The left lens of the glasses is like that of a pair of bifocal spectacles. However, instead of having two areas of different strength, a thin wedge-shaped prism is built into the left edge of the lens.
While the longest side of the prism faces the wearer's eye, the shortest side faces outwards on the left side.
The glasses also involve the use of a small LED display, which is powered by a polymer battery inside its left arm. This LED display projects an image into the prism from the side.
Before reaching the wearer's eye, the image is reflected twice inside the prism.
Mike Hazel, an optics engineer at Cambridge Consultants, one of the two firms responsible for the development of the technology, says that most head-mounted displays like those found in a fighter pilot's helmet are typically heavy and display information more obtrusively.
'If wearable computing is going to be popular you need to provide some information, but not a lot. Our goal was to produce something very light that could be styled like a normal spectacle,' the New Scientist quoted him as saying.
According to him, Informance takes up just 12 per cent of the left eye's field of view, making it barely noticeable when looking straight ahead. Since the brain also compensates for the overlay by emphasising the right eye view, this display is even less obtrusive in practice.
Hazel also revealed that the device could run for 12 hours after a recharge.
Dietmar Uttenweiler, head of research at German lens manufacturer Rodenstock, which also contributed to development of the sunglasses, says that the 160 by 120 pixels display can show even more information.
'Showing directions and distances transmitted by a GPS unit is one possibility we are interested in,' he says.
Rodenstock plans to turn Informance into a commercial product by 2009. According to Uttenweiler, it will cost between 700 to 1000 euros.