Researchers at Northwestern University (Evanston, IL) and the University of Illinois at Urbana-Champaign (Illinois) have a vision of what they believe is the ideal camera technology: They have married the hemispherical shape and lens simplicity of the human eye with the zoom capability of a single-lens reflex (SLR) camera. The resulting 'eyeball camera' could someday be employed to enhance endoscopic imaging, according to the researchers.

"Current camera [technology] is great, but its focal detector systems are really flat," says Yonggang Huang, a professor of civil and environmental engineering and mechanical engineering at Northwestern. "When you take pictures with a simple lens, the middle part is very clear, but when you go to the sides, the quality really decays. That is why we currently need a complex lens system in a camera to reduce this decay."

In contrast, the human eye features a curved detector surface so that image clarity is maintained throughout the field of vision. Aiming to replicate this curvilinear structure in a camera, Huang and John Rogers, the Lee J. Flory-founder chair in engineering at Illinois, developed a transfer printing technique that enables the printing of electronics on a flexible substrate.

"The current electronic technologies are really for rigid wafers and flat processing," Huang notes. "However, to integrate electronics with the human body, you really need the electronics to be curvilinear and flexible."

Building on this initial flexible electronics technology, which they achieved in 2008, the researchers have now created what they claim is the first tunable curvilinear camera with zoom capability. Roughly the size of a nickel, the compact eyeball camera features a simple lens system also modeled after the human eye. "Current cameras are expensive and bulky because they have a very complex lens system," Huang states. "The new camera has the potential to have a very simple lens system, so it could be less bulky and cheap to manufacture."

While the camera benefits from replicating the human eye in terms of shape and lens simplicity, it is enhanced by zoom technology borrowed from conventional cameras.

Adjustable zoom is made possible through the use of an array of interconnected and flexible silicon photodetectors placed on a thin, elastic membrane. This design allows the detectors to change shape in conjunction with the shifting shape of the image caused by magnification. To obtain a clear, magnified image, the scientists actuate a hydraulics system that coordinates the alteration of the curvature of the lens and detectors.

Equipped with a 3.5x optical zoom, the eyeball camera shows potential for use in future endoscopic imaging applications, Huang says. He adds that although the image quality is currently good, the researchers are working on improving resolution as the next phase of the project.