A holographic interface is a computer input method that utilizes a projected image instead of a physical device. Holographic interfaces are popular on computer systems that see a variety of uses, as well as those that require extremely complex inputs. Because they are more expensive than physical interfaces, they tend to be restricted to wealthy areas.
Technology
Holographic interfaces utilize holoprojectors to create a 3d image in whatever configuration is most appropriate to the program used. Because the image is constructed only of light, the configuration can be as simple or complex as needed, and easily scaled to a size that the user finds comfortable. Additionally, it can be dynamically reconfigured, so a user can quickly switch from a simplified interface to a more involved one as need.
Interaction with the image is recorded via sensors in the projector, not through direct manipulation of the hologram. These sensors can record the precise location of the user's fingers (or other appendages for interfaces that utilize them), enabling pinpoint control.
Uses
Holographic interfaces are popular in holovid games, as well as with computers in government offices. Though the projector has a more expensive up-front cost than a physical interface device, because they can be easily reconfigured to any layout through software, and do not require swapping and storage as with physical interfaces, they can be less expensive in the long run.
Most pieces of software include code that creates a customized holographic interface for those with projectors. Many are written with holographic interfaces in mind, utilizing complicated hacks to enable older interface methods to still work.