The category of large screen display technology and requirement of light-emitting devices

The classification of the electronic image on a large screen display technology is as follows:

projection too rely on the method of optical projection imaging screen display system, using the device and circuit were small, low cost. The technical defects is low brightness, contrast is poor, projection device takes a lot of space, is only applicable to general indoor screen.

direct-injection too screen display system using all kinds of light source as light-emitting unit of the screen, inlaid into a huge matrix for film and television image display. Its brightness, pixel density technology development in recent years, shows its vitality. The characteristics of the large screen display technology of all kinds of typical points mentioned below.

　　( 1) TV wall

TV wall is to sync signal decomposition and use at least two imaging unit display an image of the technology at the same time, the circuit is relatively simple.

early TV wall are using common picture tube as a unit. The adoption of plane rectangular composite image gap is too, after the image is divided, so again the TV wall in the display type of projection TV display unit, the TV wall in low brightness, only suitable for indoor.

　　( 2) LED display is

LED electroluminescent devices, light emitting from the 480 - nm wavelength ( Blu-ray) To 700 nm ( Red light) Ff: LED in technology have improved greatly.

using LED as light emitting display device, because of its simple circuit, power saving, low driving voltage, widely used in all kinds of display screen.

　　( 3) Incandescent bulbs display

bulb matrix large screen display with the development of computer control technology of matrix addressing. The 23rd Los Angeles Olympic Games venue is used in the bulb screen.

in the bulb screen system, each set of bulbs with red, green, blue, white light bulb - each Only, with the juice machine control, display text, graphics, or no gray cartoon. In recent years, the light bulb screen using the bulbs to the direction of miniaturization, energy conservation and development. With a reflective glass shell, small size mounted tungsten halogen quartz bubble of new light source is introduced bulb screen in the system. Bulb screen brightness and filament heating current exist between the nonlinear and complicated gray modulation circuit, which limits its application.

　　( 4)

the LCD display LCD display is a transmission type LCD display unit. Its advantage is small size, power saving; Defect is brightness is not enough, the applicable scope is small.

liquid crystal display (LCD) has the following main features:

(1) very low power consumption, the display panel power per square centimeter number amounts to decades amounts.

(2) low work voltage, about 10 v.

(3) belong to the illuminated LCD display, therefore in bright places shows that more and more distinct, and easy to color.

　　( 5) CRT/FDT color big screen

the CRT cathode ray tube ( 阴极射线管) , the fluorescent discharge tube (FDT 荧光放电管) 。 The luminescence principle is not the same. The former zapped with cathode ray fluorescent powder and light; The latter is anion posture of mercury atoms stimulated radiation of ultraviolet photons, ultraviolet photons stimulate phosphor and shine again.

use CRT or FDT light-emitting device spliced giant display screen, is now the most successful big screen used. Its high brightness, color reappearance ability, low power consumption, high pixel density, long life, makes the information display system is far too traditional gray system, for the AD showed the highest technical level in the media. This matrix display system composed of two kinds of light-emitting device significantly better than incandescent light bulbs, LED or matrix.

in order to obtain satisfactory color too screen display, outdoor of light-emitting device is put forward the following requirements:

(1) in order to be in the sunlight time can see colourful video images from the screen, to achieve all-weather according to requirements, the screen must be too with the 200 CD/m2 brightness.

(2) light emitting device should have a higher photoelectric conversion efficiency. This is because the system device has dry tens of thousands of light-emitting devices, power consumption is too. Efficiency difference depends on the light-emitting device, the power consumption in general is 0. 5 ~ 3 kw / m2。

3. Response time short, The rabbit lag images) And shall be able to display the 50 ~ 60 hz television image.

4. Strong colour rendering. This means that the light color purity and color coordinates of the device must meet the requirements.

5. Long life span, for thousands of hours or more.

several kinds of typical technical data of light-emitting devices are shown in table 1.

table 1 several kinds of typical technical parameters of light-emitting device