Liquid Crystal Display Overdrive Control for Brightness Response
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Solution Overview
Problem
In display apparatuses using vertical alignment liquid crystal panels, the response to brightness changes is delayed due to errors in image data compression and decompression, leading to deteriorated image quality, particularly in moving images with extreme brightness changes, as the overdrive control is not appropriately performed when pixel brightness is misidentified.
Innovation Solution
The display apparatus includes a control mechanism that stores image data, reads previous frame data, and adjusts pixel brightness by determining a middle value based on a lookup table, ensuring overdrive control is performed even when pixel brightness is misidentified, by changing the brightness from a previous frame's value to a middle value and then to the intended value, using threshold values to account for compression errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If image data is compressed and stored to save memory, then storage efficiency is improved, but brightness identification accuracy deteriorates due to compression errors
Solution Approach 1:
The patent applies preliminary action by storing a threshold value before brightness comparison, and by performing threshold-based filtering before overdrive control. The threshold value is predetermined based on compression error characteristics, allowing the system to anticipate and compensate for potential misidentification issues before they affect image quality
Solution Approach 2:
The patent introduces a threshold value as an intermediary between the compressed brightness data and the overdrive control decision. This threshold acts as a mediator that filters out false brightness changes caused by compression errors, allowing accurate distinction between real brightness changes and compression artifacts
2Speed
If overdrive control is performed to improve brightness response speed, then response time is reduced, but image quality deteriorates when brightness is misidentified due to compression errors
Solution Approach 1:
The patent implements feedback by comparing the absolute difference between current and previous frame brightness values against a threshold value. This feedback mechanism prevents overdrive control from being applied to brightness changes that are actually compression errors, thereby maintaining image quality while still improving response speed for genuine brightness changes
Solution Approach 2:
The patent changes the parameter comparison criterion from direct brightness value comparison to threshold-based difference comparison. By introducing the threshold parameter and changing how brightness changes are evaluated, the system can distinguish between significant brightness changes requiring overdrive control and minor variations caused by compression errors
3Measurement precision
If threshold value is set low to detect small brightness changes, then detection sensitivity is improved, but false detection of compression errors increases
Solution Approach 1:
The patent applies partial action by not applying overdrive control to all brightness changes, but only to those exceeding the threshold. This selective approach avoids the excessive action of applying overdrive to compression errors while maintaining sensitivity to genuine brightness changes through the appropriately set threshold
4Reliability
If threshold value is set high to filter compression errors, then false detection is reduced, but detection sensitivity to real brightness changes deteriorates
Solution Approach 1:
The patent optimizes the threshold parameter to achieve the best balance between filtering compression errors and detecting real brightness changes. By carefully setting the threshold value based on compression characteristics and display requirements, the system maintains both reliability in error filtering and sensitivity in genuine change detection
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 ensures reliable overdrive control, preventing image quality deterioration in moving images by accurately managing brightness changes, even when pixel brightness is misidentified during compression and decompression, thereby reducing tailing and improving image quality.
Implementation Method 1
a transmission state of light is represented using a refractive index which is changed by applying a voltage to the liquid crystal to bring down the liquid crystal
Data Source
AI summary
During displaying a moving image on a liquid crystal panel, when the brightness of the pixel in an image to be displayed is a prescribed setting value or more, the display apparatus performs the overdrive control for changing the brightness of the pixel from the brightness in one previous image to a middle value between the brightness in the one previous image and the brightness to be displayed, and then changing to the brightness to be displayed. The setting value is, for example, a maximum value of a displayable brightness or a value near the maximum value. If the brightness of the pixel in the one previous image is a first threshold value or less, the display apparatus performs the same overdrive control. Even when the brightness of the pixel in the one previous image is misidentified as other values of the first threshold value or less with a minimum displayable value, the same overdrive control as the case in which the brightness of the one previous image is the minimum value is performed.