There have been a few presentations now in which a live stage performance was simulated by what was described as a hologram. The most recent example of this was the Michael Jackson "appearance".
How are these done? The classic hologram I am familiar with uses only one wavelength of laser light and constructs an interference pattern on a photographic plate, where it is recorded. When the same light source illuminates the developed plate, the interference pattern effectively reconstitutes the original light paths to reproduce the effect of looking through a window (the plate) to view the original object as if it was illuminated in monochromatic light (that of the laser).
The stage presentations obviously differ in that they are in full colour, and they are moving in real time... not to mention the overall physical size.
So, what's different about the way these presentations are prepared and executed that allows them to render in such a life-size and life-like manner? Are they truly holograms? Do they employ the same principles of physics as a "classic" hologram? Are they actually something entirely different and only incorrectly labelled as holograms?