User:Panjasan/Electronic Visual Displays

Electronic Visual Displays

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.

Electronic Visual Displays - Classification

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 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).

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	retinal projection (with or without combiner) e.g. head mounted display

Layout of Picture Elements

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 Colors

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
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 Modes

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 Modes

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).

References

• SID - Society for Information Display International Conference Proceedings 1970 - 2008
• Journal of the Society for Information Display (JSID)
• Display-Metrology & Systems: Publications

Literature

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

Category:Physics Category:Optics Category:Vision Category:Display_technology