Head-Up-Displays (HUD) are featuring more and more frequently in both current and future generation automobiles. One primary reason for this upward trend is that head-up displays are said to improve auto safety significantly.  Another reason is that the installed cost of these instruments has dropped enough so that today, not only luxury vehicles are equipped with this device; HUDs now are finding their way into economy cars as well.

The HUD projects all relevant auto and traffic info “into”, not merely “onto”, the windshield. This allows the driver to maintain a view of the street scene, rather than requiring vision to be diverted to the instrument panel. The HUD “picture” is projected toward the driver’s forward field of view, 2.2 meters into the windshield. Information such as speed, autopilot data, all warning indicators, directions, etc., are displayed. The latest generation HUDs even show approaching traffic signs. 

A head-up display consists basically of a light projector and a special kind of windshield made of two sheets of glass.  The projector is built into the dashboard in front of the driver. Between the sheets is a special integrated layer that can receive and display the information sent by the projector. The control electronics sit in the engine compartment. 

To guarantee full functionality, a system test during assembly is essential. A simple visual inspection is inadequate because varying environmental light conditions would negatively impact the results. Thus, the HUD cannot be calibrated properly.