Liquid Crystal Display Local Dimming Control Method
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Solution Overview
Problem
The existing local dimming techniques for liquid crystal displays suffer from gray level saturation and increased 3D crosstalk when applied to 3D images, as they calculate pixel gain values based on dimming values from previous frames, which are not suitable for the low correlation between adjacent frames in 3D mode, leading to reduced display quality.
Innovation Solution
A liquid crystal display system that calculates pixel gain values based on dimming values of each block in a first frame and applies them to data compensation for a later frame, with the timing of application adjusted according to the 2D or 3D mode signal, allowing for delayed pixel gain value calculation in 3D mode to account for the low correlation between frames.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pixel gain values are calculated based on dimming values from previous frames using related art local dimming technique, then data compensation can be performed for the next frame, but gray level saturation and 3D crosstalk occur in 3D mode due to low correlation between adjacent frames
Solution Approach 1:
The patent applies dynamics by making the pixel gain value calculation adaptive to different display modes. In 2D mode, pixel gain values are calculated based on previous frame dimming values, while in 3D mode, the calculation is based on current frame dimming values. This dynamic adjustment of the calculation basis according to mode requirements resolves the gray level saturation and crosstalk issues.
Solution Approach 2:
The patent changes the parameter used for pixel gain value calculation based on display mode. Specifically, it switches between using previous frame dimming values (for 2D mode) and current frame dimming values (for 3D mode). This parameter change ensures accurate luminance compensation without causing gray level saturation or 3D crosstalk.
2Illumination intensity
If local dimming is applied to improve contrast ratio and reduce power consumption, then luminance can be locally controlled, but pixel data modulation becomes complex requiring precise pixel gain value calculation
Solution Approach 1:
The patent performs preliminary calculation of pixel gain values based on dimming values before applying data compensation. By pre-calculating the gain values required for luminance compensation, the system simplifies the subsequent pixel data modulation process while maintaining accurate local luminance control.
Solution Approach 2:
The patent uses feedback from dimming value analysis to calculate appropriate pixel gain values. The system analyzes the dimming values of backlight units, calculates the corresponding pixel gain values, and applies these to modulate pixel data, creating a closed-loop control system that achieves accurate luminance compensation.
3Reliability
If black frames are inserted in LBRB method for 3D display, then image tailing is reduced, but the correlation between adjacent frames decreases making previous frame based compensation inaccurate
Solution Approach 1:
The patent dynamically adjusts the basis for pixel gain value calculation based on display mode. In 3D mode with LBRB method, it uses current frame dimming values instead of previous frame values, adapting to the reduced frame correlation caused by black frame insertion while maintaining accurate luminance compensation.
Data Source
AI summary
A liquid crystal display and a local dimming control method thereof are discussed. The liquid crystal display includes a liquid crystal display panel selectively displaying a 2D image and a 3D image in response to a mode signal, a backlight unit including a plurality of light sources, a backlight driving circuit individually driving a plurality of previously determined blocks each including the light sources based on a dimming value of each block, and a local dimming control circuit, that calculates a pixel gain value based on a dimming value of each block in a first frame, applies the pixel gain value to a data compensation for a second frame, which is arranged later than the first frame, and varies a time point when the pixel gain value for the data compensation is applied in response to the mode signal.