One day your optician could give you superhuman eyesight
THINK you've got perfect vision? Think again. Pablo Artal reckons he can
double the sharpness of anybody's vision, no matter how good it is to
start with. He revealed his "smart spectacles" technology at a conference
on adaptive optics in Murcia, Spain, last week.
Few people would choose to wear Artal's prototype, as the computer
hardware it relies on takes up a full square metre of desk space. "But
the key optical component is very small and cheap," says Artal, a
researcher in the optics laboratory at the University of Murcia.
Conventional spectacles correct for poor focusing and astigmatism in the
eye's lens. But almost everyone has subtle additional faults which vary
as their pupils dilate and their eyes focus. To try and correct for these
problems, Artal and his colleagues turned to the techniques of adaptive
optics, which are more commonly used in telescopes and spy satellites.
In adaptive optics, light from a star, say, is bounced off a mirror which
changes shape to compensate for the distortions introduced by
fluctuations in the atmosphere. It is these fluctuations in the density of
the atmosphere that make stars twinkle. Artal's spectacles do the same
thing for transient imperfections in the eye, correcting for them 25 times
every second. "Everything sharpens up as you switch on," he says.
In his prototype spectacles, a low-intensity infrared laser beam bounces
off the back of the retina and into a sensor via a deformable mirrored
membrane. The membrane's shape is controlled by an electric field
created by a microchip underneath it.
A computer works
out how much the
infrared beam has
been distorted by
the eye's lens and
tells the mirror chip
to deform the mirror
in real time (see
Diagram). Because
light reaches the
user's eyes via the
deformable mirror,
the computer can
ensure that the user
sees a perfect
image.
The mirror's shape
is updated 25 times
per second--about 5
times faster than
aberrations vary in
the eye, so the
wearer is unaware
of the moving
mirror.
Artal says that
someone wearing
the new specs can
see at a range of 12
metres objects so
small that someone
with 20:20 vision can't see them farther away than 6 metres. But Fred
Fitzke, an ophthalmologist at University College London, is more
cautious: "At the moment, we don't know what other limits there are to
vision--like the structure of photoreceptors in the eye, or whether the
brain can even use the extra information. But I look forward to finding
out with this kind of device."
As well as having possible military applications, the super specs can be
used in reverse to take real-time precision images of the retina. "You
can use it to take microscopic images of individual cells and diagnose
eye diseases very early," says Austin Roorda of the University of
Houston.
Eugenie Samuel
From New Scientist magazine, 25 November 2000.
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