Backlight Control Circuit for Display Flicker and Halo Mitigation
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Solution Overview
Problem
Existing backlight control systems for display devices struggle to maintain the desired luminance level of bright but small foreground objects, leading to potential flicker issues when these objects move between zones illuminated by adjacent light sources.
Innovation Solution
The system employs a backlight control circuit that applies a filter to target parts of the input image to generate filtered image parts. It then controls the luminance level of each light source based on the maximum pixel luminance level and the local average picture level (APL) of the filtered image part, using techniques such as boosting and compensation to mitigate flicker and halo effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If local dimming is implemented using an array of light sources to illuminate respective regions of the display panel, then image quality is enhanced through brighter and/or darker portions, but flicker occurs when bright but small foreground objects move between zones illuminated by adjacent light sources
Solution Approach 1:
The patent combines multiple light sources (first light source and second light source) to illuminate a single target zone. When a bright foreground object is detected, both adjacent light sources are activated to ensure continuous illumination as the object moves between zones, eliminating flicker while maintaining local dimming benefits for other regions
Solution Approach 2:
The system performs preliminary detection of bright foreground objects and predicts their movement between zones. By proactively adjusting the illumination of adjacent light sources before the object actually moves between zones, the system prevents flicker from occurring in the first place
2Illumination intensity
If the luminance level of light sources is adjusted based on local APL to enhance image quality, then contrast is improved, but halo effects appear around bright objects
Solution Approach 1:
The patent applies different illumination strategies to different regions: for zones containing bright foreground objects, both adjacent light sources are activated to prevent halos, while for other zones, normal local dimming based on local APL is maintained to preserve contrast. This selective approach addresses halo effects locally without compromising overall image quality
Solution Approach 2:
The system detects bright foreground objects and preemptively adjusts the luminance of adjacent light sources to compensate for potential halo effects. By calculating the required compensation based on the object's position and brightness, the system counteracts the halo effect before it becomes visually apparent
Data Source
AI summary
A display device includes, a backlight device, and a backlight control circuit. The backlight device includes a plurality of light sources configured to illuminate a display panel. The backlight control circuit is configured to apply a filter to a target part of the input image to generate a filtered image part. The target part of the input image is displayed in a corresponding region of the display panel illuminated by a target light source of the plurality of light sources. The backlight control circuit is further configured to control a luminance level of the target light source based on a maximum pixel luminance level of the filtered image part and a local average picture level (APL) of the filtered image part.