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.
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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).
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.
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 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).
Emission and control of colors
Colors can be generated by selective emission, by selective absorption, transmission or by selective reflection.
Addressing modes
Each sub-pixel of a display devices must be selected (addressed) in order to be energized in a controlled way.