Pico projectors have been popping up in a number of phones recently, either as integrated devices or as an add-on in the shape of an iPhone case, for example.

But one group of researchers has gone a step further and developed a concept that sees the projector integrated into the phone and given a new function. It allows users to project an image of their phone screen and their caller's screen onto a surface in front of them while they take the call.

The two people on the call can then drag things between the two projected screens to share or work on together, alleviating the problem of touchscreen phones that tend to lockdown during a call.

The screen is about twice the size of a tablet screen and the technology in the phone tracks the users movements to allow them to manipulate the image with their fingers.

At the moment, the prototype is too bulky for commercial deployment. But the researchers from the University of Duisberg-Essen are working to make it a practical option.

In the future, there could well be patents filed by major firms such as Apple looking to integrate a scaled down version of the technology into their handsets.