How to work LCD/TFT Monitor

How to work LCD/TFT Monitor

LCD Technologies:

LCD is classified into two types.

1.      Passive LCD’s -- These LCD’s doesn’t produce any light to turn on or off desired pixels to produce the characters or images. It uses a grid of conducting material to activate each pixel.

Advantage:

·         Less expensive than Active matrix displays

·         Ease of implementation.

Disadvantage:

·         Slow response time due to that it doesn’t produce colors exactly.

·         Poor contrast so that ghost images will appear.

.     Active LCD’s   -- These displays are similar to passive, but an active device (transistor) and a capacitor is connected to each pixel to control the voltage precisely. The capacitor for each pixel holds the charge for complete refresh cycle.

Advantage:

·         Faster pixel response rate than Passive matrix displays thus stunning images will be produced.

·         Higher contrast, higher resolution so that shaper display output.

·         This display’s comes with better viewing angle than passive matrix display.

Disadvantage:

·      hese displays are highly expensive than passive matrix displays, because each pixel require a transistor and capacitor pair.

·         More complex hardware is required.

 How LCDs Work?

The principle behind the LCD’s is that when an electrical current is applied to the liquid crystal molecule, the molecule tends to untwist. This causes the angle of light which is passing through the molecule of the polarized glass and also cause a change in the angle of the top polarizing filter. As a result a little light is allowed to pass the polarized glass through a particular area of the LCD. Thus that particular area will become dark compared to other. The LCD works on the principle of blocking light. While constructing the LCD’s, a reflected mirror is arranged at the back. An electrode plane is made of indium-tin oxide which is kept on top and a polarized glass with a polarizing film is also added on the bottom of the device. The complete region of the LCD has to be enclosed by a common electrode and above it should be the liquid crystal matter.

Next comes to the second piece of glass with an electrode in the form of the rectangle on the bottom and, on top, another polarizing film. It must be considered that both the pieces are kept at right angles. When there is no current, the light passes through the front of the LCD it will be reflected by the mirror and bounced back. As the electrode is connected to a battery the current from it will cause the liquid crystals between the common-plane electrode and the electrode shaped like a rectangle to untwist. Thus the light is blocked from passing through. That particular rectangular area appears blank.