Display Device Gray Voltage Generation for Afterimage Reduction
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Solution Overview
Problem
Liquid crystal displays experience afterimages and image degradation due to prolonged electric field application, leading to blurry images and charging deterioration, especially when displaying moving objects over long periods.
Innovation Solution
A display device and method that generate gray voltages using a gray reference voltage, with a controller processing image and control signals to select between first and second gray reference voltages, and apply these voltages to offset afterimages by representing various tones of gray, including black or middle-tone gray, to improve image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If a voltage is applied to the liquid crystal layer for a long period to display images, then the display can maintain image quality, but the liquid crystal molecules experience degradation and afterimages are generated
Solution Approach 1:
The patent applies periodic action by inverting the polarity of data voltages frame by frame. The liquid crystal display inverts the polarity of data voltages with respect to the common voltage for each frame, creating a periodic reversal that prevents the liquid crystal molecules from remaining in a fixed state too long, thereby reducing afterimages and degradation while maintaining continuous display capability
Solution Approach 2:
The patent uses inversion by reversing the polarity of data voltages relative to the common voltage for each frame. This inversion causes the liquid crystal molecules to realign in the opposite direction, effectively resetting their state and preventing cumulative degradation and afterimage effects that would occur with constant polarity application
2Reliability
If the polarity of data voltage is inverted to avoid degradation, then image quality is maintained, but charging time is reduced and afterimages may still occur
Solution Approach 1:
The patent applies preliminary action by generating gray voltages corresponding to insertion grays (such as black or middle-tone gray) before the main image display. These gray voltages are applied during a preliminary period to prepare the liquid crystal molecules for the subsequent image display, ensuring proper charging and alignment while maintaining image quality through the gray reference voltage mechanism
3Reliability
If black is displayed during the rest of the frame time to reduce afterimages, then charging deterioration is reduced, but data reflection and transverse line deterioration are generated
Solution Approach 1:
The patent applies parameter changes by using gray voltages corresponding to insertion grays (such as black or middle-tone gray) instead of pure black. This parameter modification in the voltage level allows the display to maintain charging quality while avoiding the harmful artifacts (data reflection and transverse line deterioration) that occur when displaying pure black, as the gray voltage provides a more favorable electrical state for the liquid crystal molecules
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 effectively reduces afterimages and enhances display quality by actively applying gray voltages corresponding to insertion grays, such as black or middle-tone gray, without reducing charging time, thereby improving the visibility of moving objects and maintaining image clarity over time.
Implementation Method 1
a gray voltage generator to generate a gray reference voltage... dividing the gray reference voltage into a plurality of gray voltages
Implementation Method 2
when a voltage is applied to the two electrodes, an electric field may be generated in the liquid crystal layer. The intensity of the electric field may be adjusted to control the transmittance of light passing through the liquid crystal layer
Implementation Method 3
The control of the liquid crystal molecules may not be properly performed such that afterimages which cause degrading images may be generated
Data Source
AI summary
The present invention relates to a display device and a driving method thereof. A display device according to exemplary embodiments of the present invention includes: a signal controller to process an input image signal and an input control signal to control output of a digital image signal; a gray voltage generator to generate a gray reference voltage; and a data driver to generate gray voltages based on the gray reference voltage from the gray voltage generator, to receive the digital image signal, and to output a portion selected from the generated gray voltages as a data voltage, wherein the gray reference voltage includes a first gray reference voltage for the input image signal and a second gray reference voltage for an insertion gray, and the gray voltage generator generates one of the first gray reference voltage or the second gray reference voltage according to the selection signal included in the control signal to be provided to the data driver.