A new system developed by Tadayoshi Shioyama and Mohammad Uddin from the Kyoto Institute of Technology in Japan will allow blind people to cross busy roads in total safety for the first time.
The system itself comprises a single camera mounted on a pair of glasses that is hooked up to a small computer. Not only is the system capable of detecting the existence and location of a pedestrian crossing, it can measure the width of the road to the nearest step and detect the colour of the traffic lights. It relays vocal commands and information to the user through a small speaker placed near the ear.
The system developed at Kyoto is the final product of a research programme that aimed to give blind people all the navigation information they needed to cross a road from a single small camera.
The length of the pedestrian crossing is measured by projective geometry: the camera makes an image of the white lines painted on the road, and then the actual distances are determined using the properties of geometric shapes as seen in the image. Experiments carried out by Shioyama and his colleagues showed that the crossing length could be measured to within an error of only 5 per cent of the full length – which is less than one step.
To detect the location of crossings, the researchers used a calculation called the ‘projective invariant’ which takes the distance between the white lines (called the band width) and a set of linear points on the edges of the white lines, to give an accurate way of detecting what is or isn’t a crossing in a given image.
They used this technique to analyse 196 images and it proved successful in detecting whether there was a crossing present in 194 of them. In the two images where the system made a mistake, it said there wasn’t a crossing where there really was one.
The research appears today in the journal Measurement Science and Technology published by the Institute of Physics.