Backlight Control for High Dynamic Range LCD Detail Preservation
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Solution Overview
Problem
Conventional high dynamic range LCD backlight control methods cause image distortion, particularly in detailed parts, due to simplistic methods of determining backlight brightness based on average gray levels or their square roots.
Innovation Solution
A method that determines the gray level histogram of an image, accumulates it to obtain a cumulative function, and maps this function to a standard line to derive a backlight modulation function, which is used to adjust backlight brightness in different regions, enhancing image detail preservation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If backlight brightness is reduced to increase contrast, then dynamic range is improved, but image distortion occurs
Solution Approach 1:
The patent applies local quality by determining backlight brightness independently for different regions of the display based on the histogram distribution of gray levels in each region. Instead of uniformly reducing backlight brightness across the entire display, the system adjusts brightness locally in each region according to its specific image content characteristics, thereby maintaining contrast enhancement while preventing image distortion in detailed areas
Solution Approach 2:
The patent performs preliminary action by computing the histogram of gray levels and deriving the cumulative distribution function before actually controlling the backlight brightness. This pre-processing step allows the system to predict the appropriate backlight modulation function that will achieve the desired contrast enhancement without causing distortion, by mapping the cumulative histogram to a standard line in advance
2Ease of operation
If average gray level method is used to determine backlight brightness, then control simplicity is maintained, but image distortion occurs in detailed parts
Solution Approach 1:
The patent transforms the simple average gray level parameter into a more sophisticated backlight control parameter by computing the cumulative distribution function from the histogram and mapping it to a standard line. This parameter transformation maintains the computational simplicity of using a single value per region while dramatically improving image quality by accounting for the full distribution of gray levels rather than just their average
Solution Approach 2:
The patent introduces the cumulative distribution function as an intermediary between the simple average gray level measurement and the final backlight brightness control. This intermediary function captures the distribution characteristics of gray levels and translates them into an optimized backlight modulation function, thereby preserving image details while maintaining ease of control
Data Source
AI summary
A cumulative function of image is obtained according to its gray levels of pixels. This function is then mapped to obtain a backlight modulation function according to a reference line. The backlight brightness provided for different regions of the liquid crystal display are decided by the backlight modulation function while displaying the images.