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The xenon and neon gas in a plasma television is contained in hundreds of thousands of tiny cells positioned between two plates of glass. Long electrodes are also sandwiched between the glass plates, on both sides of the cells. The address electrodes sit behind the cells, along the rear glass plate. The transparent display electrodes, which are surrounded by an insulating dielectric material and covered by a magnesium oxide protective layer, are mounted above the cell, along the front glass plate. 1911: Charles Mauguin describes the structure and properties of Liquid Crystals. Normal Liquid Crystal Displays like those found in calculators have direct driven image elements – a voltage can be applied across one segment without interfering with other segments of the display. This is impractical for a large display with a large number of pixels since it would require millions of connections - top and bottom connections for each of red, green and blue of every pixel. To avoid this issue, the pixels are addressed in rows and columns which reduce the connection count from millions to thousands. If all the pixels in one row are driven with a positive voltage and all the pixels in one column are driven with a negative voltage, then the pixel at the intersection has the largest applied voltage and is switched. The problem with this solution is that all the pixels in the same column see a fraction of the applied voltage as do all the pixels in the same row, so although they are not switched completely, they do tend to darken. The solution to the problem is to supply each pixel with its own transistor switch which allows each pixel to be individually controlled. The low leakage current of the transistor also means that the voltage applied to the pixel does not leak away between refreshes to the display image. Each pixel is a small capacitor with a transparent ITO layer at the front, a transparent layer at the back and a layer of insulating liquid crystal between. Drawbacks The layout of the circuit is very similar to the one used in DRAM computer memory but rather than being built using silicon wafers, the whole structure needs to be created on glass. Many of the processing techniques used in creating circuits on silicon require temperatures in excess of the melting point of glass. The silicon substrate of normal semiconductors is grown from liquid silicon to produce a large single crystal with excellent properties for transistors. The silicon layer for TFT LCDs is deposited from Silane gas to produce an amorphic or polycrystalline silicon layer which is far less suitable for producing high grade transistors.
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. * Thin-film transistors and color filters 1911: Charles Mauguin describes the structure and properties of Liquid Crystals.
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* Many users of older (around pre-2000) LCD monitors get migraines and other severe eyestrain problems from the flicker nature of the fluorescent backlights. If you experience eyestrain issues with LCDs, consider these possibilities: using a small resolution for reading text, on a >=15 inch LCD, glare from another light, brightness is set too low or high, defective backlight, LCD monitor is too close, or too far away, Not using WindowsXP Cleartype (generally helps improve font visibility, but can cause some problems in some cases). 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. Techniques for color graphics 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. Active matrix technologies
History * 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. Zero-power displays Twisted Nematic (TN) Twisted Nematic (TN)