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A display device is an output device for presentation of information for visual or tactile reception, acquired, stored, or transmitted in various forms. When the input information is supplied as an electrical signal, the display is called electronic display. Electronic displays are available for presentation of visual and tactile information.

Tactile electronic displays are usually intended for the blind or visually impaired. They use electro-mechanical actuators to dynamically update a tactile image (usually of text) so that the image may be felt by the fingers (refreshable Braille display).

Common applications for electronic visual displays used to be television sets or computer monitors, but these days electronic visual displays tend to be ubiquitous as interface for large amounts of visual information in mobile computing applications and portable information communication technology devices.

ClassificationEdit

Electronic visual displays generate visual information according to the electrical input signal (analog or digital) either by generation of light (then they are called active displays) or, alternatively, by modulation of available light during the process of reflection or transmission (light modulators are called passive displays).

Electronic Visual Displays
Active Displays Passive Displays
visual information is provided by generation of light. visual information is provided by modulation of light.
Effect LCD + backlight (this combination is considered to be an active display) LCD (liquid crystal display)
Example LCD TV screen, LCD computer monitor LCD watch (reflective)
see LCD classification
Effect Cathodoluminescence Electrophoresis
also see Electronic paper
Example cathode ray tube (CRT)
field emission display (FED)
vacuum fluorescence display (VFD)
surface conduction electron emitter display (SED)
Research & Manufacturing:
eInk Electronic Paper Displays
SiPix Microcup Electronic Paper
Effect Electroluminescence Electrochromism
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
Effect Photoluminescence Electrowetting
Example plasma display panel (PDP) Research & Manufacturing:
Liquavista
Effect Incandescence
Electromechanical Modulation
Example Numitron, a 7-segment numerical display tube Numitron website flap display
flip-disk display
digital micromirror device (DMD)
interferometric modulation device (IMOD)
FTIR (unipixel)
telescopic pixel display

Display Mode of ObservationEdit

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.

Display Modes of Observation
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 build 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 ElementsEdit

Depending on the shape and on the arrangement of the picture elements of a display either fixed information ca be displayed (symbols, signs), simple numerals (7-segment layout) or arbitrary shapes can be generated (dot-matrix displays).

Layout of Picture Elements
segmented displays
characters, numbers and symbols of fixed shape (may be multiplexed addressed).
The following layouts are well known:
seven segment layout
fourteen segment layout
sixteen segment layout.
dot-matrix displays
sub-pixels are arranged in a regular 2-dimensional array
(multiplex addressing required). Arbitrary shapes can be generated and displayed.

Generation and Control of ColorsEdit

Colors can be generated by selective emission, by selective absorption, transmission or by selective reflection.

Color Generation and Control
additive mixing
primary colors add up to produce white light
subtractive mixing
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[1]
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.
Examples:
stripe
delta-nabla
pentile arrangement, e.g. RGB+White

Addressing ModesEdit

Each sub-pixel of a display devices must be selected (addressed) in order to be energized in a controlled way.

Addressing Modes (selection of picture elements)
direct addressing
each individual picture element has electrical connections to the driving electronics.
multiplexed addressing
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.
  • thin-film diodes (TFDs)
  • thin-film transistors (TFTs)
    • amorphous silicon (a-Si)
    • polycrystalline silicon (p-Si)
    • monocrystalline silicon
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. LCOS: liquid crystal on silicon).|

Display Driving ModesEdit

Driving Modes (activation of picture elements)
voltage driving
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).
current driving
activation of pixels by electrical current (e.g. LED).

See alsoEdit

ReferencesEdit

  1. Louis D. Silverstein, et al., Hybrid spatial-temporal color synthesis and its applications, JSID 14/1(2006), pp. 3–13

LiteratureEdit

  • ISO 13406-2
  • Pochi Yeh, Claire Gu: "Optics of Liquid Crystal Displays", John Wiley & Sons 1999, 4.5. Conoscopy, pp. 139

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