See the light

A lightweight, holographic head-up display has been developed for small planes. Berenice Baker reports

A head-up-DISPLAY (HUD) system that generates critical flight data within a glass surface has been designed for small aircraft.

The technology, called Q-HUD from BAE Systems, is unlike current HUD systems that use a bulky overhead projector to display information onto glass.

Q-HUD manipulates light using holographic waveguides so that the images appear in the combiner (the semi-transparent display in front of the pilot), rather than being projected onto it. This means it takes up considerably less room in the cockpit, cuts out 50 per cent of the weight of traditional equipment and costs less than traditional systems.

‘The optics arrangement in traditional HUDs is very complex, meaning it can only be used in a big cockpit,’ said Paul Childs, BAE Systems’s technology lead on the project. ‘In commercial aircraft, it sits close to the pilot’s head with geometric constraints, which means it has to be fitted to a particular orientation.

‘With Q-HUD, we’re effectively injecting the image directly into the combiner, allowing us to remove those optics, reduce weight, size and power consumption and produce a small form factor that gives us the ability to put it into any orientation the pilot wants and fit it to smaller aircraft.’

BAE Systems currently manufactures traditional HUDs for commercial airliners such as Boeing and Airbus. Q-HUD could extend the market into civil fixed-wing aircraft such as those made by Dassault, Bombardier and Gulfstream. It is now being refined and tested and the company aims to have it fitted in aircraft in 2010.

The technology for Q-HUD was first used in a 40mm x 40mm helmet-mounted display dubbed Q-Sight, which BAE Systems developed four years ago for dismounted soldiers. The technology was further developed and the display size was expanded to a glass size that is compatible with a HUD. Some of the early research was done in collaboration with Cambridge University.

The system consists of two sheets of glass with a holographic diffraction grating in the middle. The image for the pilot information symbols is injected at exactly a right angle to cause total internal reflection within that glass. The image propagates down the glass and, every time it is incident upon the hologram, it releases a pinpoint of light that is replicated horizontally and vertically down the glass. Since the image is collimated, consisting of light beams that are effectively parallel, the eye brings them together into one single image.

Current HUD systems consist of an overhead unit that acts as a monitor that feeds images from a symbol generator or a HUD computer and the combiner onto which it is projected. Q-HUD’s configuration would allow the back-end electronic elements to be separated and installed elsewhere, reducing the size and cabin intrusion of the overhead unit. The simpler optics would make it cheaper, too.

Q-HUD can interface with infrared sensors to offer pilots enhanced vision capability in poor-visibility conditions and it can also display video imagery on the combiner. According to BAE Systems, this means pilots using it will have enhanced situational awareness similar to that of commercial pilots. It claimed the result could be better safety for the entire industry.

Berenice Baker