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}}

There are three different '''addressing schemes''' for [[display device]] devicess: ''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 gray-scale[[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''&times;×''n'' pixels, this scheme would require ''m''&times;×''n'' control signals. in grayscale. This is generally considered to be inefficient, and is technically impossible for modern displays -- for example, 1920 x 1080 pixels and an inefficientRGB usesystem (3 times as many control signals needed) results in ~6 million control lines.<ref name=":0">{{Citation |last=Blankenbach |first=Karlheinz |title=Direct Drive, Multiplex and Passive Matrix |date=2012 |work=Handbook of IVisual Display Technology |pages=417–437 |editor-last=Chen |editor-first=Janglin |url=https://link.springer.com/referenceworkentry/10.1007/O978-3-540-79567-4_33 and|access-date=2025-03-06 physical|place=Berlin, spaceHeidelberg |publisher=Springer |language=en |doi=10.1007/978-3-540-79567-4_33 |isbn=978-3-540-79567-4 |last2=Hudak |first2=Andreas |last3=Jentsch |first3=Michael |editor2-last=Cranton |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''&times;×''n'' pixels, this scheme would requirerequires ''m''+''n'' control signals. When a row and column arein activatedgrayscale, 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 maintainedthree attimes anyas onemany time,in which means that the state of the pixel must persist without a control signal during the time which other pixels are being addressedRGB.<ref name=":0" This/> persistence can be accomplished through [[active matrix addressing]], [[passive matrix addressing]], or the persistence of vision of the (usually human) eye. 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 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]]