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A Color LCD is a descendant of the primative monochrome LCD. This kind of LCD can emulate almost any real-life image compared to a monochrome LCD. Small monochrome displays such as those found in personal organizers, or older laptop screens have a passive-matrix structure employing supertwist nematic (STN) or double-layer STN (DSTN) technology (DSTN corrects a color-shifting problem with STN). Each row or column of the display has a single electrical circuit. The pixels are addressed one at a time by row and column addresses. This type of display is called a passive matrix because the pixel must retain its state between refreshes without the benefit of a steady electrical charge. As the number of pixels (and, correspondingly, columns and rows) increases, this type of display becomes increasingly less feasible. Very slow response times and poor contrast are typical of passive-matrix LCDs. In a monochrome plasma panel, control circuitry charges the electrodes that cross paths at a cell, causing the plasma to ionize and emit photons between the electrodes. The ionizing state can be maintained by applying a low-level voltage between all the horizontal and vertical electrodes - even after the ionizing voltage is removed. To erase a cell all voltage is removed from a pair of electrodes. This type of panel has inherent memory and does not use phosphors. A small amount of nitrogen is added to the neon to increase hysteresis. Twisted Nematic (TN)
* While CRTs are capable of displaying multiple video resolutions without introducing artifacts, LCD displays usually produce only crisp images in their "native resolution" or even fractions of it. LCDs with a small number of segments, such as those used in digital watches and pocket calculators, have a single electrical contact for each segment. An external dedicated circuit supplies an electric charge to control each segment. This display structure is unwieldy for more than a few display elements. A general purpose alphanumeric LCD, with two lines of 16 characters. Active matrix technologies Zero-power displays In color LCDs each individual pixel is divided into three cells, or subpixels, which are colored red, green, and blue, respectively, by additional filters. Each subpixel can be controlled independently to yield thousands or millions of possible colors for each pixel. Older CRT monitors employ a similar method for displaying color. Color components may be arrayed in various pixel geometries, depending on the monitor's usage. Pioneering work on liquid crystals was undertaken in the late 1960s by the UK's Radar Research Establishment at Malvern. The team at RRE supported ongoing work by George Gray and his team at the University of Hull who ultimately discovered the cyanobiphenyl liquid crystals (which had all of the correct stability and temperature properties for application in LCDs).
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The TN+Film (Twisted Nematic) display is the most common consumer display type, due to its lower price. The pixel response time on modern TN panels is sufficiently fast to avoid the shadow-trail artifacts that were a cause for complaint in the past. This fast response time has been a heavily marketed aspect of TN displays, although in most cases this number does not reflect performance across the entire range of possible color transitions. However this marketing strategy, combined with the relatively lower cost of production for TN panels, has led to the dominance of TN in the consumer market. In color LCDs each individual pixel is divided into three cells, or subpixels, which are colored red, green, and blue, respectively, by additional filters. Each subpixel can be controlled independently to yield thousands or millions of possible colors for each pixel. Older CRT monitors employ a similar method for displaying color. Color components may be arrayed in various pixel geometries, depending on the monitor's usage. Months after the release of the Nintendo Game Boy which had crude monochrome graphics on an LCD without backlight, Atari and Epyx released the Atari Lynx, which was the first handheld game console with interchangeable cartridges to have a backlit color LCD. Subsequent to the Lynx's release, the Sega Game Gear which also had a backlit color LCD was released. However, the Atari Lynx didn't have familiar titles like the Game Gear, and advertisements for the Game Gear claimed "Nintendo dosen't do what Sega does" hence the color graphics on the Game Gear. People however thought that those ads were offensive even though the Game Boy had crude monochrome graphics. Game consoles with color LCDs would not have critical success until the rise of the Gameboy Color. The TN display suffers from limited viewing angles, especially in the vertical direction, and some are unable to display the full 16.7 million colors (24-bit truecolor) available from modern graphics cards. These particular panels, with 6 bits per color channel as opposed to 8, can approach true 24-bit color using a dither method which quickly cycles pixels to simulate a given shade, which are noticeable to some and discomforting to others. Overall, color reproduction and linearity on TN panels is poor. Shortcomings in display color gamut (often referred to as a percentage of the NTSC color gamut) can also be attributed to backlighting technology. It is not uncommon for displays with CCFL (Cold Cathode Fluorescent Lamps) based lighting to range from 40% to 76% of the NTSC color gamut, whereas displays utilizing white LED backlights may extend past 100% of the NTSC color gamut -a difference quite perceivable by the human eye. Transmissive and reflective displays When an electrical charge is applied to the electrodes, the molecules of the liquid crystal align themselves parallel to the electric field, thus limiting the rotation of entering light. If the liquid crystals are completely untwisted, light passing through them will be polarized perpendicular to the second filter, and thus be completely blocked. The pixel will appear unlit. By controlling the twist of the liquid crystals in each pixel, light can be allowed to pass though in varying amounts, correspondingly illuminating the pixel. 1936: The Marconi Wireless Telegraph company patents the first practical application of the technology, "The Liquid Crystal Light valve".
Vertical Alignment (VA) Contrast ratio claims Important factors to consider when evaluating an LCD monitor include resolution, viewable size, response time (sync rate), matrix type (passive or active), viewing angle, color support, brightness and contrast ratio, aspect ratio, and input ports (e.g. DVI or VGA). * The viewing angle of a LCD is usually less than that of most other display technologies thus reducing the number of people who can conveniently view the same image. However, this negative has actually been capitalised upon in two ways. Some vendors offer portables with intentionally reduced viewing angle, to provide additional privacy for example when using the PC in airplanes. Secondly, it allows multiple TV outputs from the same LCD screen just by changing the angle from where the TV is seen. Such a set can also show two different images to one viewer, providing 3-D. Twisted Nematic displays contain liquid crystal elements which twist and untwist at varying degrees to allow light to pass through. When no voltage is applied to a TN liquid crystal cell, the light is polarized to pass through the cell. In proportion to the voltage applied, the LC cells twist up to 90 degrees changing the polarization and blocking the light's path. By properly adjusting the level of the voltage most any grey level or transmission can be achieved. IPS has since been superseded by S-IPS (Super-IPS), which has all the benefits of IPS technology with the addition of improved pixel refresh timing. Though color reproduction approaches that of CRTs, the contrast ratio remains relatively weak. S-IPS technology only appears in larger displays aimed at professionals, though pricing has come down to the reach of the typical consumer.