When walls have eyes

 作者:訾捋贻     |      日期:2019-03-08 10:15:10
By Matt Walker INVISIBLE bar codes could help people who are blind find their way around unfamiliar buildings or towns, say Japanese researchers. Placed in strategic positions at schools, workplaces, railway stations and bus stops, such codes would provide vital information about a locality. Schemes to help blind people using standard bar codes read by a scanner have already been tested in supermarkets. But visible bar codes plastered around public areas would look untidy. So a team led by Hideo Makino, an engineer at Niigata University in Japan, has come up with an invisible bar code that looks like a black square no larger than a postage stamp. The bar code uses two pigments which have different optical characteristics in the infrared range. White lines are duplicated using R-chromofine black, an infrared permeable pigment that allows infrared light to pass through and be reflected by underlying white card. Black lines are written with an infrared absorbing pigment. The bar codes can be read by a small video camera fitted with a visible-light filter. In his experiments, Makino has hooked up such a camera to a computer and voice synthesiser, allowing the information contained in a bar code to be read out to a visually impaired person as they move around an area. Initial results show that information can be read from distances of up to a metre and at walking speeds of 0.8 metres per second. Such devices could be read quickly and contain far more information than Braille directions, but go completely unnoticed by the sighted, says Makino. He is now trying to develop invisible bar codes using colours other than black, so the bar codes could be hidden in a picture or on a wall of the same colour. John Gill, chief scientist for Britain’s Royal National Institute for the Blind,