Analysts worried about visual pollution from mini projectors

The projector, developed by the company 3M, is around 4cm by 3cm and designed to be embedded in PDAs, media players and cameras as well as mobile phones.

Martin Raymond, founder and director of the Future Laboratory, told BBC World Service's Digital Planet programme that in theory, they will allow content to be displayed virtually anywhere - such as onto the back seat of a bus, or on a train, or a wall.

But he warned that, while the idea is "appealing initially," he had concerns about "intruding into personal spaces, visual pollution, and inappropriate showing of things that maybe other people shouldn't be seeing."

"So actually, in the guise of something that seems quite sensible, we're going to see a lot more laws and legislation to prevent us from airing our films in public," he added.