What‘s the Relationship Between the Grayscale and Brightness of the LED Display Screen
LED grayscale can also be called LED brightness. The grayscale is also known as half-tone, and is mainly used to transmit pictures. There are 16, 32 and 64 respectively, and it USES matrix processing to process the pixels of the files into 16, 32, and 64 levels, making the transmitted images clearer. Whether it is monochrome, two-color, three color screen, to display the image or animation needs to be adjusted to constitute each LED pixel gray level, the control of fine degree is what we usually call to grayscale.
There are two ways to control LED grayscale: one is to change the flow of current, one is pulse width modulation.
Change the current flowing through the LED. The normal LED tube permits continuous working current at about 20 mah, except that the red LED has saturation, and the other LED gray is basically proportional to the current flowing through it.
Another method is to use human eye visual inertia, using pulse width modulation method to realize gray scale control, which is periodic change light pulse width (duty cycle), as long as the repetition of the light cycle is short enough (that is, the refresh rate is high enough), the human eye is feeling less than glowing pixels in jitter.
Since pulse width modulation is more suitable for digital control, it is generally used for the display content of LED display by microcomputer. Almost all the LED screens are equipped with pulse width modulation to control the gray levels. The control system of LED usually consists of the main control box, the scanning plate and the display device.
The main box from computer display card to get a screen pixel brightness of all kinds of data, and then reassigned to a number of scanning board, scanning each one is responsible for the control of the LED screen number of row (column), and each row (column) on the LED display control signal is transmitted in serial mode.
There are two kinds of serial transmission display control signals:
1. Centralized control of the grayscale of pixels on the scanning board.
Scanning board will come from the control box of each pixel gray value decomposition (pulse width modulation), then all LED to the opening of the signal pulse form (0) light is 1, dawn line by way of serial transmission to the corresponding LED on, whether to control its light. This way using the device is less, but the serial transmission data volume is bigger, because in a repeated cycle of light, each pixel under the gray level 16 needs 16 pulse, under the gray level 256 to 256 pulses, because the device operating frequency restricted, normally only the LED screen be gray level 16.
2. Pulse width modulation.
The content of the scan board serial transmission 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. In this way, in a cycle of repeated lighting, each pixel requires only four pulses at the level of 16 gray degrees, and only eight pulses are needed at the 256 level grayscale, greatly reducing the serial transmission frequency. The method of dispersing LED grayscale with this kind of dispersion can easily realize the 256 level grayscale control.