The lens that could help camera phone photographers compete with the professionals

Scientists have developed a super-thin lens that can function either as a convex or a concave lens with the flick of a switch. It means a scene can either be magnified or viewed at wide angle.

It could provide a new generation of small lenses used in devices such as mobile phones and tablet computers, allowing keen photographers to capture images that previously required expensive SLR lenses.

Dr Shuang Zhang, a reader in metamaterials at the University of Birmingham who led the research team, said: "This new device will give greater flexibility in designing and adding new functionalities to optical systems.

"The focusing properties of the same lens can be altered between a convex lens and a concave lens at will. Furthermore, the compact size, and the flat nature of the lens could useful."

The scientists created the lens, known as a plasmonic metalens, by layering gold nano-rods onto a thin, flat shard of glass half the width of a human hair.

Conventional lenses use curved glass surfaces to alter the direction of the light as it enters a camera to either magnify an object or make it smaller.

The layer of gold rods on top of the new lens, however, allows this effect to be achieved on a flat surface by controling the direction the light travels as it passes through the glass.

A prototype of the lens created by the researchers has an aperture of 80 micrometers - roughly the width of a human hair - and a focal length of 60 micrometers.

Changing the lens from its wide angle mode to the zoom mode is achieved by switching the polarisation of the light as it hits the lens. This can be achieved by placing a filter in front of the lens.

Their findings are published in the journal of Nature Communications.

Dr Zhang said they now hoped to make larger lenses that could be used in electronic devices such a mobile phones.