Thin Film Electroluminescent DisplaysElectroluminescent display uses a thin film of solid, specially treated material that glows in response to electric current.Its construction is similar to plasma panel.The diff is that , the region b/w the glass plates is filled with a phosphors such as zinc sulfide doped with manganese instead of a gas.
To form a pixel on the screen, current is sent to the intersection of appropriate row & column. When voltage is applied to a pair of crossing electrodes, the phosphors become a conductor in the area of intersection of the two electrodes. Electrical energy is then absorbed by the manganese atoms, which then release the energy as a spot of light similar to the glowing plasma effect in a plasma panel.
Advantages: Provides very high image resolution & excellent graphic capability. These displays are bright & can be switched on & off quickly.Disadvantages: It require more power. Very Expensive. Good color & gray scale displays are hard to achieve.
Light Emitting Diode (LED)An LED is a unique type of semiconductor diode. Like a normal diode, it consists of a chip of semi -conducting material doped, with impurities to create a p-n junction. As in other diodes, current flows easily from the p-side, or anode, to the n- side, or cathode, but not in the reverse direction. Charge-carriers — electrons and electron holes — flow into the junction from electrodes with different voltages. When an electron meets a hole, it falls into a lower energy level, and releases energy in the form of a photon.
So we can say in LED a matrix of diodes is arranged to form the pixel position in the display and the picture definition is stored in a refresh buffer.Additionally, they are housed in a plastic bulb that concentrates the light in a particular direction.As you can see in the diagram, most of the light from the diode bounces off the sides of the bulb, traveling on through the rounded end.
Applications of LED’s: Status indicators on all sorts of equipment Traffic lights and signals Exit signs Motorcycle and Bicycle lights Toys and sporting goods. Railroad crossing signals. Continuity indicators. Remote controls
Advantages: It provide a good light contrast. They dont have a filament that will burn out, so they last much longer. Its small plastic bulb makes it a lot more durable. They also fit more easily into modern electronic circuits. It is efficient because LEDs generate very little heat, A much higher percentage of the electrical power is going directly to generating light.