Seeing in the Dark with Artificial Eyes

Fish eyes inspire lens for improved night vision.

Elephant-nosed fish. (Image courtesy of ThinkFish.)

Elephant-nosed fish. (Image courtesy of ThinkFish.)

To improve night vision in search-and-rescue robots, engineers have fabricated an artificial eye with night vision capabilities. The inspiration came from the biology of lobsters and elephant-nosed fish.

Previous attempts to improve night vision have focused on sensory components for improving images, but by focusing on lenses the engineers saw significant night vision improvement. 

Bypassing the Sensory Approach

The team from the University of Wisconsin-Madison led by Hongrui Jiang, professor of electrical and computer engineering and of biomedical engineering at the University of Washington-Madison, increased light intensity through optics that focus the light on the sensor.  

Most night vision improvement studies make “retinal” adjustments on artificial eyes, such as changing the materials or electronics of a digital camera’s sensor. This allows a lens’ response to incoming light to be more sensitive. However, Jiang’s team studied lobster eyes for their ability to concentrate incoming light to individual spots and elephant-nosed fish eyes for their uncommon retinas, which are made of crystal cups.

Eye schematic. (Image courtesy of the American Academy of Ophthamology.)

Eye schematic. (Image courtesy of American Academy of Ophthamology.)

For the fish, the miniature crystals collect and intensify red light to help identify oncoming predators. By combining the crystal structure with the lobster’s superposition compound eyes, Jiang’s team created the uniform hemispherical dome. As a result, the device picked up a picture of university’s Bucky Badger mascot through what seemed like pitch-black darkness. This could be applied to any type of imager.

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

Clarity Compromised

The bio-inspired eyes have reached a new level in light sensitivity; however, vision sharpness suffers. This is because as more light is compressed to individual pixels, clarity decreases. To alleviate this flaw in design, Jiang’s team captured raw images and processed the set using an algorithm they developed for clearer pictures. Once precision is perfected, Jiang predicts that the artificial eyes could improve by at least an order of magnitude.

“It has always been very hard to make artificial superposition compound eyes because the curvature and alignment need to be absolutely perfect,” said Jiang. “Even the slightest misalignment can throw off the entire system.”

For photography, capturing nighttime images requires a steady hand for long exposure time. Aside from blurry images, the artificial fish eye could remove limitations for bomb-diffusing robots, laparoscopic surgery and telescopes.

“These days, we rely more and more on visual information,” said Jiang. “Any technology that can improve or enhance the taking of an image has great potential.”

For more on the cutting edge of imaging technology, learn how staring deep into a rocket’s plume gave NASA a new vision.