ABSTRACT
During early military head-up display (HUD) development, it was found that pilots using HUDs could operate their aircraft with greater precision and accuracy than they could with conventional flight instrument systems. Once low-visibility operations were successfully demonstrated using a HUD, regional airlines opted for this technology, as an alternative to a fail passive auto land system, to help maintain their schedules when the weather fell down CAT II minimums, and to improve situational awareness. The HUD requires a very bright image source that is usually monochrome green. In early systems, this was a Cathode Ray Tube (CRT) with the symbols drawn using analog signals that move a bright spot around the CRT screen. The optics in HUD systems are used to “collimate” the HUD image so that essential flight parameters, navigational information, and guidance are superimposed on the collimated outside world scene.
