The underwater landscape is not as dull and featureless as it may seem when viewed through the lens of a camera inspired by animals that live in the sea. A new bio-inspired camera shows polarization patterns underwater, and this feature could have potential application in underwater navigation.
Mantis Shrimp-Inspired Camera
The camera is a variation of a polarization imager called Mantis cam, which was named after the mantis shrimp that inspired its design. The device takes advantage of the refraction of light when it passes through the surface of water and bounces from water molecules.
The mantis shrimp has 16 color receptors. Humans only have three. This marine animal, however, is not as good when it comes to distinguishing the difference between colors. What it has is the ability to detect another property of light that is invisible to humans, polarization.
Mantis shrimp can see up to six types of polarization, and they are the only known creature that can see circularly polarized light. Researchers said this is comparable to wearing six different polarized sunglasses.
Inspired by the mantis eyes, Viktor Gruev, an engineer at the University of Illinois Urbana-Champaign, and colleagues designed a video camera with miniaturized polarized lenses.
Potential Applications In Underwater Navigation
Gruev's team used the device to collect underwater polarization data from all over the world and noticed that the polarization patterns of the water constantly change.
The researchers eventually learned that these patterns are caused by the position of the sun relative to the location where the recordings were taken. By looking at the polarization pattern in water and the exact time and date the reading was taken, the researchers realized they can can estimate their location in the world.
"We found that we can locate our position on the planet within an accuracy of 61 km," Gruev said.
The findings, which were published in the journal Scientific Advances on April 4, show that the technology has potential applications in underwater navigation.
People and robots could better navigate underwater using visual cues from polarized light. The technology can also be used to find aircraft that were lost at sea and create detailed map of the seafloor.
"The rich repertoire of underwater polarization patterns — a consequence of light's air-to-water transmission and in-water scattering — can be exploited both as a compass and for geolocalization purposes," the researchers wrote in their study.
"We demonstrate that, by using a bioinspired polarization-sensitive imager, we can determine the geolocation of an observer based on radial underwater polarization patterns."