New fish-inspired lens to see in the dark

Washington: Scientists have combined the best features of a lobster and a fish to create an artificial eye that can see in the dark and may be used in surgical probes, search-and-rescue robots or planet-seeking telescopes.

Researchers from the University of Wisconsin-Madison in US improved the sensitivity of the imaging system through the lenses rather than the sensor component.

Bomb-diffusing robots, laparoscopic surgeons and planet-seeking telescopes all need to resolve fine details through almost utter darkness. These false eyes could help search-and-rescue robots or surgical scopes make dim surroundings seem bright as day, researchers said.

"These days, we rely more and more on visual information. Any technology that can improve or enhance image-taking has great potential," said Hongrui Jiang, professor at UW-Madison.

Most attempts to improve night vision tweak the "retinas" of artificial eyes—such as changing the materials or electronics of a digital camera's sensor—so they respond more strongly to incoming packets of light.

However, rather than interfering with efforts to boost sensitivity at the back end, researchers set out to increase intensity of incoming light through the front end, the optics that focus the light on the sensor.

They found inspiration for the strategy from two aquatic animals that evolved different strategies to survive and see in murky waters.

Looking between the prominent proboscises of elephant-nosed fishes unveils two strikingly unusual eyes, with retinas composed of thousands of tiny crystal cups

instead of the smooth surfaces common to most animals. These miniature vessels collect and intensify red light, which helps the fish discern its predators.

The group emulated the fish's crystal cups by engineering thousands of miniscule parabolic mirrors, each as tall as a grain of pollen. The researchers then shaped arrays of the light-collecting structures across the surface of a uniform hemispherical dome.

The arrangement, inspired by the superposition compound eyes of lobsters, concentrates incoming light to individual spots, further increasing intensity.

"We showed fourfold improvement in sensitivity. That makes the difference between a totally dark image you can't see and an actually meaningful image," said Jiang.

The device could easily be incorporated into existing systems to visualise a variety of vistas under low light.

Although superposition compound eyes are exquisitely sensitive, they typically suffer from less sharp vision.

Increased intensity costs clarity when lots of light gets compressed down to individual pixels.

To recover lost resolution, researchers captured numerous raw images and processed the set with an algorithm to produce crisp, clear pictures. The study was published in the journal PNAS.