An electronic visual display, informally a screen, is a display device for presentation of images, text, or video transmitted electronically, without producing a permanent record. Electronic visual displays include television sets, computer monitors, and digital signage. They are also ubiquitous in mobile computing applications like tablet computers, smartphones, and information appliances.
Electronic visual displays present visual information according to the electrical input signal (analog or digital) either by emitting light (then they are called active displays) or, alternatively, by modulating available light during the process of reflection or transmission (light modulators are called passive displays).
|Electronic visual displays|
|present visual information by emitting light||present visual information by modulating light|
|Effect||Liquid crystal display (LCD) + backlight
(this combination is considered an active display)
|Example||LCD TV screen, LCD computer monitor||LCD watch (reflective)
see LCD classification
also see Electronic paper
|Example||Cathode ray tube (CRT)
Field emission display (FED)
Vacuum fluorescent display (VFD)
Surface-conduction electron-emitter display (SED)
|Research & manufacturing:
E Ink electronic paper displays
SiPix Microcup Electronic Paper
|Example||(thin or thick film) electro-luminescence (EL)
(inorganic or organic) light emitting diode (LED, OLED)
gas discharge display (Nixie tube)
|Research & manufacturing:
ntera NanoChromics Technology
|Example||Plasma display panel (PDP)||Research & manufacturing:
|Example||Numitron, a 7-segment numerical display tube Numitron website||flap display
digital micromirror device (DMD)
Interferometric modulator display (IMOD)
telescopic pixel display
Display mode of observation
Electronic visual displays can be observed directly (direct view display) or the displayed information can be projected to a screen (transmissive or reflective screen). This usually happens with smaller displays at a certain magnification.
|Direct view display||Projection display|
|transmissive mode of operation||front-projection (with reflective screen)
e.g. video projector
|reflective mode of operation||rear-projection (with transmissive screen)
e.g. rear projection television screen
|transflective mode of operation
(e.g. transflective LCD)
|retinal projection (with or without combiner)
e.g. head mounted display
A different kind of projection display is the class of "laser projection displays", where the image is built up sequentially either via line by line scanning or by writing one complete column at a time. For that purpose one beam is formed from three lasers operating at the primary colors, and this beam is scanned electro-mechanically (galvanometer scanner, micro-mirror array)) or electro-acousto-optically.
Layout of picture elements
Depending on the shape and on the arrangement of the picture elements of a display, either fixed information can be displayed (symbols, signs), simple numerals (7-segment layout) or arbitrary shapes can be formed (dot-matrix displays).
characters, numbers and symbols of fixed shape (may be multiplex addressed)
The following layouts are well known:
sub-pixels are arranged in a regular 2-dimensional array
(multiplex addressing required); arbitrary shapes can be formed and displayed
Emission and control of colors
Colors can be generated by selective emission, by selective absorption, transmission or by selective reflection.
primary colors add up to produce white light
filters, dyes, pigments (e.g.printing) subtract (absorb) parts of white light
|temporal mixing (additive)
e.g. rotating primary color filter wheel in projectors
|spatial mixing (additive)
closely spaced sub-pixels
|spatio temporal color mixing
combined spatial and temporal mixing
|arrangement of sub-pixels
for additive color mixing
see sub-pixel arrangements 1
see sub-pixel arrangements 2
see sub-pixel arrangements 3
|subtractive color mixing does not require special sub-pixel arrangements
all components (e.g. filters) have to be in the same path of light.
PenTile arrangement, e.g. RGB+White
Each sub-pixel of a display devices must be selected (addressed) in order to be energized in a controlled way.
each individual picture element has electrical connections to the driving electronics.
several picture elements have common electrical connections to the driving electronics,
e. g.. row and column electrodes when the picture elements are arranged in a two dimensional matrix.
|active matrix addressing
active electronic elements added in order to improve selection of picture elements.
|passive matrix addressing
the nonlinearity of the display effect (e.g. LCD, LED)is used to realize the addressing of individual pixels in multiplex addressing. In this mode only a quite limited number of lines can be addressed. In the case of (STN-)LCDs this maximum is at ~240, but at the expense of a considerable reduction of contrast.
|The matrix of active electronic elements can used in transmissive mode of operation (high transmittance required) or a non-transparent active matrix can be used for reflective LCDs (e.g. liquid crystal on silicon (LCOS)).||
Display driving modes
activation of pixels by voltage (e.g. LCD field effects). If the current is low enough this mode may be the basis for displays with very low power requirements (e.g. μW for LCDs without backlight).
activation of pixels by electric current (e.g. LED).
- ^ Louis D. Silverstein, et al., Hybrid spatial-temporal color synthesis and its applications, JSID 14/1(2006), pp. 3–13
- SID - Society for Information Display International Conference Proceedings 1970–2008
- Journal of the Society for Information Display (JSID)
- Display-Metrology & Systems: Publications
- Pochi Yeh, Claire Gu: "Optics of Liquid Crystal Displays", John Wiley & Sons 1999, 4.5. Conoscopy, pp. 139