Passive matrix addressing is an
addressing scheme used in early
LCDs. This is a matrix addressing scheme meaning that only ''m'' + ''n'' control signals are required to address an ''m'' × ''n'' display. A
pixel
In digital imaging, a pixel (abbreviated px), pel, or picture element is the smallest addressable element in a raster image, or the smallest point in an all points addressable display device.
In most digital display devices, pixels are the ...
in a passive matrix must maintain its state without active driving circuitry until it can be refreshed again.
The
signal
In signal processing, a signal is a function that conveys information about a phenomenon. Any quantity that can vary over space or time can be used as a signal to share messages between observers. The '' IEEE Transactions on Signal Processing' ...
is divided into a row or ''select signal'' and a column or ''video signal''. The select
voltage
Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric potential between two points. In a static electric field, it corresponds to the work needed per unit of charge to ...
determines the row that is being addressed and all ''n'' pixels on a row are addressed simultaneously. When
pixels
In digital imaging, a pixel (abbreviated px), pel, or picture element is the smallest addressable element in a raster image, or the smallest point in an all points addressable display device.
In most digital display devices, pixels are the sm ...
on a row are being addressed, a ''V
sel'' potential is applied, and all other rows are unselected with a ''V
unsel'' potential. The video signal or column potential is then applied with a potential for each ''m'' columns individually. An on-switched (lit)
pixel
In digital imaging, a pixel (abbreviated px), pel, or picture element is the smallest addressable element in a raster image, or the smallest point in an all points addressable display device.
In most digital display devices, pixels are the ...
corresponds to a ''V
on'', an off-switched (unlit) corresponds to a ''V
off'' potential.
The potential across
pixel
In digital imaging, a pixel (abbreviated px), pel, or picture element is the smallest addressable element in a raster image, or the smallest point in an all points addressable display device.
In most digital display devices, pixels are the ...
at selected row ''i'' and column ''j'' is
:
and
:
for the unselected rows.
[P. M. Alt, P. Pleshko ''Scanning limitations of liquid-crystal displays,'' IEEE Trans. Electron Devices, vol. ED-21, pp. 146–155, Feb. 1974.]
Passive matrix addressed displays, such as
Ferro Liquid Display, do not need the switch component of an active matrix display, because they have built-in
bistability
In a dynamical system, bistability means the system has two stable equilibrium states. Something that is bistable can be resting in either of two states. An example of a mechanical device which is bistable is a light switch. The switch lever ...
. Technology for
electronic paper
Electronic paper, also sometimes electronic ink, e-ink or electrophoretic display, are display devices that mimic the appearance of ordinary ink on paper. Unlike conventional flat panel displays that emit light, an electronic paper display ...
also has a form of bistability. Displays with bistable pixel elements are addressed with a passive matrix addressing scheme, whereas
TFT LCD displays are addressed using
active addressing.
See also
*
Active matrix addressing
*
Pixel geometry
The components of the pixels (primary colors red, green and blue) in an image sensor or display can be ordered in different patterns, called pixel geometry.
The geometric arrangement of the primary colors within a pixel varies depending on usage ...
*
Liquid crystal display
A liquid-crystal display (LCD) is a flat-panel display or other electronically modulated optical device that uses the light-modulating properties of liquid crystals combined with polarizers. Liquid crystals do not emit light directly but ...
References
{{DEFAULTSORT:Passive Matrix Addressing
Digital imaging
Liquid crystal displays