Backlight Duty Tone Mapping for Display Contrast
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Solution Overview
Problem
Dynamic backlight control in display devices leads to noticeable contrast loss and visual degradation, particularly in high luminance regions, when trying to save electricity, as existing methods either adjust Gamma correction or scale up luminance, resulting in either limited effectiveness or saturation.
Innovation Solution
A digital image processing method that generates a luminance statistic, determines a specific backlight duty, forms a tone mapping function, and remaps the image using this function to adaptively adjust the backlight and improve contrast, thereby enhancing the visual experience.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the backlight duty is reduced to save electricity, then power consumption is reduced, but contrast and visual quality deteriorate
Solution Approach 1:
The patent applies preliminary action by performing tone mapping on the image data before it is displayed, anticipating the contrast loss that will occur due to reduced backlight duty. The image processing unit adjusts the luminance distribution in advance based on the target backlight duty, so that when the backlight is dimmed, the pre-adjusted image data compensates for the expected contrast degradation, maintaining visual quality while reducing power consumption.
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting the tone mapping parameters based on the target backlight duty. The image processing unit modifies the luminance mapping function parameters according to the desired backlight duty level, transforming the image data to compensate for the reduced illumination. This allows the system to maintain optimal contrast across different power saving modes by changing the processing parameters rather than using a fixed approach.
2Illumination intensity
If Gamma correction factor is adjusted to compensate for contrast loss, then visual effect improves, but effectiveness is limited especially in high luminance regions
Solution Approach 1:
The patent goes beyond simple Gamma correction by implementing full tone mapping with adjustable parameters. Instead of relying solely on the fixed Gamma correction factor, the system uses a configurable tone mapping function that can adaptively adjust multiple parameters including luminance scaling, contrast enhancement, and highlight preservation. This provides more reliable compensation in high luminance regions by offering finer control over the transformation process.
Solution Approach 2:
The patent applies dynamics by making the tone mapping process adaptive rather than static. The image processing unit dynamically adjusts the tone mapping parameters based on the target backlight duty and image characteristics. This dynamic adjustment allows the system to respond to different viewing conditions and image content, providing reliable contrast compensation across varying luminance regions rather than using a fixed Gamma correction approach.
3Illumination intensity
If luminance of the image is scaled up to compensate for illumination loss, then Gamma correction effectiveness improves, but saturation occurs in high luminance portion
Solution Approach 1:
The patent applies parameter changes by using a configurable tone mapping function with multiple adjustable parameters instead of simple luminance scaling. The system can control the strength and characteristics of luminance adjustment through parameters such as the mapping function exponent and scaling factors. This prevents saturation in high luminance portions by allowing fine-tuned adjustment that preserves highlight details while still compensating for reduced backlight illumination.
Solution Approach 2:
The patent applies local quality by implementing tone mapping that can differentially adjust different regions of the luminance range. Rather than uniformly scaling all luminance values, the tone mapping function applies different transformation characteristics to different luminance levels. This allows the system to preserve high luminance details and prevent saturation in bright regions while still providing adequate compensation for dark regions, creating a more balanced and natural-looking image.
Data Source
AI summary
A method and apparatus for processing a digital image to be displayed on a display panel illuminated with a backlight module. The backlight module is set to a specific backlight duty according to a luminance statistic of the digital image. The digital image is remapped through a tone mapping function formed according to the specific backlight duty and the luminance statistic.