LCD Full Form is Liquid Crystal Display. LCD is one of the most opted technologies for display of monitors and display devices. LCDs have a wide range of use which includes televisions, computer monitors, cockpit displays in aircrafts, instrument panels, and more. LCDs have created a revolution by replacing the bulky display units with sleek, large, and flat screens. They give an elegant look to the modern devices.
With the advent of LCD, even various other common household items such as oven timers and digital clocks have a new form. The power consumption of liquid crystal display is less with a high definition output. This is because LCDs do not emit light. Rather they block light, which makes it comfortable for the eyes too.
When television was first invented it functioned on the cathode-ray tubes (CRT). These made the television a very bulky piece of electronic equipment that occupied a corner in the living room. Size- wise and weight- wise the television was a very heavy and big piece to handle. Nonetheless, since there was no other option available other than CRT televisions, the market was full of such items. Gradually, the technology improved and simpler systems of picture development were introduced. After CRT, LCD or Liquid Crystal Display televisions came into the market.
LCD Full Form – Additional Information
LCD or Liquid Crystal Display televisions are a step ahead of the cathode-ray tube versions. The technology for picture display is totally different from the CRT ones and thus, the models are more compact and sleek in size and shape. Since the LCD televisions are flat screen televisions, they can be easily mounted on the wall as well as placed on a table stand. LCD televisions use pixels to create a picture. There are millions of pixels on an LCD screen. Pixels are the picture elements that are red, blue and green light.
The picture is produced by rapid on and off the movement of the pixels. The pixels are turned on and off by electronically controlled liquid crystals that rotate the polarized light. The light is at the back of the screen and the pixels are in front. When the current is passed, it either passes through an active matrix grid or a passive matrix grid. Passive matrix grid has a grid of conductors with pixels at every intersection.
The passed current when travels through any two conductors, the light is controlled on the pixels and picture is formed. In an active matrix grid, there is a transistor at pixel intersection and this requires lesser energy to light up the pixels.The current in active matrix can be controlled well by switching on and off frequently thus giving a shorter refreshing rate that illuminates the pixels and gives a better picture quality. Because of the use of a transistor to control pixels, an active matrix LCD is recognized as TFT or Thin Film Transistor display.
HOW DOES LCD WORK?
As we know, a matter exists in three forms – solids, liquids, and gasses. However, it is very rare to find them in a combination of any two states. But in 1888 an Austrian chemist, Friedrich Reinitzer was successful in finding a liquid crystal that is the property of matter to exist in an in-between state of liquid and solid (crystals). Solids are a neat mass with a uniform pattern of atoms in a crystalline form. Liquids, on the other hand, have no definite shape or size as they only take the form of the container that holds them. A liquid crystal has the properties of solid as well as liquid. The two phases of liquid crystal are known as a smectic and nematic phase.
The nematic phase is the liquid phase in which the molecules have a free movement and the intermingling of particles is easy in a linear direction. The smectic phase is the solid part where the molecules form layers that can move against each other in an easy manner yet cannot cross over to other layers.
LCD uses the technique of forming picture through pixel movements. The back of the television screen has a strong light and there are millions of pixels covering it in front. Each pixel is composed of smaller sub-pixels that have red, blue or green light. Above all, each pixel has a polarizing glass behind it and another placed at 90 degrees in front.
Between the two polarizing filters lies the liquid crystal in nematic phase in a twisted form. When the current is passed, it blocks the light by one polarizer and when it is switched off, the light is allowed to pass through at 90 degrees making the pixel look bright.
FORMATION OF PICTURE
The picture is formed by turning on and off of the pixels. There are two polarizing filters – horizontal and another vertical at 90 degrees. When the pixels are switched off, the light passing from behind the screen is obstructed and only the light waves that are traveling horizontally can pass through. A transistor that controls the pixels turns it off when the electric current is passed. Thus, the liquid crystal in nematic phase straightens up from its twisted state and allows the light to pass through uninterrupted.
The light waves emerging from the crystal are horizontal and they get obstructed by the vertical filter that can only permit waves that vibrate vertically to pass through. Thus, the opposite clashes of polarized filters prevent the screen from lighting up and the pixels are dark.
Contrary to this state, when the pixels are switched on, the electric current passing through them has been turned off. Due to this, the liquid crystal gets twisted that reflects the light waves at 90 degrees. So the light that passes in a horizontal waveform is sent out in a vertical state. The vertical polarizing filter now allows only waves traveling in the vertical direction and thus the pixel is illuminated. The red, blue or green color in the sub-pixels gives the pixel its color and helps form an image that can be viewed on screen.
ADVANTAGES AND DISADVANTAGES OF LCD
The traditional television was made of cathode ray tubes that made it a bulky model. LCD televisions have a flat screen display and thus are compact and sleek. Besides being table mounted they can be safely put up on the wall, making the room clutter free and giving a better view without any obstruction. The picture quality is also sharp due to close-knit pixels and the colors are more real like and vibrant than CRT picture. LCD technology blocks the majority of the light before it reaches the viewing screen. Hence, more power is used up to illuminate the pixels thus making it as inefficient in power saving as the CRT version.
Initially, the LCD televisions had a poor picture quality and image distortion in fast-moving pictures. The colors also used to be hazy and muddy and it had a very poor contrast ratio. However, constant research and development on the product have resolved many issues and the LCD available now is far more superior quality than the earlier models. Many big companies like Sony, Sharp, LG etc have been manufacturing LCD televisions that are as large as 65 inches screen size. The display panel sizes have crossed 108 inches by Sharp and LG.
KNOWING MORE ABOUT LCD PURCHASE
On an average, an LCD television has 60,000 hours viewing time after which the picture and color quality is likely to deteriorate. Nothing lasts for infinity so a daily viewing of 8 hours is permissible to stretch the lifespan of the display to around 20 years. The most important factor of the television is the backlight that illuminates the pixels and the screen. A good quality light source can last for a longer period than cheap brands. Do not hesitate to invest in good brands like Sony, Sharp etc as they have high-quality lighting source installed that is guaranteed to give a longer service than the cheap Chinese or Korean brands that will render the television dysfunctional due to power breakdown.
The back light quality is the deciding factor for the color display and synchronization. Thus, a good product is a wise buy. LCD work on blocking rather than emitting light. Therefore, there are very fewer chances of the burn in the process.Even though the development has allowed the picture quality to be good in larger sizes, it is a fact that the smaller the screen denser the pixels and higher the sharpness and color display. LCD televisions have its own pros and cons. Nonetheless, for a better picture quality, it is definitely a good option than CRT.