Page 149 - CITS - Electronic Mechanic - TT - 2024

ELECTRONICS MECHANIC - CITS

When the light reaches to the far end of the liquid crystal substance, it vibrates at the same angle as that of the
final layer of the molecule vibrates. The light is allowed to enter into the device only if the second layer of the
polarized glass matches with the final layer of the molecule.
Working of LCD:
The principle of the LCD is that when an electrical current is applied to the liquid crystal molecule; molecule tends
to untwist. This causes the angle of light which is passing through the molecule of the polarized glass and also
causes a change in the angle of the top polarizing filter. A little light is allowed to pass the polarized glass through
a particular area of the LCD. Thus, that particular area will become dark.
The LCD works on the principle of blocking light. A reflected mirror is arranged at the back of LCDs. 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.

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-
phase electrode and the electrode shaped like a rectangle to untwist. Thus, the light is blocked from passing
through, and that particular rectangular area appears blank.
Advantages and Disadvantages of LCD
Advantages:

LCD consumes less power compared to CRT and LED.
LCDs consist of some microwatts for display in comparison to some mill watts for LED’s.
LCDs are low cost.
LCD provides excellent contrast.
LCDs are thinner and lighter when compared to cathode ray tube and LED.
Disadvantages of LCD:

Slightly more expensive than CRT
Can’t act as a portal to another dimension
Suffer from a motion blur effect
High refresh rate

Like the backlight ages, it can change colors slightly
The aspect ratio and resolution are fixed.
Different Size of LCDs:
There are different types of size available in the market few of them are:
480p – 720 x 480 pixels

720p (HD) – 1280 x 720 pixels.
1080p (Full HD) – 1920 x 1080 pixels.
1440p (2K QHD) – 2560 x 1440 pixels
2160p (4K UHD) – 3840 x 2160 pixels

4320p (8K UHD) – 7680 x 4320 pixels.
Types of LCDs:
1 Passive Matrix Display
2 Active-Matrix Display

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CITS : E & H - Electronics Mechanic - Lesson 77 - 83