Backlight Brightness Control for LCD Contrast Ratio
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Solution Overview
Problem
Liquid crystal display (LCD) TVs suffer from a lower contrast ratio due to light leakage, and existing solutions that adjust backlight brightness to improve contrast often cause picture flickering and visual discomfort, as well as reduce the lifespan of the backlight.
Innovation Solution
A method that continuously receives picture signals, calculates the instant relative luminance, and gradually adjusts the backlight brightness to minimum or maximum levels based on predefined ratios and buffer times, while compensating pixel grey values to maintain image vividness and avoid sudden changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the brightness of the back light module is instantly adjusted according to the total luminance of the displayed picture, then the contrast ratio is improved, but picture flickering and visual discomfort occur
Solution Approach 1:
The patent applies dynamics by transitioning from static backlight brightness to dynamic gradual adjustment. The control unit adjusts the backlight module brightness gradually over a preset time period rather than instantly, creating a dynamic transition that eliminates flickering while maintaining contrast ratio improvement. This is achieved through continuous brightness modulation controlled by the control unit based on picture luminance detection.
Solution Approach 2:
The patent changes the parameter of brightness adjustment speed from instant to gradual. By modifying the time parameter (adjusting over preset time period rather than immediately), the system resolves the contradiction between achieving high contrast ratio and avoiding picture flickering. The gradual parameter change ensures smooth transition that prevents visual discomfort.
2Manufacturing precision
If the brightness of the back light module is quickly and frequently adjusted, then the contrast ratio is improved, but the lifetime of the back light module is reduced
Solution Approach 1:
The patent uses dynamic gradual adjustment controlled by the control unit to reduce frequent switching. Instead of quick and frequent brightness changes, the system implements smooth transitions over preset time periods, which reduces stress on the backlight module and extends its operational lifetime while maintaining effective contrast ratio control.
Solution Approach 2:
The patent applies beforehand cushioning by using gradual brightness adjustment as a buffer between high and low luminance states. This cushioning approach prevents abrupt changes that would otherwise cause excessive wear on the backlight module, thereby extending its lifetime while still achieving the desired contrast ratio improvement.
3Manufacturing precision
If the brightness of the back light module is reduced, then the contrast ratio is increased, but the whole picture may look dim
Solution Approach 1:
The patent applies dynamics by implementing gradual brightness reduction rather than abrupt changes. The control unit continuously adjusts the backlight module brightness over a preset time period, creating a smooth transition that maintains overall picture brightness perception while achieving enhanced contrast ratio. This dynamic approach prevents the picture from appearing suddenly dim.
Solution Approach 2:
The patent changes the parameter of brightness adjustment from abrupt to gradual by modifying the time dimension. The preset time period parameter ensures that brightness reduction occurs smoothly, preventing the picture from looking dim while still achieving the desired contrast ratio enhancement through controlled luminance differentiation.
Data Source
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AI summary
A contrast ratio promotion method for a display device (1) is provided. The display device (1) contains a back light module (40) having a brightness and has a maximum luminance. The contrast ratio promotion method comprises the steps of continuously receiving a picture signal during each unit time, continuously calculating a ratio of a luminance of a picture corresponding to the picture signal to the maximum luminance, where the ratio is defined as an instant relative luminance, setting a first ratio (R1), a first buffer time and a first adjusting time, and gradually reducing the brightness of the back light module (40) to a minimum brightness (Imin) during the first adjusting time when a first cumulated time for the respective consecutive plural instant relative luminances being smaller than the first ratio (R1) is longer than the first buffer time.