The term "Augmented Reality" may have been coined by Thomas Caudell less than 20 years ago. It implies a computer-generated enhancement superimposed upon something ‘real.’ Real scenes, be they static, like a building, or active, like a football game, have transparent computer-generated data or images placed over them. Typically, the layer is informational, such as the line marking the first down during a football game telecast or more advanced computational rendering such as CFD [Computational Fluid Dynamics] display of turbulent air flow on NASCAR races.
 
Augmented reality in front of millions of TV viewers: Display of turbulent airflow with "clean" and "dirty" air
Augmented reality in front of millions of TV viewers: Display of turbulent airflow with "clean" and "dirty" air

Two ends of the spectrum have been identified. A pioneer in the field of Augmented Reality, Ronald Azuma, says that AR [Augmented Reality] combines real and virtual, is interactive in real time, and is registered in 3D. Paul Milgram and Fumio Kishino defined Milgram’s Reality-Virtuality Continuum as "one that spans from the real environment to a pure virtual environment". Differentiating is like splitting hairs ? you get Augmented Reality which aligns itself more with the real environment or you can have Augmented Virtuality which leans more towards the virtual environment.

ISMAR 2009, the International Symposium on Mixed and Augmented Reality is continuing to explore AR over the course of this week. The concept goes back a quarter of a century beginning with a cinematographer, Morton Heilig, who in 1962 created a motorcycle simulator called Sensorama that produced visuals, sound, vibration and smell. Almost 15 years later, Myron Krueger created Videoplace where users could interact with virtual objects. Another decade passed before Jaron Lanier coined the phrase "virtual reality." Ten more years pass before Hirokazu Kato developed and demonstrated the ARToolKit.
The G1 Android phone with Wikitude AR Travel Guide brought widespread use to the general public in late 2008. In 2009, Saqoosha added FLARToolkit to Adobe Flash, and AR moved into the web browser.
Applications of Augmented Reality are endless. Entertainment, education, industry, tourism, navigation, military are just a few of the areas that will feel the affect of AR. The future looks like the set of a Star Trek episode ? holographic images, virtual clocks on the wall, and outdoor scenes projected into a shut-in’s room.

Today, AR is already integrated into desktop and mobile environments, and can be experienced using headsets like Canon’s MR Aquarium or visors like Arcane Technologies Mirage AR System. Movies have gotten into the act. Robert Downey Jr. designed his super powered suit in Iron Man with augmented reality. The concept is becoming a popular adjunct in books from The Risen Empire to the Halting State.

If you want to get your own feet wet with this exciting concept, ARToolKit is an open source, free application that can also be licensed for commercial use. Since 1998, Augmented Reality has been the focus of conferences worldwide in such cities as San Francisco, California; Nara, Japan; Darmstadt, Germany, and Cambridge, England. The current International Symposium on Mixed and Augmented Reality bash is being held as we write this in Orlando, Florida, October 19-23, 2009.