Vibrating touch screen puts Braille at the fingertips

OUCH-SCREEN devices like the iPhone are great when you can see them, but not much good if you are blind. Now a new way of presenting Braille characters on a mobile device could be the first step towards a Braille-ready touch-screen phone.

In Braille, letters are encoded using a two-by-three matrix in which each character is represented by a different configuration of raised and absent dots at the six locations. To display these dots on a touch-screen device, Jussi Rantala of the University of Tampere in Finland and colleagues used a Nokia 770 Internet Tablet, which has a piezoelectric material built into the touch screen that vibrates when an electric signal is applied to it. The team installed software that represents a raised dot as a single pulse of intense vibration, and an absent dot as a longer vibration made up of several weaker pulses (see diagram).

To discover how visually impaired volunteers would prefer to receive these vibrations, the team developed two different presentation methods. In the first, the user touches the screen on the left-hand side to read whether or not there is a bump in that position of the matrix, then moves their finger horizontally across the screen to read the remaining five dots. "But it wasn't that easy to read," says Rantala.

In the second method, the user simply places a finger anywhere on the screen and holds it still. The phone then displays a character by vibrating the sequence of six dots, each 360 milliseconds apart. "It took some time for them to start reading, because this representation is totally different from anything else that they had previously used," says Rantala. But once the volunteers were used to it, they were able to speed it up and read a character in as little as 1.25 seconds