Combining the best features of a lobster and an African fish, University of Wisconsin\u2013Madison engineers have created an artificial eye that can see in the dark. And their fishy false eyes could help search-and-rescue robots or surgical scopes make dim surroundings seem bright as day.<\/p>\n
Their biologically inspired approach, published today in the Proceedings of the National Academy of Sciences<\/a>, stands apart from other methods in its ability to improve the sensitivity of the imaging system through the lenses rather than the sensor component.<\/p>\n Amateur photographers attempting to capture the moon with their cellphone cameras are familiar with the limitations of low-light imaging. The long exposure time required for nighttime shots causes minor shakes to produce extremely blurry images. Yet, fuzzy photos aren\u2019t merely an annoyance. Bomb-diffusing robots, laparoscopic surgeons and planet-seeking telescopes all need to resolve fine details through almost utter darkness.<\/p>\n \u201cThese days, we rely more and more on visual information. Any technology that can improve or enhance image-taking has great potential,\u201d says Hongrui Jiang<\/a>, professor of electrical and computer and biomedical engineering at UW\u2013Madison and the corresponding author on the study.<\/p>\n Most attempts to improve night vision tweak the \u201cretinas\u201d of artificial eyes \u2014 such as changing the materials or electronics of a digital camera\u2019s sensor \u2014 so they respond more strongly to incoming packets of light.<\/p>\n However, rather than interfering with efforts to boost sensitivity at the back end, Jiang\u2019s group 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.<\/p>\n Elephantnosed fishes resemble river-dwelling Cyrano de Bergeracs. Looking between their prominent proboscises reveals 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.<\/p>\n \u201cWe were thinking: \u2018Why don\u2019t we apply this idea? Can we enhance the intensity to concentrate the light?\u2019\u201d says Jiang, whose research is supported by the National Institutes of Health<\/a> and UW\u2013Madison.<\/p>\n The group emulated the fish\u2019s crystal cups by engineering thousands of miniscule parabolic mirrors, each as tall as a grain of pollen. Jiang\u2019s team 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.<\/p>\n \u201cWe showed fourfold improvement in sensitivity,\u201d says Jiang. \u201cThat makes the difference between a totally dark image you can\u2019t see and an actually meaningful image.\u201d<\/p>\n In this case, the devices picked up a picture of UW\u2013Madison\u2019s Bucky Badger mascot through what seemed like pitch-black darkness. The device could easily be incorporated into existing systems to visualize a variety of vistas under low light.<\/p>\n \u201cIt\u2019s independent of the imaging technology,\u201d says Jiang. \u201cWe\u2019re not trying to compromise among different factors. Any type of imager can use this.\u201d<\/p>\n![\"The](\"http:\/\/news.wisc.edu\/content\/uploads\/2016\/03\/Fish-lenses-2-431x500.jpeg\")
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