Liquid lens mimics human eye
Fluid device could find its way
into pocket-sized gadgets.
19 March 2004
MICHAEL
HOPKIN
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| The tiny lenses
are just 2 by 3 millimetres in size. |
| © Philips |
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Researchers have unveiled a fluid lens that can alter
its focusing power at the flick of an electric switch.
The device could find use in hand-held computers and
camera telephones, its inventors say.
The FluidFocus lens, as it is called, could speed the
development of ever-tinier gadgets, says Koen Joosse,
an engineer at Philips Research in Endhoven, the Netherlands.
"There is always demand for smaller and smaller lenses,"
he says.
It will be a year or two before the lens can be manufactured
in wholesale numbers, Joosse adds. Its cost is still
uncertain - that will depend on the application and
the overall numbers produced, he says. Philips Research
unveiled the device at this week's CeBIT technology
trade fair in Hanover, Germany.
The lens is made up of a water-based solution and an
oil. The two are contained in a cylinder 3 millimetres
across and 2.2 millimetres high.
A water-repellent chemical coats the tube's walls and
one of its caps. This pushes the watery droplet away
from the cylinder's sides and forces it into a hemisphere.
As the two liquids have different optical properties,
the curved boundary between them bends light like a
lens.
Field work
The focal distance of the lens can be changed simply
by applying an electric field. This makes the tube's
coating less hydrophobic, relaxing the water droplet's
tendency to shy away from the walls and allowing it
to sag and spread.
As the liquid curve bends towards the bottom of the
tube, it focuses light closer to the device. At its
most convex, the FluidFocus lens can focus on an object
5 centimetres away. As the electric field drops, the
lens flips from close-up to distant focusing in just
10 milliseconds.
The lenses in our eyes also change shape to focus on
different distances. But our eyes use muscles attached
to the lens to do this, rather than an electric field.
Philips Research has already built an electronic display
using technology similar to that in the FluidFocus lens1.
The pixels of the display use two liquids of different
colours; the overall colour of each pixel changes as
the liquids shift shape.
Joosse thinks the lens is suitable for mass production,
and could soon show up in miniature cameras. Such tiny
lenses might also be useful in medical tools such as
endoscopes, he says.
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