Electronic visual display

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.

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).

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 ca be displayed (symbols, signs), simple numerals (7-segment layout) or arbitrary shapes can be generated (dot-matrix displays).

Generation 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.

Literature

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