Camera Design Mimics Sophisticated Visual System

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The bio-inspired design of an ultrasensitive camera that is capable of sensing both color and polarization is based on the visual system of the mantis shrimp. The camera features a single-chip, low-power, high-resolution color-polarization imaging system. The imager captures co-registered color and polarization information in real time with high resolution by monolithically integrating nanowire polarization filters with vertically stacked photodetectors. The photodetectors capture three different spectral channels per pixel by exploiting wavelength-dependent depth absorption of photons.

Professor Viktor Gruev (l) and Missael Garcia (r), camera based on visual system of mantis shrimp. University of Illinois.

Illinois electrical and computer engineering professor Viktor Gruev, right, and graduate student Missael Garcia have developed a camera capable of sensing both color and polarization by mimicking the eye of the mantis shrimp. The camera could improve early cancer detection and provide new understanding of underwater phenomena. Courtesy of L. Brian Stauffer.

The imager comprises 1280 x 720 pixels with a dynamic range of 62 dB and a maximum signal-to-noise ratio of 48 dB. According to researchers, the quantum efficiency is more than 30 percent over the entire visible spectrum and the camera achieves high polarization extinction ratios on each spectral channel.

Researchers at the University of Illinois at Urbana-Champaign replicated the shrimp’s visual system using basic physical concepts.

“Nature has constructed the mantis shrimp eye in such a way that photosensitive elements are vertically stacked on top of each other,” said professor Viktor 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.”

This stacking allows for absorption of shorter wavelengths, such as blue light, in the shallow photoreceptors and red light in the deeper receptors. The team’s imaging sensor utilizes pixelated linear polarization filters deposited on an array of silicon-based vertically stacked photodetectors. Similar to its biological counterpart, silicon’s absorption coefficient is wavelength dependent and monotonically decreases from the blue to red wavelengths.

“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,” said researcher Missael Garcia. “By stacking multiple photodiodes on top of each other in silicon, we can see color without the use of special filters. And 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.”

The compact, highly sensitive point-and-shoot imaging system is capable of capturing co-registered color and polarization information in real time. Because of its size, low power and ease of use, the camera could be used for a number of applications, such as underwater imaging, remote sensing, and various biomedical applications, where polarization yields a body of information orthogonal to that of the color channels.

“By mimicking the mantis shrimp visual system, we have created a unique camera that can be used to improve the quality of our lives,” Gruev said. “The notion that we can detect early formation of cancer is what is driving this research forward. The cost of this technology is less than $100, which will enable quality health care in resource-limited places around the world.”

The mantis shrimp, considered one of the best hunters in shallow waters, possesses one of the most sophisticated eyes in nature. Compared with human vision, which has three different types of color receptors, the mantis shrimp has 16 different types of color receptors and six polarization channels, Gruev said.

The research was published in Optica, a publication of OSA, the Optical Society (doi: 10.1364/OPTICA.4.001263). 

Illinois researchers have developed an ultra-sensitive camera capable of sensing both color and polarization by mimicking the eye of the mantis shrimp. A new study finds that the bio-inspired imager may provide new understanding of underwater phenomena. Courtesy of University of Illinois at Urbana-Champaign.

Published: October 2017
A device used to sense incident radiation.
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