First virtual reality (VR) headset
Ivan Sutherland, Bob Sproull
first first
United States (Salt Lake City)

The first virtual reality (VR) headset was the "Sword of Damocles", a system developed by computer-graphics pioneer Ivan Sutherland and his student Bob Sproull (both USA) at the University of Utah in 1968. Its name was a reference to the appearance of the headset, which consisted of two soda-bottle-sized cathode ray tubes mounted on either side of the user's head, with mirrors to project the image in front of their eyes. The whole set up was so heavy that the headset had to be suspended from the ceiling (like the mythical sword of Damocles). The most important element of Sutherland and Sproull's invention was not the display, however, but what it displayed. The headset showed wire-frame 3D environments (simple square rooms and shapes) generated by a computer. When the operator turned their head, sensors on the headset would relay this information to the computer, which would redraw the 3D model to adjust for the change of perspective. This redrawn model was then clipped by two independent display processors, which passed the images to the user. Although very slow by modern standards, it was reportedly close enough to real-time to give a convincing impression of standing inside a virtual environment.

The Sword of Damocles was also the first AR headset, capable of displaying information onto clear reflectors in front of the user's eyes. Sutherland explains this possible mode of operation in his paper on the invention:

"Half-silvered mirrors in the prisms through which the user looks allow him to see both the images from the cathode ray tubes and objects in the room simultaneously. Thus displayed material can be made either to hang disembodied in space or to coincide with maps, desk tops, walls, or the keys of a typewriter."