Japanese scientists say they have built an electronic eye that could help blind people get around safely.
It detects where safe crossings are
People wearing the device, mounted to glasses, would be able to cross the road unaided, according to research in the Institute of Physics' MST journal.
It consists of a smart camera-computer combo which detects and measures things such as the colour of traffic lights and the width of the road.
A voice speech system relays the information to the wearer.
Lead scientist Tadayoshi Shioyama, of the Kyoto Institute of Technology said: "The camera would be mounted at eye level, and be connected to a tiny computer.
"It would relay information using a voice speech system and give vocal commands and information through a small speaker placed near the ear."
The device is advanced enough to not only detect the existence and location of a pedestrian crossing, but at the same time also measure the width of the road to the nearest step and detect when traffic lights change from red to green.
The length of a 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 the researchers showed that the crossing length could be measured to within an error of only 5% of the full length, which is less than one step.
To detect the location of crossings in the first place, the device works out a calculation projective invariant.
This takes the distance between the white lines and a set of linear points on the edges of the white lines to tell whether there is a crossing in any given image.
In tests, this method was accurate in all but two of 196 images.
In the two images where the system made a mistake, it said there was not a crossing where there really was one.
Katherine Phipps, from the Royal National Institute of the Blind, said: "Mobility is a serious issue for blind and partially sighted people and new tools like this that may help people with sight problems get around safely are always welcome."