Introduction to LED backlight TV area dimming technology
Energy-saving and image quality improvement technology has always been the field of continuous pursuit of innovation in the color TV industry. With the popularity of LCD TVs, regional dimming technology has become one of the best technologies for energy saving and image quality enhancement.
The traditional CRT TV is a flat light source, and its illumination is either illuminated by the whole piece or the whole piece is darkened, and it is impossible to dim the picture according to the picture. The LCD TV display part mainly includes a backlight and a liquid crystal display unit, wherein the backlight mainly adopts a linear light source CCFL and a point light source LED , which provides a possibility for realizing regional dimming. The backlight of the LCD TV is the most energy-consuming part of the whole machine. Therefore, the technology of adjusting the backlight brightness in various ways to achieve energy saving and improving the image quality has been a difficult problem in the industry.
At the beginning of the LCD TV, the backlight brightness is fixed or manually adjusted by the user through the menu, which is similar to the CRT's planar light source, either the whole piece is brightened or the whole piece is darkened. CCFL is a linear light source, so the partition adjustment is technically feasible. As LCD TVs gradually occupy the mainstream of the market, the backlight brightness area adjustment technology has also developed rapidly. After 0-dimensional (0D) Dimming, 1st dimension (1D) Dimming Developed to the current 2nd dimension (2D) Dimming.
Backlight area adjustment technology
LCD TV backlight area adjustment technology, that is, Local dimming technology, refers to the LCD TV system divides the image signal into several areas, and analyzes and calculates the image brightness according to each area, and then automatically controls the brightness and darkness of the backlights in each area.
0D Dimming: refers to the LCD TV system to adjust the brightness of the entire TV screen. Whether it is CCFL backlight or LED backlight , all CCFL tubes or LEDs have the same brightness under the same screen, which is controlled by the system. When darkened or brightened, the system automatically dims or brightens the backlight. The general algorithm is to calculate the average brightness of the entire picture by software, and adjust the backlight brightness according to the average brightness. For example, when the black screen (as shown in Figure 1.1), the CPU automatically adjusts the backlight brightness to the darkest, and when the white screen (Figure 1.2), the CPU automatically adjusts the backlight brightness to the brightest. The disadvantage of 0D Dimming is that the unified adjustment is not accurate enough. For example, when pure white and pure black images appear in the same picture (as shown in Figure 1.3, the black and white pictures are displayed), the system CPU calculates the average brightness and adjusts the backlight brightness to the middle. This will result in a place where pure white is not bright enough, while a place that is pure black is not black enough. So strictly speaking, 0D Dimming does not count regional dimming.
Figure 1. Several different brightness display screens may appear on the TV.
1D Dimming: English is also called line dimming. As the name implies, it is adjusted according to the line. For CCFL backlights, it will be adjusted for each lamp, or the total number of lamps will be grouped into groups according to adjacent lamps; for direct-lit LEDs, it will be adjusted for each row of LEDs, or The adjacent row LEDs are individually adjusted in groups. As shown in Figure 1.3, the CPU calculates the average brightness of each area by area. It can dim or turn off the upper or lower part of the tube or LED, and adjust the middle tube or LED to the brightest. 1D Dimming has greatly improved the technology than 0D Dimming, so as to adjust the brightness of the backlight can greatly reduce the energy consumption of the LCD TV and improve the contrast of the screen. However, when it encounters a picture with black and white interlaced in the same line as shown in Fig. 1.4, the brightness adjustment of the same line will be inaccurate.
2D Dimming: Local dimming refers to dividing the whole picture into several areas in a matrix. The CPU calculates the average brightness according to the distribution of each area, and independently controls the brightness of each area, so that it can be perfectly solved as shown in Figure 1.4 in 1D Dimming. The problem that arises.
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