrast and dynamic range, then contrast and dynamic range are improved, but trail-leaving phenomenon occurs when liquid crystal response is slow at low gray levels
Solution Approach 1:
The backlight lighting timing is made dynamic by adjusting it according to the liquid crystal response time, which varies with gray level. The system transitions from a static backlight control approach to a dynamic one where the backlight timing adapts to the liquid crystal's response characteristics at different gray levels, thereby maintaining consistent image quality across all gray levels.
Solution Approach 2:
The invention changes the backlight lighting timing parameter based on the gray level of the video signal. By detecting the gray level and adjusting the backlight timing accordingly, the system optimizes the backlight operation to match the liquid crystal response at each gray level, preventing trail-leaving while maintaining contrast.
2Reliability
If the backlight lighting timing is adjusted to match liquid crystal response at high gray levels, then trail-leving is reduced, but contrast degradation occurs at low gray levels where liquid crystal response is slow
Solution Approach 1:
The invention applies different backlight timing strategies for different gray levels. Instead of using a uniform backlight timing for all gray levels, the system adjusts the backlight timing locally according to the specific gray level being displayed, ensuring optimal performance for each gray level range.
Solution Approach 2:
The system uses feedback from the liquid crystal response characteristics to adjust the backlight timing. By monitoring how the liquid crystal responds at different gray levels and using this information to control the backlight timing, the system achieves coordinated operation between the liquid crystal and backlight.
3Use of energy by moving object
If holding-type driving operation is used to maintain current frame until next video signal, then power consumption is reduced, but trail-leaving phenomenon occurs due to slow liquid crystal response
Solution Approach 1:
The invention introduces periodic backlight flashing during the holding period. Instead of continuously illuminating the backlight or keeping it completely off, the system uses periodic backlight activation to refresh the display during the hold period, preventing trail-leaving while maintaining power efficiency.
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 solution reduces trail-leaving and improves contrast and dynamic range of luminance, maintaining image quality even at varying gray levels by synchronizing backlight operation with the liquid crystal response.
Implementation Method 1
a response of a liquid crystal is controlled in the pixel region according to the applied gray level voltage
Implementation Method 2
a backlight; wherein the backlight illuminates the liquid crystal display panel from its rear side
Data Source
AI summary
A liquid crystal display device capable of improving quality of moving images is provided. Each LED (Light Emitting Diode) block is turned ON according to a response of a liquid crystal corresponding to a light emitting region and the brightest gray level is detected for each of red (R), green (G) and blue (B) of an input video signal in every frame period and an input video signal is converted into a value obtained by being multiplied by an upper limit gray level and then by being divided by the brightest gray level and a gray level voltage corresponding to the converted value is applied to each data electrode and, during a lighting period of LED blocks, each LED block is made to flash at a duty corresponding to a rate of the brightest gray level to the upper limit gray level.