Heads-up display

Heads-up displays (HUD) are a way to provide additional information to a pilot, vehicle driver, surgeon, or industrial control operator, without requiring they take their eyes away from the primary objects they much watch: the positions of other vehicles, obstacles, or the device their hands are manimpulating. HUD implementation can be fairly simple: a semitransparent mirror is placed, at an angle, in the user's field of view. A device above the mirror projects the additional information onto the surface of the mirror, so that information is superimposed on the user's normal visual field.

Human factors need to be considered carefully in implementing systems. It would be unusual for a person to be able to put on the HUD without training, and make immediate operational use of it. The user has to learn to understand what is an enhancement to vision, even if it is something as apparently intuitive as putting a gunsight onto a target. When the HUD adds alphanumeric information, the user has to avoid information overload, and imappropriate focus on the additional information. Think of the new driver, so concerned with violating the speed limit, that the speedometer becomes his center of attention, distracting him from avoiding a collision with another car.

HUD are characteristically part of the human interface in fighter aircraft starting at the fourth generatio. In surgery, they can let the surgeon focus on the operative field, but simultaneously have X-ray or other medical imaging superimposed on the real patient.