Display addressing scheme: Difference between revisions

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{{Short description|Scheme to set or maintain the state of a pixel in a display device}}

{{unreferenced|date=June 2009|bot=yes}}

There are three different '''addressing schemes''' for [[display device]]s: ''direct'', ''matrix'', and ''raster''.{{Dubious|date=March 2025|reason=What about active addressing v. passing addressing? What about orthogonal functions?}}{{Citation needed|date=March 2025}} The purpose of each scheme is to set (or maintain) the state of a [[pixel]] to either black/white or, more commonly, a [[grayscale]] level.{{Citation needed|date=March 2025}}

==Direct addressing==

A '''direct-driven''', or '''directly addressed'''{{Citation needed|date=March 2025}} 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. in grayscale. This is generally considered to be an inefficient, useand ofis I/Otechnically andimpossible physicalfor space.Directmodern addressingdisplays mode-- meansfor thatexample, the1920 valuex for1080 apixels givenand instructionan inRGB assemblysystem programming(3 istimes pointedas tomany bycontrol asignals givenneeded) results in ~6 million control valuelines.<ref Thisname=":0">{{Citation means|last=Blankenbach the|first=Karlheinz value|title=Direct isDrive, Multiplex and Passive Matrix |date=2012 |work=Handbook of Visual Display Technology |pages=417–437 |editor-last=Chen |editor-first=Janglin |url=https://link.springer.com/referenceworkentry/10.1007/978-3-540-79567-4_33 |access-date=2025-03-06 variable|place=Berlin, basedHeidelberg on|publisher=Springer what|language=en is|doi=10.1007/978-3-540-79567-4_33 stored|isbn=978-3-540-79567-4 in|last2=Hudak memory|first2=Andreas at|last3=Jentsch a|first3=Michael given|editor2-last=Cranton address|editor2-first=Wayne |editor3-last=Fihn |editor3-first=Mark|url-access=subscription }}</ref>

==Matrix addressing==

A '''matrix-driven''', or '''matrix addressed'''{{Citation needed|date=March 2025}} display runs control signals only to the rows (lines) and columns of the display.<ref name=":0" /> (See also: [[Matrix (mathematics)Multiplexed_display#Pixel-oriented_displays|Display matrix]]) For a screen size of ''m''×''n'' pixels, this scheme would requirerequires ''m''+''n'' control signals. Inin [[active matrix addressing]]grayscale, someor sortthree oftimes capacitoras (externalmany toin the cell proper) is used to maintain the state of the cellRGB.<ref [[Passivename=":0" matrix/> addressing]] is used when cell itself has a bistability, so no external capacitor is needed. In some situations passive matrix addressing is used with the help of persistence of vision of the (usually human) eye so the cell need not be bistable. Persistence of vision is used in simpler, slower changing displays such as clocks.

To address all pixels of such a display in the shortest time, either entire rows or entire columns have to be addressed sequentially. As many images are shown on a [[16:9 aspect ratio]], the sequential addressing is typically done row-by-row (i. e. line-by-line). In this case, fewer rows than columns have to be refreshed periodically.{{Citation needed|date=March 2025}}

[[Passive matrix addressing]] is used with the help of persistence of vision of the (usually human) eye so the cell need not be bistable. Persistence of vision is used in simpler, slower changing displays with relatively few picture elements such as clocks. In [[active matrix addressing]], some sort of capacitor (external to the cell proper) is used to maintain the state of the cell. When the electro-optical property of cells itself is bistable, passive matrix addressing

without external capacitor can be implemented.{{Citation needed|date=March 2025}}

Active matrix displays are able to have higher resolution, contrast, and colors, but passive matrix displays can often be cheaper.<ref name=":0" />

==Raster addressing==

A '''raster addressed''' display (e.g., a [[Cathode -ray tube|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 persistence of the pixel element (e.g., [[phosphor]]) to maintain the pixel state until the scan can visit that pixel again. There 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.{{Citation needed|date=March 2025}}

==References==

{{Reflist}}

[[Category:Display technology]]