• 목록
• 게시판 리스트 옵션
  • 수정
  • 삭제

At present, domestic LED displays will be aging (baking machine) before leaving the factory, and the LED lights of out-of-control pixels will be repaired and replaced. There is no problem within 3/104, and even some individual manufacturers' corporate standards require that out-of-control pixels are not allowed before leaving the factory, but this will inevitably increase the manufacturer's manufacturing and maintenance costs and prolong the delivery time. In different applications, the actual requirements for the pixel out-of-control rate can be quite different. Generally speaking, LED displays are used for video playback, and the index requirements are acceptable and achievable to be controlled within 1/104; If it is used for the release of simple character information, it is reasonable to control the index requirement within 12/104.

Brightness Discrimination Level

The brightness discrimination level refers to the brightness level of the image from the darkest to the whitest that the human eye can distinguish. As mentioned earlier, the gray scale of the display screen is very high, which can reach 256 or even 1024 levels. However, due to the limited sensitivity of the human eye to brightness, these gray levels cannot be fully recognized. That is to say, many adjacent levels of grayscale may look the same to human eyes. And the ability of eyes to distinguish varies from person to person. For the display screen, the higher the level of human eye recognition, the better, because the displayed image is for people to see after all. The more brightness levels the human eye can distinguish, the larger the color space of the display and the greater the potential for displaying rich colors. The brightness identification level can be tested with special software. Generally, the display screen can reach level 20 or above, which is considered a relatively good level.

Pixel out of control rate

The pixel out of control rate refers to the proportion of the smallest imaging unit (pixel) of the display screen that is not working properly (out of control). There are two modes of pixel out of control: one is blind spot, that is, blind spot, it does not light up when it needs to be bright, which is called blind spot; the other is constant bright spot, it is always on when it needs not to be bright, Call it a constant bright spot. Generally, the composition of pixels is 2R1G1B (2 red lights, 1 green light and 1 blue light, the same as below), 1R1G1B, 2R1G, 3R6G, etc., and out of control is generally not the red, red, and blue lights in the same pixel. Both the green and blue lights are out of control at the same time, but as long as one of the lights is out of control, we consider that pixel out of control. For the sake of simplicity, we count and calculate the out-of-control pixels according to the primary colors (ie red, green, blue) of the LED display, and take the maximum value as the pixel out-of-control rate of the display.

The ratio of out-of-control pixels to the total number of full-screen pixels is called the "full-screen pixel out-of-control rate". In addition, in order to prevent out-of-control pixels from concentrating in a certain area, we propose "area pixel out-of-control rate", which is the ratio of the number of out-of-control pixels to the total number of area pixels (ie 10,000) in a 100×100 pixel area. This indicator quantifies the requirement of "out-of-control pixels are discretely distributed" in "General Specifications for LED Displays" SJ/T11141-2003, which is convenient and intuitive.

Gray scale is the so-called color scale or gray scale, which refers to the lightness and darkness of brightness. For digital display technology, grayscale is the determining factor for the number of displayed colors. Generally speaking, the higher the grayscale, the richer the displayed colors, the more delicate the picture, and the easier it is to express rich details.

The gray level mainly depends on the A/D conversion bits of the system. Of course, the system's video processing chip, memory and transmission system must provide the corresponding number of support. At present, the domestic outdoor led video panel display mainly adopts an 8-bit processing system, that is, 256 (28) gray levels. A simple understanding is that there are 256 brightness changes from black to white. Using RGB three primary colors can form 256×256×256=16777216 kinds of colors. That is commonly referred to as 16 million colors. The display screens of international brands mainly adopt a 10-bit processing system, that is, 1024 levels of grayscale, and the three primary colors of RGB can form 1.07 billion colors.

Although the grayscale is the decisive factor in determining the number of colors, it does not mean that the bigger the unlimited, the better. Firstly, the resolution of the human eye is limited, and the increase in the number of system processing digits will involve changes in various aspects of the system, such as video processing, storage, transmission, scanning, etc., the cost increases sharply, and the cost performance decreases. Generally speaking, civil or commercial products can use 8-bit system, and broadcast-level products can use 10-bit system.

Gray scale non-linear transformation

Gray-scale nonlinear transformation refers to transforming gray-scale data according to empirical data or a certain arithmetic nonlinear relationship and then providing it to the display screen for display. Since LED is a linear device, it is different from the non-linear display characteristics of traditional displays. In order to make the LED display effect conform to the traditional data source without losing the gray level, generally, the gray level data will be transformed non-linearly after the LED display system, and the number of transformed data will increase (to ensure that the gray level is not lost. data). The so-called 4096-level grayscale or 16384-level grayscale or higher by some domestic control system suppliers refers to the size of the grayscale space after nonlinear transformation. Level 4096 adopts the non-linear transformation technology from 8-bit source to 12-bit space, and level 16384 adopts the non-linear transformation technology from 8-bit to 16-bit. The non-linear transformation is done by the 8-bit source, and the converted space must be larger than that of the 8-bit source. Generally at least 10 digits. Just like the grayscale, this parameter is not as big as possible, generally 12 bits can do enough transformation.