LCD Backlight Dimming with Tone Mapping Compensation
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Solution Overview
Problem
Existing LCD technologies face challenges in reducing power consumption while maintaining perceived image brightness during backlight dimming, as previous methods often result in unintended dimming of the displayed image due to inadequate compensation for backlight intensity variations.
Innovation Solution
A method involving dimming the backlight by a determined factor and adjusting pixel intensity distribution using tone mapping functions, with a Clipping Point-based dimming factor and separate tone mapping algorithms for intensities below and above a Fidelity Point to maintain image brightness, ensuring lower power consumption without compromising visual quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If the backlight is dimmed to reduce power consumption, then power consumption is reduced, but the perceived brightness of the displayed image decreases
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the backlight intensity level based on the content type and scene brightness. The system changes the backlight dimming factor as a variable parameter rather than using a fixed level, allowing optimization between power consumption and perceived brightness for different viewing conditions.
Solution Approach 2:
The patent implements feedback mechanisms where the system monitors and adjusts backlight intensity based on detected image characteristics. The backlight control is fed back with image analysis data to automatically optimize the dimming factor, ensuring minimal power consumption while maintaining acceptable perceived brightness.
2Use of energy by stationary object
If simple expansion of LCD transmittance is used to compensate for backlight dimming, then power consumption is reduced, but high brightness values are truncated resulting in loss of image quality
Solution Approach 1:
The patent segments the image intensity range into different zones (low, mid, and high brightness regions) and applies different compensation strategies to each segment. This allows selective expansion of transmittance values in the critical mid-range while preserving high brightness values, preventing truncation and maintaining image quality.
Solution Approach 2:
The patent applies local quality by treating different intensity ranges of the image signal differently. Instead of uniform expansion, the system applies localized compensation only where needed, preserving the original high brightness values while adjusting mid-range values to compensate for backlight dimming, thus maintaining overall image quality.
Data Source
AI summary
A method of reducing power consumption in a liquid crystal display illuminated by a backlight device includes dimming the backlight and adjusting the intensity of the image to compensate for the dimmed backlight. A dimming factor for the backlight is based on a clipping point determining from the pixel intensity distribution of the image signal. The intensity of the image is adjusted based on the dimming factor, wherein a first tone mapping function is used to adjust pixel intensities below an intensity threshold and a second tone mapping function is used to adjust pixel intensities above the intensity threshold.