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What is LCD?

What is LCD

LCD is a flat display technology, stands for "Liquid Crystal Display," which is generally used in computer monitors, instrument panels, cell phones, digital cameras, TVs, laptops, tablets, and calculators. It is a thin display device that offers support for large resolutions and better picture quality. The older CRT display technology has replaced by LCDs, and new display technologies like OLEDs have started to replace LCDs. An LCD display is most commonly found with Dell laptop computers and is available as an active-matrix, passive-matrix, or dual-scan display. The picture is an example of an LCD computer monitor.

The LCD displays are not only different in terms of heavy than CRT monitors; even the process of working of them is also different. An LCD contains a backlight rather than the firing electrons at a glass screen, which offers light to individual pixels arranged in a rectangular grid. All pixels have a sub-pixel, red, green, and blue, which can be turned on or off. The display appears black if all of a pixel's sub-pixels are turned off and appears white if all the sub-pixels are turned on 100%. The millions of color combinations can be possible with the help of adjusting the individual levels of red, green, and blue light.

As compared to CRT technology, LCD consumed much less power and allowed displays to be much thinner that also made them very less heavy. Instead of emitting light, LCDs work on the principle of blocking light. In an LCD, where an LED ejects light, the liquid crystals produce a picture with the help of using a backlight. Also, while comparing with gas-display and LED displays, LCDs consume less energy.

The CRT monitors and TVs have a refresh rate, but LCD screens do not have a refresh rate. If you feel a problem with eye strain with the CRT monitor, you might need to change the monitor's refresh rate setting on your CRT screen. But with the new LCD screen, you do not need to adjust the refresh rate setting. Some LCD computer monitors provide support for VGA cables, and most have a connection for HDMI and DVI cables. But offering support for VGA cables is much less common.

Different Types of LCD

There are various kinds of LCD, which are discussed below:

  1. Twisted Nematic (TN): The TN LCDs are very common that are used in several types of displays over the industries, which led to its production much frequently. As compared to other displays, these displays are inexpensive and have high response times; therefore, these are most commonly used by gamers. These displays are more appropriate for daily operations, but they have low contrast ratios, viewing angles, and reproduction of color. These displays are available with 240 hertz (Hz) as these are the only gaming displays.
  2. In-Plane Switching (IPS): In Panel Switching displays give better picture quality, vibrant color precision & difference while comparing with TN LCDs. Graphic designer and some other applications commonly use these displays; hence, these are considered to be the best LCD.
  3. Vertical Alignment Panel (VA Panels): The vertical alignment panels are considered to deliver the medium quality between in-plane switching panel and Twisted Nematic technology. As compared to TN-type displays, this kind of panel has color reproduction with higher quality as well as best viewing angles features. Also, these panels are much sufficient for daily use and more reasonable, but these contain a low response time. As compared to the Twisted Nematic display, these panels generate deeper blacks with better colors. While comparing with TN kind displays, numerous crystal alignments can permit better viewing angle. Additionally, these displays are costly comparing to other displays. Hence these come with a tradeoff.
  4. Advanced Fringe Field Switching (AFFS): AFFS LCD is a top performer and offers an extensive choice of color reproduction. These displays provide good image quality. Generally, these displays are most commonly used in highly advanced applications such as viable airplane cockpits.

How LCDs Work?

The principle behind the LCDs is that for switching pixels on and off to reveal a specific color, LCD screens use liquid crystals. And, the molecule tends to untwist at the time of electrical current is applied to the liquid crystal molecule. This becomes the reason for a change in the angle of the top polarizing filter as well causes the angle of light, a light that is passing through the molecule of the polarized glass. Consequently, with the help of an individual area of the LCD, a small light is allowed to permit the polarized glass.

Thus, as compared to other areas, this particular area will become dark. Instead of emitting light, LCDs work on the principle of blocking light. A reflected mirror is arranged at the backside at the time of constructing the LCDs. An indium-tin-oxide is used to make the electrode plane, which is kept on top of the device. Also, on the bottom of the device, a polarized glass with a polarizing film is added. With the help of a common electrode, the LCD's complete area has to be enclosed, and the liquid crystal matter should be above it.

Then comes another polarizing film on top, and on the bottom, in the form of rectangle, the second piece of glass comes with an electrode. But make sure that both pieces are located on the right angles. The light passes through the front of the LCD when there is no current, reflecting with the help of a mirror and bounced back. A screen is in front of the light that is made up of pixels colored red, green, and blue. In order to reveal a certain color or keep that pixel black, the liquid crystals work for turning a filter on or off. This is the reason; the LCD monitors and TVs consume much less power as compared to CRT monitors or televisions.

History of LCD

What is LCD

In 1888, Friedrich Reinitzer, chemist and Austrian botanist, discovered the first liquid crystals in cholesterol extracted from carrots.

In 1962, with the help of the application of a voltage, stripe patterns in a tinny layer of liquid crystal material were generated by RCA researcher Richard Williams. This impact is depending upon an electrohydrodynamic instability forming inside the liquid crystal that is currently known as "Williams domains."

According to the IEEE, a method for electronic control of light was planned by George Heilmeier with Louis Zanoni and Lucian Barton led by a team of engineers and scientists at the RCA David Sarnoff Research Center in Princeton, New Jersey, in the mid of 1964 and 1968. And, they demonstrated the liquid crystal display for the first time.

Additionally, a global industry was launched by their work that now produces millions of LCDs. He used Heilmeier's liquid crystal displays as dynamic scattering method (DSM), in which an electrical charge is implemented to scatter light by rearranging the molecules. The dynamic scattering method was proved to be consumed high power and worked badly. Hence, an improved version of DSM replaced the older one. And, in 1969, James Fergason invented the twisted nematic field effect of liquid crystals, which was used by this improved version.

James Fergason

In the early 1970s, in liquid crystal displays filed, James Fergason is hold some of the fundamental patents. Also, for "Display Devices Utilizing Liquid Crystal Light Modulation, he holds a key US patent number 3,731,986. Later in 1972, the first modern LCD watch based on James Fergason's patent was produced by the ILIXCO, International Liquid Crystal Company owned by inventor James Fergason.

Advantages of LCD

LCD panels are increasingly rapidly and replacing CRT monitors and televisions in many homes and offices. These displays provide multiple benefits while comparing with CRT technology. Some advantages are discussed below:

  • Space: LCD (Liquid Crystal Display) technology made display screens much thinner as compared to CRT technology, through which they take up much less space. LCD displays do not take space taken up by the cathode ray tube; therefore, they are also called flat panel screens. Thus, there is much space on the table that allows keeping other documents and peripheral computer equipment easily on the desk. Hence, LCD panels have almost replaced the CRT displays.
  • Power Consumption: One of the best advantages of LCD displays is less energy Consumption. It takes very less energy as compared to CRT technology. If the size increases of LCD monitors, its power consumption is also increased; But it still takes low power while comparing with CRT monitors. On the basis of the size, the power consumption of LCD monitors is around 25 to 50 watts, but the same size of CRT monitor takes 60 to 80 watts. If the size of the CRT monitor is 19-inch, it will consume anything between 70 and 150 watts.
  • Brightness: As compared to CRT technology, LCD monitors provide output with brighter pictures as they generate the high peak intensity. Due to high-intensity results, LCD panels illuminate the screen through a constant backlight. Thus, LCD monitors are sufficient for use in brightly lit areas.
  • Screen Flicker: The screen viewing area is scanned as horizontal lines in CRT monitors. And, the rate at which the entire screen is scanned is called refresh rate. Typically, CRT monitors have a flickering effect as they contain a low refresh rate. The flickering effect can be caused to detrimental health and eye strain, and headaches if anyone is viewing for a long time period. LCD monitors have a very high refresh rate in comparison to CRT monitors. They have a refresh rate of 75 and 85 hertz being common, which means the flickering effect is very low in LCD displays that made them much comfortable to use anywhere.
  • No burn-in: With the LCD displays, you can end up with a lot of static content (images that don't change or move around) when you watch the stock ticker on MSNBC, play a lot of video games, or do other things. But CRT displays involve those images and content that cannot end up. It is done with LCD because instead of creating its own light with phosphors, it utilizes a separate backlight. Hence, they are sufficient in this problem; however, plasmas are unable to do that.

Disadvantages of LCD

LCD has many advantages, but it also has some disadvantages, which are discussed below:

  • Expensive for their size: As compared to plasma flat panels, LCDs can be more costly in order to increase the size. However, while comparing with CRTs, it may be at in low price. Currently, LCD screens are produced by some of the manufacturers in Taiwan, and Japan, which led to the technology is not much popular and has not completely spread. Also, the price can be different in the international market as much as tens to hundreds of dollars.
  • Interfaces: Although the LCD displays (LCDs) are at the top in the case of digital interface, some of the low-priced LCDs have problems like the inability to upgrade to digital interfaces, vulnerable signal transmission interference, etc. Furthermore, the analog signal, vector, and clock frequency must be consistent in order to avoid the occurrence of the flicker effect. Additionally, the display CARDS with digital output are rare, and the digital interfaces of LCD have not yet been standardized.
  • Small viewing Angle: Typically, LCDs have poor viewing angle; however, manufacturers are improving by giving some intensive efforts. Poor viewing angle results that you do not get a better image quality if you are watching the screen on some of the left and right sides, but not almost directly in the front of the screen.
  • Limited brightness: Compared with plasma TVs, LCD displays are harder to view in a brightly lit room and have lower contrast because these displays depend upon external light sources to assist in emitting light as they are unable to emit light by themselves. In this case, LCD TVs with LED backlights are more appropriate.
  • Poor reproduction of blacks: The reproduction of black images in LCD displays is poor as compared to direct-view tube displays. That means the darker screen images will look like various shades of gray but not show up as true black. Also, there can be difficult to discern the actions happening in these darker areas.





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