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Thursday, 16 December 2010
Tube stations are plastered with advertising - it helps defray the cost of running the trains, and without it Oysters would need even more money put on them than they do now.
But in the tunnels the windows go black. This is despite the fact that the passing train is throwing light out onto them. Why not put ads there too?
The reason is that they would rush past in a blur. Old-fashioned film would do the same if you just moved it through the gate of its projector. Each frame had to stop at the gate, and a shutter had to open and close to freeze the frame for a moment on the screen. Then there was a short time gap before the next frame. You didn't see this gap because of your eyes' persistence of vision.
By making tube windows from liquid crystals just like the ones used for 3D movie glasses it should be possible to achieve the same effect. As the train went past a set of identical pictures pasted to the tunnel wall the window liquid-crystal shutter would open and close for each one, maybe with an outward-pointing electronic flash to illuminate it extra brightly. The opening and the flash could be triggered by a mark on the tunnel wall beside each picture to keep the whole thing in synchronization whatever the speed the train was moving at.
Identical pictures would give a still image. But of course you could make moving pictures too.
Perhaps there should be ads all down one wall, and an idyllic sunlit country landscape with the trees moving gently in the breeze down the other...