An LCD or liquid crystal display is a type of flat panel display commonly used in digital devices.Liquid crystals do not emit light directly. for example: digital clocks, appliance displays, and portable computers.
LCDs are available to display arbitrary images (as in a general-purpose computer display) or fixed images which can be displayed or hidden, such as preset words, digits, and 7-segment displays as in a digital clock. They use the same basic technology, except that arbitrary images are made up of a large number of small pixels, while other displays have larger elements.
LCDs are used in a wide range of applications including computer monitors, televisions, instrument panels, aircraft cockpit displays, and signage. They are common in consumer devices such as video players, gaming devices, clocks, watches, calculators, and telephones, and have replaced cathode ray tube (CRT) displays in most applications. They are available in a wider range of screen sizes than CRT and plasma displays, and since they do not use phosphors, they do not suffer image burn-in. LCDs are, however, susceptible to image persistence.
The LCD is more energy efficient and can be disposed of more safely than a CRT. Its low electrical power consumption enables it to be used in battery-powered electronic equipment. It is anelectronically modulated optical device made up of any number of segments filled with liquid crystals and arrayed in front of a light source (backlight) or reflector to produce images in color ormonochrome. Liquid crystals were first developed in 1888. By 2008, worldwide sales of televisions with LCD screens exceeded annual sales of CRT units; the CRT became obsolete for most purposes.
George Harry Heilmeier (born May 22, 1936) is an American Electrical engineer and businessman, who was a pioneering contributor to Liquid Crystal Display (LCD).
How an LCD Works
According to a PC world article, liquid crystals are liquid chemicals whose molecules can be aligned precisely when subjected to electrical fields, much in the way metal shavings line up in the field of a magnet. When properly aligned, the liquid crystals allow light to pass through.
A simple monochrome LCD display has two sheets of polarizing material with a liquid crystal solution sandwiched between them. Electricity is applied to the solution and causes the crystals to align in patterns. Each crystal, therefore is either opaque or transparent, forming the numbers or text that we can read.
History of Liquid Crystal Displays – LCD
In 1888, liquid crystals were first discovered in cholesterol extracted from carrots by Austrian botanist and chemist, Friedrich Reinitzer.(This is the commwenr rhe )
In 1962, RCA researcher Richard Williams generated stripe-patterns in a thin layer of liquid crystal material by the application of a voltage. This effect is based on an electro-hydrodynamic instability forming what is now called “Williams domains” inside the liquid crystal.
According to the IEEE, “Between 1964 and 1968, at the RCA David Sarnoff Research Center in Princeton, New Jersey, a team of engineers and scientists led by George Heilmeier with Louis Zanoni and Lucian Barton, devised a method for electronic control of light reflected from liquid crystals and demonstrated the first liquid crystal display. Their work launched a global industry that now produces millions of LCDs.”
Heilmeier’s liquid crystal displays used what he called DSM or dynamic scattering method, wherein an electrical charge is applied which rearranges the molecules so that they scatter light.
The DSM design worked poorly and proved to be too power hungry and was replaced by an improved version, which used the twisted nematic field effect of liquid crystals invented by James Fergason in 1969.
|Brightness||Produces very bright images due to high peak intensity. Very suitable for environments that are brightly lit .|
|Emissions||Produce considerably lower electric, magnetic and electromagnetic fields than CRTs.|
|Geometric Distortion||No geometric distortion at the native resolution. Minor distortion can occur for other resolutions.|
|Power Consumption||Energy efficient. Consume less than 1/3 the power of a comparable CRT. Consume less electricity than a CRT and produce little heat.|
|Physical Aspects||Take up about 40% less desk space. LCDs are thin and compact.|
|Screen Shape||Completely flat screen.|
|Sharpness||At the native resolution, the image is perfectly sharp. Adjustments are required at all other resolutions which can result in measurable degradation to the image.|