display technology A display device is an output device for presentation of information in visual or tactile form (the latter used for example in tactile electronic displays for blind people). When the input information that is supplied has an electrical signal the ...

parlance, viewing angle is the

angle In Euclidean geometry, an angle is the figure formed by two rays, called the '' sides'' of the angle, sharing a common endpoint, called the ''vertex'' of the angle. Angles formed by two rays lie in the plane that contains the rays. Angles ...

at which a display can be viewed with acceptable visual performance. In a technical context, the angular range is called

viewing cone The viewing cone refers to the effective viewing directions of an LCD display, as seen from the eye. This collection of angles resembles a cone. The concept has been introduced as an international standard ISO 13406-2, which defines it as the ''r ...

defined by a multitude of viewing directions. The viewing angle can be an angular range over which the display view is acceptable, or it can be the angle of generally acceptable viewing, such as a twelve o'clock viewing angle for a display optimized or viewing from the top. The image may seem garbled, poorly saturated, of poor contrast, blurry, or too faint outside the stated viewing angle range, the exact mode of "failure" depends on the display type in question. For example, some

projection screen A projection screen is an installation consisting of a surface and a support structure used for displaying a projected image for the view of an audience. Projection screens may be permanently installed, as in a movie theater; painted on the ...

s reflect more light perpendicular to the screen and less light to the sides, making the screen appear much darker (and sometimes colors distorted) if the viewer is not in front of the screen. Many manufacturers of projection screens thus define the viewing angle as the angle at which the

luminance Luminance is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. It describes the amount of light that passes through, is emitted from, or is reflected from a particular area, and falls with ...

of the

image An image is a visual representation of something. It can be two-dimensional, three-dimensional, or somehow otherwise feed into the visual system to convey information. An image can be an artifact, such as a photograph or other two-dimensio ...

is exactly half of the maximum. With LCD screens, some manufacturers have opted to measure the contrast ratio, and report the viewing angle as the angle where the contrast ratio exceeds 5:1 or 10:1, giving minimally acceptable viewing conditions. The viewing angle is measured from one direction to the opposite, giving a maximum of 180° for a flat, one-sided screen. A display may exhibit different behaviour in horizontal and vertical axes, requiring users and manufacturers to specify maximum usable viewing angles in both directions. Usually the screens are designed to facilitate greater viewing angle in horizontal level, and smaller angle in the vertical level, should the two of them be different in magnitude. The viewing angle for some displays are specified in only a general direction, such as 6 o'clock or 12 o'clock. Early LCDs had strikingly narrow

s, a situation that has been improved with current technology. Narrow

s of some types of displays have also been used to bring a measure of

security" \n\n\nsecurity.txt is a proposed standard for websites' security information that is meant to allow security researchers to easily report security vulnerabilities. The standard prescribes a text file called \"security.txt\" in the well known locat ...

in businesses, where employees handle private information in the presence of customers, banks being one example. Rectangular filters fitting to the computer monitors have also been sold as accessories for this purpose.

LEDs

LEDs are measured so that the line along half the viewing-angle from directly forward is half the brightness as at directly forward.

References

{{Reflist Display technology