Japanese scientists have devised a way of using focused, high power lasers produce a 3d image in thin air. Each laser produces a single spot of light where it is focused if the right intensity is used; the spots only last for a milisecond, but by refreshing the dot rapidly, much like in a television set, the image appears constant. They are currently working on increasing the refresh rate to give a clearer image, and plan to eventually produce moving pictures. The only limit to this method is that it cannot produce colour, only white light.
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I'm actually quite excited by this idea. I'd love to see this in real life, and in bigger and better forms. I'd be confident in predicting good quality moving images (perhaps as good as black-and-white tv) being possible within ten years, and I can't see the ad companies not taking the opportunities this presents. Yes, very bright ads floating in the air might not seem an entirely good thing, but I'd find the whole thing impressive enough I don't think I'd care.
