Volumetric display
A volumetric display device is a graphical display device that forms a visual representation of an object in three physical dimensions, as opposed to the planar image of traditional screens that simulate depth through a number of different visual effects. Although first postulated in 1912, volumetric displays are still under development, and have yet to reach the general population. With a variety of systems proposed and in use in small quantities mostly in academia and various research labs, volumetric displays remain accessible only to corporations and the military.
Types of displays
Many different attempts (US Patent Office) have been made to extend the dynamic 2D representation of the cathode ray tube to three dimensions. Volumetric displays fall into the following categories:
Swept-plane
The principle is to have a 2D lighted surface sweep in a circle, creating a volume. The image on the 2D surface (created by projection, LEDs or other techniques) changes as the surface rotates. Due to the persistence of vision humans perceive a volume of light. The lighted surface needs to be translucent.
Emissive volume
This is probably the most 'direct' form of volumetric display. A volume of space is created out of active elements that are transparent in the Off state but are either opaque or luminous in the On state. When the elements or voxels are activated they show a solid pattern within the space of the display. An example of such as display is the Univ. Texas Prototype. Another kind, over lapping with the Laser Display, is the Laser Excited volume display [1][2] where lasers are focused at appropriate points in a block of optically active material. The focused action of the lasers excites the atoms in the optically active material and causes them to glow.
Varifocal mirror
- U.S. patent 4,607,255 — Three Dimensional Display Using a Varifocal Mirror
Laser
Uses two infrared lasers to stimulate atoms in a special glass, which then re-emit visible photons with the energy of the two infrared photons combined.
Laser plasma
Uses a focused pulsed infrared laser (about 100 pulses per second; each lasting a nanosecond) to create balls of glowing plasma at the focal point in normal air.