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 ...

parlance, viewing angle is the

angle In Euclidean geometry, an angle can refer to a number of concepts relating to the intersection of two straight Line (geometry), lines at a Point (geometry), point. Formally, an angle is a figure lying in a Euclidean plane, plane formed by two R ...

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

viewing cone The viewing cone is the set of effective viewing directions of a Computer monitor, visual display, as seen from the eye. This collection of angles resembles a generalized cone. The concept has been introduced as an international standard ISO 13406 ...

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 on a wall, as in a movie theater, mounte ...

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 wit ...

of the

image An image or picture is a visual representation. An image can be Two-dimensional space, two-dimensional, such as a drawing, painting, or photograph, or Three-dimensional space, three-dimensional, such as a carving or sculpture. Images may be di ...

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 behavior 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 angles at the horizontal level, and smaller angles at the vertical level, should the two of them differ in magnitude. The viewing angle for some displays is specified in only a general direction, such as 6 o'clock or 12 o'clock. Early

LCD A liquid-crystal display (LCD) is a flat-panel display or other electronically modulated optical device that uses the light-modulating properties of liquid crystals combined with polarizers to display information. Liquid crystals do not em ...

s 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 Security is protection from, or resilience against, potential harm (or other unwanted coercion). Beneficiaries (technically referents) of security may be persons and social groups, objects and institutions, ecosystems, or any other entity or ...

in businesses, where employees handle

private information Privacy (, ) is the ability of an individual or group to seclude themselves or information about themselves, and thereby express themselves selectively. The domain of privacy partially overlaps with security, which can include the concepts of a ...

in the presence of customers, banks being one example. Rectangular privacy filters fitting to the computer monitors have also been sold as accessories.

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