CONTROLLING the cursor on a computer screen without needing to use a
mouse or keyboard control keys would leave a user鈥檚 hands free to carry
out other operations. Wang Laboratories of Lowell, Massachusetts, has come
up with a device for hands-free control which would also make it easier
for handicapped people to operate a computer. Wang鈥檚 patent application
(WO 90/05356) describes a band which clips over the top of the user鈥檚 head,
like a pair of personal stereo headphones. The band supports a spherical
container, like a table-tennis ball, which is half filled with liquid.
When the user鈥檚 head is upright, the boundary between liquid and air
is horizontal. When the user鈥檚 head tilts, the boundary changes its angle
with respect to the sphere.
Inside the top of the sphere are four light-emitting diodes which emit
beams of light down through the boundary to four photodetector diodes in
the bottom half of the sphere.
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As the boundary angle changes when the user鈥檚 head moves, the beams
of light become more or less refracted, or bent, by the surface of the liquid
so varying amounts of light get through to the detectors.
Comparison of the electrical outputs from the four sensors gives an
accurate indication of the direction of rotation of the sphere and hence
the position of the computer user鈥檚 head.
It is a simple step to convert the output signals from the orientation
sensors into digital code, which is formatted to simulate cursor control
signals. In this way the user can aim a cursor at any part of the screen.