LCD Subarea Backlight Control for Dynamic Contrast
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Solution Overview
Problem
Existing liquid crystal display (LCD) technologies face limitations in improving picture contrast due to the inability of global backlight modulation to accurately reflect brightness details between local images, leading to suboptimal contrast quality-of-picture effects.
Innovation Solution
The method involves dividing the LCD into subareas and determining image grayscale values for each subarea, applying a preset backlight value gain coefficient, and adjusting backlight values using a subarea backlight value adjustment coefficient to enhance peak brightness and control brightness in each subarea, thereby improving contrast.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If global backlight modulation is used to control overall brightness, then energy saving is achieved, but the ability to accurately reflect local brightness details is lost
Solution Approach 1:
The display screen is divided into multiple local backlight subareas, each with independent backlight units and control circuits. This segmentation enables localized brightness control while maintaining overall energy efficiency, resolving the contradiction between global energy saving and local brightness accuracy.
Solution Approach 2:
Different backlight subareas are assigned different brightness characteristics based on local image content requirements. The system applies local quality control by adjusting brightness in specific regions rather than uniformly across the entire display, achieving both energy efficiency and brightness detail accuracy.
2Measurement precision
If subarea backlight control is implemented to improve local brightness accuracy, then picture contrast is enhanced, but device complexity increases
Solution Approach 1:
Multiple backlight units are merged into a unified backlight assembly with coordinated control. The control system integrates subarea backlight values into a cohesive driving strategy, reducing the perceived complexity while maintaining local brightness control capabilities.
Solution Approach 2:
The backlight control system is designed to perform multiple functions: global brightness regulation, local contrast enhancement, and energy management. This multi-functionality reduces the need for separate control mechanisms, thereby managing device complexity while achieving superior brightness control.
3Illumination intensity
If backlight brightness is increased to improve peak brightness, then picture contrast improves, but energy consumption increases
Solution Approach 1:
The backlight system employs periodic pulse-width modulation (PWM) to control brightness. By using periodic on/off cycles with variable duty cycles, the system achieves different brightness levels without proportionally increasing energy consumption, resolving the contradiction between peak brightness and energy use.
Solution Approach 2:
The system dynamically changes backlight driving parameters such as current magnitude and pulse width based on local image content requirements. This allows peak brightness to be increased only when and where necessary, rather than maintaining high brightness continuously, thereby reducing overall energy consumption.
Data Source
AI summary
An apparatus for controlling liquid crystal display brightness includes: a subarea image grayscale determining section configured to determine image grayscale values of subarea image data blocks corresponding to backlight subareas according to a received image signal; a subarea backlight value pre-obtaining section configured to pre-obtain subarea backlight values corresponding to the subarea image data blocks according to the image grayscale values of the subarea image data blocks; a subarea backlight value gain section configured to multiply the pre-obtained subarea backlight values with a preset backlight value gain coefficient to obtain gained backlight values of the backlight subareas, wherein the preset backlight value gain coefficient is more than 1; a subarea backlight value adjusting section configured to obtain a subarea backlight value adjustment coefficient, and to further multiply the gained subarea backlight values with the corresponding backlight value adjustment coefficient to obtain adjusted subarea backlight values, wherein if the pre-obtained subarea backlight value or the gained subarea backlight value is below a first threshold, then the corresponding backlight value adjustment coefficient is less than 1; and a subarea backlight value outputting section configured to output the respective adjusted subarea backlight values to driver circuits of backlight sources in the corresponding backlight subareas to control the brightness of the backlight sources in the corresponding backlight subareas as a result of driving.