So after seeing the demo for the hololens and knowing it can only be seen by the wearer of the goggles I had questions about real holograms. I also watching a video of a hologram that requires a single users eyes to be tracked. i got curious. Do actual holograms visable by a group or crowd of people to be seen simultaneously exist? And im not talking about steam jets either. Has technology managed to develop actual holograms visable by a crowd or are they all only visable by a single person or with parifirals on the eyes?