Optical physics is a very mature science; therefore, you wouldn’t expect major breakthroughs. Circa 1900, the federal government seriously considered closing the
patent office believing that everything that could be
invented already had been. Never underestimate man’s
Optics has recently quietly realized several discoveries
that could radically reshape it. These and their spinoffs aid
sciences such as IC manufacturing. This article addresses
competing related optics technologies, and how electronics
assists them. “Adaptive lenses” were formerly laboratory
curiosities. They are now commercially viable products with
greater than five megapixel lenses within upscale cell
phones. These lenses have superior resolving and focusing
power, have no moving parts, and consume minuscule
Types of Liquid Lenses
A liquid lens uses one or more fluids to control the
meniscus (the surface of the liquid.) There are two types:
transmissive and reflective. Don’t confuse these with liquid-formed lenses that you create from plastic, or epoxy drops
on a surface that harden to form a lens shape.
Reflective Liquid Lenses are just variable mirrors.
Reflector telescopes use them in place of traditional glass
mirrors. When you rotate a container of fluid (in this case,
mercury), centripetal force creates a smooth reflective
concavity. This avoids meticulously grinding and polishing
glass. The latter is extremely expensive and tricky
(remember the Hubble Space Telescope mirror fiasco?) .
A simple change in rotation speed changes the curve
of the meniscus of a reflective lens to the proper shape.
Scientists at the University of British Columbia built a 236
inch (six meter) liquid mirror telescope. As the world’s 13th
largest telescope, its reflective surface is a flat container of
mercury spinning at about 5 RPM. The telescope only costs
$1 million — much less than the $100 million a conventional
telescope with a solid glass mirror of the same size costs.
Transmissive Liquid Lenses (the main subject of this
article) use two immiscible fluids (ones that will not mix
together to form a single homogeneous substance) — each
with a different refractive index. This creates variable-focus
lenses of high optical quality as small as 10 µm (microns).
One of the two fluids is an electrically conducting
aqueous solution and the other a non-conducting oil. They
are contained in a short tube with transparent end caps.
You coat the interior of the tube and one of the caps with
a hydrophobic (not easily mixing with water) material. This
The latest generation of adaptive lenses has
revolutionized still and video photography,
from applications ranging from smartphones
to personal drones. Read on to learn how
they work and what's on the horizon.
34 SERVO 02.2015
Adaptive Lenses — Electronic Wonders
By Vaughn D. Martin
and Tony Rivera P.E.