In order to be able to display a clear picture, the screen needs sufficient brightness, and the unit of brightness is cd/m2. The brightness is proportional to the number of LEDs per unit area and the brightness of the LED itself. The brightness of an LED is proportional to its drive current, but its lifetime is inversely proportional to the square of its current, so the drive current cannot be excessively increased in pursuit of brightness.
The human eye's perception of brightness depends not only on the brightness of the illuminant, but also on the illuminance of the surrounding environment and the intensity of the illuminant itself to the external light. The more scientific expression should be contrast. The definition of contrast is as follows:
Brightness when emitting light (lighting brightness)/Brightness (reflected brightness) when not emitting light
In order to be able to display text and images of uniform brightness, the screen should have sufficient contrast without being affected by ambient light. The brightness when not emitting light is proportional to the ambient light and the screen reflection coefficient, while the contrast is inversely proportional. The higher the contrast, the brighter the screen appears. We deeply understand the effect of contrast on the human eye, so we improve the brightness of the screen. To minimize the light reflection coefficient of the screen surface, the lower the light reflection coefficient of the screen surface material is controlled, and the higher contrast can be ensured when the maximum luminous intensity of the screen is constant. For the control of surface light reflection coefficient, we use special materials and special operation techniques to ensure that the effective light reflection coefficient is not more than 3.5%. In general, the contrast of the screen should be around 10, and the human eye will have a more comfortable feeling.
Since the screen is composed of many pixels, controlling the brightness difference of the pixels is an important issue. The brightness difference of the pixels is measured by the uniformity of the screen.
The display system is a VGA synchronous display system, and the content on the VGA sync, ie, the VGA display, can be displayed on the large screen in a completely synchronous manner. The display screen of this structure is composed of a broadcaster, a control panel, a screen body, etc., and the interconnection relationship is as follows. As shown in the figure, the broadcast machine in the figure is a PC computer, which contains a VGA dedicated graphics card and a capture card.
On the one hand, the broadcaster is responsible for collecting information of the displayed content, and displaying the content to be displayed on the VGA display according to the specific format required by the LED display screen and a certain broadcast order; on the other hand, the screen displayed on the VGA display is collected. The card is sent to the control panel, which is a VGA card used to display the card between the LED screens. Through the card, the data on the VGA display is transmitted to the display screen in real time at a certain rate, the control board receives the signal from the acquisition card, and automatically distributes the information to each unit board of the LED display screen, thereby completing the display screen. The various signals required make the LED display body show a vivid and dynamic picture. The screen body is the LED final display unit, which is composed of an LED display module frame, a power supply, and various signal connections.