Liquid Crystal Display (LCD)

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Liquid Crystal Display (LCD)

Post  admin on Fri 23 Jul 2010, 2:45 am



LCD monitors are generally thinner than their CRT counterparts due to the technology that operates them. A liquid crystal layer is sandwiched between two transparent sheets. The layers can be referred to as substrates. When an electrical current is sent through the substrates, light is transferred into the screen and its optical properties are changed. The light will then either be blocked or allowed through the area, which represents a pixel. Each pixel is controlled by 3 transistors, which allow the pixel to display different colours as each transistor uses red, blue and green. An increase in voltage to the screen increases the intensity of a pixel. LCD monitors can either be classified as passive or active matrixes. Passive matrixes use a grid to allow electrical charges to be sent to a pixel. While simple, passive matrixes have high response times, which means the ghosting of fast moving images is noticeable, when a mouse is used, trails are left due to the refresh rate of the passive matrix being too slow. Active matrix screens uses thin film transistors, which utilise switching transistors and capacitors to store the charge sent to it until the net refresh. It also allows individual pixels to be refreshed, unlike passive matrix LCDs, which have require a whole row of pixels to be refreshed at the same time. Active matrix also allows precise voltage control, allowing the display of fine changes to the colour.




LCD screens emit far less magnetic radiation compared to CRT monitors due to the difference in technology. LCD monitors also consume far less power and its physical size and weight means that they can be used in portable devices such as phones and laptop computers. In the past, LCD was inferior to CRT in terms of resolution and colour reproduction, now, LCD monitors have largely replaced the bulky CRT screens and image quality and resolution has greater improved.

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