Holographic projector
From Memory Alpha, the free Star Trek reference.
A holographic projector (or holographic emitter) is a device used to create holograms. They do this by manipulating photons and force fields to create a realistic, but virtual image. This technology is used in the recreation, labor and medical fields.
A rapid rise in the use of holographic projectors occurred in the late 24th century. In 2364, they were only installed in specialized rooms onboard Federation starships called holodecks. When the USS Voyager was commissioned in 2371, holographic projectors were installed in ship's sickbay as well. This was in order to allow the use of the Emergency Medical Hologram. In 2373, Starfleet tested a device called a holo-communicator that employed the use of holographic projectors. These were installed on bridges of starships including the USS Defiant and in Captain Benjamin Sisko's office aboard Deep Space 9. Launched in early 2374, the USS Prometheus was equipped with holographic projectors on every deck to allow free range of movement of the EMH. (TNG: "Encounter at Farpoint", DS9: "For the Uniform", "Doctor Bashir, I Presume", VOY: "Caretaker", "Message in a Bottle")
Aboard Deep Space 9, Quark had several holosuites in the upper level of his bar that presumably use holographic projectors. (DS9: "Dramatis Personae")
Rurigan used a holographic projector to create holograms of those he had lost during the Dominion's attack on Yadera Prime in the 2340s. It had begun to fail in 2370, although Jadzia Dax and Odo were able to help him repair it. (DS9: "Shadowplay")
