The camera is making strides in science by allowing humans to glimpse into a hidden world and can even potentially improve early cancer detection

By Warren Miller,
contributing writer

Where does science look for inspiration to improve optical
imaging technology? Apparently, the seafood platter. An Illinois research team
has developed a camera based on the eye
of the mantis shrimp that is capable of detecting both the color and
polarization of light. This provides
visibility into a world unseen by human eyes, with implications as wide-ranging
as improved underwater research and early cancer detection.

While the human eye contains just three different types of
color receptors, the mantis shrimp’s eye has 16 different such receptors, as
well as six polarization channels, making it one of the most sophisticated
ocular devices naturally occurring in nature. Polarization, in particular, is
particularly useful to perceive. Most humans only know polarization from
glare-reducing sunglasses, but animals use polarization to help find food,
navigate by sensing polarization of the sky, or even as a covert communications
channel.

The research behind the camera was recently published as
“Bio-inspired color-polarization imager for real-time in situ imaging” in Optica, a journal of the OSA. Victor
Gruev, a professor of electrical and computer engineering at the University of
Illinois and a co-author of the study, helped develop the new camera with
graduate student Missael Garcia.

“Nature has constructed the mantis shrimp eye in such a way
that photosensitive elements are vertically stacked on top of each other,” said Gruev. “These organs not only surpass the sensitivity of
our own visual systems, they also capture more visual information, using less
power and space, than today’s most sophisticated, state-of-the-art cameras.” 

According to Garcia, the same laws of physics that apply to the mantis
visual system also apply to silicon materials, the material used to build our
digital cameras. By stacking multiple photodiodes on top of each other in
silicon, they can see different colors without the use of special filters. This
occurs because the sensors absorb light differently for different wavelengths.
Red penetrates deeper into the stack, for instance, meaning that lower sensors
will respond only to the red light while upper sensors are sensing the blue
energy. And by arranging the sensors in a periodic fashion, polarization
becomes detectable. “By combining this technology with metallic nanowires, we
effectively have replicated the portion of the mantis shrimp visual system that
allows it to sense both color and polarization,” he said.

Gruev_and_Garcia

Illinois electrical and computer engineering professor
Viktor Gruev, right, and graduate student Missael Garcia. Image source:
illinois.edu.

The polarization of light is the direction of oscillation of
light as it’s distributed through space. According to the duo, the human eye
isn’t nearly sensitive enough to detect polarization, and neither are the most
advanced digital cameras built to date. Undersea animals use polarization for
both communication and navigation due to its higher efficiency underwater, where illumination levels are lower. Being underwater, often very far underwater,
reduces background light noise, which is much more familiar to use above-water
dwellers. Polarized light seems to be a much better communication choice underwater, not unlike the way that whales use specific sound frequencies that can travel
much further underwater than in air.

The implications of this new technology in the area of
underwater research are numerous. Much of marine life exploits both color and
polarization in their vision systems. The ability to mimic their perception
will help biologists learn how these creatures navigate, hunt, and even
communicate using polarization effects.

But the researchers believe that their camera has uses closer to
home as well. Earlier research has shown that polarization can be used to
detect cancer in its early stages. Polarization sensors fitted to a colonoscope
were able to detect the disordered nature of cancer cells in the human colon,
for example. “The notion that we can detect early formation of cancer is what
is driving this research forward,” said Gruev. “The cost of this technology is
less than $100, which will enable quality health care in resource-limited
places around the world.”