Virtual reality
Around the same time, Douglas Engelbart used computer screens both as input and output devices. In 1968, Ivan Sutherland, with the help of many students including Bob Sproull, created what was widely considered to be the first head-mounted display (HMD) system for use in immersive simulation applications. It was primitive both in terms of user interface and realism, and the HMD to be worn by the user was so heavy that it had to be suspended from the ceiling. The graphics comprising the virtual environment were simple wire-frame model rooms. The formidable appearance of the device inspired its name, The Sword of Damocles.
Daniel J. Sandin
The first CAVE was invented by Carolina Cruz-Neira, Daniel J. Sandin, and Thomas A. DeFanti in 1992. This is an immersive system that became the standard for rear projection-based Virtual Reality systems. The normal full system consists of projections screens along the front, side and floor axes, and a tracking system for the "user". Although they used the recursive acronym Cave Automatic Virtual Environment for the CAVE system, the name also refers to Plato's "Republic" and "The Allegory of the Cave" where he explored the concepts of reality and human perception.