Starting in the early 2000s, flat-panel displays began to dominate the industry, as cathode-ray tubes (CRT) were phased out, especially for computer applications. Starting in the mid 2010s, curved display panels began to be used in televisions, computer monitors, and smartphones.
Types
There are various technologies used for electronic visual displays:
An overhead projector can be considered a type of electronic visual display.
Additionally, CRTs were widely used in the past and microLED displays are under development.
Classification
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 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
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).
Dot-matrix displays 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.
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 device 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.
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 be 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
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 electric current (e.g. LED).
