Emergency Medical Hologram
The Emergency Medical Hologram (abbreviated: EMH) is a sophisticated hologram developed in the early 2370s by Starfleet and used on most Federation starships in the late 24th century. The first starship to be equipped with an EMH is the USS Voyager. The formal name of the program is EMH Program AK-1 Diagnostic and Surgical Subroutine Omega-323.
It was developed by Dr. Lewis Zimmerman at the Jupiter Station Holoprogramming Center as the embodiment of modern medicine. The EMH Mark I is programmed with 5 million possible treatments from the collective information of 2000 medical references and the experience of 47 individual medical officers. The EMH is also supplemented with contingency programs and adaptive programs to in essence learn while serving as a supplement of a normal medical staff in cases of emergency.
Some biological Starfleet doctors objected to the use of the EMH.
The Doctor, a Mark I, originally objected to being the replacement for the entire medical staff of Voyager as the EMH program was only meant to function for a maximum of 1500 hours (62.5 days); after this time, memory degradation would occur. Fortunately, with the help of his colleagues, his program was corrected.
As of 2376, there have been four versions of the EMH, called Mark I, II, III and IV. The Mark I's outer appearance was a copy of its inventor, Dr. Zimmerman. However, as the Mark II was released, the first version soon seemed obsolete and, thus, was reconfigured to scrape plasma conduits or to mine dilithium ore.
Furthermore, the patterns of behavior of the following versions were designed to be more pleasant and courteous and its outer appearance was changed. In addition to that, new ship designs like the USS Prometheus enabled full mobility for the EMH as the whole ship was outfitted with holographic projectors.
After the EMH Mark II supplanted the "inferior" Mark I, the only remaining versions to fulfill their original programming were aboard the USS Voyager and the USS Equinox, which were both stranded in the Delta Quadrant and had to implement the emergency holograms for extended periods of time. However, the crew of the Equinox removed the program's ethical subroutines in order to be able to count on their EMH as a more unquestioning crew member. In 2376, the Equinox, along with its EMH, was destroyed, so Voyager's program, "The Doctor", was now the only Mark I still operating as an EMH. Nevertheless, Voyager's EMH developed a distinct personality over the ship's seven years-long journey back to the Alpha Quadrant, so it finally received all privileges and rights of a living person. Furthermore, Voyager's EMH was able to leave sickbay or the holodeck and to roam free with the help of the mobile emitter (originating from 29th century technology).
Though Mark II and III units are still common, they are slowly being phased out in favor of the Mark IV, which is programmed with a larger number of treatments and has a longer maximum operating time (as well as each being programmed with a distinct appearance and personality) - see the USS Tokyos Rain, USS Casey's Mark Green, USS Hyperion-D's Mindy, and Starbase 3's Meyrin Hawke (who was copied by the crew and modified into a Supplemental Holographic Bartender for service aboard the USS Endurance.
Mechanics
The EMH is an empty shell with nothing beneath the apparent surface to avoid wasting computer power simulating unnecessary internal organs. Furthermore, EMH's are not equipped with reproductive organs.
Holodecks use omnidirectional holographic diodes. A sickbay is fitted with a system of OHDs that project an image of the EMH. Each projects a complete image. Visible portions change as the hologram moves, creating an illusion of fluid motion.
Magnetic containment fields allow the EMH to interact with physical objects. These force fields move as the EMH moves to create the appearance of solid matter. The containment fields can be shut off, allowing objects and people to pass through him.
Similar OHDs and magnetic fields are added to other parts of a ship, allowing the hologram to leave sickbay.
An EMH's cohesion can range from solid to intangible. He appears human in other ways.
See also
- Administrative Medical Hologram
- Long-term Medical Hologram
- Emergency Command Hologram