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There are three different '''addressing schemes''' for [[display]]- devices;: ''electronicallydirect'' or, ''optically addressed displaysmatrix'', orand ''addressing by plasma columnsraster''. Each teqniqueThe allowspurpose aof physicaleach wayscheme ofis to set (or switchingmaintain) the state of a [[pixel]] to aeither black-/white or, more usuallycommonly, a gray-scale statelevel.
==Direct addressing==
'''Electronic and plasma schemes:''' Colour displays or the [[pixel geometry]] are actually implemented using three [[gray-scale]] component system making up one [[pixel]], and each component is followed with a [[primary colour]]-filter to separate the [[red]], [[green]] and [[blue]]. So the treatment simplifies since it is sufficient to consider only a pixel with ''N'' gray shades. The shade level is typically lineary dependent on the applied potential over the pixel, so each level will translate into a separation of say ''ΔV/N'' [[volt]]s per gray shade, where ''ΔV'' is the potential range that the pixel respons to. Each separation is typically some [[millivolt|mV]]. Since there is risk for a [[crosstalk|cross-talk]] at neighbouring pels, the addressing scheme must carefully be designed so that addressing a pixel does not affect other neighbours. If cross-talk occures, then the [[contrast]] is reduced.
A '''direct addressed''' display runs individual control signals to each pixel. This allows the state, whether on/off or grayscale, to be set and maintained on each pixel. For a screen size of ''m''×''n'' pixels, this scheme would require ''m''×''n'' control signals. This is generally considered to be an inefficient use of I/O and physical space.
==Matrix addressing==
'''Optical scheme:''' The image is not pixalized at all and it is transferred from the camera or the like directly onto the LCD-screen. The image is displayed in high resolution.
A '''matrix addressed''' display runs control signals only to the rows and columns of the display. (See also: [[Matrix (mathematics)|matrix]]) For a screen size of ''m''×''n'' pixels, this scheme would require ''m''+''n'' control signals. When a row and column are activated, only the pixel at the intersection of the row and column is addressed. In this scheme only a single pixel can have its state set or maintained at any one time, which means that the state of the pixel must persist without a control signal during the time which other pixels are being addressed. This persistance can be accomplished through [[active matrix addressing]], [[passive matrix addressing]], or the persistance of vision of the (usually human) eye. Persistance of vision is used in simpler, slower changing displays such as clocks.
== ElectronicallyRaster addressing ==
A '''raster addressed''' display (e.g., a [[CRT]]) works by scanning across the entire display in sequence while modulating control signal to activate each pixel as it is scanned. This display uses persistance of the pixel element (e.g., [[phosphor]]) to maintain the pixel state until the scan can visit that pixel again. There are are only three control signals required for this to work: a horizontal scan control signal, a vertical scan control signal, and an intensity control signal. Timing between these signals is very important, else the image on the screen will show artifacts.
There is three kinds of electronically addressing schemes for [[Liquid crystal display|Liquid Crystal Displays (LCD)]]. [[Direct addressing|Direct addressed]] display include a conductor to each [[pixel]], and thus, for a ''n'' × ''m''-display, (''n'' × ''m'') pads are needed. [[Active matrix addressing|Active]] and [[Passive matrix addressing]] wire the conductors in a [[Matrix (mathematics)|matrix]]. The former needs to connect one [[Thin Film Transistor|Thin Film Transistors (TFT)]] to each pixel, and the latter relies on the pixel's [[bistable|bistabilty]] such as [[ferroelectric|ferroelectrism]]. For a ''n'' × ''m''-matrix schemes, only (''n'' + ''m'') pads are needed.
[[Category:Display technology]]
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