Hologenerator

A hologenerator was a device used to create holographic imagery. It was similar in function to holodecks, holosuites, and the EMH mobile emitter. Some devices of this sort used omicron particles to create holograms. Holograms projected by Federation hologenerators could be interfered with by Borg lasers. 

Federation anthropological teams used hologenerators in field studies of pre-warp civilizations. 

In 2369 Quark tried to expand his holosuite level in his bar to use more space for more holosuites, which were all connected to the same hologenerator.