It works on the principle of complementary colour, says the article, in which white light is created from a mix of red and green. The projecter turns all coloured images that are reflected onto the wall into white ones by constantly shining complementary colours over them - if a person then stands in front of another project to block its light, the images that were changed to white will be restored to colour.
The researchers at the University of Tokyo are hoping to make the technology commercial, for use in advertising and marking street names, by the end of March 2006. µ
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