What are the technical indicators of gray scale and brightness of LED display?

162 views admin 2024-01-12

The gray level of the LED display is the so-called color level or gray level, which refers to the degree of brightness. For digital display technology, grayscale is the determining factor of display color number. In general, the higher the gray level, the richer the colors displayed, the more delicate the picture, and the easier it is to show rich details.

Advantages of curved LED display

1, effectively reduce space waste. Whether indoors or outdoors, the installation of the LED arc display that fits the outline of the building can effectively reduce space waste and reduce installation costs; 2. Better visual effects. LED arc display is different from the square display, with better visual effects, whether the audience is standing in the center, left or right position, different angles to see the display screen does not deform, coherent high-definition display; 3, better picture display. It can realize the uniform surface change of the display screen, the screen does not drag and black screen, and can achieve smooth display surface; 4. Greater flexibility. Some specific radians can be created to meet the needs of the product and customized according to the needs of customers, which improves the light/dark line problems of the traditional direct Angle and arc products and the problems of side viewing and light inconsistency.

Nonlinear change of gray level

Gray-scale nonlinear transformation refers to transforming gray-scale data according to empirical data or some arithmetic nonlinear relationship and then providing it to the display screen. Because the LED is a linear device, the nonlinear display characteristics are different from those of traditional displays. In order to make the LED display effect conform to the traditional data source without losing the gray level, the nonlinear transformation of the gray level data is generally done after the LED display system, and the number of data bits after the transformation will increase (to ensure that the gray level data is not lost). At present, the so-called 4096 gray level or 16384 gray level or higher of some domestic control system suppliers refers to the size of the gray space after nonlinear transformation. Class 4096 uses the nonlinear transformation technology from 8-bit source to 12-bit space, and class 16384 uses the nonlinear transformation technology from 8-bit to 16-bit. When the 8-bit source is used for nonlinear transformation, the converted space is definitely larger than that of the 8-bit source. It's usually at least 10 digits. Like grayscale, this parameter is not the bigger the better, generally 12 bits can do enough transformation.

Pixel runaway rate

The pixel runaway rate refers to the percentage of the display's smallest imaging unit (pixel) that is not working properly (out of control). The pixel out of control has two modes: one is the blind spot, that is, the blind spot, which is not bright when it needs to be bright, called the blind spot; The second is the usual bright spot, when it needs to be not bright, it has been bright, called the usual bright spot. In general, the composition of the pixel is 2R1G1B (2 red lights, 1 green light and 1 blue light, the same as below), 1R1G1B, 2R1G, 3R6G, etc., and the loss of control is generally not the same pixel in the red, green, and blue lights are all out of control at the same time, but as long as one of the lights is out of control, we believe that the pixel is out of control. For simplicity, we use the statistics and calculation of out-of-control pixels according to the primary colors of the LED display (that is, red, green and blue), and take the maximum value as the pixel out-of-control rate of the display. The ratio of the number 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 avoid the concentration of out-of-control pixels in a certain region, we propose "out-of-control pixel", that is, the ratio of the number of out-of-control pixels to the total number of regional pixels (i.e. 10000) in the 100×100 pixel region. This index quantifies the requirement of "runaway pixels are discrete distribution" in SJ/T11141-2003, which is convenient and intuitive. At present, the domestic LED display will be aging (oven) before leaving the factory, and the LED lights with runaway pixels will be repaired and replaced. It is no problem to control the "whole screen pixel runaway rate" within 1/104, and the "regional pixel runaway rate" within 3/104, and even some individual manufacturers' corporate standards require that runaway pixels are not allowed before leaving the factory. However, this will inevitably increase the manufacturing and maintenance costs of manufacturers and extend the shipment time. In different applications, the actual requirements of the pixel runaway rate can be greatly different, in general, LED display for video playback, indicators required to control within 1/104 is acceptable, but also can be achieved; If it is used for simple character information publishing, it is reasonable to require the indicator to be controlled within 12/104.

Brightness discrimination class

The brightness discrimination level refers to the brightness level of the image that the human eye can distinguish from the blackest to the whitest. As mentioned earlier, the gray level of the display 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 gray may look the same to the human eye. And eye discrimination varies from person to person. For the display screen, the level of human eye recognition is naturally the more the better, because the image displayed 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 discrimination level can be tested with dedicated software, and the general display can reach more than 20 levels.