A holographic projector (also called a holographic emitter or holo-emitter for short) was a device used to project holograms. By the 2360s, holographic projectors were installed aboard Starfleet starships in specialized areas called holodecks. (TNG episode: "Encounter at Farpoint") By the 2370s, ships such as the USS Voyager had holo-emitters installed in their sickbays to enable the use of the Emergency Medical Hologram. (VOY episode: "Caretaker")