"Head-Up Display"

Head-up display - Wikipedia, the free encyclopedia. Collimation – The projected image is collimated which makes the light rays parallel. Because the light rays are parallel the lens of the human eye focusses on infinity. Images on the HUD combiner are perceived as existing at or near optical infinity. This means that the pilot's eyes do not need to refocus to view the outside world and the HUD display...the image appears to be "out there", overlaying the outside world.