The Relationship Between Grayscale and Brightness of the LED Display
To know the relationship between grayscale and brightness of the led display, we need to know what is the led display grayscale and led display brightness first.
The gray level of the LED display can also be called the brightness of the LED display. Gray level is also called midline. It is mainly used to transfer pictures. There are 16 levels, 32 levels, and 64 levels. It uses matrix processing to process the pixels of the file into 16, 32, and 64 levels. The picture is clearer. Whether it is monochrome, two colors, full color LED display, to display an image or animation, it is necessary to adjust the illuminance of each LED constituting the pixel, and the degree of fineness of the adjustment is what we usually call the graduation.
There are two ways to control the gray level of the LED display: one is to change the current flowing, and the other is pulse width modulation. 1. Change the current flowing through the LED. Generally, the LED tube allows the continuous working current to be around 20 mA. In addition to the saturation of the red LED, the other LED grayscale is basically proportional to the current flowing through; the other method is to use the visual inertia of the human eye, using the pulse width The modulation method is used to implement gray scale control, that is, to periodically change the width of the light pulse, as long as the period of repeated lighting is short enough, the human eye does not feel that the illuminating pixel is shaking.
Since pulse width modulation is more suitable for digital control, in today's widespread use of microcomputers to provide LED display content, almost all LED displays use pulse width modulation to control gray levels.
The LED control system usually consists of three main parts: the main control box, the scanning board, and the display control unit. The main control box obtains the brightness data of each layer of pixels from the display card of the computer, and then re-allocates the data to a plurality of scanning boards, each of which is responsible for controlling several rows (columns) on the LED display, and each row (column) The display control signal of the upper LED is transmitted in serial mode. There are currently two ways to serially transmit display control signals.
One is to control the gray level of each pixel point on the scanning board, the scanning board decomposes the gray value of each row of pixels from the control box, and then serially turns the turn-on signals of each row of LEDs in a pulse form. Transfer to the corresponding LED to control whether it is lit. This method uses fewer devices, but the amount of data transmitted serially is larger because each pixel requires 16 pulses at 16 levels of gray during a repeated lighting period, requiring 256 levels of gray. 256 pulses, due to the device operating frequency limit, generally only enable the LED display to achieve 16 gray levels.
Second, one is pulse width modulation. The serial transmission of the scan board is not the switching signal of each LED but an 8-bit binary gray value. Each LED has its own pulse width modulator to control the lighting time. Thus, in a period of repeated lighting, each pixel point requires only 4 pulses in 16-level grayscale, and only 8 pulses in 256-level grayscale, which greatly reduces the serial transmission frequency. With this method of controlling the gradation of the LED, it is convenient to implement 256-level gradation control.
LED display grayscale and LED display brightness is one of the important parameters of the product. In order to better use the LED display, it is necessary to understand The Relationship Between Grayscale and Brightness of the LED Display.
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