Audi has unveiled the latest secret weapon for its Le Mans endurance racers - a digital rear view mirror.

Obviously in a road car such technology would be a superfluous frippery, but in a closed LMP sports prototype racer, with no rear window, it's an innovative and safety-enhancing tool.

"In the past, our drivers had to strictly rely on the outside mirrors when looking rearward, yet the rear end and the rear wings plus the vibrations that occur at high speeds significantly limit the field of vision of these mirrors," says Dr Wolfgang Ullrich, Audi's motorsport chief.

The mirror uses so-called AMOLED technology, which is very high resolution and which Audi says gives a better view than a conventional mirror.

"The operation of the mirror is weather-neutral," says Dr Ullrich. "By contrast, when using outside mirrors, heavy water spray severely impairs the driver's field of vision when it rains.

"For the new digital mirror, we worked out various day and night driving modes. Even when a rival approaches from the rear with high-beam headlights the image is superb and not just a glaring light spot."

The display's camera is a few millimetres wide and sits on the roof of the R18 LMP car, sending a real-time image to the mirror.

Audi has raised the possibility of a production version - it's feasible the mirror could appear in something low and with obscured rear vision, like the next-generation R8. Or even a future Lamborghini.