Researchers from Northwestern University and the University of Illinois have created the first curvilinear camera, much like the human eye - but with a zoom capability.
The 'eyeball camera' has a 3.5x optical zoom - this can be improved, says the team - takes sharp images, is inexpensive to make and is only the size of a nickel.
It could be used for night-vision surveillance, robotic vision, endoscopic imaging and consumer electronics.
"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. "Our goal was to develop something simple that can zoom and capture good images, and we've achieved that."
The tiny camera combines the simple lens of the human eye, allowing the device to be small, with the zoom capability of an SLR camera. Both the simple lens and photodetectors are on flexible substrates, and a hydraulic system can change the shape of the substrates appropriately, enabling a variable zoom.
Earlier eyeball camera designs were incompatible with variable zoom because they had rigid detectors - the detector must change shape as the in-focus image changes shape with magnification. Huang and his team use an array of interconnected, flexible silicon photodetectors on a thin, elastic membrane, which can easily change shape.
The camera system also has an integrated lens constructed by putting a thin, elastic membrane on a water chamber, with a clear glass window underneath.
Initially both detector and lens are flat. Beneath both the membranes of the detector and the simple lens are chambers filled with water. By extracting water from the detector's chamber, the detector surface becomes a concave hemisphere; injecting water back returns the detector to a flat surface. Injecting water into the chamber of the lens makes the thin membrane become a convex hemisphere.
To achieve an in-focus and magnified image, the researchers actuate the hydraulics to change the curvatures of the lens and detector in a coordinated manner.