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]]-devices; 1) electronically or 2) optically addressed displays, or 3) addressing by plasma columns. Each teqnique allows a physical way of switching the [[pixel]] to a black-white or more usually gray-scale state.

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==

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 gap of say ''δV/N'' [[volt]]s per gray shade. Since there is risk for a [[crosstalk|cross-talk]], the addressing scheme must carefully be designed so that addressing a pixel does not affect other neighbours.

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 inefficient, and is technically impossible for modern displays -- for example, 1920 x 1080 pixels and an RGB system (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 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 |place=Berlin, Heidelberg |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>

== ElectronicallyMatrix 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: [[Multiplexed_display#Pixel-oriented_displays|Display matrix]]) For a screen size of ''m''×''n'' pixels, this scheme requires ''m''+''n'' control signals in grayscale, or three times as many in RGB.<ref name=":0" />

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}}

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''&times;''m''-display, (''n''&times;''m'') pads are needed. [[Active matrix addressing|Active]] and [[Passive matrix addressing]] wire the conductors in a [[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''&times;''m''-matrix schemes, only (''n'' + ''m'') pads are needed.

[[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]]