Head-up Displays Information
Head-ups displays (HUDs) superimpose data on the field of view of a vehicle operator. This allows the operator to maintain his or her focus on vehicle control while being fed live data about the vehicle, such as speed, direction, and navigation. In aerospace applications, HUDs display altitude, flight paths, weapon systems, and other flight info. Some automotive applications utilize HUDs to provide drivers with traffic information and vehicle reports. HUDs consist of a projector unit to create a visual display of the data; a transparent combiner or specialty windshield that displays the projector imaging; and a video generation computer. HUDs are either dash- or helmet-mounted (HMD).
The HUD displays information on a combiner or vehicle windshield. A combiner is a small, transparent plastic disc or windshield-affixed film that acts as a mirror to reflect the HUD's information. The benefit of using a combiner instead of the windshield is that the optical path is easier to position using a combiner, which allows for optimization of visual properties. Combiner HUDs are cheaper and more compact than projector types, which make them better suited for smaller vehicles; they can also be added as an aftermarket product. Projector HUDs that use the windshield require specially constructed windshields but these HUDs offer a fully-transparent data display on the entire windshield. These systems are more sophisticated and expensive and are an integral part of vehicle design that is implemented by the OEM.
HUDs have transitioned from CRT-based to laser-based technologies with features like:
HUDs first appeared during World War II to help military pilots with navigation and targeting; this generation relied on reflective CRT displays. Technology progressed to solid-state light sources, such as LEDs that are modulated by an LCD screen, which are still used on commercial aircraft. Optical waveguides replaced projected images on third generation HUD devices. Modern HUDs use scanning lasers to display images and video, or utilize an alternative micro-imaging technology such as LCD, liquid crystal on silicon (LCoS), digital micro-mirrors (DMD), and organic light-emitting diode (OLED).