How Heads Up Display (HUD) Works

POSTED BY , UPDATED ON October 9th, 2019

How Heads Up Display (HUD) Works

For pilots, military personnel and for other professionals who require concentration on a visual subject, Heads Up Display (HUD) is becoming more and more familiar. In practice, HUD allows the user to have a clear vision of a subject whilst simultaneously displaying information such as speed, distance or fuel level. The name Heads Up Display comes from the notion that a pilot would be able to control their plane and view information at the same time whilst their head is positioned to enable them to look up and forwards, as opposed to looking down at a display.


How Does it Work?

There are three main pieces of the HUD:

  1. a projector
  2. a combiner
  3. a computer

The projection unit of the HUD uses a convex lens (curved outwards like a bowl) or a concave mirror (curved inwards, like the inner part of a bowl) with a liquid crystal display at the helm.

The combiner is a flat piece of glass angled and located at the front of the viewer. It exists to redirect the projected image from the projector which means users such as pilots can view a scene and data at the same time and with their head in the same position. The computer provides the interface through which the data is displayed from the HUD and the projection unit itself.


Other Uses and Design

HUD can also be used within a head-mounted display on a helmet. This form of HUD allows the user to move freely, looking at different subjects whilst the data is projected in front of them, with no fixed location for the data to be projected onto.

Over time, the displays have naturally progressed in design and functionality. From first providing users with an image on a phosphor screen (with a coating which deteriorated over time), to an HUD with a solid state light source such as an LED (which can be seen on commercial aircrafts), to the optical waveguides in the third generation design which didn’t require a projection screen yet produced images directly in front of the computer.

The HUD has come a long way and now uses a scanning laser to display images and now even videos via the system.


The Future

Seen in films such as The Terminator, HUD systems that project information directly onto the users’ retinas with lasers are also being looked into. Swimming goggles and scuba diving masks have also been looked at, where the HUD would display information inside the goggles or mask.