In the case of Augmented Reality, the augmentation is conventionally in real-time and in semantic context with environmental elements, such as sports scores on TV during a match. With the help of advanced AR technology (e.g. adding computer vision and object recognition) the information about the surrounding real world of the user becomes interactive and digitally usable. Artificial information about the environment and the objects in it can be stored and retrieved as an information layer on top of the real world view. The term augmented reality is believed to have been coined in 1990 by Thomas Caudell, an employee of Boeing at the time.
Augmented reality research explores the application of computer-generated imagery in live-video streams as a way to expand the real-world. Advanced research includes use of head-mounted displays and virtual retinal displays for visualization purposes, and construction of controlled environments containing any number of sensors and actuators.
Definition
There are two commonly accepted definitions of Augmented Reality today. One was given by Ronald Azuma in 1997 [2]. Azuma's definition says that Augmented Reality
combines real and virtual
is interactive in real time
is registered in 3D
Additionally Paul Milgram and Fumio Kishino defined Milgram's Reality-Virtuality Continuum in 1994 [3]. They describe a continuum that spans from the real environment to a pure virtual environment. In between there are Augmented Reality (closer to the real environment) and Augmented Virtuality (is closer to the virtual environment).
This continuum has been extended into a two-dimensional plane of "Virtuality" and "Mediality". Taxonomy of Reality, Virtuality, Mediality. The origin R denotes unmodified reality. A continuum across the Virtuality axis V includes reality augmented with graphics (Augmented Reality), as well as graphics augmented by reality (Augmented Virtuality). However, the taxonomy also includes modification of reality or virtuality or any combination of these. The modification is denoted by moving up the mediality axis. Further up this axis, for example, we can find mediated reality, mediated virtuality, or any combination of these. Further up and to the right we have virtual worlds that are responsive to a severely modified version of reality. (at right) Mediated reality generalizes the concepts of mixed reality, etc.. It includes the virtuality reality continuum (mixing) but also, in addition to additive effects, also includes multiplicative effects (modulation) of (sometimes deliberately) diminished reality. Moreover, it considers, more generally, that reality may be modified in various ways. The mediated reality framework describes devices that deliberately modify reality, as well as devices that accidentally modify it.
More recently, the term augmented reality has been blurred a bit due to the increased interest of the general public in AR.
Examples
Commonly known examples of AR are the yellow "first down" lines seen in television broadcasts of American football games using the 1st & Ten system, and the colored trail showing location and direction of the puck in TV broadcasts of ice hockey games. The real-world elements are the football field and players, and the virtual element is the yellow line, which is drawn over the image by computers in real time. Similarly, rugby fields and cricket pitches are branded by their sponsors using Augmented Reality; giant logos are inserted onto the fields when viewed on television. In some cases, the modification of reality goes beyond mere augmentation. For example, advertisements may be blocked out (partially or wholly diminished) and replaced with different advertisements. Such replacement is an example of Mediated reality, a more general concept than AR.
Television telecasts of swimming events also often have a virtual line which indicates the position of the current world record holder at that time.
Another type of AR application uses projectors and screens to insert objects into the real environment, enhancing museum exhibitions for example. The difference from a simple TV screen for example, is that these objects are related to the environment of the screen or display, and that they often are interactive as well.
Many first-person shooter video games simulate the viewpoint of someone using AR systems. In these games the AR can be used to give visual directions to a location, mark the direction and distance of another person who is not in line of sight, give information about equipment such as remaining bullets in a gun, and display a myriad of other images based on whatever the game designers intend. This is also called the head-up display.
In some current applications like in cars or airplanes, this is usually a head-up display integrated into the windshield.
The F-35 Lightning II has no head-up display. This is because all targets are tracked by the aircraft's situational awareness and the sensor fusion is presented in the pilot's helmet mounted display. The helmet mounted display provides an augmented reality system that allows the pilot to look through his own aircraft as if it wasn't there.
