Backlight Dimming via Pixel Histogram Clipping for LCD Power Reduction
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Solution Overview
Problem
The global dimming method for LCDs faces limitations in expressing gray levels due to highest gray level saturation, leading to image quality deterioration and increased power consumption, as it clips pixel data without accurately estimating the annoyance level of clipping artifacts.
Innovation Solution
A data clipping method that generates a filtered accumulated distribution of pixel counts at each grayscale level, adjusts the frame gain based on a threshold, and clips pixel data above the threshold to reduce power consumption while minimizing image quality deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If pixel data is clipped to control backlight brightness, then power consumption is reduced, but image quality deteriorates due to gray level saturation
Solution Approach 1:
The patent applies preliminary action by pre-calculating the frame gain value based on the histogram distribution of pixel data before backlight dimming. The frame gain is determined by analyzing the accumulated distribution of pixel values and identifying the threshold where clipping begins. This pre-computation allows the system to optimally scale pixel data to maximize backlight reduction while minimizing visible clipping artifacts, thus resolving the contradiction between power consumption reduction and image quality preservation.
2Illumination intensity
If the highest gray level is increased to compensate for reduced backlight brightness, then image brightness is maintained, but the gray level saturation limitation prevents appropriate expression
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the frame gain parameter based on the statistical distribution of pixel data in the image. Instead of using a fixed gray level mapping, the system calculates the frame gain as the ratio of maximum gray level to a threshold value derived from the histogram (frameMax). This adaptive parameter adjustment allows the system to maintain display brightness while accurately representing gray levels by scaling the entire pixel value range according to the actual image content distribution.
3Use of energy by stationary object
If pixel data is clipped at a predetermined clipping rate, then backlight brightness control is achieved, but clipping artifacts increase and deteriorate image quality
Solution Approach 1:
The patent applies feedback by using the histogram distribution of pixel data to dynamically determine the frame gain value. The system analyzes the accumulated distribution of pixel values, identifies the frameMax threshold where clipping begins, and adjusts the frame gain accordingly. This feedback mechanism ensures that the clipping rate is optimized for each specific image content, minimizing visible clipping artifacts while achieving the desired backlight brightness reduction. The frame gain calculation incorporates information about the actual pixel value distribution, creating a closed-loop system that adapts to different image characteristics.
Data Source
AI summary
The present disclosure provides method and device for dimming the backlight of an LCD. A number of pixels at each grayscale level of an input image is determined. The determined number of pixels at each grayscale level is accumulated to generate an accumulated distribution of the number of pixel and the accumulated distribution is filtered. A threshold grayscale level at which the filtered accumulated distribution exceeds a threshold value is determined. A scaling factor is determined based on the threshold grayscale level. The grayscale level of pixels of the input image having a grayscale level lower than or equal to the threshold grayscale level are up-scaled based on the scaling factor, the grayscale value of pixels of the input image having a grayscale level greater than the threshold grayscale level are set to have a predetermined clipping grayscale level, and the LCD backlight is dimmed based on the scaling factor.