Researchers have used the human eye as inspiration for a new type of camera that boasts the simple lens system of the eye, but features the variable zoom capability of a single-lens reflex (SLR) camera without the bulk and weight of a complex lens system. As a result, the “eyeball camera” measures less than an inch in diameter, is inexpensive to make and should be suited to a variety of applications, including night-vision surveillance, robotic vision systems, endoscopic imaging and consumer electronics.
Developed by researchers from Northwestern University and the University of Illinois at Urbana-Champaign, the first of its kind curvilinear camera overcomes the problem of previous eyeball camera designs that were incompatible with variable zoom. This was because they used rigid detectors, but because the image changes shape with magnification, the detector must also change shape to keep the image in focus.
To achieve this the researchers used an array of interconnected and flexible silicon photodetectors on a thin, elastic membrane, which can easily change shape. Additionally, the camera system also has an integrated “liquid lens” constructed by putting a thin, elastic membrane on a water chamber, with a clear glass window underneath.
Initially the chambers beneath the membranes of the detector and the lens are filled with water, making both the detector and the lens flat. But as water is extracted from the detector’s chamber, the detector surface becomes a concave hemisphere. Meanwhile, injecting water into the lens chamber makes the thin membrane become a convex hemisphere.
By controlling the hydraulics to change the curvatures of the lens and detector in a coordinated way to ensure the shape of the detector matches the varying curvature of the image surface, the camera is able to produce an in-focus and magnified image. The camera developed by the researchers currently has a 3.5x optical zoom, but they say a higher zoom is possible using the technology.
“We were inspired by the human eye, but we wanted to go beyond the human eye,” said Yonggang Huang, Joseph Cummings Professor of Civil and Environmental Engineering and Mechanical Engineering at Northwestern’s McCormick School of Engineering and Applied Science. “Our goal was to develop something simple that can zoom and capture good images, and we’ve achieved that.”
The research carried out by the researchers from Northwestern University and the University of Illinois at Urbana-Champaign will be published in the Proceedings of the National Academy of Sciences (PNAS).