Real pixel sign refers to the display screen of which each LED in a RGB pixel participates in one imaging pixel only in order to have enough brightness for displaying.

Virtual pixel sign refers to the display screen of which each LED in one color/color group participates in all the adjacent imaging pixels, through calculation by software, in order to increase the resolution for displaying. Usually resolution of a virtual sign can be four times higher than a real pixel sign.

 

Static sign refers to a sign, when displaying messages, graphics or video, all the LEDs in imaging pixels are lightened at the same time. While a scan sign, taking advantage of human visual feature—transient retention of images, displays materials by quickly lighting the pixels line by line. As we all know, an LED sign works by image formation through different percentage of LEDs being lighted and brightness of a sign relates much to the time period each LED is lighted. That’s why a static sign is much brighter than a scan sign on condition that the luminous intensity of LEDs is the same.

Static signs are often used outdoors where high brightness of the sign is required and a scan sign is often used indoors so that the cost can be lowered.

 

Linear virtual technique for led display is a patented know-how, developed for the purpose of using fewer LEDs to make signs with the same resolution. On basis of calculation by software, the technique makes max use of LEDs on a sign and controls the lumination of LEDs at different time points. Under the condition of same pixels, a virtual sign can display four times more of materials. Of course, virtual technique will reduce to some extent the overall brightness of a sign. For solving the problem, the advanced display controlling system must be used. For instance, Zhongkey controlling system, using specialized controlling-chips and chips of constant current to optimize the calculation so that the lose of brightness can hardly be detectable by naked eyes.

 

An LED sign must have higher gray scales in order to effectively display videos as shown by many signs produced home and abroad. At present, a high quality LED sign will have 1024 gray scales to display 10.7million of different colors. In China, most part of the led signs is of 256 gray scales. Some manufacturers may think that 256 gray scales are enough for an LED sign since color TV sets have 256 gray scales also. But actually the display result is very different. To upgrade an LED sign from 256 gray scales to 1024 gray scales, it requires quite some technology to realize it.

 

So far LED display has been widely used in many different areas. In stadium, LED signs are widely used for live show of games, for messages announcement and score records; in financial area, LED signs are employed for stocks prices, exchange rates and interest posting; in retail and postal sectors, led signs are for advertisement and message announcing. They can also be used in agricultural and industrial sectors, hospitals, military, public security and traffic areas. LED signs play more and more important roles in our lives.

 

An LED display system can divided into several categories in accordance with different criteria. In terms of ambient condition, it can be divided into outdoor display and indoor display. In terms of color display, it can be monochromic, duel-basic-color and full-color signs. In terms of gray scales, it can be 16, 32, 64, 128, 256 and 1024 gray scales of signs. In way of display functions, it can be video signs, message and graphic signs, traffic-directional signs and financial information signs.

 

An indoor display and an outdoor display are quite different from each other in several ways. First, an indoor display is much lower in brightness than an outdoor display. For an outdoor sign, super bright LEDs must be used in order to achieve overall brightness. Second, an outdoor display must be weatherproof, safe from rain, sunshine, dust, and wind. An indoor display does not have such problems.

 

The pixel pitch is the distance between the central points of two adjacent pixels. The closer the pixels are or smaller the pitch is, the higher the density of a display is and of course the cost will become higher accordingly. The pixel pitch also relates to the diameter of a pixel. The smaller the diameter, the smaller the pitch becomes.

 

The resolution of an LED display refers to the horizontal and vertical lines of pixels. When the size of an LED sign is the same, the higher the resolution, the clearer the displayed pictures become.

 

An LED display screen works in two different ways: working with a computer synchronously which is also called the full functional display or working independently. They have the same look and have the same display functions but are different in the follows ways:

A.      An off-line display has a set-in mini-device which has memory and can display what is stored when it is disconnected from a computer. If display materials are to be changed, a memory card will do the job or connect it to a computer with RS232 cable to make any changes. But an on-line display must work with a computer synchronously.

B.      An off-line display is lower in cost and simple in operation, usually used for displaying materials that will not be changed frequently. An on-line display is higher in cost and requires a hand for operation but you have total flexibility for what will be displayed any time.

 

The luminous intensity of LEDs can be derived by the following calculation (Suppose one pixel is of 2 red, 1green and 1blue LED):

Intensity of red LED = brightness/m²÷pixels/m² x 0.3÷2

Intensity of green LED = brightness/m²÷pixels/m² x 0.6

Intensity of blue LED = brightness/m²÷pixels/m² x 0.1