Holographic projector

A holographic projector (or holographic emitter) was a device used to create holograms. They did this by manipulating photons and force fields to create a realistic, but virtual image. This technology was used in the recreation, labor, and medical fields.

A rapid rise in the use of holographic projectors occurred in the late 24th century. In the early 2360s, they were installed in specialized rooms called holodecks on board Federation starships, and were also available in large tabletop models or smaller, integrated desktop models. 

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 (2370), and in Captain Benjamin Sisko's office aboard Deep Space 9. Launched in early 2374, the USS Prometheus (Prometheus class) was equipped with holographic projectors on every deck to allow free range of movement of the EMH. 

Aboard Deep Space 9, Quark had several holosuites in the upper level of his bar that presumably use holographic projectors. 

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. 

In 2371, during The Doctor's delusions on Voyager's holodeck, a hologram of B'Elanna Torres informed The Doctor that she had installed holo-projectors in main areas of the ship, such as the bridge and engineering, as well as the mess hall. 

In 2372, Lieutenant B'Elanna Torres and Ensign Harry Kim installed a holo-projector in Voyager's engine room to project The Doctor there. Unfortunately, the holo-projector significantly shortened The Doctor and the project was abandoned. 

In 2373, Rear Admiral Bennett presided over the hearing on Dr. Julian Bashir's genetic enhancement on Deep Space 9 via a holo-projector. 

In 2374, Quark created a hologram of Morn to replace him while he was away, so his business would not suffer. He was unable to afford an interactive holoprojector to make Morn speak, which he felt was better, since Morn never shut up. 

In 2378, Lieutenant Commander Tuvok shot one of the holo-emitters with a phaser in Voyager's sickbay to prevent The Doctor from escaping, after it was discovered he had incapacitated members of the crew and assumed their identities. 

The Narada, a 2387 Romulan mining vessel, had a holographic projector which could display images chosen by hand. After being transported to 2233, Ayel displayed images of the Jellyfish'' and Ambassador Spock to Richard Robau, who replied he was unaware of them or their location. Twenty-five years later in this alternate reality, Nero projected an image of his deceased wife to, while trying to justify his genocide of the Vulcan people.''