Charles is not the only one with distinctive ears

The eyes are not the only windows of the soul. Research by a team of scientists is seeking to confer equal status on the ears too, at least as far as identifying individuals is concerned.

Experts at the Image, Speech and Intelligent Systems research group at Southampton University have devised a way to automatically analyse the shape of an ear and pick out its owner from a database.

They believe it could be used for security, perhaps in combination with other biometrics systems such as face recognition or iris scanning. It might be particularly useful in the military, where hair is kept short.

Compared with eyes, ears present a relatively large target for a camera to image, and they do not alter much with age or expression as they are made from cartilage.

The automatic ear recognition technique was unveiled last week by David Hurley, who is in charge of the project, at a symposium on visual biometrics organised by the Institution of Electrical Engineers.

"This appears to offer a simple way of transforming a complex shape, such as an ear, into a simple set of data and doing so in a repeatable and reliable way," said Mr Hurley.

The technique does this through a mathematical trick called "force field transformation", which involves a computer analysis of an image of the ear that has been captured by a camera.

Every pixel in the picture is then treated as if it exerts a gravitational pull on every other, with a force related to its brightness.

Peaks and troughs in the notional gravitational field are then logged and compared with a catalogue of ear data to find a match.

This makes the storage of data much easier and the speed of comparison much faster than if the entire image was used.

Mark Nixon, who is supervising the project, said this research could be developed into a far more useful system, and there were rumours that the American military has been exploring similar techniques.

Among its advantages over other approaches was the fact that the size of the ear or its distance from the camera did not affect the analysis.

"Our technique is scaling invariant so size does not matter - Prince Charles can rest easy," Dr Nixon said.